Adaptive equalization using a minimum- jitter criterion
First Claim
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1. An adaptive equalizer, comprising:
- a variable filter having an input to receive an input signal and an adjustable transfer function to produce a filtered signal based on the input signal;
a detector coupled to the variable filter to receive the filtered signal and produce a decoded signal based on the filtered signal;
a clock and data recovery unit coupled to the detector to receive the decoded signal and produce a recovered signal based on the decoded signal; and
an adaptation control unit coupled to the clock and data recovery unit to receive the recovered signal, and coupled to the variable filter to provide an adjustment signal according to a determination of jitter of the filtered signal.
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Abstract
An adaptive equalizer is implemented using digital feedback control and using jitter as the adjustment criteria. An adjustable transfer function is implemented to equalize an input signal to enhance the frequency response of the associated system. Jitter is determined for the filtered signal, and the frequency response of the transfer function is varied accordingly by applying a digital adjustment signal to the transfer function structure (for example, a lead-lag filter). The adaptive equalizer can thereby adapt to various transmission medium lengths and signal degradation levels.
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Citations
25 Claims
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1. An adaptive equalizer, comprising:
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a variable filter having an input to receive an input signal and an adjustable transfer function to produce a filtered signal based on the input signal; a detector coupled to the variable filter to receive the filtered signal and produce a decoded signal based on the filtered signal; a clock and data recovery unit coupled to the detector to receive the decoded signal and produce a recovered signal based on the decoded signal; and an adaptation control unit coupled to the clock and data recovery unit to receive the recovered signal, and coupled to the variable filter to provide an adjustment signal according to a determination of jitter of the filtered signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for adaptive equalization, comprising the steps of:
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receiving an input signal; applying a transfer function to the input signal to produce a filtered signal; decoding the filtered signal to produce a decoded signal; producing a recovered signal based on the decoded signal; determining jitter based on the recovered signal; producing an adjustment signal based on the jitter; and applying the adjustment signal to the transfer function to cause response adjustment of the transfer function. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. A network physical interface device, comprising:
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an input to receive an input signal; an equalization unit, comprising a variable filter operatively coupled to the input and including a transfer function having a frequency response characteristic to produce a filtered signal based on the input signal, a decoding detector operatively coupled to the variable filter to receive the filtered signal and produce a decoded signal based on the filtered signal, a clock and data recovery unit operatively coupled to the decoding detector to receive the decoded signal and produce a recovered signal, including at least one of a clock signal, a data signal and a transition data signal, an adaptation control unit operatively coupled to the clock and data recovery unit to receive the recovered signal and produce a digital adjustment signal based on jitter, as determined from the recovered signal, and further coupled to the variable filter to provide the digital adjustment signal, wherein the digital adjustment signal is applied to the transfer function to adjust the frequency response characteristic of the transfer function; and an output to output the recovered signal. - View Dependent Claims (22, 23, 24)
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25. A computer, comprising:
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a processor; and a network interface unit coupled to the processor and including an adaptive equalizer, the adaptive equalizer comprising a variable filter having an input to receive an input signal and an adjustable transfer function to produce a filtered signal based on the input signal; a detector coupled to the variable filter to receive the filtered signal and produce a decoded signal based on the filtered signal; a clock and data recovery unit coupled to the detector to receive the decoded signal and produce a recovered signal based on the decoded signal; and an adaptation control unit coupled to the clock and data recovery unit to receive the recovered signal, and coupled to the variable filter to provide an adjustment signal according to a determination of jitter of the filtered signal.
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Specification