Compact Design of a Normal-Mode Helical Antenna for Wireless Temperature Monitoring

Abstract

This paper presents a design of a compact normal mode helical antenna (NMHA) to be integrated with a surface acoustic wave (SAW) sensor for wireless temperature monitoring. The miniaturized antenna is designed to resonate at a frequency of 915 MHz using Ansys High-Frequency Structure Simulator (HFSS). The antenna has been optimized for its critical design parameters such as the pitch, number of turns, and the helix antenna diameter. A non-uniform pitching technique was applied to achieve a compact size of the antenna with 0.055, which was later integrated with the SAW sensor for temperature monitoring applications. The optimal design achieved a return loss of 20.78 dB and offers sufficient bandwidth of 25 MHz that covers the operational frequency of the SAW sensor. We also measured the return loss of the integrated system between our proposed antenna and SAW sensor under various applied heating conditions. A well-observed distinction can be achieved, and the information will be useful for temperature conversion as the ultimate results.