Research on asynchronous quadrature integral demodulation method for amplitude modulation signal

The accuracy of carrier recovery in the demodulation methods of amplitude modulation signal is an important factor determining the quality of demodulation. This paper proposed an asynchronous quadrature integral demodulation (AQID) method that does not require strict carrier recovery. This method used a set frequency cardinality as the integration period to multiply and integrate the amplitude modulation signal with two preset sine signals to obtain accurate carrier frequency parameter. Subsequently, the amplitude modulation signal was multiplied and integrated with the quadrature signals to accurately analyze its true amplitude. The simulation results in this paper proved that the asynchronous quadrature integral demodulation method has a wide range of selection for preset signals and high flexibility. This demodulation method has excellent demodulation quality, and the demodulation results are not affected by the phase offset of the received amplitude modulation signal. Through simulation experiments, the analysis and comparison of indicators such as similarity, total harmonic distortion, mean square error, output signal-to-noise ratio (SNR), and computational complexity of demodulation results demonstrate that AQID has excellent demodulation performance. The total harmonic distortion of the AQID output result is stable at around -26.23 dB, that is lower than the synchronous detection of -14.30 dB. The low bound of SNR for AQID is -12 dB, that is lower than the -7 dB for synchronous detection, making this method applicable in strong noise scenarios. In addition, AQID has better noise immunity performance, and the SNR of the demodulated result is improved by an average of 13.54% compared to that of synchronous detection in the 196 sets of experiments.