Research On The Method Of Beam Design Of Microwave Band RFID Reader Antenna

In RFID engineering applications, the beam shape of reader antenna determines the range of identification in RFID system, which has a great impact on the system performance. Therefore, it leads to a significant engineering importance on the beam trimming design of a designed reader antenna. The main research results include:(1)Firstly, two 2.45 GHz reader antennas that have significant difference on the gain and halfpower bandwidth are designed. The corner cut microstrip patch antenna's gain is 5.55 dBi, and its half-power bandwidth of surface E and H are 93° are 92°. The gain of slot microstrip antenna is 8.62 dBi, and the half-power bandwidth of surface E and H are 67° are 70°. The 5.55 dBi antenna is processed and its return loss 11 S and pattern are tested.(2)Secondly, a method by loading periodic resonant structures to trim the antenna beam is adopted.Two periodic resonant structures of 2.45 GHz are designed,which are polarization insensitive and polarization sensitive respectively.The influence of the number of loading turns and loading direction of the resonant structure on the antenna beam is studied. The gain change of the 5.55 dBi antenna from resonant structure loading is up to 1.87 dB, and the changes of half-power bandwidth on surface E and H are 32° and 26°. Comparatively, the gain change of the 8.62 dBi antenna from resonant structure loading reaches 1.9 dB, and the changes of half-power bandwidth on surface E and H are 37° and 39°.(3)Finally, a method based on the design of reflecting plate to trim the antenna beam is introduced.The effects of four kinds of reflecting plate on antenna beam trimming design are studied respectively The gain change of the 5.55 dBi antenna from reflecting plate reaches 2.34 dB, and the changes of half-power bandwidth on surface E and H are 35° and 52°. Comparatively, The gain change of the 8.62 dBi antenna from reflecting plate reaches 1.9 dB, and the changes of half-power bandwidth on surface E and H are 25° and 16°.Three kinds of reflecting plate are processed,and the half-power bandwidth changes of the 5.55 dBi antenna from loading these reflecting plates are tested.The two methods of beam design used in this thesis can trim the antenna beam without changing the original antenna. It is very important to the engineering application of the RFID system.