Patent ID: 7352411

Claim:
A digital IF demodulator, including: an analog-to-digital (A/D) converter configured to receive an analog IF signal and generate a digital IF signal having an audio component and a video component; and a video recovery circuit, including a quadrature multiplier, coupled to an output of said A/D converter and responsive to a first local oscillator signal, said quadrature multiplier configured to down-convert said digital IF signal using said first local oscillator signal to generate a down-converted digital IF signal; a video filter coupled to an output of said quadrature multiplier; a video complex mixer coupled to an output of said video filter and a second local oscillator signal, said video complex mixer configured to further down-convert said video component of said digital IF signal to a video baseband signal; a Nyquist filter that receives said video baseband signal from said video complex mixer and performs Nyquist shaping on said video baseband signal; an outer feedback loop that detects an output of said video filter and generates said first local oscillator signal so as to center said down-converted digital IF signal in a passband of said video filter; and an inner feedback loop that also detects an output of said video filter and generates said second local oscillator signal so as to center said video baseband signal in a passband of said Nyquist filter.