A patch antenna-based strain sensor forstructural health monitoring

摘要

A passive strain sensor was investigated using patch antennas. For early damage detection in structuresdue to external loads, reliable strain information is necessary. A noninvasive method of measuring strainusing a patch antenna was investigated to overcome the limitations of existing strain sensing technologies.The metal patch antenna was made on a thin sheet of low-loss polymer with a ground plane on theopposite side. When fed with RF signals, the patch antenna radiates at its resonant frequency. Theresonant frequency of the patch antenna varies with its dimensions. Strain-induced change in thedimensions results in a shift in the resonant frequency. A single-frequency antenna, designed andsimulated using the Sonnet simulation tool, has a resonant frequency corresponding to its length, so theantenna is sensitive only to the length-direction strain yet insensitive to the width-direction strain. Effectof strain on frequency shift and its sensitivity to strain were calculated. The antenna was fabricated usingconventional micromachining techniques. Effects of strain on resonant frequency were verifiedexperimentally and in good agreement with simulated results.