Abstract: In one general aspect, a communications system as described herein provides a wide-band jamming signal that is digitally created, conditioned, and modified by a processing based system to provide open data channels to authorized parties within a jammed communications band. The communications system modifies and maintains the open data channels to sustain communications between authorized devices. In addition, the communications system provides frequency hopping using the open data channels to supply secure data links to authorized devices within the jammed communications band while denying service to unauthorized communication nodes or devices.

Abstract: A far field radio frequency identification (RFID) tagging and tracking system employing a plurality of continuous wave (CW), unmodulated signals selected from frequencies including a predetermined frequency band, includes a RFID interrogator generating a group of CW unmodulated signals corresponding to a RFID tag and receiving a tag identification (ID) signal sequence uniquely identifying the RFID tag, while the RFID tag includes a power source supplying power to the RFID tag but not including a microprocessor. A corresponding RFID tag and method for operating both the tag and the system are also described.

Abstract: For use in a disk drive, a head comprising a slider having a bottom air bearing surface, a leading edge and a trailing edge; a magnetic transducer mounted by the slider at the trailing edge of the slider; and a protective overcoat adhered to the air bearing surface of the slider and having a leading edge and a trailing edge. The trailing edge of the protective overcoat being spaced from the trailing edge of the slider such that the minimum distance from the slider to the surface of a disk in the disk drive is between the magnetic transducer and the disk surface.

Abstract: For use in a disk drive, a head comprising a slider having a bottom air bearing surface, a leading edge and a trailing edge; a magnetic transducer mounted by the slider at the trailing edge of the slider; and a protective overcoat adhered to the air bearing surface of the slider and having a leading edge and a trailing edge. The trailing edge of the protective overcoat being spaced from the trailing edge of the slider such that the minimum distance from the slider to the surface of a disk in the disk drive is between the magnetic transducer and the disk surface. A method for manufacturing a slider with an overcoat spaced from the trailing edge of the slider includes applying a carbon overcoat to the entire bottom air bearing surface, masking, and oxygen plasma etching exposed portions of the overcoated.

Abstract: A disk drive power manager that compares energy usage with a predetermined profile to select one of several reduced-power operating modes. An energy usage register is updated at regular intervals according to the energy used during each time interval. An attenuated average energy usage value is obtained by attenuating the energy usage measures over time and integrating the results. The average energy level is compared with several predetermined energy threshold profiles to select a full- or reduced-power operating mode. Operating mode selection automatically adapts to the usage pattern to optimally balance power consumption with operational accessibility.

Abstract: A disk drive power manager that compares energy usage with a predetermined profile to select one of several reduced-power operating modes. An energy usage register is updated at regular intervals according to the energy used during each time interval. An attenuated average energy usage value is obtained by attenuating the energy usage measures over time and integrating the results. The average energy level is compared with several predetermined energy threshold profiles to select a full- or reduced-power operating mode. Operating mode selection automatically adapts to the usage pattern to optimally balance power consumption with operational accessibility.

Abstract: A multiple disk drive system having two disk-head assemblies (HDA) internally mounted on a rigid frame and accessible via a common industry-standard interface connector is provided. Each HDA is enclosed in a separate housing which is mounted on the disk drive system frame. A vibration damper mounted on the disk drive system frame physically contacts each HDA housing providing a spring force which minimizes the effects of shock and vibration on the operation of the HDAs. The vibration damper is coated with a low-wear, electrically insulating material to provide electrical isolation between the vibration damper and the HDAs housings. The coating material is chosen to also provide a desired coefficient of friction between the vibration damper and the HDA housings. A single electronic controller board is shared by both HDAs and is mounted on the bottom side of the frame underlying the HDAs. The controller board may implement SCSI or IPI interfaces in either differential or single-ended versions.

Abstract: The present invention demonstrates a rotating media storage system which quickly measures and accurately compensates for thermal and mechanical errors in the position of the data detector with respect to the written data. This is accomplished by measuring the error rate of the written data as a function of the read offset of the detector. Error rates become increasingly large as the sensed noise to signal ratio becomes large. The present invention counts the number of errors detected in reading written data for various read offsets when the data storage system is initially activated. When the number of errors reaches a target rate, the read offset required to produce the target rate is saved. This procedure is performed on either side of the data track. The detector is then centered between the two offsets. During the operation of the storage system, thermal and mechanical errors are introduced into the detector position compensation means.

Abstract: A circuit for concurrently producing low noise electrical output signals which are amplified representations of signals produced by a magnetoresistive (MR) element and protecting said element from electrical short circuits which can occur between said element and its environment. A first feedback loop comprises (a) an input amplifier for amplifying a signal current from the MR element and (b) a source of bias current for biasing the MR element with a bias voltage. An input amplifier is concurrently biased by said current and amplifies a signal current from the MR element for producing a circuit output signal corresponding to dRh/RhRh and in which any differential direct current (dc) output offset error is minimized. (RhRh is the square of the time-averaged resistance of the MR element and dRh is the magnetic-signal-induced change in the resistance of the MR element.

Abstract: A data recording disk file with a voice coil motor (VCM) actuator and a digital servo control system for positioning the read/write heads to selected concentric data tracks includes means for calculating the factor relating acceleration of the heads to VCM input current. This permits each disk file to compensate for any variation in the nominal VCM physical parameters, thus enabling VCMs to be manufactured to less demanding tolerances. The disk file also calculates a unique acceleration factor for each head position during movement of the heads from one track to another, thereby improving the arrival time of the heads to the target track. During an initialization procedure, the disk file performs a track seek, during which VCM current and head velocity information are acquired and used by the microprocessor in the digital servo control system to calculate a value representing an average actual acceleration factor unique to that disk file.

Abstract: A digital servo control system for a data recording disk file receives as input a digital head position error signal (PES) and a digital signal corresponding to the head actuator input signal, and outputs a digital control signal. The control signal is integrated and amplified to provide the input signal to the actuator. The control signal is calculated from estimated values of absolute head position, head velocity and the equivalent actuator input signal required to compensate for constant or very low frequency bias forces. The estimated values are functions of respective predicted values, which in turn are functions of, among other things, constants representing the digital sampling time and physical parameters of the actuator. The updating of the estimated values from the respective predicted values is made with the use of an error term, which is the error between the measured absolute head position and the predicted absolute head position.

Abstract: An improvement to a disk file servo control system removes repeatable error from the read/write head position error signal (PES) during track following. The disk file includes a microprocessor 60 and associated memory devices 62, 64. A table of values of a sine function having a frequency equal to the disk rotational frequency is stored in a memory device. The microprocessor 60 receives each sample of PES from the servo control system and values from the sine function table in the memory device and computes a group of tap weights, each tap weight being a function of the PES sample, the value of a sine or cosine function with a frequency at one of the harmonics of the disk rotational frequency, a learning rate factor and the corresponding value of the tap weight for the previous PES sample. For each PES sample, the tap weights in a group are added to generate a repeatable error correction signal U.sub.

Abstract: A servo system for a magnetic disk file having a voice coil motor (VCM) actuator generates a position error signal (PES) from servo information recorded on one of the disks. An electrical model of the VCM is employed through which a measure of the VCM electrical current is passed to generate a simulated PES signal which is continuous even if the regular PES is sampled or intermittent.

Abstract: A servo system generates a velocity profile for moving a load from one position to another by dividing the time during which the load is moving into a plurality of segments, each segment being one half as long as the preceding segment. For each segment a fixed number of desired velocity values are stored and used to control the velocity of the moving load. This results in increasing resolution of the velocity wave as the load approaches its desired position, while not requiring excessive storage capacity for storing the desired velocity values.