Douglas C. Hansen
Engineers at Hollyberry Ln, Boulder, CO

6366422, Apr 2, 2002

Apr 1, 1999

09/283170

David B. Daniel - Longmont CO
Fred Eifert - Eaton CO
Douglas Christian Hansen - Boulder CO
David Lawson - Arvada CO
Thai Nguyen - Thornton CO

Storage Technology Corporation - Louisville CO

G11B 500

360 76

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.

6798841, Sep 28, 2004

Dec 20, 2000

09/742854

Douglas C. Hansen - Boulder CO

Storage Technology Corporation - Louisville CO

H04L 100

375265, 375341, 714792

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.

6476990, Nov 5, 2002

Jan 4, 2000

09/477229

Douglas Christian Hansen - Boulder CO

Storage Technology Corporation - Louisville CO

G11B 509

360 32, 360 51, 360 46, 375354, 341155

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.

6795511, Sep 21, 2004

Sep 27, 2000

09/671546

Douglas Christian Hansen - Boulder CO

Storage Technology Corporation - Louisville CO

H04L 2706

375341, 375265, 375262

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.

6574059, Jun 3, 2003

Oct 8, 2002

10/266306

Douglas Christian Hansen - Boulder CO

Storage Technology Corporation - Louisville CO

G11B 509

360 32, 360 51, 360 46, 375354, 341155

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.

5566032, Oct 15, 1996

Jul 20, 1995

8/504540

Brian G. Cleveland - Boulder CO
William C. Dodt - Broomfield CO
Douglas C. Hansen - Boulder CO

Storage Technology Corporation - Louisville CO

G11B 1518

360 722

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.

5969898, Oct 19, 1999

Oct 1, 1997

8/942040

Douglas C. Hansen - Boulder CO
Frederick A. McLean - Boulder CO

Storage Technology Corporation - Louisville CO

G11B 2102

360 7716

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.