Pseudo-Hermitian Exceptional-Point-Based Wireless Sensing System With Heterogeneous Coupling

Abstract

This letter presents a pseudo-Hermitian exceptional-point (EP) wireless sensor that exploits heterogeneous inductive–capacitive coupling to realize a third-order exceptional point (EP3) in a compact three-resonator trimer. Replacing the conventional gain-relay-loss inductive chain by a mixed inductive/capacitive link merges two LC tanks into a single physical entity, shrinking the footprint by about 50% while preserving the EP3 topology. A perturbative analysis shows that the eigenfrequency shift follows a cubic-root law when either the relay or loss resonator capacitance is perturbed, with the response to the former being approximately $1.6\times $ that to the latter—the only accessible node in some applications of conventional all-inductive trimers. The EP is experimentally identified by the zero crossing of Im( $S_{11}$ ) rather than the reflection dip, suppressing linewidth broadening and improving readout precision. Theoretical predictions of the EP3 response are quantitatively verified by both simulation and experiment. The proposed heterogeneous-coupling paradigm is fully compatible with standard printed circuit boards and customized readout-circuit processes, enabling additional footprint reduction for ultra-miniaturized sensor applications.