New phase-shifting technique for group-type unidirectional transducers used in surface-acoustic-wave filters

The letter reports a novel method of phase shifting useful in the group type of unidirectional transducers used for the design of low-loss SAW filters. This technique utilises the thin-film capacitance present between the newly described configuration of the feed-electrode layers as an essential element of the required phase shifter. The stray capacitance existing between the feed electrodes is used to advantage. The theoretical and experimental results of one of the filters fabricated are presented.