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Synchronous servo channel for longitudinal position detection and position error signal generation in tape drive systems

a technology of synchronous servo channels and longitudinal positions, applied in the direction of maintaining head carrier alignment, digital recording, instruments, etc., can solve the problems of insufficient resolution, inability to measure the reliability of the lpos detection process, and inability to detect lpos reliably during acceleration and deceleration, so as to improve the reliability of servo channels

Inactive Publication Date: 2007-07-26
INT BUSINESS MASCH CORP
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  • Summary
  • Abstract
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  • Application Information

AI Technical Summary

Benefits of technology

[0011] The present invention provides a fully synchronous longitudinal position (LPOS) detection system for improving the reliability of servo channels in tape systems. The present invention is based on the interpolation of the servo channel output signal, which is sampled by an analog-to-digital converter (ADC) at a fixed sampling rate, using a clock at a nominal frequency, so that interpolated signal samples are obtained at a predetermined fixed rate, independent of tape velocity. This predetermined fixed rate is defined in terms of samples per unit of length, as opposed to samples per unit of time, which is the measure of the ADC sampling rate. The resolution with which the servo channel signal is obtained at the interpolator output is thus determined by the step interpolation distance.

Problems solved by technology

This approach has the following severe limitations: a) The A / D converter sampling frequency has to change with the tape velocity if a constant rate expressed in number of samples per micrometer that is independent of tape velocity is desired.
c) No reliable LPOS detection is possible during acceleration and deceleration, i.e., during the phase at which the velocity is changing towards the target velocity.
d) Peak detection is not the optimum detection scheme for the LPOS pattern, which is generated using pulse position modulation (PPM) techniques.
f) There is no possibility to have a measure of reliability of the LPOS detection process.
Clearly, such a resolution is not adequate when one wants to resolve LPOS pulse position modulation of + / −0.25 μm.

Method used

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  • Synchronous servo channel for longitudinal position detection and position error signal generation in tape drive systems
  • Synchronous servo channel for longitudinal position detection and position error signal generation in tape drive systems
  • Synchronous servo channel for longitudinal position detection and position error signal generation in tape drive systems

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Synchronous Servo Channel Architecture

[0040] With the architecture of the present invention, the dynamic interpolator allows any sampling rate at the detector input, with the only limitation arising because of potential aliasing effects. For example, in the case of a distance between magnetic transitions given by Lp=2.1 μm, the maximum velocity achievable without aliasing effects with a 15 MHz fixed ADC clock is νmax=2.1×(15 / 2)=15.75 m / s. In this case the equivalent sampling frequency after the burst interpolator for achieving a resolution of 0.05 μm is equal to 315 MHz. Note that this would be the required fixed sampling frequency in an asynchronous architecture.

[0041]FIG. 3 illustrates the basic building blocks of the synchronous LPOS detection architecture 400 of the present invention. Because the number of samples per unit of length is fixed and independent of velocity after the burst interpolator, a matched filter approach can be employed for optimum detection of PPM in the ...

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Abstract

A fully synchronous longitudinal position (LPOS) detection system is provided for improving the reliability of servo channels in tape systems. The system is based on the interpolation of the servo channel output signal, which is sampled by an analog-to-digital converter (ADC) at a fixed sampling rate, using a clock at a nominal frequency, so that interpolated signal samples are obtained at a predetermined fixed rate, independent of tape velocity. This predetermined fixed rate is defined in terms of samples per unit of length, as opposed to samples per unit of time, which is the measure of the ADC sampling rate. The resolution with which the servo channel signal is obtained at the interpolator output is thus determined by the step interpolation distance.

Description

TECHNICAL FIELD [0001] The present invention relates generally to servo channel architecture in a magnetic tape storage system and, in particular, to a synchronous servo channel architecture. BACKGROUND ART [0002] Timing-based servo (TBS) is a technology developed specifically for linear tape drives in the late '90s. In TBS systems, recorded servo patterns consist of transitions with two different azimuthal slopes, and head position is derived from the relative timing of pulses generated by a narrow head reading the pattern. TBS patterns also allow the encoding of additional longitudinal position (LPOS) information without affecting the generation of the transversal position error signal (PES). This is obtained by shifting transitions from their nominal pattern position, as shown in FIG. 1. In tape systems there are typically available two dedicated servo channels from which LPOS information as well as PES can be derived. The timing-based track-following servo for linear tape system...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G11B5/584G11B5/09
CPCG11B5/584G11B5/58G11B5/09
Inventor CHERUBINI, GIOVANNIELEFTHERIOU, EVANGELOS S.HUTCHINS, ROBERT A.JELITTO, JENS
Owner INT BUSINESS MASCH CORP
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