Research Of Coupling Matrix Extracting Method Of Chebyshev Bandpass Filter

This paper studies the computational method to identify key structural factors selection in electromechanical coupling research. And then an improved coupling matrix extraction method is proposed.First, the paper introduce the basic theory of the synthesis and design of conventional filters (Butterworth,Chebyshev).Secondly , the computational method to identify key structural factors is studied. According to comprehensive evaluation methods, the process to construct the index system which is applicable to the electromechanical coupling research, was confirmed. The data envelopment analysis(DEA) method and the improved analytic hierarchy process are respectively utilized to compute the objective and subjective coupling degrees respectively. Then the maximum entropy method is introduced to compute the combination coupling degrees. At last, an engineering example was given to demonstrate the methods. And the key structural factors, which affected the electricity performance of a kind of filter with coaxial resonator, are obtained.Thirdly, an improved coupling matrix extraction method was developed based on the combination of Jacobi Method and the optimization method. The method gets the initial matrix from the solutions of the Jacobian Method. Then the matrix is utilized as the initial value of the iterative optimization to obtain the accurate coupling matrix. This method has the advantages of both methods. To obtain the initial coupling matrix, experiments on coupling matrix extracting for coaxial-cavity tunable filter was designed. S parameters were measured in the experiments. Then zeros and poles were obtained. Proved by engineering experiments and analysis, the method is feasible and rational.Finally, the synthesis theory of cross coupled filters with generalized Chebyshev filtering functions was introduced. And the paper analysis the equivalent circuit model of the cross-coupled filter. the means for realizing in the microstrip line is discussed. Simulation results demonstrates that the method is feasible.