Highly Sensitive ELC Resonator Based Differential Sensor

A highly sensitive electric LC resonator derived differential sensor is proposed in this work, with the major focus on detecting the purity of any reference dielectric material. The proposed sensor is designed with two identical electric-LC resonators being loaded on either side of a 50 Ω microstrip line such that the magnetic wall of the microstrip line is perfectly aligned with that of the resonators. The fabricated unloaded sensor is operating at a resonance frequency of 3.385 GHz, falling between the two ISM bands, exhibiting a peak electric field intensity at the capacitive gap. The working principle of the sensor is analyzed through a lumped element equivalent circuit model. Experimental validation is performed via the fabricated prototype of the developed sensor on Taconic TLY-5 substrate for various standard and unknown dielectric samples. For the accurate testing of various samples using the proposed sensor, an empirical relationship is developed relating the difference in the resonance frequencies of the unloaded and loaded resonators, and the sample thickness. Furthermore, a novel error modelling technique is also incorporated to take into consideration the effect of fabrication tolerance and any possible air gap between the sensor region and the test specimen. The proposed differential sensor possess a substantially higher normalized sensitivity of 4.915% (165 MHz in terms of absolute sensitivity), which is quite useful for applications requiring detection of purity of a product. Its applicability is validated here by detecting the presence of termite infestation in wood sample.