Abstract: Embodiments of the invention relate to writing servo patterns having aligned phases onto a recording disk in a process to write the servo patterns onto the disk. In one embodiment, time aligned patterns are written onto a magnetic disk on the basis of time intervals between base patterns with timings aligned to each other throughout tracks on the disk. The time aligned patterns are written onto typically servo tracks at time intervals Ts with aligned timings. Then, on the basis of these time aligned patterns, product servo patterns are written onto the disk. A time aligned pattern is written onto the disk after the lapse of a predetermined write time period since detection of a base pattern corresponding to the time aligned pattern. The write time period is determined on the basis of time intervals between base patterns on adjacent tracks.

Abstract: An apparatus and associated method are described for use in a disk drive including a disk that that is supported for controlled rotation and for cooperating with a transducer arrangement for accessing the disk in performing a data operation. The disk includes an arrangement of servo track wedge segments for storing servo data such that a set of servo data is periodically available as the disk is rotated in relation to the transducer arrangement and the servo track wedges are separated by an arrangement of user data wedge segments for use in storing user data. Generally, a controller IC and a channel IC are provided. The servo data is transferred from the channel IC to the controller IC using one data protocol and user data is bidirectionally transferred between the channel IC and the controller IC using a different data protocol.

Abstract: A servo controller for an embedded disk controller comprises a read channel interface that includes a programmable control logic that receives a servo field detected signal from a module that detects a servo field start bit. A memory in the read channel interface is enabled by the programmable control logic for receiving servo field data from a read channel device, wherein the programmable control logic is configured to operate in a first mode and a second mode allowing the servo controller to process servo data from the read channel device. The servo controller processes the servo data using first and second data widths during the first and second modes, respectively.

Abstract: A method of writing product servo sectors on a disk of a disk drive is disclosed. The disk comprises a reference pattern having a plurality of sync marks written around the disk. The sync marks are detected to generate a sync mark detect signal, and a timing recovery measurement is generated in response to the sync mark detect signal. A frequency control signal is generated in response to the timing recovery measurement, and a servo write clock is generated in response to the frequency control signal. A feed-forward compensation value is generated in response to the timing recovery measurement and the frequency control signal, and the timing recovery measurement is adjusted in response to the feed-forward compensation value to compensate for a repeatable phase error in the timing recovery measurement. The servo write clock and the head internal to the disk drive are used to write the product servo sectors to the disk.

Abstract: A method of simultaneously recording multiple reference magnetic signals by using a magnetic head having multiple recording portions is provided. A writing yoke formed of a ferromagnetic material thin film and a back yoke are provided to a side wall of a slider, which is formed of a hard ceramic, as a distal end portion of the magnetic head. After forming the yokes to the slider, grooves are formed by focused ion beam machining from the slider side. All of the materials of the slider, the back yoke, and the writing yoke are thus locally removed. Magnetic writing is thus blocked by the grooves, and magnetic recording is only performed by four recording portions of the writing yoke.

Abstract: A method of servo writing a disk for use in a disk drive is disclosed by writing discontinuous spiral tracks on the disk to protect against overheating the head and/or preamp circuitry. A write clock is synchronized to the rotation of the disk, and a plurality of discontinuous spiral tracks are written on the disk. Each discontinuous spiral track is written at a predetermined circular location determined from the write clock, and each discontinuous spiral track comprises a plurality of segments separated by gaps. Each segment comprises a high frequency signal interrupted at a predetermined interval by a sync mark.

Abstract: A magnetic recording disk drive has a patterned magnetic recording disk with data blocks of magnetizable material separated by nonmagnetic regions, a read head for reading the magnetized data blocks and generating a readback signal, and a timing circuitry that generates from the readback signal a series of timing pulses. When the read head is over a nonmagnetic region the readback signal is significantly reduced, and this signal reduction is detectable to determine the position of the nonmagnetic regions. The timing circuitry includes a rectifier that rectifies the readback signal, a highpass filter that filters the rectified signal at the frequency of the data blocks, and a peak detector that detects the peaks of the filtered signal and generates a series of timing pulses, each pulse representing a nonmagnetic region.

Abstract: The difference is detected between the outputs from first and second heads in a recording medium drive. The first head is positioned relative to the boundary between a first recording track and a separation track isolating the first recording track and a second recording track from each other. The second head is positioned relative to the boundary between the separation track and the second recording track. A position information specifying the positions of the first and second heads are generated based on the difference. The first and second heads follow the different boundaries, so that the outputs of the first and second heads reliably vary. The difference between the outputs thus reliably changes. An accurate position information can be generated based on the difference. The position information may be utilized in tracking servo control, for example. This enables establishment of the tracking servo control with a higher accuracy.

Abstract: A technique to sample a signal from a disk by using frequency and phase offset adjustment in a phase locked loop (PLL) timing recovery loop to sample read data from the disk, prior to a disk clocked clocking acquires a lock. Subsequently, sampling a signal from a disk by using only phase offset adjustment in the PLL timing recovery loop to sample read data from the disk after the disk clocked clocking acquires the lock. The sampled data is then error corrected by applying an error correction code (ECC).

Abstract: Timing recovery optimization using disk clock. A novel means is presented to perform and provide control of the sampling frequency of a signal that is read from a disk within a hard disk drive (HDD). Two separate, yet somewhat cooperating control loops are employed to provide feedback control of the sampling frequency of the signal that is read from disk. A timing recovery loop and a disk clock loop operate in conjunction with one another according to some desired manner (which can be predetermined or adaptive) to ensure that the sampling of the signal is performed to a very accurate degree. In one implementation, the timing recovery loop governs the sampling rate until the disk clock loop has locked, from which time either the disk clock loop govern the sampling or some combination of the signals provided from the two loops govern the sampling.

Abstract: Optimal synchronization mark/address mark construction. These marks can generally be referred to as sync marks. A novel means is presented by which sync marks can be generated for use within a variety of communication systems including HDD systems. The sync marks generated hereby have a largest possible minimum distance measurement that ensures highly accurate detection of the transition between the data portion and the preamble portion of information that is processed. Various types of distance measurement criteria can be employed, including a Euclidean distance measurement or a Hamming distance measurement, when selecting the sync mark from among a plurality of possible sync marks.

Abstract: An operation clock controller for preventing a semiconductor memory device from operating when an operation frequency of an external clock is higher than a predetermined frequency. The operation clock controller includes a clock buffer for buffering an external clock to output an internal clock; a unit delaying set for sequentially delaying the internal clock to output a plurality of delayed clocks; a phase detecting block for detecting logic levels of the delayed clocks at a rising edge of the internal clock to output phase detecting signals; a sampling pulse generator for outputting a sampling signal generated at a predetermined point of the internal clock; a latching block for outputting a phase detection latch signal by sampling and latching the phase detection signal at a point of the sampling signal being inputted; and a frequency detection block for outputting the frequency detection signal by logically combining the phase detection latch signal.

Abstract: A phase locked loop (PLL) circuit, comprises a frequency integrator circuit that receives a target signal, a phase shift signal and a frequency gain correction parameter and that selectively disables tracking frequency offset based on a value of the frequency gain correction parameter. A phase integrator circuit communicates with frequency integrator circuit, that synchronizes phase with the target signal and generates a phase signal. A phase shift measurement circuit generates the phase shift signal based on the phase signal. A phase interpolator circuit generates the frequency gain correction parameter based on the phase signal.

Abstract: Methods according to some embodiments include writing servo patterns on a data storage medium including a plurality of timing patterns in response to phase correction values generated using a phase correction value (PCV) kernel having a length that is less than the number of timing patterns on the data storage medium.

Abstract: Servo demodulation is performed by appropriately compensating for demodulation errors caused by fluctuation of the replayed signal amplitude of a phase servo pattern. A servo demodulating circuit comprises single waveform sampling means for reading into a register a single waveform of a servo burst signal included in a phase servo signal based on a sampling clock synchronized by clock synchronization means, single waveform digitizing means for calculating an amplitude value of the single waveform of the servo burst signal from peak and bottom of the single waveform of the servo burst signal read into the register, and for standardizing a value of the register based on an amplitude value of the single waveform of the servo burst signal, and phase information calculation means for calculating phase information of the single waveform of the servo burst signal based on the value of the register standardized by the waveform digitizing means.

Abstract: Embodiments in accordance with the present invention help a disk drive to effectively cope with a data address mark detection error. In one embodiment, a data sector is provided with plural data address marks and an read/write (RW) channel reads out the data sector using part of those data address marks. Each divisional section of a split sector has two data address marks and the RW channel uses one of the two data address marks. A data address mark to be used is specified by a register. When an error occurs in detecting a data address mark, its position is stored in a register. Based on the error position, an error recovery processing section stores, in the register, a data address mark to be used in a next retry.

Abstract: A method of writing product servo sectors to a disk of a disk drive is disclosed. The disk comprises a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval. The head internal to the disk drive is used to read the spiral tracks to generate a read signal. The read signal is integrated to generate a ramp signal, wherein a position error signal is generated from the ramp signal. The position error signal is used to maintain the head internal to the disk drive along a servo track while writing product servo sectors along the servo track.

Abstract: Embodiments in accordance with the present invention suppress an adverse influence on a pattern of a magnetic disk due to its rotational jitter and write the pattern at more accurate timing. In accordance with one embodiment, a hard disk controller/microprocessing unit (HDC/MPU) controls a clock frequency of a data clock generation circuit so that a rotational jitter of the magnetic disk be compensated when writing and reading user data. The HDC/MPU expects a detection timing of next adjacent servo sector using an error between an actual detection timing and an expected detection timing of a servo sector which has already been detected. The HDC/MPU controls the clock frequency using the expected timing and writes and reads user data between current servo sector and next adjacent servo sector according to the clock signal.

Abstract: A servo track sensing system receives equalized servo data from a servo demodulator and corrects for radial incoherence in the servo data. The system has a radial incoherence estimator that receives the equalized servo data and provides a radial incoherence estimate. A sequence detector receives the equalized servo data and the radial incoherence estimate, and provides a sequence detector output. A correlator receives the sequence detector output and provides correlator output data. The correlator output data has a reduced level of errors due to radial incoherence.

Abstract: Methods and systems for minimizing distortions in an analog data signal include equalizing the analog data signal at a receive end. In an embodiment, the invention adapts equalization parameters to a signal path associated with the analog data signal. Adaptive control logic is implemented with analog and/or digital components. In an embodiment, the invention equalizes a discreet-time analog representation of an analog data signal. In an embodiment, the invention digitally controls equalization parameters. In an embodiment, a resultant equalized analog data signal is digitized. In an example implementation, an analog data signal is sampled, a quality of the samples is measured, and one or more equalization parameters are adjusted with digital controls as needed to minimize distortion of the samples. The equalized samples are then digitized. The present invention is suitable for lower rate analog data signals and multi-gigabit data rate analog signals.

Abstract: A method for storing user data on a hard disk drive system comprises distributing user data across a plurality of independent data sectors, with each data sector including a first header having a first preamble field and a first sync mark field, and a second header having a second preamble field and a second sync mark field. The method performs a first timing recovery phase for recovering signal amplitude by acquiring phase and frequency lock from at least one of the preamble fields, and performs a subsequent frame synchronous detection phase by acquiring a corresponding sync mark field.

Abstract: A read channel equalizer of a magnetic tape drive which equalizes digitally sampled magnetic signals detected by a read head is dynamically adapted. A detector of equalizer dynamic adaptation logic compares equalizer output signals to desired values that are based on the decoding scheme (such as +2, 0 and ?2 for PR4) to sense equalizer output signals that are offset from at least one desired value, and signals the fact of each offset and its polarity as amplitude independent error signals. The signaled sensed amplitude independent error signals are fed back to adjustable taps of the equalizer. The simplified error signals thus avoid complex calculations of waveform errors, such as least mean square calculations. The error signals may be weighted and may be adjusted to align synchronously provided error signals with asynchronous taps of the equalizer.

Abstract: A method and apparatus for providing high speed, linear-phase interpolation. Signals from a plurality of differential pairs are weighted to produce an output clock having a selectable linear phase variation. A controller includes a pulse generator for providing a predetermined number of pulses having a predetermined phase shift and a predetermined frequency and an interpolator for processing the predetermined number of pulses having a predetermined phase shift and a predetermined frequency to generate a clock signal that is linearly adjustable between a predetermined number of output phases.

Abstract: Self-servo-writing of multi-slot timing patterns is described. Individual timing marks are replaced with groups of timing mark slots. At each timing mark location, a time measurement is made by detecting a timing mark in one of the slots. Also, extensions to the existing timing marks are written in other slots. The combination of timing measurements at every timing mark and extensions to those timing marks written at every opportunity improves the overall precision of the timing propagation. The improved accuracy of timing mark placement produces a commensurate improvement in the placement of the concomitantly written servo-data. In addition, the alignment accuracy of the written pattern is less sensitive to variations in rotation speed and variations in the shape of written transitions. Moreover, only a single disk revolution is required at each servo radius to write servo data and propagate the timing marks to maintain timing alignment.

Abstract: Write control bits are associated with servo pattern data bits to selectively disable or enable a write gate in a HDD write channel for self-servo writing after being sealed but before being vended to a user. The write gate can be disabled and enabled without deenergizing the write channel. A single write delay is calculated from one timing mark to the next to enable writing the next timing mark and portions of the radial pattern and servo pattern between the timing marks.

Abstract: A data discriminating unit includes a data discriminator and a sync signal discriminator. A data sync signal is detected for the bit string discriminated from the output of the sync signal discriminator, and the data is demodulated for the bit string discriminated from the output of the data discriminator, thereby optimizing the signal to a form suitable for discrimination and detection of the data sync signal and demodulation for data reproduction. As a result, the detection performance of the data sync signal can be improved while maintaining the data discrimination performance. A Viterbi decoder is used for discrimination by the data discriminator and the sync signal discriminator for the optimization thereby to optimize the number of states, the number of paths for state transition and the path memory length. A signal having no continuous inversions of the recording data is used as the data sync signal.

Abstract: The invention includes a testing method which may be applied to at least one writer in a disk drive during the self-test phase to generate write parameters, focused on the Over Shoot Control (OSC) of the write current parameter to improve the reliability of write operations by that writer. The Minimum OSC is used for write operations in normal temperatures. The Optimum OSC is used for a first lower temperature range, preferably between essentially 15 degrees Centigrade and essentially 5 degrees Centigrade. The Maximum OSC is preferred below essentially 5 degrees Centigrade. The Minimum OSC should preferably guarantee both an Adjacent Track Write (ATW) criteria, as well as guarantee a Write Induced Instability (WII) criteria. The invention includes the write parameter collection, as well as the disk drive containing the generated write parameter collection.

Abstract: A disc drive with a disc having multiple concentric data tracks. A track start point is rotationally displaced by a track skew time relative to a track start point of an adjacent concentric data tracks. The read/write head has a write settling time that is more than the track skew time. A data reordering circuit and firmware reorders write data and provides the reordered data to the read/write head after the write settling time. The reordering of the write data reduces write latency.

Abstract: A method for writing servo information onto a disk of a hard disk drive with a servo writer. The disk has a circumferential index and a band of servo reference tracks. The circumferential index is detected from a clock signal generated from a clock track of the disk. The reference tracks include radial indices. A spiral servo pattern is written upon the detection of the circumferential index and a radial index. The servo writer includes a phase detector that detects changes in the relative position of the circumferential and radial indices and a delay circuit that delays the clock signal to offset such changes.

Abstract: A disk drive is disclosed that estimates a sinusoidal error in a wedge time period due to eccentricity in the disk rotating to generate eccentricity compensation values. During a write operation a head is positioned over a target data sector within a target track, a write clock frequency is set using an eccentricity compensation value corresponding to the target data sector, and data is written to the target data sector using the write clock frequency. In this manner, the eccentricity compensation value adjusts the write clock frequency to better optimize the linear bit density from the inner to outer diameter tracks.

Abstract: A pattern dependent write equalization method is disclosed. The method includes identifying a trait of a data pattern in a stream of write data. A characteristic of a write equalization signal is then defined according to the identified trait for the data pattern.

Abstract: A circuit locks onto a frequency of data encoded on a medium, taking frequency variations in the physical travel of the medium into account. The circuit includes a disk locked clock (DLC) circuit having a synthesizer operating under digital control based on a feedback signal to produce a servo reference clock and a read reference clock that track frequency variations in the physical travel of the medium. A recovered clock signal is produced based on the servo reference clock and the read reference clock. A digital phase locked loop maintains a frequency lock of the recovered clock signal. An error measurement circuit is connected to the digital phase locked loop. The error measurement circuit produces the feedback signal for digitally controlling the digital logic circuit synthesizer to produce the servo reference clock and the read reference clock that track frequency variations in the physical travel of the medium.

Abstract: A method of writing product servo sectors to a disk of a disk drive is disclosed. The disk comprises a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval. The sync marks in the spiral tracks are detected to synchronize a servo write clock used to open a demodulation window during which the high frequency signal in the spiral tracks is demodulated to generate a position error signal for maintaining the head along a first servo track while writing product servo sectors along the first servo track. The demodulation window is then shifted by an integer number of sync mark intervals to initiate a seek to a second servo track. The head is then used to write product servo sectors along the second servo track.

Abstract: A disk writing apparatus includes: a temperature sensor sensing an ambient temperature of a disk; a sync mark generator generating a sync mark having a pattern when a writing temperature indicating an ambient temperature at which data is written on the disk is sensed, wherein the pattern of the sync mark corresponds to the sensed writing temperature; a writing controller outputting the writing temperature sensed by the temperature sensor to the sync mark generator; a multiplexer adding the sync mark generated by the sync mark generator to the data; and a writing unit writing the data to which the sync mark is added on the disk. Accordingly, error rates when data is written and when data is reproduced can be improved by optimally compensating for the disk writing temperature and the disk reproducing temperature using parameters of devices of an hard disk drive.

Abstract: An apparatus includes an address mark detector having an address mark output. The address mark output is indicated as erroneous if errors in a detected address mark exceed an error threshold function. The error function has a variation as a function of a difference between a detected address mark time and a reference address mark time.

Abstract: A read circuit for providing multi-bit disk data to a disk controller in correspondence to analog data from a disk head, includes a low frequency clock generator whose phase is adjustable in response to a detection of the synchronization marker in the analog disk data. A high frequency clock is phase-locked to the output of the disk head, and synchronizes operation of an A/D converter and a bit detector which produces a verified single-bit based on the A/D output. A serial-to-parallel converter converts the single bit output from the bit detector to a parallel output, and the parallel output is latched to multi-bit disk data for use by the disk controller in accordance with a low frequency clock. The low frequency clock is generated by a clock generator from the high frequency clock with a phase that is adjustable in response to the synchronization mark detector.

Abstract: A plurality of recording media combined integrally having a plurality of recording surfaces; and a plurality sets of reading heads and writing heads, combined integrally, provided for the respective ones of the plurality of recording surfaces, are provided. Upon writing data on each recording medium with the writing head provided therefor, a writing position is controlled as a result of positioning information previously provided on the recording media including the recording medium other than the each recording medium being read with the reading heads provided therefor.

Abstract: Analysis of a read back signal in a magnetic recording device is disclosed. The read back signal is converted to a digital read back signal, and a low frequency component of the digital read back signal is restored. A sample clock is recovered from the restored digital read back signal, and the restored digital read back signal is averaged using the recovered sample clock. A timing error is calculated based at least in part on the averaged restored digital read back signal.

Abstract: Methods and systems for sensing a position of a transducer head with respect to a storage medium. One method includes generating a read signal from a servo track stored on a magnetic storage medium. The servo track includes servo frames of magnetic flux transitions forming detectable servo marks, the servo marks forming a tone field of repeating servo marks oriented at a first azimuth angle and a mid-frame synchronization mark incorporated within the tone field, wherein the tone field provides a metric reference for dimensional measurements between features within the servo frame(s). The number of servo marks in the tone field of each servo frame along a longitudinal direction of the servo track before the mid-frame synchronization mark and after the mid-frame synchronization mark varies with lateral position.

Abstract: A location within a cycle is determined by reading a portion of a cyclic bit sequence, the bit sequence containing several interspersed bit-group sets that each contain a plurality of series that each consist of several consecutively-placed identical bit-groups. On a data surface in a disc drive, each bit group can be stored and accessed in unused bits of each servo sector's digital portion.

Abstract: A method and apparatus for providing combined radial and timing multislot self-servowrite propagation is disclosed. Radial bursts are combined with each timing mark and requires only three recovery/read-write spacing allocations per sector. The channel operates without requiring the writing of any bursts between reading radial bursts.

Abstract: A method for formatting a magnetic recording disk with patterned nondata islands having alternating magnetization polarity in the along-the-track direction involves clocking write pulses to switch the magnetization direction of alternate, i.e., every other, nondata island. The clocking is controlled by the previously determined phase of the regions containing the nondata islands and the known offset along-the-track between the read head and write head. In each nondata region, every other nondata island in the along-the track direction has the same magnetization direction, with adjacent nondata islands having antiparallel magnetization directions. The disk may be either a horizontal magnetic recording disk, wherein the antiparallel magnetization directions are in the plane of the recording layer and parallel to the along-the-track direction, or a perpendicular magnetic recording disk, wherein the antiparallel the magnetization directions are “into” and “out of” the recording layer.

Abstract: A data storage device such as a disc drive is described that has a controller chip with an integral embedded read/write channel on the chip. The chip includes a built in test capability for testing the controller logic via the device microprocessor and a nonreturn to zero test FIFO and control logic module. The module includes an internal first in/first out buffer (FIFO) that has variable data speeds and is provided on the chip to provide the test capability thereby permitting testing that would otherwise be difficult to perform.

Abstract: A vibration extraction processing unit extracts a deflection component synchronous with a rotation from a clock signal of a non-contact sensor so as to correct a clock jitter. A clock generating unit generates a clock signal of any format frequency preliminarily set up according to the clock signal from the vibration extraction processing unit. A sector correction processing unit measures an error due to the frequency deflection so as to correct the writing start position for the format pattern signal of each sector containing a servo frame signal stored in a memory according to the measured error. Writing processing units read out the corrected format pattern signal from the memory according to a synchronous signal corresponding to a single turn of a disc and a format frequency clock signal and then writes into a disc medium face.

Abstract: A method for operating a disk drive having timing marks (TMs) on the disk that are chosen to reduce the probability of misidentification of a TM in the presence of read errors. The disk drive searches for TMs within a fixed TM search window which extends past the TM on the disk. A TM preferably maximizes the post-shift sliding distance for m post-shifts of the TM pattern, where m corresponds to the TM search window boundary. In this manner, the probability of a misidentification of the TM due to a post-shift having a small distance from the TM pattern is reduced. The TM pattern also provides pre-shift error resistance.

Abstract: A high-speed, wide bandwidth data detection circuit includes a phase detection module, a data detection module, a loop filter, and a voltage controlled oscillator. The phase detection module is operably coupled to produce a controlled current based on a current mode mathematical manipulation of differences between an incoming data stream and a recovered clock. The phase detection module performs the current mode mathematical manipulations and produces the controlled current in the current domain. The data detection module is operably coupled to produce the detected data based on the incoming data stream and the recovered clock. The loop filter is operably coupled to convert the controlled current into a controlled voltage. The voltage controlled oscillator is operably coupled to convert the control voltage into the recovered clock.

Abstract: A disk drive includes an actuator assembly having a read/write head, a spindle motor, a disk mounted for rotation on the spindle motor, a wedge-to-wedge timer and a sector size selector. The disk includes a recording surface having a plurality of tracks and each track includes a plurality of servo wedges. The recording surface has at least one data sector between circumferentially adjacent servo wedges on each track. The wedge to wedge timer measures the time elapsed between at least two successive detections of circumferentially adjacent servo wedges and outputs a wedge-to-wedge correction signal that is dependent upon the measured elapsed time. The sector size selector outputs a sector size signal that changes according to the wedge-to-wedge correction signal. In turn, the sector size signal determines the size of the next data sector on the recording surface of the disk.

Abstract: Disclosed is a servo writer when, detecting an abnormality from servo signals written on a tape-shaped recording medium, such as a magnetic tape, corrects the abnormality through a simplified procedure, thereby allowing for an increase in the transport speed of media in the future. The servo writer includes a write head for writing servo signals, a verifying head positioned downstream of the write head in a transport direction of the tape, for reading the servo signals written by the write head in order to inspect the servo signal, an inspection section for checking whether or not the servo signals being read by the verifying head contain any abnormality, and an overwrite head positioned downstream of the verifying head in the transport direction, for overwriting a portion where the abnormality is detected by the inspection section.

Abstract: A method of writing product servo sectors to a disk of a disk drive is disclosed. A plurality of spiral tracks are written to the disk, wherein each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. During the product servo writing process, the sync marks in the spiral tracks are detected and a sync mark reliability metric is generated, wherein the sync mark reliability metric represents a probability that the sync mark was detected accurately. A timing recovery measurement is generated in response to the detected sync marks and the sync mark reliability metrics. A servo write clock is synchronized in response to the timing recovery measurement and used to write the product servo sectors to the disk while serving on the spiral tracks.

Abstract: A PLL circuit comprises a frequency comparator for detecting a phase difference based on a difference in frequencies between a reproduced data pulse and a clock generated by a VCO; a phase comparator for detecting a difference in phases between the reproduced data pulse and the VCO clock; a selector for selectively outputting a signal supplied from the frequency comparator; a first charge pump for increasing/decreasing the output voltage on the basis of the output from the selector; a second charge pump for increasing/decreasing the output voltage on the basis of the output from the phase comparator; a loop filter for eliminating unnecessary components included in a signal obtained by adding the output from the first charge pump and the output from the second charge pump; and a VCO for generating a clock of a frequency corresponding to the output voltage of the loop filter.