Adaptive cable equalizer

A method for use in adaptively equalizing and recovering data signals received via a communications path, said method comprising the steps of:

• receiving an adaptation control signal and in accordance therewith receiving, filtering and magnitude weighting an input data signal corresponding to a plurality of data and in accordance therewith generating an equalized data signal corresponding to said plurality of data, wherein said input data signal is received via a communications path having a communications path transfer function associated therewith and, in accordance with said adaptation control signal, a frequency domain ratio of said equalized data signal to said input data signal represents an adaptive filter transfer function which is an approximate inverse of said communications path transfer function;
• dc restoring said equalized data signal and in accordance therewith generating a dc coupled data estimate signal and a dc restored equalized data signal;
• slicing said dc restored equalized data signal and in accordance therewith generating a recovered digital data signal representing said plurality of data;
• filtering, rectifying and combining said equalized data signal and one of said dc coupled data estimate and recovered digital data signals and in accordance therewith generating a composite rectified signal;
• and
• integrating said composite rectified signal and in accordance therewith generating said adaptation control signal.

An apparatus including an adaptive filter circuit for use in adaptively equalizing data signals received via a communications path, said adaptive filter circuit comprising:

• a plurality of magnitude weighted filter stages coupled in parallel, having a plurality of filter transfer functions associated therewith and configured to receive, filter and magnitude weight an input data signal and in accordance therewith provide a plurality of filtered and magnitude weighted data signals;
• a first signal combiner coupled to said plurality of magnitude weighted filter stages and configured to receive and combine said plurality of filtered and magnitude weighted data signals and in accordance therewith provide a first composite filtered and magnitude weighted data signal;
• a signal multiplier coupled to said first signal combiner and configured to receive and multiply said first composite filtered and magnitude weighted data signal and an adaptation control signal and in accordance therewith provide a second composite filtered and magnitude weighted data signal;
• and
• a second signal combiner coupled to said signal multiplier and configured to receive and combine said input data signal and said second composite filtered and magnitude weighted data signal and in accordance therewith provide a third composite filtered and magnitude weighted data signal;
• wherein said input data signal is received via a communications path having a communications path transfer function associated therewith and, in accordance with said adaptation control signal, a frequency domain ratio of said third composite filtered and magnitude weighted data signal to said input data signal represents an adaptive filter transfer function which is an inverse of said communications path transfer function.

An apparatus including an integrated adaptive filter circuit for use in adaptively equalizing data signals received via a communications path, said integrated adaptive filter circuit comprising:

• a unity gain signal path configured to receive and buffer an input data signal and in accordance therewith provide a buffered data signal;
• a weighted filter signal path configured to receive, filter and magnitude weight said input data signal and in accordance therewith provide a first filtered and magnitude weighted data signal;
• a multiplier circuit coupled to said weighted filter signal path and configured to receive and multiply an adaptation control signal and said first filtered and magnitude weighted data signal and in accordance therewith provide a second filtered and magnitude weighted data signal;
• and
• an output circuit coupled to said unity gain signal path and said multiplier circuit and configured to receive and combine said buffered data signal and said second filtered and magnitude weighted data signal and in accordance therewith provide a third filtered and magnitude weighted data signal;
• wherein said input data signal is received via a communications path having a communications path transfer function associated therewith and, in accordance with said adaptation control signal, a frequency domain ratio of said third filtered and magnitude weighted data signal to said input data signal represents an adaptive filter transfer function which is an inverse of said communications path transfer function.

A method for use in adaptively equalizing data signals received via a communications path, said method comprising the steps of:

• receiving, filtering and magnitude weighting an input data signal in accordance with a plurality of filter transfer functions and in accordance therewith generating a plurality of filtered and magnitude weighted data signals;
• combining said plurality of filtered and magnitude weighted data signals and in accordance therewith generating a first composite filtered and magnitude weighted data signal;
• receiving and multiplying said first composite filtered and magnitude weighted data signal and an adaptation control signal and in accordance therewith generating a second composite filtered and magnitude weighted data signal;
• and
• combining said input data signal and said second composite filtered and magnitude weighted data signal and in accordance therewith generating a third composite filtered and magnitude weighted data signal;
• wherein said input data signal is received via a communications path having a communications path transfer function associated therewith and, in accordance with said adaptation control signal, a frequency domain ratio of said third composite filtered and magnitude weighted data signal to said input data signal represents an adaptive filter transfer function which is an inverse of said communications path transfer function.

An apparatus including a multiple stage quantized feedback circuit for use in recovering data signals, said multiple stage quantized feedback circuit comprising:

• an ac coupling network configured to receive and ac couple an equalized data signal corresponding to a plurality of data and in accordance therewith provide a first ac coupled equalized data signal;
• a first voltage comparator coupled to said ac coupling network and configured to receive and slice said first ac coupled equalized data signal and in accordance therewith provide a dc coupled data estimate signal which includes a low frequency content;
• a cross-over combiner coupled to said first voltage comparator and configured to receive said dc coupled data estimate signal and said equalized data signal, extract said low frequency content from said de coupled data estimate signal, ac couple said equalized data signal and in accordance therewith provide a second ac coupled equalized data signal, and combine said low frequency content from said dc coupled data estimate signal with said second ac coupled equalized data signal and in accordance therewith provide a dc restored equalized data signal;
• and
• a second voltage comparator coupled to said cross-over combiner and configured to receive and slice said dc restored equalized data signal and in accordance therewith provide a recovered digital data signal representing said plurality of data.

A method for use in recovering data signals, said method comprising the steps of:

• receiving an equalized data signal corresponding to a plurality of data;
• ac coupling said equalized data signal and in accordance therewith generating a first ac coupled equalized data signal;
• slicing said first ac coupled equalized data signal and in accordance therewith generating a de coupled data estimate signal which includes a low frequency content;
• extracting said low frequency content from said dc coupled data estimate signal;
• ac coupling said equalized data signal and in accordance therewith generating a second ac coupled equalized data signal;
• combining said low frequency content from said dc coupled data estimate signal with said second ac coupled equalized data signal and in accordance therewith generating a dc restored equalized data signal;
• and
• slicing said dc restored equalized data signal and in accordance therewith generating a recovered digital data signal representing said plurality of data.

An apparatus including a servo control circuit for use in adaptively equalizing and recovering data signals, said servo control circuit comprising:

• a first filter configured to be coupled to an input of a comparator circuit and receive therefrom and filter an equalized data signal and in accordance therewith provide a first filtered signal, wherein said equalized data signal corresponds to a plurality of data and has been filtered and magnitude weighted by an adaptive filter in accordance with an adaptation control signal;
• a first rectifier coupled to said first filter and configured to receive and rectify said first filtered signal and in accordance therewith provide a first rectified signal;
• a second filter configured to be coupled to an output of said comparator circuit and receive therefrom and filter a quantized signal and in accordance therewith provide a second filtered signal, wherein said quantized signal corresponds to said equalized data signal following quantization thereof by said comparator circuit;
• a second rectifier coupled to said second filter and configured to receive and rectify said second filtered signal and in accordance therewith provide a second rectified signal;
• a signal combiner coupled to said first and second rectifiers and configured to receive and combine said first and second rectified signals and in accordance therewith provide a composite rectified signal;
• and
• an integrator coupled to said signal combiner and configured to integrate said composite rectified signal and in accordance therewith provide said adaptation control signal.

A method for use in adaptively equalizing and recovering data signals, said method comprising the steps of:

• coupling to an input of a comparator circuit and receiving therefrom and filtering an equalized data signal and in accordance therewith generating a first filtered signal, wherein said equalized data signal corresponds to a plurality of data and has been filtered and magnitude weighted by an adaptive filter in accordance with an adaptation control signal;
• rectifying said first filtered signal and in accordance therewith generating a first rectified signal;
• coupling to an output of said comparator circuit and receiving therefrom and filtering a quantized signal and in accordance therewith generating a second filtered signal, wherein said quantized signal corresponds to said equalized data signal following quantization thereof by said comparator circuit;
• rectifying said second filtered signal and in accordance therewith generating a second rectified signal;
• combining said first and second rectified signals and in accordance therewith generating a composite rectified signal;
• and
• integrating said composite rectified signal and in accordance therewith generating said adaptation control signal.