Electromagnetic Enhanced Microwave Gas Sensor for Room Temperature Detection of Ammonia

Microwave gas sensors (MGSs) have been studied extensively because of their advantages of room temperature operation, easy integration, and potential for wireless detection. However, there is no research that developed a systematic guideline on designing sensitive circuits and selecting appropriate sensitive materials. In this study, a group of complementary split ring resonator (CSRR)-based MGSs were proposed, simulated, and fabricated. The strong electric field (E-field) and magnetic field (H-field) of the CSRR sensor were confined in two separate sensitive areas by simulation. For the features of NH(3)(-)sensitive and different electromagnetic (EM) properties, ZnO and Co3O4 were employed as the sensitive materials. The MGSs have exhibited excellent detection limits as low as 0.2 ppm and outstanding selectivity at room temperature. On the basis of simulation and measured results, a compatibility principle between the sensitive materials and the circuit from the perspective of the field distribution has been proposed and discussed in detail. Finally, this study provides an optimized direction for MGS that designs sensitive circuits and selects appropriate sensitive materials from the point of view of field distribution.