General extracted pole synthesis technique with applications to lowloss TE/011/ mode filters
Abstract
A novel synthesis technique is developed for twoport networks which possess finite real frequency transmission zeros. The lowpass prototype is synthesized in the form of a network with complex conjugate symmetry where the real frequency transmission zeros are extracted from both ends and realized by simple resonators separated by phase shifters. The remaining transmission zeros are realized by the central part of the filter in the form of a crosscoupled double array. This prototype is particularly suitable for designing waveguide bandpass filters and each real frequency transmission zero is independently tunable. Furthermore, in the case of the most complex transfer function with all possible types of transmission zeros, the realization requires only one type of coupling which is necessary in the important case of TE(011) cylindrical mode cavity resonators. The general synthesis technique is given and the process illustrated by a nontrivial example. Additionally, from the results of a computer program based upon the synthesis techniques, the important differences between the possible prototype forms for the same transfer function resulting from extracting the transmission zeros in different orders are cited.
 Publication:

IEEE Transactions on Microwave Theory Techniques
 Pub Date:
 September 1980
 DOI:
 10.1109/TMTT.1980.1130213
 Bibcode:
 1980ITMTT..28.1018R
 Keywords:

 Cavity Resonators;
 Computer Aided Design;
 Insertion Loss;
 Microwave Filters;
 Network Synthesis;
 Phase Shift Circuits;
 Bandpass Filters;
 Complex Variables;
 Coupled Modes;
 Cross Coupling;
 Equivalent Circuits;
 Frequency Response;
 Low Pass Filters;
 Prototypes;
 Transfer Functions;
 Electronics and Electrical Engineering