A Dual-Mode Split-Ring Resonator to Eliminate Relative Humidity Impact

In this letter, a compact resonant-based dual-mode microwave sensor is proposed, aimed to eliminate the erroneous effect of relative humidity (RH) in microwave chemical sensing within the uncontrolled environment. A single split-ring resonator (SRR) is employed as the sensor core and the first resonance (f(1) similar to 0.552 GHz) and the second resonance (f(2) similar to 1.03 GHz) of the resonator are utilized to calibrate the potential measurement error arising from ambient RH. Simulations of the sensor's design and sensitivity using the finite-element method were performed and presented, which are further confirmed by measurements for resonant profile variation considering RH change of 5%-70%. Using the proposed technique, SRR size reduction of 50% is achieved. In addition, common chemical materials of methanol, ethanol, 2-Isopropanol (IPA), and heptane are successfully detected, achieving clear distinction from the impact of external humidity.