The sensitivity of PT-symmetric LC wireless sensors around an exceptional point

Abstract

Inductor–capacitor (LC) wireless sensors are highly useful in applications that require them to be powered remotely and operated in rotating parts or harsh environments. Recent advances in the fields of parity-time (PT) symmetry proposed in the context of quantum mechanics have revealed that the performance of the LC wireless sensors can be improved. The basic sensing principle is to detect changes of the sensing capacitance, i.e., perturbation in PT- symmetry, through monitoring the frequency shift, i.e., eigenvalues in PT-symmetry. Here, we have analyzed and compared the sensitivity of the LC wireless sensors biased under an exact phase and near an exceptional point (EP). The frequency splitting responses of the PT-symmetric LC wireless sensors with the symmetric gain-loss arrangement are presented under asymmetric and symmetric perturbation, respectively. It shows that the asymmetric perturbation breaks PT-symmetry, leading to complex eigenvalues. In the exact phase, the high frequency response of two normal mode frequencies to symmetric perturbation shows the optimum sensitivity. The resulting eigenvalues splitting is proportional to the square root of perturbation near the EPs for both asymmetric and symmetric perturbation. The sensitivity to asymmetric perturbation is higher than that to symmetric perturbation. Finally, a capacitive humidity sensor was used to demonstrate the analysis.