A Study on a Measurement Method for Wave Absorbers Using a Metal-plate Lens Antenna

Electronic toll collection (ETC) in Japan is often introduced to tollgates where the space is narrow. For accurate DSRD communication, it is important to reduce unwanted reflection from concrete structures including that for ETC at tollgates or tunnels which are surrounded by concrete structures. A microwave absorber is used to reduce the wave reflection at the canopy of the tollgate. It is, however, necessary to use a lift truck to measure absorption performance of the absorber at the canopy which is very troublesome. To simplify the operation, the authors proposed the new measurement system that uses a metal-plate lens antenna installed on the ground. This makes the measurement operation safer as lift trucks are not needed.