Litvintsev S. Construction methods and circuit design solutions for microstrip band-pass filters

The actual scientific and technical problem of simplifying the development of microstrip bandpass filters on segments of transmission lines, and improving their selectivity and stopband expanding due to the improvement of existing methods and the development of new methods and circuit engineering solutions is solved in this dissertation. The coupling matrix as the well-known tool for filter designs has been improved. Changes in the matrix are proposed, which led to the possibility of using this matrix with various combinations of reflective and pass-through resonators. The mathematical model of mixed couplings between adjacent resonators, compatible with the coupling matrix, has been developed. In the second part another important characteristic of the BPF is taken into account—the stopband. The stopband expanding problem in combline and pseudocombline filters by using lumped-distributed mixed couplings between adjacent resonators and a new design method based on the antiresonant frequencies trajectories of the used resonators is solved. The stopband in dual-mode filters is expanded by replacing a uniform transmission line with a stepped one. The case when the resonator has all short-circuited ends is considered. Such combination can be used as a filter.