QAM Signal Demodulation Algorithm with Minimum Sample Per Symbol Rate

The article discusses a new QAM signal demodulation algorithm based on an adaptive equalizer. The research refers to receiving devices development for communication systems, using PSK/QAM signal for channel modulation. Results can be used in the development of demodulation schemes for satellite, radio relay and optical communication systems. Adaptive clock recovery algorithm as a modification of the adaptive equalizer is presented for the “blind” equalization variant in the continuous signal processing scheme. This algorithm can also be effectively used in demodulation schemes for block-continuous signals with the equalizer coefficients adjustment using unique words and pilot symbols. The presented clock recovery algorithm has a low computational complexity corresponding to the clock rate detuning. QAM signal demodulation algorithm effectively operates at an input sampling rate of 2 samples per modulation symbol without penalty and reducing noise immunity. It is possible to develop demodulation schemes operating at an input sampling rate of 1.5 and 1 sample per modulation symbol with quality penalty.