System to maximize the return signal of ground-penetrating radars
We examine a ground-penetrating radar system that uses two antennas with their boresight direction maintained at or near the Brewster angle for the air-soil interface. For signals going to and returning from the buried target, this arrangement minimizes reflections from the air-soil interface for TM waves and can be used for both ground-based and aircraft-mounted systems. A major problem associated with reliable detection of mines is the weak return signal from the target. This system maximizes signal return from the target by minimizing all reflections except the desired signal reflection from the target. We analyzed some soil samples to measure their complex permittivity versus frequency. The real part of the complex permittivity ranged from 3 to 8 times that of free space, thus, the Brewster angle is between 60 and 70.5 degrees. For relatively dry soil and for damp soil, we present calculations of transmission loss versus frequency, due to reflection and absorption, from transmitter to receiver for both TM and TE waves. ©2003 Copyright SPIE - The International Society for Optical Engineering.
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