STUDY OF THROUGH WALL IMAGING IN UWB RANGE FOR TARGET DETECTION

Abstract

This dissertation is concerned with the study of Ultra Wide Band Through Wall Imaging (TWI) in range of 3.95GHz to 5.85GHz. In the dissertation report, Through Wall Imaging in frequency band of 3.95GHz to 5.85GHz is studied for metallic target detection. To penetrate the wall signal must have low frequency and have wide bandwidth for greater resolution. Thus, with central frequency of 4.9GHz and bandwidth of 1.9 GHz both the condition of penetration and high resolution is satisfied. Through Wall Imaging systems detect the location or movement of persons or objects that are located on the other side of a structure such as a wall. Since the relative bandwidth of the system is 0.39 it qualifies for an UWB system as the criteria of relative bandwidth greater than 0.20 set by FCC for UWB system is satisfied. TWI setup was assembled and data were collected in frequency domain by Vector Network Analyzer. Algorithm is developed for data processing and implemented through MATLAB scripts. Target detection was done behind four types of wall, namely, plywood wall, double layer of plywood wall separated by air-gap, asbestos wall and brick wall. Results for the analyzed data clearly show the position and approximate shape of the target. Dielectric wall tends to shift the original position of the target in the image. This problem can be solved by velocity correction algorithm. The algorithm was successfully implemented on the measured data. SVD method for clutter reduction has been introduced and applied successfully on TWI data. The target was clearly detected in the radar images after the post processing of the data. Thus the system could be used in rescue and military applications.