TAILIEUCHUNG - Ultra Wideband Part 13

Tham khảo tài liệu 'ultra wideband part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 354 Ultra Wideband 2 3 4 5 6 7 8 9 10 11 12 Frequency GHz Fig. 10. Comparison between Simulated and Measured VSWR Curves of the CPW-fed PMEM Antenna The previous proposed PMEM antenna can also fed by coplanar waveguide CPW in view of UWB applications. Figure 9 illustrates the configuration of the proposed CPW fed PMEM antenna Abed 2008 with the optimal parameters where an FR4 substrate with relative permittivity of and thickness of is used. The CPW fed PMEM antenna with the optimal geometrical parameters was fabricated. Measured and simulated VSWR Voltage Standing Wave Ratio are shown in figure 10. The measured bandwidth defined by VSWR 2 of the proposed antenna with a feed gap of is from 3GHz to which covers the entire UWB band. The far field 2D radiation patterns for the proposed CPW PMEM antenna are also carried out at three frequencies. Figures 11. a and 11. b show the radiation pattern atazimuthal and elevation planes respectively. As it can be seen from the figures omnidirectional patterns can be observed for the H plane. These patterns are comparable to those reported for a conventional dipole antenna. It is very important to note that at the higher frequency there is an obvious deviation from the omnidirectional shape in the H plane radiation patterns. Also the E plane patterns have large back lobes at low frequency and with increasing frequency they become smaller splitting into many minor ones. For the antenna gain it is found that the proposed microstrip fed PMEM antenna has a simulated maximum gain which varies between dBi and dBi within the UWB band. By comparison with the microstrip fed PMEM antenna the CPW fed PMEM antenna presents a less gain inside the UWB band with a peak gain of dBi at the frequency GHz. Design and characterization of microstrip UWB antennas 355 -10 - -20 - -30 - -40 - -40 - -30 - -20 - -10 - 180 ------f GHz 0 f GHz f GHz Azimuthal pattern H-plane 270 a 0 - -10 - -20 - -30

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