  High-performance interrogation of inductor-capacitor (LC) microsensor has
been a long-standing challenge due to the limited size of the sensor.
Parity-time (PT) symmetry, an intriguing concept originated from quantum
physics, has been utilized to improve the spectral resolution and sensitivity
of the conventional readout circuit, while the PT symmetry condition has to be
satisfied. In this work, a sandwich-type wireless capacitance readout mechanism
based on perturbed PT-symmetric electronic trimer without manual tuning of the
reader circuit is proposed. Theoretical eigenvalue analysis by solving the
system equations shows that the system exhibits single real mode in weak
coupling regime whose eigenfrequency changes in response to the capacitance of
the neutral resonator. Furthermore, the proposed readout system exhibits wider
readout capacitance range compared to standard PT-symmetry-based system while
retaining higher Q-factor compared to conventional readout method, which has
been validated with the experimental prototype based on printed circuit board.
Our work not only enriches the underlying theory of non-Hermitian physics, but
also shows potential applications in scenarios where longer interrogation
distance is required, such as implanted medical devices, parameter detection in
harsh environment, etc.
