IIDT type low-loss SAW filters with improved stopband rejection in the range of 1 to 2 GHz

Abstract

Interdigitated interdigital transducer (IIDT)-type surface acoustic wave (SAW) filters with suppressed sidelobes and reduced insertion losses are described. The filters are composed of multiple withdrawal-weighted IDTs in different withdrawal positions. An 878-MHz filter composed of 13 IDTs was designed by this method. This filter has a minimum insertion loss of 1.6 dB and a stopband rejection of about 30 dB. Three filters with center frequencies of 0.9 GHz, 1.5 GHz, and 1.9 GHz were fabricated using the lift-off process. Their frequency responses are almost the same, and the insertion losses are less than 3 dB.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>