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

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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
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Design of Antennas for Handheld DVB
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Acknowledgements This master thesis
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4 DESIGN AND TESTING OF ANTENNA SOL
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Figure 5.2. Reference dipole antenn
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1 Introduction The passed decade th
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2 Background This chapter provides
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is simultaneously modulated into 10
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2.1.3 Reed-Solomon Codes 2.1.4 DVB-
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2.1.5 DVB-H DVB-H is the latest dev
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2.1.5.2 Time slicing A large proble
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figure 2.5). All three elements tog
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symbols or four 2K OFDM symbols. Th
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2.2 Competing standards The DVB-H s
Page 27 and 28: 2.3 Antenna theory This section des
Page 29 and 30: Figure 2.9. Impedance bandwidth def
Page 31 and 32: unloaded quality factor (Q0) and th
Page 33 and 34: losses should be avoided in handhel
Page 35 and 36: 3.3 Loop Figure 3.1. Yagi-Uda anten
Page 37 and 38: PIFA Figure 3.2. Four different con
Page 39 and 40: The size of the antenna is another
Page 41 and 42: 4.4 PIFA To verify the balun a resi
Page 43 and 44: 4.5 Folded-Patch With the PIFA-ante
Page 45 and 46: Figure 4.9a. Folded-patch 2, front
Page 47 and 48: Figure 4.11. Loop antenna schematic
Page 49 and 50: Figure 4.15. Wire loop antenna retu
Page 51 and 52: using an H-field antenna together w
Page 53 and 54: antenna. The dimension of the anten
Page 55 and 56: The result of the return loss measu
Page 57 and 58: Figure 4.24. Return loss graph for
Page 59 and 60: The result of the measurement of th
Page 61 and 62: Figure 4.31. Return loss graph for
Page 63 and 64: frequency band, the first from 470
Page 65 and 66: Figure 5.6. Radiation pattern for R
Page 67 and 68: 5.1.3 Measurement result In this ch
Page 69 and 70: Figure 5.10. Radiation pattern for
Page 71 and 72: Figure 5.12. Radiation pattern for
Page 73 and 74: Table 5.4. Switched monopole 1, gai
Page 75 and 76: Power gain / dB 2 0 -2 -4 -6 -8 -10
Page 77: Figure 5.22. Radiation pattern for
Page 81 and 82: 6.3 Control signal 6.4 Cost The swi
Page 83 and 84: not be possible, there will always
Page 85 and 86: There are many advantages with tuna
Page 87 and 88: 8 References [1] Schiller, Jochen -
Page 89: [29] Gardiol, Fred - Microstrip cir
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Design of Antennas for Handheld DVB-H ... - Lunds tekniska högskola

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