Substrate choice impact on microwave sensor

In this paper, the impact of dielectric properties of a carrier substrate on the sensitivity of a planar microwave resonator is studied for sensing applications. It is demonstrated experimentally and practically that the substrate material plays a significant role in microwave sensor's characteristics. As a generic planar ring resonator, a passive microwave ring resonator with a slit is used to illustrate that a low permittivity substrate has a significantly higher sensitivity to permittivity variation in its environment, compared with a substrate with higher permittivity. Extensively, it is demonstrated that the same sensitivity analysis regarding substrate dielectric properties can be extended to active resonators, which have a higher quality factor and resolution than passive structures.