Abstract: Methods are provided for limiting channel control values, such as servo automatic gain control (AGC) values and/or servo phase lock loop (PLL) values, within respective desired ranges. Keeping such values within desired ranges improves servo demodulation robustness.

Abstract: Systems are provided for limiting channel control values, such as servo automatic gain control (AGC) values and/or servo phase lock loop (PLL) values, within respective desired ranges. Keeping such values within desired ranges improves servo demodulation robustness.

Abstract: The present invention is directed to a method and apparatus for performing seek operations in a disk drive having a disk surface with spiral servo information written thereon. In one embodiment, a disk surface is provided with a read head associated therewith. The disk surface has spiral servo information written thereon. The read head generates a read signal envelope when reading the spiral servo information. A plurality of integration windows is provided. The plurality of integration windows have a standard interval therebetween. A position error signal is generated based upon a location of a read signal envelope within an integration window. The interval between adjacent integration windows is adjusted from the standard interval to generate a position error signal. The read head is moved in a radial direction based upon the position error signal. This process may be repeated to seek across the disk surface.

Abstract: A head position is demodulated by two-phase servo signals of PosN and PosQ from output of the head, so as to acquire a more accurate demodulated position. Saturation of PosN and PosQ is judged from the ratio of each absolute value of PosN and PosQ, and a different demodulating method is used for a saturated area and for an unsaturated area, and a demodulating formula is constructed so that the edge of each demodulating area matches with the edge of the adjacent demodulating area. Also saturated/unsaturated is judged by comparing the absolute value of PosN and the absolute value of PosQ, and determining whether the ratio thereof is greater or small than a predetermined saturation coefficient r.

Abstract: Position information PosN and PosQ are compared and position information Pos1 and Pos2 in which influences of an error of a position sensitivity gain appear oppositely are calculated. Subsequently, a weight gain G1=M and a weight gain G2=(1?M) are obtained from the position information Pos1. A multiplication value obtained by multiplying the third position information Pos1 by the weight gain G1 and a multiplication value obtained by multiplying the fourth position information Pos2 by the weight gain G2 are added and synthesized, thereby calculating a decoded position.

Abstract: Method and apparatus for recording data on a magnetic recording medium and writing data to a computer bus in which the data is divided into words of a predetermined length, a signal is generated for each data word, having an amplitude which is representative of the value of the data word, and this signal is then recorded to the magnetic recording medium or written to the computer bus. Complementary method and apparatus is provided for reading the data from the magnetic recording medium and the computer bus.

Abstract: A method of encoding and decoding data involving the simultaneous application of pulse width modulation and pulse position modulation systems to data intended for storage on a magnetic disk medium.

Abstract: An object of the present invention is to provide a digital amplifier which is capable of preventing a reproduction of an analogue audio signal from a loud speaker, when an output sound volume from the loud speaker is set to zero and when inputting of a digital audio signal or an input signal is stopped. In order to achieve the object, in the digital amplifier of the present invention, a silent PWM signal output section 7 outputs a PWM signal having a duty ratio of 50%, instead of a PWM signal generated by the PWM signal generating section 6, in the following cases: the factor detecting section 3 detects that the digital audio signal is multiplied by the factor “0” in the gain regulation section 2, the silent signal determining section 4 determines that the signal input from the reproducing unit 13 is stopped, and the silent signal determining section 4 determines that the digital audio signal is a signal at a silent level.

Abstract: A hard disk controller generates a read gate signal RG which has a predefined read start time and read end time set based on a sector pulse as a reference. A read data demodulation unit reproduces read data from a readout signal of medium by executing a read based on the read gate signal RG. A read gate optimization unit detects errors of read data demodulated by the data demodulation unit while varying the read start time and the read end time of the read gate signal RG, determines the read start time and the read end time at which the detected errors will be minimized and sets these in the read gate generation unit.

Abstract: A method of encoding and decoding data involving the simultaneous application of pulse amplitude modulation, pulse width modulation, and pulse position modulation systems to data intended for storage on a magnetic disk medium.

Abstract: Digital data recording apparatus includes a modulator for modulating a recording clock by a recording data. A reference voltage and a reference current in signal processing are set based on a reference clock having a multiple cycle of the cycle of the recording clock when the reference clock is supplied via a rotary transformer. A demodulator demodulates a modulation signal supplied via the rotary transformer to produce a demodulation signal, from which a recording signal is generated for recording on a recording medium. The demodulator obtains a modulation signal and an inverted modulation signal from which first and second saw-tooth wave signals are produced when the reference current is supplied. A mixer mixes the first and second saw-tooth wave signals, and the demodulation signal is obtained, based on the mixer output and the reference voltage.

Abstract: A disk driver writer precompensation system modulates the write current waveform based on a pattern of data bits magnetically recorded on a medium in order to adjust the timing of magnetic transitions recorded on the medium.

Abstract: A method of encoding and decoding data involving the simultaneous application of pulse amplitude modulation, pulse width modulation, and pulse position modulation systems to data intended for storage on a magnetic disk medium.

Abstract: Automatic-signal-selecting is provided for controlling which output is supplied from a switch, i.e., a digital signal or an analog signal. The control is carried out based on information selected by manual-signal-selecting and information judged by copyright-information-judging. This structure allows a recording and reproducing apparatus to record the content-prohibited from being recorded in a digital form according to copyright information-in an analog form.

Abstract: A data storage device for retrieving data includes a controllably positionable head and a storage medium having servo information comprising a phase pattern having a first frequency and a PES pattern having a second frequency, the second frequency being different from the first frequency.

Abstract: Here is disclosed an information recording and reproducing apparatus comprising a multi-phase quadrature angular modulator for subjecting a signal to be written on a recording medium to multi-phase quadrature angular modulation to generate a modulated signal expressing information in phase difference and frequency difference, a quantizer for generating a discrete signal by making discrete the amplitude of the modulated signal generated by the quadrature angular modulator with reference to a certain level, a write head for writing the output signal of the quantizer onto the recording medium, a read head for reading information written on the recording medium, a read compensate circuit for compensating the phase and amplitude of a signal readout of the read head, and a multi-phase quadrature angular demodulator for demodulating a signal supplied from the read compensate circuit by subjecting it to multi-phase quadrature angular demodulation.

Abstract: A phase locked loop (PLL) circuit is disclosed comprising a phase detector for generating a phase error between an input oscillating signal and an output oscillating signal. A fractional frequency synthesizer (FFS) generates the output oscillating signal in response to the phase error, wherein the FFS comprises an input for receiving a reference oscillating signal, and a fractional divider responsive to variables I and Fr. The variable I is an integer value, and the variable Fr is a fractional value, both of which are generated in response to the phase error.

Abstract: In a coding method which does not restrict a run length of “1” while data is recorded/reproduced, there are such a drawback that when an error correction is carried out, a total number of error data to be corrected is increased, and also errors of not-detectable data are increased. While data is coded, a continuous number of “1” contained in a code word is limited, and then an error correction is carried out inside a coding/decoding process operation. Thus, a recording/reproducing apparatus having a small number of decoding errors is available.

Abstract: A method and apparatus for generating a position information signal for the head of a hard disk drive. The disk has a track which contains a plurality of servo bursts that allow the head to be centered with the centerline of the track. The servo bursts are first sensed and an upper and a lower threshold values, based on the values of servo bursts, are generated. A position error signal based on the upper and lower threshold and the values of the servo bursts are generated and stored in a memory device.

Abstract: A robust and efficient method for determining the location of a transducer head in a mass storage system. A position-indicative signal characterized by a fundamental frequency F is received from a data path including the transducer head. Energy in the signal at frequencies smaller than F/10 is substantially attenuated by a special filter, which may be an analog or digital differentiator. A sequence of bits indicative of the transducer head position indicator is then extracted from the digitized, filtered signal.

Abstract: A disk driver writer precompensation system modulates the write current waveform based on a pattern of data bits magnetically recorded on a medium in order to adjust the timing of magnetic transitions recorded on the medium.

Abstract: An information storage medium includes a wobbled track containing a wobble modulated in correspondence with playback control information. The playback control information contains address data. Part of the address data contains at least one item of sync information. The frequency of the wobble changes at the boundary of the sync information.

Abstract: A recording equalizer for correcting a write timing of magnetic information when the magnetic information is recorded with a magnetic recording head on a magnetic recording medium, includes a buffer for storing a recording object bit and bits before and after the recording object bit and a calculator for calculating a precompensation parameter using the bits stored in the buffer. The calculator calculates the preconpensation parameter of the recording object bit by linearly adding influence of a transition existing at a two-previous bit of the recording object bit, influences of a transition at a one-previous bit of the recording object bit and influences of a transition existing at one-following bit of the recording object bit and further adding an offset. The offset is determined to a value such that a write timing of the magnetic information is corrected always in a delaying direction.

Abstract: There is disclosed a pattern matching technique for comparing (a) signals representing detected magnetically recorded characters against (b) a set of predetermined idealized reference signals representing those characters. The pattern matching techniques involves a correlation of coefficients. The characters are encoded as data in the form of binary signals in which one type of bit has a greater width and the other type of bit has a lesser width. Techniques are disclosed to compensate for various distortions in the demodulated characters from the magnetic stripe. These distortions may be due to a loss of magnetic head resolving power, contamination and scratches on the magnetic medium and equipment drift. Techniques are disclosed for normalizing the width of each segment that corresponds to a character. Techniques are also described for detecting the starting point of the segment that represents a character. A technique is described to avoid errors due to abnormal signal peaks.

Abstract: A magnetic card reader for causing a magnetic card to make a move relative to a magnetic head and reproducing data on the magnetic card by the magnetic head, said magnetic card reader includes an amplifier for amplifying a magnetic signal provided by the magnetic head, a peak detection section for detecting a peak point of amplifier output from the amplifier output, a data reproduction section for reproducing digital data based on the interval between the peak points, an anomaly detection section for detecting an anomaly of the peak point interval and an output value storage section for converting the amplifier output from analog form into digital form every predetermined time and storing the provided data.

Abstract: Here is disclosed an information recording and reproducing apparatus comprising a multi-phase quadrature angular modulator for subjecting a signal to be written on a recording medium to multi-phase quadrature angular modulation to generate a modulated signal expressing information in phase difference and frequency difference, a quantizer for generating a discrete signal by making discrete the amplitude of the modulated signal generated by the quadrature angular modulator with reference to a certain level, a write head for writing the output signal of the quantizer onto the recording medium, a read head for reading information written on the recording medium, a read compensate circuit for compensating the phase and amplitude of a signal readout of the read head, and a multi-phase quadrature angular demodulator for demodulating a signal supplied from the read compensate circuit by subjecting it to multi-phase quadrature angular demodulation.

Abstract: Position information PosN and PosQ are compared and position information Pos1 and Pos2 in which influences of an error of a position sensitivity gain appear oppositely are calculated. Subsequently, a weight gain G1=M and a weight gain G2=(1−M) are obtained from the position information Pos1. A multiplication value obtained by multiplying the third position information Pos1 by the weight gain G1 and a multiplication value obtained by multiplying the fourth position information Pos2 by the weight gain G2 are added and synthesized, thereby calculating a decoded position.

Abstract: The present invention relates to a stop section detecting method of various magnetic recording media such as a magnetic card and a data demodulating method for magnetic recording data in the case in which magnetic recording data written to the magnetic recording media are to be demodulated.

Abstract: The invention is a modulation system that encodes symbols in accordance with a modulation code which, for a given communications channel, produces a signal that at the decoder includes maximized sample timing information in each encoded symbol. For systems that use PLLs to control a sample timing clock, the sample timing information is the average or squared slope. The modulation code used for a given system is selected based on the target response h(x) of the associated communications channel, such that h (x)*rk exceeds a predetermined threshold value, where “*” represents convolution and rk is a modulation code symbol. To reduce the bit overhead, or code rate, the inventive modulation system provides more modulation code symbols at the start of a data block, or sector, when system jitter is expected to be relatively high in response, for example, to the movement of a read head.

Abstract: A new synchronous Partial Response Maximum Likelihood (PRML) servo is provided for a high track-per-inch disk-drive system. To increase the data capacity in hard disk drives (HDD), one can shorten the servo format and/or increase the track density. The new servo system has circuits that allow a high-performance and accurate system for positioning the read-write heads. The major circuits include burst demodulation, Viterbi detection, timing synchronization, and spin-up search. A highly linear discrete-fourier-transform (DFT) burst-demodulation circuit can demodulate high-density and low-signal-to-noise-ratio (SNR) position bursts. The Viterbi detection circuit includes a sync-mark detector and a Viterbi detector that are matched to at least two sets of Gray code ( e.g., ¼ rate and {fraction (4/12)} rate) and pruned accordingly. The timing synchronization circuit includes phase restart and interpolating timing recovery (ITR) circuits to implement a fully digital timing recovery.

Abstract: A new technique for Hard Disk Drive (HDD) servo-burst demodulation is provided. A 4-samples per dibit Discrete Fourier Transform (DFT) amplitude estimation is used to calculate the read-head servo-position error signal. Comparatively, the conventional method of burst demodulation—called burst integration—typically uses more than 8 samples/dibit. Consequently, the new 4-samples/dibit DFT burst-demodulation scheme requires fewer samples per dibit than does burst integration, thus reducing the disk space occupied by the burst data while increasing the performance as compared to burst integration. Furthermore, the DFT scheme does not require the samples to be synchronized to any particular points of the servo burst, and can include an averaging algorithm that further improves performance for a given Signal to Noise Ratio (SNR). Moreover, the same sample-clocking circuit that detects the Gray Code servo information can also implement the DFT burst-demodulation scheme to demodulate the servo burst.

Abstract: A magnetic medium comprises a magnetic disc having a read surface that has a plurality of tracks, at least some having servo sectors. The servo sectors comprise a plurality of magnetic irregularities, such as pits or regions of reduced magnetic coercivity, arranged in a servo pattern along the servo sector at a servo frequency. A magnetic pattern is recorded in the disc along the servo sector at a high carrier frequency. A process for manufacturing the servo pattern and for recovering servo data from the servo pattern are also described.

Abstract: There is provided a digital data recording apparatus, which can transmit a recording data via a rotary transformer without receiving an influence of a recording data rate and low frequency cut-off, and can perform high-quality digital recording with a simple configuration.

Abstract: First and second synchronous words having respective numbers of times of inversion different from each other in NRZI conversion are generated in a synchronous word generation portion, and first and second code word series data are generated by arranging code word data generated making reference to a run-length coding table after these two synchronous words. With respect to the first and second code word series data, DSV calculation results stored in two DSV calculation peak value memories corresponding to these data are compared with each other by a peak value comparison portion. Based on a comparison result, the code word series data having a smaller direct-current component generated in NRZI conversion is selected.

Abstract: A method of detecting a position on a disk is applied to a disk which is time-divisionally recorded with a data region and a servo region based on a signal read from the disk, where the servo region is recorded with a servo pattern having a length of consecutive “0”s longer than a length of consecutive “0”s existing in the data region, and the servo pattern has three or more zones with consecutive “0”s. The method includes the steps of (a) digitizing the signal read from the disk and slicing at a predetermined level so as to convert the signal into “0” or “1”, and (b) detecting the servo pattern when two zones with consecutive “0”s are detected from information converted by the step (a).

Abstract: There is provided a data storage device concurrently allowing storage of data that can be reproduced in higher quality and storage of data that can be used also in a data transmission path with a lower transfer speed. The data storage device comprises an A/D converter 103 for sampling analog audio signals based on a sampling frequency, a DSP 104 for compressing sample data sequentially output from the A/D converter 103, a storing and reading control unit 107 for storing the compressed data sequentially output from the DSP 104, and a control unit 105 for controlling the DSP 104 and the storing and reading control unit 107 for dividing the sample data sequentially output from the A/D converter 103 into a group under odd number of turns and a group under even number of turns, compressing the groups at each different compression rate and storing them on different storage areas A and B, respectively.

Abstract: Data which is greater in capacity than the prior arts is recorded and reproduced on and from a low-capacity recording medium. In a large-capacity flexible disk device having head sliders (4) loaded with a low-capacity magnetic head and a high-capacity magnetic head, a control means such as a CPU 14 and the like for controlling the low-capacity magnetic head and the high-capacity magnetic head is provided so that a high-capacity track format is written in a low-capacity recording medium (1) by the low-capacity magnetic head to record information, and the information recorded on the low-capacity recording medium (1) in a high-capacity track format is reproduced by means of the high-capacity magnetic head.

Abstract: A method of generating a position error estimate generates a phase field signal and a position error field signal. A set of operations is performed on the phase field signal and the same set of operations is performed on the position error field signal. The result obtained by performing the set of operations on the position error field signal is divided by the results obtained by performing the set of operations on the phase field signal. The result of the division is the position error estimate. In addition, a demodulation circuit is provided that utilizes field ratioing.

Abstract: In a digital information recording and reproducing apparatus of a rotary magnetic head type for selecting and recording a plurality of digital information signals having different transmission rates and for selectively reproducing the recorded signal, a high-rate digital information signal and a low-rate digital information signal are inputted for selection of either one thereof to be converted by a recording-system encoder into two channels of recording signals. When recording the high-rate signal, the rotary drum is turned at a rotation speed and the magnetic tape is fed at a feed speed (V1) to conduct 4-track azimuth recording of the signals for each rotation of the rotary drum by the first to fourth magnetic heads.

Abstract: There is disclosed a recording method for performing a DSV control while recording a recording signal generated by inserting a synchronous signal for decoding reproduction data into every predetermined number of code words in a code word string satisfying a predetermined run length restriction rule and to be outputted into a recording medium, when a plurality of coding tables are used to convert an input data word of p-bits to a code word of q-bits (q>p), and the code word string obtained by directly coupling the code words is recorded and reproduced in a recording medium such as an optical disk and magnetic disk, or transmitted via a transmitting portion, wherein the p-bits are 8 bits, the q-bits are 15 bits, and the predetermined run length restriction rule stipulates that a minimum run length of the signal obtained by NRZI-converting the code word excluding the synchronous signal is 3T, and a maximum run length is any one of 11T, 12T, 13T, and 14T.

Abstract: An asynchronous demodulator and method is provided which determines a position error of a read head relative to a position on a medium in a storage device. The read head generates a-read signal as the read head passes over a servo area on the medium. The demodulator generates a normal demodulating signal that is asynchronous with the read signal and a quadrature demodulating signal that is ninety degrees out of phase with the normal demodulating signal. The read signal is multiplied by the normal demodulating signal and the quadrature demodulating signal to produce a normal position signal and a quadrature position signal. The demodulator produces a position error magnitude and a position error direction based on the normal position signal and the quadrature position signal.

Abstract: A 6-bit output code word is generated in response to every 4-bit input code word by referring to a set of encoding tables. The encoding tables contain output code words assigned to input code words, and contain encoding-table designation information accompanying each output code word. The encoding-table designation information designates an encoding table among the encoding tables which is used next to generate an output code word immediately following the output code word accompanied with the encoding-table designation information. The generated output code words are sequentially connected into a sequence which follows run length limiting rules. The run length limiting rules are changed between RLL(1, 7) and RLL(1, 8) in response to auxiliary information to superimpose the auxiliary information on the sequence of the generated output code words.

Abstract: Automatic-signal-selecting is provided for controlling which output is supplied from a switch, i.e., a digital signal or an analog signal. The control is carried out based on information selected by manual-signal-selecting and information judged by copyright-information-judging. This structure allows a recording and reproducing apparatus to record the content-prohibited from being recorded in a digital form according to copyright information-in an analog form.

Abstract: A magnetic storage apparatus is provided with unit for identifying the frequency of overwriting storage at the time of overwriting in the same data sector, and depending on the frequency of overwriting, a code for coding or a scrambler initial value is changed at every overwrite operation. The modulation code has the same code rate so that a data length does not change at every write operation. A number corresponding to the present modulation code of each data sector is stored on a memory, and the aforesaid number is also written as an additional bit in the data sector on a medium. Data are read only when the modulation coding number on the memory and the modulation coding number on the medium, which are compared, agree with each other. If they do not agree, offset reading is performed until they agree, and then the read operation is performed.

Abstract: A helical scan magnetic recording/reproducing apparatus incorporating an MR head to serve as a reproducing magnetic head is arranged to convert data which is recorded on a magnetic tape into data in the form of DC-free code trains. The magnetic recording/reproducing apparatus is provided with a high-pass filter for attenuating low-frequency components of a reproduced signal detected by the MR head. Moreover, a demodulating circuit is provided which demodulates data in a state before data is converted into the DC-free code trains from the reproduced signal, in which the low-frequency components have been attenuated by said high-pass filter. As a result, noise (thermal asperities) in a low-frequency region caused when the magnetic tape and the MR head are brought into contact with each other is removed so that a reproduced output free from excessive noise is obtained. The high-pass filter is, for example, a rotary transformer mounted on rotational drum.

Abstract: A magnetic card reader for causing a magnetic card to make a move relative to a magnetic head and reproducing data on the magnetic card by the magnetic head, said magnetic card reader includes an amplifier for amplifying a magnetic signal provided by the magnetic head, a peak detection section for detecting a peak point of amplifier output from the amplifier output, a data reproduction section for reproducing digital data based on the interval between the peak points, an anomaly detection section for detecting an anomaly of the peak point interval and an output value storage section for converting the amplifier output from analog form into digital form every predetermined time and storing the provided data.

Abstract: An asynchronous demodulator and method is provided which determines a position error of a read head relative to a position on a medium in a storage device. The read head generates a read signal as the read head passes over a servo area on the medium. The demodulator generates a normal demodulating signal that is asynchronous with the read signal and a quadrature demodulating signal that is ninety degrees out of phase with the normal demodulating signal. The read signal is sampled to produce a series of digital read values which are multiplied by the normal demodulating signal and the quadrature demodulating signal to produce a plurality of normal and quadrature sample values. The demodulator produces the a position error magnitude and a position error direction based on the plurality of normal and quadrature sample values.

Abstract: An integrated circuit servo system demodulator that incorporates a high speed gain stage with DC offset cancellation. The gain stage receives a differential voltage signal representing a servo burst and converts the differential voltage signal to a differential current signal by a transconductance amplifier. The differential current signal is full-wave current rectified and converted to a full-wave rectified voltage signal by a transimpedance amplifier. A DC offset cancellation circuit is coupled between the full-wave current rectifier and transimpedance amplifier and functions to mirror and subtract, from the rectified current signal directed to the transimpedance amplifier, any DC leakage current developed by the rectifier which would generate a DC offset voltage through the transimpedance amplifier.

Abstract: A head position signal demodulator that demodulates a position signal indicating the position of the magnetic head in the disk radius direction based on a servo pattern recorded on the magnetic disk includes a waveform shaping circuit which shapes an input signal obtained from the magnetic head according to the servo pattern and a phase comparison circuit which compares a phase of an output signal of the waveform shaping circuit and a phase of a reference signal and outputs a phase difference signal. The head position signal demodulator also includes a position signal generation circuit that generates a position signal of the magnetic head based on the phase difference signal, and a phase shifter which changes the phase of the reference signal during micro jogging, for an amount of the phase which has been set according to the amount of the micro jogging.

Abstract: A synchronous digital demodulator and method for demodulating a read signal including a user data waveform and a servo waveform which are generated by a read head as the read head passes over a user data area and a servo area, respectively, on a medium in a storage device. The user data waveform is converted to a series of digital user data values at a user data sample rate. The series of digital user data values are then applied to a user data detector circuit. The servo waveform is converted to a series of digital servo values at a servo sample rate, which is independent from the user data sample rate. The series of digital servo values are demodulated synchronously with the servo waveform to produce a position error value indicative of a position error of the read head relative to a location on the medium.