RESONANT INDUCTIVE SENSING WITH ALGORITHMIC CONTROL LOOP FOR TUNING NEGATIVE IMPEDANCE TO RESONATOR IMPEDANCE

摘要

A resonant inductive sensing system includes a sensor resonator and an inductance-to-data converter (IDC) including an algorithmic control loop with operational and calibration phases. The resonator is characterized by a resonance state corresponding to a sensed condition. The IDC includes a negative impedance stage and a loop control stage. During the operation phase, the negative impedance stage drives the resonator with a selected (controlled) negative impedance. The loop control stage includes detection circuitry that detects resonance state, and range comparison circuitry that generates an out-of-range signal when the detected resonance state is not within a pre-defined range of resonance states. Algorithmic control circuitry is responsive to the out-of-range signal to transition the IDC to operation in the calibration phase, including determining an adjusted negative impedance corresponding to a resonance state within the pre-defined range of resonance states, and generating a negative impedance control signal based on the adjusted negative impedance.