QAM Signal Demodulator with One and a Half Symbol Per Sample

The article discusses a new QAM signal demodulation algorithm operating at a clock speed of 1.5 sample per symbol. The demodulation algorithm implements a modified adaptive equalizer scheme that allows clock synchronization recovery and detecting a signal at a rate of 2 modulation symbols per 3 signal samples without loss of quality. The basic version of the demodulation scheme is presented in the continuous signal processing variant. In this case, the algorithm of adaptive clock synchronization recovery is used a modification of adaptive "blind" equalization. The presented algorithm can also be effectively used for block signal demodulation. In this case, a scheme is presented using the adjustment of the equalizer coefficients on the unique word and pilot symbols. The developed algorithm, in comparison with classical demodulation schemes, has a lower computational complexity and, without reducing the noise immunity, operates with an input signal sampling rate corresponding to 1.5 samples per modulation symbol. The conducted research relates to the development of receiving devices of communication systems using PAK/QAM signal modulation in their channels. The results obtained can be used in the development of demodulation schemes for satellite, radio relay and optical communication systems.