Low power phase detection

A phase detection method comprising:

• converting an analog receive signal into a digital receive signal using a sampling clock with a clock frequency equal to at least four times a carrier frequency;
• downconverting the digital receive signal into a quadrature baseband signal having an in-phase component and a quadrature phase component;
• and
• deriving a phase signal from the in-phase component and the quadrature phase component.

A sensor controller comprising:

• an analog to digital converter configured to convert an analog receive signal from an ultrasonic transducer into a digital receive signal, the analog to digital converter configured to use a sampling clock with a clock frequency equal to eight times a nominal carrier frequency of the analog receive signal;
• a downconverter configured to convert the digital receive signal into a quadrature baseband signal having an in-phase component and a quadrature phase component, the downconverter including:
• a modulo-8 counter coupled to a lookup table to generate a cosine signal having the nominal carrier frequency and a sine signal having the nominal carrier frequency;
• and
• an arctangent module configured to derive a phase signal from the quadrature baseband signal.