Investigation On Estimating The Delay And Scaling Parameters Of Wideband Radar Targets With Mellin Transform

The radar that transmits large signal bandwidth is referred to as wideband radar.Compared with traditional narrowband radar,wideband radar has the advantages of stronger anti-interference capability,higher range resolution,higher target recognition ability and better waveform design flexibility.In the wideband scenario,the coupling between the scaling factor that represents target velocity and the time delay that represents the target range is encapsulated in the echo envelop,which makes the parameter estimation methods based on narrowband echo model unusable in accurate parameter estimation of wideband radar target.Besides,when the target size is larger than the radar resolution cell,which is common in wideband radar applications with high range resolution,different scattered points of the target can be identified,which are distributed in multiple range cells.Such target,referred to as extended target,should not be treated as point target any more,and thus the traditional point target signal processing methods are no longer valid for extended target parameter estimation.The Mellin transform theory provides new ideas for parameter estimation of wideband radar signal.Based on the property that the amplitude of the signal mellin spectrum after scaling is the same with that of the original signal,the wideband echo signal can be firstly transform to mellin domain by Mellin transform so as to achieve decoupling and estimation of scale and time delay.The potential of Mellin transform theory in parameters decoupling combined with waveform matched dictionary motivates the estimation of time delay and scale factor of wideband target,which is the focus of this paper.The main work of this paper is organized as follows:(1)In this paper,we briefly reveal the physical connotation of Wideband radar echo model and scale factor,analyze the coupling characteristics of scale factor and delay parameter and discuss two commonly used methods for parameter estimation——Wideband Ambiguity Function(WAF)and the Mellin Matched Filter(MMF).(2)A Modified Mellin Matched Filter(MMMF)based on the MMF is proposed.In this paper,we reconstruct the impulse response function of the filter with respect to the amplitude spectrum of the transmitted signal and then estimate the scale factor with the usage of this filter by mellin matched filtering of the amplitude spectrum of the echo signal.After that,an echo matched dictionary is built based on the scale estimation to estimate the time delay of the target.The simulation experiments demonstrate that the parameter estimation performance of this method is better than those of WAF and MMF.(3)The estimation performance of the Modified Mellin Matched Filter quickly tends to saturated with the increase of signal-to-noise ratio.In order to further improve the parameter estimation accuracy of wideband radar signal,a parameter estimation method based on Atomic Norm Minimization(ANM)is proposed in this paper.This method transforms the scale factor of target echo into the vector with Vandermonde structure by utilizing the Direct Mellin Transform(DMT).Then ANM theory is applied to the estimation of target scale factor and an echo matched dictionary is built in the time domain to estimate the time delay of the target.Simulation experiments show that the estimation error of this method decreases as the signal-to-noise ratio increases.Besides the estimation performance of this method is better than those of WAF,MMF and MMMF in high signal-to-noise ratio environments.