Bistable PT-Symmetric WPT Systems With Laterally Arranged Relays and Coupling Detuning

The implementation of parity-time (PT) symmetry in wireless power transfer (WPT) systems successfully prevents power transfer degradation by adaptively tracking the eigenfrequencies. For systems with relays, exact PT symmetry requires that the coupling coefficients between the transmitter (Tx) and relay(s) equal those between the receiver (Rx) and relay(s). However, this condition is generally unsatisfied in practical application scenarios involving positional uncertainties of the Rx. In this paper, under the condition of coupling detuning, we analyze the system’s behaviors and uncover its bistability characteristics. In the bistable region, the over-detuning mode is found to have a higher amplitude on the load than either the under-detuning mode or the exact PT-symmetric mode, indicating that it has the potential to improve the power transfer efficiency. We also develop a method to switch the system to operate in the over-detuning mode, if it initially operates in the under-detuning mode. Additionally, under an exact PT symmetry condition, we give a different perspective on a hybrid region where both the PT-symmetry and PT-broken modes coexist, which is different from previous works. Our work paves the way for extending the applications of PT-symmetric WPT systems, even without satisfying the exact PT symmetry conditions of coupling coefficients.