Abstract:An algorithm for modulation recognition of multiple quadrature amplitude modulation signals based on constellation recovery was proposed. Firstly, parameters of the carrier frequency and signal to noise ratio were estimated from its spectrum. According to the baud rate and the symbol timing, the baud rate sampling was finished. Then a non-data-aided carrier frequency offset estimation method was used to mitigate the effect of frequency offset and phase offset in constellation recovery. Finally, the modulation type was recognized by the average likelihood ratio test method. Simulation results demonstrate that the proposed algorithm has a better recognition performance when comparing with the amplitudebased maximum likelihood algorithm.