Recovery of data from amplitude modulated signals with self-coherent demodulation

Abstract

A demodulation system extracts data from an input amplitude modulated signal electromagnetic wave with a signal multiplying means that has two input terminals both of which are coupled to receive the input amplitude modulated signal. An output terminal of the multiplying means provides an output signal which is the instantaneous square of the input amplitude modulated signal. A lowpass filter is coupled to the output terminal of the signal multiplying means to reject at least twice the carrier frequency 2(.omega..sub.c) and higher frequency components, and to pass the second harmonic and lower frequencies of the modulation signal 2(.omega..sub.m(max)) to provide a filtered signal that is representative of the square of the amplitude modulation of the input signal. This demodulation method approaches ideal square law detection with power measurement of the input amplitude modulated signal. The filtered signal is supplied to an analog-to-digital converter to supply a digital data output. The signal may optionally be coupled from the lowpass filter through a square root circuit.

Dependencies are inferred from the claim text.