A novel ultra-high frequency humidity sensor based on a magnetostatic spin wave oscillator

This paper presents a robust, simple and highly sensitive method to detect vapour compounds using a magnetostatic spin wave (MSW) tunable oscillator based on a yttrium iron garnet (YIG) epitaxial thin film coupled to a coplanar waveguide resonator. In this work, the device has been tested as relative humidity sensor. For this purpose, the coplanar waveguide resonator was coated with polyvinylpyrrolidone (PVP) polymer and used as a humidity probe. A dielectric change in the PVP due to a change in the ambient humidity introduces a fast phase shift in the probe, which causes a frequency shift in the MSW oscillator. The humidity sensing behavior of this device was investigated at room temperature over a range of 12.5–95% relative humidity (RH). Furthermore, the device was used to monitor human breath as a non-invasive sensor, showing great adaptability and ease of use in a real application. In conclusion, the sensor exhibited reproducibility, accuracy, high sensitivity, and fast response and recovery times. It also has the advantage of being simple and cost-effective.