Data storage device filtering burst correction values before downsampling the burst correction values
View Patent ↗A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of servo tracks defined by servo bursts. A number of burst correction values are generated by reading at least one of the servo bursts at a number of different radial locations across the disk. The burst correction values are filtered to generate filtered burst correction values, and the filtered burst correction values are downsampled to generate downsampled burst correction values. The downsampled burst correction values are written to the disk, and the head is servoed over the disk by reading the downsampled burst correction values from the disk.
1. A data storage device comprising:
a disk comprising a plurality of servo tracks defined by servo bursts;
a head; and
control circuitry configured to:
generate a number of burst correction values by reading at least one of the servo bursts at a number of different radial locations across the disk;
filter the burst correction values to generate filtered burst correction values;
downsample the filtered burst correction values to generate downsampled burst correction values;
write the downsampled burst correction values to the disk; and
servo the head over the disk by reading the downsampled burst correction values from the disk.
2. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to:
generate an intermediate burst correction value based on at least a first and second one of the downsampled burst correction values read from the disk; and
servo the head over the disk based on the intermediate burst correction value.
3. The data storage device as recited in claim 2 , wherein the control circuitry is further configured to generate the intermediate burst correction value by interpolating the first and second downsampled burst correction values.
4. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to filter the burst correction values based on:
L
n
′
=
{
∑
i
=
-
N
N
a
i
L
n
+
i
,
n
∈
[
N
+
1
,
m
-
N
]
and
n
is
even
1
2
(
L
n
-
1
′
+
L
n
+
1
′
)
=
∑
i
=
-
N
N
a
i
L
n
-
1
+
i
L
n
+
1
+
i
2
,
n
∈
[
N
+
1
,
m
-
N
]
and
n
is
odd
where:
L′ n represents the filtered burst correction values;
N represents an order of the filtering; and
a i represents coefficients of the filtering.
5. The data storage device as recited in claim 4 , wherein the control circuitry is further configured to generate the coefficients a i of the filtering based on:
ⅆ
MSE
ⅆ
a
j
=
2
E
{
(
L
n
′
-
L
n
)
L
n
+
j
}
+
2
E
{
(
L
n
+
1
′
-
L
n
+
1
)
(
L
n
+
j
+
L
n
+
2
+
j
2
)
}
=
0
,
j
∈
[
-
N
,
N
]
,
n
is
even
where the E operator computes a mean squared error.
6. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to generate a burst correction value at a centerline of one of the servo tracks, ±25 percent away from the centerline, and ±50 percent away from the centerline.
7. The data storage device as recited in claim 6 , wherein the control circuitry is further configured to downsample the filtered burst correction values to generate downsampled burst correction values at ±25 percent away from the centerline.
8. A method of operating a data storage device, the method comprising:
generating a number of burst correction values by reading at least one of a plurality of servo bursts on a disk at a number of different radial locations across the disk;
filtering the burst correction values to generate filtered burst correction values;
downsampling the filtered burst correction values to generate downsampled burst correction values;
writing the downsampled burst correction values to the disk; and
servoing the head over the disk by reading the downsampled burst correction values from the disk.
9. The method as recited in claim 8 , further comprising:
generating an intermediate burst correction value based on at least a first and second one of the downsampled burst correction values read from the disk; and
servoing the head over the disk based on the intermediate burst correction value.
10. The method as recited in claim 9 , further comprising generating the intermediate burst correction value by interpolating the first and second downsampled burst correction values.
11. The method as recited in claim 8 , further comprising filtering the burst correction values based on:
L
n
′
=
{
∑
i
=
-
N
N
a
i
L
n
+
i
,
n
∈
[
N
+
1
,
m
-
N
]
and
n
is
even
1
2
(
L
n
-
1
′
+
L
n
+
1
′
)
=
∑
i
=
-
N
N
a
i
L
n
-
1
+
i
L
n
+
1
+
i
2
,
n
∈
[
N
+
1
,
m
-
N
]
and
n
is
odd
where:
L′ n represents the filtered burst correction values;
N represents an order of the filtering; and
a i represents coefficients of the filtering.
12. The method as recited in claim 11 , further comprising generating the coefficients a i of the filtering based on:
ⅆ
MSE
ⅆ
a
j
=
2
E
{
(
L
n
′
-
L
n
)
L
n
+
j
}
+
2
E
{
(
L
n
+
1
′
-
L
n
+
1
)
(
L
n
+
j
+
L
n
+
2
+
j
2
)
}
=
0
,
j
∈
[
-
N
,
N
]
,
n
is
even
where the E operator computes a mean squared error.
13. The method as recited in claim 8 , further comprising generating a burst correction value at a centerline of one of the servo tracks, ±25 percent away from the centerline, and ±50 percent away from the centerline.
14. The method as recited in claim 13 , further comprising downsampling the filtered burst correction values to generate downsampled burst correction values at ±25 percent away from the centerline.