A miniaturized evanescent mode HMSIW humidity sensor

A passive evanescent mode half-mode substrate integrated waveguide (HMSIW) resonator loaded with a complementary split ring resonator (CSRR) is designed and fabricated for humidity sensing applications. The use of the CSRR which is etched on the top plane of the HMSIW can significantly reduce the size of the device. Without any sensing material, the sensor which has a compact size of 5.8 mm×5.8 mm can provide high humidity sensitivity up to 5.82 MHz/%RH at high relative humidity (RH) region (>84.3%). The results indicate that the proposed structure is a promising candidate for radio and microwave humidity sensing applications.