US 5,490,091 AGranted

Histograms of processed noise samples for measuring error rate of a PRML data detection channel

AssigneeGuzik Technical Enterprises

InventorsAndrew Kogan, Alexander Taratorin, Alexander Tesler, Dmitry Varsanofiev

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Abstract

A method and apparatus for measuring the error rate of a magnetic recording device, such as a hard disk storing a set of data. The apparatus has a partial response maximum likelihood data detecting channel (PRML channel) which differs from a conventional PRML channel by including a noise processing unit (66) which is connected between the output of an A/D converter (54) and the input of a sequence detector (60), and a histogrammer (70), which is connected to the output of a noise processing unit. The method consists of estimating a sequence of noise samples received from the output of the A/D converter (54), processing the sequence of noise samples according to a plurality of predetermined sets of processing coefficients, accumulating a plurality of histograms of segregated processed noise samples, and processing the plurality of histograms so as to determine a dependence of a number of errors on a preselected criterion which characterizes a signal-to-noise ratio of the PRML channel. The above dependence can be extrapolated for an actual error rate of the channel being tested.

Claims25

Dependent claims

A method for measuring the error rate of a magnetic recording device storing a set of data and having a partial response maximum likelihood data detecting channel, said channel having an output, a predetermined set of values at which samples are taken, a plurality of known reference values, a plurality of predetermined sets of processing coefficients, and a plurality of control values for each reference value, said channel being set in accordance with a predetermined criterion, said method comprising the steps of:

reading at least a part of said set of data by means of said partial response maximum likelihood data detecting channel and obtaining a plurality of sampled signals from said set of data;
transforming each of said plurality of sampled signals in accordance with said plurality of known reference values into a plurality of sampled noise signals;
processing said plurality of sampled noise signals in accordance with said plurality of predetermined sets of processing coefficients, thus obtaining a plurality of processed sampled noise signals;
segregating said plurality of processed sampled noise signals in accordance with said plurality of control values, thus obtaining a segregated plurality of processed sampled noise signals;
accumulating said segregated plurality of processed sampled noise signals and sorting them into a plurality of histograms based on the frequency of occurrence of said segregated plurality of processed sampled noise signals, each histogram of said plurality of histograms having a specified measure of separation;
counting a number of histogram values corresponding to said specified measure of separation for each of said plurality of histograms and assuming the obtained number as a number of errors of said magnetic recording device corresponding to said specified measure of separation;
changing said specified measure of separation of each histogram a plurality of times and obtaining a plurality of measures of separation;
repeating said step of counting a plurality of times;
determining a dependence in accordance with said number of errors in all of said histograms for each of said specified measures of said plurality of measures of separation;
extrapolating said dependence to said predetermined criterion and determining a number of errors corresponding to said predetermined criterion;
and
evaluating the performance of said partial response maximum likelihood data detecting channel based upon said dependence and said extrapolating step.

9 more elements

An apparatus for measuring the error rate of a magnetic recording device which stores a set of data, said apparatus comprising:

a partial response maximum likelihood data detection channel having a predetermined set of values at which samples are taken and is set in accordance with a predetermined criterion;
a reference pattern generator, generating plurality of reference samples and plurality of control values;
a subtraction unit;
a noise processing unit, having means for processing plurality of noise samples in accordance with a plurality of predetermined processing coefficients, and transforming said plurality of noise samples into a plurality of processed noise samples, and
a histogrammer having means for accumulating said plurality of processed noise samples and segregating said plurality of processed noise samples into a plurality of histograms in accordance with a plurality of predetermined control values.

2 more elements

An apparatus for measuring the error rate of a magnetic recording device which stores a set of data, said apparatus comprising:

a partial response maximum likelihood data detection channel having a predetermined set of values at which samples are taken and is established in accordance with a predetermined criterion;
a reference pattern generator, generating plurality of reference samples and plurality of control values;
a subtraction unit;
a noise processing unit, having means for processing plurality of noise samples in accordance with a plurality of predetermined processing coefficients, and transforming said plurality of noise samples into a plurality of processed noise samples, and
a histogrammer having means for accumulating said plurality of processed noise samples and segregating said plurality of processed noise samples into a plurality of histograms in accordance with a plurality of predetermined control values.
said partial response maximum likelihood data detection channel comprising the following elements connected in series:
an amplifier which receives said set of data and produces a plurality of amplifier output signals;
a signal equalizing unit for equalizing said amplifier output signals, said signal equalizing unit producing a plurality of signal equalizing unit output signals;
signal sampling means for sampling said plurality of signal equalizing unit output signals;
and
a sequence detection unit for determining the sequence in which said samples have been taken;
a timing recovery unit for synchronizing said signal sampling means, said timing recovery unit being connected to said signal sampling means and to a point between said signal sampling means and said sequence detection unit;
and
a gain recovery unit for controlling the gain of said amplifier, said gain recovery unit being connected to said amplifier.

11 more elements

An apparatus for measuring the error rate of a magnetic recording device which stores a set of data, said apparatus comprising:

a partial response maximum likelihood data detection channel having a predetermined set of values at which samples are taken and is established in accordance with a predetermined criterion;
a reference pattern generator, generating plurality of reference samples and plurality of control values;
a subtraction unit;
a noise processing unit, having means for processing plurality of noise samples in accordance with a plurality of predetermined processing coefficients, and transforming said plurality of noise samples into a plurality of processed noise samples, said noise processing unit comprising at least:
a plurality of digital delay lines connected in series;
a plurality of multipliers connected to the output of each of said plurality of digital delay lines and
an adder, connected to the output of each of said plurality of multipliers
a histogrammer having means for accumulating said plurality of processed noise samples and segregating said plurality of processed noise samples into a plurality of histograms in accordance with a plurality of predetermined control values, said histogrammer means comprising at least:
an address formation unit;
a random access memory unit;
and
an incrementor, said address unit being connected in series to said random access memory unit and to said incrementor.

9 more elements

Dependencies are inferred from the claim text.