Abstract: An example system for passive sensing includes a coupled pair of resonators including a sensor resonator and a reader resonator, the sensor resonator including a resistor a loss associated with the resistor, and the reader resonator including a MOS cross-coupled pair that implements a nonlinear gain of the reader resonator via compressive saturation of negative resistance. An amplitude detector measures the amplitude of oscillations associated with the reader resonator, and the negative resistance is determined based on the measured amplitude of oscillations associated with the reader resonator when the measured amplitude reaches a steady state, i.e., when the gain of the reader resonator balances the loss of the sensor resonator. The resistance associated with the resistor of the sensor resonator may be determined based on the determined negative resistance. When the resistor is a resistive sensor, indications of measurements by the resistive sensor may be determined in this way.

Abstract: One example is directed to a reader device having a first resonance circuit and being configured to interrogate one or more other remotely-located resonance circuits, each associated with a second resonance circuit which may be part of a passive sensor circuit. The first resonance circuit is operated to cause the inductively-coupled oscillating signal to be swept over a range of frequencies and therein cause a jump or sudden transition in a frequency of the oscillating signal while the first and second resonance circuits are in sufficient proximity for inductively-coupling via an oscillating signal via their respective resonance circuits. Sensing circuitry may be used to detect the jump or sudden transition in the frequency of the oscillating signal and, by way of or in response to an indication of timing and/or a set of inductively-related parameters, data is conveyed from the sensor to the reader device via the inductively-coupled oscillating signal.

Abstract: One example is directed to a reader device having a first resonance circuit and being configured to interrogate one or more other remotely-located resonance circuits, each associated with a second resonance circuit which may be part of a passive sensor circuit. The first resonance circuit is operated to cause the inductively-coupled oscillating signal to be swept over a range of frequencies and therein cause a jump or sudden transition in a frequency of the oscillating signal while the first and second resonance circuits are in sufficient proximity for inductively-coupling via an oscillating signal via their respective resonance circuits. Sensing circuitry may be used to detect the jump or sudden transition in the frequency of the oscillating signal and, by way of or in response to an indication of timing and/or a set of inductively-related parameters, data is conveyed from the sensor to the reader device via the inductively-coupled oscillating signal.