Small-And Large-Scale Strain Sensing Using Frequency Selective Surfaces

Abstract

Frequency selective surfaces (FSSs) are arrays of conductive elements or patches that have specific reflection and transmission responses. In this work, an FSS sensor designed to measure small (0% – 0.5%) and large (0% – 5%) scale strain is presented. The proposed unit cell of the sensor consists of two passive dipoles (of different dimensions) arranged normal to one another. This was done to reduce the error of small-scale strain on the large-scale strain measurement, and vice versa. Strain sensing is achieved by monitoring the change in the resonant frequencies of the two dipoles using an interrogating signal linearly polarized and aligned with the long dimension of the element under interrogation. Simulated results indicate that the sensitivity of the sensor to small-scale strain is 15 MHz/0.1% strain and 150 MHz/1.0% strain large-scale. The error in measurement can be partially alleviated, with a remaining error of 6 MHz for both measurements.