Abstract: A resonant inductive sensing system includes an active resonator target that balances losses in the target resonator. The resonant sensor includes a sensor resonator LC circuit and a resonant target including a target resonator Lt/Ct circuit characterized by a loss factor Rts and a target quality factor Qt. The sensor resonator LC circuit and the target resonator Lt/Ct circuit are configured for operation as coupled resonators. The resonant sensor includes a sensor circuit configured to drive the resonant sensor, such that the sensor resonator LC circuit projects a magnetic sensing field based on a sensor quality factor Q, and an active negative resistance circuit ?Ra coupled to the target resonator Lt/Ct circuit, and configured to substantially cancel the loss factor Rts, such that target quality factor Qt is substantially Qt=(?[Lt/Ct]/Rts)(RaRts/[RaRts?Lt/Ct]).

Abstract: A resonant impedance sensing system includes a class D negative impedance stage implemented with a Class D comparator, and a loop control stage implemented with an output comparator clocked by the class D comparator, establishing a negative impedance control loop that includes the resonator as a loop filter. The negative impedance stage includes a multi-level current source (such as a current DAC) interfaced to the resonator through an H-bridge controlled by the class D comparator. Class D switching synchronizes resonator oscillation voltage (input to the class D comparator) with resonator current drive (from the multi-level current source), driving the resonator with a negative impedance that balances resonator impedance to maintain sustained oscillation.

Abstract: A rotational resolver system and method includes a rotational shaft to which at least one eccentric conductive coarse resolution disc is fixed and to which at least one conductive fine resolution disc is also fixed. The fine resolution disc defines a plurality of generally semicircular protruding edge segments. At least one conductive coarse-disc sensing coil is disposed adjacent an edge of the coarse resolution disc, and at least one conductive fine-disc sensing coil is disposed adjacent the edge of the fine resolution disc. These coils may be oriented for axial sensing of the respective disc.

Abstract: 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.

Abstract: A resonant inductive sensing system includes in the drive current signal path of the resonator a pulse shaper for noise reduction, including reducing noise resulting from down modulation of signal energy around harmonics of the oscillator (multiples of the resonance frequency), and from uncertainty in the duration of the oscillation period. The pulse shaper is configured so that, for each modulation period of the drive current, consecutive drive current pulses are substantially identical. In example embodiments, an inductance-to-digital conversion (IDC) unit includes drive circuitry configured to drive excitation current pulses to the resonator with a modulation period synchronized with a resonator oscillation frequency, and pulse shaping circuitry configured to pulse shape the drive current pulses so that each pair of drive current pulses within a modulation period are substantially identical.

Abstract: An inductive gear sensing system suitable for sensing gear (gear tooth) movement, such as some combination of speed, direction and position, based on differential sensor response waveforms. Example embodiments of inductive gear sensing with differential sensor response for different gear configurations include generating differential pulsed/phased sensor response signals from dual differential sensors based on axial (proximity-type) sensing for offset differential sensors (FIG. 1B, 102, 102; FIG. 2B, 201, 202), and generating asymmetrical response signals from a single sensor based on lateral and axial sensing with either asymmetrical gear teeth (FIG. 3A, 30A; FIG. 3B, 30B) or an asymmetrical sensor (FIG. 4B, 401) or a combination of both.

Abstract: One example includes a position sensing system. The system includes an inductive position element that is moveable and comprises a position inductor. The system also includes a plurality of inductive load elements. Each of the inductive load elements includes a load inductor. Each of the plurality of inductive load elements can be selectively controlled in response to a modulation signal to provide a corresponding mutual inductance between the position inductor and the respective load inductor, the corresponding mutual inductance depending on a position of the inductive position element relative to the respective load inductor. The system further includes a position controller configured to generate the position and modulation signals and to calculate the position of the inductive position element relative to the plurality of inductive load elements based on a difference of the position signal with respect to the mutual inductance between the position inductor and each respective load inductor.

Abstract: A resonant impedance sensing system includes a class D negative impedance stage implemented with a Class D comparator, and a loop control stage implemented with an output comparator clocked by the class D comparator, establishing a negative impedance control loop that includes the resonator as a loop filter. The negative impedance stage includes a multi-level current source (such as a current DAC) interfaced to the resonator through an H-bridge controlled by the class D comparator. Class D switching synchronizes resonator oscillation voltage (input to the class D comparator) with resonator current drive (from the multi-level current source), driving the resonator with a negative impedance that balances resonator impedance to maintain sustained oscillation.

Abstract: A resonant impedance sensing system includes a negative impedance control loop incorporating the resonator as a loop filter, and including a class D negative impedance stage implemented with a class D comparator, and a loop control stage implemented with an output comparator clocked (D_clk) by the class D comparator. The class D comparator receives resonator oscillation voltage, and generates a class D switching output synchronized with resonator oscillation frequency. A discrete current source (such as a current DAC) drives the resonator through an H-bridge switched by the class D switching output, so that the time average of the discrete drive current corresponds to resonator oscillation amplitude.

Abstract: A test system (and methodology) suitable for testing a resonant sensor circuit configured to drive a sensor resonator with a negative resistance. Example embodiments include a test sensor resonator setup configured to simulate a sensor resonator with a selectable loss factor Rs, and includes, in a single-ended configuration, a first oscillator signal source that generates a first oscillation signal, coupled to a first controllable resistor that provides a controlled resistance R1 that simulates a selectable sensor resonator loss factor Rs, which together generate a first oscillation voltage signal based on the controlled resistance R1. A DUT resonant sensor circuit is coupled to receive the first oscillation voltage signal at a first input, and generate a negative resistance ?Ra that substantially counterbalances the resistance R1 (corresponding to sustained oscillation).

Abstract: Wideband capacitive sensing (single-ended or differential) is based on a modulated sense (capacitance) signal. A carrier/drive signal path modulates a reference signal with a carrier signal (such as fixed frequency or spread spectrum) to generate a carrier/drive signal, driven (with optional pre-scaling) out through an output node (to sense capacitor(s)). A sense signal path receives at an input/summing node up-modulated sense capacitance signal(s), corresponding to measured capacitance up-modulated to the carrier frequency, and, after filtering (optional) and amplification, demodulates the up-modulated sense capacitance signal with the carrier signal, to generate a demodulated sense capacitance signal corresponding to measured capacitance, which can be converted to sensor data. Sense signal path amplification can use charge amplification (capacitor feedback), or transimpedance amplification (resistor feedback).

Abstract: A test system (and methodology) suitable for testing a resonant sensor circuit configured to drive a sensor resonator with a negative resistance. Example embodiments include a test sensor resonator setup configured to simulate a sensor resonator with a selectable loss factor Rs, and includes, in a single-ended configuration, a first oscillator signal source that generates a first oscillation signal, coupled to a first controllable resistor that provides a controlled resistance R1 that simulates a selectable sensor resonator loss factor Rs, which together generate a first oscillation voltage signal based on the controlled resistance R1. A DUT resonant sensor circuit is coupled to receive the first oscillation voltage signal at a first input, and generate a negative resistance ?Ra that substantially counterbalances the resistance R1 (corresponding to sustained oscillation).

Abstract: 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.

Abstract: A rotational resolver system and method includes a rotational shaft to which at least one eccentric conductive coarse resolution disc is fixed and to which at least one conductive fine resolution disc is also fixed. The fine resolution disc defines a plurality of generally semicircular protruding edge segments. At least one conductive coarse-disc sensing coil is disposed adjacent an edge of the coarse resolution disc, and at least one conductive fine-disc sensing coil is disposed adjacent the edge of the fine resolution disc.

Abstract: An inductive gear sensing system suitable for sensing gear (gear tooth) movement, such as some combination of speed, direction and position, based on differential sensor response waveforms. Example embodiments of inductive gear sensing with differential sensor response for different gear configurations include generating differential pulsed/phased sensor response signals from dual differential sensors based on axial (proximity-type) sensing for offset differential sensors (FIG. 1B, 102, 102; FIG. 2B, 201, 202), and generating asymmetrical response signals from a single sensor based on lateral and axial sensing with either asymmetrical gear teeth (FIG. 3A, 30A; FIG. 3B, 30B) or an asymmetrical sensor (FIG. 4B, 401) or a combination of both.

Abstract: One example includes a position sensing system. The system includes an inductive position element that is moveable and comprises a position inductor. The system also includes a plurality of inductive load elements. Each of the inductive load elements includes a load inductor. Each of the plurality of inductive load elements can be selectively controlled in response to a modulation signal to provide a corresponding mutual inductance between the position inductor and the respective load inductor, the corresponding mutual inductance depending on a position of the inductive position element relative to the respective load inductor. The system further includes a position controller configured to generate the position and modulation signals and to calculate the position of the inductive position element relative to the plurality of inductive load elements based on a difference of the position signal with respect to the mutual inductance between the position inductor and each respective load inductor.

Abstract: Resonant impedance sensing with a resonant sensor (such as LC) is based on generating a controlled negative impedance to maintain steady-state oscillation in response to changes in resonance state caused by interaction with a target. Resonant impedance sensing can include: (a) generating a controlled negative impedance at the sensor; (b) controlling the negative impedance based on a detected resonance state to substantially cancel the sensor resonant impedance, such that the sensor resonance state corresponds to steady-state oscillation, where the negative impedance is controlled by a negative impedance control loop that includes the sensor resonator as a loop filter; and (c) providing sensor response data based on the controlled negative impedance, such that the sensor response data represents a response of the sensor to the target. Thus, the response of the sensor to the target corresponds to the negative impedance required for steady-state oscillation.

Abstract: A resonant inductive sensing system includes an active resonator target that balances losses in the target resonator. The resonant sensor includes a sensor resonator LC circuit and a resonant target including a target resonator Lt/Ct circuit characterized by a loss factor Rts and a target quality factor Qt. The sensor resonator LC circuit and the target resonator Lt/Ct circuit are configured for operation as coupled resonators. The resonant sensor includes a sensor circuit configured to drive the resonant sensor, such that the sensor resonator LC circuit projects a magnetic sensing field based on a sensor quality factor Q, and an active negative resistance circuit ?Ra coupled to the target resonator Lt/Ct circuit, and configured to substantially cancel the loss factor Rts, such that target quality factor Qt is substantially Qt=(?[Lt/Ct]/Rts)(RaRts/[RaRts?Lt/Ct]).

Abstract: A resonant inductive sensing system includes in the drive current signal path of the resonator a pulse shaper for noise reduction, including reducing noise resulting from down modulation of signal energy around harmonics of the oscillator (multiples of the resonance frequency), and from uncertainty in the duration of the oscillation period. The pulse shaper is configured so that, for each modulation period of the drive current, consecutive drive current pulses are substantially identical. In example embodiments, an inductance-to-digital conversion (IDC) unit includes drive circuitry configured to drive excitation current pulses to the resonator with a modulation period synchronized with a resonator oscillation frequency, and pulse shaping circuitry configured to pulse shape the drive current pulses so that each pair of drive current pulses within a modulation period are substantially identical.

Abstract: A resonant impedance sensing system includes a negative impedance control loop incorporating the resonator as a loop filter, and including a class D negative impedance stage implemented with a class D comparator, and a loop control stage implemented with an output comparator clocked (D_clk) by the class D comparator. The class D comparator receives resonator oscillation voltage, and generates a class D switching output synchronized with resonator oscillation frequency. A discrete current source (such as a current DAC) drives the resonator through an H-bridge switched by the class D switching output, so that the time average of the discrete drive current corresponds to resonator oscillation amplitude.