US 8,477,445 B2Granted

Write clock synchronization appartus for magnetic recording disk drives with patterned media

AssigneeGuzik Technical Enterprises

InventorsAnatoli B. Stein, Semen P. Volfbeyn

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Abstract

A write clock generator for use in writing data to a rotating patterned magnetic media disk is disclosed. The generator includes a magnetic read head for generating a succession of servo signals representative of succession of servo magnetization patterns detected from a corresponding succession of arcuate sectors along a circular data track on the disk. A preamble processor generates a corresponding succession of sector pair signals representative of the lengths of adjacent sectors along the data track on a rolling pair-wise basis. A next sector length predictor processor determines for a succession of pairs of sectors, a length ratio of the lengths of the sectors in the respective pairs of sectors. A clock generator generates a periodic clock for each sector of the succession of sectors, wherein the clock rate associated with a current sector has an associated phase deviation relative to a clock rate associated with a previous sector, which is proportional to the length ratio for the current sector and the previous sector.

Claims8

Dependent claims

A write clock synchronization apparatus for magnetic recording disk drives with patterned media comprising:

A. an analog to digital converter (ADC) for receiving an analog read back signal from a magnetic read head, and converting the analog read back signal into a digital read back signal;
B. a preamble processor having a read back signal input coupled to receive the digital read back signal, a digital clock input, an address mark output, a phase deviation output, and a sector length output, wherein said preamble processor is operative to:
i. detect preambles and address marks in the read back signal,
ii. generate address mark (AM) pulses indicative of the detection of an occurrence of address marks in the read back signal, and apply the AM pulses to the address mark output,
iii. derive a preamble clock from the respective preambles and for each preamble clock, determine a phase deviation between the preamble clock and a digital clock at the digital clock input, and apply the respective phase deviations on the phase deviation output;
and
iv. for each detected preamble, determine a length value representative of a time interval between detection of a current preamble and a detection of a preceding preamble, and apply the respective length values on the sector length output;
C. a next sector length predictor having a sector length input, an address mark input, an index input, and a predicted sector length output, wherein said sector length predictor is operative for a current detected preamble, to:
i. calculate a ratio of a length value for a previous sector to a length value for the current sector,
ii. determine an average ratio value for each sector during a revolution of the disk,
iii. determine a next sector predicted length value representative of a product of the current sector length by the corresponding average ratio on the output, and apply the next sector predicted length value on the predicted sector length output,
D. a phase increment calculator responsive to the address mark and the phase deviation from the preamble processor and next predicted sector length from the next sector length predictor, and operative to generate a phase increment value at a calculator output;
and
E. a clock generator responsive to the phase increment value from the phase increment calculator output, and operative to:
i. generate the digital clock and apply the digital clock to the digital clock input of the preamble processor, and
ii. generate an analog write clock signal at a write clock output,
wherein the phase and the frequency of the digital clock and the analog write clock signal are determined by the phase increment value.

14 more elements

An apparatus for generating a write clock signal for writing data to a magnetic recording disk bearing patterned media, wherein the disk includes on a surface transverse to and disposed about a central axis:

a plurality of concentric circular data tracks disposed about the central axis,
wherein each data track includes a plurality of arcuate sectors wherein each sector in a data track includes a plurality of islands of a relatively magnetizable material mutually separated in a circumferential direction along the data track by a region of relatively non-magnetizable material, wherein each island is adapted to be characterized by magnetization representative of a data bit written to the disk, and
wherein at least two of the sectors of the data tracks are characterized by a preamble followed by an address mark demarking a following data field, wherein the preamble includes a magnetic pattern detectable by a magnetic read head overlying the sectors during passage of the data track past the read head during rotation of the disk about the central axis, to indicate the lengths of the respective sectors,
comprising:
A. a preamble processor
operative as the disk rotates about the central axis with a magnetic read head overlying a data track, to:
receive a succession of digital preamble signals representative of a corresponding succession of preambles read from the disk by the read head, and
operative in response to the received digital preamble signal for each preamble and a digital clock determined from a previous digital preamble signal associated with a previous sector, to:
generate an address mark associated with a current digital preamble signal, wherein the address mark is representative of a first location following the preamble in the sector to which a bit of data is to be written to the current sector,
generate a sector length signal representative of a length associated with the current digital preamble signal associated with the current sector, and
generate a phase deviation value associated with the current digital preamble signal, wherein the phase deviation value is representative of a difference in phase associated with the current digital preamble signal associated with the current sector, with respect to the phase of the digital clock,
B. a next sector length predictor processor
operative for a current received digital preamble signal associated with a current sector, to:
store a current sector length (CSL) value representative of the length signal for the associated current sector,
access a stored CSL value for a previous sector,
determine a sector ratio value representative of the ratio of the stored current CSL value for the current sector, to the accessed CSL value for the previous sector,
update and maintain a rolling average of the sector ratio value over a plurality of revolutions of the disk, and
generate a predicted next sector length value corresponding the product of the sector length of the current sector and the current rolling average of the sector ratio value,
C. a phase adjustment determination network responsive to (i) the phase deviation value associated with the digital preamble signal for the current sector, (ii) an applied disk position encoder signal representative of the angular position of the disk, (iii) the address mark associated with the digital preamble signal for the current sector, and (iv) the predicted next sector length value, and operative to:
generate a phase increment value associated with the next sector, wherein the phase increment value is representative of a change in phase to be applied to the digital clock for application to the preamble processor for a digital preamble associated with the next sector for a then-current rotational rate of the disk,
D. a write clock generator responsive to the phase increment value to generate a data write clock signal for data to be written to a next sector.

18 more elements

Dependencies are inferred from the claim text.

Facts

Application: 13/706,311Filed 5 Dec 2012 · us provisional application
Priority: 6 Dec 2011
Published: US 2013/0141812 A16 Jun 2013
Granted: 2 Jul 2013
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

G11B 20/10222
Improvement or modification of read or write signals: clock-related aspects, e.g. phase or frequency adjustment or bit synchronisation
G11B 5/012
Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor: recording on, or…
G11B 5/59616
Circuits: synchronisation; Clocking
G11B 5/746
Patterned record carriers, wherein the magnetic recording layer is patterned into magnetic isolated data islands, e.g. discrete tracks: bit…