Parameter Estimation of Hybrid Linear Frequency Modulation-Sinusoidal Frequency Modulation Signal

In this letter, a novel method which employs the Radon transform (RT) and inverse Radon transform is proposed to estimate the parameters of the hybrid linear frequency modulation (LFM)-sinusoidal frequency modulation (SFM) signal. By adding a parameter called width, we extend the original RT to a three-parameter transform, which we named as extended Radon transform (ERT). Compared with the original RT, the ERT has shown more capacities, such as estimating the parameters of a strip in a plane. As the time-frequency representations (TFRs) of the hybrid LFM-SFM signal is a strip where there is a sinusoidal pattern embedded, the parameters of the signal are related to the strip; herein, we employ the ERT to estimate several parameters of the signal. With the estimated parameters values, the signal can be dechirped to be a SFM signal, whose parameters can be estimated by some existing methods. As it is based on the TFRs, the proposed method has strong robustness under low signal-to-noise ratios. Numerical results and analysis are provided to demonstrate the effectiveness of the proposed method.