Implementation of Four-parameter LC Sensing Through Symmetric Dual-Resonant Circuit

LC-type sensors have been widely investigated and applied in sealed and harsh environments, because of the passive wireless features. However, most reported LC sensors can only monitor one or two parameters at a time. This paper provides a novel symmetric LC circuit configuration that has two mutually independent resonant modes. It is demonstrated that each mode can characterize two different parameters of interest. By using two diode varactors and two variable resistors as the sensing elements, a prototype of four-parameters monitoring system is implemented. Experimental results demonstrate that, the sensitivities of the two resonant frequencies are 557.14 kHz/V and 154.97 kHz/V, respectively; and the sensitivities of the Q-values are 0.27kΩ−1 and −0.22Ω−1, respectively.