Air vehicle humidity sensor based on PVA film humidity sensing principle

In order to ensure the flight safety of an aircraft and reduce the loss of humidity to the precision instruments and equipment in the aircraft, this study designs a small-size resonator antenna shape based on Radio Frequency Identification (RFID) technology and sensor principles. The resonator antenna makes use of the characteristics of the square ring and bent resonator and, at the same time, adopts the polyvinyl alcohol film with strong hygroscopic performance as the moisture-sensitive material. The equivalent resonant circuit of the sensor is constructed, and the parameters are optimized according to the principle of “coarse tuning of inductance parameters and fine tuning of capacitance parameters” to determine the optimal size. The relationship between the resonance frequency and the resonance response of humidity was investigated by the optimized model of the RFID resonator and polyvinyl alcohol (PVA). The simulation results show that as the relative humidity increases from 29.1 %RH to 90.9 %RH, the dielectric constant of the PVA film increases from 5.3 to 22 and the resonance frequency of the resonator decreases significantly from 4.74 to 4.12 GHz, with a total offset of 620 MHz, and the sensitivity is as high as 10.03 MHz/%RH. The results show that the designed sensor has a high sensitivity to humidity changes and a wide humidity detection range, providing an advanced solution for the detection and control of humidity inside aircraft.