Research On Estimation Method Of Wall Parameters In Through-the-Wall Radar

Through-the-wall radar(TWR) can detect,identify,locate and track objects within a certain range behind obstacles.Due to the signal distortion induced by the wave propagation through the wall,the target images can be blurred and displaced from their true locations in practical TWR situations.If the wall constitutive parameters such as the relative permittivity,thickness and conductivity are precisely known,the wave propagation effects inside the wall can be compensated.Therefore,estimating unknown wall parameters is typically important for the application of TWR.Based on the wall echo signal model of the frequency domain and time domain,this thesis proposed two methods for estimation of wall parameters.The main contents of this thesis are as follows:(1)The through-the-wall radar system is introduced,and the algorithm of Orthogonal Matching Pursuit(OMP)is explained.Then,the time-delay-only estimation(TDOE)method for estimating the relative permittivity,thickness and conductivity of the wall is described in detail,which adopts a hybrid bistatic-monostatic measurement configuration.(2)Aiming at the wall echo signal model of the frequency domain,the OMP sparse reconstruction method for wall parameters estimation is proposed,which utilizes the OMP algorithm to perform the time delay estimation for each bistatic antenna separation.Then the proposed method utilizes the TDOE strategy with hybrid bistatic-monostatic measurement configuration to retrieve the wall parameters.Compared with the existing algorithm Estimating Signal Parameter via Rotational Invariance Technique(ESPRIT),the proposed algorithm can provide the time delay estimation with higher accuracy.Numerical simulation and experimental results have shown that the proposed estimation method is capable of providing the estimation of wall parameters with more accuracy and robustness.(3)Aiming at the wall echo signal model of the time domain,the sparse blind deconvolution method for wall parameters estimation is proposed,which utilizes the sparse blind deconvolution technique to simultaneously retrieve the reflectivity function and the transmitted pulse,and retrieve the time delay of echoes backscattered from the wall for each bistatic pair.Then the proposed method utilizes the TDOE strategy with hybrid bistatic-monostatic measurement configuration to retrieve the wall parameters.The proposed algorithm can retrieve the time delays without prior knowledge of the transmitted wavelet,which avoids the needed calibration reference measurement using the large metallic plate.The effectiveness and robustness of the proposed wall estimation method are demonstrated by applying it to the simulated data.