Advanced Cascaded Filter Synthesis

Advanced lowpass filtering networks comprising novel cascaded quadruplets and/or fivetuplets and/or sixtuplets are proposed in this work. Each of the new network sections realizes a single zero located at infinity and the rest can be positioned at finite frequencies thus offering increased control of the filter selectivity. The methodology derives the desired network configurations from a synthesized intermediate network based on equivalent circuits. Numerical examples of advanced lowpass networks comprising fifteen resonators are demonstrated. Furthermore, the EM implementations of two quadruplets in Combline technology are presented. Each quadruplet realizes a total of three finite frequency transmission zeros with one having all the zeros positioned below the passband and the other one above. The performances of the two quadruplet models are in good agreement with their circuit counterparts.