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ABSTRACT: Filters are an integral part of any communication or electronic
warfare system. They are used extensively in electronic countermeasures,
instrumentation and satellite communication. There are numerous types of
filters that can be used at microwave frequencies, nevertheless the main
drawback of a waveguide filter is its large size at lower microwave
frequencies. For this reason, the one structure that can provide smaller
size is the evanescent mode filter. A complete design procedure is
presented for an evanescent mode filter, which does not require special
tuning techniques. This method covers the case of a rectangular
waveguide structure, which is composed of an air-filled waveguide
containing a number of dielectric inserts operating in the normal
propagative mode, while air-filled sections are evanescent. The
technique consists of finding a scattering description of all the filter
sections and junctions. This search stems from an exhaustive
electromagnetic study of the field quantities and requires modal
analysis methods. A genetic algorithm optimisation has been developed
and included, and rules are provided to assist designers in their search
for the best results. Examples of waveguide filters with various orders
are simulated for a given cross section, permittivity and step size. The
filters' section lengths are evaluated such that the best response
according to designer specifications is achieved
Circuits and Systems, 2000. Proceedings. ISCAS 2000 Geneva. The 2000 IEEE International Symposium on; 02/2000
