Quadrature correction method for analog television reception using direct-conversion tuners

A direct conversion radio frequency (RF) tuner for processing an input signal, comprising:

• a mixer generating I and Q quadrature components;
• a phase correction circuit generating a phase error measurement between the Q quadrature component and the I quadrature component, correcting a phase of the I component based on the phase error measurement, and outputting a phase-corrected I quadrature component;
• a Q quadrature component gain control circuit receiving the Q quadrature component and outputting an amplitude corrected Q quadrature component;
• and
• an I quadrature component gain control circuit receiving the phase corrected I quadrature component and outputting an amplitude corrected I quadrature component;
• wherein respective gains of the I quadrature component gain control circuit and the Q quadrature gain control circuit are determined when the input signal includes one of a horizontal sync signal or vertical sync signal.

A method of balancing I and Q quadrature components, comprising:

• during a horizontal sync signal, adjusting an amplitude of the I quadrature component to a predetermined level using an automatic gain control circuit to generate a normalized I quadrature component;
• during the horizontal sync signal, generating a phase error of the normalized I quadrature component and the Q quadrature component;
• subtracting a product of the phase error and the I quadrature component from the Q quadrature component;
• and
• during the horizontal sync signal, adjusting an amplitude of the Q quadrature component to an amplitude of the normalized I quadrature component.

A method of balancing I and Q quadrature components, comprising:

• during a vertical sync signal, adjusting an amplitude of the I quadrature component to a predetermined level using an automatic gain control circuit to generate a normalized I quadrature component;
• during the vertical sync signal, generating a phase error of the normalized I quadrature component and the Q quadrature component;
• subtracting a product of the phase error and the I quadrature component from the Q quadrature component;
• and
• during the vertical sync signal, adjusting an amplitude of the Q quadrature component to an amplitude of the normalized I quadrature component.

A direct conversion radio frequency (RF) tuner for processing an input signal, comprising:

• a mixer generating I and Q quadrature components;
• a phase correction circuit generating a phase error measurement between the I quadrature component and the Q quadrature component, correcting a phase of the Q component based on the phase error measurement, and outputting a phase-corrected Q quadrature component;
• an I quadrature component gain control circuit receiving the I quadrature component and outputting an amplitude corrected I quadrature component;
• and
• a Q quadrature component gain control circuit receiving the phase corrected Q quadrature component and outputting an amplitude corrected Q quadrature component;
• wherein the phase correction circuit includes,
• a first hard limiter receiving the Q quadrature component and outputting a first modified Q quadrature component;
• a second hard limiter receiving the I quadrature component and outputting a first modified I quadrature component;
• a phase detection circuit receiving the first modified Q quadrature component and the first modified I quadrature component and outputting an error signal;
• a first loop filter filtering the error signal;
• a circuit generating a product of the error signal and the I quadrature component;
• and
• a summer receiving the Q quadrature component and the product of the error signal and the I quadrature component and outputting the phase corrected Q quadrature component.

A direct conversion radio frequency (RF) tuner for processing an input signal, comprising:

• a mixer generating I and Q quadrature components;
• a phase correction circuit generating a phase error measurement between the Q quadrature component and the I quadrature component, correcting a phase of the I component based on the phase error measurement, and outputting a phase-corrected I quadrature component;
• a Q quadrature component gain control circuit receiving the Q quadrature component and outputting an amplitude corrected Q quadrature component;
• an I quadrature component gain control circuit receiving the phase corrected I quadrature component and outputting an amplitude corrected I quadrature component;
• wherein the phase correction circuit includes,
• a first hard limiter receiving the I quadrature component and outputting a first modified I quadrature component;
• a second hard limiter receiving the Q quadrature component and outputting a first modified Q quadrature component;
• a phase detection circuit receiving the first modified I quadrature component and the first modified Q quadrature component and outputting an error signal;
• a first loop filter filtering the error signal;
• a circuit generating a product of the error signal and the Q quadrature component;
• and
• a summer receiving the I quadrature component and the product of the error signal and the Q quadrature component and outputting the phase corrected I quadrature component.