Measuring phasors of phase quadrature signals for capacitive sensing

A system comprising:

• a capacitive sensing system comprising first and second transmit electrodes and a receive electrode positioned to have mutual capacitances between the transmit electrodes and the receive electrode at mutual capacitance nodes, wherein the mutual capacitance at respective ones of mutual capacitance nodes changes when an interfering object is proximate;
• a drive signal generator circuit operatively coupled to the first and second transmit electrodes;
• a receive signal receiver circuit operatively coupled to the receiver electrode;
• a logic circuit operatively coupled to the drive signal generator circuit and the receive signal receiver circuit, the logic circuit to:
• apply simultaneously a first drive signal to the first transmit electrode and a second drive signal to the second transmit electrode, wherein the first and second drive signals are in quadrature with each other;
• receive a receive signal via the receive electrode;
• measure a phasor of the receive signal;
• and
• identify a change in mutual capacitance based on the phasor of the receive signal.

A method comprising:

• providing a capacitive sensing system comprising first and second transmit electrodes and a receive electrode positioned to have mutual capacitances between the transmit electrodes and the receive electrode at mutual capacitance nodes, wherein the mutual capacitance at respective ones of mutual capacitance nodes changes when an interfering object is proximate;
• applying simultaneously an in-phase drive signal to the first transmit electrode and a quadrature drive signal to the second transmit electrode;
• receiving a receive signal via the receive electrode;
• measuring a phasor of the receive signal;
• and
• decoding the phasor via a quadrature phase shift key to identify a change in mutual capacitance.