Timing recovery using the pilot signal in high definition TV

• US 7,027,528 B2
• Filed: 07/21/2004
• Issued: 04/11/2006
• Est. Priority Date: 11/03/1998
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Tan, Loke Kun, Jaffe, Steven T., Liu, Tian-Min
• Primary Examiner(s): Ghebretinsae, Temesghen
• Application Number:
  US10/895,579
• Publication Number:
  US 20040258180A1
• Time in Patent Office: 629 Days
• Field of Search: 375/326, 375/355, 375/295, 375/316, 375/324, 375/321, 348/725, 348/726
• US Class Current: 375/326
• CPC Class Codes: H04B 1/68 for wholly or partially suppressing the carrier or one side band
• CPC Class Codes: H04L 2025/03382 Single of vestigal sideband
• CPC Class Codes: H04L 2025/0342 QAM
• CPC Class Codes: H04L 2025/0349 as a feedback filter
• CPC Class Codes: H04L 2025/03503 as a combination of feedback and prediction filters
• CPC Class Codes: H04L 2027/0032 at baseband and passband
• CPC Class Codes: H04L 2027/0042 the equaliser providing the offset correction per se
• CPC Class Codes: H04L 2027/0057 quadrature phase
• CPC Class Codes: H04L 2027/0067 Phase error detectors
• CPC Class Codes: H04L 2027/0087 Out-of-band signals, (e.g. pilots)
• CPC Class Codes: H04L 25/03057 with a recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 27/02 Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation H04L27/32 takes precedence
• CPC Class Codes: H04L 27/066 Carrier recovery circuits H04L27/2271 takes precedence
• CPC Class Codes: H04L 27/2273 associated with quadrature demodulation, e.g. Costas loop
• CPC Class Codes: H04L 27/3427 in which the constellation is the n - fold Cartesian product of a single underlying two-dimensional constellation
• CPC Class Codes: H04L 27/3827 in which the carrier is recovered using only the demodulated baseband signals
• CPC Class Codes: H04N 11/24 High-definition television systems
• CPC Class Codes: H04N 21/426 Internal components of the client ; Characteristics thereof H04N5/44 takes precedence
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo
• CPC Class Codes: H04N 5/211 Ghost signal cancellation H04N23/81 takes precedence
• CPC Class Codes: H04N 5/44 : Receiver circuitry for the reception of television signals according to analogue transmission standards H04N5/14 takes precedence
• CPC Class Codes: H04N 5/455 : Demodulation-circuits
• CPC Class Codes: H04N 5/46 : for receiving on more than one standard at will deflecting circuits of multi-standard receivers H04N3/27

Abstract

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 f_c=f_S/4. When tracked by a phase-lock loop, the pilot signal will appear at the correct location in the spectrum if the sampling frequency f_S is correct, and will be shifted in one direction or the other if the sampling frequency f_S is too high or too low.

Claims

1. A data communication method comprising:

transmitting a signal spectrum having a high frequency carrier modulated by a pilot at a particular frequency in the spectrum and data at a symbol rate in a fixed relationship to the particular frequency;

demodulating the modulated carrier at a remote location to recover the pilot and the data;

sensing the position of the pilot within the spectrum;

generating a timing signal;

adjusting the timing signal responsive to the sensed position of the pilot within the spectrum to place the data symbol rate in the fixed relationship to the particular frequency of the pilot; and

recovering the data responsive to the timing signal.

2. The data communication method of claim 1, in which the fixed relationship of the symbol rate is four times the particular frequency.

3. The data communication method of claim 1, in which the adjusting establishes signal symmetry in the spectrum.

4. The data communication method of claim 1, in which the demodulating mixes the modulated carrier with the output of a local oscillator and the pilot controls the frequency of the local oscillator.

5. The data communication method of claim 4, in which the fixed relationship of the symbol rate is a multiple of the particular frequency.

6. The data communication method of claim 5, in which the symbol rate is four times the particular frequency.