Research on asynchronous quadrature integral demodulation method for amplitude modulation signal

Abstract The accuracy of carrier recovery in the demodulation methods of an amplitude modulation (AM) signal is an important factor determining the quality of demodulation. This paper proposes an asynchronous quadrature integral demodulation (AQID) method that does not require strict carrier recovery. This method uses a set frequency cardinality as the integration period to multiply and integrate the AM signal with two preset sine signals to obtain accurate carrier frequency parameters. Subsequently, the AM signal is multiplied and integrated with the quadrature signals to accurately analyze its true amplitude. The simulation results presented in this paper prove that the AQID 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 AM signal. Through simulation experiments, the analysis and comparison of indicators such as similarity, total harmonic distortion, mean squared error (MSE), output signal-to-noise ratio (SNR), and the computational complexity of demodulation results demonstrate that AQID has an excellent demodulation performance. The total harmonic distortion (THD) of the AQID output result is stable at around −26.23 dB, which is lower than the synchronous detection of −14.30 dB. The low bound of the SNR for AQID is −12 dB, which 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.