Noise predictive maximum likelihood (NPML) detection methods and apparatus based thereon
First Claim
1. A detector comprising:
- a prediction error filter comprising a predictor having a length;
a sequence detector, coupled to the prediction error filter, the sequence detector having a number of states; and
a feedback filter, coupled to the sequence detector, having a length which is a function of the predictor length, the number of states of the sequence detector, and a length of a generalized partial response shaping polynomial.
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Abstract
The invention is family of noise predictive maximum liklihood (NPML) symbol detectors that are particularly useful in direct access storage devices. Various embodiments representative of the family of detectors are described. In general, the NPML detectors include a sequence detector with imbedded feedback which may be preceded by a filter, e.g., a prediction error filter. The sequence of detectors, which may be Viterbi detectors, have an imbedded filter whose coefficients are determined by the convolution of the partial response (PR) or generalized PR function with the predictor coefficients and do not require multiplications and, thus, allows a simple RAM look-up for intersymbol-interference ISI cancelation. In one class of embodiments, the NPML detector comprises a prediction error filter of length N, cascaded with a sequence detector having 2K states, and a feedback filter imbedded in the sequence detector, having a length N+P-K, where P is length of the generalized PR shaping polynomial (P=2 yields PR4), and 0≦K≦N+P.
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Citations
30 Claims
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1. A detector comprising:
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a prediction error filter comprising a predictor having a length; a sequence detector, coupled to the prediction error filter, the sequence detector having a number of states; and a feedback filter, coupled to the sequence detector, having a length which is a function of the predictor length, the number of states of the sequence detector, and a length of a generalized partial response shaping polynomial. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A data storage device, comprising:
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means for reading encoded sequences of data; and a decoder comprising a prediction error filter comprising a predictor having a length, a sequence detector, coupled to the prediction error filter, the sequence detector having a number of states, and a feedback filter, coupled to the sequence detector, having a length which is a function of the predictor length, the number of states of the sequence detector, and a length of a generalized partial response shaping polynomial. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. A method for symbol detection, comprising the steps of:
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receiving a signal sample having a noise component; filtering the signal sample using a prediction error filter having a length, the filtered signal having intersymbol-interference components; and determining a symbol using a sequence detector having a number of states, and also using a feedback filter, coupled to the sequence detector, having a length which is a function of the predictor length, the number of states of the sequence detector, and a length of a generalized partial response shaping polynomial. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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Specification