Compelling impact of intermodulation products of regenerative active resonators on sensitivity

In this paper, a new technique to enhance the sensitivity of microwave resonators is introduced. Double split ring resonators are implemented as the core of an active resonator. It is illustrated that regenerative coupled-oscillators can produce higher order intermodulation products at the output signal. The variations in sensing tone are multiplied and exhibit considerably higher sensitivities at 3rd, 5th, and 7th IM components compared to the main resonant frequency. The sensor is also integrated into wireless platform with ultra-wideband bowtie antennas. Common fluids such as Toluene, IPA, Methanol, and Water are tested in fluidic channel and demonstrated that the sensitivity for intermodulation products are significantly increased. It is expected that such behavior reduces the limit of detection and enables more sensitive measurements.