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A multiple branch predetection combining diversity receiver technique using pulse-envelope modulation of the transmitted signal is described. The receiver branches use the "STAR" scheme of multiple heterodyning of the received signal with itself to eliminate all exponential modulation components imparted by the transmission medium. Each branch can be shown to be mathematically equivalent to a simple square-law detector. A modulation scheme using low-bit-rate (50 kHz) companded delta modulation is proposed which provides a reasonable output signal-to-noise ratio (30-40 dB). The convenience of received signal gain control before pulse regeneration and the possible application of conjugate phase retransmission could make this technique useful.
Date of Publication: Aug. 1973