Detection of linear chirp and non-linear chirp interferences in a spread spectrum signal by using Hough-Radon transform

The time-frequency distribution (TFD) of a spread spectrum signal looks more like a noise, and the energy distribution occupies the full two-dimensional time-frequency (TF) plane. Any jammer or interference will be well localized in the TF plane. By treating the TF plane as an image, the interference patterns can be detected by using the image analysis technique of Hough-Radon transform (HRT). Curves with mathematical equations can be easily detected by transforming the shapes into Hough domain, and searching for dominant peaks (maximum values). The co-ordinates of the dominant peaks provide the parameters of the shape. For example, in case of a straight line, the Hough domain would be the “rho, theta” space, where “rho and theta” are the parameters of a straight line. The maximum value in the rho, theta plane would correspond to the exact parmeters of the straight line. If a high resolution TFD for a spread spectrum signal is achieved, then any linear chirp or non-linear chirp interference will show up as straight lines and curves in the TF plane. By applying the HRT on the TF plane, chirp interferences can be identified. Evaluation of the proposed techniques show successful detection of both linear and hyperbolic (nonlinear) chirp interferences in spread spectrum signals even under very low SNR conditions of 0 dB. The method detects any localized interference as along as the interference pattern in the TF plane can be represented by a