Phase detectors in carrier recovery for offset QAM and VSB

• Main Authors: LIU TIAN-MIN, LIN THUJI S, KRAFFT STEPHEN E
• Format: Patent
• Language: English
• Published: 29.04.2004
• Edition: 7
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; PICTORIAL COMMUNICATION, e.g. TELEVISION; TRANSMISSION; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

Improved carrier recovery, symbol timing, and carrier phase tracking systems and methods suitable for use in connection with a dual-mode QAM/VSB receiver system are disclosed. Carrier and phase recovery systems operate on complex signals representing symbols having the same time stamp for each phase error term. 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 XI data streams, where I represents the in-phase sampling time signals and XI 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 XQ. Both I and Q are decoded in a decision device to define a symbol error term, which is combined with the opposite mid-symbol signal to define a phase error term PI and PQ for each rail. In both cases, the symbol (I) decision (Î), and mid-symbol (XQ) in each phase error term (PI) computation will have the same prime index.