A Communications Detector With a Signal-Synthesized Reference

A detector in which the reference is derived from the incoming signal by a form of waveform synthesis utilizing positive feedback is capable of demodulating a variety of types of transmission, including single-sideband and double-sideband (carrierless) waves. With single-sideband transmissions the system permits the detection of weak signals without the problem of stray pickup from the reference oscillator and displays an inherent rate-of-change limiting action against impulse-type noise. With double-sideband waves (with or without carrier) it makes full use of the sideband energy in the two halves of the signal spectrum and maintains its effectiveness against impulse-type interference. With any type of AM transmission having correlated upper and lower sidebands it removes much of the distortion associated with selective fading.