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

4.1 Through-Wall TOA Estimation 53
Antenna looking dirrection
180˚
90˚
270˚
�
0˚
Z
Wall
TX
� �
Target
a) b)
Fig. 4.1.8: a) The example of horn antenna footprint. b) Bistatic through-wall
model.
where w1 = footprint(φ1) and w2 = footprint(φ2). The whole implementation of
the antenna footprint to the SAR imaging increase the computation complexity
only negligibly.
4.1.7 Measurements Results
The influence of the wall on imaging results is illustrated on two experiments.
For testing of the proposed algorithm the 2D SAR measurements were chosen.
The measurements were done with the 9 GHz M-sequence UWB radar system
[43, 116, 118] described in Section 2.1.3. Bistatic model with the double-ridged
horn antennas was used. For bistatic system the dtot has to be computed twice,
for transmitter-target flight distance and for target-receiver flight distance:
RX
� �
P 1
dtot bist = dtot T X2T + dtot T 2RX. (4.1.17)
All the preprocessing and calibration steps described in Section 2.4 were undertaken.
The irregular trolley movement was compensated, as well as antenna beam.
The migration with a simple geometrical approach described in Section 2.5.2 called
SAR imaging was used to transform time domain into the spatial domain. The
wall was compensated by the proposed algorithm.
Scenario 1 is a simple scenario, where the measured object is in parallel with
the scanned wall. The measured room was approximately 4 m × 5 m large, with
the wall thickness of about 0.2 m. The wall was made of bricks with relative
permittivity approximately εrw = 4. Distance between the centers of antennas
P 2
X