| Summary: | In this paper, the UV illumination effect for microwave gas sensors based on the tin dioxide was verified. A UV LED with emission wavelength close to the absorption edge of the SnO<sub>2</sub> gas-sensing layer was selected as the UV source. The developed gas sensors were tested under exposure to acetone in the 0−200 ppm range at room temperature. The sensor’s complex reflection coefficient corresponding to target gas concentration was measured with the use of a five-port reflectometer system exhibiting enhanced uncertainty distribution, which allows for the detection of low gas concentration. The UV illumination significantly emphasizes the sensors’ response in terms of both magnitude and phase for low gas concentrations, in contrast to previously reported results, in which only the reflection coefficient’s phase was affected. The highest responses were obtained for modulated UV illumination.
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