# US 8,786,970 B2 · Determining inter-track coherence using output signals from first and second tracks

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- Number: US 8,786,970 B2
- Document ID: US8786970B2
- Status: Granted
- Kind: B2
- Application number: 13/429,795
- Filed: 2012-03-26
- Published: 2013-09-26
- Granted: 2014-07-22
- Earliest claimed: 2012-03-26
- Assignees: Seagate Technology LLC
- Applicants: Mehmet Fatih Erden
- Inventors: Mehmet Fatih Erden
- Web page: https://patentgrep.com/patent/US8786970B2

## CPC

- G11B 5/012: Recording on, or reproducing or erasing from, magnetic disks (G11B17/00, G11B19/00 take precedence)
- G11B 5/3948: {the sensitive elements being active read-out elements}
- G11B 5/4886: {relative to rotating disc}
- G11B 20/10222: {clock-related aspects, e.g. phase or frequency adjustment or bit synchronisation (dedicated sync patterns in the modulation code G11B20/1403)}
- G11B 20/10268: {bit detection or demodulation methods}
- G11B 5/3954: {the active elements transducing on a single track}
- G11B 5/746: {Bit Patterned record carriers, wherein each magnetic isolated data island corresponds to a bit}
- 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

An assembly and method to determine adjacent track coherence is disclosed. The assembly includes coherence circuitry configured to receive phase and frequency offsets from timing recovery circuitry and determine an inter-track phase and frequency coherence between the encoded data on a first track and the encoded data on a second track adjacent to the first track utilizing the frequency and phase offsets from the timing recovery circuitry for the output signals corresponding to the first and second tracks.

## Claims

### Claim 1

An assembly comprising:
timing recovery circuitry configured to process a first signal corresponding to input from a first track utilizing a first reference pattern to provide a first phase and frequency offset for the first signal and process a second signal different from the first signal corresponding to input from the first track and a second track utilizing a second inter-track reference pattern to provide a second phase and frequency offset for the second signal; and
coherence circuitry including circuit components configured to use the first phase and frequency offsets for first signal and the second phase and frequency offset for the second signal outputted from the timing recovery circuitry to determine an inter-track phase and frequency coherence between the first and second tracks.

### Claim 2 (depends on 1)

The assembly of claim 1 and comprising a transducer head including a first read element and a second read element spaced from the first read element and the first signal is provided by the first read element and the second signal is provided by the second read element.

### Claim 3 (depends on 2)

The assembly of claim 2 wherein the timing recovery circuitry is configured to process the first signal from the first read element from a timing field on the first track relative to the reference pattern and the timing recovery circuitry is configured to process the second signal from the second read element from timing fields on the first and second tracks and provide the phase and frequency offsets for the second signal relative to the second inter-track reference pattern.

### Claim 4 (depends on 1)

The assembly of claim 1 wherein the circuit components of the coherence circuitry are configured to determine a differential between the phase or frequency offsets for the first and second signals and multiple the differential by a skew factor to determine the inter-track phase or frequency coherence.

### Claim 5 (depends on 1)

The assembly of claim 1 wherein the circuit components of the coherence circuitry apply phase and frequency transfer functions derived numerically to determine the inter-track phase and frequency coherence based upon the phase and frequency offsets determined from the timing recovery circuitry for the first and second signals.

### Claim 6 (depends on 1)

The assembly of claim 1 comprising signal processing circuitry including circuit components configured to use the inter-track phase and frequency coherence between the first and second tracks to decode user data on the first and second tracks.

### Claim 7 (depends on 1)

The assembly of claim 1 wherein the circuit components of the coherence circuitry are configured to use initial inter-track phase and frequency offsets from the coherence circuitry to determine the inter-track phase coherence at a sampling instance n by multiplying the initial inter-track frequency offset by the sampling instance n and adding the initial inter-track phase offset.

### Claim 8 (depends on 1)

The assembly of claim 1 wherein the coherence circuitry uses a phase transfer function to output an inter-track phase offset where the phase transfer function is provided by the equation
x
0
=
(
a
+
b
)
b
⁢
(
x
0
⁢
B
-
x
0
⁢
⁢
AB
)
where x0 is an inter-track first phase offset, X0B is the phase offset for the first signal from a first read element RB, X0AB is the second phase offset for the second signal from a second read element RAB, and a and b are coherence factors.

### Claim 9 (depends on 1)

The assembly of claim 1 wherein the coherence circuitry uses a frequency transfer function to output an inter-track frequency offset where the frequency transfer function is provided by the equation
f
0
=
(
a
+
b
)
b
⁢
(
f
0
⁢
B
-
f
0
⁢
AB
)
where f0 is an inter-track frequency offset, f0B is the first frequency offset for the first signal from a first read element RB, f0AB is the second frequency offset for the second signal from a second read element RAB, and a and b are coherence factors.

### Claim 10

An assembly comprising:
timing recovery means for determining phase and frequency offsets for first and second signals corresponding to encoded data on first and second tracks of a data storage media utilizing a first reference pattern for the first signal and a second inter-track reference pattern for the second signal; and
coherence means for determining inter-track phase and frequency coherence between the encoded data on the first and second tracks using the phase and frequency offsets for the first and second signals from the timing recovery means.

### Claim 11 (depends on 10)

The assembly of claim 10 wherein the timing recovery means uses the first reference pattern to determine the phase and frequency offsets for the first signal from a first read element and the second inter-track reference pattern to determine the phase and frequency offsets for the second signal from a second read element.

### Claim 12 (depends on 10)

The assembly of claim 10 wherein the coherence means comprises circuit components configured to apply a phase transfer function to determine an inter-track phase offset between the first and second tracks based upon the phase offsets for the first and second signals corresponding to the first and second tracks and a frequency transfer function to determine an inter-track frequency offset between the first and second tracks based upon the frequency offsets for the first and second signals corresponding to the first and second tracks.

### Claim 13

A method comprising
utilizing phase and frequency offsets determined by timing recovery circuitry for first and second signals corresponding to encoded data on first and second tracks of a data storage media to determine inter-track phase and frequency coherence including an initial inter-track phase offset and initial inter-track frequency offset between the adjacent first and second tracks of the data storage media; and
detennining an inter-track phase offset at sampling instance n by multiplying the initial inter-track offset by the sampling instance n and adding the initial inter-track phase offset.

### Claim 14 (depends on 13)

The method of claim 13 wherein the first signal is provided from a first read element on a transducer head and the second signal is provided from a second read element on the transducer head and comprising the steps of receiving the first signal from the first read element and receiving the second signal from the second read element to determine the phase and frequency offsets.

### Claim 15 (depends on 13)

The method of claim 13 wherein the first and second signals are provided from a single read element and comprising the step of receiving the first signal from the read element aligned with the first track during one rotation of the data storage media and receiving the second signal from the read element aligned with the first and second tracks during another rotation of the data storage media to determine the phase and frequency offsets.

### Claim 16 (depends on 13)

The method of claim 13 wherein in the step of utilizing the phase and frequency offsets to determine the inter-track phase and frequency coherence comprises using a differential between the phase and frequency offsets for the second signal and the phase and frequency offsets for the first signal to determine the inter-track phase and frequency coherence.

### Claim 17 (depends on 16)

The method of claim 16 wherein the first and second signals are provided from one or more read elements on a transducer head and comprising the step of:
applying a skew factor to the differential between the phase and frequency offsets for the first and second signals to account for skew angle of the one or more read elements relative to the data storage media.

### Claim 18 (depends on 13)

The method of claim 13 and comprising:
determining the phase and frequency offsets for the first signal based upon a reference pattern for the first track; and
determining the phase and frequency offsets for the second signal relative to an inter-track reference pattern for the first and second tracks.