Simulation of RFID based Folded Patched Antenna for Strain Sensing
RFID based strain sensors with quarter wave rectangular patched antennas were investigated for monitoring the strain in structures. When the patch antenna is under strain/deformation, causing electromagnetic resonance frequency of the antenna shifting, its resonance frequency varies accordingly. The RFID based sensors can be interrogated by a wireless or wired interrogation equipment, and the variation of the resonance frequency can be identified by measuring the backscatter parameter of antenna, then the amount of the strain can be determined. This paper designed two folded patched antenna sensors with different material of the substrate, RT 5870 and FR4. A 2.4GHz quarter wave patched antenna is used for minimizing the size of the sensor. The correlation between resonance frequency variation and the strain were simulated numerically via HFSS and the strain transfer efficiency of sensor were simulated via ABAQUS software. The simulation results showed that the variation of the resonance frequency of both sensors is due to the contribution of the strain in longitudinal direction. The width variation of the rectangular patched antenna has little influence on the variation of resonance frequency in transversal direction, therefore the resonance frequency shifting of strain sensors depends on the strain in longitudinal direction. To compare the difference between two antennas, the antenna with FR4 substrate has a better performance, it has smaller size, less impact of width strain and better strain transfer efficiency.