Abstract: A selectively adjustable impedance boosting circuit for a magneto-resistive head in a disk drive to compensate a frequency pole by introducing a zero in proportion to the resistance of the magneto-resistive element and with selectable circuit parameters to further adjust the pole compensation. The invention includes selectively adjusting the sensitivity of the pole compensation to changes in the resistance of the head, selectively adjusting the peak compensation, and adjusting the frequency of the compensating zero.

Abstract: An improved write drive circuit which includes a discharge circuit added to the base of the bottom transistors of the H-bridge to prevent excessive overshoot and ringing while allowing for higher data rates. The discharge circuit is turned on after the head voltage or current reaches an overshoot condition. In preferred embodiments, the discharge circuit includes variable discharge capability by selecting one or more parallel drive transistors or varying a variable delay in the discharge circuit or any combination of both variables. Both can be controlled by a word written to the disk drive pre-amp over the serial control port.

Abstract: A magnetic tape recording system employing a single bump read-while-write head, methods of minimizing crossfeed signals between the read and write channels of magnetic tape recording systems, and electronic circuitry to implement such methods.

Abstract: In a signal processing apparatus according to the present invention employing PRML technology to reproduce a code sequence recorded on a magnetic recording medium, the maximum likelihood code sequence of a readback signal is obtained by using a likelihood function based on a conditional distribution of each branch corresponding to a quantization level. A plurality of conditional distributions having various deviations are provided, and a suitable conditional distribution is selected in accordance with the characteristic of the readback signal, the signal reproduction performance can be improved. Especially set is a conditional distribution for the nonlinear phenomenon, such as the nonlinear transition shift (NLTS) and the partial erasure (PE). Therefore, it is possible to prevent the signal processing performance deterioration, caused by the nonlinear phenomenon, which tends to appear more often in consonance with the increase in the recording density of a magnetic recording medium.

Abstract: A method of writing data onto magnetic thin film media commonly employed in magnetic disk drives at sub-ambient temperatures is disclosed. The method employs a thin film capacitor having a magnetoelectric element as its dielectric in a GMR read/write head to produce magnetic fields. To get the maximum magnetic field from the thin film capacitor, the thin-film capacitor is cooled via a thermoelectric cooling device present in the GMR read/write head of the magnetic disk drive. The magnetic field produced by the thermoelectrically cooled thin film capacitor structure is capable of writing data onto magnetic media with increased bit densities or coercivity.

Abstract: A data storage apparatus for magnetic recording and regeneration on a medium. Only in case of a dibit or Tri-bit code sequence in MTR codes having a restricted number of magnetic transition consecutive, a write unit records the interval of the magnetic transition on the medium with an extension of &Dgr;T relative to the original magnetic transition interval. For the maximum likelihood detection after equalization of the medium read signals, a read unit adds to an expected value of the maximum likelihood detection an amplitude error &Dgr;V arising from the extension record of the magnetic transition interval relative to the original magnetic transition interval. A parameter regulation unit regulates and sets &Dgr;T and &Dgr;V by use of test patterns.

Abstract: A read channel for use in a disk drive having an MR head. The read channel comprises a compensation device which has a high-pass filter (HPF) for compensating a thermal asperity (TA). The read channel suppresses level changes of a data signal which have resulted from TA disturbance present in the data signal. The read channel has a switch circuit connected to the input of the HPF, for canceling the DC undershoot present in the data signal. The switch circuit maintains the DC level of the data signal at zero level while a thermal asperity is being detected in the data signal.

Abstract: A method for compensating digital samples of an asymmetric read signal is presented. The method involves reading a digital sample of an asymmetric read signal V(t) (160), generating a compensated sample at least when the digital sample requires compensation (164), and outputting either the digital sample (168) or the compensated sample (166). Also presented is an asymmetry correction block (158) of a read channel (144) of a disc drive (110) that includes an input (200), a level detector (202), a compensator (204), and an output (208). The level detector (202) and the compensator (204) receive the digital sample through the input (200). The level detector (202) determines whether the digital sample requires compensation. The compensator (204) generates a compensated sample at least when the digital sample requires compensation. The output (208) selectively outputs either the digital sample or the compensated sample.

Abstract: When a magnetic tape cassette which may include a memory in cassette (MIC) device storing a system log therein is loaded, on the basis of a system log allocation flag read out from the magnetic tape it is judged which one of the magnetic tape and the MIC should be used as a location of the system log to be preferentially used by the tape drive device. If the system log to be preferentially used exists in the MIC, but it is impossible to read out the system log from the MIC, the system log allocation flag of the magnetic tape is rewritten so that the system log to be preferentially used exists on the magnetic tape, whereby the tape cassette is afterwards handled as a tape cassette with no MIC on the system.

Abstract: A method and apparatus are provided for implementing an in-situ digital harmonic computation facility for direct access storage device (DASD). A digital sequence output of a DASD channel from a constant write frequency field on a disk surface is applied to a plurality of adders for modulo-n summing the digital sequence. A harmonics computation block provides discrete Fourier transform computing based upon the summed modulo-n digital sequence to produce a plurality of harmonic coefficients. A plurality of estimate functions utilize predetermined ones of the plurality of harmonic coefficients for estimation of predefined conditions in the DASD. The plurality of estimate functions include a flyheight estimate function, a readback signal asymmetry estimate function and a thermal activity estimate function.

Abstract: A new embedded-servo format is proposed for use in disk drives, preferably hard disk drives. It is based on biphase modulation (more generally, p-phase modulation, where p>1) and offers significant advantages, in terms of SNR and timing content, over existing formats. It is shown that for biphase, at the low linear densities typically employed for servo information, near maximum-likelihood performance may be attained by a simple bit-detector consisting of a full-response linear equalizer and a binary slicer. When compared with an optimal detector for the commonly used technique of dibit signalling, a SNR gain of some 4 dB is achieved. The same equalizer may be used as the basis for near-maximum-likelihood Position Error Signal (PES) amplitude estimation and timing recovery. Investigations carried out on a practical servo demodulator based on a 5th order analog filter show that, at typical linear densities, this ideal performance is closely approached.

Abstract: A write circuit selectively provides a write current through a write head in first and second opposite directions. The write circuit is connected to the write head by an interconnect, and has a positive supply level and a negative supply level. A first voltage source provides a first control voltage, and a second voltage source provides a second control voltage. A first resistor is provided between the first voltage source and the interconnect for impedance matching to the interconnect, and a second resistor is provided between the second voltage source and the interconnect for impedance matching to the interconnect. The first and second control voltages provide a transient voltage to the interconnect and provide a subsequent steady-state voltage to the interconnect.

Abstract: A bias current for a magnetoresistive read head is selected by defining a tuning range based on a maximum and a minimum bias current value for the head. A plurality of read operations are iteratively performed using a different bias current value over the tuning range for each iteration. The results of each read iteration are measured and a bias current is selected on the basis of the read error rates, and particularly those bias currents associated with the lowest read error rate.

Abstract: To provide a magnetic recording method and apparatus which utilize a spin vortex as a recording unit and which enables high density recording, spin vortices (2) are recorded on a recording medium (1) such that the spin vortices (2) are aligned to form a recording track (3). The recording medium (1) is formed of a magnetic super-thin film, and positive and negative recorded spin vortices (2) are aligned thereon.

Abstract: A disk drive with the capability to prevent off-track writing with reduced false triggering is described. An improved method of predicting the position of a head is used to determine whether the head is on or off-track. A position error signal at an nth servo position Pn and a velocity Vn at the nth servo position (Vn=Pn−Pn−1) are calculated using values read at the nth and n−1 head positions. Based on these Pn and Vn and on the output of the servo controller at the nth servo position Un, the predicted PESn+1 is calculated as: Predicted PESn+1=Pn+Vn+kUn where k is a constant.

Abstract: A pulse-mode data writing protocol is disclosed which reduces the time required to implement a transition in the direction of magnetization of a recording medium, and which reduces the total power required to encode a given data sequence. After a magnetic transition is encoded on the medium by generating a write current pulse through the write head, the write current through the recording head is reduced, thereby utilizing the spatial extent of the write bubble to encode the lack of a transition on the medium. Alternate configurations are disclosed for various scenarios of write bubble size versus maximum cell size, all utilizing the principle of the invention.

Abstract: A disk drive system is disclosed that includes a disk device coupled to control circuitry. The disk device transfers a read signal representing data to the control circuitry, where the control circuitry is configured to receive the read signal and convert it into a data signal. To convert the read signal, the control circuitry samples the read signal to generate read samples. The control circuitry interpolates the read samples using phase error data to generate a first interpolated sample and a second interpolated sample. To generate the phase error data, the control circuitry subtracts the second interpolated sample from the first interpolated sample to generate a first result. The control circuitry subtracts the first interpolated sample from the second interpolated sample to generate a second result. The control circuitry slices the second result to generate a third result. The control circuitry then multiplies the first result and the third result to generate the phase error data.

Abstract: A magnetic recording apparatus having a magnetic recording medium having a recording layer formed on a substrate, the recording layer being constituted by magnetic grains and a nonmagnetic material formed between the magnetic grains, a heating unit configured to heat the recording layer, and a magnetic recording unit configured to apply a magnetic field to the recording layer. The magnetic recording medium, the heating unit and the magnetic recording unit are constituted so as to meet the following relationship: T/RKu(T)<11200/(ln(t)+20.72) where, setting that Ku(T) is magnetic anisotropy energy density of the recording-layer at a temperature T, and Ku(Ta) is that at ambient temperature, RKu(T) represents a ratio Ku(T)/Ku(Ta), and t represents an elapsed time after the magnetic field application is completed.

Abstract: A method of refreshing magnetization of a servo pattern in a magnetic medium within a disc drive is provided, wherein the servo pattern is at least partially defined by physical features of the medium. The method includes reading servo information through a transducer in the disc drive from a first portion of the servo pattern. The transducer is positioned at a radial position relative to the medium based on the servo information. The magnetization of a second portion of the servo pattern is then refreshed at the radial position with a magnetic field generated by the transducer.

Abstract: For any specific, hard disk drive that occupies a specific logical position within a computer system, A Hard Disk Drive Selector is disclosed that permits the replacement of one physically distinct, permanently mounted hard disk drive for another physically distinct, permanently mounted hard disk drive within the specific logical position occupied. The Selector simultaneously controls the addressing traces, the control/command traces and the power supply connections to all hard disk drives connected to it. The selector operates by closing the address, command/control, and power circuits to the chosen hard disk drive while opening these circuits to all other hard disk drives connected to the selector. The choice of hard disk drive is made prior to “booting” the computer system and the choice is maintained until the computer system is turn off.