Comb-Shaped Slit Antipodal Vivaldi Antenna and Its Application for Detection of Void Inside Concrete Specimens

Abstract

A design of antipodal Vivaldi antenna (AVA) with high gain at low frequencies is presented in this chapter. It consists of comb-shaped slits in edges of the top and bottom radiators to lower cut-off frequency of conventional AVA and to enhance antenna gain at low frequencies. The proposed antenna has impedance bandwidth of 1.65–18 GHz, high gain at low frequencies (6.7 dB at 1.65 GHz and 9.1 dB at 2 GHz) and front-to-back ratio of 42 dB at 13.5 GHz. The capability of the proposed AVA for UWB imaging for the purpose of the detection of voids inside a concrete beam is demonstrated. Extended results of microwave imaging of voids inside concrete at different standoff distances between the proposed antenna and the surface of concrete are also provided.