Microwave acoustic delay lines

The established technology for making evaporated thin film piezoelectric transducers has made the construction of delay lines at microwave frequencies possible. Thin films of CdS on sapphire delay media have been used to make c.w. and pulsed delay lines from 1–11GHz, with delays from 1–14μs operating at 77°K and 300°K. The performance of some of these lines is described. The parameters governing the choice of delay media, transducer material and electrode structure are discussed and the importance of careful electrical matching of transducer to generator is emphasised.