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

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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
Page 1 and 2: Design of Antennas for Handheld DVB
Page 3 and 4: Acknowledgements This master thesis
Page 5 and 6: 4 DESIGN AND TESTING OF ANTENNA SOL
Page 7 and 8: Figure 5.2. Reference dipole antenn
Page 9 and 10: 1 Introduction The passed decade th
Page 11 and 12: 2 Background This chapter provides
Page 13 and 14: is simultaneously modulated into 10
Page 15 and 16: 2.1.3 Reed-Solomon Codes 2.1.4 DVB-
Page 17 and 18: 2.1.5 DVB-H DVB-H is the latest dev
Page 19 and 20: 2.1.5.2 Time slicing A large proble
Page 21 and 22: figure 2.5). All three elements tog
Page 23 and 24: symbols or four 2K OFDM symbols. Th
Page 25 and 26: 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: 3.3 Loop Figure 3.1. Yagi-Uda anten
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 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 79 and 80: was received in all five channels.
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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