Water Antenna Based Passive Wireless Temperature Sensor

Passive wireless temperature sensors have attracted great attention in power systems, since they can work safely and stably under high temperature and high pressure environment with the advantages of compact size, easy integration, low-cost and high sensitivity. This paper proposes a type of passive wireless temperature sensor based on water patch antenna. The permittivity of the distilled water integrated into the antenna substrate changes with temperature, which results in the changes of resonant frequency. A single-polarized and a dual-polarized water antenna with temperature sensitivity are designed, which are working at around 2 GHz. The single-polarized water antenna works at 2.06 GHz at room temperature, with a bandwidth $(\vert \mathrm{S}11\vert < -10\ \text{dB})$ of about 3% and gain of 3.50 dBi. The dual-polarized water antenna works at 1.95 GHz at room temperature, with a bandwidth $(\vert \mathrm{S}11\vert < -10\ \text{dB})$ of about 2% and gain of 2.43 dBi. The simulation results show that the sensitivity of 5 MHz/10°C can be obtained when the temperature changes from 20 °C to 90°C for both sensors.