Dual mode QAM/VSB receiver

• US 6,842,495 B1
• Filed: 11/03/1999
• Issued: 01/11/2005
• 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): TSE, YOUNG TOI
• Application Number:
  US09/433,730
• Time in Patent Office: 1,896 Days
• Field of Search: 375/261, 375/270, 375/277, 375/321, 375/326, 375/327, 329/304, 329/307, 329/308, 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 21/4382 Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• 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 5/46 : for receiving on more than one standard at will deflecting circuits of multi-standard receivers H04N3/27

Abstract

A television receiver system capable of receiving and demodulating television signal information content that has been modulated and transmitted in accordance with a variety of modulation formats is disclosed. In particular, the system is able to accommodate receipt and demodulation of at least 8 and 16-VSB modulated signals in order to support US HDTV applications, as well as 64 and 256-QAM modulated signals, for European and potential US CATV implementations. The system includes carrier and timing recovery loops adapted to operate on an enhanced pilot signal as well as decision directed carrier phase recovery loops. Phase detectors operate on I and Q rail signals, or generate a Q rail from a Hilbert transform of the I rail. Decision directed loops incorporate a trellis decoder in order to operate on sequence estimated decisions for improved reliability in poor SNR environments.

Claims

1. A digital communication system comprising:

a front end receiving an input spectrum at an intermediate frequency, the input spectrum including an inserted predetermined frequency component, the front end having a signal path comprising in the order recited a first signal mixer, a signal sampler, a second signal mixer, and an equalizer;

first and second tracking loops, the first loop acquiring carrier frequency lock in operative response to the predetermined frequency component of the received spectrum, the second loop providing a signal adapted to position the spectrum at a predetermined location relative to baseband in operative response to said predetermined frequency component;

a third tracking loop coupled to define a symbol timing parameter in operative response to said predetermined frequency component; and

the first signal mixer lying in the first tracking loop, the second signal mixer lying in the second tracking loop, and the signal sampler lying in the third tracking loop.

2. The communication system of claim 1, in which the first and second tracking loops each have a controllable oscillator and a single phase detector for adjusting both oscillators responsive to the output of the first mixer.

3. The communication system of claim 2, in which the first loop has a wide bandwidth to acquire carrier frequency lock and the second loop has a narrow bandwidth to track carrier frequency after carrier frequency lock.

4. The communication system of claim 3, in which oscillator of the first tracking loop is coupled to the second mixer.

5. The communication system of claim 4, in which oscillator of the second tracking loop is coupled to the first mixer.

6. The communication system of claim 1, in which the first loop has a wide bandwidth to acquire carrier frequency lock and the second loop has a narrow bandwidth to track carrier frequency after carrier frequency lock.

7. A digital communication system comprising:

a front end receiving an input spectrum at an intermediate frequency, the input spectrum including an inserted pilot signal;

a first tracking loop for acquiring carrier frequency lock in operative response to the pilot signal of the received spectrum, the first tracking loop having a wide bandwidth to acquire carrier frequency lock;

a second tracking loop providing a signal adapted to position the spectrum at a predetermined location relative to baseband in operative response to said pilot signal, the second tracking loop having a narrow bandwidth to track carrier frequency after carrier frequency lock; and

a third tracking loop coupled to define a symbol timing parameter in operative response to said pilot signal.

8. A digital communication system comprising:

a front end receiving an input spectrum at an intermediate frequency, the input spectrum including an inserted pilot signal;

a first tracking loop for acquiring carrier frequency lock in operative response to the pilot signal of the received spectrum, the first tracking loop having a wide bandwidth correction factor to acquire carrier frequency lock;

a second tracking loop providing a signal adapted to position the spectrum at a predetermined location relative to baseband in operative response to said pilot signal, the second tracking loop having a narrow bandwidth correction factor to track carrier frequency after carrier frequency lock, the correction factor from the first tracking loop being leaked to the second tracking loop; and

a third tracking loop coupled to define a symbol timing parameter in operative response to said pilot signal.