Design of cross-coupled quarter-wave SIR filters with plural transmission zeros

Abstract

A cross-coupled bandpass filter is designed with quarter-wave stepped-impedance resonators (SIRS) on a single circuit plane. The entire circuit has not only a compact area since half-sized SIRS are used, but also a wide upper stopband because the first spurious peak occurs at a frequency much higher than the passband. Plural transmission zeros on both sides of the passband can be realized by non-adjacent couplings and tapped input/output. Two-port Z-parameters are employed to formulate the analysis of the transmission zeros. An experimental filter is fabricated and measured to validate the design.