幅相调制信号的星座图恢复与调制方式识别

针对幅相调制信号的调制方式识别问题，提出一种基于星座图恢复的算法。该算法估计信号载频及信噪比等参数，并依据波特率和符号定时完成对接收信号的波特率采样；采用一种非数据辅助载频偏差估计方法，以消除载频偏差及相位偏移对星座图恢复的影响；利用平均似然比检测的方法，完成幅相调制信号调制方式的识别。仿真结果表明，与仅考虑信号幅值分布的极大似然算法相比，该算法具有识别性能更优。
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 amplitude based maximum likelihood algorithm. 