Absolute and Noncontact Type Displacement Sensor using Transmission Line for Detecting Multiple Targets

Abstract

In this paper, we propose a noncontact and absolute type displacement sensor detecting multiple targets using standing wave on a transmission line. The standing wave is generated, when driving the transmission line by a high-frequency signal toward the targets, due to additive-synthesis from the drive-signal and the reflected signals induced by the targets. The level of the synthetic signal observed at a certain point on the transmission line, periodically changes with the frequency of the drive-signal. Namely, the observable signal level is a sinusoidal function of the frequency. Besides, the period is inverse proportional to the displacement of each target with reference to the observation point. Thereby, we propose a method to find the period by Fourier Transforming.
We have confirmed experimentally that each target can be detected individually in the displacement from 0.2m to 3.6m and the resolution of 0.5mm is feasible.