Chapter 3: Vehicle-Mounted GPR System for Landmine Detection

34 3. Vehicle-Mounted GPR System for Landmine Detection
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Fig. 3.7: Power spectra of 100 ground reflections measured by VNA #1 (a), VNA
#2 (b), and VNA #3 (c) with offset frequency of 300 kHz for VNA #2 and 1.25
MHz for VNA #3, and an IF bandwidth of 3 kHz.
3.2.3 Antennas
Vivaldi antennas are employed in this system. It is a kind of microstrip antenna,
which possesses a wide bandwidth and a high cross-polarization ratio (Guillanton et
al., 1998). Since it can be made on a thin and lightweight circuit board, it has
advantages, for example easy to be manufactured and to be configured as an array.
For SAR-GPR, the antenna shown in Fig. 3.8(a) has been designed and
manufactured. The size is 19×20 cm, and the antennas are aligned with a spacing of
6 cm as shown in Fig. 3.8(b). Return loss of the antennas with the array
configuration is shown in Fig. 3.9.