A Semicircle Bow-Tie Antenna for Subsurface Radar Applications in Civil Engineering

A modified bow-tie antenna consisting of two semicircle flares fed by a tapered microstrip line is described. Such design allows avoiding separate impedance transformers and baluns that are often poorly matched over the wide frequency band of operation resulting in considerable late-time ringing. The tapered microstrip line using one of the antenna flares as ground plane is used to transform 50 Ohm impedance of the feeding cable to the antenna impedance of around 100 Ohm. The antenna performance was tested experimentally using a concrete member made of heavy density concrete with a metal rod inserted near its center. For the sake of comparison, two other antennas designed for the same frequency band, namely tapered-slot Vivaldi antenna and conventional bow-tie antenna with impedance transformer have been tested in the same scenario.