Dual-sensing and dual-frequency microwave SRR sensor for liquid samples permittivity detection

Abstract

In this paper, a microwave sensor based on the split ring resonator has been proposed to detect the real part of the dielectric constant of the liquid sample. The proposed structure composed of non-identical double-split ring resonators which are placed in the inner part of the power divider branches. The proposed sensor has two purposes: (1) Measurement of the permittivity of one sample under test in two frequency bands (multi-band), (2) Dual samples under test for simultaneous dielectric detection (multi-sensing). There are several advantages in measuring the permittivity of the sample under test with the proposed sensor such as high Q-factor, high sensitivity, compact size, multi-sensing and multi-band. This paper investigates resonance frequency variation relative to the samples with different permittivities, such as ethanol, methanol, glucose solution and deionized water compared to previous similar works in simulation and experimental results. The permittivity of samples under test varies from 24 to 78 at 25 ˚C, and the simulated sensor resonance frequency would change about from 5.76 to 4.8 GHz at first resonance frequency and 7.85 to 6.35 GHz at second resonance frequency.