We report the realization of coupling-independent, robust wireless sensing of fully passive resistive sensors. $\mathcal{P}\mathcal{T}$-symmetric operation obviates sweeping, permitting real-time, single-point sensing. Self-oscillation is achieved through a fast-settling nonlinearity whose voltage amplitude is proportional to the sensor’s resistance. These advances markedly simplify the reader. A dual time-scale theoretical framework generalizes system analysis to arbitrary operating conditions and a correction strategy reduces errors due to detuning from $\mathcal{P}\mathcal{T}$-symmetric conditions by an order of magnitude.

• Received 13 July 2020
• Revised 20 November 2020
• Accepted 24 November 2020

DOI:https://doi.org/10.1103/PhysRevApplied.14.064072