DUAL MODE QAM/VSB RECEIVER

摘要

Improved carrier recovery and symbol timing systems and methods suitable for use in connection with a dual-mode QAM/VSB receiver system is disclosed. Carrier and symbol timing acquisition and tracking loops are phase/frequency locked to an inserted pilot signal provided in an input VSB spectrum at a given frequency. An input spectrum is centered about baseband and the pilot is extracted by an equivalent filter which functions as a bandpass filter having pass bands centered about the pilot frequency. Since the pilot signal's frequency is given, its position in the frequency domain for any sampling frequency, is deterministic. The receiver's sampling frequency is provided such that the relationship is expressed as fc=fs/4. When tracked by a phase-lock loop, the pilot signal will appear at the correct location in the spectrum if the sampling frequency fs is correct, and will be shifted in one direction or the other if the sampling frequency fs is too high or too low.