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Investigation of choke-ring structures for ground-penetrating radar

For common GPR antennas such as dipoles, shielding, such as with a metallic cavity, is an attractive way to isolate the antenna from the above-ground environment and reduce unwanted coupling and emissions into the air. However, currents induced on the shield by the antenna can travel around the shield and re-radiate, creating unwanted signal paths and offsetting these benefits. This work establishes the viability of choke-ring structures in reducing these surface currents through shaping of the radiation pattern and demonstrates that good bandwidth and time-domain performance may be achieved through the use of resistive, rather than perfectly metallic, surfaces.