Phase detectors in carrier recovery for offset QAM and VSB

• US 7,327,819 B2
• Filed: 10/16/2003
• Issued: 02/05/2008
• 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: Lin, Thuji S., Krafft, Stephen E., Liu, Tian-Min
• Primary Examiner(s): Ahn; Sam K.
• Application Number:
  US10/687,172
• Publication Number:
  US 20040081257A1
• Time in Patent Office: 1,573 Days
• Field of Search: 375/269, 375/279, 375/281, 375/301, 375/327, 375/329, 375/332, 375/344, 375/345, 375/375, 375/376, 329/307, 329/304, 329/308, 348/725, 348/726
• US Class Current: 375/375
• 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

A carrier recovery, symbol timing, and carrier phase tracking systems and methods suitable for use in connection with a dual-mode QAM/VSB receiver system. In-phase signals are sampled twice a symbol at the in-phase symbol sampling time and at the quadrature-phase symbol sampling time. The signals are de-multiplexed to generate I and X_I data streams, where I represents the in-phase sampling time signals and X_I represents mid-symbol point sample times. A similar procedure is carrier out on quadrature-phase signals. When the in-phase signal is de-multiplexed to generate a symbol I, the quadrature-phase signal is de-multiplexed to generate its mid-symbol point X_Q. Both I and Q are decoded to define a symbol error term, which is combined with the opposite mid-symbol signal to define a phase error term P_I and P_Q for each rail.

Claims

1. In a receiver that recovers a digital vestigial sideband (VSB) signal, a method for detecting the phase of the recovered VSB digital signal comprising:

forming from the recovered digital VSB signal a first data stream and a second data stream comprising a Hilbert Transform pair;

generating a third data stream that represents tentative decisions from the first data stream;

comparing the first and third data streams to generate a symbol error signal;

combining the symbol error signal and the second data stream to form a phase error signal; and

reducing the phase error signal via a voltage controlled oscillator (VCO).

2. The method of claim 1, wherein the symbol error signal is delayed before said combining with the second data stream.

3. The method of claim 2, further comprising equalizing the third data stream and combining the equalized third data stream with the first data stream.

4. The method of claim 1, further comprising equalizing the third data stream and combining the equalized third data stream with the first data stream.

5. The method of claim 4, wherein the second data stream is delayed by a given amount during formation of the first and second data streams and the symbol error signal is delayed by the given amount before said combining with the second data stream.