Balanced wide band fan-shaped three-tranducer SAW filters with reduced insertion loss and improved frequency response

Abstract

This paper presents the new balanced SAW filters using fan-shaped IDTs with reduced insertion loss, a fractional bandwidth of 10-24% on 128°YX LiNbO3. The fan-shaped three-transducer structure containing one input IDT and two output IDTs with the split electrodes is used in these filters. The constructional and topological optimization of the SAW filters is provided with a computer simulation using an δ-function model. The 255, 305 MHz samples of the SAW filters have shown 3-dB bandwidth of 30-61 MHz, insertion loss of 5.5-7.5 dB, passband ripple of around 3 dB, shape factor of 1.28-1.5, stopband attenuation over 40 dB in a matched system. The samples were housed in the 5×5×1.35 mm SMD packages and could operate in balanced/unbalanced 50-Ω system.