Design of Antennas for Handheld DVB-H ... - Lunds tekniska högskola

Design of Antennas for Handheld
DVB-H Terminals
Master of Science Thesis
Fredrik Persson & Mattias Wideheim
in cooperation with
Perlos AB
January 2006
Department of Electroscience

Abstract
DVB-H is a standard that makes it possible to deliver live broadcast
television to handheld terminals. It is developed from the DVB-T standard,
which makes it possible to send DVB-H signals along with DVB-T signals in
the same multiplexer, in the DVB-H/T frequency band 470-862 MHz. A
benefit with this is that it is possible to reuse the DVB-T transmission
equipment. The differences between DVB-H and DVB-T are some additions
that improve the features for a mobile terminal in the DVB-H standard. The
most important additions are the time slicing, in order to reduce the average
power consumption, and MPE-FEC for improving Doppler performance and
tolerance against interference.
A big challenge in developing terminals for the DVB-H system is the
antenna. The problem is the low frequencies and the small size of today’s
handheld terminals. The result is electrically small antennas that are difficult
to get good efficiency with. The large bandwidth is another big problem
when designing antennas for DVB-H.
After an introduction of the DVB-H system this master thesis investigates
different solutions for both external and internal antennas for the DVB-H
system, such as PIFA, loop antenna, monopole and dipole.
The investigation takes RF performance, size, design, complexity and cost in
consideration when evaluating the proposals for DVB-H antennas.
I

Acknowledgements
This master thesis is our final thesis at the Master of Science programme in
Electrical engineering at Lund institute of technology.
To start with we would like to thank our supervisors Anders Sunesson and
Dag Mårtensson for giving us the chance to work with this interesting thesis
and all support during the work.
We also would like to thank the entire RF engineer team at Perlos who have
supplied us with technical and antenna knowledge and helped us through a
lot of the problems that have turned up during the work. We are also grateful
to all other Perlos employees for the pleasant Wednesday meetings.
Finally we would like to thank our supervisor Anders Karlsson at LTH.
This work has been supported and funded by Perlos AB in Lund.
II

List of contents
1 INTRODUCTION ..........................................................................................1
1.1 Thesis overview.......................................................................................... 1
1.2 Purpose....................................................................................................... 2
2 BACKGROUND............................................................................................3
2.1 Digital Video Broadcasting....................................................................... 3
2.1.1 DVB .................................................................................................... 3
2.1.2 OFDM ................................................................................................. 4
2.1.3 Reed-Solomon Codes.......................................................................... 7
2.1.4 DVB-T................................................................................................. 7
2.1.5 DVB-H ................................................................................................ 9
2.1.5.1 Standardization of DVB-H............................................................ 10
2.1.5.2 Time slicing................................................................................... 11
2.1.5.3 Multi Protocol Encapsulation – Forward Error Correction........... 12
2.1.5.4 MPE-FEC frame............................................................................ 13
2.1.5.5 4K mode ........................................................................................ 14
2.1.5.6 Transmission Parameter Signalling - TPS .................................... 15
2.2 Competing standards .............................................................................. 17
2.2.1 Satellite-Digital Mobile Broadcast.................................................... 17
2.2.2 Mobile Broadcast/Multicast Service ................................................. 17
2.3 Antenna theory ........................................................................................ 19
2.3.1 Efficiency, directivity and gain......................................................... 19
2.3.2 Reflection from a mismatched antenna ............................................. 19
2.3.3 Resonance Circuit ............................................................................. 21
2.3.4 Quality Factor.................................................................................... 22
2.3.5 Bandwidth......................................................................................... 23
2.3.5.1 Impedance matching ..................................................................... 23
2.3.6 Bandwidth enhancement ................................................................... 24
3 POSSIBLE SOLUTIONS..........................................................................26
3.1 Dipole and Monopole antenna ............................................................... 26
3.2 Yagi-Uda .................................................................................................. 26
3.3 Loop.......................................................................................................... 27
3.4 Microstrip antenna.................................................................................. 27
III

4 DESIGN AND TESTING OF ANTENNA SOLUTIONS .......................30
4.1 Required antenna performance ............................................................. 30
4.2 Monopole.......................................................Error! Bookmark not defined.
4.3 Folded dipole antenna ............................................................................. 32
4.4 PIFA.......................................................................................................... 33
4.5 Folded-Patch............................................................................................ 35
4.6 Loop antenna ........................................................................................... 38
4.7 Switched Monopole ................................................................................. 43
5 MEASUREMENTS OF ANTENNA SOLUTION....................................54
5.1 Anechoic chamber measurement ........................................................... 54
5.1.1 Test set-up ......................................................................................... 54
5.1.2 Measurements.................................................................................... 54
5.1.3 Measurement result ........................................................................... 59
5.1.4 Measurement reliability..................................................................... 69
5.2 Testing with DVB-T receiver................................................................. 70
6 RESULTS....................................................................................................72
6.1 RF Performance ...................................................................................... 72
6.2 Design....................................................................................................... 72
6.3 Control signal........................................................................................... 73
6.4 Cost........................................................................................................... 73
7 CONCLUSION............................................................................................74
8 REFERENCES............................................................................................79
IV

List of figures
Figure 2.1. Multi path propagation of the transmitted signal………………….. 6
Figure 2.2. Digital TV standards used in the world……………………………. 8
Figure 2.3. Connection between the specifications defining DVB-H.………….10
Figure 2.4. An example of the data sent trough one multiplexer……………….12
Figure 2.5. The three elements that form the DVB-H codec…………………... 13
Figure 2.6. The MPE-FEC frame……………………………………………….14
Figure 2.7. DVB-H symbol interleaving scheme……………………………….15
Figure 2.8. Voltage reflection from a mismatched load……………………….. 19
Figure 2.9. Impedance bandwidth………………………………………………21
Figure 2.10. Parallel resonance circuit………………………………………….22
Figure 2.11. Matching circuit scheme…………………………………………..24
Figure 3.1. Yagi-Uda antenna………………………………………………...... 27
Figure 3.2. Four different configurations to feed microstrip antennas………….29
Figure 3.3. PIFA antenna………………………………………………………. 29
Figure 4.1. Specified gain for handheld DVB-T terminals……………………..30
Figure 4.2. Dipole antenna……………………………………………………... 32
Figure 4.3. Dipole antenna dimensions………………………………………....32
Figure 4.4. Dipole antenna, return loss graph………………………………….. 33
Figure 4.5. PIFA antenna………………………………………………………. 34
Figure 4.6. PIFA return loss graph…………………………………………….. 34
Figure 4.7. Folded-patch antenna……………………………………………….35
Figure 4.8. Return loss graph for the folded-patch…………………………….. 36
Figure 4.9. Folded-patch 2 antenna……………………………………………..37
Figure 4.10. Return loss graph of the folded-patch 2………………..….………38
Figure 4.11. Loop antenna schematic………………………………………….. 39
Figure 4.12. Perlos loop antenna………………...……………………………...39
Figure 4.13. Perlos loop antenna return loss graph……………………………..40
Figure 4.14. Wire loop antenna…………………………………………………40
Figure 4.15. Wire loop antenna return loss graph………………………………41
Figure 4.16. Loop antenna…………………………………………………….. 42
Figure 4.17. Loop antenna return loss graph………………………………….. 42
Figure 4.18. Model of switched monopole concept…………………………….43
Figure 4.19. Example of four different matching circuits……………………... 44
Figure 4.20. Switched monopole without RF switches………………………... 44
Figure 4.21. Schematic for four matching……………………………………... 45
Figure 4.22. Return loss Graph for switched monopole……………………….. 46
Figure 4.23. Switched monopole 2…………………………………………….. 48
Figure 4.24. Return loss graph - circuit 1, switched monopole 1……………… 49
Figure 4.25. Return loss graph - circuit 2, switched monopole 1……………… 49
Figure 4.26. Return loss graph - circuit 3, switched monopole 1……………… 50
Figure 4.27. Return loss graph - circuit 4, switched monopole 1……………… 50
Figure 4.28. Return loss graph - circuit 1, switched monopole 2……………… 51
Figure 4.29. Return loss graph - circuit 2, switched monopole 2……………… 52
Figure 4.30. Return loss graph - circuit 3, switched monopole 2……………… 52
Figure 4.31. Return loss graph - circuit 4, switched monopole 2....…………… 53
Figure 5.1. Schematic view of Perlos anechoic chamber……………………… 54
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Figure 5.2. Reference dipole antenna………………………………………….. 55
Figure 5.3. Reference dipole antenna return loss graph……………………….. 55
Figure 5.4. Radiation pattern for Reference antenna………………………….. 56
Figure 5.5. Radiation pattern for Reference antenna………………………….. 56
Figure 5.6. Radiation pattern for Reference antenna………………………….. 57
Figure 5.7. Gain for the folded-patch 1 verses specification………………….. 59
Figure 5.8. Radiation pattern for Folded-patch 1……………………………….60
Figure 5.9. Radiation pattern for Folded-patch 1……………………………….60
Figure 5.10. Radiation pattern for Folded-patch 1………………..…………….61
Figure 5.11. Gain for five different capacitances in the loop antenna…………. 61
Figure 5.12. Radiation pattern for Loop antenna………………………………. 63
Figure 5.13. Radiation pattern for Loop antenna………………………………. 63
Figure 5.14. Radiation pattern for Loop antenna………………………………. 64
Figure 5.15. Gain for the different circuits, switched monopole 1…………….. 64
Figure 5.16. Radiation pattern for Switched monopole 1……………………… 65
Figure 5.17. Radiation pattern for Switched monopole 1……………………… 66
Figure 5.18. Radiation pattern for Switched monopole 1……………………… 66
Figure 5.19. Gain for the different circuits, switched monopole 2…………….. 67
Figure 5.20. Radiation pattern for Switched monopole 2……………………… 68
Figure 5.21. Radiation pattern for Switched monopole 2……………………… 68
Figure 5.22. Radiation pattern for Switched monopole 2……………………… 69
VI

List of tables
Table 2.1. Qualities for the three different modes……………………….…….. 15
Table 2.2. The TPS block……………………………………………………… 16
Table 4.1. Value of components for the different switched monopoles……….. 45
Table 5.1. Reference antenna values for calculation of gain and efficiency…... 58
Table 5.2. Folded-patch 1 gain and efficiency results…………………………. 59
Table 5.3. Loop antenna, gain and efficiency results………………………….. 62
Table 5.4. Switched monopole 1, gain and efficiency results…………………. 65
Table 5.5. Switched monopole 2, gain and efficiency results…...…………….. 67
VII

1 Introduction
The passed decade the media consumption has grown rapidly. Devices like video
recorders, video-on-demand and pay-per view offerings have enabled users to
personalize the content they want to watch. Today the majority of the European
population has access to Internet and a large number of TV-channels.
Along with this trend is the amazing development of mobile telephones. Mobile
terminals are packed with new technologies that broaden their functionality. The
mobile terminal converges and can be used as an organizer, game console, music
player, portable radio, agenda, camera, video camera and now, television. The
place of viewing is no longer limited to a television set at home or in a vehicle.
Instead, it is widened to allow personal viewing of television anytime at anyplace.
Television has been brought to mobiles through the use of cellular networks.
However, providing television this way is very expensive and if many users want
to watch the same channel at the same time a lot of bandwidth will be used to
send the same information over and over again.
Digital Video Broadcasting – Handheld (DVB–H) is a standard that makes it
possible to deliver live broadcast television to handheld terminals. There are other
standards that are competing with DVB-H to be the main television provider in
Europe. All the technical problems with the DVB-H standard have not yet been
solved. If DVB-H is to be the main television provider in Europe these technical
problems need to be solved rather quickly. We believe they will be solved and
that the DVB-H standard is the best way to provide television for mobile
terminals.
1.1 Thesis overview
Chapter 2 of this thesis introduces the DVB-H system. It also has one part about
competing standards and the last part of this chapter is an introduction of antenna
theory that is related to this work.
Chapter 3 gives an overview of existing antenna solutions for the DVB-H
frequencies. Chapter 4 describes the design of all our solutions with return loss
graphs and characteristics for the different antennas. In chapter 5 the three final
prototypes are presented and different measurements on these are presented.
Chapter 6 contains the results from all measurements and chapter 7 is for final
conclusions.
1

1.2 Purpose
This thesis has a couple of purposes. In the beginning the work is completely
theoretical and the objective is to collect as much information as possible about
the DVB-H system and summarize this information in the report. It is important to
understand the possibilities and limits that DVB-H offers. The goal is to extract an
antenna specification for handheld devices on the basis of the obtained
information.
When this theoretical part is done the goal is to design some DVB-H antennas and
make measurements on them. The measurements that will be presented for these
antennas are power gain, efficiency, radiation pattern and interference
measurements.
The most important purpose of this thesis is to create a knowledge platform that
makes it easier to design antennas for DVB-H in the future.
2

2 Background
This chapter provides general information about the different DVB standards and
will give the needed knowledge about the system. Basic antenna theory will also
be presented, to help the reader understand later discussions.
2.1 Digital Video Broadcasting
2.1.1 DVB
This part will give the reader an overview of the existing Digital Video
Broadcasting – Terrestrial (DVB-T) system and the future DVB-H system.
The analogue TV system used today has basically remained unchanged for
decades, with the colour TV as the only invention worth mentioning since the
1960s. The European PAL system and the US NTSC system use the resolution of
625 lines respectively 525 lines, and the display is interlaced with only 25 or 30
frames per second. Compared with today’s computer screen with resolution of
1280�1024 and at least 75 Hz frame rate. So, it is naturally that a transition to a
digital system with higher resolution implies better picture and additional features
[1].
Until 1991 digital television broadcasting to the home was thought expensive and
impractical to implement. During 1991 broadcasters and equipment manufactures
discussed unify Europe with one standard for digital TV. The result was a group
called European Launching Group (ELG) that expanded to include the major
European media interest groups, both public and private, the consumer electronics
manufacturers, common carriers and regulators. 1993 ELG renamed itself to
Digital Video Broadcasting (DVB). The work in digital television, already
underway in Europe, moved into top gear. It became clear that Digital Video
Broadcasting–Satellite (DVB-S) and Digital Video Broadcasting–Cable (DVB-C)
were delivering digital video broadcasting before DVB-T. This depends on fewer
technical problems and a simpler regulatory.
1997 the DVB-standards were adopted globally and became the benchmark for
digital television worldwide [2].
DVB is an industry-led group with more than 300 broadcasters, manufacturers,
network operators, software developers and regulatory bodies. One of the main
goals for the group is to develop open standards to prevent the digital TV to
include as many standards as the analogue system (NTSC, PAL and SECAM)
does. Since European Telecommunication Standards Institute (ETSI) adopted
DVB as a standard, it has been implemented in many countries. An EU directive
requires all country which will implement digital terrestrial TV broadcasting to
3

2.1.2 OFDM
choose DVB. But DVB is not the only standard for digital broadcast in the world,
e.g. Japan has developed Integrated Services Digital Broadcasting - Terrestrial
(ISDB-T) and in US they have implemented Advanced Television System
Committee (ATSC) [3].
One of the best things with the digital system compared to the analogue is the
spectrum efficiency. It is possible to send four to six digital channels by the
multiplex instead of one analogue channel on the same frequency. The DVBstandard
uses the video format MPEG-2 while the sound is coded with MPEG-1,
layer II. Normally 80 percent of the capacity is reserved for the video stream and
10 percent each for the sound and teletext [4].
Orthogonal Frequency Division Multiplexing (OFDM) was developed in 1960,
but it has not been used much until lately. It has become very popular because it is
now possible to build the integrated circuits that are needed to perform the highspeed
digital operations necessary for OFDM. It is based on Frequency Division
Multiplexing (FDM), which is a technology that uses multiple frequencies to
simultaneously transmit multiple signals in parallel [5].
It is different to transmit a terrestrial broadcasting channel than to transmit a
satellite link or a cable transmission channel. You will get reflections from
buildings and mountains, which will result in a multi path propagation of the
transmitted signal (See figure 2.1). These reflected signals will be time-delayed at
the receiver and can cause harmful interference. If the delay time of the echo
signals is in the range of the symbol duration of the transmitted signal it will result
in a selective behaviour of the frequency response [6].
The individual echoes which successively arrive at the receiver, vary in amplitude
and delay time. By superimposing themselves on the main signal they cause
fluctuations in the complex channel transfer function. A characteristic value of
such fading channels is given by the ratio of the directly received signal power to
the total of the power of all echo signals [7].
It is possible to compensate for the distortions in the frequency domain by using
suitable equalizers. Usually the time delay of the echo exceeds the symbol
duration. This means that the adjacent symbols affect each other. A filter for inter
symbol interference must therefore be of a high order, which is hard and
expensive to implement.
To minimize the number of symbols affecting each other you can just make the
duration of the transmitted symbol longer. This can be done by the parallel
transmission of several symbols. If, for instance, the information to be transmitted
4

is simultaneously modulated into 1000 symbols of different carrier frequencies,
then for each individual symbol there is a time slot available, which before
changing to parallel transmission, was allotted to all the sequentially transmitted
symbols together. The value of the bandwidth and the transmission time of some
information can vary as a function of each other. If OFDM is used to send a
symbol the frequency range required for the transmission of an individual
subsymbol is reduced [6].
In the OFDM system all the subcarrier frequencies should be orthogonal to each
other. To get the subcarriers to be orthogonal to each other the Inverse Discrete
Fourier Transform (IDFT) must be calculated. It is necessary for a predetermined
number of subsymbols to be available simultaneously at the input of the IDFT
unit. The data that are to be transmitted are temporarily stored until the required
number of subsymbols for parallel transmission are ready to be sent, and are then
read out in parallel.
One of the major problems of OFDM is that the peak amplitude of the emitted
signal can be considerably higher than the average amplitude. This Peak to
Average Ratio (PAR) problem comes from the fact that an OFDM signal is the
superposition of all the sinusoidal signals of the different subcarriers. On average
the emitted power is linearly proportional to the number of carriers. Sometimes
the signals on the subcarriers ad up constructively and then the amplitude of the
signal is proportional to the number of carriers. There are three ways of dealing
with this:
1. Use a power amplifier in the transmitter that can amplify linearly up to the
possible peak value. This solution requires expensive and power
consuming class A amplifiers.
2. Use a nonlinear amplifier, and accept that the amplifier characteristic will
lead to distortions of the output signal. Those nonlinear distortions destroy
the orthogonality between the subcarriers, and also leads to out of band
emissions.
3. Use PAR reduction techniques. There are several different approaches
these will not be described in this rapport.
5

Figure 2.1. Multi path propagation of the transmitted signal.
The OFDM transmission scheme has the following key advantages:
• Makes efficient use of the spectrum by allowing overlap.
• By dividing the channel into narrowband flat fading subchannels, OFDM
is more resistant to frequency selective fading than single carrier systems
are.
• Eliminates ISI and IFI through use of a cyclic prefix.
• Using adequate channel coding and interleaving one can recover symbols
lost due to the frequency selectivity of the channel.
• Channel equalization becomes simpler than by using adaptive equalization
techniques with single carrier systems.
• In conjunction with differential modulation there is no need to implement
a channel estimator.
• Is less sensitive to sample timing offsets than single carrier systems are.
• Provides good protection against co-channel interference and impulsive
parasitic noise.
In terms of drawbacks OFDM has the following characteristics:
• The OFDM signal has a noise like amplitude with a very large dynamic
range, therefore it requires RF power amplifiers with a high peak to
average power ratio.
• It is more sensitive to carrier frequency offset and drift than single carrier
systems are due to leakage of the DFT [8].
6

2.1.3 Reed-Solomon Codes
2.1.4 DVB-T
Reed-Solomon codes (RS codes) are block-based error correcting codes and are
very widely used in digital communications and storage. RS codes can detect and
correct errors within blocks of data and are used in a lot of applications, for
example:
• Storage devices (including tape, compact, DVD, barcodes, etc)
• Wireless or mobile communications (including cellular telephones,
microwave links, etc)
• Satellite communications
• Digital television / DVB
• High-speed modems such as ADSL, xDSL,etc
The RS encoder takes a block of digital data and adds extra "redundant" bits.
Errors occur during transmission or storage for a number of reasons (for example
noise or interference, scratches on a CD, etc). The Reed-Solomon decoder
processes each block and attempts to correct errors and recover the original data.
DVB-H uses RS (255,191), were 191 is the number of information symbols input
per block and 255 the number of symbols per block that the encoder outputs, the
code rate can be varied. The term symbol may represent one bit or a number of
bits. The number and type of errors that can be corrected depends on the
characteristics of the Reed-Solomon code and is always half of the parity
symbols. So in the DVB-H system it is possible to correct up to 32 errors in a
codeword [9].
DVB-T is the terrestrial mode for Digital Video Broadcasting. DVB-T has been
selected as the common standard for digital television in Europe and is the base
platform for DVB-H, witch makes it possible to transmit IP-packages to handheld
terminals. The standard for DVB-T was adopted in December 1995. In November
1998 the first DVB-T network became operational in the United Kingdom. Since
1998 DVB-T has been introduced in Europe, Australia, Singapore and Taiwan [6].
See figure 2.2 to see the spread of the different digital TV specifications.
In DVB-T, each program is sent over a separate logical channel that is identified
by a unique packet identifier. All users that have access to a specific service may
receive any program on that logical channel. The control streams used with the
packet identifiers such as the program and service information are transmitted
repeatedly from the head end to the users [10].
7

Usually the Moving Pictures Experts Group (MPEG-2) compression code is used
to compress DVB-T transmissions. However the latest DVB-T specification
allows AVC/H.264 as a compliment.
DVB-T divides the signal into several thousand orthogonal subcarriers using
ODFM. The system is designed to operate with the Ultra High Frequency (UHF)
spectrum, and can be used with 6, 7 or 8 MHz channel bandwidths depending on
the regional demands. DVB-T has many parameters that can be changed to best
fulfill the regions needs. The parameters that can be changed are the number of
subcarriers, guard interval, whether a hierarchical signal is used, error correction
level and the modulation scheme. The number of subcarriers used affects what
Doppler frequency the system can handle and what range it can cover. The
Doppler frequency is the shift in frequency and wavelengths depending on what
speed the terminal have. DVB-T has two modes that determine the number of
subcarriers, 2k and 8k. The guard interval parameter determines the signal’s
tolerance to echo. Because the system has this ability to tolerate echo it is possible
to use the spectrum efficient Single Frequency Networks (SFN). A SFN is a
network of several stations that broadcast the same signal simultaneously using
multiple transmitters [11].
Today DVB-T is more effective than its initial requirements. For example DVB-T
can be used in public transportations and in cars. It is also possible to offer IPdatacasting
over the DVB-T network even though this network was not designed
to target mobile handset. The problem with IP-datacasting over the DVB-T
network is the battery consumption.
Figure 2.2. Digital TV standards used in the world.
8

2.1.5 DVB-H
DVB-H is the latest developed standard within the DVB transmission standards.
The work with the technical specification started in autumn 2002 and was finished
in February 2004. In November the same year ETSI finally published the DVB-H
standard as a European Norm [12].
The first step towards DVB-H was taken when the ability of DVB-T to deliver
broadcast services to mobile receivers was demonstrated.
The problem was the power consumption, and that lead to the new standard,
DVB-H that enables IP datacasting. IP datagrams that are broadcasted over DVB-
H are encapsulated inside the MPEG-2 transport stream using the Multi Protocol
Encapsulation (MPE) to improve mobile performance [11].
DVB-H is so similar to DVB-T that it is possible to send DVB-H signals along
with DVB-T signals in the multiplexer, between 470 – 862 MHz [4]. That it is
possible to reuse DVB-T transmission equipment makes it an interesting
technique in an economically point of view. DVB-H has a downstream channel
with capacity off several Mbit/s. It may be used for radio and video streaming, file
downloads and many other applications.
DVB-H includes the following additions to improve the features for a mobile
terminal:
• Time slicing, in order to reduce the average power consumption of the
terminal and to make it possible to smooth handovers.
• MPE-FEC, for improving Doppler performance and tolerance to impulse
interference.
• 4k-mode, provides more flexibility to network design.
• In-depth symbol interleaver, for further improvement of the transmitted
signal robustness in mobile environment.
• Extended Transmission Parameter Signaling (TPS).
The DVB-H standard recommends using H.264 (MPEG-4 Part 10: Advanced
Video Codec) and the CIF resolution (352*288) in difference to DVB-T that uses
MPEG-2 code and SDTV (720*576) [14]. During 2004 and 2005 successful trials
have been going on in Helsinki, Berlin and Pittsburg.
Several European countries have plans to launch commercial services already
2006, and according to market prospects, the sales figures will be somewhere
between 10 and 100 millions 2008 [15]
9

2.1.5.1 Standardization of DVB-H
The DVB-H system is not specified in one single document. Instead some
modifications to other DVB specifications have been made (See figure 2.3).
• The central specification is the DVB-H system specification EN 302 304.
It has been published as the European norm for DVB-H.
• The physical layer specification has been integrated in the DVB-T
specification EN 300 744. This standard has been published as a new
version, which contains the DVB-H physical layer enhancements in an
annex.
• Time slicing and MPE-FEC have been described in a new chapter of the
DVB Data Broadcast specification EN 301 192. This document also
defines the Multi-Protocol Encapsulation.
• DVB-H-specific signaling has been integrated into the DVB Service
Information (SI) specification EN 300 468.
Figure 2.3. The connection between the different specifications defining DVB-H.
The system specification determines mandatory and optional elements. The
system specification is complemented by DVB-H implementation guidelines,
which contain hints for the use and practical implementation of the standard. The
DVB Project released these guidelines in the autumn of 2004 [12].
10

2.1.5.2 Time slicing
A large problem with handheld terminals is the limited battery capacity. It is
impossible to receive and decode a broad band, high data-rate stream like the
DVB-T data stream with a battery terminal. The receiver and demodulation part in
the terminal would use too much power and the battery would run out quickly. In
the beginning of the development of DVB-H it was shown that the power
consumption of a DVB-T receiver is about 1 Watt, which is too much [14]. A
some-what lower value seems possible but the desired target of 100 mW as a
maximum threshold for the entire front end incorporated in a DVB-H terminal is
still unobtainable for a DVB-T receiver.
A considerable drawback for battery-operated terminals is the fact that with DVB-
T, the whole data stream has to be decoded before any one of the services (TV
programs) of the multiplex can be accessed. The main reason why DVB-H
consumes less power is that the receiver only has to receive and process the parts
of the data stream that contains the information needed for the selected service.
For this to be possible the data stream needs to be reorganized in a suitable way.
With DVB-H, service multiplexing is performed in a pure time-division
multiplex. The data of one particular service are therefore not transmitted
continuously but in compact periodical bursts with interruptions in between. In the
interruption between bursts, other services are sent. This leads to a continuous
data stream. This data stream can be received in time intervals where the receiver
is synchronized with the service you want to receive. Then the receiver can be
shut down when the other services that you have no interest in are sent. This way
of dividing the signal is called time slicing [15].
When time slicing is used to receive the signal it saves a lot of power because the
receiver can be turned off most of the time. When the receiver is on, the received
signal is buffered in a memory and then read out from the buffer in the service
data-rate. When the receiver is turned on the next time and receives a new data
stream, this data is buffered in the memory and the video can be played
continuously. For the receiver to know when it is time to turn itself on again after
an off-time, data containing information about how long the receiver should be
turned off between the bursts, has to be sent in each burst.
The duration of one burst is in the range of several hundred milliseconds whereas
the power save time may amount to several seconds. The receiver has to be turned
on before it is time to receive data and therefore it is turned on 50-250 ms before
calculated receiving time. Depending on the ratio between on time and off time,
the resulting power saving may be more than 90 %.
As an example, figure 2.4 shows a cut-out of a data stream containing time-sliced
services. One quarter of the assumed total capacity of the DVB-T channel of
11

13.27 Mbit/s is assigned to DVB-H services whereas the remaining capacity is
shared between ordinary DVB-T services. This example shows that it is possible
to transmit both DVB-T and DVB-H within the same network.
Another benefit with time slicing is that the receiver is able to search for the
service in use in other cells during the receiver’s off time. In this way a channel
handover can be performed at the border between two cells without the user
knowing anything about it [6].
Figure 2.4. An example of the data sent trough one multiplexer.
2.1.5.3 Multi Protocol Encapsulation – Forward Error Correction
Handheld devices with small antennas make the reception of high data rate
streams in mobile environment unreliable and difficult. Because of that Multi
Protocol Encapsulation – Forward Error Correction (MPE-FEC) was added to the
DVB-H standard to improve the C/N- and Doppler performance in mobile
channels and to improve the tolerance against impulse interference [16]. The use
of MPE-FEC is optional.
In contrast to other DVB transmission systems based on the DVB transport stream
adopted from the MPEG-2 standard, the DVB-H system is based on Internet
Protocol (IP). Therefore is the base-band interface an IP interface, this interface
allows the DVB-H system to be combined with other IP networks. The MPEG-2
transport stream is still used, because the IP data are embedded into the transport
stream by means of the Multi Protocol Encapsulation (MPE), a protocol defined
by DVB Data Broadcast Specification. On the same level as MPE is an additional
Forward Error Correction (FEC) added. This technique is called MPE-FEC and is
the second main innovation besides time slicing [15]. Intensive testing of DVB-H,
by DVB member companies showed that use of MPE-FEC improves the result by
7 dB over DVB-T [12].
The MPE-FEC scheme is located on the link layer at the level of input IP streams
before they are encapsulated by means of the MPE. The MPE, MPE-FEC and
time slicing techniques are neighboring in the transmitter block diagram (See
12

figure 2.5). All three elements together form the DVB-H codec, which contain the
essential DVB-H functionality.
The input IP streams coming from different sources as single elementary streams
are multiplexed one by one according to the time slicing method. The MPE-FEC
error protection is calculated and added separately for each single elementary
stream before they are encapsulated into the transport stream. All data processing
is carried out before the transport stream interface to guarantee compatibility to a
DVB-T transmission network [15, 30].
2.1.5.4 MPE-FEC frame
Figure 2.5. The three elements that form the DVB-H codec.
The MPE-FEC scheme consists of RS code in conjunction with a block
interleaver. The MPE-FEC encoder creates a specific MPE-FEC frame (See figure
2.6). In that frame are all DVB-H coded input data inserted. The frame consists of
255 columns and a maximum of 1024 rows and with every cell equivalent to one
byte, the maximum frame size is almost 2 Mbit.
A frame is divided in two parts, the application data table and the RS data table.
The application data table is the 191 columns to the left and is filled with the IP
packets of the service to be protected. The first byte of the first datagram inserts in
the upper left cell and going downwards the first column. If a datagram is longer
than a column it continues on top of the next column.
With the application data table filled with datagrams or zero padding it is possible
to calculate the 64 Parity bytes in the RS data table for each row with RS
(255,191) code. When the application data table is filled with IP packets and RS
data table with parity bits the MPE-FEC frame is ready for transmission [17]. The
IP packets are read out of the application data table and encapsulated in IP
sections by means of the MPE method. The IP data is carried in MPE sections
irrespective MPE-FEC is used or not. This makes reception backwards compatible
with MPE-FEC ignorant receiver.
13

Every section has information in the header about start address for the IP
datagram. The address indicates the position for the first byte of the IP datagram
in the application table. This application data is followed by the parity bytes in the
RS data table that are read out column by column and encapsulated in separate
MPE-FEC sections. The FEC frame structure also contains a block interleaving
effect in addition to coding. That means that the receiver can put the datagram in
right order in the application table and mark it “reliable” for the RS decoder. A
flag marks the end of the application data table. If all application data is received
correctly none of the MPE-FEC sections are necessary. That is optimal if time
slicing is used, because then the receiver can go to sleep [17].
2.1.5.5 4K mode
Figure 2.6. The MPE-FEC frame.
DVB-T provides two different modes for different topologies, 2K and 8K mode.
DVB-H also disposes of an intermediate 4K mode that has a little of both 2K and
8K modes qualities. The qualities of the different modes can be seen in Table 2.1.
It allows twice as long distance between receiver and transmitter in SFNs
compared to the 2K mode and it is less susceptible to Doppler frequencies in case
of mobile reception compared to the 8K mode. The 4K mode shall make the
network planning for DVB-H easier, this does not apply for DVB-T since it does
not include the 4K mode [10].
To make transmissions with the 4K mode possible a new symbol interleaver with
4096 OFDM carrier frequencies was specified. In connection with the three
network modes a new symbol-interleaving scheme is defined (See figure 2.7). A
DVB-H terminal should support all three modes and then needs an 8K symbol
interleaver. It is preferred to use the relatively big memory of the 8K symbol
interleaver in all three network modes. This symbol interleaver is able to process
the amount of one complete 8K OFDM symbol or alternatively two 4K OFDM
14

symbols or four 2K OFDM symbols. This way the memory is used more
effectively and it results in an increased interleaving depth in the 2K and 4K
modes, which can be expected to improve performance. If the full memory
interleaving solution is used it is called in-depth interleaving [15].
Table 2.1. Qualities for the three different modes.
Mode
OFDM parameter 2K 4K 8K
Overall carriers (=FFT size) 2048 4096 8192
Modulated carriers 1705 3409 6817
Useful carriers 1512 3024 6048
OFDM symbol duration (µs) 224 448 896
Guard interval duration (µs) 7, 14, 28, 56 14, 28, 56,112 28, 56,112,224
Carrier spacing (kHz) 4.464 2.232 1.116
Maximum distance of
transmitters (km)
17 33 67
Figure 2.7. DVB-H symbol interleaving scheme.
2.1.5.6 Transmission Parameter Signalling - TPS
So called TPS data is provided in DVB-H to inform the receiver about the
modulation and coding scheme and wheter DVB-H-specific features are used and
if so, which ones. The TPS is transmitted in parallel on 17 TPS carriers for the 2k
mode, 34 carriers for 4k mode and on 68 carriers for 8k mode. The TPS is defined
over 68 OFDM symbols, referred to as one OFDM frame. Each TPS block
contains 68 bits, defined as table 2.2.
15

Bit number
Table 2.2. The TPS block.
Purpose/Content
S0
Initialization
S1 to S16
Synchronization word
S17 to S22
Length indicator
S23, S24
Frame number
S25, S26
Constellation
S27 to S29
Hierarchy information
S30 to S32
Code rate, HP stream
S33 to S35
Code rate, LP stream
S36, S37
Guard interval
S38, S39
Transmission mode
S40 to S47
Cell identifier
S48 to S53
DVB-H features
Error protection
S54 to S67
Every TPS carrier is differential binary phase shift keying (DBPSK) modulated.
The first bit of the TPS is initialising the DBPSK.
The bits 1 to 16 of the TPS form a synchronization word. Together four OFDM
frames forms one OFDM super-frame. Frame numbers 1 and 3 have the same
synchronization word, 0011010111101110, and frames 2 and 4 have following
synchronization word, 1100101000010001.
S17 to S22 is used as a length indicator to signal number of used bits of the TPS.
The next section of the TPS numbers the four frames inside the super-frame from
one to four, bit S25 and S26 determine the modulation scheme. S27 to S29 indicates
if the transmission is hierarchical and if in-depth interleaver is used or not.
The code rate for HP stream respectively LP stream is decided from s30 to S35. The
guard interval, transmission mode (2k, 4k or 8k), cell identifier are signaled by the
following twelve bits.
DVB-H services are indicated by S48 and S49, the following three bits are reserved
for future use and shall be set to zero. S48 shows if time slicing method is used or
not and s49 indicates if at least one elementary uses MPE-FEC.
The last 14 bits contents the parity bits for error protection [18, 6].
16

2.2 Competing standards
The DVB-H standard has some competing standards used in different parts of the
world, some of them will be briefly explained here.
2.2.1 Satellite-Digital Mobile Broadcast
In Korea a digital broadcasting network is already deployed, it is called Satellite-
Digital Mobile Broadcast (S-DMB). S-DMB is a hybrid satellite/terrestrial gapfiller
system. It relies on very high power geo-stationary satellites and a network
of gap-fillers co-sited with Base Transceiver Station (BTS) to provide urban
indoor coverage. Signals from the satellite and the gap-fillers are synchronized so
the terminal can combine them. Even forward error correction and interleaving is
used to make the transmission more reliable.
A multi-beam configuration with 6 spots to cover Western Europe and three
satellites is preferred. In this solution, by applying a frequency reuse scheme it is
possible to achieve a capacity of up to 2 Mbits/s per beam with good outdoor and
first wall indoor reception.
Even though one spot covering several countries the capacity can be shared by
several national mobile operators and it is possible to support different
languages/cultural multimedia services on the same carrier. It targets mainly the
delivery of multimedia push & store and streaming services to mobile handsets.
S-DMB uses the IMT2000-band and is fully compliant to the 3rd Generation
Partnership Project (3GPP) standard for Mobile Broadcast/Multicast Service
(MBMS), including its air interface. That makes it cheap to upgrade the Universal
Mobile Telecommunications (UMTS) terminals to support Mobile Satellite
Service-band (MSS).
S-DMB can be used as a complement to any terrestrial network for example as a
multicast network over unicast terrestrial 3G UMTS mobile network [19, 20, 21].
2.2.2 Mobile Broadcast/Multicast Service
MBMS is an IP data cast (IPDC) type of service that can be offered by existing
GSM and UMTS cellular networks. The MBMS has been standardized in various
groups of 3GPP. The standard will facilitate the integration of broadcast and
multicast transmission into mobile networks. This will bring high quality mobile
TV while lowering bandwidth at lower cost. The service seems to bee attractive,
as quite lot of operators and equipment manufactures have participated in the
standardization work.
17

The MBMS was designed to eliminate the need for operators to introduce new
hardware into their networks. It is a solution for transferring light video and audio
clips, although real streaming is also possible. An important feature of MBMS is
that it can be multiplexed with existing services on the same carrier. This will
allow operators to offer voice, data and TV over a common service and network
infrastructure. For heavy streaming in a wide area for a large and concentrated
audience the DVB-H system, which is the main alternative to MBMS, is more
suitable.
Practical network implementations may be expected by the third quarter of 2007
and the first terminal to be available the third quarter the year after. According to
estimations 30% of the terminals will support MBMS the year 2010 [22, 23].
18

2.3 Antenna theory
This section describes basic antenna theory, to easier understand later discussions.
2.3.1 Efficiency, directivity and gain
Radiation efficiency ηrad is defined as the ratio between the radiated power Prad
and the power accepted by the antenna Pin (see figure 2.8)
P
rad η rad =
(2.1)
Pin
The directivity D and the gain G of an antenna are connected to each other by ηrad
as
G = ηrad
D
(2.2)
Directivity describes the directional property of an antenna and the gain takes into
account the losses in the antenna structure. For an ideal antenna the gain and the
directivity are equal.
Figure 2.8. Voltage reflection from a mismatched load.
Γ is the refection coefficient, ZL and Z0 are the impedances of the load and
transmission line, respectively. Pt, Pin and Prad are the (total) incident power to the
load, the power accepted by the load and the power radiated by the load,
respectively.
2.3.2 Reflection from a mismatched antenna
The antenna impedance, ZL, must be equal to the characteristic impedance for the
transmission line feeding the antenna, Z0, otherwise part of the voltage will be
reflected from the antenna. How large this reflected voltage is can be measured in
a network analyser as the parameter S11. The reflection coefficient can be
calculated with following equation:
Z
Z
− Z
+ Z
L 0
Γ =
(2.3)
L
0
19

There will be no reflection only when the impedance of the antenna and the
characteristic impedance of the transmission line are equal, then the antenna is
perfectly matched. To achieve good antenna performance in a wide frequency
range a slight mismatch in the whole band is the best solution. The reflection is
unwanted because a part of the power is not delivered into the antenna, in the
transmission case and vice versa in the receiving case. The impedance matching is
an important task in the antenna design. Some basic methods for matching are
presented later [25].
The voltage at a point on a transmission line is in the general case the sum of two
waves travelling opposite directions. This scenario is known to create a standingwave
pattern along the transmission line. The ratio between the maximum and the
minimum value of this sum is termed the voltage standing-wave ratio and can be
calculated from the reflection coefficient with equation 2.4.
1+
Γ
VSWR = (2.4)
1−
Γ
Power loss due to reflection, called reflection loss Lrefl, can be calculated from
1
L refl = 10 log
(2.5)
2
1 − Γ
Return loss describes the ratio between the propagated and the reflected power
and can be calculated from
1
L retn = 10log
(2.6)
2
Γ
VSWR, Lrefl and Lretn are all calculated from the reflection coefficient and they are
normally used to define the impedance bandwidth. In figure 2.9, the bandwidth
BWabs is defined by the absolute value of the reflection coefficient Γ ≤ 0.
501,
which corresponds to the return loss criterion of Lretn ≥ 6dB
or the VSWR
criterion of S ≤ 3.
01.
This limit has to be set in each case separately. Nowadays
Lretn ≥ 6dB
is an acceptable upper limit on the bandwidth criterion for built-in
antennas [24].
20

Figure 2.9. Impedance bandwidth defined according to the absolute value of the
reflection coefficient ⎟Γ⎜ = ⎟S11⎜ = -6 dB. BWabs is the absolute frequency
bandwidth.
From the absolute bandwidth the relative bandwidth can be defined according to
the following equation.
BWabs
Br
= (2.7)
CF
Where BWabs is the absolute frequency bandwidth and CF is the arithmetic center
frequency of the impedance band.
2.3.3 Resonance Circuit
The small antennas studied in this thesis are resonators. Input impedance of such
antennas consists of one resistive part and one reactive part according to the
following formula
( f ) R ( f ) + jX ( f )
Za a
a
= . (2.8)
The resistance Ra(f) represents the radiation and ohmic loss. Xa(f) represents the
reactive, non-radiating energies of the antenna structure that consists of inductive
and capacitive components.
Resonance in the antenna structure is achieved when the inductive part and the
capacitive part cancel each other, which results in the best efficiency for the
antenna. This can be achieved by a self-resonant structure, but only inside a
narrow bandwidth, or by a matching circuit. A short-circuited λ / 4 or an open
λ / 2 antenna normally achieves the self-resonance, where λ is the wavelength at
the used frequency in the used medium.
21

A resonator can be modelled as a parallel resonance circuit, as shown in figure
2.10.
Figure 2.10. Parallel resonance circuit.
The total energy stored in the resonance structure, is the average energy stored in
the capacitance C added with the average energy stored in the inductance L. These
definitions give the following formula to calculate the resonance frequency [24].
f r
1
= (2.9)
2π
LC
2.3.4 Quality Factor
The quality factor describes the ratio between energy stored and energy lost in a
resonator circuit per unit time. There are numerous definitions of Q, but the most
fundamental one is
Maximum energy stored in the network
Q = 2π
*
(2.10)
energy dissipated per cycle
Note that the Q is dimensionless and that it is fundamental because it does not
care about what stores or dissipates the energy. For that reason it applies perfectly
well to both resonant and non-resonant systems. Therefore it is appropriate to
characterise a RC circuit, or even a single component, by the Q [25].
The quality factor for the circuit in figure 2.10, according to formula 2.2 is
ωrW
ωrC
1
Q = = =
(2.11)
P G G * ω * L
l
r
Where ω r is the angular resonant frequency, W is the energy stored and Pl is
power loss in a resonator structure.
The total loss can be divided into several load components, where each of them
can be described by different quality factors. The total quality factor is called
loaded quality factor (Ql) and describes the total loss and can be divided into the
22

unloaded quality factor (Q0) and the external quality factor (Qe). The unloaded
quality factor describes the internal losses, which can be further divided into
radiation, conductor and dielectric losses. The unloaded and radiation (Qrad)
quality factors are in an ideal case equal but in practise there are losses in
dielectrics and conductors, which are included in the dielectric (Qd) and conductor
(Qc) quality factors. The relation between all different quality factors is shown in
equation (2.12) [26].
1
Q
2.3.5 Bandwidth
l
1 1 1 1 1 1
= + = + + +
(2.12)
Q Q Q Q Q Q
0
e
rad
c
d
e
The useful bandwidth is limited by a number of factors, for example impedance,
gain, polarization or beamwidth. The impedance matching is the main factor
limiting the bandwidth of a resonator. The input impedance of a small antenna for
handheld devices varies quickly with frequency, which limits the frequency range
over that the antenna can be matched to its feed line.
The unloaded quality factor is very important because it determines the bandwidth
of the antenna. The relatively Bandwidth and the unloaded has the connection
shown in equation (2.13).
B r
=
1
Q
0
( TS −1)(
S − T )
S
23
(2.13)
Where VSWR = S over the impedance bandwidth and T = Y0/G, where G is the
conductance seen at the input of a resonator at the resonance frequency and Y0 is
the characteristic admittance of the transmission line [26].
2.3.5.1 Impedance matching
A basic task in radio engineering is to match the antenna load to the characteristic
impedance of the feed line to prevent voltage reflection (see figure 2.11).
A matching circuit can be realized by lumped elements (capacitor and inductor),
distributed elements (stub or quarter-wavelength transformer) or by resistive
matching. It is always possible to make a matching circuit as long as the Ra(f) of
the input impedance is not zero. To design a matching circuit, formulas or Smith
chart can be used. Resistive matching is not recommended because of the losses it
results in.
Matching network by lumped elements is close to ideal as long as the physical
lengths of the components are clearly smaller than the free-space length and the

ohmic losses are small enough. A complex load can always be matched by two
lumped components.
At higher frequencies, when the lumped components not are ideal, it is better to
implement the matching circuit by using distributed elements like tuning stub. It is
possible to use distributed elements even at RF frequencies but the lengths of the
stubs may be to long for printed circuit board.
A resistive attenuator can be placed between a load and a transmission line for
giving resistive matching. If a 3-dB attenuator is used, the signal level and the
total efficiency will be attenuated with 3 dB, while the reflection coefficient
decreases 6 dB. Resistive matching can be used if power consumption is not a
problem, but usually resistive matching is not acceptable, because valuable power
cannot be wasted in the resistive matching circuit in handheld devices.
2.3.6 Bandwidth enhancement
Figure 2.11. Matching circuit scheme.
The matching networks described above give perfect matching at single frequency
points. To achieve matching over certain impedance band the matching criterion
must be loosen. Instead of a criterion with return loss, Lretn = -∞ dB, usually the
return loss is chosen to be less than –6 dB for antennas in handheld devices.
To make the bandwidth as wide as possible, there are two characteristics to
choose to loosen, either to make the volume larger or lower the efficiency.
Impedance, volume and efficiency are three antenna characteristics that depend on
each other, so the best compromise to reach the specified performance must be
found. Changing the volume for internal antennas for DVB-H to make them
wideband is not easy because the small size of the terminal, and users do not want
terminals in non-pocket-size.
One method that makes it possible to enhance the bandwidth is to worsen the
efficiency, which can be made in three ways, accepting mismatching, resistive
matching with attenuator or adding resistive losses. As mentioned before, resistive
24

losses should be avoided in handheld devices, so accepting mismatching is the
best choice to get wider bandwidth.
Other possible, but more complicated methods to make the bandwidth as wide as
possible is multiple resonant antennas and to split the frequency range into several
frequency bands and design one matching circuit to each band and switch between
these.
An alternative to wideband antennas is a tuneable antenna that is narrowband but
possible to tune in a large frequency band. It can be made by adjustable
components in the matching network, in former time it was adjusted mechanical
that is not possible with handheld devices. A possible solution for the DVB-H
system is to use a control signal from the tuner to adjust the matching circuit [24,
25, 26].
25

3 Possible solutions
This chapter describes different existing antenna types that can receive a TV
signal.
3.1 Dipole and Monopole antenna
The dipole is one of the most basic antennas. It consists of a straight piece of wire
that is cut at the centre and fed with a balanced generator. This type of antenna is
resonant at the frequency were the conductor length is a half wavelength. This
means that to be resonant at 600 MHz (λ=500mm) it needs a length of 250mm
A quarterwave monopole is a ground plane dependent antenna that must be fed
single ended, which makes it an unbalanced antenna. The ground plane is very
important, because the larger the ground plane the more efficient antenna. The
ground plane is half of the monopole antenna that has a radiation pattern like the
dipole antenna. It depends on that a quarter wave monopole “mirrors” itself in the
ground plane, much in the same way one sees their own reflection in the water.
According to that is the length of a quarter wave monopole antenna half of a
dipole antenna, at 600 MHz 125 mm [27].
3.2 Yagi-Uda
The Yagi-Uda antenna is a wideband antenna that is a very good radiator in the
frequency range 3-3000 MHz. This antenna consists of a number of linear dipole
elements, as shown in figure 3.1. The first dipole element after the reflector is
energized directly by a feed transmission line. The rest of the elements act as
parasitic radiators, the currents are induced in these elements by mutual coupling.
The parasitic elements in the direction of the beam are smaller in length than the
feed element. Typically the length of the feed element is 0.45-0.49λ and the
directors are about 0.4-0.45λ. It is not necessary for the directors to be of the same
length or to have the same diameter. The separation between the directors are also
not necessary the same for uniform design.
The most common feed element for Yagi-Uda antenna is a folded dipole. When
this folded dipole is used all elements placed behind it will act as reflectors. The
major role of the reflector is played by the one placed next to the energized
element. Very little is gained with a second reflector.
The high gain of a Yagi-Uda antenna comes from the directors, the more directors
the higher gain. Practically very little is gained by the addition of more than 12
directors, usually 6-12 are used. However, many arrays have been designed and
built with 30 to 40 elements, with a typical gain of about 15-17.5 dBi [28].
26

3.3 Loop
Figure 3.1. Yagi-Uda antenna.
A simple, inexpensive and very versatile antenna type is the loop antenna, that
takes many different forms such as a rectangle, square, triangle, ellipse, circle and
many other configurations and they are usually classified in two categories,
electrically small and electrically large. Electrically small antennas are those
whose overall length (number of turns times circumference) much shorter than a
wavelength and the electrically large loops are those with a circumference about
one free-space wavelength. Most of the applications of the loop antennas are in
the HF (3-30 MHz), VHF (30-300 MHz) and the UHF (300-3000 MHz) bands.
Loop antennas with electrically small circumference are very poor radiators and
are very seldom employed for transmission in radio communication. When they
are used in such application, it is usually in receiving mode where antenna
efficiency is not as important as the signal-to-noise ratio. Electrically large loop
antennas are used primarily to achieve directional characteristic [28].
3.4 Microstrip antenna
Microstrip antennas provide interesting features for spacecraft, aircraft, mobile,
radio and wireless communication, in particular their low weight, cost,
performance, ease installation and thin profile. They are easily mounted on flat or
gently curved surfaces. Printed antennas (patches, microstrip) can use square,
rectangular, circular, triangular, elliptical or even more complex shapes as
radiating elements. It is parameters like bandwidth, side lobes, polarization that
decide which shapes that are most suitable. Since patches are narrow band
radiators, their main dimension is about a half-wavelength. The directivity for a
microstrip is therefore comparable to that of a half-wave dipole. This drawback
may be overcome by grouping a number of patches to form an array.
27

Major operational disadvantages of microstrip antennas are their low efficiency,
low power, high Q and very narrow frequency bandwidth. These drawbacks are
avoided by building antennas on thick low-permittivity substrates, where larger
bandwidth and efficiency are achieved.
The four most popular configurations that are used to feed microstrip antennas are
the microstrip line, coaxial probe, proximity and aperture coupling. These are
displayed in figure 3.2. The microstrip line feed (figure 3.2 a) is easy to fabricate,
simple to match by controlling inset position and rather simple to model.
However, this structure cannot be optimised either as an antenna or as a
transmission line, because the requirements for both are contradictory. This means
that some compromise must be made, in which the feed line does not radiate too
much at the discontinuities.
Coaxial line feed (figure 3.2 b), where the inner conductor of the coax is attached
to the radiation patch and the outer conductor with the groundplane, are also
widely used. The coaxial probe feed is also easy to fabricate and match. However,
it has narrow bandwidth like the microstrip line feed and it is more difficult to
model, especially for thick substrates.
Of the four different feeds described here, the proximity (figure 3.2 c) has the
largest bandwidth and is somewhat easy to model. However its fabrication is
somewhat more difficult. The length of the feeding stub and the width-to-line
ratio of the patch can be used to control the match.
The aperture coupling (figure 3.2 d) is the most difficult of all four to fabricate
and has narrow bandwidth. The aperture coupling consists of two substrates
separated by a ground plane. On the bottom side of the lower substrate there is a
microstrip feed line whose energy is coupled through a slot on the ground plane to
the patch. This arrangement allows independent optimisation of the feed
mechanism and the radiating element. Matching is typically performed by
changing the width of the feed line and the length of the slot [28, 29].
28

PIFA
Figure 3.2. Four different configurations to feed microstrip antennas.
PIFA stands for Planar Inverted F Antenna and is a common used antenna for
mobile phones today, this because it has an omni directional radiation pattern and
is easy to embed. Figure 3.3 shows a simple single band PIFA that has a low
profile resonant element that is about a quarter wavelength long. The impedance
matching can be changed by moving the feed point and is lowered by connecting
the feed nearer the ground point. The antenna type can have many resonances and
are achieved by making different patterns in the antenna element [32].
Figure 3.3. PIFA antenna.
29

4 Design and testing of antenna solutions
In this chapter the design of the different antennas and the return loss graphs are
presented.
4.1 Required antenna performance
The antennas that are presented in this chapter must fulfil bandwidth and gain
requirements on the basis of the DVB-T specification. The frequency range that
DVB-H is specified for is from 470 to 862 MHz, but in case the GSM 900 is used
the upper frequency is limited to channel 49 (702 MHz) due to the interoperability
considerations. The relative bandwidth is then about 40 %. This is a big problem
when designing antennas.
Typical gain of antennas for DVB-T in handheld terminals is presented in figure
4.1. It is assumed that the same values can be used for DVB-H, because the
demand of the signal power is lower in DVB-H than DVB-T on account of the
MPE-FEC in DVB-H. The low frequencies (large wavelength) make the antennas
electrically small and lead to high losses and low overall efficiency.
Power gain / dB
2
0
-2
-4
-6
-8
-10
-12
Antenna power gain specification
470 510 550 590 630 670 710
Frequency / MHz
Figure 4.1. Specified gain for handheld DVB-T terminals.
30

The size of the antenna is another very important characteristic that has been on
consideration during the design. The maximum size of the ground plane that has
been used is 110*60 mm. This size has been chosen to be about the same size as
today’s mobile terminals with a screen large enough to watch TV. The height
above the ground plane is flexible, but the total volume of the antenna is always
kept as small as possible.
To avoid making gain measurements the whole time during the design of different
antennas a 6 dB return loss criterion was used, this is often used when designing
antennas for mobile terminals. To verify the antenna performance, gain
measurement was made in the end of the antenna design.
For covering the whole DVB-H band with a normal size terminal, the total
efficiency must be deteriorated. In a transmitting antenna, the resistive and
matching losses must be minimized because of the valuable battery power and
excessive heat producing. But in a receiver antenna, lower efficiency, can be
accepted if the signal level is high enough compared to the noise level.
31

4.3 Folded dipole antenna
Figure 4.2. Dipole antenna.
The first antenna type that was realized was the folded dipole antenna, shown in
figure 4.2. This type of antenna was chosen because it is simple to build and is
primarily used in the same frequency bands as DVB-T is transmitted. With 600
MHz as centre frequency it can be decided that the length of the dipole antenna
should be 235 mm. The antenna impedance should be 50 Ω, to transform the
antenna impedance to this a balun was constructed by a coaxial cable. With 600
MHz as centre frequency and a coaxial cable, with known material parameter
(α=0.66), the balun should be 165 mm. For equations see figure 4.3. The coaxial
cable was connected with the SMA outlet as shown in figure 4.3.
Figure 4.3. Dipole antenna dimensions.
32

4.4 PIFA
To verify the balun a resistance equivalent to the antenna resistance was
connected between the ends of the balun, and then the SMA to the network
analyser. When the characteristic of the balun was satisfactory it was connected to
the antenna, the return loss graph is presented in figure 4.4. The antenna was now
ready to use.
Figure 4.4. Dipole antenna, return loss graph.
After constructing a large dipole antenna the PIFA was the first attempt to build
an embedded DVB-H antenna.
The PIFA has a ground plane that is created by double side copper laminate with a
size of 110*60 mm 2 . To connect the two sides with each other copper tape was
placed over the edges. The antenna element is placed on a 6 mm thick substrate
and the dimension of the antenna element is 35*50 mm 2 . The length and width
have been tested to get as good performance as possible. A large number of
different patterns and substrates of the antenna element have also been tested to
improve the performance. With the pattern shown in figure 4.5 best return loss
was achieved.
33

Figure 4.5. PIFA antenna.
The bandwidth of the PIFA is increasing with the height above the ground plane.
Therefore the height of the antenna is the most important parameter for a PIFA to
cover the whole DVB-H band. The total height for the PIFA is 15 mm to get
required bandwidth (see return loss graph in figure 4.6).
Though the purpose is to develop an antenna for handheld devices we decided to
not continue with PIFA because it needs a too large height above ground plane to
fit inside a terminal.
Figure 4.6. PIFA return loss graph.
34

4.5 Folded-Patch
With the PIFA-antenna the most critical measure is the height above the ground
plane. Therefore the antenna element was flipped up and placed at the same height
as the ground plane (see figure 4.7). After a lot of testing the antenna fulfilled the
demand to have at least a 6 dB return loss in the frequency range 470-702 MHz,
the return loss graph is shown in figure 4.8.
The ground plane for this antenna measures 62*51mm. The antenna element is
folded around a 1mm plastic substrate and measures 36*51mm.
The critical measure in this antenna is the distance between the antenna and the
ground plane, which in this case is 19mm. This distance is critical because the
antenna is a ground free antenna and the antenna element cannot be placed closer
than 19 mm to the ground plane. The antenna bandwidth is increased with the
distance. Another important measure is the width of the antenna, which is 51mm.
If the width is decreased the resonance frequency is increased. A lot of different
antenna patterns were tried, the one in the picture gave the best result.
The location of the feeding point is another important factor for the characteristic
of the antenna. To get the wished performance of the antenna it has to be fed on a
strip line as the picture shows.
Figure 4.7a. Folded-patch, front side.
35

Figure 4.7b. Folded-patch, back side.
Figure 4.8. Return loss graph for the folded-patch.
The folded-patch 1 antenna is too big to fit inside a mobile terminal. After a lot of
failed attempts to make it smaller and still have a minimum return loss of six dB a
smaller similar antenna was designed (see figure 4.9). The return loss graph is
presented in figure 4.10. However the antenna is still big and it cannot be placed
above a ground plane, because it is a ground free antenna. A possible solution for
this problem in practice is to have a construction that slides out from the ground
plane when the antenna should be used. Another solution to this problem could be
to place the antenna in a support for the terminal that is folded out so the terminal
can stand on a table.
36

Figure 4.9a. Folded-patch 2, front side.
4.9b. Folded-patch 2, back side.
37

4.6 Loop antenna
Figure 4.10. Return loss graph of the folded-patch 2.
When the work with the wideband folded-patch antenna was finished we read
Perlos patent application SE0403110-0 about a loop antenna. This loop antenna is
a narrowband antenna that is tunable over the whole DVB-H frequency band. The
work with the loop antennas in section 4.6 is based on this patent.
The concept consists of a loop antenna that is tuned by two variable capacitance
diodes (see figure 4.11). An analogue voltage controls the diodes, for simplicity
the same voltage that controls the tuner in the DVB-H receiver. The inductance
between the two diodes prevents the signal from leaking into the control circuit. If
there in some way leaks signal through the inductance the capacitance will ground
this signal.
To be able to feed at the same point as the ground point, which is preferable to get
a balanced antenna, the length of the feeding loop can be changed to get the
desired performance.
38

Figure 4.11. Loop antenna schematic (measures in mm).
The antenna in figure 4.12 is a loop antenna that is designed by Perlos. Its
diameter is 30 mm and is made by a 3mm wide metal band. This antenna has a
bandwidth of 11 MHz at –6 dB return loss, see figure 4.13 for return loss graph.
Figure 4.12. Perlos loop antenna.
39

Figure 4.13. Perlos loop antenna return loss graph.
To test what difference the width of the antenna metal band has, return loss
measurements were also made on another loop antenna (see figure 4.14) with the
same diameter but only a 0.5 mm wide copper wire, see figure 4.15 for the return
loss graph.
Figure 4.14. Wire loop antenna.
40

Figure 4.15. Wire loop antenna return loss graph.
The good result from the measurement with the loop antenna made by thin wire
did it interesting to make a loop antenna by copper tape. So the last loop antenna
that was designed is the one in figure 4.16. The antenna is controlled by two
variable capacitance diodes that can be varied between 2.6-6.7 pF, the variable
capacitance diodes used has part number SMW1763. The return loss graph for the
loop antenna made by copper tape is presented in figure 4.17. The reason why this
is the most interesting design is that it is the most likely loop antenna to realize in
a real cell phone, because it is very thin and can be made by flex film or by PCB.
41

Figure 4.16. Loop antenna.
Figure 4.17. Loop antenna return loss graph.
The experience from designing loop antennas for DVB-H is that the shape of the
antenna is flexible and does not affect the performance. The size of the loop
antenna can be changed but this affects the efficiency, a smaller antenna gives
worse efficiency and the other way around.
An advantage with the loop antenna is that it responds to the magnetic field
component of an electromagnetic wave. Therefore, the risk of interference
between the loop antenna and another antenna in the mobile device may be
relatively low (Perlos patent application SE0403110-0 includes the advantages of
42

using an H-field antenna together with an E-field antenna). Another advantage
with this solution is the narrow bandwidth that gives a function like a filter, which
also lowers the risk for interference.
Disadvantages with this antenna are the complexity with the control signal and
that it cannot be placed over a ground plane in a cell phone. This means that the
loop antenna must be placed on an external flap to have good performance.
Another disadvantage is that the control signal must be very precise to tune in
exactly right frequency, because the bandwidth is not much wider than the
channel.
4.7 Switched Monopole
Today nobody wants an external antenna on a mobile phone. Therefore this
embedded prototype antenna was designed. With today’s small mobile phones it
is hard to achieve required bandwidth for DVB-H with an embedded antenna. The
solution to this problem is a switched monopole antenna along one of the sides of
a mobile handset. The idea to this solution came from Perlos patent SE525069.
The antenna is controlled by two switches/multiplexers so different matching
circuits can be connected, a model with three matching circuits is presented in
figure 4.18.
Figure 4.18. Model of switched monopole concept.
The idea of this antenna type is that some different matching circuits together can
cover the whole DVB-H frequency band as shown in figure 4.19 The number of
matching circuits needed depends on the antenna requirements, but to be sure that
the requirements will be fulfilled four matching circuits have been used for all
switched monopoles in this chapter.
43

Return Loss /dB
0
-2
-4
-6
-8
-10
-12
-14
-16
Matching networks
450 480 510 540 570 600 630 660 690 720
Frequency /MHz
44
Matching network 1
Matching network 2
Matching network 3
Matching network 4
Figure 4.19. Example of four different matching circuits covering the DVB-H
frequency band.
The first switched monopole has no switches so soldering was needed to be able
to switch between the matching circuits. This first prototype was built just to
verify that this concept was possible for a DVB-H antenna, a picture of the
antenna can be seen in figure 4.20
Figure 4.20. Switched monopole without RF switches.
The ground plane used for all of the switched monopole prototypes is 110*60 mm
and the antenna element is 70*10 mm. The dimensions of the antenna element are
very important parameters for the antenna characteristic, the length affects the
resonance frequency and the width of the element affects the bandwidth of the

antenna. The dimension of the antenna element was chosen so it fits in a normal
handheld device. If it had been possible with a wider antenna element it had
maybe been enough with two or three matching networks instead. The distance
between the antenna element and the ground plane is an important parameter for
the antenna characteristic, the longer the distance the better the performance, both
deeper and wider return loss graph. All switched monopole prototypes have been
built with a distance between ground plane and the antenna element of 3 mm.
After designing the four different matching circuits, as shown in the schematic in
figure 4.21 with component values according to table 4.1, the return loss was
measured. The result of the return loss measurement is presented in figure 4.22.
Figure 4.21. Schematic for four matching circuits for the switched monopole
concept.
Table 4.1. Value of components for the three different switched monopole
prototypes.
Circuit 1 Circuit 2 Circuit 3 Circuit 4
without RF
switches
Switched
monopole 1
Switched
monopole 2
C1
L1
C2
/pF /nH /pF /nH /pF /nH /pF /nH
12 19.5 10 15 8 11.2 7 7.5
45
L2
12 12 10 10 7 8.2 6 4.7
10 15 10 8.2 7 3.9 6 0
C3
L3
C4
L4

Figure 4.22a. Return loss graph with matching circuit 1 and 2 for switched
monopole without switches.
Figure 4.22b. Return loss graph with matching circuit 3 and 4 for switched
monopole without switches.
46

The result of the return loss measurement was satisfactory and it was decided that
instead of this prototype a switched monopole with two RF switches should be
built.
To verify that the switch worked correctly and to make it possible to find out how
one switch affects the characteristic of the antenna a prototype with just one
switch was designed. The RF switch is connected between the matching circuits
and the antenna element and between the matching circuits and the antenna feed it
was needed to solder to switch between the different matching circuits. This
switched monopole prototype is called switched monopole 1 from now on.
The antenna that is called switched monopole 2 is exactly the same as switched
monopole 1 besides that it has a switch before the matching circuit and it has
different values of the matching components.
The RF switch that is used for these two prototypes is an antenna switch from
Peregrine (PE4268), other switches have been tested but without satisfactory
result. The used switches need three digital control signals that could be
withdrawn from an I2C-bus that the chipset provides. The I2C-bus can be
connected to the expander MAX7313 circuit that can be programmed to provide
the desired control signals. An alternative to this solution could be if the chipset
could deliver these signals directly.
The switched monopole 1 and 2 are built with a ground plane and an antenna
element with the same size as the switched monopole described above and with
the same distance between ground plane and antenna element. In figure 4.23 a
picture is shown of the switched monopole 2.
47

Figure 4.23. Switched monopole 2.
The design of the matching circuits is presented in figure 4.21 and the values of
the components are presented in table 4.1 for both prototypes.
The return loss graphs for the different matching circuits for switching monopole
1 are presented below.
48

Figure 4.24. Return loss graph for matching circuit 1 for switched monopole 1.
Figure 4.25. Return loss graph for matching circuit 2 for switched monopole 1.
49

Figure 4.26. Return loss graph for matching circuit 3 for switched monopole 1.
Figure 4.27. Return loss graph for matching circuit 4 for switched monopole 1.
50

The result of the measurement of the return loss graph for switched monopole 2 is
presented in the following four graphs.
Figure 4.28. Return loss graph for matching circuit 1 for switched monopole 2.
51

Figure 4.29. Return loss graph for matching circuit 2 for switched monopole 2.
Figure 4.30. Return loss graph for matching circuit 3 for switched monopole 2.
52

Figure 4.31. Return loss graph for matching circuit 4 for switched monopole 2.
The result from the return loss graphs for the different switched monopole
antennas is satisfactory. There are some differences for example the varying level
of the return loss graphs for the different prototypes, which depends on the loss in
the switches. It is only the anechoic chamber measurement that can show how
much the switches affect the performance of the antenna and show if the prototype
is good enough even though there are losses in the switches.
A switched dipole has also been tested, with the same design as the switched
monopole but with an extra antenna element along the other side of the ground
plane connected to the ground plane. The test result showed that the switched
dipole has somewhat better performance than the switched monopole. But the
conclusion of the test is that the antenna element connected to the ground just
enlarges the ground plane and the small increase of performance does not
motivate the increase of cost and size it will mean.
53

5 Measurements of antenna solution
Now when some different antenna prototypes have been built it is time to find out
how good they really are. Here you can read about how the measurements were
done, how accurate the measurements are and what performance the different
antenna prototypes have.
5.1 Anechoic chamber measurement
This chapter presents measurement results of our prototypes. The purposes are to
find out the efficiency and power gain for each prototype. The measurements are
made in Perlos 3D near field chamber.
5.1.1 Test set-up
All measurements presented in this chapter are made in an anechoic chamber.
Figure 5.1 shows a schematic view of the chamber. The antenna is mounted in the
centre of the chamber and is rotated in phi direction while the probes are sliding in
theta axis. Measurements are made for every tenth degree for both phi and theta.
5.1.2 Measurements
Figure 5.1. Schematic view of Perlos anechoic chamber.
Unfortunately Perlos chamber is not adapted for measurements at frequencies
lower than 700 MHz, therefore we determine the efficiency and the power gain
from a comparison with a reference antenna. All measurements presented are
rawdata.
As reference antennas we used four dipole antennas that we built ourselves, in
figure 5.2 one of the antennas is shown. Each of them was made for a 60 MHz
54

frequency band, the first from 470 to 530 MHz and so on, this characteristic was
achieved by changing the length of the antenna. In figure 5.3 the return loss graph
of the reference antenna matched for the frequency band 530-590 MHz is shown.
The other three reference antennas look the same and have the same return loss
for their respective centre frequency.
Figure 5.2. Reference dipole antenna.
Figure 5.3. Reference dipole antenna return loss graph.
55

Figure 5.4. Radiation pattern for Reference antenna, frequency=560 MHz,
Theta=90°, Phi=0°-350°, A=Phi polarization, B= Theta polarization.
Figure 5.5. Radiation pattern for Reference antenna, frequency=560 MHz,
Theta=0°-350°, Phi=0°, A=Phi polarization, B= Theta polarization.
56

Figure 5.6. Radiation pattern for Reference antenna, frequency=560 MHz,
Theta=0°-350°, Phi=90°, A=Phi polarization, B= Theta polarization.
To determine the power gain for our antennas we must measure the radiated
signal in the whole sphere. The maximum value of all these values is equivalent to
2.15 dBi power gain for an ideal dipole, because our reference antennas are not
ideal we estimated the maximum power gain to 1.6 dBi. Then the maximum
absorbed signal for our antennas can be compared with this value for respective
frequency (see equation 5.1).
G=A-B+1.6 (5.1)
G=Antenna power gain in dBi.
A=Received signal strength in our prototype.
B=Received signal strength in the reference antenna.
To find out the efficiency for our antennas we must calculate TRP, total radiated
power for both the reference antenna and our prototype.
2π
π
⎧
⎫
Prad = B0
∫ ⎨∫
f ( θ ) ⋅ sin θ ⋅ dθ
⎬dφ
0 ⎩ 0
⎭
Numerical equation:
(5.2)
P
rad
⎛ π ⎞⎛
2π
⎞
= B0⎜
⎟⎜
⎟
⎝ N ⎠⎝
M ⎠
M
⎡
∑ ⎢∑
⎣
N
j=
1 i=
1
F(
θ φ
i,
j
) sin
θ
i
⎤
⎥
⎦
57
(5.3)

Since the measurements for the prototypes and the reference antennas are made
for the same number of points in the sphere we can compare TRP directly to
calculate the efficiency (see equation 5.4) [28].
Prad,
prototype TRPprototype
e 0 =
⋅ 0.
9 =
⋅ 0.
9
(5.4)
P
TRP
rad,
reference.
antenna
reference.
antenna
Where 0.9 is the estimated efficiency for our reference antenna.
To calculate the power gain and efficiency for our prototypes, we have to measure
and calculate received signal strength and TRP for all four antennas. To get more
accurate calculations all measurements was made three times and a mean value
was calculated (see table 5.1).
Table 5.1. Reference antenna values for calculation of gain and efficiency.
Frequency /MHz Received signal
strength /dBm
TRP /mW
470 -47.9 0.00351
490 -47.3 0.00426
510 -47.0 0.00473
530 -45.9 0.00491
550 -44.7 0.00644
570 -44.0 0.00795
590 -43.7 0.00972
610 -42.8 0.01167
630 -42.4 0.01156
650 -43.5 0.0092
670 -43.2 0.00836
690 -43.4 0.00868
710 -44.5 0.00791
58

5.1.3 Measurement result
In this chapter the results of the anechoic chamber measurement for the different
prototypes are presented. The results are discussed in chapter 7, Conclusions.
Power gain / dB
2
0
-2
-4
-6
-8
-10
-12
Folded-patch 1 vs. specification
470 510 550 590 630 670 710
Frequency / MHz
59
Specification
Figure 5.7. Gain for the folded-patch 1 versus specification.
Folded-patch 1
Table 5.2. Folded-patch 1 gain and efficiency results.
Folded patch 1
Frequency / MHz Gain / dB Efficiency / %
470 -3.72 19.4
530 -2.72 40.5
590 -1.04 47.2
650 -2.68 41.2
710 -4.68 27.3

Figure 5.8. Radiation pattern for Folded-patch 1, frequency=590 MHz,
Theta=90°, Phi=0°-350°, A=Theta polarization, B=Phi polarization.
Figure 5.9. Radiation pattern for Folded-patch 1, frequency=590 MHz, Theta=0°-
350°, Phi=0°, A=Theta polarization, B=Phi polarization.
60

Figure 5.10. Radiation pattern for Folded-patch 1, frequency=590 MHz,
Theta=90°-350°, Phi=0°, A=Theta polarization, B=Phi polarization.
Power gain / dB
2
0
-2
-4
-6
-8
-10
-12
Loop antenna vs specification
470 510 550 590 630 670 710
Frequency / MHz
61
Specification
470-478MHz
530-538MHz
590-598MHz
650-658MHz
702-710MHz
Figure 5.11. Gain for five different capacitances in the loop antenna versus
specification.

Table 5.3. Loop antenna, gain and efficiency results.
Loop antenna
Frequency / MHz Gain / dB Efficiency / %
470 -5.2 15.2
472 -4.3 17.5
474 -3.4 21.0
476 -4.6 18.1
478 -4.9 15.6
530 -4.8 15.6
532 -3.7 18.2
534 -3.1 22.5
536 -3.6 19.6
538 -4.5 18.7
590 -4.1 18.5
592 -3.2 20.9
594 -2.4 26.8
596 -2.9 23.0
598 -3.7 22.1
650 -3.8 24.8
652 -3.0 29.4
654 -1.6 33.6
656 -2.1 30.8
658 -2.5 28.4
702 -2.7 29.4
704 -2.0 34.8
706 -1.2 38.6
708 -1.6 35.4
710 -2.2 33.1
62

Figure 5.12. Radiation pattern for Loop antenna, frequency=640 MHz, Theta=90°,
Phi=0°-350°, A=Theta polarization, B=Phi polarization.
Figure 5.13. Radiation pattern for Loop antenna, frequency=640 MHz, Theta=0°-
350°, Phi=0°, A=Theta polarization, B=Phi polarization.
63

Figure 5.14. Radiation pattern for Loop antenna, frequency=640 MHz, Theta=0°-
350°, Phi=90°, A=Phi polarization, B=Theta polarization.
Power gain / dB
2
0
-2
-4
-6
-8
-10
-12
Switched monopole 1 vs specification
470 510 550 590 630 670 710
Frequency / MHz
64
Specification
Circuit 1
Circuit 2
Circuit 3
Circuit 4
Figure 5.15. Gain for the four different matching networks of switched monopole
1 versus specification.

Table 5.4. Switched monopole 1, gain and efficiency results.
Switched monopole 1
Frequency / MHz Gain / dB Efficiency / %
470 -5.12 10.0
490 -4.86 11.7
510 -4.22 18.8
530 -4.57 14.7
550 -4.14 19.7
570 -2.74 24.9
590 -0.54 25.0
610 0.58 30.1
630 0.00 34.3
650 0.10 43.1
670 -1.18 57.5
690 -1.59 54.8
710 -1.97 50.2
Figure 5.16. Radiation pattern for Switched monopole 1, frequency=510 MHz,
Theta=90°, Phi=0°-350°, A=Phi polarization, B= Theta polarization.
65

Figure 5.17. Radiation pattern for Switched monopole 1, frequency=510 MHz,
Theta=0°-350°, Phi=0°, A=Phi polarization, B= Theta polarization.
Figure 5.18. Radiation pattern for Switched monopole 1, frequency=510 MHz,
Theta=0°-350°, Phi=90°, A=Phi polarization, B= Theta polarization.
66

Power gain / dB
2
0
-2
-4
-6
-8
-10
-12
Switched monopole 2 vs specification
470 510 550 590 630 670 710
Frequency / MHz
67
Specification
Circuit 1
Circuit 2
Circuit 3
Circuit 4
Figure 5.19. Gain for the four different matching networks of switched monopole
2 versus specification.
Table 5.5. Switched monopole 2, gain and efficiency results.
Switched monopole 2
Frequency Gain Efficiency
470 -6.12 7.7
490 -5.58 9.3
510 -4.91 10.9
530 -6.22 10.4
550 -5.39 14.4
570 -3.89 18.5
590 -1.35 24.6
610 -0.59 27.3
630 -1.58 27.5
650 -1.11 35.1
670 -2.44 45.9
690 -2.90 40.9
710 -3.60 34.6

Figure 5.20. Radiation pattern for Switched monopole 2, frequency=630 MHz,
Theta=90°, Phi=0°-350°, A=Theta polarization, B=Phi polarization.
Figure 5.21. Radiation pattern for Switched monopole 2, frequency=630 MHz,
Theta=0°-350°, Phi=0°, A=Phi polarization, B=Theta polarization.
68

Figure 5.22. Radiation pattern for Switched monopole 2, frequency=630 MHz,
Theta=0°-350°, Phi=90°, A=Theta polarization, B=Phi polarization.
5.1.4 Measurement reliability
Since the anechoic chamber, where the measurements were made, was
constructed to measure frequencies above 700 MHz the correctness of the
measurements made can be discussed.
The dipole antennas that were used as reference antennas were not built with very
high precision and will therefore contribute to somewhat higher uncertainty in the
measurements. The reference dipole antennas have higher losses than an ideal
dipole, therefore the maximum measured value for the reference antennas were
estimated to 1.6 dBi instead of 2.15 dBi.
The moderating cones in the chamber are constructed to moderate frequencies
down to 500 MHz, however it cannot be certain that no standing waves appear in
the chamber when frequencies below 700 MHz are measured.
When antennas are measured in a near field chamber as the one used, the distance
between the probes and the antenna under test should be at least three times the
wavelength of the frequencies measured. This is to lower the interaction between
the probes and the antenna. This means that the distance between the probes and
the antenna under test should be close to two meters when measuring on 470 MHz
69

and about 1.3 meters when measuring on 700 MHz. This distance in the chamber
used is only about one meter. This will also increase the uncertainty of the
measurements.
The probes are designed to send frequencies down to 700 MHz and do not work
very well for lower frequencies. Since the measurements are done relatively this
should not affect the results.
All these possible error contributions give a pretty big uncertainty for the absolute
value in the measurements. However the different prototypes that have been
measured could be compared to each other with a rather high precision.
5.2 Testing with DVB-T receiver
Since DVB-H is supposed to be sent with the same base stations as DVB-T and
on the same channels one can draw the conclusion that DVB-H will be sent with
the same power as DVB-T. If DVB-H becomes successful the plan is to build
more transmitters to get better coverage. The present DVB-T base stations
transmit with 50 000 Watt ERP.
From the antenna point of view it is the same thing to receive a DVB-H signal as
a DVB-T signal. A difference between the two signals is that the DVB-H signal is
harder coded with MPE-FEC than the DVB-T signal. A DVB-H receiver will
therefore need lower received signal strength to have good reception. In other
words, if our antennas can receive and show a DVB-T signal they will also be
able to receive and show DVB-H signals.
A relevant test for the built antennas is therefore to try and receive digital TV with
them in different environments. This was done with a laptop and a DVB-T box
that was connected to the computer through a USB 2.0 port. The DVB-T box
antenna connection is matched to 75Ω and all the antennas built are matched to
50Ω. The tested antennas will need somewhat higher signal strength together with
the DVB-T box than they will with a future DVB-H receiver since this will be
matched to 50Ω.
At the moment there are five different channels transmitted in Skåne at 482, 506,
634, 794 and 818 MHz. The tests were done on 482 and 506 MHz because these
are the only channels that transmit programs free of charges.
To get an idea of how strong the DVB-T signal is the constructed dipole antenna
was connected to a spectrum analyzer and the signal strength of the different
channels were measured. Inside Perlos laboratory no signal could be found. To get
a signal the window had to be opened, and then signal strength of around –80dBm
70

was received in all five channels. The lower limit of today’s chipset is about –95
dBm, so reception should be possible
All the built antenna prototypes could receive the DVB-T signal and digital TV
could be seen on the computer as long as the antenna is placed outside.
Generally the polarization should not have any effect, but it was noticed that the
reception was not very good with the loop antenna when it was held in vertical
led, this will be further discussed in section 7, Conclusions.
71

6 Results
Now three final antenna prototypes have been designed and measured (foldedpatch,
loop antenna and switched monopole 2). In this chapter they will be
evaluated and compared to each other.
6.1 RF Performance
6.2 Design
A big difference between these three prototypes is the bandwidth. The loop
antenna covers only 1/30 of the DVB-H band, while the switched monopole 2
covers one fourth of the bandwidth and the folded-patch covers the whole band.
Different bandwidths have different advantages. The narrowband loop antenna
has the advantage of being interference tolerance against GSM 900. This is why
the loop antenna has very bad performance for all frequencies except its resonance
frequency. The antenna acts like a filter against all unwanted frequencies. Another
feature that makes the loop antenna interference tolerant is that it is an antenna
that responds to the magnetic field. The folded patch has no filter effect at all and
therefore becomes very sensitive to interference. The switched monopole 2 has
interference tolerance somewhere in between these.
All three prototypes fulfil the gain specification well. The folded-patch differs
from the other two in the sense that it has almost the same gain in the two ends of
the band while the other two antennas gain increases with the frequency.
Since the efficiency depends on the gain these two values have the same
characteristic. The folded-patch has best efficiency in the lower part and in the
middle of the band. The switched monopole 2 has the best efficiency in the higher
part of the band while the loop antenna has a more even efficiency.
The folded-patch has the radiation pattern closest to an isotropic antenna, with no
distinct zero. In the radiation pattern for the loop antenna two zeros can be seen.
The zeros for the switched monopole 2 are not as distinct as for the loop antenna.
The folded-patch and the loop antenna cannot be placed above a ground plane.
Therefore a mechanical solution has to be designed for these two antennas. This
mechanical solution that includes the antenna has to be extractable, which reduces
the design flexibility for this two antenna concepts. Both these antennas could be
manufactured out of flexible film. The antenna element of switched monopole 2 is
placed along the ground plane and can thereby be designed as an embedded
antenna. This antenna element is preferably made of sheet metal.
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6.3 Control signal
6.4 Cost
The switched monopole 2 needs the most complex control signal to work
properly. For the switches used in this prototype three digital control signals are
needed to control the switches. To control the loop antenna an analogue DC
voltage between 0.5 and 3.0 V is required. This DC voltage can be the same that
controls the VCO in the tuner. A big advantage with the folded-patch antenna is
that no control signal is required.
The manufacturing cost varies a lot between the different prototypes. The most
expensive antenna solution will probably be the switched monopole 2 since the
two switches and the expander are expensive circuits. The switches we used from
Peregrine can be bought for about $1 each and the expander costs $1.50. For this
solution three inductors and four capacitances are also required. The inductors
cost $0.02 each and the capacitors cost $0.005 a piece. Which adds up to about
$3.60 for components only. Hopefully the DVB-H chipset will be able to deliver
the needed control signal and then the expander is not needed. There are cheaper
switches on the market that are possible to use in this concept, our time limit did
not allow us to test these.
The second in line is the loop antenna, mostly because the variable capacitance
diodes are relatively expensive. One variable capacitance diode cost about $0.30.
One capacitor and one inductor are also needed for this prototype so the total
component cost adds up to about $0.60. The folded patch antenna does not need
any components. However this prototype and the loop antenna will need a slightly
more expensive mechanical solution than the switched monopole 2.
All prices are approximations and apply when one component is bought, if the
antennas were to be mass-produced the prices will be significantly lower.
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7 Conclusion
During this project the different measurements have been the major problem, and
already during our first measurement we ran into trouble. No DVB-T signal was
detected when measurements with the spectrum analyzer was done. The reason
for this is that the walls and windows attenuate the signal. The windows at Perlos
laboratory have a thin metal layer on the glass.
This means that there is no indoor coverage in Perlos laboratory in Lund and
probably not in larger parts of Skåne. For the DVB-H system to be successful
coverage inside cars, busses, trains and buildings has to be achieved. The base
stations operating today only provide full indoor coverage in the near of the base
stations. If the DVB-H system is successful more base stations are planed and full
indoor coverage will be achieved.
As you all now by now the frequencies used for the DVB-H system are 470-862
MHz. This frequency range is good in aspect of getting good coverage with few
base stations. The only drawback with these low frequencies is that the antennas
become electrically very small, and thereby inefficient. If higher frequencies had
been used more base stations had been required since higher frequencies have a
higher propagation loss.
DVB-H system can use all existing DVB-T base stations and only a handful new
base stations have to be built in the future. This is a huge economical advantage
against competing systems. Another big advantage is that it is a broadcasting
system, which means that it is spectrum efficient. That it is a broadcasting system
means that an infinite number of users can watch the same show without
occupying more bandwidth. This could be compared to the technique used today
in the 3G network where smaller shows are streamed to each user separately.
One of the reasons why shows are streamed separately is that in this way the
operators can easily control how long time each user has watched and thereby be
charged. Another reason is that the operators have a lot of unused capacity in the
3G network and want to use this to stream TV shows in.
A big difference between DVB-H and DVB-T is time slicing. This has been added
in the DVB-H standard to decrease the power consumption to a level suitable for
handheld devices. This technique has a couple of drawbacks. The first one is that
when the user likes to change channel it might take up to five seconds before the
next burst are transmitted. This means that no picture can be shown until the burst
for the chosen channel has been received. The second one is if the terminal has
bad reception during the burst time, then the terminal will not have any video to
play until the next burst is received. When this technique is used live shows will
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not be possible, there will always be some delay. This is for instance not wanted
when a live football match is transmitted.
Other notable differences between DVB-H and DVB-T are MPE-FEC and 4kmode.
These features are added to DVB-H to make the system more robust and to
make the network design more flexible. They have no major drawbacks but when
MPE-FEC is used more bits have to be sent per data bit.
The DVB-H system suits handheld terminals very well in all ways except that a
normal sized antenna for the frequencies used would be larger than the terminal
itself. The large bandwidth that the antenna has to cover is a hard problem to
solve. We have solved this problem in three different ways, with one wideband,
one switched and one tunable narrowband antenna. The different solutions fit
different kinds of terminals. Since the wideband antenna, folded-patch, is
sensitive to interference this solution fits best in devices without GSM 900, like
Ipod and other terminals with screens suitable for watching TV. From this point of
view the loop antenna is the most suitable antenna for GSM 900 terminals.
Theoretically the isolation between an H-field and an E-field antenna is much
higher than for two E-field antennas. This theory and its narrowband characteristic
are two things that make the loop antenna interference tolerant. No tests have been
done to find out which of these things that contributes most to the interference
tolerance. A lot of discussions with senior antenna designers about the H- and Efield
theory have been conducted. None of these designers could say for sure that
this theory has any effect in the real case. If the folded patch should be used in a
GSM 900 terminal a good filter on the DVB-H chipset is required. As an example,
if the maximum allowed input level of the DVB-H chipset is –28 dBm the total
attenuation (isolation + filter) must be at least 61 dB (since a GSM 900 terminal
transmits with a peak value of 33 dBm). The requirement of the filter depends on
the antenna used since the isolation between the GSM 900 antenna and the DVB-
H antenna will differ.
If the mobile manufacturers desire an embedded antenna the only suitable solution
would be the switched monopole 2.This is the major advantage with this solution
compared to the other two that needs an extension. Customers today are used to
embedded antennas and do not prefer an external solution that easily breaks. If an
external solution is chosen anyway it could be combined as a support for the
terminal to be able to stand on a table or another smart mechanical solution.
Regardless of which antenna that is selected an important thing is the placement
of the antenna element. It has to be placed so that the antenna characteristics are
changed as little as possible when the user holds the terminal in different ways.
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The only thing that could be read out about the antenna performance from the
specification is the power gain requirement for a handheld DVB-T antenna.
Though the requirements of the DVB-H antennas certainly not will be higher than
for DVB-T antennas, these are reasonable limits for our design. However the gain
itself does not say much about the antenna performance for a handheld terminal
since an isotropic radiation pattern is desired. This is why we have chosen to
present both gain, efficiency and radiation pattern. When these three things are
presented it is easier to draw conclusions about the antennas RF performance. The
gain requirement is not very hard to achieve but to get good efficiency is hard.
This is a consequence of electrically small antennas, which all DVB-H antennas
must be to take place in a handheld device. For an electrically small antenna it is
the ground plane that contributes most to the radiation. This means that it is easier
to achieve good efficiency with a large terminal.
Our prototypes fulfilled the gain specification with large margin. Therefore the
antennas could not be separated in RF performance from the gain measurement.
From the efficiency measurement it could be seen that the folded-patch has a bit
higher values than the other prototypes but not so much that any solution can be
excluded. From a gain and efficiency perspective the folded-patch is slightly
better than the other two prototypes.
In a report from EICTA it is claimed that generally no polarisation discrimination
can be expected [31]. However, polarisation discrimination was found during our
DVB-T box measurement, the most sensitive prototype was the loop antenna.
When watching TV with the loop antenna the reception was good when the
antenna was held in vertical led but when the antenna was turned to horizontal led
the reception was bad. After some studies in the subject, the conclusion is that for
these low frequencies the polarisation is not much changed when the signal is
reflected. Therefore antenna designers cannot assume that the income signal has
different polarisations. From the radiation patterns and the DVB-T box
measurement it can be seen that the folded-patch is least sensitive to polarisation
and the loop antenna most sensitive.
Another important thing to discuss is the different control signals the antennas
need. Today it is not common with tunable antennas, but we think that it will be
more common in the near future. More and more antennas are included in the
mobile phones that take up much space. A solution for this problem could be to
use an antenna for more than one application, and then a controllable antenna
could be used. An example is that the switched monopole 2, with one extra
matching network can be used as FM antenna. The control signals available from
the chipsets today are an I2C signal and the VCO voltage. In the future it might be
possible to get more adapted signals to control the antenna. For an example it
would be easier if the DVB-H chipset could deliver the three control signals
needed to control the switches in switched monopole 2.
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There are many advantages with tunable antennas, but one big drawback for the
manufactures is the extra cost the circuits brings. The cost is one of the most
important aspects whether the antenna is to be realized or not. It is up to the
manufacturer to decide if the advantages a tunable antenna has is worth the extra
cost.
The three prototypes designed and measured in this thesis have very different
characteristics. Here below the different prototypes will be summarized.
Folded-patch
Advantages
• Good RF performance
• Simple and cheap design
• No control signal needed
Disadvantages
• Large antenna that has to be extended
• Bad interference tolerance
Loop antenna
Advantages
• Good RF performance
• High interference tolerance (filter function)
• Simple analogue control signal
Disadvantages
• Has to be extended
• Expensive variable capacitance diodes needed
• Polarisation sensitive
Switched monopole 2
Advantages
• Good RF performance
• Embedded antenna
• Possible to use same antenna for DVB-H and FM radio
Disadvantages
• Expensive components
• Complex control signal
• Losses in RF switches
It is impossible to say that one antenna is better than another because they have
different advantages and suit different terminals. If we were to choose a favourite
it would be the switched monopole 2 because this is the only antenna that could
be embedded and we are willing to pay the extra cost that this results in.
Below follows a list of demands for a DVB-H antenna:
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• Frequency range 470-862 MHz, 470-702 MHz together with GSM 900
transmitter.
• Bandwidth 392 MHz (58.9 %), 232 MHz (39.6 %) together with GSM 900
transmitter.
• Channel bandwidth 5, 6, 7 or 8 MHz.
• Minimum power gain –10 dBi at 474 MHz linearly increasing to –5 dBi at
858 MHz.
• 50 Ω impedance matching.
• As omni directional radiation pattern as possible.
• Polarisation problem can be an issue.
• A filter is needed on the DVB-H chipset input to block GSM 900 signal
and a LNA is preferable. This is not an antenna issue but as high isolation
against GSM 900 as possible is wanted.
• Low efficiency will be tolerated due to the electrically small antennas.
• The DVB-H chipset sets the sensitivity level, today’s chipset have a level
of about –95 dBm.
We still have some prototypes to evaluate. The most interesting is to replace the
switches and the matching circuits with a balun and variable capacitance diodes in
the switch monopole 2. This way the antenna could be controlled by an analogue
control voltage and no expensive switches have to be used.
We planned to do isolation measurements of the different prototypes but we did
not have enough time for this. These are important measurements that have to be
done to be able to decide the filter characteristic.
To be able to verify and to get some more reliable measurement results it would
have been interesting to do measurements in a larger chamber suitable for DVB-H
frequencies.
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8 References
[1] Schiller, Jochen - Mobile Communications, Addison Wesley, 2003
[2] DVB – History of the DVB Project
http://www.dvb.org/
[3] Almgren, Hanna and Vestin, Johanna - Scalable Services Distributed over
DAB and DVB-T from a Receiver Point of View, Mar 2002.
[4] Teracom
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[5] Orthogonal Frequency Division Multiplexing, Intel, 2004.
[6] Reimers, Ulrich – DVB - The Family of International Standards for Digital
Video Broadcasting, Springer-Verlag Berlin Heidelberg, 2005.
[7] Molisch, Andreas F. - Wireless digital communication
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[8] Intini, Aníbal Luis - Orthogonal Frequency Division Multiplexing for Wireless
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[9] 4i2i
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[11] Arjona Andres - Internet Protocol Datacasting
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[13] Quinnell, Richard A - Digital video goes mobile
Test & Measurement World, Mar 2005
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[14] Herrero, Carlos and Vuorimaa, Petri - Delivery of Digital Television to
Handheld Devices, Telecommunications Software and Multimedia Laboratory,
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[16] DVB Document A080, Apr 2004.
[17] ETSI TR 102 377 V1.1.1 (2005-02).
[18] ETSI EN 300 744 V1.5.1 (2004-06).
[19] The missing link between 3G and DVB-H
S-DMB/ MAESTRO Project, Jan 2005
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[23] Ericsson news archieve
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Helsinki University of technology, 2005
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[27] Compact Integrated Antennas, Freescale semiconductor, Nov 2004
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John Wiley & Sons, Inc., 1997.
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[29] Gardiol, Fred – Microstrip circuits, John Wiley & Sons Inc, 1994
[30] Pekowsky, Stuart and Maalej, Khaled - DVB-H architecture for mobile
communications systems, Apr 2005
[31] Mobile and portable DVB-T radio access interface specification, EICTA, jan
2004
[32] K. Fujimoto, J.R. James - Mobile Antenna Systems Handbook, Artech house,
INC, 2001
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