Through-Wall Imaging With UWB Radar System - KEMT FEI TUKE

Chapter 4
Selected Research Methods
Our research was concentrated onto three main tasks. First, in Section 4.1 a
precise, efficient, and fast method of TOA estimation for through-wall scenario
was investigated. Second, in Section 4.2 easy to handle, fast and practical method
for measurements of wall parameters with UWB radar, that is required for precise
TOA estimation was developed. Third, in Section 4.3 a method for highlighting
of inner and outer building contours scanned from the outside by utilization of
image processing algorithms is presented. In Section 4.4, the performance of basic
migration methods was compared for through-wall scenario and several practical
measurement scenarios measured with M-sequence UWB radar system are shown.
4.1 Through-Wall TOA Estimation
Precise TOA estimation is a basic step of standard migration methods for object
imaging from SAR measurements. In this section, an effective computational
method of the TOA for through-wall model is presented, published by the author
in [1]. The conventional method that uses constant velocity model produces errors
in object shape and position estimation [141,4,3]. Computation of the TOA (corresponding
to the true flight distance) for three layer model requires the complex
minimization algorithm. The proposed method transforms three layer (air-wallair)
model to an equivalent two layer (air-wall) model with lower computation
complexity and the same precision. It uses iterative solution of well defined minimization
problem. Moreover, conveniently selected initial conditions of iteration
process can further decrease computational complexity of the method. The proposed
method provides more precise TOA estimation than the conventional one
and is less complex than three layer methods. Therefore, it is suitable for implementation
on realtime hardware. The method performance is demonstrated by
processing of real 2D SAR data acquired by through-wall M-sequence UWB radar
system.
41