Abstract
We experimentally investigate a new class of resonant dielectric sensors that are based on reflectance phase measurement in the Lorentzian dispersion regime. The Lorentzian dispersion, also known as anomalous dispersion, is characterized by a strong wave absorption accompanied by a double reversal of the phase (flip-flop phase). Since the Kramer-Kronig relation holds, a phase-slope measurement is enough to completely characterize a dielectric material at in the narrowband microwave spectrum. Due to strong dispersion, the Lorentz sensors are noise immune and are less affected by external circuit changes. Therefore, they can be potentially applied in hostile environments such as high temperature furnaces. The proposed detection method is inspired from the optical measurement technique known as spectroscopic ellipsometry. We apply the anomalous phase detection to estimate dielectric and moisture changes.