Application of ultrashort-pulse radar to non-destructive inspection

An ultrashort-pulse radar (USPR) has been developed for non-destructive inspection of structures, search of buried objects, and biomedical imaging. An impulse with 150 ps pulse width is used as a source for the present USPR. Since the bandwidth of the source is inverse relation to the pulse width, we can expect wide frequency range in microwave region which benefits high spatial resolution as well as time resolution. Therefore antennas for the USPR are required to provide acceptable characteristic in wide frequency band width. Non-destructive inspection for concrete structures utilizes the contrast in the dielectric properties between cement and air at cracks. In this paper, the comparison of inspected results of the concrete samples are described using three types of antennas, an open-ended rectangular waveguide antenna, a bow-tie antenna, and a log-spiral antenna.