Cascade Synthesis of Selective Linear-Phase Filters

A design procedure is presented for the realization of selective linear-phase channel filters in a cascade configuration. From the transfer function which exhibits optimum maximally fiat amplitude and linear phase characteristics, synthesis is performed using symmetrical seconddegree transmission zero producing sections which contain frequencyinvariant reactances, and the overall network is constructed with complex conjugate symmetry. Conversion is made to lumped-element bandpass channel filters using the reactance slope parameter method. In all but very narrow bandwidths, dispersion occurs in the bandpass filter, but it is shown that by choosing a dispersive modification to the prototype, flat group-delay characteristics may be recovered in the bandpass filter.