Use of the cross time-frequency distribution for the analysis of the class of PSK signals

Phase Shift- Keying (PSK) modulation has been applied widely in most of the data communication system nowadays due to its noise immunity and bandwidth efficiency capability. Analysis of digital modulation is an important component of spectrum monitoring. Furthermore, it has been identified recently that spectrum sensing is part of the function in cognitive radio. Works on bilinear time-frequency distribution (TFD) previously does not represent the phase information of a signal and it is incapable to analyze PSK type of signals. The cross TFD method proposed overcomes this problem, and is able to analyze signal carrying phase information like the class of PSK signals. From the cross time-frequency representation (TFR), signal parameters like the subcarrier frequency, instantaneous phase and bit duration can be estimated. The choice of the window width has significant effect on the accuracy of the phase estimation as well as the frequency resolution of the Time Frequency Representation (TFR). It is shown that the cross TFD with appropriate window width can give a complete representation of a phase modulated signal.