Nonlinear surface acoustic wave PSK encoder/correlator

An improved nonlinear surface acoustic wave, phase shift key (PSK) encoder/correlator apparatus of the type which provides encoding and correlation of a pair of electrical signals of different determined frequency provided by a signal source, and which includes,

• a nondispersive surface acoustic wave delay line including, a piezoelectric substrate having a major surface, a pair of signal launching transducers disposed on the major surface, each responsive to the electrical signals from the signal source and each providing surface acoustic waves in the substrate at a frequency in dependence on a respective one of the electrical signals, the delay line further including a plurality of transducer taps disposed in an interaction region of the major surface, each providing a plurality of sensed electrical signals in response to surface acoustic waves impinging thereon in the interaction region, the sensed signals including electrical signals at the frequency of each of said acoustic waves,
• a plurality of nonlinear frequency mixer means, each responsive to the second electrical signals from a corresponding one of the transducer taps for providing signal manifestations of the sum and difference frequency of the surface acoustic waves impinging on the tap, and
• summing means, responsive to the signal manifestations from each of said nonlinear frequency mixer means, for providing a summation thereof,
• wherein the improvement comprises:
• said plurality of nonlinear mixer means each including a nonlinear transfer characteristic in each of two quadrants displaced by one hundred eighty degrees, each of said plurality of nonlinear mixer means providing the signal manifestations of the sum and difference frequency in either of said quadrants, alternatively.