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Non-radiative wireless power transfer (WPT) technology has made considerable progress with the application of the parity-time (PT) symmetry concept. In this letter, we extend the standard second-order PT-symmetric Hamiltonian to high-order symmetric tridiagonal pseudo-Hermitian Hamiltonian, relaxing the limitation of multi-source/multi-load system based on non-Hermitian physics. We proposed a three-mode pseudo-Hermitian dual-transmitter-single-receiver circuit and demonstrate that robust efficiency and stable frequency WPT can be achieved even though PT-symmetry is not satisfied as usual. In addition, no active tuning is required when the coupling coefficient between the intermediate transmitter and the receiver is changed. Moreover, the proposed system has an open frequency band gap with an abrupt frequency change at the phase transition point, which is expected to advance wireless sensing technologies.

In this article, we report a vector-network-analyzer-free and real-time LC wireless capacitance readout system based on perturbed nonlinear parity-time (PT) symmetry. The system is composed of two inductively coupled reader-sensor parallel RLC resonators with gain and loss, respectively. By searching for the real mode that requires the minimum saturation gain, the steady-state frequency evolution as a function of the sensor capacitance perturbation is analytically deduced. The proposed system can work in different modes by setting different perturbation points. In particular, at the exceptional point of PT symmetry, the system exhibits high sensitivity. Experimental demonstrations revealed the viability of the proposed readout mechanism by measuring the steady-state frequency of the reader resonator in response to the change of trimmer capacitor on the sensor side. Our findings could impact many emerging applications such as implantable medical device for health monitoring, parameter detection in harsh environment, sealed food packages, etc.