Research On Estimation Of Unknown Wall Parameter In Ultra-wide-band Through-wall Radar

Ultra-wide-band through-the-wall radar is a nondestructive detection radar rising in recent years.It can use electromagnetic waves to penetration cob walls,wood walls,brick walls,concrete and other nonmetallic walls,and detect and image the inner structure of human body or buildings behind walls.For the excellent penetration capability and high down-range resolution,through－the-wall detection based on ultra-wide-band is of great demand for military and civil applications.In the application of UWB through-the-wall radar,the velocity of electromagnetic wave propagating be reduced when the electromagnetic wave pass through the wall.At the same time,the phenomena of refraction,reflection,delay and signal attenuation will occur,which will affect the imaging quality.Most imaging algorithms assume that the wall parameters are known and then image the target,but in practical applications,the wall parameters cannot be known in advance.The accuracy of the unknown wall parameters directly affects the location of the target and the imaging quality.In addition,the diversity of the wall will also have an impact on this,so it is very necessary to estimate the parameters of wall.To resolve the problem above-mentioned,the main content of this paper is summarized as follow.(1)The electromagnetic propagation properties of UWB through-the-wall radar are studied.In the process of ultra-wide-band signal penetrating the wall,time delay and signal attenuation will occur.At the same time,the influence of the center frequency of the transmitted signal,the relative dielectric constant and the thickness of the wall on the received signal are discussed.(2)A method based on transmission coefficient for unknown wall parameters estimation is proposed.Via the calculation for transmission coefficient of electromagnetic wave propagating through the wall,the amplitude attenuation coefficient is deduced.Then,combined with the nonlinear relationship between propagation delay and wall parameters,the unknown wall parameters can be accurately obtained by Newton iterative method.Finally,the error analysis and comparison of the results show that the proposed method is feasible and superior to estimate unknown wall parameters.(3)The parameter estimation of multistory wall is studied.At present,many wall estimation algorithms are only suitable for single-layer wall parameter estimation,but in practical application,the wall is basically multistory wall,so it is more meaningful to study the multistory wall parameter estimation.The application of sparse decomposition method to wall parameter estimation is studied.First,sparse decomposition method is used to estimate the time delay atoms and reflection coefficients of reflected signals,and calculate the reflection amplitude of the interface.Then the wall parameters are estimated layer by layer according to the propagation model.Finally,the superiority of the method is verified by the error analysis and comparison.