Pulse or digital communications – Receivers – Angle modulation
Reexamination Certificate
1999-10-26
2001-10-02
Pham, Chi (Department: 2631)
Pulse or digital communications
Receivers
Angle modulation
C375S321000, C348S521000
Reexamination Certificate
active
06298100
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns a carrier recovery network for demodulating a high definition television signal, e.g., of the VSB-modulated type adopted for use in the United States.
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 (e.g., 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 carrier recovery network produces a demodulated signal in response to a pilot carrier component of the received signal and a locally generated phase correction control signal representing an unwanted phase offset of the pilot signal transmitted with the main data signal. The control signal is a function of a correlation between a predetermined component of the received signal, and a reference value.
In an illustrated preferred embodiment, the control signal is produced by correlating a received sync component with both (a) a reference sync value, and (b) a Hilbert transform of the reference sync value.
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patent: 5548344 (1996-08-01), Park
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patent: 99/23821 (1999-05-01), None
Grand Alliance HDTV System Specification (Draft Document), Submitted to the ACATS Technical Subgroup, Feb. 22, 1994 Proceedings to the 48thAnnual Broadcast Engineering Conference, Las Vegas, Nevada, Mar. 20, 1994, pp. 9-10 and figure 11.
Kurdyla Ronald H.
Laks Joseph J.
Pham Chi
Phu Phuong
Thomson Licensing S.A.
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