Surface wave device with suppressed boundary-reflected waves

Abstract

This disclosure depicts a surface wave transmitting device having a piezoelectric surface wave propagative medium and interdigitated comb-type input and output transducers on a surface of said medium. The input transducer is responsive to a source of input signals for launching on the surface of the medium surface waves of predetermined center wavelength. The output transducer receives the surface waves from the input transducer and develops output signals. The device is improved by one of the input and output transducers having at a transducer boundary or at an internal irregularity in the transducer tooth pattern a first tooth on a first comb connected to its associated bus bar. On an opposed second comb, there is provided a second tooth collinear with the first tooth but electrically isolated from its associated bus bar. Spurious surface waves reflected from the first and second teeth of the one transducer are in canceling phase relationship due to the fact that the first tooth is electrically connected to the associated comb bus bar while said second tooth is not. The other of the input and output transducers is of sufficient width on the surface of the medium to intercept and electrically destructively combine the out-of-phase spurious waves reflected from the first and second teeth.