Synchronous servo channel for tape drive systems

A synchronous servo channel for a data tape drive, comprising:

• a servo reader configured to read servo bursts from a data tape movable longitudinally past the servo reader at a tape velocity, the tape further having a lateral (y) position relative to the servo reader and a longitudinal position (LPOS) relative to an end of the tape;
• a clock operable at a fixed-frequency;
• an analog-to-digital converter (ADC) operable to output signal samples at a sampling rate provided by the clock and coupled to receive a servo channel signal comprising servo bursts from the servo reader, the servo bursts including encoded LPOS symbols embedded therein;
• a channel parameter acquisition module operating at a rate established by the clock, comprising:
• a first input coupled to receive a sequence of signal samples from the ADC;
• a second input coupled to receive at least one control signal from the channel parameter estimator;
• and
• a plurality of outputs for outputting at least an initial tape velocity estimate and an initial y-position estimate;
• a timing-basis generator initially responsive to at least the initial tape velocity estimate and initial y-position estimate from the parameter acquisition module, the timing-basis generator comprising a control unit and operable to output a plurality of control signals and a timing error signal;
• a servo channel signal interpolator operating at a rate established by the clock, comprising:
• a first input coupled to receive the sequence of signal samples from the ADC;
• and
• a second input coupled to receive the timing information from the timing-basis generator for the generation of interpolated servo signal samples;
• a channel parameter estimator initially responsive to at least the initial tape velocity estimate and initial y-position estimate from the parameter acquisition module, the parameter estimator comprising:
• a first input coupled to receive the sequence of signal samples from the ADC;
• and
• a second input coupled to receive at least one of the signals output from the timing-basis generator;
• and
• a first output to provide a tape velocity estimate and a second output to provide a y-position estimate from the sequence of signal samples output from the channel ADC;
• an optimum longitudinal position (LPOS) detector, comprising:
• a first input coupled to receive an output from the servo channel signal interpolator;
• a second input coupled to receive at least one of the plurality of signals output from the timing-basis generator;
• and
• an output to provide a decoded LPOS symbol;
• and
• an LPOS detection monitor operable to assign a reliability measure to the decoded LPOS symbol.

A computer program product of a computer readable medium usable with a programmable computer, the computer program product having computer-readable code embodied therein for operating a synchronous servo channel in a data tape drive in which a loaded tape has a velocity, a lateral (y) position relative to a servo element and a longitudinal position (LPOS) relative to an end of the tape, the computer-readable code comprising instructions for:

• acquiring initial servo channel parameters from a sequence of signal samples output from a channel analog to digital converter (ADC) without a prior indication of the tape velocity or of the y-position of the tape;
• generating a timing basis for signal interpolation from zero crossings of an interpolated servo channel signal, whereby timing information is extracted despite unequally spaced servo bursts in the servo channel signal;
• generating a tape velocity estimate and a y-position estimate from the sequence of signal samples output from the channel ADC;
• detecting and decoding an LPOS symbol encoded in the servo bursts;
• and
• monitoring LPOS detection and assigning a reliability measure to the decoded LPOS symbol.