Microstrip Patch Antenna Temperature Sensor

The resonant frequencies of a microstrip patch antenna are dependent on the dielectric constant of its substrate and the physical dimensions of its radiation patch. Both of these parameters are temperature-dependent. In this paper, we investigated the effects of temperature on the antenna resonant frequencies for the purpose of studying the microstrip patch antenna as a temperature sensor. First, the relationship between the antenna resonant frequency shift and the temperature change is derived based on the transmission line model. To validate the theoretical prediction, antenna sensors bonded on different metal bases were tested in a temperature chamber. By comparing the measured temperature-frequency relationship with the theoretical predictions, we discovered that the dielectric constant of the substrate is not only dependent on temperature but also influenced by the base material. After calibrating the thermal coefficient of the substrate dielectric constant using the measurement data, the differences between the measurements and the theoretical predictions were within the expected systematic error of the reference thermocouple, validating that a microstrip patch antenna can serve as a temperature sensor.