Surface acoustic wave memory correlator on semi-insulating GaAs

Experimental evaluation of a monolithic surface acoustic wave memory correlator fabricated on a semi-insulating GaAs wafer is reported. The correlator employed the piezoelectricity of the GaAs substrate alone without need for a ZnO overlay. A strip coupling technique was used to couple the acoustic region to the Schottky diode region which was defined by selective ion implantation. The device, with 40 wavelength long interdigital transducers, had a 3-dB bandwidth of 5 MHz. The 0.8-μs-long correlation region had 500 diodes uniformly spaced at a spatial frequency of 0.5 Rayleigh wavelengths at 300 MHz. With all ports untuned, the input-port transduction loss was 16.9 dB; an external correlation efficiency of −87 dBm was obtained.