Synthesis Of Microwave Filters And Diagnosis

The synthesis technique based on Chebyshev function is a great approach to improve the selectivity and performance of microwave filters.But it brings about another two problems, harder tuning and longer design peroid, which result in high costs of research and production. The key to solve these problems is diagnosis technique. In this thesis, the synthesis theory of cross coupled filters with Chebyshev filtering function and the diagnosis technique has been systematically presented as follow.1. The diagnosis technique of lossy single passband filters is presented, including extraction of the scattering parameter polynomial, diagnosis of the coupling matrix, removal and extraction of the unloaded Q value. Three microwave filters designed by synthesis technique are used to prove the correctness and effectiveness of diagnosis technique, such as a microstrip filter with one transmission zero, a filter of coaxial cavity without trasmission zeros and a microstrip filter with two trasmission zeros.Besides, the optimization process of disgnosis and tuning the lossy filters in the stage of electromagnetic design for physical dimensions is presented.2. The synthesis technique of lossy dual passband filters is presented and a dual passband filter is desidgned by this synthesis technique. Besides, the corresonding diagnosis technique is presented and some parameters about this dual passband filter are extracted, such as extraction of the scattering parameter polynomial, removal and extraction of the unloaded Q value.3. The diagnosis technique of lossy stopband filters is presented, including extraction of the scattering parameter polynomial, diagnosis of the coupling matrix, removal and extraction of the unloaded Q value.A microstrip filter and a filter of coaxial cavity are used to prove the correctness and effectiveness of the diagnosis technique.