Study Of Printed Broadband Antenna And Dual-band Filter

Antennas have played a very important role in many microwave and millimeter wave communication systems. With the rapid development of antenna, people have proposed higher criteria in miniaturization of antenna, wide band and high gain. Since the circular-polarization antenna and dual-polarization antenna have a strong ability of anti-interference. They have a broad application in the civilian base stations and satellite communication systems. Therefore, the research and design of these antennas have been one of the research projects now. In microwave and millimeter wave communication system, filter has the important function in connecting the antenna and amplifying circuit. Its frequency-selective characteristics have a large impact on the receiving system. Multiple band-pass filters can effectively filter out interference signals and it can transfer signals in many pass bands. It can be applied to Wide band Code Division Multiple Access(WCDMA) and Wireless Local Area Network(WLAN) systems. Accordingly, the study on filters with the characteristic of high performance, miniaturization, and multi-band is also very necessary.In this paper, two novel circular-polarized antennas based on parallel resonator, dual-polarized antenna based on stepped impedance resonator and dual-pass band filter which can be used in WLAN system have all been discussed. Firstly, put two SMD oscillators across vertically. The antenna is fed by a power divider which has a phase difference of 90°. The proposed circular-polarized antenna has a feature of AR<3dB with bandwidth of 1.75~2.5 GHz(35%). Secondly, the circular-polarized antenna can be improved by adding a parasitic patch to the top of antenna. The new proposed circular-polarized antenna has a feature of AR<3dB with bandwidth of 1.1~1.7 GHz(42.8%). Thirdly, a dual-polarization antenna based in Vivaldi antenna theory which works in S-band has been designed. It has a feature of S11<-15 db with the bandwidth of 1.5~3.6GHz(82.3%). Finally, two different structures of dual-band filters have been designed thorough analysis of the micro-strip filter theory. Then, the dual-pass filter is designed with a modified dual-mode resonator with the bandwidth of 2.35~2.5 GHz as well as 5.05~5.35 GHz. In another hand, the improved SIR dual-band filer owns the bandwidth of 2.35~2.56 GHz and 5.11~5.33 GHz. They can both cover the frequency band of WLAN system(especially 2.4&5.2 GHz) and can transfer the signals effectively. In addition, some specific performances of the proposed devices above have been tested by experiments, and it shows that the experimental results agree well with the simulation results, which further proves the correctness and validity of our conclusions.