Research And Design Of Novel Microwave And Millimeter Wave Bandpass Filters

Microwave filters are key components and indispensable in the modern wireless communication system. The performance of filter will have a great impact on the whole system. As the rapid development of wireless system, it also stimulates the demand of various filters. Recently, the filters with high performance, miniaturization, low-loss and high power capacity find a great application in the wireless system. On the other hand, as the expansion of radio spectrum as well as several advantages appear in the millimeter-wave(mm W) communication system, the center frequency of communication system in the future will develop to mm W band. This trend gives a lot space to do some further research on the mm W filter for future applications.This theme of thesis is focus on synthesizing and designing novel microwave and mm W bandpass filters. Firstly, a novel Ultra-wide band(UWB) is designed based on the microstrip/CPW coupled structure, and an improved circuit with high order notch band and wide upper stopband rejection is also discussed. Then, a rotational symmetric structure is proposed and detailed discussed. A pair of transmission zeros are obtained and locate at out-of-band, based on this, two rotational symmetric mm W bandpass filters are designed and discussed. As for the unequal terminated resistance problem which occurred in the exact design method, a detailed solution is given and discussed here.In order to solve the port transformation problem which appeared in the integration between the traditional bandpass filters and the RFICs, the balanced filter on a double-layer substrate is proposed. The slotline is also used here for high common-mode rejection. Based on these discussion, a dual-band and dual-band tunable balanced filters are designed and discussed.The mm W bandpass filters which fabricated on the substrate integrated waveguide(SIW) are also discussed in this thesis. Two types of EBG units which composed of slotline etching on the SIW transmission line are first discussed. The two units have the bandpass characteristic based on the analysis of their propagation constant. Based on this, two types of mm W bandpass filters which designed at 140 GHz and 40 GHz are proposed, the coupled resonator theory is applied for synthesis and optimization. The proposed electric coupling is also detailed discussed and a comparison with magnetic coupling is also given here.Finally, a conclusion and further discussion is given, and the proposed filters in this thesis have a high performance and could be applied to the modern wireless system..