Disclosed is a system and method for controlling handheld devices without contact by interacting with their wireless charging coils or other inductive coil antennae. The present disclosure utilizes the interaction between human body and the coil wherein the coil is used to send alternating magnetic field to interact with a control signal, such as a hand, instead of simply using the coil in the smart phone as a power receiver. The hand movement in front of the wireless charging coil changes the coil's conductivity distribution, which creates effective coil impedance also known as reflected impedance.

A system includes a sensor integrated circuit (IC), including a driver adapted to be coupled to an oscillator, the driver including first and second transistors. The sensor IC includes an amplitude control amplifier coupled to the first transistor. The sensor IC also includes a common mode control amplifier coupled to the second transistor. The sensor IC includes a handover control circuit coupled to the amplitude control amplifier and configured to hand off an operation from the sensor IC to a different sensor IC, the handover control circuit including a resistor network coupled to a switch network.

In an embodiment, an inductive proximity sensor includes two receiving coils and one transmitting coil arranged between the two receiving coils. The receiving coils and transmitting coil are each formed from a group of at least two individual coils on carrier boards, which are arranged parallel to one another. The carrier boards have a diameter which is smaller than or equal to 10 mm, and a winding of the receiving coils or the transmitting coil has a cross-sectional geometry in which a ratio of a base width to a height lies in the range from 0.2 to 0.3. An embodiment of a method for detecting an object using an inductive proximity sensor includes generating an alternating field using a transmitting coil of the proximity sensor and sensing, using two receiving coils of the inductive proximity sensor, a change in the alternating field caused by proximity of the object.

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. Negative impedance magnitude is controlled by the loop control stage, with the output comparator generating a multi-level loop control signal the controls drive current level based on resonator oscillation amplitude (the time-average of the multi-level drive current).

A system includes a sensor integrated circuit (IC), including a driver adapted to be coupled to an oscillator, the driver including first and second transistors. The sensor IC includes an amplitude control amplifier coupled to the first transistor. The sensor IC also includes a common mode control amplifier coupled to the second transistor. The sensor IC includes a handover control circuit coupled to the amplitude control amplifier and configured to hand off an operation from the sensor IC to a different sensor IC, the handover control circuit including a resistor network coupled to a switch network.

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. Negative impedance magnitude is controlled by the loop control stage, with the output comparator generating a multi-level loop control signal the controls drive current level based on resonator oscillation amplitude (the time-average of the multi-level drive current).

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. Based on resonator oscillation amplitude, the output comparator provides a discrete loop control signal to the discrete current source, driving the resonator with a negative impedance that balances resonant impedance, thereby maintaining constant resonator oscillation amplitude corresponding to steady-state oscillation.

A method for measuring a physical quantity with a, particularly inductive, sensor element and for providing a sensor output depending on the physical quantity. The sensor element is part of a resonant circuit whose attenuation depends on the physical quantity being measured. The resonant circuit is excited to generate a periodic oscillation signal, the amplitude of which depends on the attenuation. The oscillation signal is compared with a comparator threshold value in a comparator to produce a periodic comparator signal with a duty cycle depending on the comparator threshold value. The comparator threshold value is set to be different from a mean value of the oscillation signal so that a duty cycle different from 50% is achieved. The sensor output is output depending on the duty cycle of the comparator signal.