# US 4,635,141 A · Method and apparatus for storing data on magnetic or optical media

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- Number: US 4,635,141 A
- Document ID: US4635141A
- Status: Granted
- Kind: A
- Application number: 06/433,880
- Filed: 1982-10-13
- Granted: 1987-01-06
- Earliest claimed: 1982-10-13
- Assignees: United States Design Corporation
- Inventors: Douglas Coulter
- Web page: https://patentgrep.com/patent/US4635141A

## CPC

- G11B 20/10212: {compensation for data shift, e.g. pulse-crowding effects}
- G11B 7/013: for discrete information, i.e. where each information unit is stored in a distinct discrete location {, e.g. digital information formats within a data block or sector}
- G11B 20/1411: {conversion to or from pulse width coding}
- G11B 20/182: {using test patterns}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

Method and apparatus for storing data on a recording medium wherein the method includes grouping digital binary signals into chunks of N bits where N is an integer greater than 1. The value of each of the N bit chunks is determined and converted into a symbol cell. Each symbol cell has a duration which is dependent upon the value of the corresponding N bit chunk. The symbol cell is recorded. The transition shift for each of a plurality of juxtapositions of symbol cells is determined, and the symbol cell duration is varied depending upon the compensation required from the determined transition shift. A system of reading out the recorded symbol cells is also disclosed.

## Claims

### Claim 1

A method of storing data on a recording medium comprising the steps of:
grouping digital binary signals into chucks of N bits wherein N is an integer number greater than 1;
determining the value of each of N bit chunks;
converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunk and which is equal to the sum of the minimum transition period for the recording medium and an incremental time period, said incremental time period being directly proportional to the value of said N bit chunk, the maximum duration of said incremental time period being less than the time duration of the minimum transition period; and
recording said symbol cells onto a recording medium.

### Claim 2 (depends on 1)

The method of claim 1 wherein N is equal to 3.

### Claim 3

A method of storing data on a recording medium comprising the steps of:
grouping binary input signals into chunks of N bits wherein N is an integer number greater than 1;
determining the values of each of said N bit chunks;
determining the relative frequency of occurrence of each of the values of said N bit chunks;
assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell;
generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto; and
recording said symbol cells onto a recording medium.

### Claim 4 (depends on 3)

The method of claim 3 wherein said symbol cells each have a duration equal to the sum of the minimum transition period for the recording medium and an incremental time period, said incremental time period being inversely proportional to the frequency of occurrence of the values of said N bit chunks, the maximum duration of said incremental time period being less than the time duration of the minimum transition period.

### Claim 5 (depends on 4)

The method of claim 4 wherein N is equal to 3.

### Claim 6

A method of storing data on a recording medium comprising the steps of:
grouping binary signals into chunks of N bits wherein N is an integer greater than 1;
determining the value of each of said N bit chunks;
converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunk;
recording on a portion of said medium the relative symbol cell juxtapositions for at least two successive symbol cells;
determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; and
adaptively precompensating for said transition shift by varying the duration of said symbol cells before recording.

### Claim 7

A method of storing data on a recording medium comprising the steps of:
grouping binary signals into chunks of N bits wherein N is an integer greater than 1;
determining the values of each of said N bit chunks;
determining the relative frequency of occurrence of each of the values of said N bit chunks;
assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell;
generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto;
recording on a portion of said medium the relative symbol juxtaposition for at least two successive symbol cells;
determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; and
adaptively precompensating for said transition shift by varying the duration of said symbol cells before recording.

### Claim 8 (depends on 6, 7)

The method of storing data on a recording medium of either claim 6 or 7 wherein said symbol cell has a duration equal to the sum of the minimum transition period for the recording medium and an incremental time period, said incremental time period being inversely proportional to the frequency of occurrence of the values of said N bit chunks, the maximum duration of said incremental time period being less than the time duration of the minimum transition period.

### Claim 9

A method of storing data in a recording medium comprising the steps of:
grouping binary signals into chunks of N bits wherein N is an integer greater than 1;
determining the value of each of said N bit chunks;
converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunk;
recording on a portion of said medium the relative symbol cell juxtapositions for a plurality of successive symbol cells;
determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells;
modifying the duration of said symbol cells to compensate for said determined transition shift; and
recording said symbol cells onto a recording medium.

### Claim 10 (depends on 9)

The method of claim 9 further comprising the steps of determining the relative frequency of occurrence of each of the values of said N bit chunks;
assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is a timed duration assigned to the symbol cell; and
generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto.

### Claim 11

A method of storing data on a recording medium comprising the steps of:
grouping digital binary signals into chunks of N bits, wherein N is an integer number greater than 1;
determining the value of each of said N bit chunks;
converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunk;
recording a plurality of different symbol juxtapositions onto a magnetic medium;
determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells;
compensating said symbol cells for transition shift by varying the duration thereof; and
recording said compensated symbol cells corresponding to said N bit chunks onto a recording medium.

### Claim 12 (depends on 11)

The method of claim 11 wherein each precompensated symbol cell has a duration equal to the sum of the minimum transition period for the recording medium and an incremental time period, said incremental time period being directly proportional to the value of said N bit chunks, the maximum duration of said incremental time period being less than the time duration of the minimum transition period.

### Claim 13 (depends on 11, 12)

The method of claim 11 or 12 further comprising the step of determing the relative frequency of occurrence of each of the values of said N bits chunks;
assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell; and
generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto.

### Claim 14 (depends on 11)

The method of claim 11 wherein said compensating step further comprises the step of successively rerecording said plurality of bit juxtapositions and determining said transition shift therein until said transition shift is reduced to an acceptable level; and recording symbol cells of data onto said recording medium by precompensating said bits in accordance with the determined transition shift of said plurality of bit shift juxtapositions.

### Claim 15

A method of storing data on a recording medium comprising the steps of:
grouping binary signals into chunks of N bits wherein N is an integer greater than 1;
determining the value of each of said N bit chunks;
converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunks;
recording on a portion of said medium the relative symbol cell juxtapositions for three successive symbol cells;
determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells;
compensating said symbol cells for transition shift by varying the duration of said symbol cells;
repeating said recording, determining and compensating steps until said transition shift has been compenstated; and
compensating symbol cells to be stored for transition shift by varying the duration of said symbol cells in accordance with the determined transition shift of juxtaposed symbol cells.

### Claim 16

A method of compensating for transition shift in a magnetic storage medium comprising the steps of:
recording on a portion of said magnetic medium a plurality of different bit juxtapositions;
recording the order in which said plurality of relative bit juxtaposition are recorded;
reading from said medium the order in which said bit juxtapositions are recorded;
reading from said medium the plurality of different bit juxtapositions;
determining the level of transition shift for each of said plurality of different bit juxtapositions;
reading data stored on said medium; and
compensating said read data bits for transition shift by varying the duration of said symbol cells in accordance with said determined transition shift.

### Claim 17

A method of storing data on a recording medium comprising the steps of:
grouping digital binary signals into chunks of N bits, wherein N is an integer number greater than 1;
determining the value of each of said N bit chunks;
converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunk; and
recording on a portion of said magnetic medium a plurality of relative symbol cell juxtapositions;
recording the order in which said plurality of relative symbol cell juxtapositions are recorded;
reading from said medium the order in which said symbol cell juxtapositions are recorded;
reading from said medium the plurality of symbol cell juxtapositions;
determining the level of transition shift for each of said plurality of symbol cell juxtapositions;
reading data stored in a form of said symbol cells from said medium; and
compensating said read data symbol cells for transition shift by varying the duration of said symbol cells in accordance with said determined said transition shift.

### Claim 18 (depends on 17)

The method of claim 17 wherein said symbol cell has a duration equal to the sum of the minimum transition period for the recording medium and an incremental time period, said incremental time period being directly proportional to the value of said N bit chunk, the maximum duration of said incremental time period being less than the time duration of the minimum transition period.

### Claim 19 (depends on 17, 18)

The method of claim 17 or 18 further comprising the steps of determining the relative frequency of occurrence of each of the values of said N bit chunks;
assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell; and
generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto.

### Claim 20

A method of storing data on a recording medium comprising the steps of:
recording a plurality of different bit juxtapositions onto a magnetic medium;
determining from said recorded bit juxtapositions the transition shift for each of said juxtapositions of bits;
compensating said bits for transition shift by varying the duration thereof;
recording bits of data on said recording medium by precompensating said bits in accordance with the determined transition shift of said plurality of bits shift juxtapositions;
recording the order in which said plurality of different bit juxtapositions are recorded onto said magnetic medium;
reading from said medium the order in which said bit juxtapositions are recorded;
reading from said medium the plurality of recorded bits of data;
determining the level of transition shift for each of said plurality of different bit juxtapositions;
reading said recorded bits of data from said medium; and
compensating said read data bits for transition shift by varying the duration of said bits in accordance with said determined transition shift.

### Claim 21

A method of storing data on a recording medium comprising the steps of:
grouping ditigal binary signals into chunks of N bits, where N is an integer greater than 1;
determining the value of each of said N bit chunks;
converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an duration which is dependent upon the value of the corresponding N bit chunks;
recording on a portion of said medium the relative symbol cell juxtapositions for at least two successive symbol cells;
determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells;
compensating said symbol cells for transition shift by varying the duration of said symbol cells;
recording on a portion of said magnetic medium a plurality of relative symbol cell juxtapositions wherein said symbol cells are precompensated to reduce transition shift distortion;
recording the order in which said plurality of relative symbol cell juxtapositions are recorded;
reading from said medium the order in which said symbol cell juxtapositions are recorded;
reading from said medium the plurality of symbol cell juxtapositions;
determining the level of transition shift for each of said pluality of said symbol cell juxtapositions;
reading data stored in the form of said symbol cells from said medium; and
compensating said read data symbol cells for transition shift by varying the duration of said symbol cells in accordance with said determined transition shift.

### Claim 22 (depends on 21)

The method of claim 21 further comprising the steps of determining the relative frequency of occurence of each of the values of said N bit chunks;
assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell;
generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto; and wherein said compensated read data symbol cells are converted back to N bit chunks corresponding to said grouped digital binary signals.

### Claim 23

A system of storing data on a recording medium comprising:
means for grouping digital binary signals into chunks of N bits wherein N is an integer number greater than 1;
means for determining the value of each of said N bit chunks;
means for converting sain N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunk, and having a duration equal to the sum of the minimum transition period for the recording medium and an incremental time period, said incremental time period being directly proportional to the value of said N bit chunks, the maximum duration of said incremental time period being less than the time duration of the minimum transition period; and
means for recording said symbol cells onto a recording medium.

### Claim 24 (depends on 23)

The system of claim 23 wherein N is equal to 3.

### Claim 25

A system of storing data on a recording medium comprising:
means for grouping binary input signals into chunks of N bits wherein N is an integer number greater than 1;
means for determining the value of each of said N bit chunks;
means for determining the relative frequency of occurrence of each of the values of said N bit chunks;
means for assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell;
means for generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto; and
means for recording said symbol cells onto a recording medium.

### Claim 26 (depends on 25)

The system of claim 25 wherein said symbol cells have a duration equal to the sum of the minimum transition period for the recording medium and an incremental time period, said incremental time period being directly proportional to the value of said N bit chunk, the maximum duration of said incremental time duration being less than the time duration of the minimum transition period.

### Claim 27

A system for storing data on a recording medium comprising:
means for grouping binary signals into chunks of N bits wherein N is an integer greater than 1;
means for determining the value of each of said N bit chunks;
means for converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunks;
means for recording on a portion of said medium the relative symbol cell juxtapositions for three successive symbol cells;
means for determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells;
means for compensating said symbol cells to be stored for transition shift by varying the duration of said symbol cells in accordance with the determined transition shift of juxtaposed symbol cells.

### Claim 28 (depends on 27)

The system of claim 27 wherein N equals 3.

### Claim 29

A system for storing data on a recording medium comprising:
means for grouping binary signals into chunks of N bits wherein N is an integer greater than 1;
means for determining the value of each of said N bit chunks;
means for converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunk;
means for recording on a portion of said medium the relative symbol cell juxtapositions for at least two successive symbol cells;
means for determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; and
means for adaptively precompensating for said transition shift by varying the duration of said symbol cells before recording and means for recording said symbol cells corresponding to said input data.

### Claim 30 (depends on 29)

A system of storing data on a recording medium of claim 29 further comprising:
means for determining the relative frequency of occurrence of each of the values of said N bit chunks;
means for assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell; and
means for generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto.

### Claim 31

A system for storing data on a recording medium comprising:
means for grouping digital binary signals into chunks of N bits wherein N is an integer number greater than 1;
means for determining the value of each of said N bit chunks;
means for converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having duration which is dependent upon the value of the corresponding N bit chunk;
means for recording on a portion of said magnetic medium a plurality of relative symbol cell juxtapositions;
means for recording the order in which said plurality of relative symbol cell juxtapositions are recorded;
means for reading from said medium the order in which said symbol cell juxtapositions are recorded;
means for reading from said medium the plurality of symbol cell juxtapositions;
means for determining the level of transition shift for each of said plurality of symbol cell juxtapositions;
means for reading data stored in a form of said symbol cells from said medium; and
means for compensating said read data symbol cells for transition shift by varying the durtion of said symbol cells in accordance with said determined transition shift.

### Claim 32 (depends on 31)

The system of claim 31 further comprising:
means for assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is a time duration assigned to the symbol cell; and
means for generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto.

### Claim 33

A system of storing data on a recording medium comprising:
means for grouping digital binary signals into chunks of N bits, where N is an integer greater than 1;
means for determining the value of each of said N bit chunks;
means for converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunks;
means for recording on a portion of said medium the relative symbol cell juxtapositions for at least two successive symbol cells;
means for determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells;
means for compensating said symbol cells for transition shift by varying the duration of said symbol cells;
means for recording on a portion of said magnetic media a plurality of relative symbol cell juxtapositions wherein said symbol cells are precompensated to reduce transition shift distortion;
means for recording the order in which said plurality of relative symbol cell juxtapositions are recorded;
means for reading from said medium the order in which said symbol cell juxtapositions are recorded and the plurality of symbol cell juxtapositions;
means for determining the level of transition shift for each of said plurality of said symbol cell juxtapositions;
means for reading data stored in the form of said symbol cells from said medium; and
means for compensating said read data symbol cells for transition shift by varying the duration of said symbol cells in accordance with said determined transition shift.

### Claim 34

A system for compensating for transition shift in a magnetic storage medium comprising the steps of:
means for recording on a portion of said magnetic medium a plurality of relative symbol cell juxtapositions wherein said symbol cells are precompensated to reduce transition shift distortion;
means for recording the order in which said plurality of relative symbol cell juxtapositions are recorded;
means for reading from said medium the order in which said symbol cell juxtapositions are recorded;
means for reading from said medium the plurality of symbol cell juxtapositions;
means for determining the level of transition shift for each of said plurality of symbol cell juxtapositions;
means for reading data stored in the form of said symbol cells from said medium; and
means for compensating said read data symbol cells for transition shift by varying the duration of said symbol cells in accordance with said determined transition shift.