Motion sensing by microwave interferometry using two electric probes

Abstract

This paper addresses the possibility of displacement measurement by microwave interferometry at an unknown reflection coefficient with the use of two electric probes mounted in a waveguide section. The aim of this paper is to show that the displacement measurement accuracy can be improved by using an interprobe distance other than its conventional value. The measurement error as a function of the interprobe distance is analyzed with the inclusion of variations of the currents of the semiconductor detectors connected to the probes from their theoretical values. Based on the results of this analysis, the interprobe distance is suggested to be one tenth of the guided operating wavelength. In comparison with the conventional interprobe distance, its suggested value offers a marked reduction in the measurement error for reflection coefficients close to unity, while for smaller ones this error remains much the same.