Realizing Multi-Parameter Measurement Using PT-Symmetric LC Sensors

With the rapid development in sensor network technology, the complexity and diversity of application scenarios have put forward more and more new requirements for inductor-capacitor (<i>LC</i>) sensors, for instance, multi-parameter simultaneous monitoring. Here, the parity-time (PT) symmetry concept in quantum mechanics is applied to <i>LC</i> passive wireless sensing. Two or even three parameters can be monitored simultaneously by observing the frequency response of the reflection coefficient at the end of the readout circuit. In particular, for three-parameter detection, a novel detection method is studied to extract the three resonant frequencies of the system through the phase-frequency characteristics of the reflection coefficient, which has never appeared in the previous literature on PT symmetry. The changes in three resonant frequencies are in response to changes in the three parameters in the environment. We show theoretically and demonstrate experimentally that the PT-symmetric <i>LC</i> sensor can realize multi-parameter measurement using a series LCR circuit as the sensor and a symmetric adjustable LCR circuit as the readout circuit. Our work paves the way for applying PT symmetry in multi-parameter detection.