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| | Abstract | | This paper describes a newly developed stepped-frequency type directional borehole radar system using a network analyzer. Through careful antenna design, we achieved to install a circular dipole array directive antenna in the compact radar sonde with a diameter of 57 mm operating across 5-500 MHz frequency band. All the associated surface electronics for the radar system is fit into a small carrying case. Data from MEMS sensors in the radar sonde can be used to compensate for the rotation and inclination of the sonde, and this enables us to locate reflection points in 3-D space correctly. All the data acquired by the radar sonde were sent to the processing electronics via an optical link, and the data was updated in real time. Our field testing confirmed that system accuracy for determining arrival directions was 2 to 9 degrees between 30 and 180 MHz in wet soil. We demonstrated 3-D location of a buried cylindrical conducting object, set 2 m from the radar in wet soil. After system calibration and signal processing, we were able to estimate the reflection point position with an averaged accuracy of 34 cm. |
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