Ultra wideband balanced fan-shaped three-transducer low-loss leaky SAW filters

Abstract

This paper presents the new ultra wideband balanced leaky SAW filters using fan-shaped IDTs with the low insertion loss, fractional bandwidth of 39-55% on 64°YX and 41°YX LiNbO3. The three-transducer structure containing one input fan-shaped IDT and two output fan-shaped IDTs with the split electrodes is used in these filters. For an efficient triple transit suppression in the wide bandpass of the filters the output IDTs were made with a different geometry: with symmetric and antisymmetric configuration of the electrodes. The constructional and topological optimization of the leaky SAW filters is provided with a computer simulation using an δ-function model. The 64 and 66 MHz leaky SAW filters have shown bandwidths of 35 and 26 MHz, insertion loss of 7-8 dB, passband ripple of less than 3 dB, shape factor of 1.35-1.47, stopband attenuation over 40 dB in a matched system. The filters are housed in the 13.3×6.5×1.8 mm SMD packages and can operate in the balanced/unbalanced system.