Court Opinion

ID: 4522728
Source: CourtListenerOpinion
Date Created: 2020-04-06 15:00:37.210892+00
Date Added: 2024-06-11T12:07:11.468552
License: Public Domain

Case: 19-1343       Document: 43           Page: 1       Filed: 04/06/2020

        NOTE: This disposition is nonprecedential.

   United States Court of Appeals
       for the Federal Circuit
                      ______________________

            PROMOS TECHNOLOGIES, INC.,
                     Appellant

                                     v.

         SAMSUNG ELECTRONICS CO., LTD.,
                     Appellee
              ______________________

                            2019-1343
                      ______________________

     Appeal from the United States Patent and Trademark
 Office, Patent Trial and Appeal Board in No. IPR2017-
 01412.

      -----------------------------------------------------------------

            PROMOS TECHNOLOGIES, INC.,
                     Appellant

                                     v.

         SAMSUNG ELECTRONICS CO., LTD.,
                     Appellee
              ______________________

                            2019-1344
                      ______________________
Case: 19-1343        Document: 43     Page: 2    Filed: 04/06/2020

2                 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

     Appeal from the United States Patent and Trademark
 Office, Patent Trial and Appeal Board in No. IPR2017-
 01413.
                  ______________________

                      Decided: April 6, 2020
                      ______________________

     KEVIN CHRISTOPHER JONES, TechKnowledge Law
 Group LLP, Redwood City, CA, argued for appellant. Also
 represented by CRAIG R. KAUFMAN.

    NAVEEN MODI, Paul Hastings LLP, Washington, DC,
 argued for appellee. Also represented by CHETAN BANSAL,
 STEPHEN BLAKE KINNAIRD, JOSEPH PALYS.
                  ______________________

    Before O’MALLEY, REYNA, and WALLACH, Circuit Judges.
    Opinion for the court filed by Circuit Judge O’MALLEY.
          Dissenting opinion filed by Circuit Judge REYNA.
 O’MALLEY, Circuit Judge.
     In two inter partes review proceedings requested by
 Samsung Electronics Co. (“Samsung”), the U.S. Patent
 Trial and Appeal Board (“the Board”) invalidated all chal-
 lenged claims of U.S. Patent No. 6,069,507 (the “’507 pa-
 tent”), which is assigned to ProMOS Technologies, Inc.
 (“ProMOS”). J.A. 3; J.A.II. 3. 1 The Board found the chal-
 lenged claims unpatentable as anticipated and obvious.

      1   This opinion primarily cites to the briefing and ap-
 pendix from the -1343 appeal because the briefing and ap-
 pendices for the two appeals are substantially identical on
 the claim construction issue. Any citations to the -1344
 briefing and appendices will use the modifier “II,” e.g.,
 “J.A.II.,” “Appellant Br. II,” “Appellee Br. II”
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.              3

 ProMOS appeals the Board’s final written decisions, argu-
 ing that the Board’s invalidity findings are erroneous be-
 cause its construction of the “maintaining” limitation is
 erroneous. Because we agree with the Board’s construc-
 tion, we affirm the Board’s decisions.
                       I. BACKGROUND
                      A. The Technology
    A clock signal is a type of periodic signal that oscillates
 between low and high voltages, and is often used to coordi-
 nate or synchronize different parts of a circuit. J.A. 227.
 The most common type of clock signal is in the form of a
 square wave, usually with a fixed, constant frequency:

 J.A. 227. The period (or cycle) of a clock signal is the dura-
 tion between one LOW-to-HIGH transition, also called a
 “rising edge,” and the next LOW-to-HIGH transition.
 J.A. 227. The HIGH-to-LOW transition is similarly called
 a “falling edge.” One period of a clock signal spans a 360˚
 phase. J.A. 228. When the rising and falling edges of two
 clock signals do not occur at the same time, the two signals
 are not “phase-aligned.” J.A. 228. This difference is known
 as a “phase difference.”
      One challenge associated with digital circuits is “clock
 skew”—that is, when a clock signal originating from a
 given source arrives at different components in a circuit at
 different times. J.A. 229–30. Clock skew may be caused
 by a variety of spatial or physical conditions, e.g., differing
 lengths of wire for conducting clock signals to respective
 components. J.A. 230. When circuit components have dif-
 ferent perceptions of timing due to clock skew, this may
 lead to undesirable circuit behavior. J.A. 230. For exam-
 ple, if two circuit components—which are designed to
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4               PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

 execute actions simultaneously—receive copies of a clock
 signal that are not phase-aligned due to clock skew, the ac-
 tions will occur sequentially.
     One way to address this issue is through a system
 known as a “delay locked loop” (“DLL”). A DLL, via a
 “phase detector,” determines how much of a phase differ-
 ence there is between two clock signals: a reference (or in-
 put) clock and an output (or feedback) clock. The DLL then
 employs a “voltage variable delay line” to delay the input
 data until it is synchronized with the reference clock.
                      B. The ’507 Patent
     The ’507 patent, entitled “Circuit and Method for Re-
 ducing Delay Line Length in Delay-Locked Loops,” relates
 to DLLs and “more particularly to reducing delay line
 length in DLLs.” ’507 patent, col. 1 ll. 12–13. Figure 1 of
 the patent provides an example of a “typical digital DLL”
 at the time of the invention.

     In this “typical digital DLL,” a phase detector 12 deter-
 mines if a phase difference exists between the buffered in-
 put and feedback clock signals, “CKI” and “CKF.” ’507
 patent, col. 1 ll. 19–33. If there is a nonzero phase differ-
 ence between the two signals, the system shifts the
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.            5

 buffered input clock signal by adjusting the shift register
 14 to select sufficient delay through delay line 16. ’507 pa-
 tent, col. 1 ll. 29–33. This added delay synchronizes the
 input and feedback clock signals. Id.
      Although DLLs can resolve the problems associated
 with clock skew, they generally require long delay lines to
 achieve sufficient coverage of frequency ranges and guar-
 antee desired resolution. ’507 patent, col. 1 ll. 16–18. This
 increased delay line length may demand larger silicon area
 requirements and higher power consumption. ’507 patent,
 col. 1 ll. 42–44. Increased delay line length may also cause
 other problems, such as a longer lock-in time and greater
 high frequency signal distortion. ’507 patent, col. 1 ll. 44–
 46.
     The ’507 patent proposes a “more elegant and cost ef-
 fective” solution for reducing delay line length in a DLL.
 Figure 2, the only embodiment described in the written de-
 scription, illustrates a “digital DLL 24 in accordance with
 the present invention.” ’507 patent, col. 2 ll. 49–50.

     The DLL 24 has an additional phase detector 30, which
 determines a phase difference between the buffered input
 clock signal CKI and a feedback clock signal CKF. ’507 pa-
 tent, col. 2 ll. 61–67. If the second phase detector 30
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6               PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

 determines that the difference between the feedback clock
 signal CKF and the buffered input clock signal CKI is
 within a 180˚ phase difference, the second phase detector
 controls the switch 28 to be at position (1), as seen above.
 Under this configuration, clock signal CKI is provided as
 an input to the delay line 16. ’507 patent, col. 2 l. 61–col.
 3, l. 6. But if the phase difference between the two clock
 signals is greater than 180˚, the second phase detector con-
 trols switch 28 to be at position (2). Under this new config-
 uration, the clock signal CKI is inverted by inverter 26 and
 then provided as an input to the delay line. ’507 patent,
 col. 3 ll. 8–15. “Through the inversion, the phase difference
 needing to be compensated by the delay line 16’ is made
 less than 180˚” which decreases the length of the delay line
 by “approximately one-half the length that a typical DLL
 would require for comparable clock deskewing needs.” ’507
 patent, col. 3 ll. 11–18.
     Independent claim 10 recites:
     A method for reducing delay line length in a digital
     delay locked loop (DLL), the method comprising:
         determining a phase difference between an
         input clock signal and a feedback clock sig-
         nal;
         maintaining the phase difference between
         the input clock signal and the feedback
         clock signal [within2] approximately 180˚,

     2   Both the Board and the parties agree that the word
 “within” is missing from the “maintaining” limitation and
 neither party challenged the Board’s decision to read the
 claim to include “within.” J.A. 7. During prosecution, the
 applicant amended the language of what became claim 10
 to include, inter alia, the limitation “within approximately
 180˚.” J.A. 7. In addition, the examiner acknowledged that
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.            7

         including adjusting the input clock signal
         with a loop comprising a phase detector,
         shift register, and delay line when the de-
         termined phase difference is less than ap-
         proximately 180˚; and
         delaying the input clock signal to compen-
         sate for the phase difference, wherein a
         number of delay cells utilized is reduced by
         approximately one-half.
 ’507 patent, col. 4 ll. 47–59.
     Dependent claim 11 recites:
     The method of claim 10 wherein the phase detector
     comprises a phase difference detector with a first
     resolution.
 ’507 patent, col. 4 ll. 60–61.
                       C. The Prior Art
           1. Donnelly (U.S. Patent No. 5,945,862)
     Donnelly, a U.S. patent entitled, “Circuitry for the De-
 lay Adjustment of a Clock Signal,” relates to providing “ad-
 justable delays” to an incoming periodic signal, like a clock
 signal. J.A. 451. Donnelly discloses a DLL system. J.A.
 453, col. 5 ll. 32–34. The DLL system determines a phase
 difference between an input clock signal and a feedback
 clock signal via its phase detector. Donnelly explains that
 the DLL operates as follows: (1) the phase detector detects
 a nonzero difference between the two clock signals and in-
 structs a counter to determine this difference; (2) the cir-
 cuit block receives information which instructs the selector
 to switch consecutively through the taps from the output of
 the blender circuit to reduce the phase error; and (3) the

 the maintaining step recites “within approximately 180 de-
 gree[s].” J.A. 7.
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8               PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

 selector switches consecutively through the taps until it
 eliminates the phase difference. J.A. 453, col. 5 l. 39–col. 6
 l. 1. Donnelly explains that this process of constantly ad-
 justing the value in the counter causes the output signal to
 “jitter” around the desired phase relationship between the
 input clock signal and the feedback clock signal. J.A. 453,
 col. 6 ll. 1–8.
              2. Kim (U.S. Patent No. 5,875,219)
     Kim, a U.S. patent entitled “Phase Delay Correction
 Apparatus,” discloses a digital DLL with an improved
 phase delay correction apparatus. J.A.II. 668, col. 1 ll. 5–
 10. The DLL includes a phase detector for outputting a
 comparing signal, a shift register that can sequentially
 shift data bit values in both directions in accordance with
 the comparing signal, a phase delay unit for delaying and
 outputting the system clock signal, a domain selecting con-
 troller, and a domain selector for adjusting the phase of a
 driving signal from one region comprising approximately
 0–180˚ to another area comprising approximately 180–
 360˚. J.A.II. 668, col 2 ll. 38–64.
                   D. The Board’s Decisions
      As relevant to this appeal, Samsung filed two IPR pe-
 titions asserting that claims 10 and 11 of the ’507 patent
 are unpatentable because they would have been obvious in
 view of Donnelly and Iwamoto (U.S. Patent No. 5,875,219)3
 and are anticipated by Kim. J.A. 133; J.A.II. 115. In its
 petitions, Samsung asserted that Donnelly and Kim dis-
 close “maintaining the phase difference between the input
 clock signal and the feedback clock signal [within] approx-
 imately 180˚” (the “maintaining limitation”), as required by
 claim 10. J.A. 157–187; J.A.II. 129–55. Samsung and its
 expert, Dr. R. Jacob Baker, explained that the input and

     3     The disclosures of Iwamoto are not relevant to this
 appeal.
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.             9

 feedback clocks in Donnelly and Kim have the same fre-
 quency and the same period. Under this assumption, the
 clock signals disclosed in the two references “always have
 a phase difference within 180˚.” J.A. 277–80; J.A.II. 217–
 27. To illustrate Samsung’s point, Dr. Baker offered the
 following example:

                                    2

                               1                   3

 J.A. 279 (annotated). The figure above shows two clock sig-
 nals, an input clock signal and a feedback clock signal, with
 the same frequency and period. In this example, the later
 rising edge of the feedback clock signal (3) lags behind the
 rising edge of the input clock signal (2) by more than 180˚.
 The phase difference between the two signals is more than
 180˚. But the earlier rising edge of the feedback clock sig-
 nal (1) is less than 180˚ ahead of the same rising edge of
 the input clock signal (2). The phase difference between
 these two signals is within approximately 180˚. Therefore,
 regardless of how the feedback clock signal is shifted, a ris-
 ing edge of the feedback clock signal will always be within
 approximately 180˚ of the input clock signal. J.A. 279.
     In its Patent Owner Preliminary Responses, ProMOS
 did not dispute that a feedback clock signal is always
 within either 180˚ ahead or 180˚ behind an input clock sig-
 nal with the same period and frequency. Instead, ProMOS
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 10             PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

 argued that the “maintaining” limitation should be con-
 strued as meaning “ensuring that the feedback clock signal
 follows behind the input clock signal by less than 180˚.”
 J.A. 833 (emphases added). ProMOS asserted that a read-
 ing of the limitation that covered a variation in either di-
 rection is inconsistent with the intrinsic record and would,
 in effect, render the limitation meaningless. J.A. 831–33.
      In its Institution Decisions, the Board agreed with Pro-
 MOS’s construction of the “maintaining” limitation. J.A.
 867–69. The Board accepted ProMOS’s characterization of
 the prosecution history and agreed with ProMOS that
 Samsung’s interpretation would render the claim term
 “meaningless.” J.A. 867–69. Accordingly, the Board ini-
 tially did not institute IPRs on challenged claims 10 and
 11, but instituted the IPRs based on other unpatentability
 grounds, involving other claims (claims 13 and 15) that are
 not at issue in this appeal. J.A. 892–93.
      After the Supreme Court’s decision in SAS Inst., Inc. v.
 Iancu, 138 S. Ct. 1348 (2018), the Board issued orders in
 both IPRs, instituting on claims 10 and 11. J.A. 1042–43.
 Due to the limited scope of the original institution, how-
 ever, ProMOS’s Patent Owner Responses only addressed
 claims 13 and 15. Accordingly, the Board asked the parties
 if further briefing was necessary for claims 10 and 11. J.A.
 1042–43. In response, ProMOS “indicated that it has noth-
 ing to add, for claims 10 and 11, and would be satisfied if
 [it] could simply rely on arguments made in [the] Patent
 Owner’s Preliminary Response for claims 10 and 11.” J.A.
 1047–48. Samsung, however, requested that it be allowed
 to file replies that addressed the arguments for claims 10
 and 11 in ProMOS’s Preliminary Responses. J.A. 1048.
 The Board granted Samsung’s request. J.A. 1048–49.
     In its reply, Samsung argued that the Board should
 adopt the plain and ordinary meaning of the “maintaining”
 limitation—one without a directionality requirement—be-
 cause the claim language, specification, and prosecution
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.           11

 history cut against ProMOS’s proposed construction. J.A.
 1074–85. Samsung argued that: (1) there was no “clear and
 unmistakable disavowal” of the full scope of the “maintain-
 ing” limitation; (2) the specification and the language of
 claim 13 demonstrated that the patent applicant deliber-
 ately chose not to inject a directionality requirement into
 the “maintaining” limitation; and (3) as confirmed by Pro-
 MOS’s own declarant, the specification itself does not sup-
 port ProMOS’s construction. J.A. 1074–80. Samsung
 explained that the sole embodiment describes a phase dif-
 ference between the input and feedback clock signals that
 oscillates between less than 180˚ and more than 180˚. J.A.
 1080–83. Samsung also pointed out that ProMOS’s Pre-
 liminary Response had misrepresented the prosecution
 history that had led the Board to originally deny institution
 on claims 10 and 11. J.A. 1083–85.
     The Board rejected ProMOS’s proposed construction of
 the “maintaining” limitation the second time around. In
 its Final Written Decisions, the Board stated that it had
 changed its mind after reviewing “the complete trial rec-
 ord,” noting that the intrinsic evidence supported a finding
 that the limitation imposes no directionality requirement,
 such that one signal must follow the other by within ap-
 proximately 180˚. J.A. 16–22. In particular, the Board ex-
 plained that ProMOS’s interpretation of the prosecution
 history was “internally inconsistent and self-contradic-
 tory,” and found no disavowal by the applicant with regard
 to the subject matter of claim 10. J.A. 19–21. The Board
 concluded that the “maintaining” limitation “imposes no di-
 rectional [sic] requirement, so either signal can be ahead or
 behind the other by within approximately 180˚.” J.A. 22.
 Based on this construction, the Board determined that
 Donnelly and Kim both disclose the “maintaining” limita-
 tion. J.A. 40–45; J.A.II 32–38. The Board found that Sam-
 sung had established, by a preponderance of the evidence,
 that the challenged claims are anticipated by Kim and
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 12             PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

 would have been obvious over the combined teachings of
 Donnelly and Iwamoto. J.A. 45
    ProMOS timely appealed the Board’s final decisions.
 We have jurisdiction under 28 U.S.C. § 1295(a)(4)(A).
                        II. DISCUSSION
      ProMOS appeals: (1) the Board’s construction of the
 “maintaining” limitation; and (2) the Board’s anticipation
 and obviousness findings based on its construction of the
 “maintaining” limitation. Both parties agree that the claim
 construction dispute is dispositive to the Board’s anticipa-
 tion and obviousness findings. Appellant Br. 10 (“Claim
 construction is dispositive in this appeal.”); Appellee Br. 38
 (“It is undisputed that if the Board’s construction is upheld,
 then there can be no error in the Board’s finding of un-
 patentability.”); Appellant Reply Br. 9. Accordingly, we ad-
 dress the claim construction dispute inquiry first.
                    A. Claim Construction
      This court reviews the ultimate construction of a claim
 de novo. Teva Pharm. USA, Inc. v. Sandoz, Inc., 574 U.S.
 318 (2015). The court reviews subsidiary factual findings
 for substantial evidence. Knowles Elecs. LLC v. Iancu, 886
 F.3d 1369, 1374 (Fed. Cir. 2018). When we review the
 claim construction of a patent term in an IPR appeal after
 the patent has expired, such as in this case, we apply the
 standard established in Phillips, not the “broadest reason-
 able interpretation.” See In re CSB-Sys. Int’l, Inc., 832 F.3d
 1335, 1342 (Fed. Cir. 2016). That is, the words of a claim
 “are generally given their ordinary and customary mean-
 ing,” as the term would have been understood by a person
 of ordinary skill in the art at the time of the invention.
 Phillips v. AWH Corp., 415 F.3d 1303, 1313 (Fed. Cir.
 2005).
     ProMOS argues that the Board’s construction of the
 “maintaining” limitation is erroneous because it does not
 include a directionality requirement.      According to
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.             13

 ProMOS, the “maintaining” limitation should be construed
 as “ensuring that the feedback clock signal follows behind
 the input clock signal by less than 180˚.” Appellant Br. 11
 (emphasis added). In support of this argument, ProMOS
 relies on certain language from the written description and
 the prosecution history. As described in further detail be-
 low, however, ProMOS misinterprets the intrinsic evidence
 and attempts to import the narrower characteristics of an
 embodiment into an unrelated claim term.
       1. The Plain Language of the Claims and the
           Written Description Do Not Support
          Importing a Directionality Restriction
            into the “Maintaining” Limitation
      The plain text of the claim does not place a directional-
 ity restriction on the “maintaining” limitation. Claims 8
 and 10, the only two claims reciting the limitation, simply
 require that the phase difference between the input and
 the feedback clock signals is maintained within 180˚. ’507
 patent, col. 4 ll. 51–53 (“maintaining the phase difference
 between the input signal and the feedback clock signal
 [within] approximately 180˚”). Neither claim states or im-
 plies that the phase difference between the two signals is
 calculated by how much the feedback signal “follows” or
 lags behind the input signal. ’507 patent, col. 4 ll. 33–39,
 51–53. Accordingly, unless “the patentee has chosen to be
 his own lexicographer in the specification or has clearly dis-
 claimed coverage during prosecution,” we must interpret
 claims according to their plain language. See E-Pass
 Techs., Inc. v. 3Com Corp., 343 F.3d 1364, 1370 Fed. Cir.
 2003). But there is no such explicit definition or disclaimer.
 Outside of claims 8 and 10, the ’507 patent only refers to
 the “maintaining” limitation in two instances: in the Ab-
 stract and in the Summary of the Invention. ’507 patent,
 Abstract; ’507 patent, col. 2 ll. 3–11. In both cases, the lim-
 itation is described broadly, without a directionality modi-
 fier such as “behind.” Id.
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 14             PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

     ProMOS argues that one of the statements in the writ-
 ten description, “CKF is more than 180˚ behind CKI,” indi-
 cates that the “maintaining” limitation calculates the
 phase difference based on how much the feedback signal
 lags the input signal. Appellant Br. 12. The written de-
 scription, however, supports no such inference. In discuss-
 ing the sole embodiment, depicted in Figure 2, the ’507
 patent recites:
      When the second phase detector 30 determines
      that CKF [the feedback clock signal] is more than
      180˚ behind CKI [the input clock signal], the second
      phase detector 30 controls switch 28 to be at posi-
      tion (2). The inverted buffered clock signal is thus
      selected, so that the input clock signal CKI is re-
      versed by 180˚[.] Through the inversion, the phase
      difference needing to be compensated by the delay
      line 16’ is made less than 180˚ and within the nor-
      mal operation capabilities of the phase adjusting
      loop formed by phase detector 12, shift register 14’,
      and delay line 16’.
 ’507 patent, col. 3 ll. 7–15. This discussion of the preferred
 embodiment does not address the “maintaining” limitation.
 This passage explains that the phase detector “select[s]”
 the inverted buffered clock signal when it “determines”
 that the feedback signal is more than 180˚ behind the input
 signal. ’507 patent, col. 3 ll. 7–15. It does not state that
 this directionality requirement should also apply when the
 DLL is “maintaining” the phase difference between the two
 signals. ’507 patent, col. 3 ll. 7–15.
     ProMOS conflates the “determining” and “selecting”
 steps with the separate “maintaining” limitation. As dis-
 closed in claims 8 and 10 of the patent, the “maintaining”
 limitation does not involve “determining” whether a phase
 difference exists or “selecting” an inverted buffered clock
 signal. Read plainly, the claim language states that the
 DLL maintains the phase difference between the two
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.             15

 signals within approximately 180˚ by adjusting the input
 clock signal with a loop comprising a phase detector, shift
 register, and delay line when the determined phase differ-
 ence is less than approximately 180˚. ’507 patent, col. 4 ll.
 51–57. We need not construe the “maintaining” limitation
 so narrowly simply because an embodiment describes other
 steps, namely, the “determining” and “selecting” steps,
 which do have directional restrictions. In fact, this direc-
 tionality restriction is captured by claim 13 of the ’507 pa-
 tent, which includes the “determining” and “selecting”
 limitations:
     A method for reducing delay line length in a digital
     delay locked loop (DLL), the method comprising:
     determining whether a feedback clock signal in the
     DLL follows within a 180˚ phase difference behind
     an input clock signal; and
     selecting a switch position according to the deter-
     mining step, including selecting a first switch posi-
     tion when the feedback clock signal follows behind
     the input clock signal with 180˚.
 ’507 patent, col. 4 l. 66–col. 5 l. 10 (emphases added). Like
 the discussion of the preferred embodiment, claim 13
 acknowledges that these two steps include a directionality
 restriction. If the patentee wanted to import that same re-
 striction—“follows behind”—into the “maintaining” limita-
 tion of claim 10, he could have used similar language. But
 he did not. The written description further confirms that
 the patentee understood how to describe the relationship
 between two clock signals in a manner that makes clear
 which clock signal leads or lags the other in phase. ’507
 patent, col. 2, ll. 63–66 (“When the second phase detector
 30 determines that the feedback clock signal CKF from the
 DLL 24 is behind the buffered input clock CKI within a
 180˚ phase difference . . . .”). We decline to adopt a nar-
 rower construction in contravention of the plain language
 of the claims.
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 16             PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

     And, even if we were to determine that the above pas-
 sage pertains to the “maintaining” limitation, it is well es-
 tablished that claims may be broader than described
 embodiments. See, e.g., Innogenetics, N.V. v. Abbott Labs.,
 512 F.3d 1363, 1370 (Fed. Cir. 2008).
       2. The Prosecution History Does Not Support
        ProMOS’s Narrower Proposed Construction
             of the “Maintaining” Limitation
     ProMOS argues that the examiner allowed claim 10
 over Butcher (U.S. Patent No. 4,789,996), another prior art
 reference, because Butcher did not teach “maintaining the
 phase difference between the input clock signal and the
 feedback signal within 180 degrees.” Appellant Br. 13 (cit-
 ing J.A. 393). According to ProMOS, “Butcher teaches a
 phase locked loop having input and feedback clock signals
 with equal frequencies.” Id. ProMOS insists that, if the
 examiner had understood the “maintaining” limitation un-
 der the Board’s construction, “he could not have reached
 the conclusion he did—that the DLL in Butcher did not
 teach the claimed ‘maintaining’ step.” Id.
      ProMOS’s argument requires several logical leaps. In
 order to arrive at the same conclusion as ProMOS, the rec-
 ord must establish that: (1) the input and feedback clock
 signals disclosed in Butcher have the same frequencies;
 (2) the examiner knew that these clock signals have equiv-
 alent frequencies; and (3) the examiner’s allowance of the
 “maintaining” limitation was directed to the “within 180˚”
 part of the maintaining step, and not to the overall step
 itself. But whether the record supports these factual hur-
 dles is irrelevant because ProMOS mischaracterizes the
 prosecution history. The patentee did not add the “main-
 taining” limitation to claim 10 in order to overcome rejec-
 tion.
     During prosecution, the examiner rejected pending
 claim 8, which included the “maintaining” limitation, as ob-
 vious in view of Butcher. J.A. 393. Although the examiner
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.           17

 admitted that Butcher did not disclose the “maintaining”
 limitation, he concluded that the step would have been ob-
 vious to a person of ordinary skill in the art. J.A. 393 (“It
 would have been obvious to one skilled in the art to main-
 tain a delay of 180 degrees by selecting a proper number of
 registers without changing the scope of the Butcher refer-
 ence.”). Pending claims 9 and 11 (now claim 10), which de-
 pended from pending claim 8 and had additional
 limitations on top of the “maintaining” limitation, were
 found to include allowable subject matter. J.A. 394. Ac-
 cordingly, the patentee rewrote claims 9 and 11 in inde-
 pendent form, incorporating the features of claim 8 from
 which they depended. J.A. 406–07.
     The record is clear: the “maintaining” limitation was
 not added to pending claim 11/now claim 10 in order to
 overcome the prior art, as argued by ProMOS. J.A. 33–34.
 Pending claim 11 already included the “maintaining” limi-
 tation based on its dependency on pending claim 8. These
 facts do not imply that the examiner somehow interpreted
 the “maintaining” limitation to include a directionality re-
 striction, as ProMOS contends.
       3. The Board’s Construction Does Not Render
         the “Maintaining” Limitation Superfluous
     Finally, ProMOS argues that the Board’s construction
 of the “maintaining” limitation renders the limitation su-
 perfluous. Appellant Br. 16. Under the Board’s construc-
 tion, any two clock signals with identical frequencies (and
 therefore, identical periods) are always “within 180˚ of each
 other.” ProMOS concludes that the limitation has “no real
 meaning” under this construction because the limitation is
 always satisfied.
     The Supreme Court has stated that “[e]ach element
 contained in a patent claim is deemed material to defining
 the scope of the patented invention.” Warner-Jenkinson
 Co., Inc. v. Hilton Davis Chem. Co., 520 U.S. 17, 29 (1997).
 Consistent with this philosophy, we have determined that
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 18             PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

 it is generally improper to construe a patent claim so that
 express claim limitations or elements are rendered super-
 fluous. See Biocon, Inc. v. Straumann Co., 441 F.3d 945,
 950–52 (Fed. Cir. 2006). The distinction here, however, is
 that claims 8 and 10 of the ’507 patent are not necessarily
 rendered “superfluous” by the Board’s construction.
      The plain language of the claims does not require the
 input clock signal and the feedback clock signal to have the
 same frequency and period. J.A. 131 at 4:47–59. There-
 fore, the Board’s construction does not render the claimed
 maintaining step superfluous because a pair of clock sig-
 nals with different frequencies would not satisfy the limi-
 tation. These facts are distinct from those present in our
 “superfluous” precedent, where the erroneous claim con-
 struction ignored the ordinary meaning of explicit claim
 limitations or read out limitations in their entirety. See,
 e.g., Biocon, 441 F.3d at 950–52 (“In sum, the effect of
 adopting Diro’s proposed claim construction would be to
 read limitations [a], [b], [e], and [h] out of the claim. Not
 only would that be contrary to the principle that claim lan-
 guage should not be treated as meaningless, but it would
 be contrary to the specification, which describes the fea-
 tures of the claimed abutment in detail . . . .”); Elektra In-
 strument S.A. v. O.U.R. Sci. Int’l, Inc., 214 F.3d 1302, 1307
 (Fed. Cir. 2000) (claim language “only within a zone ex-
 tending between latitudes 30˚–45˚” does not read on a de-
 vice with radiation sources extending between 14˚–43˚
 because “[a]ny other conclusion renders the reference to 30
 degrees superfluous”).
     ProMOS contends that a DLL, such as the one dis-
 closed in the ’507 patent, always has clock signals with the
 same frequency because it is a necessary characteristic of
 a DLL circuit. Appellant Br. 16–17. But neither party pre-
 sented evidence on this issue. J.A. 21–22 (“Patent Owner
 has not, either in its Preliminary Response or its Patent
 Owner Response, asserted in a DLL the input clock signal
 and the feedback clock signal necessarily would have the
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.            19

 same frequency. Petitioner has not had a full opportunity
 to respond to this new argument. Accordingly, the new ar-
 gument, raised for the first time in Patent Owner’s Sur-
 Reply, will not be considered.”). ProMOS relies on deposi-
 tion testimony from Samsung’s expert stating that, “in the
 engineering sense,” two synchronized DLL clock signals
 have the same frequencies and the same signals. J.A. 959
 at 9:12–22. This, however, is not an admission that DLL
 clock signals always have the same input and feedback sig-
 nals. In that context, Samsung’s expert may have been de-
 fining “synchronization” instead of opining on the
 fundamental characteristics of clock signals in DLL cir-
 cuits. We decline to adopt ProMOS’s proposed construction
 without any supporting evidence in the record.
      B. The Board’s Unpatentability Determinations
     Both parties agree that the claim construction dispute
 over the “maintaining” limitation is dispositive to the
 Board’s anticipation and obviousness findings. Appellant
 Br. 10 (“Claim construction is dispositive in this appeal.”);
 Appellee Br. 38 (“It is undisputed that if the Board’s con-
 struction is upheld, then there can be no error in the
 Board’s finding of unpatentability.”); Appellant Reply Br.
 9. Accordingly, because the Board correctly construed the
 “maintaining” limitation, we conclude that there is no error
 in the Board’s findings of unpatentability.
                       III. CONCLUSION
     The Board correctly construed the “maintaining” limi-
 tation. As both parties agree that our determination with
 respect to the Board’s construction of that limitation is dis-
 positive as to whether substantial evidence supports the
 Board’s anticipation and obviousness findings, we affirm
 the Board’s decisions in both IPRs.
                         AFFIRMED
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 20               PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

                               COSTS
      No costs.
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         NOTE: This disposition is nonprecedential.

    United States Court of Appeals
        for the Federal Circuit
                       ______________________

             PROMOS TECHNOLOGIES, INC.,
                      Appellant

                                      v.

          SAMSUNG ELECTRONICS CO., LTD.,
                      Appellee
               ______________________

                             2019-1343
                       ______________________

     Appeal from the United States Patent and Trademark
 Office, Patent Trial and Appeal Board in No. IPR2017-
 01412.

       -----------------------------------------------------------------

             PROMOS TECHNOLOGIES, INC.,
                      Appellant

                                      v.

          SAMSUNG ELECTRONICS CO., LTD.,
                      Appellee
               ______________________

                             2019-1344
                       ______________________
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 2              PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

     Appeal from the United States Patent and Trademark
 Office, Patent Trial and Appeal Board in No. IPR2017-
 01413.
                  ______________________

 REYNA, Circuit Judge, dissenting.
      The ’507 patent concerns an improvement to the oper-
 ation of a delay locked loop—a circuit used to synchronize
 digital clocks by delaying the signal of one clock (here, an
 input clock signal) relative to the signal of another (here, a
 feedback clock signal) to compensate for the “phase differ-
 ence” between the signals. At issue is whether this “phase
 difference,” as used in the claim term “maintaining the
 phase difference between the input clock signal and the feed-
 back clock signal [within] approximately 180˚” is to be
 measured in only one direction, i.e., as the lag of the feed-
 back signal behind the input signal, or whether “phase dif-
 ference” refers to the variance between the clock signals in
 either direction, i.e. as either the lag or the lead of the input
 signal relative to the feedback signal.
     A careful analysis of the way “phase difference” is used
 in the claims, and the way the invention is described in the
 specification, makes clear that the phase difference recited
 in the ’507 patent is unidirectional. Neither the majority
 nor the Board, however, engage in this analysis. Instead,
 they begin with the assumption that the “plain meaning”
 of the term “phase difference” is bi-directional. Only then
 do they turn to the intrinsic evidence to assess whether a
 “directional limitation” should be “imported” into the
 claims under the exacting criteria for lexicography and ex-
 press disavowal.
     This is contrary to the framework we set forth in Phil-
 lips, which dictates that the relevant plain meaning of a
 claim term is its meaning in the context of the patent, to be
 discerned at the outset in the context of the specification
 and other intrinsic evidence.       Because the majority
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.            3

 embraces a construction of “phase difference” divorced
 from its usage in the patent and affirms the invalidation of
 the challenged claims based on that erroneous construc-
 tion, I respectfully dissent.
                               I
      It is well-established that we generally give claim
 terms their plain and ordinary meaning to a skilled artisan
 when read in the context of the specification and prosecu-
 tion history. Thorner v. Sony Computer Ent. Am. LLC, 669
 F.3d 1362, 1365 (Fed. Cir. 2012); Phillips v. AWH Corp.,
 415 F.3d 1303, 1315-17 (Fed. Cir. 2005). The doctrines of
 lexicography and disavowal are narrow exceptions to this
 rule that are applied when we limit claim scope in contra-
 diction to the claim language. Thorner, 669 F.3d at 1365
 (citing Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576,
 1580 (Fed. Cir. 1996)).
     The intrinsic evidence is therefore integral at the out-
 set of claim construction for discerning the plain and ordi-
 nary meaning of claim terms in the context of the patent.
 See Lexion Med., LLC v. Northgate Techs., Inc., 641 F.3d
 1352, 1356 (Fed. Cir. 2011). (“The customary meaning of a
 claim term is not determined in a vacuum and should be
 harmonized . . . with the intrinsic record, as understood
 within the technological field of the invention.”); Abbott
 Labs. v. Andrx Pharms., Inc., 452 F.3d 1331, 1336 (Fed.
 Cir. 2006) (“Where claim terms are ambiguous or disputed,
 then we turn to the specification as . . . the single best
 guide to the meaning of a disputed term”) (quoting Phillips,
 415 F.3d at 1315)). In Phillips, we specifically cautioned
 against construing claims by first developing a broad defi-
 nition of claim terms divorced from the context of the pa-
 tent and then turning to the specification only to look for
 grounds for limiting the claim scope. Phillips, 415 F.3d at
 1320 (discussing Texas Digital Sys., Inc. v. Telegenix, Inc.,
 308 F.3d 1193 (Fed. Cir. 2002)). Such an approach, we
 noted, posed a “risk of systematic overbreadth,” which “is
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 4              PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

 greatly reduced if the court instead focuses at the outset on
 how the patentee used the claim term in the claims, speci-
 fication, and prosecution history, rather than starting with
 a broad definition and whittling it down.” Id. at 1321.
     Thus, we have rejected a proposed claim construction
 where it relies on an initial “assumption” that a claim term
 has a broad “ordinary meaning” unsupported by the intrin-
 sic or extrinsic evidence. Ruckus Wireless, Inc. v. Innova-
 tive Wireless Sols., LLC, 824 F.3d 999, 1003 (Fed. Cir.
 2016). When the plain meaning of a claim term does not
 clarify whether and how a restriction applies, we have said
 that such ambiguity is to be resolved in the first instance
 by reviewing the claim language as a whole, the other in-
 trinsic record, and any extrinsic evidence. See Uship Intel-
 lectual Props., LLC v. U.S., 714 F.3d 1311, 1315 (Fed. Cir.
 2013).
     Fundamentally, when construing claims in light of the
 specification, we do so “with a view to ascertaining the in-
 vention.” United States v. Adams, 383 U.S. 39, 49 (1966).
 Even when applying the broadest reasonable interpreta-
 tion standard, which is broader than the standard applica-
 ble here, we have held that “[t]he correct inquiry . . . is not
 whether the specification proscribes or precludes some
 broad reading of the claim term adopted by the examiner.”
 In re Smith Int’l, Inc., 871 F.3d 1375, 1382–83 (Fed. Cir.
 2017). Rather, a correct construction is one “that corre-
 sponds with . . . how the inventor describes his invention in
 the specification, i.e., an interpretation that is consistent
 with the specification.” Id. at 1383 (citation and internal
 quotation marks omitted); see also PPC Broadband, Inc. v.
 Corning Optical Commc’ns RF, LLC, 815 F.3d 747, 752
 (Fed. Cir. 2016).
                               II
     Because the digital clock signals described in the ’507
 patent are periodic, i.e. they repeat at a regular interval,
 the variance or “phase difference” between two signals, A
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.               5

 and B, can in theory always be measured in one of two
 ways: (1) from a certain point on signal A to the next corre-
 sponding point on signal B (i.e., as the lag of signal B be-
 hind signal A), or (2) from a point on signal B to the next
 corresponding point on signal A (i.e. as the lead of signal B
 ahead of signal A). The question of whether a reference is
 referring to either or both of these measurements as the
 “phase difference” will depend on the context.
     This is not unlike the ambiguity presented when we
 talk about the “time difference” between two analog clocks:
 The time difference between Clock A, which reads 1 o’clock,
 and Clock B, which reads 8 o’clock, could be 7 hours or 5
 hours, depending on whether we are looking at the lag or
 the lead of Clock A relative to Clock B. If one is instructed
 to determine the time difference between these two clocks,
 and to maintain the time difference within 6 hours, that
 person would first need to understand what “time differ-
 ence” means in the full context of the instruction.
      Here, the Board recognized in its initial Institution De-
 cision that the phrase, “maintaining the phase difference
 between the input clock signal and the feedback clock sig-
 nal [within] approximately 180°,” was facially ambiguous
 in that it “does not specify whether the input clock signal
 must be ahead of the feedback clock signal or the feedback
 clock signal must be ahead of the input clock signal.” J.A.
 867. Consistent with its obligations under Phillips, the
 Board looked to the specification for guidance, and deter-
 mined that the patent’s written description of the limita-
 tion at issue indicated that “phase difference” referred to
 the lag of the feedback clock signal behind the input clock
 signal:
     the Specification of the ’507 patent makes a distinc-
     tion between feedback clock signals that are more
     than 180° behind the input clock signal and feed-
     back clock signals that are less than 180° behind
     the input clock signal. [’507 patent, col. 3 ll. 8-15].
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 6              PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

     Indeed, when the feedback clock signal is deter-
     mined to be more than 180° behind the input clock
     signal, a step is applied to invert it, effectively
     shifting it by 180°. Id. That is the disclosed imple-
     mentation for the limitation at issue, i.e., “main-
     taining the phase difference between the input
     clock signal and the feedback clock signal [within]
     approximately 180°.”
 J.A. 868-889 (emphasis added).
     This unidirectional understanding of “phase differ-
 ence” is consistent with the usage of the term throughout
 the claims. Claim 10 recites the following steps:
     determining a phase difference between an input
     clock signal and a feedback clock signal;
     maintaining the phase difference between the input
     clock signal and the feedback clock signal [within]
     approximately 180˚, including adjusting the input
     clock signal with a loop comprising a phase detec-
     tor, shift register, and delay line when the deter-
     mined phase difference is less than approximately
     180˚; and
     delaying the input clock signal to compensate for
     the phase difference, wherein a number of delay
     cells utilized is reduced by approximately one-half.
 ’507 patent, col. 4 ll. 49–59 (emphasis added). The “phase
 difference” determined in the first step is the antecedent
 for the “phase difference” in the subsequent steps, and thus
 the claim term should be construed to have a consistent
 meaning, including with respect to directionality, in each
 step. See Phonometrics, Inc. v. Northern Telecom Inc., 133
 F.3d 1459, 1465 (Fed. Cir. 1998) (“A word or phrase used
 consistently throughout a claim should be interpreted con-
 sistently.”). The steps of determining a phase difference,
 maintaining a phase difference within a given range, and
 adjusting the input signal based on the determined
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.                7

 difference all indicate that the “phase difference” recited in
 the claim is meant to be a single measurable value: the
 term should not be construed to encompass two different
 “phase differences.” Moreover, the phrase “delaying the in-
 put clock signal to compensate for the phase difference” in-
 dicates that the phase difference refers to the lag of the
 feedback clock behind the input clock. As a matter of com-
 mon usage, if I say that I am delaying Clock A to compen-
 sate for the time difference between Clock A and Clock B, I
 am implying that Clock B is behind Clock A.
      Additional intrinsic evidence supports the construction
 of “phase difference” as unidirectional. In particular, the
 ’507 patent teaches that maintaining the phase difference
 within 180˚ by inverting (or shifting by 180˚) the input sig-
 nal when the phase difference is greater than 180˚ reduces
 the length of the delay line needed to compensate for the
 phase difference. ’507 patent, col. 3 ll. 7-18; col. 4 ll. 35-42.
 This only makes sense if the “phase difference” at each step
 is consistently measured in one direction.
                                III
      Neither the Board nor the Majority refute or even en-
 gage with this analysis in arriving at the plain meaning of
 the claim language. Indeed, when the Board revised its
 construction of “maintaining a phase difference . . . [within]
 approximately 180˚” in its Final Written Decision, the
 Board pointed to nothing in the ’507 patent that indicated
 a bi-directional usage of “phase difference.” Rather, the de-
 cision reframed the facial ambiguity identified in its insti-
 tution decision as linguistic clarity: “The words of the claim
 are clear in not specifying which signal leads or lags.” J.A.
 17 (emphasis added). The Board then proceeded to explain
 why the intrinsic evidence supporting a directional limita-
 tion does not amount to “express disavowal” justifying “re-
 writing” of the claims. Id.
     The majority relies on essentially the same reasoning.
 Citing only to the text of the “maintaining” limitation, and
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 8              PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.

 without any further discussion, the opinion concludes in a
 single sentence that neither claim 8 nor claim 10 “states or
 implies that the phase difference between the two signals
 is calculated by how much the feedback signal ‘follows’ or
 lags behind the input signal.” Slip op. 13. The opinion then
 proceeds to search the intrinsic evidence for lexicography
 or disavowal, and ultimately finds none. But if the skilled
 artisan would understand the plain and ordinary meaning
 of “phase difference” in the context of the patent to be uni-
 directional, then the patentee need not include additional
 verbiage to narrow the scope of its claims from some other
 broader meaning. Ultimately, nowhere does the majority
 conduct the principal analysis of determining the plain and
 ordinary meaning of the claim language, including the
 words “phase difference,” in the context of the patent. This
 is error.
      Nothing in the majority’s remaining analysis mitigates
 this deficiency. The mere fact that another independent
 claim, claim 13, recites “determining whether a feedback
 clock signal in the DLL follows within a 180° phase differ-
 ence behind an input clock signal” does not contradict the
 consistent directionality of the “phase difference” described
 throughout the patent. Slip op. at 15 (quoting ’507 patent,
 col. 4 l. 66–col. 5 l. 10). We have previously acknowledged
 that a patentee’s choice to use different, though similar,
 words for corresponding limitations in different claims
 “does not mandate different interpretations of the two lim-
 itations . . . .” Kraft Foods, Inc. v. Int’l Trading Co., 203
 F.3d 1362, 1368 (Fed. Cir. 2000) (internal quotations and
 citation omitted). Here, in particular, the use of the words
 “follows” and “behinds” in one claim and not others does
 not implicate the doctrine of claim differentiation because
 the claims contain different steps that confer different
 claim scope separate and apart from the language at issue.
 Cf., id. at 1366 (noting that the doctrine of claim differen-
 tiation is based on the presumption that two claims in the
 same patent have different claim scope).
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 PROMOS TECHS., INC. v. SAMSUNG ELECS. CO., LTD.            9

     Likewise, a bi-directional construction of “phase differ-
 ence” cannot rest on the conclusion that the construction
 does not always render the “maintaining” limitation super-
 fluous and meaningless. Slip Op. 17-19. More relevant
 here is the canon that in cases of genuine ambiguity, claims
 are to be construed in favor of preserving validity. Ruckus,
 824 F.3d at 1004 (citing Phillips, 415 F.3d at 1327). Here,
 except in those circumstances where the “maintaining”
 limitation is functionally meaningless, the majority’s bi-di-
 rectional reading of “phase difference” renders the claims
 at issue indefinite because it encompasses two different
 ways of determining the phase difference with no guidance
 on which to apply for any given claim, precluding a skilled
 artisan from discerning with “reasonable certainty”
 whether the “maintaining” limitation is satisfied. See Teva
 Pharms. USA, Inc. v. Sandoz, Inc., 789 F.3d 1335, 1345
 (Fed. Cir. 2015).
      Ultimately, there is sometimes a fine line between “us-
 ing the specification to interpret the meaning of a claim
 and importing limitations from the specification into the
 claim.” Phillips, 415 F.3d at 1323; Intervet Am., Inc. v.
 Kee–Vet Labs., Inc., 887 F.2d 1050, 1053 (Fed. Cir. 1989)
 (cautioning against confusing “interpreting what is meant
 by a word in a claim” with “adding an extraneous limitation
 appearing in the specification”). Here, the Board avoided
 its obligation to engage in the former task by mistaking it
 for the latter. The majority joins the Board in misjudging
 the line.
     For these reasons, I would reverse the Board’s claim
 construction. Because Samsung has made no argument
 that the invalidation of the claims at issue could be af-
 firmed under ProMOS’s construction, I would reverse the
 invalidation of those claims as well.