# US 8,149,954 B2 · Baseline wander compensation for perpendicular recording

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- Number: US 8,149,954 B2
- Document ID: US8149954B2
- Status: Granted
- Kind: B2
- Application number: 12/902,976
- Filed: 2010-10-12
- Published: 2011-04-07
- Granted: 2012-04-03
- Earliest claimed: 2007-02-16
- Assignees: Link—A—Media Devices Corporation
- Inventors: Marcus Marrow; Shih-Ming Shih
- Web page: https://patentgrep.com/patent/US8149954B2

## CPC

- H04L 25/06: DC level restoring means; Bias distortion correction {; Decision circuits providing symbol by symbol detection}
- G11B 20/10046: {filtering or equalising, e.g. setting the tap weights of an FIR filter}
- G11B 20/10203: {baseline correction (DC correction by choosing codewords of the modulation code G11B20/1426)}
- G11B 20/10296: {using the Viterbi algorithm}
- G11B 2220/2512: Floppy disks
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- 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 tail estimate signal which includes noise associated with baseline wander is generated. The tail estimate signal is generated by processing an input signal using a detector to obtain one or more decisions. Using the one or more decisions, the tail estimate signal is generated. The tail estimate signal is removed from the input signal.

## Claims

### Claim 1

A method, comprising:
using a processor to generate a tail estimate signal which includes noise associated with baseline wander, including by:
processing an input signal using a detector to obtain one or more decisions; and
generating the tail estimate signal using the one or more decisions;
removing the tail estimate signal from the input signal; and
using a second detector to process the input signal with the tail estimate signal removed, wherein the detector used to obtain the one or more decisions has a faster latency than the second detector.

### Claim 2 (depends on 1)

The method of claim 1, wherein the input signal includes equalized samples output by a finite impulse response (FIR).

### Claim 3 (depends on 1)

The method of claim 1, wherein the detector used to obtain the one or more decisions includes a decision feedback equalizer (DFE) having one or more delay element parameters, Ti.

### Claim 4 (depends on 1)

The method of claim 1, wherein processing an input signal using the detector to obtain the one or more decisions includes:
removing the tail estimate signal from the input signal; and
processing the input signal with the tail estimate signal removed using the detector.

### Claim 5

A method, comprising:
using a processor to generate a tail estimate signal which includes noise associated with baseline wander, including by:
processing an input signal using a detector to obtain one or more decisions; and
generating the tail estimate signal using the one or more decisions, including by using the equation yi=βxi+αyi-1 where x are input samples and y are output samples; and
removing the tail estimate signal from the input signal.

### Claim 6

A method, comprising:
using a processor to generate a tail estimate signal which includes noise associated with baseline wander, including by:
processing an input signal using a detector to obtain one or more decisions, wherein the detector used to obtain the one or more decisions includes a decision feedback equalizer (DFE) having one or more delay element parameters, Ti; and
generating the tail estimate signal using the one or more decisions, including by using the equation yi=βxi+αyi-1 where xi are input samples and yi are output samples and β and α are parameters;
removing the tail estimate signal from the input signal; and
simultaneously determining values for at least the parameter β and the one or more delay element parameters, Ti.

### Claim 7

A system, comprising:
a tail estimator configured to generate a tail estimate signal which includes noise associated with baseline wander, including by:
processing an input signal using a detector to obtain one or more decisions; and
generating the tail estimate signal using the one or more decisions;
a tail remover configured to remove the tail estimate signal from the input signal; and
a second detector configured to process the input signal with the tail estimate signal removed, wherein the detector used to obtain the one or more decisions has a faster latency than the second detector.

### Claim 8

A system, comprising:
a tail estimator configured to generate a tail estimate signal which includes noise associated with baseline wander, including by:
processing an input signal using a detector to obtain one or more decisions; and
generating the tail estimate signal using the one or more decisions, including by using the equation yi=βxi+αyi-1 where x are input samples and y are output samples; and
a tail remover configured to remove the tail estimate signal from the input signal.

### Claim 9 (depends on 8)

The system of claim 8, wherein the input signal includes equalized samples output by a finite impulse response (FIR).

### Claim 10 (depends on 8)

The system of claim 8, wherein the detector used to obtain the one or more decisions includes a decision feedback equalizer (DFE) having one or more delay element parameters, Ti.

### Claim 11 (depends on 8)

The system of claim 8, wherein the tail estimator is configured to process the input signal using the detector to obtain the one or more decisions by:
removing the tail estimate signal from the input signal; and
processing the input signal with the tail estimate signal removed using the detector.

### Claim 12

A system, comprising:
a tail estimator configured to generate a tail estimate signal which includes noise associated with baseline wander, including by:
processing an input signal using a detector to obtain one or more decisions; and
generating the tail estimate signal using the one or more decisions, including by using the equation yiβxi+αyi-1 where xi are input samples and yi are output samples and β and α are parameters;
a tail remover configured to remove the tail estimate signal from the input signal; and
a processor configured to simultaneously determine values for at least the parameter β and the one or more delay element parameters, Ti.

### Claim 13

A computer program product, the computer program product being embodied in a non-transitory computer readable storage medium and comprising computer instructions for:
generating a tail estimate signal which includes noise associated with baseline wander, including by:
processing an input signal using a detector to obtain one or more decisions; and
generating the tail estimate signal using the one or more decisions;
removing the tail estimate signal from the input signal; and
using a second detector to process the input signal with the tail estimate signal removed, wherein the detector used to obtain the one or more decisions has a faster latency than the second detector.

### Claim 14

A computer program product, the computer program product being embodied in a non-transitory computer readable storage medium and comprising computer instructions for:
generating a tail estimate signal which includes noise associated with baseline wander, including by:
processing an input signal using a detector to obtain one or more decisions; and
generating the tail estimate signal using the one or more decisions, including by using the equation yi=βxi+αyi-1 where x are input samples and y are output samples; and
removing the tail estimate signal from the input signal.

### Claim 15

A computer program product, the computer program product being embodied in a non-transitory computer readable storage medium and comprising computer instructions for:
generating a tail estimate signal which includes noise associated with baseline wander, including by:
processing an input signal using a detector to obtain one or more decisions; and
generating the tail estimate signal using the one or more decisions, including by using the equation yi=βxi+αyi-1 where xi are input samples and yi are output samples and β and α are parameters;
removing the tail estimate signal from the input signal; and
simultaneously determining values for at least the parameter β and the one or more delay element parameters, Ti.

### Claim 16 (depends on 15)

The computer program product of claim 15, wherein the input signal includes equalized samples output by a finite impulse response (FIR).

### Claim 17 (depends on 15)

The computer program product of claim 15, wherein the detector used to obtain the one or more decisions includes a decision feedback equalizer (DFE) having one or more delay element parameters, Ti.

### Claim 18 (depends on 15)

The computer program product of claim 15, wherein the computer instructions for processing an input signal using the detector to obtain the one or more decisions includes computer instructions for:
removing the tail estimate signal from the input signal; and
processing the input signal with the tail estimate signal removed using the detector.