Thermal asperity compensating method, data reproduction error compensating method, automatic gain control system and magnetic disk unit
AssigneeNEC Corporation
InventorTakashi Tachikawa
Life of this patent
Estimating the term…
Abstract
A magnetic disk unit lowers a possibility to cause data reproduction errors by setting a gain of a variable gain amplifier (VGA) at a predetermined fixed level for a predetermined time when an output from the VGA which amplifies an input signal is changed to a value smaller than an optimum value upon occurrence of a thermal asperity and then restoring a variable gain condition so that an output amplitude automatically has a certain preset value.
Claims8
An automatic gain control system having
- a variable gain amplifier (hereinafter referred to as a VGA) which receives a read signal as an input and normally outputs a constant amplitude by feeding back an output thereof comprising:
- a gain determination circuit which holds a gain of said variable gain amplifier at a fixed level for a predetermined time duration with a predetermined delay time after detecting a thermal asperity (hereinafter referred to as a TA) from said read signal;
- means for selecting said fixed level from a plurality of fixed levels to be higher than a gain which is immediately before occurrence of the TA.
An automatic gain control system having
- a variable gain amplifier (hereinafter referred to as a VGA) which receives a read signal as an input and normally outputs a constant amplitude by feeding back an output thereof comprising:
- a gain determination circuit which holds a gain of said variable gain amplifier at a fixed level for a predetermined time duration with a predetermined delay time after detecting a thermal asperity (hereinafter referred to as a TA) from said read signal;
- and
- means for providing plurality of values to said gain determination circuit, said gain determination circuit further including means for selecting from said plurality of values as said fixed level wherein said fixed level is higher than a gain of said variable gain amplifier immediately before occurrence of the TA.
A magnetic disk unit comprising an automatic gain amplification system including
- a variable gain amplifier (hereinafter referred to as a VGA) which receives a read signal as an input and normally outputs a constant amplitude by feeding back an output thereof, said variable gain amplifier including:
- a gain determination circuit which holds a gain of said variable gain amplifier at a fixed level for a predetermined time duration with a predetermined delay time after detecting a thermal asperity (hereinafter referred to as a TA) from said read signal;
- and
- means for selecting said fixed level from a plurality of fixed levels to be higher than a gain immediately before occurrence of the TA.
A magnetic disk unit comprising an automatic gain amplification system including
- a variable gain amplifier (hereinafter referred to as a VGA) which receives a read signal as an input and normally outputs a constant amplitude by feeding back an output thereof comprising:
- a gain determination circuit which holds a gain of said variable gain amplifier at a fixed level for a predetermined time duration with a predetermined delay time after detecting a thermal asperity (hereinafter referred to as a TA) from said read signal;
- and
- means for providing a plurality of values to said gain determination circuit, said gain determination circuit further comprising means for selecting from said plurality of values as said fixed level
- wherein said fixed level is higher than a gain of said variable gain amplifier immediately before occurrence of the TA.
Dependencies are inferred from the claim text.