Surface acoustic wave spectrum analyzer

Abstract

A surface acoustic wave (SAW) device configured to operate as a spectrum analyzer, and having an array of input transducers disposed on a substrate in such positions as to produce a focused beam of acoustic energy at a focal arc, each position on the arc being representative of an input signal frequency. Output transducers produce electrical signals corresponding to the energy received at successive segments of the focal arc. The disclosed device includes various combinations of input transducer array improvements, some of which are to provide amplitude weighting of the input array, including aperture width weighting, capacitive weighting, resistive weighting, series-parallel weighting, and source withdrawal weighting. Another improvement in input array configuration eliminates close or overlapping electrodes of opposite polarities and thereby reduces parasitic capacitance and acoustic radiation between electrode elements. The use of curved input transducer fingers improves operation of the transducers as point sources. Other important improvements include the use of acoustic transducers before to transmit the focused output energy from the focal line to conventional output transducers, thereby improving frequency resolution, and the use of electromagnetic waveguides to transmit energy from output transducers located on the focal line.