Court Opinion

ID: 6329054
Source: CourtListenerOpinion
Date Created: 2022-04-01 14:00:53.939456+00
Date Added: 2024-06-11T09:22:46.734616
License: Public Domain

Case: 20-2167   Document: 40     Page: 1   Filed: 04/01/2022

   United States Court of Appeals
       for the Federal Circuit
                 ______________________

     GENUINE ENABLING TECHNOLOGY LLC,
               Plaintiff-Appellant

                            v.

  NINTENDO CO., LTD., NINTENDO OF AMERICA
                    INC.,
             Defendants-Appellees
            ______________________

                       2020-2167
                 ______________________

    Appeal from the United States District Court for the
 Western District of Washington in No. 2:19-cv-00351-RSM,
 Judge Ricardo S. Martinez.
                  ______________________

                 Decided: April 1, 2022
                 ______________________

     DEVAN V. PADMANABHAN, Padmanabhan & Dawson,
 PLLC, Minneapolis, MN, argued for plaintiff-appellant.
 Also represented by ERIN DUNGAN, PAUL J. ROBBENNOLT.

    JERRY A. RIEDINGER, Perkins Coie, LLP, Seattle, WA,
 argued for defendants-appellees. Also represented by
 KEVIN ANDREW ZECK; ANDREW DUFRESNE, DAVID R.
 PEKAREK KROHN, Madison, WI.
                ______________________

    Before NEWMAN, REYNA, and STOLL, Circuit Judges.
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2       GENUINE ENABLING TECHNOLOGY      v. NINTENDO CO., LTD.

 REYNA, Circuit Judge.
      Genuine Enabling Technology LLC sued Nintendo Co.,
 Ltd. and Nintendo of America, Inc. accusing five products
 of infringing certain claims of U.S. Patent No. 6,219,730.
 The U.S. District Court for the Western District of Wash-
 ington construed the term “input signal,” which appears in
 all the asserted claims, consistent with the defendants’ pro-
 posed construction, and on that basis granted summary
 judgment of non-infringement in favor of the defendants.
 Genuine appeals, arguing that the district court erred in
 construing the limitation by improperly relying on extrin-
 sic evidence and by improperly finding that the inventor,
 Mr. Nguyen, disclaimed certain claim scope during prose-
 cution. We conclude that the district court erred in its con-
 struction of “input signal” and construe the term to mean
 “a signal having an audio or higher frequency.” Accord-
 ingly, we reverse the district court’s grant of summary
 judgment and remand for further proceedings consistent
 with this opinion.
                         BACKGROUND
                       The ’730 Patent
     On June 20, 1998, inventor Nghi Nho Nguyen filed a
 patent application that issued on April 17, 2001, as U.S.
 Patent No. 6,219,730. The ’730 patent is titled “Method
 and Apparatus for Producing a Combined Data Stream and
 Recovering Therefrom the Respective User Input Stream
 and at Least One Additional Input Signal.” The ’730 pa-
 tent discloses technology for combining data streams that
 Mr. Nguyen conceived when developing a “voice mouse”
 that conserved computer resources. Appellant’s Br. 7–8.
      According to the ’730 patent, in the prior art, comput-
 ers received user input via a “user input device” or “UID,”
 such as a mouse or keyboard. ’730 patent col. 1 ll. 14–18,
 col. 3 ll. 26–30. Computers also used “input/output” or
 “I/O” cards to process various types of signals. Id. at col. 1
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 GENUINE ENABLING TECHNOLOGY      v. NINTENDO CO., LTD.          3

 ll. 18–22. As an example of an I/O card, a sound card would
 be used to receive speech input from a microphone and to
 transmit speech output to a speaker. Id. at col. 3 ll. 26–30.
 The ’730 patent explains that devices and cards share com-
 puter resources and that their configuration can be cum-
 bersome:
     Devices and cards require and share common com-
     puter resources such as the direct memory access
     (DMA) channels and the interrupt request (IRQ)
     services. Computer resources for each device or
     each card equipped in a computer must be config-
     ured, or assigned, to pre-arranged memory loca-
     tions that are limited in number. Configuration
     setup for computer resources is cumbersome and
     sometimes causes conflict in running software.
 Id. at col. 1 ll. 21–28.
      To solve these problems, the ’730 patent “offers a new
 kind of UID utilizing the computer resources efficiently.”
 Id. at col. 1 ll. 41–42. The embodiment shown in Figure 1B
 “eliminates the [computer’s] sound card” so that the UID
 (i.e., mouse 18) “directly receives speech input from micro-
 phone 16 and transmits speech output to speaker 17.” Id.
 at col. 3 ll. 30–36. This arrangement involves the use of a
 “framer” that (i) receives input from the UID and external
 device (e.g., speaker or microphone), and (ii) “synchro-
 nize[s] and merge[s]” those data streams into a “combined
 data stream.” Id. at col. 4 ll. 28–31. Claim 1 is representa-
 tive and recites:
     1. A user input apparatus operatively coupled to a
     computer via a communication means additionally
     receiving at least one input signal, comprising:
         user input means for producing a user in-
         put stream;
         input means for producing the at least one
         input signal;
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4        GENUINE ENABLING TECHNOLOGY     v. NINTENDO CO., LTD.

          converting means for receiving the at least
          one input signal and producing therefrom
          an input stream; and
          encoding means for synchronizing the user
          input stream with the input stream and en-
          coding the same into a combined data
          stream transferable by the communication
          means.
 Id. at col. 7 l. 61–col. 8 l. 4.
     During prosecution, the examiner rejected pending
 claims 1–27 as obvious. J.A. 1762, 1767–69. In particular,
 the examiner rejected pending claims 1, 16, and 23 as ob-
 vious in light of U.S. Patent No. 5,990,866 (“Yollin”).
 J.A. 1768–69.
     Yollin is titled “Pointing Device with Integrated Physi-
 ological Response Detection Facilities.” Yollin explains
 that prior art pointing devices (e.g., a mouse, joystick, or
 stylus) typically provided two-dimensional motion infor-
 mation for a cursor (i.e., positional change information) as
 well as signals for pushing a button (i.e., user selection in-
 formation). Yollin at col. 1 ll. 27–38. According to Yollin,
 a subset of prior art devices also processed input known as
 biofeedback from physiological sensors, but those systems
 generally “require a separate dedicated physiological re-
 sponse input device that consumes a valuable I/O port of
 the computer system, and . . . rel[y] on a specialized dedi-
 cated program.” Id. at col. 1 ll. 53–62. Yollin thus disclosed
 “a pointing device with integrated physiological response
 detection facilities” that “does not consume excess I/O
 ports.” Id. at col. 1 l. 66–col. 2 l. 6.
     Yollin further described the types of physiological re-
 sponse sensors that could be used. Yollin’s invention could
 use “any of a number of alternative devices which measure
 any of a number of physiological responses of a user who
 contacts the sensor(s).” Id. at col. 3 l. 64–col. 4 l. 2.
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 GENUINE ENABLING TECHNOLOGY      v. NINTENDO CO., LTD.            5

 Exemplary sensors included “a [Galvanic Skin Response or
 GSR] sensor, an electromyograph (muscle tension), electro-
 cardiograph (heart activity), electroencephalograph (brain
 activity), thermometer (skin temperature), blood pressure
 sensor, and the like.” Id. at col. 4 ll. 5–10. Yollin, however,
 did not specifically discuss the frequencies of the signals
 generated by the physiological sensors.
      With respect to the “input signal” limitation of pending
 claims 1, 16, and 23, the examiner cited Yollin’s teaching
 of “input information received from motion translation unit
 102, user selection unit 104 and physiological response sen-
 sor(s) 106” as grounds for rejection. J.A. 1768 (citing Yollin
 at col. 5 ll. 16–18).
     Mr. Nguyen responded to the office action on Septem-
 ber 28, 2000, arguing that Yollin failed to adequately teach
 the limitation. Mr. Nguyen distinguished the “slow vary-
 ing” physiological response signals discussed in Yollin from
 the “signals containing audio or higher frequencies” con-
 templated by his invention on the ground that the latter
 signals pose a signal “collision” problem solved by Mr. Ngu-
 yen’s inventions:
     Yollin’s invention . . . utilizes various implementa-
     tions and configurations for receiving input from
     motion translation unit 102, user selection unit 104
     and physiological response sensor(s) 106, and for
     processing their information prior to communica-
     tion to the host system via communication inter-
     face 108 and channel 112. These configurations are
     standard and well-known to the artisan. However,
     Yollin only uses the configuration to receive the
     slow varying signal coming from the physiological
     response sensor(s). Yollin is not motivated and
     does not anticipate their use for receiving signals
     containing audio or higher frequencies in place of
     the physiological response sensor(s). The high fre-
     quency input signal, which comes from a source
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6       GENUINE ENABLING TECHNOLOGY        v. NINTENDO CO., LTD.

    different from those of motion and selection units,
    will run asynchronously relative to, and collide
    with, the other signals. Yollin’s invention does not
    teach or suggest any approach for receiving and re-
    covering that kind of input signal.
 J.A. 1784 (emphasis added). Mr. Nguyen then reiterated
 that distinction between Yollin and his inventions:
    [Yollin] utilizes . . . a controller to receive positional
    change information, user selection information and
    physiological change information to generate . . . a
    composite signal but does not anticipate its use with
    signals containing audio or higher frequencies. Us-
    ing a controller to generate the composite control
    signal out of the information changes, which are
    slow-varying, is standard and not worth [being]
    mentioned in Yollin’s description. Difficulties will
    arise when one signal runs asynchronously relative
    to another signal and fast. Yollin’s patent does not
    teach or suggest any method for the controller to
    receive and recover such signals. In contrast, this
    invention describes, in its representative embodi-
    ments, how to combine the data from a UID
    (mouse) and from a high-frequency signal, via a
    framer, which is unique and novel.
 J.A. 1785 (emphasis added). Mr. Nguyen made this essen-
 tial argument a third time:
    Yollin’s method of using the controller to generate
    a composite signal only works for slow varying sig-
    nals. In contrast, this invention teaches the arti-
    san the ways of synchronizing and encoding two
    sources of signals into a combined data, via a
    framer, before sending onto a communication link,
    and of recovering from the received combined data
    the original information of the respective signals.
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 GENUINE ENABLING TECHNOLOGY    v. NINTENDO CO., LTD.          7

 Id. (emphasis added). In late November 2000, the exam-
 iner entered an examiner’s amendment and allowed the
 claims. See J.A. 1796–810.
                 The District Court Action
     On February 8, 2017, Genuine Enabling Technology
 LLC (“Genuine”) filed an action against Nintendo Co., Ltd.
 and Nintendo of America, Inc. (collectively, “Nintendo”) in
 the U.S. District Court for the District of Delaware.
 J.A. 63. Genuine alleged that five Nintendo products in-
 fringe the ’730 patent: (1) the Wii Remote and Wii Remote
 Plus; (2) the Nunchuk; (3) the WiiU Game Pad; (4) the
 Switch Joy-Con Controller; and (5) the Nintendo Switch
 Pro Controller. Genuine Enabling Tech. LLC v. Nintendo
 Co., No. C19-351RSM, 2020 WL 4366163, at *1 (W.D.
 Wash. July 30, 2020). Specifically, Genuine alleged that
 these products contain functionality that infringe claims
 10, 14–18, 21–23, and 25 of the ’730 patent. Id. On March
 11, 2019, the case was transferred to the Western District
 of Washington. Id. at *4; J.A. 666.
     In early 2020, the parties submitted claim construction
 briefing in which they disputed the proper construction of
 the claim term “input signal” in all asserted claims. 1
 J.A. 1440–52, 1655–77. Genuine proposed the construc-
 tion, “a signal having an audio or higher frequency.”
 J.A. 1677. Nintendo proposed the following narrower con-
 struction:
    A signal containing audio or higher frequencies.
    Mr. Nguyen disclaimed signals that are 500 Hertz
    (Hz) or less. He also disclaimed signals that are
    generated from positional change information, user
    selection information, physiological response

    1   The district court held a Markman hearing on Feb-
 ruary 24, 2020. See J.A. 3263–321.
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8       GENUINE ENABLING TECHNOLOGY     v. NINTENDO CO., LTD.

    information, and other slow-varying information.
    Alternatively, indefinite.
 J.A. 1448. In support, Nintendo submitted a declaration
 by Dr. Howard Chizeck, which discussed the features and
 operation of physiological sensors such as those disclosed
 in the Yollin reference. J.A. 1542–55. Dr. Chizeck included
 a chart titled “Range and Frequency of Select Physiological
 Phenomena” and indicated that the information in the
 chart came from a reference he called “Yuce, et al.”
 J.A. 1551. The chart provided frequency ranges for signals
 associated with various physiological phenomena, includ-
 ing a range of 10–500 Hz for EMG (electromyogram). Id.
 Based on this chart, Dr. Chizeck opined that “the maxi-
 mum frequency of the signals from physiological sensors
 described by Yollin is at least 500 Hz.” J.A. 1553. Relying
 on Dr. Chizeck’s declaration, Nintendo argued that a per-
 son of ordinary skill in the art would have understood
 Yollin to teach physiological sensor signals having maxi-
 mum frequencies of at least 500 Hz, and that, therefore,
 Mr. Nguyen had disclaimed all such signals when he dis-
 tinguished Yollin from his inventions during prosecution.
 J.A. 1450–51. Nintendo accordingly opposed Genuine’s
 broader construction, which encompassed the range of fre-
 quencies that humans can hear (20 Hz to 20,000 Hz).
 J.A. 1451.
     On January 23, 2020, Nintendo moved for summary
 judgment of non-infringement, which was predicated on
 the district court’s acceptance of its claim construction of
 “input signal.” J.A. 2465–90. Nintendo argued that its ac-
 cused controllers produce the types of slow-varying signals
 that Mr. Nguyen disclaimed during prosecution when he
 distinguished his inventions from the Yollin reference. See
 J.A. 2482–84.
     On July 30, 2020, the district court issued an order
 granting Nintendo’s motion for summary judgment. Gen-
 uine, 2020 WL 4366163, at *1. The court construed the
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 “input signal” limitation in all asserted claims to mean
 “signals above 500 Hz and excluding signals generated
 from positional change information, user selection infor-
 mation, physiological response information, and other
 slow-varying information,” consistent with Nintendo’s pro-
 posed construction. Id. at *10. The court interpreted Mr.
 Nguyen’s arguments regarding Yollin during prosecution
 as “amount[ing] to disclaimer of the slow-varying signals
 addressed by Yollin.” Id. at *8. In particular, the court
 found Mr. Nguyen’s assertions “to be a clear expression by
 Mr. Nguyen that if a sensor produces signals at the fre-
 quency of those contemplated by Yollin, those frequencies
 do not pose a collision problem when combined with slow-
 varying button data and are therefore distinct from ‘fast-
 varying’ signals addressed by the ’730 patent.” Id. Based
 on this finding, the court determined that a person of ordi-
 nary skill in the art “would understand the upper bound of
 ‘slow-varying’ signals covered by Yollin to set the lower
 bound of ‘fast-varying’ signals covered by the ’730 patent.”
 Id. The court then credited Dr. Chizeck’s testimony iden-
 tifying “500 Hz as the upper limit of slow-varying signals
 covered by Yollin.” Id. at *9–10.
     The district court rejected Genuine’s argument that
 Mr. Nguyen had only distinguished Yollin on the grounds
 that its signals were slow-varying rather than fast-varying,
 and that Mr. Nguyen accordingly should only be deemed to
 have disclaimed slow-varying signals below the audio fre-
 quency spectrum. Id. at *9. The court cited Andersen Corp.
 v. Fiber Composites, LLC, 474 F.3d 1361, 1374 (Fed. Cir.
 2007), for the proposition that “an applicant’s argument
 that a prior art reference is distinguishable on a particular
 ground can serve as a disclaimer of claim scope even if the
 applicant distinguishes the reference on other grounds as
 well.” Id. “Accordingly,” the district court explained, “even
 though Mr. Nguyen distinguished Yollin on the basis that
 the ’730 patent addressed ‘audio or higher frequencies,’ this
 distinction does not negate his additional statements
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 10     GENUINE ENABLING TECHNOLOGY      v. NINTENDO CO., LTD.

 expressly disavowing as ‘slow-varying’ the range of fre-
 quencies addressed by Yollin.” Id. The court also stated
 that Genuine had not adequately rebutted Dr. Chizeck’s
 analysis and opinion regarding the 500 Hz threshold. Id.
 Based on its claim construction of “input signal,” the dis-
 trict court granted summary judgment of non-infringement
 in favor of Nintendo. Id. at *10–14.
    Genuine appealed.         We have jurisdiction under
 28 U.S.C. § 1295(a)(1).
                    STANDARD OF REVIEW
     We review a district court’s grant of summary judg-
 ment under the standard applied in the regional circuit, in
 this case the Ninth Circuit. Neville v. Found. Constructors,
 Inc., 972 F.3d 1350, 1355 (Fed. Cir. 2020). The Ninth Cir-
 cuit reviews a grant of summary judgment de novo. Id. (ci-
 tation omitted). Summary judgment is proper only when
 the court determines that “no reasonable jury could have
 found infringement on the undisputed facts or when all
 reasonable factual inferences are drawn in favor of the pa-
 tentee.” Netword, LLC v. Centraal Corp., 242 F.3d 1347,
 1353 (Fed. Cir. 2001) (first citing Fed. R. Civ. P. 56(c); and
 then citing Anderson v. Liberty Lobby, Inc., 477 U.S. 242,
 248 (1986)).
     We review a district court’s claim construction de novo
 and its underlying factual determinations for clear error.
 Teva Pharms. USA, Inc. v. Sandoz, Inc., 574 U.S. 318,
 326–27 (2015). We review the application of prosecution
 disclaimer de novo. Shire Dev., LLC v. Watson Pharms.,
 Inc., 787 F.3d 1359, 1365 (Fed. Cir. 2015).
                         DISCUSSION
                               I
                               A
     This court has long “emphasized the importance of the
 intrinsic evidence in claim construction” while also
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 GENUINE ENABLING TECHNOLOGY      v. NINTENDO CO., LTD.             11

 “authoriz[ing] district courts to rely on extrinsic evidence”
 in certain scenarios. Phillips v. AWH Corp., 415 F.3d 1303,
 1317 (Fed. Cir. 2005) (en banc). Extrinsic evidence, we
 have observed, is generally “less reliable” for claim con-
 struction purposes than the intrinsic record for several rea-
 sons. Id. at 1318. Extrinsic sources might not have been
 written for the purpose of illuminating the scope of the pa-
 tent at issue; they might have been written for an audience
 different from persons of ordinary skill in the art; they
 might suffer from litigation bias; and relatedly, they might
 have been selectively plucked from the unbounded uni-
 verse of potentially relevant material to advance a liti-
 gant’s position. Id. We have therefore cautioned against
 “undue reliance” on extrinsic evidence because it “poses the
 risk that it will be used to change the meaning of claims in
 derogation of the indisputable public records consisting of
 the claims, the specification and the prosecution history,
 thereby undermining the public notice function of patents.”
 Id. at 1319 (citation and quotation marks omitted). In
 other words, “[e]xtrinsic evidence is to be used for the
 court’s understanding of the patent, not for the purpose of
 varying or contradicting the terms of the claims.” Mark-
 man v. Westview Instruments, Inc., 52 F.3d 967, 981 (Fed.
 Cir. 1995), aff’d, 517 U.S. 370 (1996).
      Expert testimony, one type of extrinsic evidence, may
 be useful in claim construction “to provide background on
 the technology at issue, to explain how an invention works,
 to ensure that the court’s understanding of the technical
 aspects of the patent is consistent with that of a person of
 skill in the art, or to establish that a particular term in the
 patent or the prior art has a particular meaning in the per-
 tinent field.” Phillips, 415 F.3d at 1318 (citations omitted).
 However, expert testimony may not be used to diverge sig-
 nificantly from the intrinsic record. See, e.g., id. (“[A] court
 should discount any expert testimony that is clearly at odds
 with the claim construction mandated by the claims them-
 selves, the written description, and the prosecution history,
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 12      GENUINE ENABLING TECHNOLOGY      v. NINTENDO CO., LTD.

 in other words, with the written record of the patent.” (ci-
 tation and quotation marks omitted)); see also Vitronics
 Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1584 (Fed. Cir.
 1996) (“[E]xpert testimony . . . may not be used to vary or
 contradict the claim language. Nor may it contradict the
 import of other parts of the specification.” (citation omit-
 ted)); Aqua-Aerobic Sys., Inc. v. Aerators Inc., 211 F.3d
 1241, 1245 (Fed. Cir. 2000) (stating that expert testimony
 “may not correct errors or erase limitations or otherwise
 diverge from the description of the invention as contained
 in the patent documents”); Omega Eng’g, Inc, v. Raytek
 Corp., 334 F.3d 1314, 1332 (Fed. Cir. 2003) (“Yet, Omega
 submits its expert declarations not to shed light on this
 field of art, but to rewrite the patent’s specification and ex-
 plicitly provide for the laser splitting device, lenses, and
 prisms to strike the center of the energy zone. That we
 cannot accept.”); U.S. Indus. Chems. v. Carbide & Carbon
 Chems. Corp., 315 U.S. 668, 678 (1942) (“It is inadmissible
 to enlarge the scope of the original patent by recourse to
 expert testimony to the effect that a process described and
 claimed in the reissue, different from that described and
 claimed in the original patent, is, because equally effica-
 cious, in substance that claimed originally.”).
     Accordingly, the intrinsic record “must be considered
 and where clear must be followed.” See Mantech Env’t
 Corp. v. Hudson Env’t Servs., Inc., 152 F.3d 1368, 1373
 (Fed. Cir. 1998); see also Vitronics, 90 F.3d at 1584
 (“[W]here the patent documents are unambiguous, expert
 testimony regarding the meaning of a claim is entitled to
 no weight.”). “Any other rule would be unfair to competi-
 tors who must be able to rely on the patent documents
 themselves, without consideration of expert opinion that
 then does not even exist, in ascertaining the scope of a pa-
 tentee’s right to exclude.” Vitronics, 90 F.3d at 1584. Reli-
 ance on expert testimony regarding the claim
 interpretation is thus permissible where the testimony is
 “consistent with [the interpretation] required by the
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 GENUINE ENABLING TECHNOLOGY       v. NINTENDO CO., LTD.         13

 intrinsic evidence.” Goldenberg v. Cytogen, Inc., 373 F.3d
 1158, 1166 (Fed. Cir. 2004).
                              B
      The doctrine of prosecution disclaimer “preclud[es] pa-
 tentees from recapturing through claim interpretation spe-
 cific meanings disclaimed during prosecution.” Omega,
 334 F.3d at 1323. “As a basic principle of claim interpreta-
 tion, prosecution disclaimer promotes the public notice
 function of the intrinsic evidence and protects the public’s
 reliance on definitive statements made during prosecu-
 tion.” Id. at 1324. For a statement during prosecution to
 qualify as a disavowal of claim scope, it must be “so clear
 as to show reasonable clarity and deliberateness,” and “so
 unmistakable as to be unambiguous evidence of dis-
 claimer.” Id. at 1325 (citations omitted); see also Tech.
 Props. Ltd. LLC v. Huawei Techs. Co., 849 F.3d 1349, 1358
 (Fed. Cir. 2017) (“The patentee’s disclaimer may not have
 been necessary, but its statements made to overcome
 Magar were clear and unmistakable.”). If the challenged
 statements are ambiguous or amenable to multiple reason-
 able interpretations, prosecution disclaimer is not estab-
 lished. See Tech. Props., 849 F.3d at 1358 (citing Mass.
 Inst. of Tech. v. Shire Pharms., Inc., 839 F.3d 1111, 1119
 (Fed. Cir. 2016)). “The party seeking to invoke prosecution
 history disclaimer bears the burden of proving the exist-
 ence of a clear and unmistakable disclaimer that would
 have been evident to one skilled in the art.” Shire, 839 F.3d
 at 1119 (citation and quotation marks omitted).
                              II
     The parties agree that Mr. Nguyen disavowed claim
 scope during prosecution of the ’730 patent in distinguish-
 ing his claimed inventions from the Yollin reference. Ap-
 pellant’s Br. 34; Appellee’s Br. 26. The parties dispute
 whether he disavowed claim scope beyond signals below
 the audio frequency spectrum.
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 14     GENUINE ENABLING TECHNOLOGY     v. NINTENDO CO., LTD.

      Genuine contends that the prosecution history clearly
 shows that Mr. Nguyen disclaimed “slow-varying” signals
 from the full scope of the term “input signal.” Appel-
 lant’s Br. 35. According to Genuine, Mr. Nguyen estab-
 lished a clear demarcation between Yollin’s low-frequency
 signals and the signals “of audio or higher frequency” used
 in his inventions. Id. Genuine further argues that the dis-
 trict court erred by finding disavowal of additional claim
 scope where the record shows no such disavowal. Id. at 38.
 According to Genuine, neither the intrinsic record nor
 Yollin ever discussed signal frequency in a manner that
 would allow a person of ordinary skill in the art to draw
 any bright line in claim scope based on frequency, let alone
 a bright line at 500 Hz. Id. Genuine also contends that the
 district court erroneously relied on testimony by Nin-
 tendo’s expert, Dr. Chizeck, that a person of ordinary skill
 in the art would have understood Mr. Nguyen’s assertions
 as a disavowal of all signals of frequencies up to 500 Hz.
 Id. at 44. Genuine points out that Dr. Chizeck’s testimony
 had no support in the intrinsic record, but rather was based
 solely on other extrinsic evidence purporting to describe
 various signals’ frequency ranges. Id. at 44–45. We agree
 with Genuine.
      We conclude that the only disavowal of claim scope that
 is clear and unmistakable in the record before us is Mr.
 Nguyen’s disavowal of signals below the audio frequency
 spectrum. Omega, 334 F.3d at 1325–26 (prosecution his-
 tory disclaimer must be clear and unmistakable). Mr. Ngu-
 yen repeatedly distinguished his inventions from Yollin on
 the grounds that Yollin taught “slow-varying signals”
 whereas his inventions involved “audio or higher fre-
 quency” signals. See J.A. 1784–85. The examiner’s ac-
 ceptance of that distinction and resulting decision to allow
 the claims suggest that Mr. Nguyen and the examiner
 reached an understanding on that point. To the extent Mr.
 Nguyen’s statements may implicate other claim scope—
 such as signals of frequency up to 500 Hz—the record does
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 GENUINE ENABLING TECHNOLOGY      v. NINTENDO CO., LTD.             15

 not rise to the level of establishing a “clear and unmistak-
 able” disavowal. Tech. Props., 849 F.3d at 1358 (disclaimer
 is not established where statements are ambiguous or ame-
 nable to multiple reasonable interpretations).
      Regarding the 500 Hz threshold, the district court
 erred by relying on expert testimony to limit the claim
 scope in a manner not contemplated by the intrinsic record.
 The district court credited Dr. Chizeck’s testimony that the
 signals disclosed in Yollin would have had frequencies up
 to 500 Hz. Genuine, 2020 WL 4366163, at *9 (“Based on
 Dr. Chizeck’s testimony, which identifies 500 Hz as the up-
 per limit of slow-varying signals covered by Yollin, Nin-
 tendo proposes that the Court construe ‘input signal’ as
 frequencies greater than 500 Hz.”). As Genuine points out,
 the 500 Hz frequency threshold has no basis anywhere in
 the intrinsic record; instead, Dr. Chizeck divines that
 threshold from another extrinsic reference he calls “Yuce
 et al.” The district court, however, did not assess the Yuce
 reference in its decision. Neither a full citation for that ref-
 erence nor the reference itself appears in the record before
 us. Nintendo does not make any mention of that reference,
 let alone attempt to defend its soundness as a basis for Dr.
 Chizeck’s testimony. We are left, therefore, with the con-
 clusion that the district court relied on extrinsic evidence
 upon extrinsic evidence to draw a bright line in claim scope
 not suggested anywhere in the intrinsic record. Such evi-
 dence cannot properly overcome the clarity with which Mr.
 Nguyen only disavowed signals below the audio frequency
 spectrum. Mantech, 152 F.3d at 1373; Vitronics, 90 F.3d at
 1584; Goldenberg, 373 F.3d at 1166.
     In view of our conclusion above that Mr. Nguyen only
 disavowed signals below the audio spectrum, the district
 court also erred to the extent it found that Mr. Nguyen dis-
 avowed signals based on their content or nature—namely,
 “signals generated from positional change information,
 user selection information, physiological response infor-
 mation, and other slow-varying information.” Genuine,
Case: 20-2167     Document: 40    Page: 16    Filed: 04/01/2022

 16     GENUINE ENABLING TECHNOLOGY      v. NINTENDO CO., LTD.

 2020 WL 4366163, at *10–11. Mr. Nguyen’s assertions dis-
 tinguishing his inventions from Yollin do not clearly and
 unmistakably demonstrate any such disclaimer. The ex-
 aminer cited Yollin’s teaching of “input information re-
 ceived from motion translation unit 102, user selection unit
 104 and physiological response sensor(s) 106” as disclosing
 the “input signal” limitation. J.A. 1768 (citing Yollin at
 col. 5 ll. 16–18). In response, Mr. Nguyen distinguished
 that teaching on the ground that those signals fell below
 the audio spectrum. See J.A. 1784–85. The record does not
 support finding a separate and distinct disclaimer of claim
 scope relating to the particular type or content of signal.
 Omega, 334 F.3d at 1325–26; Tech. Props., 849 F.3d at
 1357–58.
     For the above reasons, we conclude that the district
 court erred in construing “input signal,” and we construe
 that term to mean “a signal having an audio or higher fre-
 quency.”
                        CONCLUSION
      We hold that the district court erred in construing the
 term “input signal.” In particular, the district court erred
 in finding that Mr. Nguyen disclaimed subject matter other
 than signals below the audio frequency spectrum during
 prosecution, and it further erred in relying on extrinsic ev-
 idence to limit the claim scope to signals above 500 Hz. We
 therefore conclude that the proper construction of “input
 signal” is “a signal having an audio or higher frequency.”
 Accordingly, we reverse the district court’s grant of sum-
 mary judgment of non-infringement and remand for fur-
 ther proceedings consistent with this opinion.

                REVERSED AND REMANDED
                            COSTS
 No costs.