CHAPTER 3 THE PROPOSED DVB-H ANTENNA
3.2 Proposed Antenna Prototype No.1
3.2.1 Numerical analysis of antenna prototype no.1
In the numerical analysis, the size of ground planes and width of the connecting plate are selected the usual dimensions of 90×50 mm2 and 15 mm, respectively, which are similar to commercial clamshell mobile phones.
Figure 3.4 shows simulated return loss versus frequency by varying α. The bandwidth of the antenna is affected by α and it is found α = 9∘yield the largest bandwidth.
The radiation patterns at 500 MHz, 650 MHz, and 780 MHz are shown in Figure 3.5, 3.6, and 3.7 respectively. For the radiation patterns at 500 MHz, 650 MHz, and 780 MHz is near-omnidirectional, which are similar to a monopole.
Figure 3.8 presents the simulated antenna gain over the DVB-H band. The antenna gain varies from 2.5 dBi to 3.6 dBi over the operating band.
Figure 3.4 Simulated return loss versus frequency by varying α
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Figure 3.5 Radiation patterns of DVB-H antenna prototype No.1 at 500 MHz, (a) x-z plane, (b) y-z plane, and (c) x-y plane.
(a) x-z plane (b) y-z plane
(c) x-y plane
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Figure 3.6 Radiation patterns of DVB-H antenna prototype No.1 at 650 MHz (a) x-z plane, (b) y-z plane, and (c) x-y plane.
(a) x-z plane (b) y-z plane
(c) x-y plane
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Figure 3.7 Radiation patterns of DVB-H antenna prototype No.1 at 780 MHz (a) x-z plane, (b) y-z plane, and (c) x-y plane.
(a) x-z plane (b) y-z plane
(c) x-y plane
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Figure 3.8 Simulated antenna gain versus frequency.
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
3.2.2 The Advantages of Antenna Prototype No.1
Compared with [2] – [6] as shown in Table 3.1, our design not only has a simple planar structure but also yields the smallest antenna area and the largest gain with small fluctuation. In [2], [3], and [4], bending a flat metal-plate into U-shaped or L-shaped structure is employed and provides a broadband operation and size reduction. [5] is constructed by a bow-tie structure, the size is 110×45 mm2 which is too large compared with pocket-size.
Table 3.1 Size, bandwidth and gain comparisons between proposed antenna prototype No.1 and other published DVB-H antennas
Antenna area
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
3.3 Proposed Antenna Prototype No.2
In this section, the antenna prototype No. 2 is proposed to improve the bandwidth of the antenna prototype No.1. To broaden No.1’s bandwidth, boundaries, a-b-c, of No.1 antenna are changed and become a curved line as shown in Figure 3.9. The curved line is described by a function: antenna, and s1 is the gap between antenna and upper ground.
Figure 3.9 The proposed DVB-H antenna prototype No.2. (The curved line C is plotted when N=18.)
3.3.1 Numerical Analysis of Antenna Prototype No.2
Figure 3.10 shows return loss versus frequency of the No.2 antenna with different N.
The result clearly indicates that the bandwidth increases with N but the incremental is saturated when N is approaching 18. Therefore, N = 18 is chosen for our design.
Figure 3.11 shows return loss versus frequency of the No.2 antenna with different g,
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
it is observed that the mutual coupling between the antenna and the upper ground plane may affect the bandwidth. Here, g is changed from 6 mm to 10 mm to find a reasonable bandwidth. It is found that g = 9 mm can provide the largest impedance bandwidth.
Figure 3.12 shows simulated return loss versus frequency by varying tilting angle β.
It is noted that the frequency response of our design does not affected by change of the tilting angle. In the figure, the titling angles are in the range of 50º - 60º, which are suitable angles for viewing DTV.
The radiation patterns at 470 MHz, 500 MHz, 550 MHz, 600 MHz, 700 MHz, and 800 MHz are shown in Figure 3.13, 3.14, 3.15, 3.16, 3.17 and 3.18 respectively. From these figures, no special distinctions are observed. The patterns are near-omnidirectional, which are similar to a monopole antenna.
Figure 3.19 presents the simulated antenna gain over the DVB-H band. The antenna gain varies from 2.18 dBi to 3.54 dBi over the operating band.
Figure 3.10 Simulated return loss versus frequency by varying N
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Figure 3.11 Simulated return loss versus frequency by varying gap width (g)
Figure 3.12 Simulated return loss versus frequency by varying tilting β.
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Figure 3.13 Radiation patterns of proposed DVB-H antenna at 470 MHz (a) x-z plane, (b) y-z plane, and (c) x-y plane.
(a) x-z plane (b) y-z plane
(c) x-y plane
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Figure 3.14 Radiation patterns of proposed DVB-H antenna at 500 MHz (a) x-z plane, (b) y-z plane, and (c) x-y plane.
(a) x-z plane (b) y-z plane
(c) x-y plane
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Figure 3.15 Radiation patterns of proposed DVB-H antenna at 550 MHz (a) x-z plane, (b) y-z plane, and (c) x-y plane.
(a) x-z plane (b) y-z plane
(c) x-y plane
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Figure 3.16 Radiation patterns of proposed DVB-H antenna at 600 MHz (a) x-z plane, (b) y-z plane, and (c) x-y plane.
(a) x-z plane (b) y-z plane
(c) x-y plane
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Figure 3.17 Radiation patterns of proposed DVB-H antenna at 700 MHz (a) x-z plane, (b) y-z plane, and (c) x-y plane.
(a) x-z plane (b) y-z plane
(c) x-y plane
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Figure 3.18 Radiation patterns of proposed DVB-H antenna at 800 MHz (a) x-z plane, (b) y-z plane, and (c) x-y plane.
(a) x-z plane (b) y-z plane
(c) x-y plane
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Table 3.2 The peak gain and average gain of the proposed antenna prototype No.2
Figure 3.19 Simulated antenna gain versus frequency
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
3.3.2 Comparison Between Simulated and Measured Results
According to the proposed antenna of the given dimensions in the last section, the proposed antenna is fabricated by using FR4 substrate. The measured and simulated antenna return losses are compared and shown in Figure 3.20. The return loss is measured by using the Agilent 8719ET Network Analyzer. The figure indicates a good agreement between the measured and simulated results. A wide impedance bandwidth 350MHz (from 450 MHz to 800 MHz) is achieved with return loss less than -10 dB.
This result shows that the proposed antenna is suitable for DVB-H receiving antenna in the UHF-band.
The measured radiation patterns at 750 MHz and 800 MHz are shown in Figure 3.21 and Figure 3.22, respectively. The near-omnidirectional patterns are obtained.
3.20 Simulated and measured return loss versus frequency
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
3.21 Measured Radiation patterns of proposed DVB-H antenna at 750 MHz (a) x-z plane, (b) y-z plane, and (c) x-y plane.
(a) x-z plane (b) y-z plane
(c) x-y plane
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
3.22 Measured radiation patterns of proposed DVB-H antenna at 800 MHz (a) x-z plane, (b) y-z plane, and (c) x-y plane.
(a) x-z plane (b) y-z plane
(c) x-y plane
CHAPTER 3 THE PROPOSED DVB-H ANTENNA
Table 3.3 Size, bandwidth and gain comparisons between our works and other published DVB-H antennas
CHAPTER 4 CONCLUSION
CHAPTER 4 CONCLUSION
In this thesis, a miniaturized DVB-H antenna is constructed by traveling-wave architecture using a bow-tie structure. To achieve DVB-H band, an antenna boundary follows a curve of of x to the power of N function . By dint of x to the power of N, frequency response is realized systematically in the design process. The measurement shows that a wide bandwidth is achieved, about 350 MHz, from 450 MHz to 800 MHz with return loss less than -10dB. The radiation characteristics of the proposed antenna were computed using Ansoft HFSS, which was expected to provide reliable information for the proposed antenna. The computed results shows that the radiation patterns are near-omnidirectional, which are similar to a monopole. The computed antenna gain varies from 2.18 to 3.54 dBi over the DVB-H band and is a reasonable value for DVB-H band.
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[30] 吳武順﹐以碎形特徵作玻璃上數位電視平面天線之設計﹐私立大同大學通訊 工程研究所碩士論文﹐中華民國九十四年十月。