New method for wideband excitation of interdigital surface-wave transducers

A new method of designing coupled resonator networks for wideband excitation of interdigital surface-wave transducers is described. The elements of the tuning network are chosen, using an optimisation computer program. The insertion loss is minimised over the bandwidth of interest. For interdigital transducers on a monolithic zinc-oxide-on-silicon structure with ¿v/v = 0.0036, a fractional bandwidth of 20% can be obtained. For a narrow-acoustic-beam interdigital transducer on a LiNbO3 halfspace with ¿v/v = 0.022, a fractional bandwidth of 40% can be obtained. The design of the coupled resonator network takes into consideration the variation of the transducer acoustic impedance with frequency.