Highly selective cavity based band pass filter using asymmetric double quadruplets

A compact design procedure and realization techniques of sharp rejection band pass filter with pre calculated feed position is reported in this paper. Two spatially symmetric quadruplets are used asymmetrically with space mapping technique to adjust transmission zeros for getting desired selectivity. External coupling bandwidths are analysed, calculated and plotted for different feed line widths. A set of design equation are proposed to calculate external coupling bandwidths from the physical dimensions of the feed strip. Inter resonator spacing is utilized in special way to enhance overall bandwidth of the filter.