A Generalized Method for Modulation Period Estimation Based on Envelope Spectrum and Deconvolution

Le résumé fourni par la source

This paper proposes a generalized method for estimating the modulation period of non-cooperative signals without requiring prior knowledge of their modulation system. To achieve this, a unified mathematical model is first established that characterizes various periodically modulated signals as the convolution of a basic waveform with a periodic Dirac pulse train. Based on this model, it is theoretically derived that the signal's envelope spectrum exhibits discrete spectral lines at integer multiples of the modulation frequency, whose amplitudes are shaped by the autocorrelation of the basic waveform's spectrum. To address potential estimation ambiguities arising from unfavorable spectral line distributions, an adaptive framework is developed. This framework calculates the kurtosis of the autocorrelation of the envelope spectrum to decide whether to estimate the period directly from the envelope spectrum or via its autocorrelation waveform. Furthermore, maximum second-order cyclostationarity blind deconvolution is iteratively applied to enhance the discrete spectral lines in the envelope spectrum, thereby strengthening the periodic modulation characteristics and resolving ambiguities. Simulation results demonstrate the method's generality and effectiveness across various signal types, showing advantages in non-cooperative signal processing scenarios where the modulation scheme is unknown.

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