Nimbelink Corp. v. Digi International Inc.

NOTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
NIMBELINK CORP.,
Plaintiff-Appellant
v.
DIGI INTERNATIONAL INC.,
Defendant-Appellee
______________________
2024-2292
______________________
Appeal from the United States District Court for the
District of Minnesota in No. 0:22-cv-02345-NEB-DJF,
Judge Nancy E. Brasel.
______________________
Decided: February 23, 2026
______________________
D EVAN V. PADMANABHAN , Padmanabhan & Dawson
PLLC, Minneapolis, MN, argued for plaintiff-appellant.
Also represented by ERIN D UNGAN , BRITTA LOFTUS , M ARIAH
L. REYNOLDS , PAUL J. ROBBENNOLT.
K ATHERINE S. RAZAVI, Faegre Drinker Biddle & Reath
LLP, Minneapolis, MN, argued for defendant-appellee.
Also represented by K ELLY J. FERMOYLE, TIMOTHY E.
G RIMSRUD ; ANDREW M. M CCOY, Indianapolis, IN.
______________________
Case: 24-2292 Document: 40 Page: 1 Filed: 02/23/2026

-- 1 of 12 --

NIMBELINK CORP . v. DIGI INTERNATIONAL INC. 2
Before M OORE, Chief Judge, D YK and TARANTO , Circuit
Judges.
M OORE, Chief Judge.
NimbeLink Corp. (NimbeLink) appeals an invalidity
judgment from the United States District Court for the Dis-
trict of Minnesota and the dismissal of NimbeLink’s
breach-of-contract claims. For the following reasons, we
reverse the judgment of invalidity and affirm the dismissal
of NimbeLink’s breach-of-contract claims.
BACKGROUND
NimbeLink owns U.S. Patent Nos. 9,497,570 and
9,838,066 (collectively, the Asserted Patents), which relate
to embedded cellular modems. ’570 patent at 1:11–14.1
The disclosed modems facilitate machine-to-machine com-
munication in remote environments via cellular networks.
’570 patent at 1:18–23, 35–43. Claim 1 of the ’570 patent
is representative:
1. A space-efficient cellular modem device for ma-
chine-to-machine communications, the modem de-
vice comprising:
a multi-layer printed circuit board defining
a top side and a bottom side and including
a first circuit layer adjacent the top side, a
second circuit layer adjacent the bottom
side, a ground plane layer, and a power
plane layer, the ground and power plane
1 Because the parties agree the Asserted Patents’
specifications are nearly identical, we cite to the specifica-
tion of the ’570 patent alone. NimbeLink Br. 3 n.1;
Digi Br. 7 n.1.
Case: 24-2292 Document: 40 Page: 2 Filed: 02/23/2026

-- 2 of 12 --

NIMBELINK CORP . v. DIGI INTERNATIONAL INC. 3
layers located between the first and second
circuit layers;
a cellular transceiver module configured to
communicate over a cellular wireless cellu-
lar network, the cellular transceiver mod-
ule comprising a processor and attached to
a top side of the multi-layer printed circuit
board;
electrical power-management components
attached to the multi-layer printed circuit
board, the power-management components
in electrical communication with the cellu-
lar transceiver module;
a first plurality of electrically-conductive
pins in electrical connection with the cellu-
lar transceiver module and aligned along a
first pin axis to form a first row of pins,
each of the first plurality of pins extending
outwardly and away from the bottom side
of the multi-layer printed circuit board;
a second plurality of electrically-conductive
pins in electrical connection with the cellu-
lar transceiver module and aligned along a
second pin axis to form a second row of
pins, each of the second plurality of pins ex-
tending outwardly and away from the bot-
tom side of the multi-layer printed circuit
board, the second row of pins located oppo-
site the first row of pins; and
a communications port in electrical com-
munication with the cellular transceiver
module, the communications port config-
ured to receive and transmit communica-
tion signals over the cellular wireless
network.
Case: 24-2292 Document: 40 Page: 3 Filed: 02/23/2026

-- 3 of 12 --

NIMBELINK CORP . v. DIGI INTERNATIONAL INC. 4
Id. at 6:6–41 (emphasis added).
In 2022, NimbeLink sued Digi International Inc. (Digi)
for allegedly infringing at least claim 1 of each of the As-
serted Patents with its accused XBee cellular modem prod-
ucts and breaching non-disclosure agreements (NDAs)
executed in 2015 (2015 NDA) and 2016 (2016 NDA). Nim-
beLink’s patent infringement claims proceeded to claim
construction, where the parties disputed whether the pre-
amble phrase appearing in every asserted independent
claim—“space-efficient cellular modem device”—is limit-
ing, and if so, whether the term “space-efficient” is indefi-
nite. See J.A. 9–27. The district court determined the
preamble was limiting because it recites additional struc-
ture the specification underscores as important to the in-
vention. J.A. 10–12. The court then held the term “space-
efficient” indefinite because the term failed to convey dis-
cernable, objective boundaries to a skilled artisan.
J.A. 14–22. Following the court’s determination, the par-
ties stipulated to judgment that all asserted claims of the
Asserted Patents are invalid as indefinite under 35 U.S.C.
§ 112(b) and that Digi therefore does not infringe any valid
claim of the Asserted Patents. See J.A. 3–4. The court ac-
cordingly entered judgment to that effect. Id.
NimbeLink’s breach-of-contract claims arise from an
independent set of factual allegations, which we accept as
true for the purposes of this appeal. In 2015, while the ap-
plication for the ’570 patent was pending, Digi sought Nim-
beLink’s help to develop a product that would incorporate
the Skywire2 product. J.A. 135 ¶ 16. NimbeLink and Digi
then entered into the 2015 NDA, under which they would
exchange information about product design. J.A. 135 ¶ 17;
J.A. 217–18. During the 2015 NDA’s term, Digi expressed
2 Skywire is NimbeLink’s line of cellular embedded
modems designed to provide plug-in cellular connectivity.
J.A. 133 ¶¶ 9–10.
Case: 24-2292 Document: 40 Page: 4 Filed: 02/23/2026

-- 4 of 12 --

NIMBELINK CORP . v. DIGI INTERNATIONAL INC. 5
interest in acquiring NimbeLink and asked to be educated
on the Skywire product, NimbeLink’s cellular certification
process, and the Skywire product’s market potential.
J.A. 135 ¶ 18. In December 2015, Nimbelink and Digi rep-
resentatives met twice to discuss the Skywire product, and
during those meetings, Nimbelink disclosed financial and
marketing information related to the Skywire product.
J.A. 135–36 ¶¶ 19, 26. Discussions continued through Jan-
uary 2016, when Digi informed Nimbelink that Digi was no
longer interested in an acquisition. Id. ¶¶ 19–20. Later
that year, however, Digi developed a renewed interest in
acquiring NimbeLink, prompting the parties to enter into
the 2016 NDA, under which Digi would receive marketing
and financial information from NimbeLink. J.A. 136 ¶ 22;
J.A. 137 ¶¶ 31–32. Digi ultimately chose not to acquire
NimbeLink; instead, in January 2017, Digi introduced its
own cellular modem products, including the XBee Cellular
modem product line. J.A. 136 ¶ 23; J.A. 138 ¶ 36. Nim-
beLink subsequently brought breach-of-contract claims al-
leging Digi violated the 2015 and 2016 NDAs. J.A. 137
¶¶ 28, 34. Digi moved to dismiss. See J.A. 29. The district
court granted Digi’s motion, concluding the complaint
failed to plausibly allege (1) the specific nature of the con-
fidential information allegedly disclosed under the NDAs
and (2) Digi’s unauthorized use. J.A. 33–36.
NimbeLink appeals the invalidity judgment and the
dismissal of its breach-of-contract claims. We have juris-
diction under 28 U.S.C. § 1295(a)(1).
D ISCUSSION
NimbeLink argues we should: (1) reverse the district
court’s holding that the preamble phrase “space-efficient
cellular modem device” is indefinite; and (2) reverse the
district court’s dismissal of NimbeLink’s breach-of-contract
claims because the complaint adequately alleges the na-
ture of the confidential information disclosed under the
Case: 24-2292 Document: 40 Page: 5 Filed: 02/23/2026

-- 5 of 12 --

NIMBELINK CORP . v. DIGI INTERNATIONAL INC. 6
NDAs, as well as Digi’s unauthorized use of that confiden-
tial information.
I. Preamble Construction
Whether preamble language is a claim limitation is a
question of law. Data Engine Techs. LLC v. Google LLC,
10 F.4th 1375, 1380 (Fed. Cir. 2021). We review a district
court’s claim construction based on intrinsic evidence de
novo and its subsidiary fact findings about extrinsic evi-
dence for clear error. Forest Lab’ys, LLC v. Sigmapharm
Lab’ys, LLC, 918 F.3d 928, 932–33 (Fed. Cir. 2019). Nor-
mally, a preamble is used to state a purpose or intended
use for the invention and therefore is generally not limit-
ing. Summit 6, LLC v. Samsung Elecs. Co., 802 F.3d 1283,
1292 (Fed. Cir. 2015). We have articulated a number of
guideposts to aid in determining whether the preamble is
limiting. For example, a preamble may be limiting if it re-
cites additional structure or steps the specification under-
scores as important, provides antecedent basis for a claim
limitation, or serves as a basis for distinguishing prior art
during prosecution. Catalina Mktg. Int’l, Inc. v. Coolsav-
ings.com, Inc., 289 F.3d 801, 808 (Fed. Cir. 2002).
Digi argues the Asserted Patents’ written description,
claim language, and prosecution history confirm the pre-
amble phrase “space-efficient cellular modem device” is
limiting. Digi Br. 17–21. The written description supports
that conclusion, in Digi’s view, for three reasons. First, the
written description identifies “space-efficient embedded
cellular modems” as the “present invention.” ’570 patent
at 1:12–14. Second, the written description refers to the
invention and embodiments as “space-efficient” cellular
modem devices, emphasizing the important role space effi-
ciency plays in the claimed invention. See id. at Abstract
(disclosing “[a] space-efficient cellular modem device”),
1:36–37 (disclosing that “[e]mbodiments of the invention
comprise various space-efficient, embedded cellular mo-
dems”). Third, the written description refers to the
Case: 24-2292 Document: 40 Page: 6 Filed: 02/23/2026

-- 6 of 12 --

NIMBELINK CORP . v. DIGI INTERNATIONAL INC. 7
structure, arrangement, or size of the cellular modem de-
vice as “space-efficient.” See, e.g., id. at 4:19–21 (“compact,
space-efficient embedded cellular modem”), 4:32 (“efficient
spacing of surface-mounted components”), 5:3–4 (“[t]he
space-efficient size of [the] embedded cellular modem”).
Digi argues the claims further suggest the preamble
phrase is limiting because the phrase provides antecedent
basis for multiple dependent claims reciting “the modem
device” or “the cellular modem device.” Compare id. at
claims 5–6, 15–16, with claims 1, 10. And finally, Digi ar-
gues the prosecution history shows the preamble phrase is
limiting because the examiner distinguished the prior art
based on the claimed cellular modem device’s “arrange-
ment, relative size and overall complete structure,” each of
which the specification describes as “space-efficient.”
J.A. 927 (notice of allowance); see ’570 patent at 4:19–21,
4:31–33, 5:3–6. While NimbeLink argues that “space-effi-
cient” is limiting (if the claims are not indefinite), NimbeL-
ink Br. 30–31, at the same time, NimbeLink argues “space-
efficient” does not recite essential structure, does not pro-
vide antecedent basis for any terms in the bodies of the
claims, and did not serve as a basis for distinguishing prior
art during prosecution. Id. We conclude that the term
“space-efficient” in the preamble is not a limitation.3
3 In determining whether the preamble phrase is
limiting, neither the parties’ constructions nor that of the
district court bind us on de novo review. See DSU Med.
Corp. v. JMS Co., 471 F.3d 1293, 1299 (Fed. Cir. 2006)
(“This court reviews claim construction without defer-
ence.”); Bancorp Servs., L.L.C. v. Sun Life Assur. Co. of
Canada (U.S.), 687 F.3d 1266, 1274 (Fed. Cir. 2012) (“Just
as a district court may construe the claims in a way that
neither party advocates, . . . we may depart from the dis-
trict court and adopt a new construction on appeal[.]”) (in-
ternal citations omitted).
Case: 24-2292 Document: 40 Page: 7 Filed: 02/23/2026

-- 7 of 12 --

NIMBELINK CORP . v. DIGI INTERNATIONAL INC. 8
Even accepting Digi’s premise that the written descrip-
tion identifies a “space-efficient cellular modem” as the
“present invention,” the preamble phrase does not recite
additional, essential structure beyond what is already oth-
erwise claimed. As the written description explains, a
skilled artisan may achieve space savings through various
design choices, including the use of a stacked or multi-layer
circuit board configuration, ’570 patent at 5:15–18; various
pin arrangements, id. at 4:7–13; the XBee form factor, id.
at 4:19–21; surface mount connectors, id. at 4:31–33; and a
micro-SIM card slot, id. at 5:9–11. Every such space-sav-
ing feature appears in the body of the various claims. See,
e.g., id. at 6:8–14 (reciting a multi-layer printed circuit
board), 7:17–24 (reciting two rows of outwardly extending,
electrically conductive pins), 8:10–11 (reciting a cellular
modem device conforming to an XBee form factor), 6:15–19
(reciting a cellular transceiver module attached to a top
side of—i.e., mounted on the surface of—the multi-layer
printed circuit board), 6:62–63 (reciting a micro-SIM card
slot). In other words, the claims themselves, by virtue of
their recited elements, already embody a degree of space
efficiency without relying on the preamble to add another
structural limitation. We conclude that the preamble de-
scribes a characteristic or result of the claimed design
choices, but it does not supply an additional structural re-
quirement necessary to define the invention. We have long
held that preamble language that merely extolls the bene-
fits or features of the claimed invention does not limit claim
scope. Catalina, 289 F.3d at 809. We conclude that the
term “space-efficient” in the preamble does exactly
this—extoll the virtues of the structurally complete inven-
tion contained within the body of the claim.
While Digi is correct that portions of the preamble pro-
vide antecedent basis for claim limitations contained
within the body of the claim, the dependent claims of the
’570 patent refer back to “the cellular modem device.”
’570 patent at claims 5–6, 15–16. A preamble that is
Case: 24-2292 Document: 40 Page: 8 Filed: 02/23/2026

-- 8 of 12 --

NIMBELINK CORP . v. DIGI INTERNATIONAL INC. 9
limiting in part does not transform nearby descriptive
words in the preamble into claim limitations. TomTom,
Inc. v. Adolph, 790 F.3d 1315, 1323 (Fed. Cir. 2015) (“[t]hat
[part of] the phrase in the preamble . . . provides a neces-
sary structure for [independent] claim 1 does not neces-
sarily convert the entire preamble into a limitation”). That
is particularly true when, as here, the bodies of the depend-
ent claims recite a structurally complete device “such that
deletion of [‘space-efficient’] does not affect the struc-
ture . . . of the claimed invention.” Id. at 1324 (quoting Am.
Med. Sys., Inc. v. Biolitec, Inc., 618 F.3d 1354, 1358–59
(Fed. Cir. 2010)) (internal quotations omitted). We con-
clude that the bodies of the claims at issue define a com-
plete and operative invention and that the preamble
language is not, in this case, an additional claim limitation
beyond what is already contained in the body of the claim.
The prosecution history does not compel a different
conclusion. In the reasons for allowance, the examiner
noted “[w]hen taken as a whole, in combination, none of the
prior art discloses” the claimed cellular modem’s “specific
circuit structure including the arrangement, relative size
and overall complete structure.” J.A. 927. This examiner
reference does not demonstrate reliance on the term
“space-efficient” in the preamble as a limitation.
Georgetown Rail Equip. Co. v. Holland L.P., 867 F.3d 1229,
1236 (Fed. Cir. 2017) (quoting Catalina, 289 F.3d at 808)
(holding that a term in the preamble was not limiting
where there was no clear reliance on it to distinguish the
claimed invention from the prior art).
We see no basis to deviate from the general rule that
preamble language is not limiting. The claims at issue de-
scribe a complete and operative invention. The preamble
does not introduce essential structure but rather extolls
the virtues of the claimed invention. Therefore, we reverse
the judgement of invalidity.
Case: 24-2292 Document: 40 Page: 9 Filed: 02/23/2026

-- 9 of 12 --

NIMBELINK CORP . v. DIGI INTERNATIONAL INC. 10
II. Breach-of-Contract Claims
We review the grant of a motion to dismiss according
to the law of the regional circuit, here the Eighth Circuit.
Disc Disease Sols. Inc. v. VGH Sols., Inc., 888 F.3d 1256,
1259 (Fed. Cir. 2018) (citing Cleveland Clinic Found. v.
True Health Diags. LLC, 859 F.3d 1352, 1359 (Fed. Cir.
2017)). The Eighth Circuit reviews the grant of a motion
to dismiss de novo. Affordable Comtys. of Mo. v. Federal
Nat’l Mortg. Ass’n, 714 F.3d 1069, 1073 (8th Cir. 2013). In
doing so, the Eighth Circuit “accept[s] all facts pled by the
nonmoving party as true and draw[s] all reasonable infer-
ences from the facts in favor of the nonmovant.” Waldron
v. Boeing Co., 388 F.3d. 591, 593 (8th Cir. 2004).
NimbeLink argues the district court erred in two re-
spects by dismissing the breach-of-contract claims. Nim-
beLink Br. 46–53. First, as to confidential information,
NimbeLink argues it is not required to disclose the infor-
mation itself; instead, it need only describe the nature of
that information, which NimbeLink maintains it did with
sufficient detail. See, e.g., J.A. 135 ¶ 18 (alleging Digi
sought information regarding the Skywire product and
NimbeLink’s cellular certification process); id. at ¶ 19 (al-
leging NimbeLink provided Digi “technical information” re-
garding the Skywire product and “detailed business and
market strategy information that underlies the success of
the Skywire[] product” under the 2015 NDA); J.A. 136 ¶ 22
(alleging NimbeLink provided Digi “financial and market
information . . ., including detailed financial information
about the Skywire[] product and information about the
market for that product” under the 2016 NDA). Second, as
to unauthorized use, NimbeLink argues it plausibly al-
leged that Digi used NimbeLink’s confidential information
in breach of the NDAs to launch a competing cellular mo-
dem. See, e.g., J.A. 137 ¶ 27 (alleging “[d]uring the term of
the 2015 NDA, Digi used NimbeLink’s Proprietary Infor-
mation for non-permitted uses,” including to develop and
enter the market with its own cellular modem products);
Case: 24-2292 Document: 40 Page: 10 Filed: 02/23/2026

-- 10 of 12 --

NIMBELINK CORP . v. DIGI INTERNATIONAL INC. 11
id. at ¶ 28 (alleging “Digi’s non-permitted uses of NimbeL-
ink’s Proprietary Information constitute a breach of the
2015 NDA”); id. at ¶¶ 33–34 (alleging the same regarding
the 2016 NDA). Taken together, NimbeLink contends
these allegations suffice to state a breach-of-contract claim.
We do not agree.
NimbeLink’s complaint fails to sufficiently plead the
nature of the alleged confidential information at issue.
NimbeLink characterizes that information as relating to
“financ[e] and marketing,” but that is too vague to pass
muster under Rule 8. See Sip-Top, Inc. v. Ekco Grp., Inc.,
86 F.3d 827, 831 (8th Cir. 1996) (when a breach-of-contract
claim is based on the alleged use of confidential infor-
mation, the plaintiff must demonstrate the information al-
legedly used in violation of the contract “was the type of
information covered by the Confidentiality Agreement”).
NimbeLink’s description of the alleged confidential infor-
mation as “technical” or related to “business and marketing
strategy” does not meaningfully distinguish between confi-
dential and non-confidential information to survive the mo-
tion to dismiss. J.A. 135 ¶ 19. While NimbeLink alleges
with more particularity that it provided Digi information
about the Skywire product and cellular certification pro-
cesses, it fails to allege that information was confidential.
Id. at ¶ 18. NimbeLink correctly notes Rule 8 does not re-
quire disclosure of the confidential information itself, but
the rule does require sufficient factual content to allow the
court to draw the reasonable inference that Digi is liable
for the misconduct alleged. Ashcroft v. Iqbal, 556 U.S. 662,
678 (2009). Like the district court, we conclude that Nim-
beLink’s complaint fails to meet this requirement.
The complaint also fails to plausibly allege unauthor-
ized use of confidential information. NimbeLink’s theory
of breach rests primarily on Digi’s later introduction of
competing modem products after the NDA-governed dis-
cussions concluded. But the 2015 NDA expressly permits
independent development. J.A. 217 (“[N]either Party will
Case: 24-2292 Document: 40 Page: 11 Filed: 02/23/2026

-- 11 of 12 --

NIMBELINK CORP . v. DIGI INTERNATIONAL INC. 12
be precluded from independently developing technology or
pursuing business opportunities similar to those covered
by this Agreement.”). And the 2016 NDA prohibits an in-
ference of breach from the mere fact of later competition.
J.A. 260 (establishing Digi’s use of “practices, techniques,
concepts or information as those used by [NimbeLink]”
does not “give rise to any inference that any Information
was used or disclosed in violation of this agreement”). Un-
der these circumstances, NimbeLink’s allegations do not
support a reasonable inference that Digi used NimbeLink’s
confidential financial information rather than its own
knowledge, experience, or any information exchanged be-
tween the parties that Digi was permitted to use. We can-
not say the district court erred in dismissing the breach-of-
contract claims under these circumstances.
CONCLUSION
We have considered Digi’s remaining arguments and
find them unpersuasive. We reverse the judgment of inva-
lidity. We affirm the dismissal of NimbeLink’s breach-of-
contract claims.
AFFIRMED-IN-PART, REVERSED-IN-PART,
AND REMANDED
COSTS
No costs.
Case: 24-2292 Document: 40 Page: 12 Filed: 02/23/2026

-- 12 of 12 --