Low-Profile, Low-Frequency, UWB Antenna for Imaging of Deeply Buried Targets

A novel ultrawideband directive antenna for ground-penetrating radar (GPR) applications is presented in this letter. The antenna is designed for operation at frequencies below 500 MHz to allow for high-depth-resolution imaging of the deeply buried targets such as buried pipes and other deep underground man-made structures such as tunnels. The antenna is formed by a pair of coupled antennas inspired by an electrically narrow very low profile (ENVELOP) antenna with differential feeding to provide a directive pattern normal to the antenna ground over a wide bandwidth. An antenna operating in the range of 140-510 MHz is designed and fabricated using the printed circuit board (PCB) substrates. The antenna is designed and optimized for operation in the proximity of a half-space soil medium to achieve efficient coupling of power from the air to the ground. The measured reflection coefficient of the antenna near concrete and wet soil covered by sand and grass is shown to be better than -9.5 dB within the specified band. The simulated realized gain of the antenna in the presence of dry soil is better than 4.9 dBi within the range of 140-510 MHz. The antenna is low-profile with a total height of 153 mm and a lateral dimension of 600 mm × 600 mm. The performance of the antenna for GPR applications is evaluated through a field measurement of a buried object in wet soil with high losses.