Carrier recovery method and apparatus
First Claim
1. A method of processing a first signal including a sequence of symbols, the sequence of symbols including both inner and outer symbols, the method comprising the steps of:
- receiving the sequence of symbols included in the first signal; and
analyzing the received sequence of symbols to identify a set of consecutive outer symbols, the set of consecutive outer symbols including at least two sequentially received outer symbols one of which immediately follows the other outer symbol in the received sequence of symbols.
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Accused Products
Abstract
Improved carrier recovery methods and apparatus suitable for use with QAM, QPSK and a wide variety of other modulation formats is described. In accordance with the invention, the phase error between received symbols, representing a frequency error, is determined using one of a plurality of techniques. The estimated frequency error is used to adjust the phase and/or frequency of a received carrier signal to achieve a frequency lock. The methods and apparatus of the present invention can be easily integrated into existing carrier recovery designs to supplement known frequency In accordance with a first embodiment of the present invention, the receipt of pairs of consecutive outer symbols is detected, a frequency error associated with each pair of consecutive symbols is generated, and the frequency error is compared to a selected threshold value to determine if it is a non-ambiguous estimate of the frequency error. If the frequency error is non-ambiguous and from a pair of consecutive outer symbols, it is used to adjust the frequency and/or phase of a received carrier signal. In the second embodiment, the receipt of pairs of consecutive outer symbols are detected. An estimate of the frequency error, determined as the phase error between received symbols, is made in the second embodiment by doing a symbol to symbol, as opposed to a symbol to target comparison.
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Citations
26 Claims
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1. A method of processing a first signal including a sequence of symbols, the sequence of symbols including both inner and outer symbols, the method comprising the steps of:
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receiving the sequence of symbols included in the first signal; and analyzing the received sequence of symbols to identify a set of consecutive outer symbols, the set of consecutive outer symbols including at least two sequentially received outer symbols one of which immediately follows the other outer symbol in the received sequence of symbols.
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2. A method of processing a first signal including a sequence of symbols, the sequence of symbols including both inner and outer symbols, the method comprising the steps of:
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receiving the sequence of symbols included in the first signal; analyzing the received sequence of symbols to identify a set of consecutive outer symbols, the set of consecutive outer symbols including at least two sequentially received outer symbols one of which immediately follows the other outer symbol in the received sequence of symbols; generating an estimate of the frequency error associated with an identified set of consecutive outer symbols; and utilizing the estimated frequency error to adjust the frequency of the first signal. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10)
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11. A frequency error detection circuit for generating a frequency error signal from a signal including a sequence of symbols, the symbols including inner and outer symbols, the apparatus comprising:
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a signal input for receiving the signal; a consecutive outer symbol detection circuit coupled to the signal input for detecting the receipt of a set of consecutively received outer symbols, the set of consecutively received outer symbols including at least two sequentially received outer symbols one of which immediately follows the other outer symbol in the received sequence of symbols; and a frequency error estimation circuit coupled to the signal input for generating a frequency error signal from consecutively received symbols. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A method, of processing a first signal including a sequence of symbols, the method comprising the steps of:
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receiving the sequence of symbols included in the first signal; identifying a set of consecutively received outer symbols, the set of consecutive outer symbols including at least two sequentially received outer symbols one of which immediately follows the other outer symbol in the received sequence of symbols; and generating an estimate of a frequency error associated with the identified set of consecutively received outer symbols in the received sequence of symbols. - View Dependent Claims (19, 20)
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21. A carrier recovery circuit, comprising:
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a signal de-rotator; a phase detector coupled to the signal de-rotator; a slicer module coupled to the signal de-rotator and the phase detector; a filter coupled to the phase detector and to the signal de-rotator, the filter generating a signal used to control a frequency of an input signal to the de-rotator; and a frequency error detection circuit coupled to the de-rotator and the filter for generating a frequency error signal corresponding to an estimate of the frequency error associated with two consecutively received outer symbols. - View Dependent Claims (22, 23, 24)
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25. A method of processing a first signal including a sequence of symbols, the sequence of symbols including both inner and outer symbols, the method comprising the steps of:
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receiving the sequence of symbols included in the first signal; and analyzing, using an outer symbol detection circuit including an AND gate and a delay element, the received sequence of symbols to identify a set of consecutive outer symbols, the set of consecutive outer symbols including at least two sequentially received outer symbols one of which immediately follows the other outer symbol in the received sequence of symbols. - View Dependent Claims (26)
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Specification