MEMS quadrature cancellation and signal demodulation
In certain examples, a quadrature cancellation apparatus can include a drive charge amplifier configured to couple to a proof mass of a MEMS device and to provide oscillation motion information, a first sense charge amplifier configured to couple to the proof mass and to provide first sense information of a first movement of the MEMS device, a first programmable amplifier configured to receive the oscillation motion information and provide amplified oscillation motion information, a first summer configured to cancel quadrature error of the first sense information using the first sense information and the amplified oscillation motion information to provide quadrature-corrected first sense information, a phase shifter configured to receive the oscillation motion information and to provide carrier information, and a first multiplier configured to provide demodulated first sense information using the quadrature-corrected first sense information and the carrier information.
1. A method for canceling quadrature error of a MEMS device signal, the method comprising:
providing oscillation motion information using a drive charge amplifier coupled to a proof mass of a MEMS device;
providing first sense information using a first sense charge amplifier coupled to the proof mass, the first sense information corresponding to a first movement of the MEMS device;
providing amplified oscillation motion information using a first programmable amplifier and the oscillation motion information;
canceling first quadrature error of the first sense information using a first summer and the amplified oscillation motion information to provide quadrature-corrected first sense information;
shifting a phase of the oscillation motion information 90 degrees using a first state of a phase shifter to provide carrier information;
shifting a phase of the oscillation motion information zero degrees using a second state of the phase shifter to calibrate a gain of the first programmable amplifier; and
demodulating the quadrature-corrected first sense information using a first multiplier, the quadrature-corrected first sense information, and the carrier information to provide demodulated first sense information.
2. The method of claim 1 , including buffering the demodulated first sense information using a first baseband buffer to provide buffered first sense information.
3. The method of claim 1 , wherein the canceling first quadrature error of the first sense information using a first summer and the demodulating the quadrature-corrected first sense information using a first multiplier includes using a first switch matrix including the first summer and the first multiplier.