SURFACE ACOUSTIC WAVE BANDPASS FILTER

摘要

The invention described is a surface acoustic wave (SAW) bandpass filter which has a lower insertion loss than conventional SAW bandpass filters. The filter comprises a piezoelectric substrate for propagating a surface acoustic wave, an input transducer formed on the substrate and an output transducer also formed on the substrate and having the same structure as the input transducer. The input transducer has a pair of interdigital electrodes consisting of several electrode fingers for exciting a surface acoustic wave in response to an electrical signal applied thereto. The output transducer develops this surface acoustic wave into a filtered electrical signal. The input and output transducers are so arranged that the distance between them is greater than < IMG > but less than < IMG > where n is a positive integer and is the pitch between the centres of adjacent electrode fingers.