Digital servo demodulation for sampled amplitude magnetic recording
First Claim
1. 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) a means for receiving the discrete time sample values;
(b) a rectifier for generating a rectified sequence of sample values proportional to the absolute magnitude of the discrete time sample values of the analog signal;
(c) an accumulator for accumulating a predetermined number of the rectified sample values representative of one of the plurality of servo bursts; and
(d) a discrete time output for outputting a discrete time servo control signal indicative of an area of the pulses representing a servo burst.
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Abstract
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.
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Citations
29 Claims
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1. 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:
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(a) a means for receiving the discrete time sample values; (b) a rectifier for generating a rectified sequence of sample values proportional to the absolute magnitude of the discrete time sample values of the analog signal; (c) an accumulator for accumulating a predetermined number of the rectified sample values representative of one of the plurality of servo bursts; and (d) a discrete time output for outputting a discrete time servo control signal indicative of an area of the pulses representing a servo burst. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. 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:
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(a) sampling the analog read signal to generate the discrete time sample values; (b) generating a rectified sequence of sample values proportional to an absolute magnitude of the discrete time samples of the analog read signal; (c) accumulating a predetermined number of the rectified sample values representative of one of the plurality of servo bursts; and (d) outputting a discrete time servo control signal indicative of an area of the pulses representing a servo burst. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. 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:
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(a) an input for receiving the discrete time sample values; (b) an accumulator for accumulating a predetermined number of the sample values representative of one of the plurality of servo bursts; and (c) a discrete time output for outputting a discrete time servo control signal indicative of an area of the pulses representing a servo burst. - View Dependent Claims (20)
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21. 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:
- the servo data comprises a plurality of servo bursts and each servo burst comprises a plurality of pulses, the servo bursts are used to control an electromechanical servo system for positioning a recording head with respect to the disk storage medium, and the user data is recorded at a predetermined baud rate, the sampled amplitude read channel comprising;
(a) a sampling device for sampling the analog read signal asynchronous to the baud rate to generate asynchronous sample values representing the servo bursts; (c) an accumulator for accumulating a predetermined number of the asynchronous sample values representing one of the servo bursts; and (d) a discrete time output for outputting a discrete time servo control signal indicative of an area of the pulses representing the servo burst. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29)
- the servo data comprises a plurality of servo bursts and each servo burst comprises a plurality of pulses, the servo bursts are used to control an electromechanical servo system for positioning a recording head with respect to the disk storage medium, and the user data is recorded at a predetermined baud rate, the sampled amplitude read channel comprising;
Specification