IF extraction of multicomponent radar signals based on time-frequency gradient image

The estimation of multicomponent radar signals with overlapped instantaneous frequencies (IFs) in low SNR environments has been a challenging research topic. This paper proposes an IF estimation algorithm for spectrally overlapped radar signals which contain continuous and stepped IF laws. Firstly, we design a gradient image via the time-frequency distribution, based on which two ratio images are derived for detecting the IF segments of continuous and stepped radar components, respectively. Secondly, a graph to link the detected IF segments is constructed, and a Markov random field model is defined on the constructed graph. The final IF estimation process is transformed into the extraction of the best graph labeling. Numerical results are provided to demonstrate the robustness and efficiency of the proposed algorithm.