On the cross-terms in LPPs

This paper studies the effects of cross-terms in the local polynomial periodograms (LPP) by defining and examining the cross local polynomial periodogram (CLPP) and the time-frequency correlative coefficients (TFCC). Our observations show that the cross-terms of signal components can be ignored if they do not intersect and the window length used in the LPP is sufficient. In addition, the TFCC is useful for the analysis of time-frequency coherency between LFM signals and gives us a parametric measure on the amount of the cross-terms in the LPP.