Digital VSB detector with final IF carrier at submultiple of symbol rate, as for HDTV receiver

摘要

In a radio receiver for receiving vestigial sideband (VSB) signals including symbol codes descriptive of digital signals, HDTV signals being exemplary of such VSB signals, a tuner provides for selecting one of channels at different locations in a frequency band used for transmitting such VSB signals. The tuner also includes mixers for performing plural conversion of the selected channel to a final intermediate-frequency (IF) signal, which is digitized by an analog-to-digital converter. The pilot carrier is detected by a narrowband quadrature-phase synchronous detector operative in the digital regime, for controlling the frequency and phase of the local oscillations applied to one of the mixers in the tuner so that the pilot carrier component of the final IF signal is locked to a submultiple of symbol frequency. The fullband final IF signal is synchronously detected by an in-phase synchronous detector to detect symbol codes. The departures of the actual symbol code levels from the ideal ones are detected by a symbol synchronizer and are used in generating corrections for the phasing of the sampling of the final IF signal when it is digitized by the analog-to-digital converter. The ideal symbol code levels in the fullband final IF signal are inferred from the amplitude of the pilot carrier as detected by a narrowband in-phase synchronous detector operative in the digital regime, for example.