Abstract
In the Parametric Acoustic Receiving Array (PARRAY), a low-frequency acoustic wave modulates a locally generated high-frequency carrier wave. The information in the low-frequency signal wave then appears as low-level, modulation side bands of the carrier. The function of the receiver electronics is to suppress the high-level carrier while simultaneously amplifying the low level near side-band signals. A band elimination processor has been developed that is capable of detecting signals with carrier to side-band ratios approaching 180 dB. Cascaded crystal filters and low-noise amplifiers provide the high order to carrier suppression. Additional circuitry is incorporated to permit independent observation of the upper and lower side bands. The band elimination processor is described in detail and test data for side-band signals 40 Hz–4 kHz from a 65-kHz carrier are presented. [This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Naval Electronic Systems Command under Contract NO0039-76-C-0231.]
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