Research On High Performance And Miniaturized Planar Microwave Filter

Microwave filters have the property of frequency-selective transmission, which enable them to transmit energy in one or more passbands and to attenuate energy in one or more stopbands. Thus, microwave filter is one of the most important components in microwave/RF circuits and systems. Emerging wireless communication applications continue to challenge microwave/RF filters with even more stringent requirement—higher performance, smaller size and lower cost. This dissertation gives a detail research on design theory and technology of high performance and miniaturized microwave planar bandpass filters, including transversal filter, extend doublet filter and dual band filter. It is summarized as follows:Firstly, systematic research on the design theory of new transversal resonator bandpass filter, especially on the characteristic of special two-order transversal filter-open loop dual-mode filter. Based on the research, two novel fully canonical three-order transversal bandpass fiters using planar technology are proposed. Compared with the latest reported three-order transversal filter which using cavity and microstrip mixed technology, these filters have the advantages of much smaller sizes and flexible transmission zeros arrangement.Secondly, a novel E-type quarter-wavelength resonator is proposed for the design of dual band bandpass filter. By combining hook feed line and pseudo-interdigital coupling scheme, the E-type resonator dual band filter not only has controllable bandwidths and very compact size, but also has very good high stopband and low stopband rejection levels.Thirdly, we apply the theory of transversal resonator filter to the design of dual band filter. The proposed transversal dual band filter is comprised of two different resonators and, it can realize fully canonical coupling scheme in both passbands. It has many advantages such as controllable bandwidths, compact size, flexible transmission zeros arrangement and good frequency selectivity.Fourthly, two miniaturized dual band filters with controllable bandwidths are proposed. One of them uses resonator-embedded quarter-wavelength resonator, in which the higher passband is based on embedded resonator and the lower passband is based on quarter-wavelength resonator. Controllable bandwidths, very compact size and good frequency selectivity can be achieved by this technology. The other one is comprised of triple-mode resonator and half wavelength resonator and, it is also a transversal dual-band filter. It can achieve controllable bandwidths, compact size and good frequency selectivity.Fifthly, a extend doublet microstrip bandpass filter using novel resonator- embedded open loop dual-mode resonator is proposed. Due to the merits of the proposed resonator, source/load coupling can be introduced into the filter. Thus, a fully canonical extend doublet filter is realized for the first time. Compared with the latest reported extend doublet filter, it has the advantages of much smaller size and the capability to realize fully canonical coupling scheme.Sixthly, a summary of the whole dissertation is given, and future research topics are suggested.