Temperature Self-Compensation Method for Crack Length Measurement Based on a Microstrip Antenna Sensor

A temperature self-compensation method for the microstrip antenna sensor is innovatively proposed to reduce the measurement error associated with temperature variation. Temperature compensation is achieved by inserting a layer of compensation substrate in the resonant cavity of the antenna sensor. The compensation substrate with a thermal coefficient of the dielectric constant opposite that of the sensor substrate is designed to offset the frequency variation of the sensor. The design parameters of the sensor are obtained from multi-layer substrate theory and microstrip antenna theory. The temperature compensation performance of the sensor is experimentally and numerically analyzed to validate the proposed method. The results show that the microstrip antenna sensor proposed in this paper provides more accurate measurement results of the structural crack length with an identification error of ±0.2mm within the temperature range of 0 to 60 °C. This reduces the measurement error of the crack length in a multi-temperature environment by more than 95%, relative to that of conventional microstrip antenna sensors.