Research and Design of a TEM Horn Antenna for Urban Underground Space Detection

Based on transmission line theory, a TEM horn antenna was studied and designed to enhance low-frequency performance. After improvement, it can effectively reduces excessive reflection within the low-frequency band. Additionally, the improvements increase the main axis gain at low-frequency band. Compared to traditional TEM horn antenna, the antenna with incorporated elliptical ridge structure can effectively suppresses back lobe radiation across the entire operating frequency range and broaden the low-frequency bandwidth. Simulation results indicate that the designed antenna operates within a frequency range of 51 to 253 MHz and consistently exceed 2.8 dB in axial gain across this spectrum. With dimensions of 2500 × 1400× 2000 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>, the antenna is considered well-suited for the detection of underground spaces at depths reaching up to 30 meters.