Efficient Time Delay and Doppler Stretch Estimation of Wideband Sonar Signals Using the Radon-Ambiguity Transform

摘要

A novel efficient technique based on single slice Radon-ambiguity transform (RAT) for time delay and Doppler stretch estimation is proposed in this paper. The proposed approach combines the modulus square of narrowband ambiguity function (NAF), the modulus square of wideband ambiguity function (WAF) and Radon transform to estimate multiple targets in noisy environments. The square modulus of Gaussian-LFM (GLFM) signals has high-energy centrality in the ambiguity domain. Its peaks in the NAF represent straight lines whose slopes depend on the Doppler rates of the moving targets. These lines could be effectively detected by computing the Radon transform (RAT) of the NAF for all possible angles. However, using the Radon transform is computationally intensive due to the need of interpolation. It is shown in this paper that without calculating the entire RAT, it is possible to estimate line parameters using only a single slice of the RAT i.e. using an appropriate projection of the NAF. It is demonstrated that the proposed method can successfully separate overlapping targets, efficiently. The efficiency is achieved due to FFT-based processing, use of a single slice of RAT and the use of only 1-d searches.