Synthesis Theory And Realization Of Mixed Coupling Filter

A higher frequency selectivity of filter is required by modern microwave systems, in order to meet this requirement, innovations on filter theory and realizations are pursued. Therefore, the mixed coupled filter synthesis theory and design method are studied in this thesis, and a number of planar and two-layer SIW mixed coupled filters are designd.1. The synthesis theory of mixed coupled filter is introduced in this thesis, on the basis of above, the high order frequency variation characteristics of the coupling coefficient of the resonator are considered.In addtition,two kinds of gradient based on optimization algorithm for extracting coupled matrix is introduced in detail, and one of algorithm is improved,and the algorithms are realized by Matlab platform. In this thesis, two microstrip filters with high order frequency variation characteristics are fabricated and tested. The measured results and the simulation results and the theoretical results calculated by the coupling matrix are almost perfect match between the three. A total of four synthesis examples are given in this thesis, and the validity of the optimization algorithm and software performance is verified.2. The design method of the mixed filter is summarized and analyzed, and the mechanism and characteristics of the mixed coupled structures are studied, and the study is also focused on how to adjust the size of the coupled structures to meet the corresponding frequency-dependent coupling coefficient, the design method of the mixed coupled filters is introduced in detail through two examples.3. A number of planar SIW mixed coupled filters with transmission zero are designed, further more, the mixed coupled structures of some filters are used as a resonator, in case of no increase in size, the order of filters is increased, and the selectivity of the filters is improved. Finally, six filters are fabricated and tested, and the test results are in good agreement with the simulation ones.4. Three two-layer SIW mixed coupled filters are designed. The transmission zero of the two order two-layer SIW filter is generated by the design of the mixed coupled structure between the non-coplanar resonant cavities, the selectivity of the filters is improved.