Research On Portable Through-Wall Radar Imaging Technology

The through-wall radar has a wide range of applications in both military and civil fields,because it has the characteristics of good wall perspective and little environmental impact.And the through-wall radar has developed very fast in recent years.At the same time there also exist many problems in the technology,such as big volume,heavy weight,high power consumption,complex operation and so on.These problems limit the usage scenario of the through-wall radar in some times.So research on compact through-wall radar,namely the portable through-wall radar,is an important direction in this field.But due to limitations in hardware and environment,the imaging is not ideal.In this thesis,an effective method for the portable through-wall radar imaging is proposed,which is based on the research and analysis of the through-wall radar imaging technology.Firstly,on the basis of experiments,characteristics of the wall's dielectric parameters and the human target echo signals are studied.This is important to detect signals,identify targets,and improve imaging methods.Then,after analyzing the operating conditions of portable through-wall radar,we find that the back projection(BP)imaging algorithm is more suitable for this radar system.It has the advantages of accurate wall compensation,good noise suppression,and less strict requirements on the radar movement path.However,the computational cost of the classical BP algorithm is O(MLN).And there is a problem of slow imaging speed.So,a fast BP algorithm based on non-uniform fast Fourier transform(NUFFT)is proposed.Through selecting an appropriate window function f,the uniform sampled data is transformed into non-uniform data.This way can reduce the computational cost by reducing the amount of data.Finally,the hardware implementation and actual imaging effect of the fast BP algorithm are verified by the FPGA and the measured data.The fast BP algorithm based on non-uniform fast Fourier transform(NUFFT)can reduce the computational cost to O(M(NlogN+|logε|L)).By comparing with the simulation results of classical BP algorithm in MATLAB,it is proved that the proposed algorithm can improve the imaging speed and ensure the imaging quality.Experiments show that the fast BP algorithm can be successfully implemented on the FPGA,and the results are in good agreement with the simulation results of MATLAB under the same conditions,which indicate that the proposed algorithm has good hardware implementation.The portable through-wall radar system developed in our laboratory is used to detect the human target behind the wooden and brick walls,and the measured data is used to image by the fast BP algorithm.The results show that the target can be accurately positioned,which proves that we can achieve accurate and fast through-wall imaging by the fast BP imaging algorithm.