US5220466A — Method and apparatus for digital filter control i…

Claim 1

Independent Claim 75 words

A method for controlling a digital filter function included in a data path within gain and timing control loops of a PRML recording channel comprising the steps of: removing the digital filter function from the data path during an acquisition mode; restoring the digital filter function to the data path during a tracking mode; and providing a predetermined gain and a quantized delay at a synchronization frequency when switching from acquisition mode to tracking mode.

Claim 2

Independent Claim 75 words

A method for controlling a digital filter function included in a data path within gain and timing control loops of a PRML recording channel comprising the steps of: removing the digital filter function from the data path during an acquisition mode; restoring the digital filter function to the data path during a tracking mode; and providing a predetermined gain and a quantized delay at a synchronization frequency when switching from acquisition mode to tracking mode.

Claim 3

Dependent Claim 40 words

A method as recited in claim 1 further comprising the step of: supplying a digital signal from an analog to digital converter ADC of the PRML magnetic recording channel to an acquisition gain and timing control during the acquisition mode.

Claim 4

Dependent Claim 52 words

A method as recited in claim 2 further comprising the steps of: supplying a digital signal from the ADC of the PRML recording channel to the digital filter during the acquisition mode, whereby initial conditions start-up of the digital filter is provided with the digital filter function removed from the data path.

Claim 5

Dependent Claim 36 words

A method as recited in claim 1 further comprising the step of: supplying a digital signal from the digital filter of the PRML recording channel to a tracking gain and timing control during the tracking mode.

Claim 6

Dependent Claim 20 words

A method as recited in claim 3 wherein said step of providing a predetermined gain includes providing a unity gain.

Claim 7

Dependent Claim 40 words

A method as recited in claim 1 wherein said step of providing a quantized delay includes providing a delay defined by nT±k, where n is an integer number, T is a sampling period and k is a fractional delay parameter.

Claim 8

Dependent Claim 77 words

Apparatus for controlling a digital filter function included in a data path within gain and timing control loops of a PRML recording channel comprising: means for removing the digital filter function from the data path during an acquisition mode; means for restoring the digital filter function to the data path during a tracking mode; and means for providing a predetermined gain and a quantized delay at a synchronization frequency when switching from acquisition mode to tracking mode.

Claim 9

Dependent Claim 77 words

Apparatus for controlling a digital filter function included in a data path within gain and timing control loops of a PRML recording channel comprising: means for removing the digital filter function from the data path during an acquisition mode; means for restoring the digital filter function to the data path during a tracking mode; and means for providing a predetermined gain and a quantized delay at a synchronization frequency when switching from acquisition mode to tracking mode.

Claim 10

Dependent Claim 119 words

Apparatus as recited in claim 7 wherein said PRML recording channel is a PRML magnetic recording channel including a maximum-likelihood detector; a variable-gain amplifier (VGA); an analog to digital converter (ADC); and the digital filter function being coupled between the ADC and the maximum-likelihood detector; and wherein said means for removing the digital filter function from the data path during an acquisition mode include: an acquisition gain and timing control for receiving an input signal from the ADC; and said acquisition gain and timing control responsive to said received input signal for generating a digital gain control signal for adjusting the gain of the VGA and for generating a digital timing control signal for correcting timing of the ADC.

Claim 11

Dependent Claim 80 words

Apparatus as recited in claim 8 wherein said means for restoring the digital filter function from the data path during a tracking mode include: a tracking gain and timing control for receiving an input signal from the digital filter; and said tracking gain and timing control responsive to said received input signal for generating a digital gain control signal for adjusting the gain of the VGA and for generating a digital timing control signal for correcting timing of the ADC.

Claim 12

Dependent Claim 49 words

Apparatus as recited in claim 9 wherein each said acquisition gain and timing control is adapted for providing a unity gain for the VGA and for providing a delay defined by an integer number of sampling periods at a synchronization frequency when switching from acquisition mode to tracking mode.

Claim 13

Dependent Claim 53 words

Apparatus as recited in claim 7 further including means for supplying a digital signal from an analog to digital converter of the PRML recording channel to the digital filter during an acquisition mode, whereby initial conditions start-up of the digital filter is provided with the digital filter function removed from the data path.

Claim 14

Dependent Claim 154 words

In a direct access storage device (DASD) of the type utilizing partial response signaling and maximum-likelihood (PRML) detection including a digital filtering function comprising: a housing; at least one disk mounted in said housing for rotation about an axis and for providing at least one disk surface for storing data arrayed in a pattern around said axis; transducer means mounted for movement across said disk surface for reading and writing data on said disk surface; and apparatus for controlling a digital filter function included in a data path within gain and timing control loops of the PRML magnetic recording channel including; means for removing the digital filter function from the data path during an acquisition mode; means for restoring the digital filter function to the data path during a tracking mode; and means for providing a predetermined gain and a quantized delay at a synchronization frequency when switching from acquisition mode to tracking mode.

Claim 15

Dependent Claim 154 words

In a direct access storage device (DASD) of the type utilizing partial response signaling and maximum-likelihood (PRML) detection including a digital filtering function comprising: a housing; at least one disk mounted in said housing for rotation about an axis and for providing at least one disk surface for storing data arrayed in a pattern around said axis; transducer means mounted for movement across said disk surface for reading and writing data on said disk surface; and apparatus for controlling a digital filter function included in a data path within gain and timing control loops of the PRML magnetic recording channel including; means for removing the digital filter function from the data path during an acquisition mode; means for restoring the digital filter function to the data path during a tracking mode; and means for providing a predetermined gain and a quantized delay at a synchronization frequency when switching from acquisition mode to tracking mode.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1996-06-14	1996-12-14	1997-06-15	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2000-06-14	2000-12-14	2001-06-15	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2004-06-14	2004-12-14	2005-06-15	$7700.00	Window Closed / Lapsed

Method and apparatus for digital filter control in a partial-response maximum-likelihood disk drive system

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