Abstract: An alternative time interval is taken of a timing based servo band to determine lateral position of a servo read head. The servo band is arranged in a sequence bursts with non-parallel servo stripes in sequentially adjacent sub-frames of a linear tape. The timing intervals comprise at least a first time interval (A) between a first pair of non-parallel servo stripes of a sub-frame; and an alternative time interval (C) between a pair of non-parallel servo stripes intermediate the first time intervals (A), the alternative interval servo stripes of sequentially adjacent sub-frames comprising a second servo stripe of the first pair, and a first servo stripe of a sequentially succeeding first pair. Position signals are ratios involving the first and second time intervals.

Abstract: Timing based servo bursts of servo frames, in which the frames are arranged to be symmetric with the same number of servo stripes in each burst of a frame, are synchronized by shifting selected bits. For example, servo frames are arranged with four servo bursts with an equal number of servo stripes in each burst, the servo frames comprising two symmetric sub-frames, each sub-frame comprising two bursts of servo stripes that are parallel to each other within a burst, and the bursts are non-parallel with respect to each other; each servo burst is arranged to comprise at least one reference servo stripe; and each servo burst is arranged to comprise at least one shifted servo stripe, wherein the shift is in the same longitudinal direction with respect to at least one reference servo stripe for each burst of a frame and the opposite longitudinal direction for bursts of sequentially adjacent frames.

Abstract: A weighted combining scheme exploits information from two servo channels operating in parallel. A timing-based servo module comprises two synchronous servo channels coupled respectively to receive two digital servo signals read from a data tape. Both channels have outputs for an unweighted parameter estimate and for a measure of the channel reliability. A weight computation module provides first and second weight signals using the measures of channel reliability from the servo channels. An offset computation module provides first and second offset terms which are summed with the unweighted parameter estimates. Multiplying nodes receive the unweighted parameter estimates and the weight signals and outputs offset weighted parameter estimates. A summing node receives the offset weighted parameter estimates and outputs a combined offset weighted parameter estimate to a servomechanism.

Abstract: According to one embodiment, a magnetic recording tape includes a plurality of servo tracks, each servo track comprising a series of magnetically defined bars having an average height of between about 80 microns and about 120 microns, wherein an average stripe angle of the bars is between about 10° and about 25°. A stripe angle is measured between a longitudinal axis of each respective bar and a line oriented perpendicular to a direction of tape travel and parallel to a plane of the tape, wherein an average stripe width of the bars is between about 1.0 micron and about 2.2 microns and an average servo frame length of groups of the bars comprising a servo frame is between about 120 microns and about 180 microns. In more embodiments, a servo format and a system including a servo format are disclosed, along with other embodiments of magnetic tapes.

Abstract: A weighted combining scheme exploits information from two servo channels operating in parallel. A timing-based servo module servo module comprises two servo channels coupled respectively to receive two digital servo signals read from a data tape. Both channels have outputs for an unweighted metric and for a measure of the channel reliability. A weight computation module provides first and second weight signals using the measures of channel reliability from the servo channels. A first multiplying node receives a first unweighted metric and a first weight signal and is operable to output a first weighted metric. A second multiplying node receives a second unweighted metric and a second weight signal and outputs a second weighted metric. A summing node receives the first and second weighted metrics and outputs a combined weighted metric to an LPOS word decoder.

Abstract: According to one embodiment, a system includes a plurality of synchronous servo channels with each synchronous servo channel including a servo reader included in a magnetic head, and logic for applying a plurality of first control signals to a skew-following loop. Each first control signal includes a reference shift value, each reference shift value corresponds to one of a number of hypotheses, and each hypothesis corresponds to one servo band set. The system also includes logic for computing an average difference between lateral position estimates from the plurality of synchronous servo channels, logic for selecting a hypothesis from the number of hypotheses that corresponds to a maximum of the computed average difference, and logic for applying a second control signal to the skew-following loop. The second control signal includes a reference shift value that corresponds to the selected hypothesis. Other systems and methods are also described.

Abstract: A storage medium on which servo patterns are encoded to provide lateral and longitudinal position (LPOS) information is provided. Each of the servo patterns includes a servo frame, including first through fourth bursts, which are each independently modulated with multi-level pulse position modulation (PPM) to encode at least one independent bit per burst.

Abstract: A method for operating a reel-to-reel system of a storage device with a first reel, a second reel, a first motor and a second motor, the first motor drives the first reel and the second motor drives the second reel. The system transports a tape supplied by one of the two reels and taken up by the other reel. A tape velocity and tape tension between the first and reels, and a longitudinal displacement are determined. An estimated state vector depends on the tape velocity, tape tension and longitudinal displacement. A reference state vector depends on a predetermined reference tape velocity and a predetermined reference tape tension. A first control signal and a second control signal are generated dependent on the estimated state vector and the reference state vector. The first motor is controlled by the first control signal and the second motor is controlled by the second control signal.

Abstract: According to one embodiment, a system includes a plurality of synchronous servo channels, where each channel receives a signal from a servo reader of a magnetic head. The system also includes logic for estimating a tape velocity, logic for determining a first and second time instant representing a time at which a flag is generated by a related servo channel, logic for determining a first and second correction term representing a time difference between a time at which a peak of a correlation signal and a time at which the flag occur, logic for calculating a skew error estimate based on a reference shift value associated with a servo band pair being spanned by a head module, and logic for applying a control signal including a skew correction that corresponds to the calculated skew error estimate to the skew-following loop. Other systems and methods are disclosed as well.

Abstract: A storage medium on which servo patterns are encoded to provide lateral and longitudinal position (LPOS) information is provided. Each of the servo patterns includes a servo frame, including first through fourth bursts, which are each independently modulated with multi-level pulse position modulation (PPM) to encode at least one independent bit per burst.

Abstract: Provided are a method, servo channel, and tape drive for recovering servo information from a synchronous servo channel. An interpolator reads samples of a servo signal obtained from a servo reader at a rate of one servo sample per clock interval, to produce up to M interpolated servo samples per clock interval. A first buffer buffers interpolation time instants at which the interpolator generates interpolated servo samples. The interpolated servo samples are buffered in a second buffer and the interpolated servo samples are outputted from the second buffer to a correlator to produce correlation signal samples.

Abstract: A digital control system, and in particular a tape drive system having a track-following servomechanism with a predictor (also referred to herein as a predictor filter), is described. In certain embodiments, the servomechanism includes an actuator, a servo channel, and a predictor coupled to the servo channel. The predictor receives from the servo channel a lateral position estimate signal and determines a modified lateral position estimate signal that reduces a difference, introduced by a tape velocity-dependent delay, e.g., introduced by the servo channel, between the modified lateral position estimate signal and an actual lateral position. The modified lateral position estimate may be used to modify a control signal sent to the actuator.

Abstract: Apparatus is provided for fast-adjustment of the position of a plant in a servo system in which a servo output indicative of the plant position is provided to a positioning system for positioning the plant in dependence on the servo output. The apparatus includes an adjustment signal generator, operable in a fast-correction mode and a shock-compensation mode, for generating an adjustment signal for supply to the positioning system to effect fast positional adjustment of the plant. The apparatus also has an adjustment controller for receiving the servo output. The adjustment controller is adapted to detect from the servo output occurrence of a disturbance affecting positioning of the plant and, in response, to initiate the shock-compensation mode of the adjustment signal generator. The adjustment controller is further adapted to initiate the fast-correction mode of the adjustment signal generator in response to indication of an error in positioning of the plant.

Abstract: A servo pattern, including stripes arranged in servo bursts for use in position error signal (PES) generation, is provided in which a stripe width is narrower than 1.7 ?m and in which the stripes are oriented at an azimuth angle which in absolute value is equal to or larger than 6 degrees.

Abstract: Servo control methods and apparatus for a tape drive. A read/write head reads and writes data on magnetic tape with at least one servo track providing transverse position information. At least two servo readers arranged for reading a servo track associated with the read/write head operate concurrently to generate servo read signals. A position estimator processes each servo read signal to generate a series of position values corresponding to respective time instants indicative of their transverse positions. A servo controller calculates a skew value indicative of tape skew relative to the read/write head and a tension variation value indicative of variation of tape tension. The servo controller is adapted to account for cross-coupling between tape skew and tension variation.

Abstract: A method to position a head module, where the head module comprises at least one servo element and a plurality of data elements, where the servo element and each of the plurality of data elements can detect a servo signal, wherein the method includes moving a sequential information storage medium having a servo band encoded therein across the head module and detecting the servo band using the at least one servo element or any one of the plurality of data elements.

Abstract: A weighted combining scheme exploits information from two servo channels operating in parallel. A timing-based servo module comprises two synchronous servo channels coupled respectively to receive two digital servo signals read from a data tape. Both channels have outputs for an unweighted parameter estimate and for a measure of the channel reliability. A weight computation module provides first and second weight signals using the measures of channel reliability from the servo channels. An offset computation module provides first and second offset terms which are summed with the unweighted parameter estimates. Multiplying nodes receive the unweighted parameter estimates and the weight signals and outputs offset weighted parameter estimates. A summing node receives the offset weighted parameter estimates and outputs a combined offset weighted parameter estimate to a servomechanism.

Abstract: A method for monitoring a plurality of servo channels, providing a finite state machine (“FSM”) comprising a single servo channel mode and a combined servo channel mode, and moving a sequential information storage medium comprising a plurality of servo bands across a read/write head comprising a corresponding plurality of servo sensors. The method further asserts an acquisition flag by a servo channel if that servo channel is tracking a servo pattern, and asserts a bit flag by a servo channel if a new LPOS bit is decoded. If at least one acquisition flag is asserted, the method determines if a bit flag is asserted by a servo channel associated with said asserted acquisition flag, and if an acquisition flag and a bit flag are asserted by a servo channel, the method determines a relative positioning of each servo sensor with respect to an associated servo pattern.

Abstract: A servo write head is provided and is configured to simultaneously write at least two servo patterns in respective servo bands on linear magnetic tape. Centerlines of the servo patterns are substantially uniformly spaced in the lateral direction. In addition, the servo patterns of all adjacent respective servo bands are displaced relative to each other in a longitudinal direction by an amount that is related to a length of a servo frame and a type of the servo patterns.

Abstract: A weighted combining scheme exploits information from two servo channels operating in parallel. A timing-based servo module comprises two synchronous servo channels coupled respectively to receive two digital servo signals read from a data tape. Both channels have outputs for an unweighted parameter estimate and for a measure of the channel reliability. A weight computation module provides first and second weight signals using the measures of channel reliability from the servo channels. An offset computation module provides first and second offset terms which are summed with the unweighted parameter estimates. Multiplying nodes receive the unweighted parameter estimates and the weight signals and outputs offset weighted parameter estimates. A summing node receives the offset weighted parameter estimates and outputs a combined offset weighted parameter estimate to a servomechanism.