BRYSON, Circuit Judge. Samsung Electronics America, Inc., appeals from a de- cision of the Patent Trial and Appeal Board in an inter partes review proceeding. Samsung petitioned the Board to rule that certain claims of U.S. Patent No. 8,650,591 (“the ’591 patent”), owned by cross-appellant Prisua Engi- neering Corp. (“Prisua”), were unpatentable. At the con- clusion of the proceeding, the Board held that claim 11 of the ’591 patent was unpatentable based on obviousness. However, the Board declined to analyze whether claims 1– 4 and 8 were unpatentable as anticipated or obvious, be- cause it concluded that those claims were indefinite. On appeal, Samsung contends that the Board should have canceled claims 1–4 and 8 for indefiniteness. In the alternative, Samsung argues that even if the Board was not statutorily authorized to cancel those claims for indefi- niteness, it should have assessed whether they would have been anticipated or obvious in view of the cited prior art. Prisua cross-appeals from the Board’s ruling that claim 11 was unpatentable for obviousness. We affirm in part, re- verse in part, and remand. I A Congress has long permitted parties accused of patent infringement in federal court to challenge the validity of the asserted patent claims on any ground specified in part II of the Patent Act as a condition for patentability and for failure to comply with any requirement of 35 U.S.C. § 112. See 35 U.S.C. § 282(b)(2)–(3). Over the last few decades, Congress has supplemented federal court litigation by cre- ating several administrative processes that authorize the Patent and Trademark Office (“PTO”) to reconsider and cancel wrongly issued claims in some circumstances. In 1980, Congress established a regime known as “ex parte reexamination.” See Act to Amend the Patent and

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SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING 3 CORP. Trademark Laws, Pub. L. No. 96-517, 94 Stat. 3015 (1980), codified at 35 U.S.C. § 301 et seq. Ex parte reexamination gives “[a]ny person at any time” the right to “file a request for reexamination” based on certain prior art “bearing on the patentability” of an already-issued patent. 35 U.S.C. §§ 301(a)(1), 302. After institution, an ex parte reexamina- tion follows essentially the same back and forth process be- tween the patent owner and the examiner as in the initial PTO examination. 35 U.S.C. § 305. Congress subsequently created a procedure known as “inter partes reexamination.” See Optional Inter Partes Reexamination Procedure Act of 1999, Pub. L. No. 106-113, 113 Stat. 1501A-567, codified at 35 U.S.C. § 311 et seq. (2006 ed.) (superseded). Inter partes reexamination gave third parties greater opportunities to participate in the reexamination process, but otherwise proceeded much like an ex parte reexamination. The Leahy-Smith America Invents Act (“AIA”), Pub. L. No. 112-29, 125 Stat. 284 (2011), replaced inter partes reexamination with “inter partes review,” the procedure at issue in this case. See 35 U.S.C. §§ 311–19. Inter partes review, commonly referred to as IPR, provides patent chal- lengers with even broader rights to participate in the pro- cess of re-evaluating patents, but it also sets limits on the process. A petition for inter partes review, for example, can request cancellation of claims “only on a ground that could be raised under section 102 or 103 [of the Patent Act] and only on the basis of prior art consisting of patents or printed publications.” 35 U.S.C. § 311(b). The AIA also created another administrative process called “post-grant review.” See 35 U.S.C. §§ 321–29. Un- like a petition for inter partes review, a petition for post- grant review can request cancellation of patent claims “on any ground that could be raised under paragraph (2) or (3) of section 282(b) [of the Patent Act] (relating to invalidity of the patent or any claim),” the same invalidity defenses Case: 19-1169 Document: 52 Page: 4 Filed: 02/04/2020 4 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING CORP. long available to defendants accused of patent infringe- ment in federal district court. 35 U.S.C. § 321(b). Although a petition for inter partes review is limited to a narrow set of grounds, it can be requested at any time during a patent’s enforceability period, with certain re- strictions. 35 U.S.C. §§ 311(c), 315(b). By contrast, the broad range of grounds that may be raised in a post-grant review petition are available only for a limited time after the patent is issued. 35 U.S.C. § 321(c). B In 2010, Dr. Yolanda Prieto applied for a patent aimed at providing a “new and unique form of enhancing” a user’s multimedia entertainment experience. ’591 patent, Ab- stract. The PTO granted the application in 2014. The is- sued patent, entitled “Video Enabled Digital Devices for Embedding User Data in Interactive Applications,” is di- rected to “generating an edited video data stream from an original video stream” by “substituting at least one object . . . in said original video stream by at least a different ob- ject.” ’591 patent, col. 1, ll. 43–47. Figure 3 illustrates the operation of the video image substitution according to one embodiment: Case: 19-1169 Document: 52 Page: 5 Filed: 02/04/2020 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING 5 CORP. As illustrated, a user can insert a selected image, such as a face of the user’s choosing, in place of the face of the figure in the original video. Id. at col. ^[3], line 66, through col. 4, line 2. Case: 19-1169 Document: 52 Page: 6 Filed: 02/04/2020 6 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING CORP. Claims 1–4, 8, and 11 of the ’591 patent are at issue in this appeal. The claims are directed to methods and appa- ratuses for “generating a displayable edited video data stream from an original video data stream.” ’591 patent, col. ^[7], ll. 14–16; id. at col. 8, ll. 28–29. Independent claim 1 reads in full as follows: 1. An interactive media apparatus for generat- ing a displayable edited video data stream from an original video data stream, wherein at least one pixel in a frame of said original video data stream is digitally extracted to form a first image, said first image then replaced by a second image resulting from a digital extraction of at least one pixel in a frame of a user input video data stream, said appa- ratus comprising: an image capture device capturing the user input video data stream; an image display device displaying the original video stream; a data entry device, operably coupled with the im- age capture device and the image display device, operated by a user to select the at least one pixel in the frame of the user input video data stream to use as the second image, and further operated by the user to select the at least one pixel to use as the first image; wherein said data entry device is selected from a group of devices consisting of: a keyboard, a dis- play, a wireless communication capability device, and an external memory device; a digital processing unit operably coupled with the data entry device, said digital processing unit per- forming: Case: 19-1169 Document: 52 Page: 7 Filed: 02/04/2020 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING 7 CORP. identifying the selected at least one pixel in the frame of the user input video data stream; extracting the identified at least one pixel as the second image; storing the second image in a memory device oper- ably coupled with the interactive media apparatus; receiving a selection of the first image from the original video data stream; extracting the first image; spatially matching an area of the second image to an area of the first image in the original video data stream, wherein spatially matching the areas re- sults in equal spatial lengths and widths between said two spatially matched areas; and performing a substitution of the spatially matched first image with the spatially matched second im- age to generate the displayable edited video data stream from the original video data stream. ’591 patent, cl. 1. Claims 2–4 and 8 depend from claim 1 and add several limitations that are not pertinent to the resolution of this appeal. Independent claim 11 is a method claim that tracks the limitations of apparatus claim 1, with some minor differences. In particular, claim 11 does not have a limitation corresponding to claim 1’s requirement of “an image display device displaying the original video stream.” Id. On the other hand, claim 11 adds limitations that require the computation of “motion vectors associated with the first image” and the application of those motion vectors “to the second image, wherein the generated dis- playable edited video data stream resulting from the sub- stitution maintains an overall motion of the original video data stream.” Id. Case: 19-1169 Document: 52 Page: 8 Filed: 02/04/2020 8 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING CORP. C After the ’591 patent issued, Dr. Prieto formed Prisua to commercialize the invention claimed in the patent. In 2016, Prisua sued Samsung Electronics America, Inc., and several other Samsung entities for patent infringement. Prisua alleged that the “Best Face” feature on several Sam- sung devices, including cell phones, infringed claims 1, 3, 4, and 8 of the ’591 patent. The “Best Face” feature, ac- cording to Prisua, allowed the accused devices to capture a burst of images and then replace unwanted facial images, such as images captured when someone was blinking, with better images from other frames in the same burst. 1 After being sued, Samsung petitioned for inter partes review of claims 1–4, 8, and 11 of the ’591 patent on four separate grounds. The Board initially determined that it would review only whether a U.S. patent application pub- lication known as Sitrick rendered claim 11 obvious. The Board declined to institute review of claims 1–4 and 8 on any ground, because it concluded that it could not deter- mine the scope of those claims. The Board concluded that there were two impediments to determining the scope of claim 1. First, the Board found that it was “unclear whether claim 1 covers, for example, an apparatus that includes a data entry device capable of being operated by a user to select the at least one pixel, or covers only the user actually operating the data entry de- vice to select the at least one pixel.” Samsung Elecs. Am., Inc. v. Prisua Eng’g Corp., No. IPR2017-01188, 2017 WL 1 After a trial in the United States District Court for the Southern District of Florida, the jury found that Sam- sung willfully infringed the asserted claims and awarded Prisua $4.3 million in damages. That action has been stayed pending this proceeding; the verdict in that case is not at issue in this appeal. Case: 19-1169 Document: 52 Page: 9 Filed: 02/04/2020 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING 9 CORP. 4570373, at *5 (P.T.A.B. Oct. 11, 2017) (“Institution Deci- sion”) (emphasis in original). For that reason, the Board concluded that claim 1 was indefinite under this court’s de- cision in IPXL Holdings, LLC v. Amazon.com, Inc., 430 F.3d 1377, 1384 (Fed. Cir. 2005). Institution Decision, 2017 WL 4570373, at *5-6. The Board also concluded that the “digital processing unit” limitation in claim 1 “invoke[d] § 112, sixth paragraph” and that the petition failed to iden- tify any corresponding structure, as required by section 112 and the pertinent PTO regulation, 37 C.F.R. § 42.104(b)(3). Institution Decision, 2017 WL 4570373 at *6 (citing Wil- liamson v. Citrix Online, LLC, 792 F.3d 1339, 1348 (Fed. Cir. 2015) (en banc)). The Board found that claims 2–4 and 8, which depend from claim 1, were indefinite for the same reasons. Because the Board determined that it was unable to construe claim 1 or dependent claims 2–4 and 8, it con- cluded that the petitioner had not “established a reasona- ble likelihood of prevailing in showing that claims 1–4, and 8 are unpatentable under any of the asserted grounds.” Id. As the IPR briefing was drawing to a close, the Su- preme Court decided SAS Institute, Inc. v. Iancu, 138 S. Ct. 1348 (2018), in which the Court held that when the Board institutes an IPR, it may not pick and choose which claims it will address, but must address the patentability of every claim challenged by the petitioner. Accordingly, the Board modified its institution decision to include all the chal- lenged claims and all the grounds presented in the petition. The Board also allowed the parties to file supplemental briefs and evidence, but only to address the newly added claims and grounds. In its supplemental briefing, Prisua stated that it did not agree with the Board’s indefiniteness determinations. Despite that, Prisua argued that because Samsung had failed to prove the claims were definite, the Board should not apply the prior art to the claims. Prisua also contended that the Board did not have the statutory authority to can- cel claims for indefiniteness during an IPR. Case: 19-1169 Document: 52 Page: 10 Filed: 02/04/2020 10 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING CORP. In response, Samsung urged the Board to cancel claims 1–4 and 8 based on the Board’s determination that those claims were indefinite under this court’s analysis in IPXL. In the alternative, Samsung argued that even if the Board could not cancel the claims for indefiniteness, it could still apply the prior art to the claims despite the IPXL issue. In support of that contention, Samsung argued that because the uncertainty regarding claim scope resulted from the combination of two statutory classes of invention, a manu- facturer or seller of the claimed device would not know when infringement occurred. But that, according to Sam- sung, would not pose an obstacle to determining whether those claims could be measured against the prior art. Sam- sung also argued that the term “digital processing unit” constituted a sufficient recitation of structure and did not invoke means-plus-function analysis under 35 U.S.C. § 112 ¶ 6. In its final written decision, the Board repeated its con- clusion that claims 1–4 and 8 were indefinite under IPXL. Samsung Elecs. Am., Inc. v. Prisua Eng’g Corp., No. IPR2017-01188, 2018 WL 5274000, at *7–8 (P.T.A.B. Oct. ^[2], 2018) (“Final Written Decision”). In addition, the Board again held that claim 1 and its dependent claims invoked section 112, paragraph 6, for the “digital processing unit” element, and that because there was no corresponding structure in the specification, the Board could not apply the prior art to the claims. Id. at *9. The Board therefore held that Samsung had not established that claims 1–4 and 8 were unpatentable under any of the asserted grounds. Id. With respect to claim 11, the Board analyzed whether that claim would have been obvious in view of Sitrick, the sole originally instituted ground of review. After reviewing various record materials, including competing expert testi- mony, the Board found that all of the limitations of claim 11 would have been obvious in light of Sitrick, including the “digital processing unit” limitation. Id. at[*11] -19. The Board therefore held claim 11 to be unpatentable. Case: 19-1169 Document: 52 Page: 11 Filed: 02/04/2020 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING 11 CORP. II On appeal, Samsung challenges the Board’s decision not to cancel the claims it found indefinite. In the alterna- tive, Samsung contends that the Board should have ap- plied the cited prior art to those claims. A We reject Samsung’s contention that the IPR statute authorizes the Board to cancel challenged claims for indef- initeness. In Cuozzo Speed Techs., LLC v. Lee, the Su- preme Court said the Patent Office would be acting “outside its statutory limits” by “canceling a patent claim for ‘indefiniteness under § 112’ in inter partes review.” 136 S. Ct. 2131, 2141–42 (2016). This court subsequently ech- oed that view, stating—albeit in a non-precedential opin- ion—that “[i]n an IPR, the Board cannot declare claims indefinite.” Google LLC v. Network-1 Techs., Inc., 726 F. App’x 779, 782 n.3 (Fed. Cir. 2018) (citing 35 U.S.C. § 311(b)); see also Neptune Generics, LLC v. Eli Lilly & Co., 921 F.3d 1372, 1378 (Fed Cir. 2019) (holding that the Board is not authorized to address challenges to patent eligibility under 35 U.S.C. §101 in an IPR proceeding: “Congress ex- pressly limited the scope of inter parties review to a subset of grounds that can be raised under 35 U.S.C. §§ 102 & 103.”). Samsung asks us to reject those statements as dicta and to hold that even though the Board may not institute inter partes review based on a claim’s indefiniteness, it may cancel such a claim on indefiniteness grounds once it has instituted review on statutorily authorized grounds. We are not persuaded by Samsung’s arguments; we hold that the Board may not cancel claims for indefiniteness in an IPR proceeding. The statutory provisions governing the inter partes re- view process do not permit the Board to institute inter partes review of claims for indefiniteness. Section 311(b), Case: 19-1169 Document: 52 Page: 12 Filed: 02/04/2020 12 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING CORP. entitled “Scope,” states that “[a] petitioner in an inter partes review may request to cancel as unpatentable 1 or more claims of a patent only on a ground that could be raised under section 102 or 103 and only on the basis of prior art consisting of patents or printed publications.” 35 U.S.C. § 311(b). Samsung, the petitioner in the IPR pro- ceeding below, was thus not permitted to request that the Board cancel claims 1–4 and 8 on the ground that they were indefinite. Nor could the Board cancel those claims as indefinite on its own accord. As the Supreme Court explained in SAS, Congress “chose to structure a process in which it’s the pe- titioner, not the Director, who gets to define the contours” of an IPR proceeding. 138 S. Ct. at 1355. “[T]he statute envisions that a petitioner will seek an inter partes review of a particular kind—one guided by a petition describing ‘each claim challenged’ and ‘the grounds on which the chal- lenge to each claim is based.’” Id. (quoting 35 U.S.C. § 312(a)(3)). After analyzing the IPR statute and its prede- cessors, the Supreme Court concluded that it was clear that “the petitioner’s contentions, not the Director’s discretion, define the scope of the litigation all the way from institu- tion through to conclusion.” Id. at 1357. The petition, that is, defines the scope of an IPR proceeding, and nothing in the IPR statute permits the Board to expand that scope in its final written decision.

Notwithstanding the foregoing authority, Samsung points to several provisions in the IPR statute in an effort to show that Congress authorized the Board to cancel claims for indefiniteness after an IPR has been instituted. None of those provisions, however, supports Samsung’s ar- gument. First, while section 311(b) limits the scope of an IPR petition to certain grounds that could be raised under sec- tions 102 and 103, Samsung argues that section 318(a),

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SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING 13 CORP. which relates to the Board’s final written decision, is not so limited. Section 318(a) directs the Board to “issue a final written decision with respect to the patentability of any pa- tent claim challenged by the petitioner and any new claim added under section 316(d).” 35 U.S.C. § 318(a). Samsung contends that the word “patentability” in section 318(a) is broader than the phrase “a ground that could be raised un- der section 102 or 103” in section 311(b). The difference, according to Samsung, indicates that the permissible scope of the Board’s final written decision is broader than the permissible scope of the petition and the institution deci- sion. The problem with that argument is that it divorces the final written decision provision, section 318(a), from the rest of the inter partes review statute. Section 311(b) says that a petitioner may ask the Board “to cancel [challenged claims] as unpatentable” on certain 102 and 103 grounds. In context, it is clear that section 318(a)’s directive to the Board to issue a final written decision on the “patentabil- ity” of a challenged claim refers back to the grounds on which, under section 311(b), the petitioner may request the Board to “cancel as unpatentable” claims of the challenged patent, i.e., the designated section 102 and 103 grounds. ^[2] Second, Samsung notes that the word “patentability” in section 318(a) modifies both “challenged” claims and “new” claims that are proposed during the inter partes pro- ceeding. For that reason, Samsung suggests, the scope of the Board’s review must be the same for both. And because We also do not agree with Samsung’s contention that the Board’s inherent authority to perform claim construc- tion during an inter partes review means that the Board can cancel the claims as indefinite. Although “indefinite- ness analysis involves general claim construction princi- ples,” Sonix Tech. Co. v. Publications Int’l, Ltd., 844 F.3d 1370, 1378 (Fed. Cir. 2017), it does not follow that the Board may exceed its statutorily limited authority simply

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16 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING CORP. because an indefiniteness issue arises during claim con- struction. Instead, as discussed above, Congress viewed a challenge based on indefiniteness to be distinct from a chal- lenge based on sections 102 and 103. As such, the proper course for the Board to follow, if it cannot ascertain the scope of a claim with reasonable certainty for purposes of assessing patentability, is to decline to institute the IPR or, if the indefiniteness issue affects only certain claims, to conclude that it could not reach a decision on the merits with respect to whether petitioner had established the un- patentability of those claims under sections 102 or103. 3 It would not be proper for the Board to cancel claims on a ground that is unavailable in an IPR.

In essence, Samsung’s argument is that there is no limit to the Board’s authority to make unpatentability de- terminations at the conclusion of an IPR proceeding. That position is at odds with both the statutory language and the case law, and we reject it. B Having rejected Samsung’s argument that the Board may cancel challenged claims for indefiniteness during an IPR, we next address Samsung’s secondary argument that the Board should have assessed the patentability of claims 1 and 4–8 under sections 102 or 103. As noted, even though neither party raised the issue of indefiniteness below, the Board raised two indefiniteness We agree with Samsung that the term “digital pro- cessing unit” is not a “means-plus-function” limitation sub- ject to analysis under section 112, paragraph 6. Because the reference to the digital processing unit does not contain the words “means for,” there is a rebuttable presumption that section 112, paragraph 6, does not apply to that limi- tation. Williamson, 792 F.3d at 1348. That presumption can be overcome, but only “if the challenger demonstrates that the claim term fails to ‘recite sufficiently definite structure’ or else recites ‘function without reciting suffi- cient structure for performing that function.’” Id. at 1349. The question whether the term “digital processing unit” invokes section 112, paragraph 6, depends on whether persons skilled in the art would understand the claim language to refer to structure, assessed in light of the presumption that flows from the drafter’s choice not to em- ploy the word “means.” The Board pointed to no evidence that a person skilled in the relevant art would regard the term “digital processing unit” as purely functional. In fact, Prisua argued to the Board, based on testimony from its expert (the inventor), that the digital processing unit

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18 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING CORP. recited in the claims is “an image processing device that people in the art are generally familiar with.” J.A. 896. As used in the claims of the ’591 patent, the term “dig- ital processing unit” clearly serves as a stand-in for a “gen- eral purpose computer” or a “central processing unit,” each of which would be understood as a reference to structure in this case, not simply any device that can perform a partic- ular function. See, e.g., LG Elecs., Inc. v. Bizcom Elecs., Inc., 453 F.3d 1364, 1372 (Fed. Cir. 2006), rev’d on other grounds, Quanta Computer, Inc. v. LG Elecs., Inc., 553 U.S. 617 (2008); Inventio AG v. ThyssenKrupp Elevator Ams. Corp., 649 F.3d 1350, 1359 (Fed. Cir. 2011). Significantly, that is what the Board found with re- spect to the use of the term “digital processing unit” in claim 11. Final Written Decision, 2018 WL 5274000, at[*14] (“As a result, we are not persuaded by Patent Owner’s con- tention that ‘digital processing unit’ has a narrower defini- tion than CPU. Sitrick discloses a general purpose computer with a CPU that is capable of performing all of the functions recited in claim 11. As a result, we are per- suaded that Sitrick’s CPU teaches the recited ‘digital pro- cessing unit.’”). Moreover, claim 1 requires that the “digital processing unit” be operably connected to a “data entry device” such as a keyboard, which in turn is con- nected to other components. That portion of claim 1 con- stitutes further evidence of the structural nature of the term “digital processing unit,” as used in the claim. The Board did not treat claim 11’s “digital processing unit” as simply a black box recitation of any structure ca- pable of providing certain functions. Instead, the Board equated the term to a class of known structures—central processing units—that could be found in any general-pur- pose computer. See Final Written Decision, 2018 WL 5274000, at[*14] . The Board’s treatment of the “digital pro- cessing unit” limitation in claim 11 as structural in nature undermines its conclusion that the same term in claim 1 Case: 19-1169 Document: 52 Page: 19 Filed: 02/04/2020 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING 19 CORP. was functional and thus subject to analysis under section 112, paragraph 6. Given the Board’s findings with respect to claim 11, the context of the term in the claim at issue, and the presump- tion arising from the patentee’s failure to use the “means for” formulation, unrebutted by any evidence before the Board, we conclude that the Board erred in ruling that the term “digital processing unit” does not recite structure and instead is a purely functional term. We therefore reject the Board’s conclusion that the term “digital processing unit,” as used in claim 1, invoked means-plus-function claiming, and that for that reason claims 1 and 4–8 cannot be ana- lyzed for anticipation or obviousness. 4 The Board also concluded that claim 1 was indefinite because of an IPXL issue—a finding that neither party dis- putes. However, the Board did not address Samsung’s ar- gument that the Board could nonetheless apply the prior art to claim 1 and its dependent claims for purposes of an- ticipation or obviousness analysis. In light of our decision to reverse the Board’s decision as to the “digital processing unit” term, we believe the Board ended its analysis with respect to the IPXL issue prematurely. We therefore re- mand for further consideration of that issue.

4 Pointing to the Board’s reference to 37 C.F.R. § 42.104(b)(3), Prisua argues that Samsung’s petition failed to present a proper claim construction for claim 1, and that the Board’s decision is supportable on that ground. The Board, however, referred to the regulation only “if one were to contend that claim 1 is an apparatus claim whose limitations are merely written in functional language.” Final Written Decision, 2018 WL 5274000, at *9. Samsung has not made such a contention, and we have rejected it. Case: 19-1169 Document: 52 Page: 20 Filed: 02/04/2020 20 SAMSUNG ELECTRONICS AMERICA v. PRISUA ENGINEERING CORP. On remand, the Board should address Samsung’s argu- ment that the Board may analyze the patentability of a claim even if that claim is indefinite under the reasoning of IPXL. The rationale of IPXL is that the claim conflates elements of both an apparatus and a method, rendering the claim indefinite for purposes of determining when infringe- ment occurs. But that merely says that the claim is subject to invalidation on the ground of indefiniteness. It does not speak to whether the claim is also invalid for obviousness, regardless of whether it is treated as being directed to an apparatus or a method. Even though the validity of the challenged claims may be subject to question for IPXL-type indefiniteness, that is simply another ground on which the claims might be chal- lenged in an appropriate forum (other than the Board). See Standard Oil Co. v. Am. Cyanamid Co., 774 F.2d 448, 453– 55 (Fed. Cir. 1985) (upholding decision that patent was in- valid for both indefiniteness and obviousness); In re Collier, 397 F.2d 1003, 1004–06 (CCPA 1968) (rejecting claim on grounds of indefiniteness and obviousness). It does not necessarily preclude the Board from addressing the patent- ability of the claims on section 102 and 103 grounds. In the remand proceedings, the Board should determine whether claim 1 and its dependent claims are unpatentable as an- ticipated or obvious based on the instituted grounds. ^[5]