A Modified Compact UWB Directional Bow-Tie Antenna for Underwater GPR

In this letter, a modified compact ultrawideband directional bow-tie antenna is designed and used for underwater ground-penetrating radar measurement. The antenna features a compact size of 89 mm × 89 mm × 50 mm, achieved through the use of a crescent-shaped, double-layer patch structure and a cylindrical reflective cavity with grooves. In addition, a novel electromagnetic wave-absorbed medium is presented and filled within the reflective cavity, improving the time-domain performance of the antenna. The assembled antenna was measured in an artificial lake. The measurement results show that the proposed antenna has a wide operating band of 157 MHz to 600 MHz, and a gain of 2.76 dBi to 7.77 dBi in the main-lobe direction. Furthermore, a field radar experiment is also conducted in the lake. The radar image shows a clear target response, indicating that the antenna can be used well for underwater detection.