The Study Of Dual-band Filter Used For Wireless Communication

Because the need of wireless mobile communication., WLAN(wireless local area network)and dual-band telephones become more and more popular and develop very fast. Dual-band filters play an important role in these communications systems recently. The main works of the thesis can be summarized as following:Firstly, the fundamental theory can be classified as the basic theories of the conventional filters,electromagnetism coupling and impedance transformation. In addition, the thesis elaborates the basic structures and characteristics of step-impedance, while the half-wavelength step-impedance resonator and its application in bandpass filter are emphasized, from which we can derive the theoretical foundation of designing a dual-band filter. Based on this, we can make full use of the method of the second pass band of slow-wave resonator which makes for miniaturization of dual-band filter to design the miniature dual-band band pass filter. Meanwhile, the characteristic of has be improved by the stop-band 0°feed structure. This theory can be proved by the designing of a dual-band filter.Furthermore, we can make full use of new dual-band resonator to design a dual-band filter with controllable bandwidths, which includes a two one-section microstrip open-stub. Formulas for designing fully controllable bandwidth dual-band BPF can be inferred. At the same time, a dual-band BPF which operates in 2.4GHz and 5.2GHz can be designed and simulated. And all the theoretical analysis and design procedures have been validated by Momentum full-wave simulator.