Multiband And Broadband Microwave Filter Synthesis Technology Research

(?) With the muti-band filters and wideband filters playing a more and more important role in wireless communication systems, it is necessary to find an effective way to synthesis the two types of filters. This dissertation mainly researches some synthesis technologies for the muti-band filters and wideband filters. Firstly, on the basis of in depth comprehensive analysis the Chebyshev filters’synthesis theory, we propose a hybrid optimization algorithm which based on genetic algorithm and gradient algorithm for the coupling matrix elimination. Secondly, we introduce a comprehensive method to synthesis the common dual-band banpass filter. And after carefully analyzed the mutiband bandpass filters’nature of equiripple function, two methods of synthesis the multiband bandpass filters are presented. One is an analytical method, and the other is an iterative calculation method. Both methods are examples verify their accuracy. Then we summarize the synthesis theory of both single band filters and multiband filters, and develop a microwave filter design software’Qsfilter’ using MATLAB. Finally, according to the characteristics of the wideband filter, a modular design approach based on a simple microstrip unit is given. We introduced several commonly used structures to improve the wideband filters’out-band rejection level. Using these methods above, a harmonic suppression of ultra-wideband filter with narrow notched band is designed.