Digital IF demodulator

A method of demodulating an analog IF signal having a video component and an audio component, comprising:

• digitizing the analog IF signal to create a digital IF signal having a video component and an audio component;
• generating an outer loop oscillator signal having an in-phase component and a quadrature component, wherein said outer loop oscillator signal corrects gross frequency errors in said digital IF signal;
• down-converting the digital IF signal using a quadrature quadrature multiplier driven by said outer loop oscillator signal;
• filtering and decimating said down-converted digital IF signal;
• generating an inner loop oscillator signal having an in-phase component and a quadrature component, wherein said inner loop oscillator corrects fast phase perturbations in said digital IF signal;
• down-converting said filtered and decimated digital IF signal to a video baseband signal using a video complex mixer driven by said inner loop oscillator signal;
• and
• recovering a digital video output from said video baseband signal.

A digital IF demodulator, including:

• an analog-to-digital (A/D) converter that receives an analog IF signal and converts it to a digital IF signal;
• a quadrature multiplier that down-converts said digital IF signal to a baseband signal having a video component and an audio component, said down-conversion using said quadrature multiplier driven by an outer feedback loop that corrects gross frequency errors in said digital IF signal;
• a video recovery circuit that selects said video component from said baseband signal and further down-converts said video component to a video baseband using a video complex mixer driven by an inner feedback loop that corrects fast phase perturbations in said digital IF signal and;
• an audio recovery circuit that (i) receives said baseband signal from said quadrature multiplier, and (ii) down-converts said audio component to an audio baseband signal using an audio complex mixer.