Abstract: In a method of manufacturing a silicon carbide semiconductor device, a semiconductor substrate made of silicon carbide and having first and second opposing surfaces is prepared. The second surface of the semiconductor substrate is processed so that a surface roughness of the second surface is less than or equal to 10 nm and a value of (100%-reflectance-transmittance) at a wavelength of a laser light is greater than or equal to 80%. A metal layer is formed on the second surface of the semiconductor substrate after the processing the second surface. The metal layer is irradiated with the laser light and thereby an ohmic electrode is formed on the second surface.

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: 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: 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: A system and method are disclosed for detecting a periodic sequence. A value detector module detects a plurality of values of a periodic sequence. In one embodiment, a transformation module transforms the plurality of values into transformed values. A confinement module confines the values to a limited set of confined values. A correlation module correlates the confined values with a plurality of instances of the periodic sequence. In addition, a selection module selects an instance of the periodic sequence with the highest correlation to the confined values as an observed periodic sequence.

Abstract: In a magnetic tape drive having a servo read system with at least one read head, the system configured to read servo pattern information as a magnetic tape is moved longitudinally with respect to the at least one read head, the servo pattern comprising a timing-based servo pattern comprising an even number of bursts of sloped magnetic stripes, adjacent bursts oppositely sloped, alternate bursts identically sloped, an embodiment of a method determines the time between detection from the read head of a same stripe of alternate bursts of a pattern; determines the time between detection from the read head of stripes of a burst of a pattern; and determines a ratio of the determined times. The ratio is compared to a threshold, wherein the threshold comprises a differentiation between different servo pattern types.

Abstract: In accordance with the present invention, a method of operating a magnetic tape drive, a magnetic tape drive and a servo control system are provided for obtaining and maintaining velocity control in a magnetic tape drive. In one embodiment, a method is provided for operating a magnetic tape drive. The tape drive includes a plurality of DC motors, and each DC motor has a plurality of Hall sensors. The DC motors are under the control of a servo system which is configured to read location information from the magnetic tape, and compute a primary tape velocity from the location information, and sense a secondary and tertiary velocity signal and compute a tape velocity based on one of the sensed secondary velocity signal and tertiary velocity. The method includes detecting if the primary velocity location information is available. In response to detecting that the primary velocity location information is available the primary velocity is employed to control the servo system.

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: In a manufacturing method of a silicon carbide semiconductor device, a semiconductor substrate made of single crystal silicon carbide is prepared, an amorphous layer is formed on a portion of the semiconductor substrate where an electrode is to be formed, a metal layer is formed on the amorphous layer, and the electrode including the metal layer and a silicide layer is formed by irradiating the metal layer with a laser light in such a manner that a part of the metal layer reacts with the amorphous layer and forms the silicide layer.

Abstract: Where a tape is subject to lateral shift excursions from one side of a head to another, a coarse actuator is positioned laterally to enable a fine actuator to follow lateral motion of a longitudinal tape having at least one longitudinal defined servo track. A position error signal loop is configured to sense servo sensor(s) and to determine position error between the head and a desired position related to the defined servo track(s). A servo control senses the lateral shift excursion of the defined servo track(s); determines a maximum positive peak and a maximum negative peak of the lateral shift excursion; and positions the coarse actuator substantially at a midpoint of the maximum positive peak and the maximum negative peak of lateral shift excursion of the defined servo track(s). Thus, the fine actuator follows the lateral shift excursion, while the coarse actuator remains at the midpoint.

Abstract: In a magnetic tape drive having a servo read system with at least one read head, the system configured to read servo pattern information as a magnetic tape is moved longitudinally with respect to the at least one read head, the servo pattern comprising a timing-based servo pattern comprising an even number of bursts of sloped magnetic stripes, adjacent bursts oppositely sloped, alternate bursts identically sloped, an embodiment of a method determines the time between detection from the read head of a same stripe of alternate bursts of a pattern; determines the time between detection from the read head of stripes of a burst of a pattern; and determines a ratio of the determined times. The ratio is compared to a threshold, wherein the threshold comprises a differentiation between different servo pattern types.

Abstract: A method and apparatus is presented to determine a lateral position of a read/write head relative to a sequential information storage medium having a servo signal encoded therein and moving adjacent to the read/write head, where the servo signal comprises a plurality of pulses. The method includes detecting the servo signal using the read/write head and calculating a timing interval between each of the pulses using a clock rate of a clock signal. The clock rate is then adjusted based upon the velocity of the sequential information storage medium.

Abstract: A servo detection system for detecting servo tracks of a longitudinal tape. In a read/write head, two servo read heads are spaced laterally on a first head module, and a servo read head is on a second head module spaced longitudinally from the first module. A method comprises initially sensing a tape servo track with one servo read head of the first module and the servo read head of the second module to determine skew misalignment of the servo track. A zero reference value is stored representing the determined skew misalignment. The detection system switches from the one servo read head of each module, to the two servo read heads of the first module, and employs the stored value to position the read/write head in the zero skew position. The two servo read heads are then employed to read two servo tracks to identify the data band and to control skew.

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: An apparatus, system, and method are disclosed for dynamic tape stick and tape break detection. A first counter increments a first count and resets a second count in response to a sensor pulse from a first sensor of a first tape servo. A second counter increments the second count and resets the first count in response to a sensor pulse from a second sensor of a second tape servo. A detection module detects either the first count or the second count exceeding an error threshold.

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: Where a tape is subject to lateral shift excursions from one side of a head to another, a coarse actuator is positioned laterally to enable a fine actuator to follow lateral motion of a longitudinal tape having at least one longitudinal defined servo track. A position error signal loop is configured to sense servo sensor(s) and to determine position error between the head and a desired position related to the defined servo track(s). A servo control senses the lateral shift excursion of the defined servo track(s); determines a maximum positive peak and a maximum negative peak of the lateral shift excursion; and positions the coarse actuator substantially at a midpoint of the maximum positive peak and the maximum negative peak of lateral shift excursion of the defined servo track(s). Thus, the fine actuator follows the lateral shift excursion, while the coarse actuator remains at the midpoint.

Abstract: A method, a servo system and a tape drive are provided to acquire lock on a servo signal. The servo signals of at least one servo element are monitored to detect a valid servo signal. If a valid servo signal is not detected than the fine actuator is moved in a first direction until either a valid servo signal is detected or the fine actuator travel limit is reached. When a valid servo signal is detected, the fine actuator is set to a neutral position and the coarse actuator is moved in the first direction. When the fine actuator travel limit is reached the fine actuator is moved to the first position and the coarse actuator is moved in a second direction, opposite of the first direction.

Abstract: A servo detection system for detecting servo tracks of a longitudinal tape. In a read/write head, two servo read heads are spaced laterally on a first head module, and a servo read head is on a second head module spaced longitudinally from the first module. A method comprises initially sensing a tape servo track with one servo read head of the first module and the servo read head of the second module to determine skew misalignment of the servo track. A zero reference value is stored representing the determined skew misalignment. The detection system switches from the one servo read head of each module, to the two servo read heads of the first module, and employs the stored value to position the read/write head in the zero skew position. The two servo read heads are then employed to read two servo tracks to identify the data band and to control skew.

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.