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US 5,854,714 AGranted
Digital servo demodulation for sampled amplitude magnetic recording
AssigneeCirrus Logic, Inc.
InventorsDavid E. Reed, William G. Bliss
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AssigneeCirrus Logic, Inc.
InventorsDavid E. Reed, William G. Bliss
Estimating the term…
A discrete time servo demodulation technique incorporated within a sampled amplitude read channel to demodulate embedded servo field information stored on a magnetic medium. The servo field information is transduced by a read head into an analog signal, and converted to a sequence of sample values in the read channel. The demodulation technique is responsive to the sample values and includes a discrete time peak detector for detecting servo data, and a discrete time servo burst amplitude detector for measuring the amplitude of servo bursts. Peaks are detected in the analog read signal by sensing a change of slope from the sequence of sample values. The peaks are qualified by polarity in that a peak is detected only if its polarity is opposite in sign from the previous peak. The servo burst amplitudes are measured by interpolating, rectifying, and accumulating the sequence of sample values corresponding to the servo bursts. A plurality of registers store the amplitude measurement of corresponding servo bursts such as the four servo bursts in a quadrature system. The sample values are interpolated, squared, and the sampling frequency dithered in order to decrease the sensitivity of the burst amplitude measurement to variations in the sampling phase and to increase the effective resolution of the read channel ADC for servo demodulation. Control signals are generated in response to the detected servo data which are transferred to a servo controller over a fully digital interface, thus obviating the analog-to-digital converter found in conventional servo controllers.
A discrete time area detector used in a sampled amplitude read channel, responsive to a sequence of discrete time sample values generated by sampling pulses in an analog signal representative of digital data stored on a magnetic medium, the analog signal being generated by reading the medium using a magnetic read/write head, the digital data comprises a plurality of servo bursts wherein each servo burst comprises a plurality of pulses, the servo bursts used to control an electromechanical servo system for positioning the read/write head with respect to the medium, the discrete time area detection circuit comprising:
A method for reading digital data from a sequence of discrete time sample values generated by sampling pulses in an analog read signal emanating from a magnetic read/write head positioned over a magnetic storage medium, the digital data comprising a plurality of servo bursts wherein each servo burst comprises a plurality of pulses, the servo bursts used to control an electromechanical servo system for positioning the read/write head with respect to the medium, comprising the steps of:
A sampled amplitude read channel, responsive to a sequence of discrete time sample values generated by sampling pulses in an analog read signal representative of digital data stored on a magnetic medium, the analog read signal generated by reading the medium using a magnetic read/write head, the digital data comprising a plurality of servo bursts wherein each servo burst comprises a plurality of pulses, the servo bursts used to control an electromechanical servo system for positioning the read/write head with respect to the medium, the sampled amplitude read channel comprising:
A sampled amplitude read channel for detecting user data and servo data stored on a disk storage medium from a sequence of discrete time sample values generated by sampling pulses in an analog read signal, wherein:
Dependencies are inferred from the claim text.