Sensitivity evaluation of dielectric perturbed substrate integrated resonators for hydrogen detection

This paper presents a theoretical and experimental study of a substrate integrated resonator (SIW) structure for gas sensing applications. The goal of the presented work is to evaluate, via an analytical model of sensitivity based on the resonant perturbation method, the evolution of the sensitivity of SIW sensors, which essentially depends on the properties of the functionalized region. The effect of the SIW resonator parameters, such as the size, the relative permittivity and the topology of the functionalized areas, are studied. In order to validate the theoretical study and propose the best design to maximize the sensitivity, different topologies of SIW sensors are fabricated and tested experimentally. The operation frequency of the SIW resonator is comprised between 4 and 6 GHz, and hydrogen is used as the detection gas. The SIW resonators are functionalized with tin oxide (SnO2) micro powder, which is a dielectric material sensitive to hydrogen gas. Thus, the experimental results of the sensor, whose detection principle is based on the variation of the effective dielectric permittivity caused by the presence of hydrogen, exhibit sensitivities ranging from 8.1 to 33.9%, depending on the size, the relative permittivity or the topology of the functionalized region of the gas sensor. This new concept provides a low-cost solution for passive sensors that can be easily integrated in a PCB fabrication process.