Sensitivity Modeling of an RFID-Based Strain-Sensing Antenna With Dielectric Constant Change

Abstract

An RFID-based folded patch antenna has been developed as a novel passive wireless sensor to measure surface strain and crack, for the structural health monitoring of metallic structures. Up to 2.5 meters of read range is achieved by a proof-of-concept prototype patch antenna sensor with a strain sensitivity around -760 Hz/με, which is equivalent to a normalized strain sensitivity of -0.74 ppm/με. In this paper, we propose to consider the change of the substrate dielectric constant due to strain when modeling the antenna sensor. An enhanced strain sensitivity model is introduced for more accurately estimating the strain sensing performance of the hereby introduced "smart skin" antenna sensor. Laboratory experiments are carried out to quantify the dielectric constant change under strain. The measurement results are incorporated into a mechanics-electromagnetics coupled simulation model. Accuracy of the multi-physics coupled simulation is improved by integrating dielectric constant change in the model. Index Terms-Folded patch antenna, RFID sensor, structural health monitoring, smart skin, dielectric constant change, antenna sensor, wireless sensor, strain sensing.

A Review of Passive RFID Tag Antenna-Based Sensors and Systems for Structural Health Monitoring Applications

“…For this measurand, the antenna sensor design is to be considered so that the mechanical strain is changed into electrical signals and the electrical signals are transmitted to the reader via RFID technique simultaneously. The strain model addresses two factors affecting the measured sensitivity [46]: (i) the efficiency of mechanical strain transfer from the base structure to the top surface of the RFID antenna sensor; (ii) the substrate dielectric constant change because of strain. Strain is denoted as $\mathrm{sans-serif\epsilon }=\mathrm{normal\Delta }\mathrm{normalL}/{\mathrm{L}}_0$, where $\mathrm{normal\Delta }\mathrm{normalL}$ is difference length because of the strain and ${\mathrm{L}}_0$ is the initial “zero-strain” length.…”

A strain sensor realized by a multilayer dielectric antenna

“…Based on Equations (1), (7), (8), (11), and (12), we can calculate the resonance frequency of the presented antenna in theory, which can be seen in Table 5.…”

“…The design of dual-port ensures a certain strain homogeneity over the sensor part. In order to simulate the change of permittivity of dielectric substrate when the dielectric plate is deformed, Yi et al 8 designed a new strain sensitivity model which takes the change of dielectric constant of substrate into account. A passive strain-sensor based on a meander line antenna has also been designed.…”

Dielectric Characterization of Chinese Standard Concrete for Compressive Strength Evaluation

“…The presented results will be very useful for the future design of concrete-embedded antennas [43,44] and wireless power transfer to embedded sensors [45]. Nevertheless, further investigation into the imaginary part of complex permittivity, namely the loss factor of concrete, which has a different initial water content, is one of the immediate research works.…”