Viasat, Inc. v. Western Digital Technologies, Inc.

N OTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
VIASAT, INC.,
Appellant
v.
WESTERN DIGITAL TECHNOLOGIES, INC.,
Appellee
______________________
2024-1483
______________________
Appeal from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in No. IPR2022-
01171.
______________________
Decided: January 7, 2026
______________________
MATTHEW R. F ORD, Bartlit Beck LLP, Chicago, IL, ar-
gued for appellant. Also represented by MEG E. F ASULO,
N EVIN M. G EWERTZ, J OHN SCOTT M CBRIDE, RAVI SHAH ;
N OSSON K NOBLOCH , Denver, CO; D AVID ZIMMER, Zimmer,
Citron & Clarke LLP, Cambridge, MA.
BRIAN M. BUROKER, Gibson Dunn & Crutcher, LLP,
Washington, DC, argued for appellee. Also represented by
N ATHAN ROBERT CURTIS , Dallas, TX; L. K IERAN
K IECKHEFER , San Francisco, CA.
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VIASAT, INC. v. WESTERN DIGITAL TECHNOLOGIES, INC. 2
______________________
Before CHEN, BRYSON , and CUNNINGHAM , Circuit Judges.
BRYSON, Circuit Judge.
In this appeal from a final written decision of the Pa-
tent Trial and Appeal Board, the patentee, Viasat, Inc.,
(“Viasat”) challenges the Board’s decision that certain
claims of Viasat’s patent-in-suit are unpatentable for obvi-
ousness. We hold that substantial evidence supports the
Board’s obviousness decision, and we therefore affirm.
I
Viasat is the owner of U.S. Patent No. 8,966,347 (“the
’347 patent”), titled “Forward Error Correction with Paral-
lel Error Detection for Flash Memories.” The patent is di-
rected to methods and systems for error correction in data
retrieved from flash memory. Because flash memory is
prone to an increasing error rate in the data over time, the
invention is designed to modify the error correction process
to make it more robust as the number of errors in the stored
data begins to climb.
One method for correcting errors in flash memory data
is to use a technique referred to as forward error correction
(“FEC”), which generally uses an error correction code
(“ECC”) to generate and store redundant information
alongside the original data. When the original data is re-
trieved from memory, it is compared against the redundant
information, which enables the system to detect and ulti-
mately correct the corrupted data.
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VIASAT, INC. v. WESTERN DIGITAL TECHNOLOGIES, INC. 3
System claims 13 through 23 of the ’347 patent are at
issue in this case.1 Independent claim 13 is representative.
It reads as follows:
13. A system comprising:
[a] an encoder to encode data using forward error cor-
rection coding;
[b] a flash memory to store the encoded data;
[c] a decoder to retrieve the encoded data stored in the
flash memory to generate a data stream, and [d] to process
the data stream to correct errors in the data stream asso-
ciated with the flash memory using at least a first error
correction sub-module; and
[e] a controller to:
monitor a metric of the flash memory while repeat-
ing the encoding, the storing, the retrieving and the
processing, wherein the metric represents memory per-
formance degradation of the flash memory;
[f] determine that the monitored metric exceeds a
threshold;
[g] in response to the determination, modify the for-
ward error correction coding for use by the encoder in
subsequently encoding data for storage in the flash
memory; and
[h] in response to the determination, powering-up,
from an inactive mode, a second error correction sub-
module arranged in parallel with the first error
1 The PTAB also found method claims 1–11 to be un-
patentable, but Viasat has not appealed the PTAB’s deci-
sion with respect to those claims.
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VIASAT, INC. v. WESTERN DIGITAL TECHNOLOGIES, INC. 4
correction sub-module for subsequent data stream pro-
cessing.2
’347 patent, col. 11, line 40, through col. 12, line 10.
For present purposes, the critical portions of claim 13
are limitations 13[c] and 13[d], which describe the function
of the decoder as being “to retrieve the encoded data stored
in the flash memory to generate a data stream, and to pro-
cess the data stream to correct errors in the data stream
associated with the flash memory using at least a first er-
ror correction sub-module.” Id., col. 11, ll. 44–48.
II
Western Digital Technologies, Inc., (“Western Digital”)
filed a petition for inter partes review of claims 1 through
11 and 13 through 23 of the ’347 patent. The Patent Trial
and Appeal Board granted the petition, and in its final
written decision the Board found all the challenged claims
to be unpatentable for obviousness. J.A. 1. In so finding,
the Board relied on prior art published patent applications
to Diggs and Cheng.3 While the Board relied on combina-
tions of Diggs and Cheng for the disclosure of certain limi-
tations, its decision found that the 13[c] and 13[d]
limitations at issue on appeal were disclosed by Diggs
alone, and thus only Diggs is relevant to our analysis here.
J.A. 29–32.
2 In its briefing before the Board, Western Digital
added the bracketed letters to the claims to facilitate anal-
ysis, and Viasat relied on these same letter assignments in
its appellate brief. The claims are reproduced here includ-
ing the bracketed letters employed by the parties and the
Board.
3 The Diggs reference is Pub. No. US 2009/0070651;
the Cheng reference is Pub. No. US 2009/0276570.
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VIASAT, INC. v. WESTERN DIGITAL TECHNOLOGIES, INC. 5
Diggs is directed to a system for adjustable error cor-
rection in solid-state storage systems, such as flash
memory storage. Diggs ¶¶ 2, 4, 7–8, J.A. 451. The Diggs
system is very similar to the invention recited in the ’347
patent, in that the Diggs system, like the patented system,
uses a controller and a decoding device to retrieve signals
from the solid-state memory, to decode those signals, and
to detect and correct the errors in the data revealed by the
error correction mechanism.
In the portion of its decision pertinent to the issue pre-
sented in this appeal, the Board addressed Western Digi-
tal’s argument that the “decoder” recited in claim 13 of the
’347 patent is disclosed by the Diggs Controller. The Board
noted that figure 1 of Diggs, which depicts an embodiment
of the Diggs invention, shows that Diggs contains a Con-
troller, designated as component 114. The Controller in-
corporates the ECC Detection and Correction module,
which is designated as component 125. Diggs ¶ 23, J.A.
452. Figure 1 of Diggs, J.A. 447, is depicted below.
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VIASAT, INC. v. WESTERN DIGITAL TECHNOLOGIES, INC. 6
In the proceedings before the Board, the parties fo-
cused on whether Diggs teaches a “decoder” that both “re-
trieve[s] the encoded data stored in the flash memory to
generate a data stream,” as recited in claim element 13[c]
of the ’347 patent, and also “process[es] the data stream to
correct errors in the data stream,” as recited in claim ele-
ment 13[d] of the patent.
The parties agreed that the component denominated
“Controller” in Diggs (component 114) performs the func-
tion of retrieving the encoded data to generate a data
stream, and that the component denominated “ECC Detec-
tion and Correction” in Diggs (component 125) performs
the function of processing the data stream to correct errors.
J.A. 30–31. The parties disagreed, however, about whether
that meant that the component in Diggs that performs the
retrieval function is separate from the component that per-
forms the error correction function.
Viasat argued that because the retrieval function in
Diggs is performed by the Diggs Controller, and the correc-
tion function in Diggs is performed by the ECC Detection
and Correction component, the two functions are not per-
formed by a single decoder, but are performed by different
components. Western Digital responded that in Diggs the
ECC Detection and Correction module (125) is part of the
Controller (114) and thus the same component performs
the functions of data retrieval and correction.
The Board noted that it was undisputed that Diggs’s
ECC Detection and Correction module (125) is incorpo-
rated within the Diggs Controller (114). J.A. 31. For that
reason, the Board found that the Diggs Controller, includ-
ing the incorporated ECC Detection and Correction mod-
ule, performs the two related functions of the “decoder,” as
set forth in claim 13[c] of the ’347 patent.
The Board explained that although the ECC module in
Diggs “handles the decoding, and another portion of
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VIASAT, INC. v. WESTERN DIGITAL TECHNOLOGIES, INC. 7
controller 114 handles data retrieval, this division of labor
is not inconsistent with claim 13, which does not require
that the functions of a decoder reside within one circuit.”
J.A. 31. Accordingly, despite the difference in terminology
between Diggs and claim 13 of the ’347 patent, the Board
found that “the structure disclosed by Diggs fits comforta-
bly within the structure defined by claim 13,” id., and that
Diggs therefore discloses circuitry that performs both the
tasks of retrieving data from the flash memory and pro-
cessing that data to correct errors.
Based on that analysis, the Board found that the dif-
ference between the relevant portions of the structures de-
scribed in Diggs and in claim 13 was a “semantic
discrepanc[y]” rather than a difference in substance. J.A.
31–32 (internal citation omitted). The Board therefore con-
cluded that Western Digital had shown that claim 13 of the
’347 patent was unpatentable for obviousness. Based on
that conclusion and its analysis of the other claims before
it, the Board found that claims 1 through 11 and claims 13
through 23 would have been obvious in light of the combi-
nation of Diggs and Cheng.
Viasat appealed to this court, focusing entirely on the
Board’s analysis of the patentability of claim 13.4
III
Viasat’s argument on appeal is simple: Viasat con-
tends that claim 13 of the ’347 patent requires that the “de-
coder” both “retrieve the encoded data” and “correct
errors.” Appellant’s Br. 1. In Diggs, according to Viasat,
4 Viasat has not challenged the Board’s finding that
limitation 13[h] is taught by Cheng and that, subject to the
dispute over limitations 13[c] and [d], claims 1–11 and 14–
23 are rendered obvious by the combination of Diggs and
Cheng.
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VIASAT, INC. v. WESTERN DIGITAL TECHNOLOGIES, INC. 8
the Controller retrieves the encoded data, while the de-
coder (the ECC Detection and Correction module, accord-
ing to Viasat) is “presented with the data already retrieved
from flash by the controller.” Id. at 2. Viasat argues that
the controller of claim 13 does not retrieve the data stream
from the flash memory, but simply monitors the error rate
and activates the additional error correction feature if and
when needed. Id. According to Viasat, the difference in the
respective roles of those two components in Diggs and in
the device recited in claim 13 constitutes a fundamental
structural distinction between the architecture of Diggs
and the architecture of claim 13. In view of that difference,
Viasat argues, the Board erred in finding that the limita-
tions in claim elements 13[c] and [d] were disclosed by
Diggs.
Viasat’s argument is not persuasive. As shown in fig-
ure 1 of Diggs, the decoding mechanism in Diggs–the ECC
Detection and Correction module (125)—is part of the
Diggs Controller (114). For that reason, the Board found
that the Controller in Diggs both receives the data stream
and processes it, thus performing all the functions of the
decoder recited in claim 13. J.A. 30–31.
The parties disagree about whether the Board’s deci-
sion was based on a finding of fact or on an implicit claim
construction. Viasat argues that claim 13 should be con-
strued to require that the functions of the controller and
the decoder be performed by separate entities, and that the
Board implicitly rejected that claim construction. Western
Digital, on the other hand, interprets the Board’s decision
as turning on a finding of fact—that the Diggs Controller
performs all the functions assigned by claim 13 to the de-
coder. Either interpretation would lead to the same con-
clusion, but we interpret the Board’s ruling as principally
based on a factual finding, and we therefore review the
Board’s decision for substantial evidence.
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VIASAT, INC. v. WESTERN DIGITAL TECHNOLOGIES, INC. 9
1. To begin with, it is undisputed that the Diggs Con-
troller receives the encoded data to generate a data stream.
In addition, it is clear that Diggs’s ECC Detection and Cor-
rection module, which processes the data stream to correct
errors, is part of the Diggs Controller. Thus, the Board was
justified in finding that the functions of receiving the data
stream from the flash memory and processing that data
stream to make corrections are both performed by the
Diggs Controller, even though in Diggs the latter function
is performed by a sub-module of the Controller.
According to Viasat, the difference between Diggs and
the invention recited in claim 13 of the ’347 patent is that
in Diggs the ECC Detection and Correction structure per-
forms one of the functions of the decoder of claim 13 (pro-
cessing the data stream to correct errors in the data
stream) but does not perform the other designated function
of the decoder (retrieving data from the flash memory to
generate a data stream). In Diggs, Viasat argues, that
function is performed not by the decoder (the ECC Detec-
tion and Correction module), but by the Controller.
As the Board found, that distinction is inconsequential.
Figure 1 of Diggs shows that the ECC Detection and Cor-
rection module (125) in Diggs is part of the Controller (114),
and the text of the Diggs reference confirms that the “con-
troller 114 further includes an ECC detection and correc-
tion module 125.” Diggs ¶ 23, J.A. 452. The two functions
that the ’347 patent assigns to the decoder are thus per-
formed by the Controller in Diggs through the incorporated
ECC Detection and Correction module. The Board there-
fore properly rejected Viasat’s core argument for distin-
guishing Diggs—that a single entity in Diggs does not
perform both the retrieval function and the processing
function. Accordingly, we reject Viasat’s argument, which
the Board properly characterized as reducing to one of no-
menclature.
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VIASAT, INC. v. WESTERN DIGITAL TECHNOLOGIES, INC. 10
2. We would reach the same result in this case if we
viewed the Board as having based its decision on an im-
plicit construction of claim 13, to wit, as not requiring that
the decoder and controller consist of physically separate
circuitry. The claim language does not compel us to inter-
pret claim 13 in that fashion, and in fact the specification
of the ’347 patent suggests the opposite.
The specification teaches that the encoder, decoder,
and controller “may, individually or collectively, be imple-
mented with one or more Application Specific Integrated
Circuits (ASICs) adapted to perform some or all of the ap-
plicable functions in hardware. Alternatively, the func-
tions may be performed by one or more other processing
units (or cores), on one or more integrated circuits.” ’347
patent, col. 3, ll. 34–40. That language indicates that the
claim language, properly construed, provides that the func-
tions of the decoder and the controller of claim 13 can be
performed by varying sets of circuits, individually or collec-
tively. In other words, they can be performed by the same
structure.
In arguing to the contrary, Viasat relies on two cases
involving mechanical patents in which the claims recited
inventions having distinct components. In the first, Bec-
ton, Dickinson & Co. v. Tyco Healthcare Group, 616 F.3d
1249 (Fed. Cir. 2010), the court wrote that when a claim
lists elements separately, “the clear implication of the
claim language is that those elements are distinct compo-
nents of the patented invention.” Id. at 1254 (citation mod-
ified). In the second, Kyocera Senco Industrial Tools Inc. v.
International Trade Commission, 22 F.4th 1369 (Fed. Cir.
2022), the court similarly explained that when a patent
claim separately lists two mechanical components, it is pre-
sumed that those components are distinct. Id. at 1382.
That presumption has force with regard to mechanical
patents, in which particular functions are typically
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VIASAT, INC. v. WESTERN DIGITAL TECHNOLOGIES, INC. 11
performed by physically discrete components. It is less
clearly applicable to electronic patents in which particular
functions are frequently performed by combinations of cir-
cuitry that are not necessarily contained in segregated
physical packages. What ultimately matters in this case is
whether the patent at issue indicates that the claimed
functions may be performed by a shared structure. See
Powell v. Home Depot U.S.A., Inc., 663 F.3d 1221, 1231–32
(Fed. Cir. 2011); Retractable Techs., Inc. v. Becton, Dickin-
son & Co., 653 F.3d 1296, 1304 (Fed. Cir. 2011); NTP Inc.
v. Research in Motion, 418 F.3d 1282, 1310 (Fed. Cir. 2005).
That point is illustrated by this court’s decision in Lin-
ear Technology Corp. v. International Trade Commission,
566 F.3d 1049 (Fed. Cir. 2009). That case involved claims
of an electronic patent that recited a “second circuit” and a
“third circuit” that performed particular functions. The In-
ternational Trade Commission construed those limitations
not to require the two circuits to be entirely distinct, with-
out common circuit elements. Instead, the Commission
construed the claim language to require only that the two
circuits perform their stated functions.
This court agreed with the Commission’s construction
of the terms “second circuit” and “third circuit,” holding the
two terms “to not require entirely separate and distinct cir-
cuits.” 566 F.3d at 1055. The court explained that
there is nothing in the claim language or specifica-
tion that supports narrowly construing the terms
to require a specific structural requirement or en-
tirely distinct “second” and “third” circuits. Rather,
the “second” and “third” circuits must only perform
their stated functions. For example, what is re-
quired is that the “second circuit” “generate[es] a
first control signal . . . to vary the duty cycle,” not
that any particular components make up this cir-
cuit. In fact, the ’258 patent’s specification
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VIASAT, INC. v. WESTERN DIGITAL TECHNOLOGIES, INC. 12
expressly discloses that the “second circuit” and
“third circuit” can share common components. For
example, figure 2 shows that components of the
“second circuit”—such as the reference circuit 37—
can also be part of the “third circuit.”
Id.
The same analysis applies in this case. While there is
overlap in the Diggs circuitry that performs the functions
of the controller and the decoder of the ’347 patent, nothing
in the ’347 patent suggests that such overlap is impermis-
sible. In fact, as noted above, the specification of the ’347
patent makes it clear that the components of the systems
claimed in the patent—particularly the encoder, the de-
coder, and the controller—may be implemented by various
circuits that individually or collectively are “adapted to
perform some or all of the applicable functions in hard-
ware.” ’347 patent, col. 3, ll. 33–40. See also id., col. 5, line
64, though col. 6, line 3 (“These components and sub-mod-
ules” may be implemented with circuits “adapted to per-
form some or all the applicable functions in hardware.
Alternatively, the functions may be performed by one or
more processing units (or cores), on one or more integrated
circuits.”). The specification of the ’347 patent thus makes
it clear that under the proper construction of claim 13, the
identity of the particular module or sub-module that per-
forms each task is not critical.
We agree with the Board that the Diggs reference maps
to the structures and functions set forth in claim elements
13[c] and [d] of the ’347 patent, and we therefore uphold
the Board’s decision that the combination of Diggs and
Cheng rendered claim 13 unpatentable for obviousness.
AFFIRMED
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