# US 8,570,679 B2 · Read channel averaging

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- Number: US 8,570,679 B2
- Document ID: US8570679B2
- Status: Granted
- Kind: B2
- Application number: 11/709,719
- Filed: 2007-02-21
- Published: 2008-08-21
- Granted: 2013-10-29
- Earliest claimed: 2007-02-21
- Assignees: Seagate Technology International
- Applicants: Yunxiang Wu; Henry Bang; Richard Wang
- Inventors: Yunxiang Wu; Henry Bang; Richard Wang
- Web page: https://patentgrep.com/patent/US8570679B2

## CPC

- G11B 20/10027: {adjusting the signal strength during recording or reproduction, e.g. variable gain amplifiers (optimum power control for optical discs G11B7/125)}
- G11B 20/10009: {Improvement or modification of read or write signals}
- G11B 20/10046: {filtering or equalising, e.g. setting the tap weights of an FIR filter}
- G11B 20/10055: {using partial response filtering when writing the signal to the medium or reading it therefrom}
- G11B 20/10194: {using predistortion during writing (G11B20/10055 takes precedence)}
- G11B 20/10296: {using the Viterbi algorithm}
- G11B 20/24: for reducing noise {(control of amplification in general, e.g. dependent upon noise level H03G)}
- G11B 2020/1863: {wherein the Viterbi algorithm is used for decoding the error correcting code}
- G11B 2220/2516: Hard disks
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

A hard disk drive with a read channel that averages data before the data is provided to a viterbi detector of the channel. Averaging the data reduces the zero mean noise in the data.

## Claims

### Claim 1

An apparatus, comprising:
a read channel coupled to a head, wherein
said read channel includes a detector,
said read channel includes an averaging circuit having a buffer and averaging logic,
said read channel includes a finite impulse filter directly coupled to said averaging circuit,
said buffer is operable to store read data, wherein said read data comprises a same data being read using said head multiple times at different times,
said averaging logic is operable to average said read data,
said averaging circuit is directly coupled to said detector in an open-ended arrangement operable to provide an average of said data to said detector, and
said detector provides a maximum likelihood detection of said averaged data;
an actuator arm coupled to said head; and
a controller coupled to said read channel.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein said averaging circuit reduces a zero mean noise of said data.

### Claim 3 (depends on 1)

The apparatus of claim 1, wherein said averaging circuit produces an average of data read from a disk sector at different times.