Storage Technology Corporation

Mks Instruments, Inc.

Douglas Christian Hansen

Gerardo A Brucker

William C Dodt

Thai Nguyen

Paul C Arnold

Brian G Cleveland

Stephen C Blouch

Fred C Eifert

David B Daniel

David A Lawson

Wesley J Graba

Frederick A McLean

Devices and corresponding methods can be provided to test an ionization gauge, such as a hot cathode ionization gauge, for leakage currents and to respond to the leakage currents to improve pressure measurement accuracy. Responding to the leakage current can include applying a correction to a pressure measurement signal generated by the gauge based on the leakage current. Responding to the leakage current can also include removing contamination causing the leakage current, where the contamination is on electrical feedthrough insulators or other gauge surfaces. Testing and correcting for leakage currents and removing contamination can be completed with the ionization pressure gauge in situ in its environment of use, and while the gauge remains under vacuum.

Devices and methods for feedthrough leakage current detection and decontamination in ionization gauges

Devices and corresponding methods are provided to operate a hot cathode ionization pressure gauge (HCIG). A transistor circuit can be configured to pass the electron emission current with low input impedance and to control cathode bias voltage. Emission current and cathode bias voltage can be controlled independently of each other, without a servo settling time. HCIGs can be calibrated with respect to leakage current.

Ionization pressure gauge with bias voltage and emission current control and measurement

A wide dynamic range trans-impedance amplifier includes a first trans-impedance amplifier configured to receive a first input current and produce a first voltage as a function of the first input current, and a second trans-impedance amplifier configured to receive a second input current and produce a second voltage as a function of the second input current. A current steering element causes a first portion of current from a current source to flow to the first trans-impedance amplifier until the first current portion reaches the first threshold current, and causes a second portion of current from the current source to flow to the second trans-impedance amplifier, until the second current portion reaches the second threshold current. The second current portion is current from the current source that exceeds the first threshold current. The wide dynamic range trans-impedance amplifier may receive, for example, ion collector current from a hot cathode ionization gauge (HCIG).

Trans-impedance amplifier with increased dynamic range

An adaptive trellis adaptable to read a signal having signal amplitude dropouts includes a standard partial response maximum likelihood (PRML) trellis and an estimating PRML trellisd. The standard trellis is associated with a standard state diagram having standard branches between states. The estimating trellis is associated with an estimating state diagram having estimating branches between states. Each branch has an associated error metric. Each state of the standard state diagram has two estimating branches feeding into that state and each state of the estimating state diagram has two standard branches feeding into that state. The states are connected by paths formed by branches between the states. A path error metric is the sum of all branch error metrics for all of the branches that form the path. The path arriving at one state having the lowest error metric is the expected path to the next state for reading the signal.

Partial response maximum likelihood (PRML) detection trellis method adaptable to signal dropouts

An improved maximum likelihood detector with a trellis having three or more dimensions is disclosed. Trellis dimensions include a state dimension and a sample dimension found in a conventional Viterbi trellis. The additional dimensions are added to the trellis for adaptation to additional parameters that are responsive to channel variations such as pulse shape, amplitude, timing, media velocity and media tension. A set of rules govern most likely paths moving along the additional dimensions. In the preferred embodiment, a most likely path may transition up to a predetermined maximum number of unit lengths along each additional dimension per unit length movement in the sample dimension. Once a path has changed values in any given additional dimension then it must dwell at that value for a minimum number of samples.

Method for reducing the sensitivity of a maximum likelihood detection trellis to channel variations

A circuit and a method of operation for detecting a bit sequence from an analog waveform representing the bit sequence and at least one other parameter associated with the analog waveform are disclosed. Detection includes digitizing the analog waveform and at least one other parameter using at least one analog to digital converter. The resulting digital numbers are synchronized in time by a plurality of registers so that the outputs of the registers always change simultaneously. The outputs of the registers are concatenated to form an address. The address is input into a read-only memory that looks up a most likely bit detected that has been predetermined for that address and stored in the read-only memory. The bits read from the read-only memory by the addresses are output periodically to form the bit sequence.

General purpose digital read channel architecture

It is difficult to read data from curved helical data tracks in a helical scan tape drive. Curved helical tracks can be caused by improper tape tension, tape damage, tape path misalignment, tape head offset between different head systems, and debris. The present invention solves the problem of recovering data from curved helical tracks by providing a table of different curve offset signals. Each curve offset signal represents a curve track profile of a typical curved track. The position of the helical read head reading a curved data track is controlled as a function of one of the curve offset signals such that the read head is positioned properly with respect to the helical data track to provide a proper read back signal. The curve offset signals are selected one at a time to control the position of the helical read head until the helical read head provides a proper read back signal.

Helical scan tape drive error recovery using track profile mapping

A method and system for reading data containing errors due to curved or displaced tracks in a track region reproduced by reproducing heads in a tape drive includes a signal processing circuit for sensing a first set of parameters associated with the data at a first head position at predetermined points along each track in the region. The signal processing circuit also senses a second set of parameters associated with the data at a second head position different from the first head position at the predetermined points along each track in the region. A movable head controller positions the reproducing heads to follow the curved or displaced tracks based on the first and second head positions and the first and second set of parameters.

Method and system for reading data that is unreadable by a tape drive

A novel method is disclosed for performing a high speed search for a selected data block or data file utilizing any one of several presently existing helical scan tape formats which utilize, in addition to the helically scanned tracks, one or more longitudinal tracks for recording indexing information indicative of the location of data blocks and file marks stored on the associated helical tracks. Data file location information is written to a header area on a series of helical tracks and to one (or more) of the longitudinal tracks when a data block or a file mark is written to a tape. A high speed search for a desired data block or data file can then be performed using this track location information.

Growing community of inventors

Boulder, CO, United States of America

Douglas Christian Hansen