A Non-Invasive Phase Sensor for Permittivity and Moisture Estimation Based on Anomalous Dispersion

Omar Siddiqui, Rashad Ramzan, Muhammad Amin, Omar M. Ramahi

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)


The traditional microwave resonance sensors are based on the measurement of the frequency shift and bandwidth of a resonator's amplitude spectrum. Here we propose a novel sensing scheme in which the material properties are estimated by determining the changes in the phase spectrum of an anomalous-phase resonator. In the proposed phase sensing, we exploit the unique double phase reversal which takes place on the edges of the anomalous dispersion region as a signature to detect the resonance. We show that with the phase sensing, a significant reduction in detection errors compared to the traditional sensing can be obtained because of the noise immunity offered by the phase detection and also due to the strong dispersive phase response that reduces the sensor's dependence on the external environment. We also show that the bandwidth determination procedure of the resonance which is needed to characterize the sample losses is significantly simplified. The concept of phase sensing is shown by devising an experimental microstrip open stub resonator whose frequency response lies in the anomalous dispersion region. The dielectric characteristics of the samples placed on the stub are extracted from the resonant frequency and the slope of the phase response. We also demonstrate that the changes in moisture levels can also be detected by utilizing the phase sensing method.

Original languageEnglish
Article number28626
JournalScientific reports
Publication statusPublished - Jun 27 2016

ASJC Scopus subject areas

  • General


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