# US 10,482,918 B1 · Changing bit spacing for selected symbols written to a magnetic recording medium > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,482,918 B1 - Document ID: US10482918B1 - Status: Granted - Kind: B1 - Application number: 16/104,332 - Filed: 2018-08-17 - Granted: 2019-11-19 - Earliest claimed: 2018-08-17 - Assignees: Seagate Technology LLC - Applicants: Seagate Technology LLC - Inventors: Mehmet Fatih Erden; Stephanie Hernandez; Steven Douglas Granz - Web page: https://patentgrep.com/patent/US10482918B1 ## CPC - G11B 20/10009: {Improvement or modification of read or write signals} - G11B 20/105: {selecting parameter values from a plurality of predetermined settings} - G11B 20/1217: {on discs} - 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 A set of patterns written to a magnetic recording medium are found that result in a relatively high and/or low error when read back. Upon writing subsequent to the determining of the set of patterns, one pattern of the set of the patterns is identified within a data segment ready to be written to the magnetic recording medium. The data segment is written with a changed bit spacing in response to identifying that the one pattern of the set of the patterns is within the data segment. ## Claims ### Claim 1 A method, comprising: writing a plurality of different symbols to a magnetic recording medium at a nominal bit timing; determining a first set of the symbols that result in a relatively high error when read back; upon writing subsequent to the determining of the first set of symbols, identifying one symbol of the first, set of symbols within a data segment ready to be mitten to the magnetic recording medium; and writing the data segment with increased bit spacing relative to the nominal bit timing in response to identifying that the one symbol of the first set of symbols is within the data segment. ### Claim 2 (depends on 1) The method of claim 1, further comprising: determining a second set of the symbols written to the magnetic recording medium that result in a relatively low error when read back; upon writing subsequent to the determining of the second set of symbols, identifying one symbol of the second set of the symbols within a second data segment ready to be written to the magnetic recording medium; and decreasing a second bit spacing of the second data segment relative to the nominal bit timing in response to identifying the one symbol of the second set of the symbols within the data segment. ### Claim 3 (depends on 1) The method of claim 1, wherein determining the first set of symbols mitten to a magnetic recording medium that result in a relatively high error comprises writing pseudo-random bit sequences and reading back the pseudo-random bit sequences to determine the set of symbols. ### Claim 4 (depends on 3) The method of claim 3, wherein the first set of symbols have a lowest signal-to-noise ratio of all symbols in the pseudo-random bit sequences. ### Claim 5 (depends on 3) The method of claim 3, wherein the first set of symbols have a highest bit error rate of all symbols in the pseudo-random bit sequences. ### Claim 6 (depends on 1) The method of claim 1, wherein determining the first set of symbols written to a magnetic recording medium that result in a relatively high error comprises reading back previously written user data to determine the set of symbols. ### Claim 7 (depends on 1) The method of claim 1; wherein the bit spacing is increased by a fractional amount between 1% to 100% of a single bit spacing. ### Claim 8 A method, comprising: writing a plurality of different symbols to a magnetic recording medium at a nominal bit timing; determining a set of the symbols that result in a relatively low error when read back; upon writing subsequent to the determining of the set of symbols, identify one symbol of the set of the symbols within a data segment ready to be written to the magnetic recording medium; and write the data segment with decreased bit spacing relative to the nominal bit timing in response to identifying that the one symbol of the set of the symbol is within the data segment. ### Claim 9 (depends on 8) The method of claim 8, wherein determining the set of symbols written to a magnetic recording medium that result in a relatively low error comprises writing pseudo-random bit sequences and reading back the pseudo-random bit sequences to determine the set of symbols. ### Claim 10 (depends on 9) The method of claim 9, wherein the set of symbols have a highest signal-to-noise ratio of all symbols in the pseudo-random bit sequences. ### Claim 11 (depends on 9) The method of claim 9, wherein the set of symbols have a lowest bit error rate of all symbols in the pseudo-random bit sequences. ### Claim 12 (depends on 8) The method of claim 8, wherein determining the set of symbols written to a magnetic recording medium that result in a relatively low error comprises reading back previously written user data to determine the set of symbols. ### Claim 13 (depends on 8) The method of claim 8, wherein the bit spacing is decreased by a fractional amount between 1% to 50% of a single bit spacing. ### Claim 14 An apparatus, comprising: interface circuitry coupled to a head that reads from and writes to a magnetic recording medium; and a controller coupled to the interface circuitry and operable to: determine a set of symbols written to the magnetic recording medium that result in one of a relatively high error or relatively low error when read back; upon writing subsequent to the determining of the set of symbols, identify one symbol of the set of the symbols within a data segment ready to be written to the magnetic recording medium; and write the data segment with a changed bit spacing in response to identifying that the one symbol of the set of the symbols is within the data segment. ### Claim 15 (depends on 14) The apparatus of claim 14, wherein determining the set of symbols written to a magnetic recording medium that result in the relatively high or low error comprises writing pseudo-random bit sequences and reading back the pseudo-random bit sequences to determine the set of symbols. ### Claim 16 (depends on 15) The apparatus of claim 15, wherein the set of symbols have a lowest or highest signal-to-noise ratio of all symbols in the pseudo-random bit sequences. ### Claim 17 (depends on 15) The apparatus of claim 15, wherein the set of symbols have a highest or lowest bit error rate of all symbols in the pseudo-random bit sequences. ### Claim 18 (depends on 14) The apparatus of claim 14, wherein determining the set of symbols written to a magnetic recording medium that result in the relatively high or low error comprises reading back previously written user data to determine the set of symbols. ### Claim 19 (depends on 14) The apparatus of claim 14, wherein the set of symbols results in the relatively high error, the bit spacing being increased by a fractional amount between 1% to 100% of a single bit spacing. ### Claim 20 (depends on 14) The apparatus of claim 14, wherein the set of symbols results in the relatively low error, the bit spacings being decreased by a fractional amount between 1% to 50% of a single bit spacing.