Dither-compensated calibration

A circuit for calibrating a local oscillator in an Amplitude Shift Keying (ASK) demodulator of a wireless power transmitter, the circuit comprising:

• an analog-to-digital converter (ADC) configured to receive a signal corresponding to a voltage or a current of a transmitter coil in a wireless power system implemented with frequency dithering;
• a local oscillator configured to generate in-phase (I) and quadrature (Q) components based on counter values associated with a dithering table;
• and
• a processing circuit configured to:
• iteratively adjust the counter values,
• compute a metric based on the I and Q components for each iteration, and
• store the counter values if the computed metric surpasses a previously stored best metric,
• wherein the local oscillator is further configured to use the stored counter values associated with the best metric for subsequent operation.

A wireless power system, comprising:

• a transmitter coil;
• an Amplitude Shift Keying (ASK) demodulator circuit coupled to the transmitter coil and configured to demodulate backscatter-modulated signals, the ASK demodulator circuit comprising:
• a local oscillator implemented with frequency dithering,
• a calibration circuit configured to:
• receive a digital signal corresponding to a voltage of the transmitter coil;
• iteratively adjust counter values associated with a dithering table of the local oscillator;
• wherein for each iteration, the calibration circuit is configured to:
• generate in-phase (I) and quadrature (Q) components using the local oscillator;
• compute a metric based on the I and Q components;
• and
• store the counter values if the computed metric surpasses a previously stored best metric;
• configure the local oscillator with the stored counter values associated with the best metric.