A Surface-Acoustic-Wave Continuously-Variable Delay Device with One Unidirectional and Two Uniform Transducers

A SAW device with a group delay time variable over a wide range has been developed. The device utilizes a unidirectional transducer arranged between two uniform transducers. The unidirectional transducer is placed much closer to one of the uniform transducers than the other. The distance between the two uniform transducers was 13 mm. The group delay time varies with the phase difference between the input signals applied to the electrodes of the unidirectional transducer. The variable region of the group delay time was more than 4 μs, and the bandwidth was 370 kHz. Moreover, negative values of the group delay time were observed.