Programable frequency acoustic wave discriminator

Claim 1

A discriminator for use in controlling the output frequency of a voltage controlled oscillator, comprising: an acoustic wave delay line and a phase sensitive detector arranged to measure the phase difference between signals applied to the delay line and signals received from the delay line and produce a signal representing such phase difference, wherein the delay line comprises a substrate capable of supporting acoustic waves, first and second transducer means arranged on the substrate and connected to the phase sensitive detector to launch and receive acoustic waves in and from the track, the second transducer means arranged on the substrate and connected to the phase sensitive detector to launch and receive acoustic waves in and from the track, the second transducer means comprising a plurality of transducers each spaced apart along the track at a different distance from the first transducer means, and each being capable of supporting oscillation at a number of harmonic frequencies, said difference in distance being less than one wavelength at the transducer means center frequency, and switch circuitry for selectively switching each of the plurality of transducers to the phase sensitive detector so that by sequential operation of said switching means the oscillator may be caused to oscillate any one of said harmonic frequencies such number being much greater than the number of second transucers.