Design of a Passive Sensor Based on Air Holes for Humidity Detection

Aiming at the problems of humidity sensors in closed and dangerous situations, limited measurement of humidity parameters by external power supply and limited application range of traditional microwave passive devices composed of metal waveguides or microstrip lines, a new type of waveguide structure for humidity detection is designed and fabricated. The model of the SIW sensor is built, simulated and optimized by using HFSS electromagnetic simulation software, and the design of the passive humidity sensor is completed. A passive humidity sensor is realized by using the air through hole as a humidity sensitive material combined with the SIW structure. The feasibility of the sensor can be used for humidity measurement is verified by circuit analysis and simulation. The PCB board process is used to complete the fabrication of the sensor, and the humidity test platform is used to complete the test of the sensor. The test results show that the sensor can be detected in the range of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$70-100 \% \text{rH}$</tex> humidity, and the sensitivity is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1 \text{MHz} / \text{RH} \%$</tex>. The sensor has a wide range of application value in industrial and environmental monitoring and other fields with simple preparation process and high sensitivity.