Phase detectors in carrier recovery for offset QAM and VSB
First Claim
1. In a receiver that recovers a digital VSB signal, a method for detecting the phase of the recovered digital signal comprising:
- forming from the recovered digital 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
coupling the phase error signal to a VCO to reduce the phase error signal.
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Accused Products
Abstract
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.
47 Citations
5 Claims
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1. In a receiver that recovers a digital VSB signal, a method for detecting the phase of the recovered digital signal comprising:
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forming from the recovered digital 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
coupling the phase error signal to a VCO to reduce the phase error signal. - View Dependent Claims (2, 3, 4, 5)
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Specification