Coupling-matrix-based SAW filter design

This paper presents a design method for resonator-type bandpass SAW filters that results in significantly larger bandwidth than what is currently possible with traditional SAW filter synthesis approaches. Unlike traditional lattice/ladder-type SAW filters, this method employs SAW resonators of a single resonant frequency and therefore reduces the complexity of SAW filter design. The proposed coupling-matrix-based SAW resonator models allow for the realization of a custom frequency response using non-custom SAW resonators. Two different implementations, lumped element (LE) and microstrip line (ML), are demonstrated and achieve 3-dB fractional bandwidths (FBWs) of 0.197% and 0.1% while the electromechanical coupling coefficients, K_t², of the SAW resonators used are 0.132% and 0.049%, respectively.