Quadrature amplitude demodulator comprising a combination of a full-wave

Abstract

In a demodulator for use in deriving demodulated signals from a modulated signal subjected to k-by-k quadrature amplitude-and-phase modulation where k is equal to 2.sup.N and N is an integer greater than unity, first and second detection signals, each having k-levels, are derived from the modulated signal by a coherent detecting circuit (21, 22, 24, 26, 28) and processed by first and second processing circuits (31, 32). Each of the first and the second processing circuits is implemented by a combination of (N-1) full-wave rectifier(s) (35) and N+2) binary detectors (34, 36-38; 42, 46-48) to produce each set of binary signals and each additional binary signal divisible into a pair of partial bit signals. Alternatively, each processing circuit is implemented by a combination of N full-wave rectifiers and first through (N+1)-th binary detectors. The first through the N-th detectors detect each set while the (N+1)-th detector, each additional binary signal. Anyway, each set serves to produce the demodulated signals while each additional binary signal, an AGC signal and an APC signal.