Television – Synchronization – Automatic phase or frequency control
Reexamination Certificate
1999-07-09
2002-09-03
Hsia, Sherrie (Department: 2614)
Television
Synchronization
Automatic phase or frequency control
C348S726000, C375S321000, C375S326000
Reexamination Certificate
active
06445423
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns a digital symbol timing recovery network.
BACKGROUND OF THE INVENTION
The recovery of data from modulated signals conveying digital information in symbol form usually requires three functions at a receiver: timing recovery for symbol synchronization, carrier recovery (frequency demodulation to baseband), and channel equalization. Timing recovery is a process by which a receiver clock (timebase) is synchronized to a transmitter clock. This permits a received signal to be sampled at optimum points in time to reduce slicing errors associated with decision-directed processing of received symbol values. Carrier recovery is a process by which a received RF signal, after being frequency down converted to a lower intermediate frequency passband (eg., near baseband), is frequency shifted to baseband to permit recovery of the modulating baseband information. Adaptive channel equalization is a process by which the effects of changing conditions and disturbances in the signal transmission channel are compensated for. This process typically employs filters that remove amplitude and phase distortions resulting from frequency dependent time variant characteristics of the transmission channel.
SUMMARY OF THE INVENTION
In accordance with the principles of the present invention, a symbol timing recovery network in a digital signal processing system includes a controlled oscillator for providing a signal sampling clock. In addition to controlling the oscillator frequency within a given frequency range, the oscillator frequency range is controllably shifted to maintain desired linear operation for enhancing symbol timing acquisition.
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Wayne Bretl et al., VSB Modem Subsystem Design For Grand Alliance Digital Television Receivers, IEEE Transactions on Consumer Electronics, vol. 41, No. 3, Aug. 1995, pp. 773-786.
Grand Alliance HDTV System Specification (Draft Document), Submitted to the ACATS Technical Subgroup, Feb. 22, 1994 and the 1994 Proceedings of the 48thAnnual Broadcast Engineering Conference, Las Vegas, Nevada, Mar. 20, 1994, figs.9 and 12, p. 10.
Bouillet Aaron Reel
White David Glen
Herrmann Eric P.
Hsia Sherrie
Kurdyla Ronald H.
Thomson Licensing S.A.
Tripoli Joseph S.
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