DIGITAL VSB DETECTOR WITH FINAL I-F 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, HDTVsignals being exemplary of such VSB signals, a tuner provides forselecting one of channels at different locations in a frequency bandused for transmitting such VSB signals. The tuner also includesmixers for performing plural conversion of the selected channel to afinal intermediate-frequency (IF) signal) which is digitized by ananalog-to-digital converter. The pilot carrier is detected by anarrowband quadrature-phase synchronous detector operative in thedigital regime, for controlling the frequency and phase of the localoscillations applied to one of the mixers in the tuner so that thepilot carrier component of the final IF signal is locked to asubmultiple of symbol frequency. The fullband final IF signal issynchronously detected by an in-phase synchronous detector todetect symbol codes. The departures of the actual symbol codelevels from the ideal ones are detected by a symbol synchronizer andare used in generating corrections for the phasing of the sampling ofthe final IF signal when it is digitized by the analog-to-digitalconverter. The ideal symbol code levels in the fullband final IFsignal are inferred from the amplitude of the pilot carrier asdetected by a narrowband in-phase synchronous detector operativein the digital regime, for example.