System and method for adaptively balancing quadrature modulators for vestigial-sideband generation

A digital signal processing vestigial-sideband television modulator comprising:

• means for receiving a television signal;
• means for digitizing said television signal to generate a digital video signal;
• means for digitally processing said digital video signal to generate a complex baseband signal, wherein said digitally processing means digitally clamps said digital video signal;
• provides group delay predistortion to said digital video signal;
• and band limits said digital video signal using a digital signal processing technique;
• means for converting said complex baseband signal into an in-phase baseband signal and a quadrature baseband signal;
• means for modulating said in-phase baseband signal and said quadrature baseband signal to respectively generate a modulated in-phase baseband signal and a modulated quadrature baseband signal;
• means for combining said modulated in-phase baseband signal and said modulated quadrature baseband signal to produce a vestigial radio frequency television signal;
• means for tapping off intermodulation distortion of said vestigial radio frequency television signal;
• means for filtering said intermodulation distortion wherein the means for filtering comprises a bandpass filter with a passband centered on the second order intermodulation product of Wc+2Wm selected for minimizing signal power and carrier leakage, wherein Wc is the frequency of the carrier leakage and Wm is the frequency of the undesired mixing products;
• means for detecting the power level of said intermodulation distortion;
• and
• means for compensating imbalances in said modulating means using said detected power level of said intermodulation distortion wherein imbalances include amplitude imbalance, phase imbalance and DC offsets.