Development of radar antennas for the detection of voids behind tunnel liner and laboratory experiments

Ground penetrating radar antennas used for voids detection in the tunnel are almost ground-coupled, which leads to a slow detection speed, and also was greatly affected by the surrounding environment and operation factors, to improve the detection speed and reduce the effect of surrounding environment, the air-coupled antenna, Vivaldi antenna I was chosen, and a series improvement were proposed, finally two kinds of novel Vivaldi antennas were introduced, namely, Vivaldi antenna II and Vivaldi antenna III, the performance of the antennas was investigated numerically, and to test the performance of the antennas, some model detection experiments are carried out, and the detections results of Vivaldi antennas also was compared with the results of commercial antennas, the results indicate that the novel Vivaldi antennas are as good as commercial antenna, and Vivaldi antenna II and III has a better performance than Vivaldi antenna I, and Vivaldi antennas are air-coupled, the detection results will be better if there is a certain distance between the antenna and the tunnel lining, which provides feasibility for fast detection of tunnel disease.