Folded type SAW filters with minimised group delay deviation

Aiming at realising the frequency response with small group delay deviation and wide passband width, we propose miniaturised surface acoustic wave (SAW) filters having folded propagation path and employing a straight edge mirror reflector for SH-type SAWs. In a filter fabricated on a PZT substrate, the group delay deviation of less than ±15 ns and passband width of 5% were obtained at the centre frequency of 100 MHz. The experimental result and theoretical prediction were in good agreement with each other