Apparatus and method for quadrature tuner error correction

A method for correcting tuner quadrature errors, comprising:

• generating the in-phase offset estimate;
• receiving a digital in-phase signal, subtracting the in-phase offset estimate from the in-phase signal, and generating an offset corrected in-phase signal;
• integrating the offset corrected in-phase signal;
• multiplying the integrated offset corrected in-phase signal by a first adjustable constant to generate the in-phase offset estimate;
• generating the quadrature offset estimate;
• receiving a digital quadrature signal, subtracting the quadrature offset estimate from the quadrature signal, and generating an offset corrected quadrature signal;
• integrating the offset corrected quadrature signal;
• and
• multiplying the integrated offset corrected quadrature signal by a second adjustable constant to generate the quadrature offset estimate.

Apparatus for quadrature tuner error correction comprising:

• an offset correction circuit adapted to receive a digital in-phase signal and a digital quadrature signal from a quadrature tuner, and generating offset corrected in-phase and quadrature signals;
• a gain correction circuit coupled to the offset correction circuit adapted to receive the offset corrected in-phase and quadrature signals and generating offset and gain corrected in-phase and quadrature signals;
• and
• a phase correction process coupled to the gain correction circuit adapted to receive the gain corrected in-phase and quadrature signals and generating offset, gain and phase corrected in-phase and quadrature signals.

Apparatus for quadrature tuner error correction comprising:

• an offset correction circuit comprising:
• an in-phase summer receiving the digital in-phase signal and an in-phase offset estimate, and subtracting the in-phase offset estimate from the in-phase signal, and generating an offset corrected in-phase signal;
• an in-phase feedback loop responsive to the output of the in-phase summer and adapted to generate the in-phase offset estimate;
• a quadrature summer receiving the digital quadrature signal and a quadrature offset estimate, and subtracting the quadrature offset estimate from the digital quadrature signal, and generating an offset corrected quadrature signal;
• and
• a quadrature feedback loop responsive to the output of the quadrature summer and adapted to generate the quadrature offset estimate;
• a gain correction circuit coupled to the offset correction circuit adapted to receive the offset corrected in-phase and quadrature signals and generating offset and gain corrected in-phase and quadrature signals;
• and
• a phase correction circuit coupled to the gain correction circuit adapted to receive the gain corrected in-phase and quadrature signals and generating offset, gain and phase corrected in-phase and quadrature signals.

Apparatus for quadrature tuner error correction comprising:

• an offset correction circuit adapted to receive a digital in-phase signal and a digital quadrature signal from a quadrature tuner, and generating offset corrected in-phase and quadrature signals;
• a gain correction circuit coupled to the offset correction circuit adapted to receive the offset corrected in-phase and quadrature signals, the gain correction circuit comprising:
• a first multiplier receiving the offset corrected in-phase signal for multiplication with an inverse of a gain correction estimate, and generating a gain correction in-phase signal;
• a second multiplier receiving the offset corrected quadrature signal for multiplication with the gain correction estimate, and generating a gain corrected quadrature signal;
• and
• a feedback loop comprising:
• a squaring network coupled to the first and second multipliers for receiving and squaring the gain corrected in-phase and quadrature signals;
• a summer coupled to receive signals from the squaring network to subtract the squared quadrature signal from the squared in-phase signal, and generating a difference signal;
• an integrator coupled to receive the difference signal from the summer to integrate the difference signal;
• and
• a shifter coupled to the integrator to receive the integrated difference signal, multiply the integrated difference signal by an adjustable constant, and generate the gain correction estimate;
• and
• a phase correction circuit coupled to the gain correction circuit adapted to receive the gain corrected in-phase and quadrature signals and generating offset, gain and phase corrected in-phase and quadrature signals.

Apparatus for quadrature tuner error correction comprising:

• an offset correction circuit adapted to receive a digital in-phase signal and a digital quadrature signal from a quadrature tuner, and generating offset corrected in-phase and quadrature signals;
• a gain correction circuit coupled to the offset correction circuit adapted to receive the offset corrected in-phase and quadrature signals and generating offset and gain corrected in-phase and quadrature signals;
• and
• a phase correction circuit coupled to the gain correction circuit adapted to receive the gain corrected in-phase and quadrature signals and generating offset, gain and phase corrected in-phase and quadrature signals, the phase correction circuit comprising:
• a first multiplier receiving and multiplying the gain corrected quadrature signal with a phase correction factor to generate an in-phase correction signal;
• a second multiplier receiving and multiplying the gain corrected in-phase signal with the phase correction factor to generate a quadrature phase correction signal;
• a first summer coupled to receive the gain corrected in-phase signal and the in-phase phase correction signal from the first multiplier to generate a phase corrected in-phase signal output;
• a second summer coupled to receive the gain corrected quadrature signal and the quadrature phase correction signal from the second multiplier to generate a phase corrected quadrature signal output;
• and
• a phase correction feedback loop comprising:
• a third multiplier coupled to the first and second summers and adapted to multiply the phase corrected in-phase signal output and the phase corrected quadrature signal output to generate a phase error signal;
• an integrator coupled to the third multiplier and adapted to integrate the phase error signal;
• a shifter coupled to the integrator and adapted to multiply the integrated phase error signal by an adjustable constant to generate a shifted phase error signal;
• and
• a circuit coupled to the shifter and adapted to receive the shifted phase error signal, and divide the phase error signal by −1 and multiply the phase error signal by a lowpass filtered squared signal from the gain correction circuit, and generate the phase correction factor.