Time-Frequency representation of a Signal through Non-Stationary Multipath Fading Channel

摘要

Spectral analysis is only applicable to stationary signals and most of the real signals in many practical applications are nonstationary. Time-frequency methods are applied to analyze nonstationary signals and this paper presents different time-freqnency methods to analyze a modulated random signal through a multi-path fading channel with emphasis on time-varying power spectra. Short-time Fourier transform (STFT) divides the full time interval signal into a number of small intervals and is not useful for analyzing signal to determine frequency contents of a time varying voltage spectra. WignerVille distribution (WVD) is the most popular time-frequency energy distributions to develop time-frequency plane for estimation and detection of non-stationary process. The objective of this paper is to analyze time-frequency relationship of a non-stationary amplitude varying fading channel. In this paper, STFT and WVD are applied to the time varying non-stationary multi path fading channel to analyze timefrequency contents. The result shows that WVD provides better timefrequency relationship than that obtained by Fourier transform, and the analysis procedure will be used in future to analyze time-frequency relationship of amplitude varying non-stationary channel using Wavelet transform.