The use of wavelets to identify frequency hopped signals

Digital signal processing is used in the interception of digital communication signals. Due to the inherent security features, frequency hopped signals (FH) are widely used in both military and commercial communication applications. The interception of FH signals can be addressed in several ways. In this work we use the instantaneous correlation function (ICF) to represent non-stationary signals. We relate the wavelet transform of the ICF surface of a signal to its Wigner-Ville distribution (WVD). The signals can be observed in the scale surfaces of the wavelet domain. An energy analysis is applied to the surfaces (in the wavelet domain) to identify the scale of the FH signal and to estimate the hop frequency. The FH signals can also be identified by inspecting the pattern of the scales of a multiple-hop-observation interval. If all hop frequencies are within one wavelet scale, then the FH signal can be identified by a set of distinct hop frequencies.