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US 5,327,302 AGranted
Data filter tuning for constant density recording applications
AssigneeAT&T Bell Laboratories
InventorsJohn M. Khoury, Dale H. Nelson
Life of this patent
Estimating the term…
Abstract
An arrangement for tuning a data filter in a mass storage system. The filter cutoff frequency (low pass) may be set as a percentage above or below the incoming data rate to achieve the desired "eye opening" in read data. The frequency of a reference oscillator in a phase-locked-loop (PLL) and the cutoff frequency of the filter is controlled by a common control signal from the PLL. The PLL, locked to a scaled multiple of the data rate, determines the cutoff frequency of the filter.
Claims11
In a mass storage system having:
- a tunable filter for filtering data read from the system, the filter having a characteristic frequency substantially determined by a control signal;
- and
- a generator for producing a reference signal having a frequency substantially proportional to the frequency of the data;
- Characterized by:
- a comparison network, responsive to the reference signal, for providing a control signal;
- and
- a reference network, responsive to the control Signal, for providing an output signal coupled to the comparison network;
- wherein the comparison network phase locks the output signal from the reference network to the frequency of the reference signal scaled by a predetermined scale factor Y/X and the characteristic frequency of the tunable filter is substantially proportional to the scaled frequency of the reference signal.
5 more elements
In a magnetic medium mass storage system read channel having:
- a tunable filter for filtering data read from the medium, the filter having a characteristic frequency substantially determined by a control signal;
- and
- a generator for producing a reference signal having a frequency substantially proportional to the frequency of the read data;
- Characterized by:
- an oscillator, for providing an output signal, the frequency of which is substantially determined by the control signal and is proportional to the characteristic frequency of the tunable filter;
- a first divider for dividing the frequency of the reference signal by a predetermined factor X;
- a second divider for dividing the frequency of the output signal from the reference network by a predetermined factor Y;
- a phase comparator, having an output, for comparing the phases of the divided reference signal and the divided output signal from the reference network;
- and
- a filter, coupling to the output of the phase comparator, for providing the control signal to the tunable filter and the oscillator;
- wherein the characteristic frequency of the tunable filter substantially proportional to the frequency of the reference signal scaled by the factor Y/X.
8 more elements
Dependencies are inferred from the claim text.