Wireless passive high-temperature sensor based on multifunctional reflective patch antenna up to 1050 degrees centigrade

A novel wireless passive temperature sensor based on a reflective patch is demonstrated up to 1050 °C herein. This reflective patch acts as a patch resonator (temperature sensor) and an integrated antenna at the same time. The temperature sensing mechanism is the monotonic increase of the dielectric constant of alumina versus temperature, which reduces the resonant frequency of a patch resonator formed on such an alumina substrate. By properly designing the shape and dimensions of the patch, it can also act as a transmit/receive antenna for wireless passive sensing. Therefore, temperatures can be wirelessly sensed by measuring the resonant frequency of the temperature sensor using an interrogation antenna. This temperature sensor uses robust alumina and platinum materials for high-temperature applications. In addition, this wireless passive temperature sensor is simple in mechanical structure and low in profile, with the potential to be in conformal shape. A temperature sensor using this reflective patch was designed, fabricated and tested from 50 to 1050 °C in ambient. The resonant frequency of the sensor decreases from 5.07 to 4.58 GHz, which corresponds to a dielectric constant change from 9.7 to 11.4 for the alumina substrate. The temperature measurement sensitivity is found to be 0.58 MHz/°C at 1050 °C. Being wireless, passive, planar and low profile, the proposed high-temperature sensor can be used for various harsh-environment applications.