The Study On Clutter Suppression And Imaging Method Of Ultra Wideband Through-the-wall Radar

Through-the-wall radar is a system that uses electromagnetic waves to detect the scene behind the wall.It inverts the information of the scene and target behind the wall according to the reflection and scattering of electromagnetic waves at the interface between the wall and the air to actualize the detection and location of targets behind the wall.Due to its high resolution,strong penetrability and anti-interference ability,UWB radar has been widely used in military and civilian applications and has a good development prospect.The conventional through-wall radar model assumes that the antenna array is parallel to the wall.However,this condition cannot be guaranteed in some special scenarios.The inclination between the antenna array and the wall will cause difficulties in wall clutter suppression,and the target will also be biased shift.In addition,conventional BP imaging algorithm has the drawback of high sidelobe energy.This paper has carried out related research on the above issues,the specific contents are as follows:(1)Aiming at the problem that the target is offset and the wall clutter is difficult to mitigate caused by the tilted antenna array,this paper proposes the idea of delay correction to correct the transmission and reception timing of each antenna array's time domain echo signal to virtual measurement line parallel to the wall,which makes it have the same characteristics as the antenna array parallel to the wall model,facilitating subsequent imaging processing.In order to improve the accuracy of singular value decomposition,the original echo signal is processed by Jacobi singular value decomposition to obtain singular terms with better orthogonality,and subspace projection is used to suppress the singular terms which characterize the wall.The simulation results show that the echo signals of each channel after delay correction receive the wall echo at almost the same time,the target is corrected to the proper position,and the wall clutter is completely suppressed.And the imaging result based on Jacobi singular value decomposition has higher target clutter ratio than the traditional singular value decomposition imaging results,obtain better imaging effect.(2)In the standard BP algorithm,the imaging result after coherent superposition of each pixel point contains the interference of other points in addition to the response of the point,which results in a larger sidelobe energy in the imaging result.To solve this problem,a cross-correlation BP imaging algorithm that uses the correlation between the echoes of each channel to increase the contrast of the target and noise energy is proposed.Multiplying the the amplitudes of the channels in pairs without overlapping before the superposition which increases the energy contrast between the target and the noise.The simulation results show that the proposed CBP imaging algorithm reduces the integrated sidelobe ratio of the imaging results to a certain extent compared with the standard BP algorithm,and suppresses the noise energy,which greatly improves the imaging quality.(3)Introduce the process of using LabVIEW to test the clutter suppression method of wall-through radar wall.Input the echo signal and Gaussian white noise to be processed on the front panel,and call MATLAB Script node to realize the wall clutter suppression and target correction based on jacobi singular value decomposition proposed in this paper.The time domain map of the echo signal and imaging image are displayed on the LabVIEW interface to complete the development of the test software.