Synthesis Of Cross-coupled Filters And Corresponding Diagnosis & Tuning

With phenomenal growth in the telecommunication industry in recent years, especially in the filed of wireless communication, more stringent filter characteristics are demanded, such as higher close-to-band rejections, asymmetric rejections specifications, lower in-band insertion loss and equalized in-band groupdelay, the cross coupled filters are able to accomplish these specifications by introducing the prescribed transmission and/or equalization zeros.The thesis is mainly devoted to the synthesis theory of cross coupled filters with generalized Chebyshev filtering functions and the means for realizing in practical microwave circuits, the corresponding diagnosis and tuning methods are presented as well. Firstly, N-degree transversal array network model is given, thus corresponding admittance function could be evaluated, By the contrast between the admittance function and that evaluated via transmission function of filter, the"extended"coupling matrix could be extracted. Then a further series of similarity transforms may be applied to reconfigure the coupling matrix to other more convenient forms to be realized. Secondly, we discussed the cross-coupled filter topology, with an emphasis on the CT/CQ topology which is mostly adopted in practical design. Thirdly, the diagnosis and tuning methods of microwave-filters are studied, mainly the modified Cauchy method. Examples are demonstrated for supporting this method. Finally, the means for realizing in the waveguide, microstrip line and coaxial cavity structure is discussed. Simulation results are demonstrated, thus the feasibility and practicality of the means are both verified.