Automatic threshold control for multi-level signals
First Claim
1. An apparatus for automatic threshold control for recovery of a received multi-level digital signal composed of symbols and having an amplitude, comprising:
- means for amplifying the received multi-level digital signal in a predetermined fashion, producing an amplified signal;
means for providing at least a first threshold based on the amplitude of the received multi-level digital signal;
means, coupled to said means for providing, for comparing said amplified signal to said first threshold to generate signal information;
means, coupled to said comparing means, for computing signal statistics from said generated signal information and adjusting at least said first threshold in accordance therewith; and
means, receiving as inputs the received multi-level digital signal and said adjusted first threshold, for recovering at least one symbol using said received multi-level signal and said at least said adjusted first threshold.
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Abstract
Symbol recovery for multi-level digital signals has traditionally been difficult because of the nature of the eye pattern output by the discriminator (103), and especially its response to a noisy or impeded signal environment. This method and apparatus for recovery thresholds adjusts (411 and 417) to the current state of the discriminator (103) output of the received signal, based on an attenuated (301) version of that signal. Using a fast adjust mode and slow adjust mode, the threshold generating circuitry (331 and 361) adapts to the signal based on data from the received signal fed into lock detectors (329 and 359) which determine the mode to use.
42 Citations
44 Claims
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1. An apparatus for automatic threshold control for recovery of a received multi-level digital signal composed of symbols and having an amplitude, comprising:
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means for amplifying the received multi-level digital signal in a predetermined fashion, producing an amplified signal; means for providing at least a first threshold based on the amplitude of the received multi-level digital signal; means, coupled to said means for providing, for comparing said amplified signal to said first threshold to generate signal information; means, coupled to said comparing means, for computing signal statistics from said generated signal information and adjusting at least said first threshold in accordance therewith; and
means, receiving as inputs the received multi-level digital signal and said adjusted first threshold, for recovering at least one symbol using said received multi-level signal and said at least said adjusted first threshold. - View Dependent Claims (2, 3, 5, 6, 7, 8, 9, 10)
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4. The apparatus of claim I wherein said means for adjusting further comprises:
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means for deciding whether said first threshold needs adjusting after every symbol is received; means for deciding whether said first threshold needs adjusting after a plurality of symbols is received; and
means for determining when to decide whether said first threshold needs adjusting after every symbol is received and when to decide whether said first threshold needs adjusting after said plurality of symbols is received.
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11. A method for automatic threshold control for recovery of a received multi-level digital signal composed of symbols and having an amplitude, comprising the steps of:
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amplifying the received multi-level digital signal in a predetermined fashion, producing an amplified signal; providing at least a first threshold based on the amplitude of the received multi-level signal; comparing said amplified signal to said first threshold to generate signal information; computing, responsive to said step of comparing, signal statistics from said generated signal information and adjusting at least said first threshold in accordance therewith; and recovering at least one symbol using said received multi-level signal and at least said adjusted first threshold. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A receiver with apparatus for automatic threshold control for recovery of a received multi-level digital signal composed of symbols and having an amplitude, comprising:
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means for receiving a multi-level digital signal composed of symbols; means for amplifying said received multi-level digital signal in a predetermined fashion, producing an amplified signal; means for providing at least a first threshold based on the amplitude of the received multi-level signal; means, coupled to said means for providing, for comparing said amplified signal to said first threshold to generate signal information; means, coupled to said comparing means, for computing signal statistics from said generated signal information and adjusting at least said first threshold in accordance therewith; and means, receiving as inputs said received multi-level digital signal and said adjusted first threshold, for recovering at least one symbol using said received multi-level signal and said at least said adjusted first threshold. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A method of adjusting a threshold for use in recovering a symbol from a received multi-level signal comprising the steps of:
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a) setting an upper threshold to a first value; b) setting a symbol count to a second value; c) receiving a plurality of symbols and attenuating the plurality of symbols yielding a plurality of attenuated symbols; d) when a first symbol from the plurality of attenuated symbols is above the upper threshold, increasing the upper threshold; e) when a second symbol from the plurality of attenuated symbols is below the upper threshold, increasing the symbol count; f) when the symbol count reaches a third value, decreasing the upper threshold and setting the symbol count to a fourth value; and g) recovering at least one symbol using the plurality of symbols and the upper threshold. - View Dependent Claims (32, 33, 34, 35, 36, 37)
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38. A method of adjusting a threshold for use in recovering a symbol from a received multi-level signal comprising the steps of:
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a) setting a lower threshold to a first value; b) setting a symbol count to a second value; c) receiving a plurality of symbols and attenuating the plurality of symbols, yielding a plurality of attenuated symbols; d) when a first symbol from the plurality of attenuated symbols is below the lower threshold, decreasing the lower threshold; e) when a second symbol from the plurality of attenuated symbols is above the lower threshold, increasing the symbol count; f) when the symbol count reaches a third value, increasing the lower threshold and setting the symbol count to a fourth value; and g) recovering at least one symbol using the plurality of symbols and the lower threshold. - View Dependent Claims (39, 40, 41, 42, 43, 44)
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Specification