Ampex Corporation

Kurt F Hallamasek

George R Varian

Keith A Kambies

John Abedor

A digital servo track pattern for a magnetic medium which can be recorded and reproduced by a recording and reproducing system. The servo track pattern has a plurality of digital mark patterns recorded thereon, each of said digital mark patterns having a leading identifier field of digital bits, a trailing identifier field of digital bits and a field of digital synchronizing data located between said leading and trailing identifier fields. The leading identifier field of digital bits is electrically equivalent during reproducing while the medium is moving in a first direction to the trailing identifier field of digital bits while the medium is moving in a direction opposite to said first direction.

Digital servo track format with leading and trailing identifiers

A tape system that uses a Kalman filter to produce both an estimate of the tape pack radius and an estimate of the associated estimation error variance. The Kalman filter produces the estimates based on current and prior angular estimation position measurements of the reel, capstan, and tension arm, and the prior estimates of both the tape pack radius and the estimation error variance. The filter gain is based on prior estimation error variance and a calculated measurement error variance, which is a function of the current and prior measurements. Preferably, the system uses two Kalman filters, one to produce the estimates for the supply reel and one to produce the estimates for the take-up reel.

System for estimating tape pack radius using a Kalman filter

Servomechanisms (58 and 60) control a takeup reel (12) and a tension arm (16) in a cassette recorder. The servomechanisms receive control signals (54 and 56) generated in accordance with respective control functions, each of which includes a respective constituent function of the difference between a commanded tension-arm position and a measured tension-arm position. In a position of the tension arm that prevails at the beginning of tape threading the constituent of the tension-arm control function that depends on this arm-position error is a relatively large contribution and gradually decreases to zero as the tension arm moves to the position that it assumes for normal recording and playback. During the same time, the the constituent of the reel-control function that depends on arm-position error begins at zero and gradually increases. Such a gradual transfer of position-error-based control suppresses tape-tension transients that would otherwise result.

Hybrid arm-position/tape-tension servocontrol system

A servomechanism for controlling the position of a magnetic-tape playback head (16) with respect to a track (24) of digital data on a magnetic tape (22) positions the head by reference to an error signal that error-signal-generation circuitry (FIG. 10). generates. Sample-clock signals obtained from simultaneously read azimuth-recorded data tracks clock respective frequency dividers (52 and 54), and a phase detector 56 generates the error signal by comparing the frequency dividers' outputs.

Track-curvature detection using clock phase shift in azimuth recording

A timing recovery system for the low density longitudinal record channels utilizing capstan velocity or feed forward rate in a magnetic tape recording/reproducing system in which the capstan feed forward velocity, derived from an encoder, provides a signal whose frequency is proportional to the speed of the tape driven by the capstan. A scaling circuit is provided by a frequency-to-voltage converter followed by a voltage-to-frequency converter, the output signal providing a demodulation clock having a multiplied frequency proportional to the data rate reproduced from the tape. The demodulation clock, fed to the timing window generation circuitry, provides an input to data detection circuitry to provide a clocked data output, regardless of the reproduce speed within a very large range of speeds.

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Berkeley, CA, United States of America

Kurt F Hallamasek