Court Opinion

ID: 808413
Source: CourtListenerOpinion
Date Created: 2012-09-13 15:16:26+00
Date Added: 2024-06-11T18:00:30.410865
License: Public Domain

NOTE: This disposition is nonprecedential

 United States Court of Appeals
     for the Federal Circuit
            __________________________

   IN RE REMBRANDT TECHNOLOGIES, LP,
            PATENT LITIGATION
           __________________________

    REMBRANDT TECHNOLOGIES, LP AND
REMBRANDT TECHNOLOGIES, LLC (doing business
              as Remstream),
           Plaintiffs-Appellants,
                         v.
  CABLEVISION SYSTEMS CORPORATION AND
           CSC HOLDINGS, INC.,
            Defendants-Appellees,
                        AND

   ABC INC., CBS CORPORATION, AND NBC
  UNIVERSAL, INC. (now known as NBCUniversal
                 Media, LLC),
             Defendants-Appellees,
                        AND

CENTURY-TCI CALIFORNIA COMMUNICATIONS,
 LP, CENTURY-TCI CALIFORNIA, LP, CENTURY-
TCI DISTRIBUTION COMPANY, LLC, CENTURY-
       TCI HOLDINGS, LLC, PARNASSOS
      COMMUNICATIONS, LP, PARNASSOS
 DISTRIBUTION COMPANY I, LLC, PARNASSOS
 DISTRIBUTION COMPANY II, LLC, PARNASSOS
REMBRANDT TECH   v. CABLEVISION           2

HOLDINGS, LLC, PARNASSOS, LP, AND WESTERN
           NY CABLEVISION, LP,
            Defendants-Appellees,
                           AND

CHARTER COMMUNICATIONS OPERATING LLC
   AND CHARTER COMMUNICATIONS, INC.,
            Defendants-Appellees,
                           AND

    COMCAST CABLE COMMUNICATIONS
     HOLDINGS, INC., COMCAST CABLE
     COMMUNICATIONS, LLC, COMCAST
       CORPORATION, COMCAST OF
  FLORIDA/PENNSYLVANIA, LP, COMCAST OF
PENNSYLVANIA II, LP, AND COMCAST OF PLANO,
                    LP,
            Defendants-Appellees,
                           AND

                    COXCOM, INC.,
                   Defendant-Appellee,
                           AND

    FOX BROADCASTING COMPANY AND FOX
        ENTERTAINMENT GROUP, INC.,
             Defendants-Appellees,
                           AND

       SHARP CORPORATION AND SHARP
        ELECTRONICS CORPORATION,
             Defendants-Appellees,
                           AND

  TIME WARNER CABLE LLC, TIME WARNER
 CABLE, INC., TIME WARNER ENTERTAINMENT
        COMPANY, L.P., TIME WARNER
3                         REMBRANDT TECH    v. CABLEVISION

      ENTERTAINMENT-ADVANCE/NEWHOUSE
    PARTNERSHIP, AND TIME WARNER NEW YORK
    CABLE LLC (known as Time Warner NY Cable LLC),
                Defendants-Appellees,
                          AND

    ADELPHIA COMMUNICATIONS CORPORATION,
      ADELPHIA CONSOLIDATION LLC, AMBIT
     MICROSYSTEMS, INC., CISCO SYSTEMS, INC.,
    MOTOROLA, INC., NETGEAR, INC., SCIENTIFIC
        ATLANTA INC., AND THOMSON, INC.,
                    Defendants.
               __________________________

                       2012-1022
               __________________________

    Appeal from the United States District Court for the
District of Delaware in case no. 07-MD-1848, Chief Judge
Gregory M. Sleet.
               ___________________________

              Decided: September 13, 2012
              ___________________________

    MICHAEL J. BONELLA, Kessler Topaz Meltzer & Check
LLP, of Radnor, Pennsylvania, argued for plaintiffs-
appellants. With him on the brief was PAUL B. MILCETIC.
Of counsel was JENNA M. PELLECCHIA.

   DAVID S. BENYACAR, Kaye Scholer LLP, of New York,
New York, for defendants-appellees Time Warner Cable,
LLC, et al., and EDWARD R. REINES, Weil, Gotshal &
Manges LLP, of Redwood Shores, California, for defen-
dants-appellees ABC, Inc., et al., argued for all defen-
dants-appellees. With them on the brief were DANIEL L.
REMBRANDT TECH   v. CABLEVISION                         4

REISNER, Kaye Scholer, LLP, of New York, New York, for
Time Warner Cable, LLC, et al.; TIMOTHY C. SAULSBURY,
Weil, Gotshal & Manges LLP, of Redwood Shores, Cali-
fornia, for ABC, Inc., et al.; MARK A. PERRY, JOSH A.
KREVITT, and BENJAMIN HERSHKOWITZ, Gibson, Dunn &
Crutcher LLP, of Washington, DC, for CSC Holdings, Inc.,
et al.; KEVIN D. HOGG and JOHN R. LABBE, Marshall,
Gerstein & Borun LLP, of Chicago, Illinois, for Charter
Communications Operating LLC, et al.; MITCHELL G.
STOCKWELL, Kilpatrick Townsend & Stockton LLP, of
Atlanta, Georgia, for CoxCom, Inc.; JEFFREY B. PLIES,
Dechert LLP, of Austin, Texas, and MARTIN J. BLACK, of
Philadelphia, Pennsylvania, for Fox Broadcasting Com-
pany, et al.; RICHARD H. BROWN III, Day Pitney LLP, of
Parsippany, New Jersey, for Sharp Corporation, et al.;
and BRIAN L. FERRALL, Keker & Van Nest, LLP, of San
Francisco, California, for Comcast Cable Communications
Holdings, Inc., et al. Of counsel were SARAH J. KALEMERIS,
Marshall, Gerstein & Borun LLP, of Chicago, Illinois, for
Charter Communications Operating LLC, et al; and
JONATHAN B. TROPP, Day Pitney LLP, of Stamford, Con-
necticut, for Sharp Corporation, et al.
                __________________________

Before RADER Chief Judge, O’MALLEY, and REYNA, Circuit
                       Judges.
O’MALLEY, Circuit Judge.
    Rembrandt Technologies, LP and Rembrandt Tech-
nologies, LLC (“Rembrandt”) appeal the district court’s
entry of judgment in favor of the above-captioned defen-
dants (“Defendants”). After the district court construed
the disputed terms of the asserted claims of U.S. Patent
No. 5,243,627 (the “’627 patent”), and in light of the
court’s constructions, Rembrandt and the Defendants
agreed upon a stipulation that disposed of all infringe-
5                           REMBRANDT TECH   v. CABLEVISION

ment claims relating to the ’627 patent. Because we find
that the district court correctly construed the term “signal
point,” we affirm the district court’s entry of judgment.
                       BACKGROUND
                             I.
    The ’627 patent, issued to William Betts and Edward
Zuranski on August 22, 1991, discloses an improvement
to a system and method for transmitting digital data
across high data rate communications networks. Rem-
brandt has accused the Defendants of infringing the ’627
patent by providing services using certain cable modems,
or receiving and transmitting digital broadcast signals,
that comply with the Advanced Television Systems Com-
mittee Digital Television Standard.
    Communications channels used in connection with the
claimed invention carry digital data across large distances
through the use of analog carrier waves. Characteristics
of the carrier wave, such as phase, frequency, or ampli-
tude, are modulated—or altered—such that the transmit-
ted signal represents the digital data input to the system.
As described in more detail below, blocks of bits—referred
to as signal points—correspond to permissible combina-
tions of carrier wave characteristics and are encoded at
the transmitter for transmission on the carrier wave at
successive intervals.      The receiver demodulates and
decodes the received analog signal such that the transmit-
ted digital bits are recovered.
    In the context of the claimed invention, each modu-
lated characteristic represents a dimension of the trans-
mitted signal point. To transmit a particular set of bits,
one inputs those bits into a Quadrature Amplitude Modu-
lation (“QAM”) encoder which outputs values into a
modulator. The modulator then generates a carrier wave
REMBRANDT TECH   v. CABLEVISION                           6

with the characteristics specified by the encoder. The
transmitter sends the wave to the receiver, where the
process used to transmit the signal point is performed in
reverse, interpreting the characteristics of the carrier
wave and from those determining the sent bits:
   Thus referring to FIG. 4, the line signal transmit-
   ted by the transmitter of FIG. 3 is received from
   the channel and applied to demodulator/equalizer
   455 which, in conventional fashion—including an
   input from phase tracking loop 457—generates a
   stream of outputs on lead 456 representing the
   demodulator/equalizer’s best approximation of the
   values of the I and Q components of the signal
   points of the transmitted interleaved signal point
   stream. These outputs are referred to herein as
   the “received signal points.”
’627 patent col. 5 ll. 48-57. Figure 2 of the ’627 patent
shows a representative signal constellation comprised of
signal points, with the axes of the constellation represent-
ing characteristics (referred to as I and Q) of the analog
waveform modulated by the transmitter, and the signal
points on the constellation representing strings of 1s and
0s, or bits.
7                           REMBRANDT TECH    v. CABLEVISION

The signal points shown in Figure 2, e.g. A0, are consid-
ered to be two-dimensional, in reference to the two char-
acteristics, I and Q, represented on the x and y axis. The
parties dispute whether “signal point,” as used in the ’627
patent refers only to two-dimensional signal points such
as those shown in Figure 2, or may include signal points
having only a single dimension.
    Data transmission in the manner described is suscep-
tible to noise bursts which may alter the carrier waves
prior to receipt. “Due to distortion and other channel
impairments that the demodulator/equalizer is not able to
compensate for, the I and Q components of the received
signal points, instead of having exact integer values, can
have any value.” Id. at col. 5 ll. 57-61. This can result in
a received signal being demodulated as a signal point that
does not exist on the signal constellation. Id. at col. 5 ll.
61-64 (“Thus a transmitted signal point having coordi-
nates (3, -5) may be output by the demodulator/equalizer
REMBRANDT TECH   v. CABLEVISION                           8

as the received signal point (2.945, -5.001).). When the
coordinates received are sufficiently close to a permissible
signal point, such as in the example provided, the receiver
may be able to guess the desired signal point correctly. In
many instances, however, the received signal point is too
far from an acceptable point on the constellation that a
guess is impossible and the signal point transmitted is
unrecoverable at the receiver.
     Achieving a high data rate is preferable in these
communication systems, and as data rates approach the
limits of the channel, “various channel impairments,
whose effects on the achievable bit rate were relatively
minor compared to, say, additive white Gaussian noise
and linear distortion, [] become of greater concern.” Id. at
col. 1 ll. 18-22. To compensate for those impairments,
while maintaining high data rates, encoding techniques
have been introduced that separate related data and
permit the recovery of information lost in transmission.
One such technique, trellis encoding, may be used to
assist the receiver in recreating or recovering data lost in
transmission.
    A trellis encoder adds, into each set of data, non-data
redundant bits that are correlated to each other according
to a pattern. The receiver can then use these redundant
bits to determine whether the inserted bits follow the
prescribed pattern. If they do not, the receiver can tell
not only that an error has occurred, but also where the
error has occurred based upon the location of the devia-
tion from the expected pattern of the redundant bits.
Accordingly, trellis encoding is useful for small errors in
transmission that alter the characteristics of the wave,
but it has limited utility in dealing with larger bursts of
noise that disrupt entire sequences.
9                           REMBRANDT TECH    v. CABLEVISION

    In an effort to address the disruptions due to these
larger bursts of noise, Betts, a named inventor of the ’627
patent, filed for U.S. Patent No. 4,677,625 (the “’625
patent”). The ’625 patent, issued on June 30, 1987, ex-
pands on the use of trellis encoding in data communica-
tion systems using two-dimensional signal points selected
by a QAM encoder. Specifically, the patent describes a
system in which “through the use of a distributed trellis
encoder/Viterbi decoder, the effects of many of these
impairments can be reduced.” ’627 patent col. 1 ll. 34-38.
As described in the ’627 patent, the ’625 patent improves
upon the prior art “by distributing the outgoing data to a
plurality of trellis encoders in round-robin fashion and
interleaving the trellis encoder outputs on the transmis-
sion channel.” Id. at col. 1 ll. 59-62. The receiver in the
’625 patent contains a corresponding plurality of trellis
decoders to which the stream of received interleaved
channel symbols is distributed. Id. at col. 1 ll. 62-64.
Thus, each redundant bit inserted by each encoder is
separated from its related redundant bits, increasing the
receiver’s ability to recover channel symbols lost due to
bursts of noise. Id. at col. 1 l. 65–col. 2 l. 2. (“Since the
successive pairs of channel symbols applied to a particu-
lar trellis decoder are separated from one another as they
traverse the channel, the correlation of the noise compo-
nents of these channel symbol pairs is reduced from what
it would have otherwise been.”)
    The improvements claimed in the ’625 patent, how-
ever, failed to achieve the level of error correction re-
quired as demands for greater bit rates increased.
Additional trellis encoders could theoretically enhance the
error correction of the system, but, in the ‘625 patent,
each expansion operation of a trellis encoder selects only
one signal point. Thus, one redundant non-data bit must
be transmitted for every signal point. This limitation
REMBRANDT TECH   v. CABLEVISION                           10

constrains the efficiency of the system and one’s ability to
increase the bitrate. To address this problem, the ’627
patent improves upon a “data communication system
using 2N-dimensional channel symbols” as described in
the ’625 patent. Id. at Abstract. Specifically, Betts
sought to enhance the distributed trellis encoder/Viterbi
decoder technique disclosed in the ’625 patent by combin-
ing it with “a signal point interleaving technique which
causes the constituent signal points of the channel sym-
bols to be non-adjacent as they traverse the channel.” Id.
at col. 2 ll. 11-13. Interleaving is “essentially shuffling
data,” and in the claimed system, the “transmission-
reception system shuffles data, transmits it, and then
reorders the data back to its original order again at the
receiver.” Appellants’ Opening Brief at 20. Thus, inter-
leaving “reduces the effect of bursts of noise during
transmission since any error of discrete duration will be
spread out when the data is reordered at the receiver.”
Id.
    The steps of the claimed invention can be understood
with reference to Figures 3 and 4 of the ’627 patent which
show a block diagram of the transmitter and receiver
sections of a modem embodying the principles of the
invention. Digital data is encoded through trellis encod-
ers 319 and the signal point interleaver 341 to reduce
vulnerability to noise due to the channel medium. The
data is then modulated and transmitted via modulator
328. That analog waveform is received and demodulated
at the receiver such that the original digital data is recov-
ered. Figure 5 of the ’627 patent illustrates both the
deficiencies perceived in the prior art as well as the
claimed improvement. In the examples shown, each
channel symbol is composed of two two-dimensional
signal points that are referred to as a four-dimensional
channel symbol.
11                           REMBRANDT TECH   v. CABLEVISION

     Representative claim 11 of the ’627 patent recites:
     A method for forming a stream of trellis encoded
     signal points in response to input information,
     said method comprising the steps of
     generating a plurality of streams of trellis encoded
     channel symbols in response to respective portions
     of said input information, each of said channel
     symbols being comprised of a plurality of signal
     points, and
     interleaving the signal points of said generated
     channel symbols to form said stream of trellis en-
     coded signal points, said interleaving being car-
     ried out in such a way that the signal points of
     each channel symbol are non-adjacent in said
     stream of trellis encoded signal points and such
     that the signal points of adjacent symbols in any
     one of said channel symbol streams are non-
     adjacent in said stream of trellis encoded signal
     points.
                   II. Procedural History
    This appeal arises out of fifteen separate actions
brought by Rembrandt against the Defendants in various
district courts, alleging infringement of the ’627 patent
and other patents not at issue in this appeal. The Judi-
cial Panel on Multidistrict Litigation centralized all
actions in the District of Delaware before Chief Judge
Gregory M. Sleet. The transferee court grouped the
consolidated actions into two cases for case management
purposes: one relating to the ’627 patent and a second for
the remaining patents. The court then held a Markman
hearing in August, 2008, with a full day devoted to the
REMBRANDT TECH   v. CABLEVISION                        12

’627 patent. 1 On November 7, 2008, the district court
issued an order construing the disputed terms of the ’627
patent. Order Construing the Terms of U.S. Patent No.
5,243,627, In Re: Rembrandt Technologies, LP Patent
Litigation, No. 07-MD-01848, ECF No. 445 (“Claim Con-
struction Order”). In relevant part, the district court
determined that a “signal point” is “a point on a 2-
dimensional constellation having a pair of coordinates
representing two components of a corresponding signal.”
Claim Construction Order at 1.
    Following the entry of the Claim Construction Order,
Rembrandt informed the district court and the Defen-
dants that it wished to stipulate to a judgment of nonin-
fringement of the ’627 patent based solely on the
construction of “signal point” and postpone any further
discovery pending appeal of that construction to this
court. The Defendants agreed that a judgment of nonin-
fringement was appropriate under the construction of
“signal point,” but also sought leave to move for summary
judgment of noninfringement based on the construction of
several other terms. Rembrandt advised the Court that it
would oppose summary judgment with respect to the
terms referred to by the parties as the “trellis encoded
channel symbol,” “stream of trellis encoded channel
symbols,” and “intedeaving/deinterleaving” limitations.
On May 28, 2009, the district court granted the Defen-
dants’ motion for leave and, on July 21, 2009, the Defen-
dants moved for summary judgment of noninfringement.

   1     A Markman hearing was held in one of the prior
actions, Rembrandt Technologies, LP. v. Comcast Corp. et
al., Civ. No. 2:05-CV-443 (E.D. Tex.), construing the ’627
patent. The Texas district court issued an opinion and
order construing the phrase “signal point,” but that
construction was vacated by the transferee court when
the various actions were consolidated before it.
13                          REMBRANDT TECH   v. CABLEVISION

In opposition, Rembrandt agreed that the district court
should enter summary judgment of noninfringement
based on the construction of “signal point,” but argued
that the Defendants failed to carry their burden of show-
ing that no genuine dispute existed on the other limita-
tions, as construed by the district court.
    After considering the Defendants’ motion, the district
court determined that numerous disputed material facts
raised genuine issues for trial as to the Defendants’
alternative grounds for finding noninfringement. The
parties thereafter agreed upon a Stipulation for Entry of
Final Judgment and Order, based on the construction of
“signal point,” that disposed of all infringement claims
relating to the ’627 Patent. The district court entered the
Stipulation for Entry of Final Judgment and Order on
September 7, 2011. Rembrandt timely appealed and we
have jurisdiction pursuant to 28 U.S.C. § 1295(a)(1).
                       DISCUSSION
     On appeal, Rembrandt asserts error in the district
court's construction of the terms “signal point,” “stream of
trellis encoded channel symbols,” and “trellis encoded
channel symbol . . . comprised of a plurality of signal
points.” The Defendants argue that the district court
correctly construed the terms at issue and that the con-
structions of “stream of trellis encoded channel symbols”
and “trellis encoded channel symbol . . . comprised of a
plurality of signal points” provide alternative grounds for
affirming summary judgment of noninfringement. Find-
ing no error with the district court’s construction of “sig-
nal point,” we do not address either the remaining
constructions or the Defendants’ alternative arguments.
REMBRANDT TECH   v. CABLEVISION                           14

                             I.
    This court reviews a district court’s claim construction
de novo. Cybor Corp. v. FAS Techs. Inc., 138 F.3d 1448,
1453 (Fed. Cir. 1998) (en banc). To ascertain the scope
and meaning of the asserted claims, we look to the words
of the claims themselves, the specification, the prosecu-
tion history, and any relevant extrinsic evidence. Phillips
v. AWH Corp., 415 F.3d 1303, 1315–17 (Fed. Cir. 2005)
(en banc). As a general rule, a claim term is given its
plain and ordinary meaning as understood by a person of
ordinary skill in the art at the time of invention. Id. at
1312-13. Although claim construction begins with the
language of the claims themselves, the claims “must be
read in view of the specification, of which they are a part.”
Markman v. Westview Instruments, Inc., 52 F.3d 967, 979
(Fed. Cir. 1995) (en banc). Indeed, the specification “is
the single best guide to the meaning of a disputed term”
and it “acts as a dictionary when it expressly defines
terms used in the claims or when it defines terms by
implication.” Phillips, 415 F.3d at 1321 (quoting Vitronics
Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582 (Fed. Cir.
1996)).
    Similarly, we review the grant of summary judgment
without deference. Dynacore Holdings Corp. v. U.S.
Philips Corp., 363 F.3d 1263, 1273 (Fed. Cir. 2004).
Summary judgment is appropriate if no genuine issues of
material fact exist such that the moving party is entitled
to judgment as a matter of law. Fed. R. Civ. P. 56(c); see
also Ethicon Endo-Surgery, Inc. v. U.S. Surgical Corp.,
149 F.3d 1309, 1315 (Fed. Cir. 1998). This court reviews
the evidence in the light most favorable to the non-moving
party. Anderson v. Liberty Lobby, Inc., 477 U.S. 242, 255
(1986).
15                          REMBRANDT TECH   v. CABLEVISION

                            II.
    We begin by addressing the district court’s construc-
tion of the disputed term “signal point” as “a point on a 2-
dimensional constellation having a pair of coordinates
representing two components of a corresponding signal.”
Claim Construction Order at 1. Rembrandt presents two
primary arguments against the district court’s construc-
tion: (1) neither the claims nor the specification limit a
signal point to two dimensions, or, conversely, the plain
language of the claims and specification permits any
dimensionality; and (2) claim differentiation requires that
no limit be placed on dimensionality. 2
    Rembrandt first argues that the court’s construction
is inconsistent with the plain meaning of the term be-
cause there is no language in claims 11 and 19 that
references a specific signaling scheme or constellation,
and that Defendants’ own expert agreed that it is possible
to have a one-dimensional signal point. According to
Rembrandt, moreover, limiting “signal point” to a two-
dimensional coordinate contradicts the express statement

     2  Defendants argue that Rembrandt proposed a
specific construction of signal point at the Markman
hearing, and cannot now rely on plain and ordinary
meaning after conceding that the term required construc-
tion. Defendants also contend that, by presenting a
different construction on appeal, Rembrandt waived its
ability to challenge the district court’s construction.
“[P]resenting proposed claim constructions which alter
claim scope for the first time on appeal invokes the doc-
trine of waiver as to the new claim constructions.” NTP,
Inc. v. Research In Motion, Ltd., 418 F.3d 1282, 1296
(Fed. Cir. 2005) (citations omitted). Because we find that
the district court correctly construed “signal point,” how-
ever, we need not determine whether Rembrandt presents
a new construction on appeal or opine on the effect of any
waiver that may have occurred.
REMBRANDT TECH    v. CABLEVISION                            16

in the specification that “the invention can be used with
signaling schemes of any dimensionality.” Appellant’s
Opening Brief at 36 (quoting the ’627 patent col. 8 ll. 59-
61). Rembrandt asserts that the two-dimensional em-
bodiment described in the specification is merely illustra-
tive and represents one possible embodiment.
     While the Defendants admit that one-dimensional
signal points are conceivable in the abstract, they assert
that, in the context of the ’627 patent, signal points exist
only as points on a two-dimensional constellation. In-
deed, Defendants argue that the ’627 patent unambigu-
ously refers to the invention as an improvement on an
existing system—as described in the ’625 patent—using
only two-dimensional signal point constellations, and that
all references within the specification are consistent with
that understanding. Accordingly, the reference to “any
dimensionality” refers not to the dimensionality of the
signal points themselves, but rather to the channel sym-
bols. See, e.g., ’627 patent at col. 4 ll. 54-56 and col. 8 ll.
23-26 (illustrating embodiments with four and eight
dimensions, respectively). We agree.
    A “person of ordinary skill in the art is deemed to read
the claim term not only in the context of the particular
claim in which the disputed term appears, but in the
context of the entire patent, including the specification.”
Phillips, 415 F.3d at 1313. Here, the Abstract and Sum-
mary of the Invention make clear that the claimed inven-
tion is an improvement on the system described in the
’625 patent which utilizes only two-dimensional signal
point constellations. As stated in the Summary, “[i]n
accordance with the present invention, performance in a
data communication system using 2N-dimensional chan-
nel symbols can be further enhanced by an interleaving
technique . . . .” ’627 patent col. 2 ll. 5-9. The parties do
not dispute that “2N-dimensional channel symbol" refers
17                             REMBRANDT TECH   v. CABLEVISION

to a variable number (N) of two-dimensional signal points
per channel symbol. Oral Arg. at 00:31, available at
http://www.cafc.uscourts.gov/oral-argument-
recordings/2012-1022/all.      And this understanding is
clearly set forth in the specification:
     Note    that,    implementationally,     the   2N-
     dimensional channel symbol is generated by hav-
     ing the trellis encoder identify, interdependently,
     N subsets of the two-dimensional constellation of
     FIG. 2, then select a two-dimensional signal point
     from each of the subsets thus identified. The con-
     catenation of the N two-dimensional signal points
     thus selected is the desired 2N-dimensional chan-
     nel symbol.
’627 patent col. 4 ll. 4-11.
     Moreover, every contemplated embodiment flows from
the general two-dimensional scheme, varying the value of
N to permit “signaling schemes of any dimensionality.”
See, e.g., ’627 patent col. 3 ll. 19-20 (“N=I, i.e., a two-
dimensional signaling scheme . . .”); id. at col. 4 ll. 54-56
(“four-dimensional, i.e., N=2, signaling scheme . . .”); id. at
col. 8 ll. 57-67 (comparing the general, 2N-dimensional,
case to the “four-dimensional signaling scheme” of “the
illustrative embodiment”); id. at col. 9 ll. 8-13 (“when
dealing with 2N-dimensional signaling where N>2, it is
necessary to add additional delay elements to the signal
point interleaver/deinterleaver . . .”); id. at col. 9 ll. 14-15
(“N=4, i.e., an eight dimensional case . . . .”). We see no
indication that the patentee contemplated anything other
than a specific improvement to the system described in
the ’625 patent or claimed a deviation from the two-
dimensional signal constellation set forth in Figure 2 of
the specification.
REMBRANDT TECH   v. CABLEVISION                         18

    Rembrandt contends that these descriptions of the
embodiments are insufficient to limit the ’627 patent to
two-dimensional signal points. But Rembrandt points
only—and repeatedly—to the phrase “signaling schemes
of any dimensionality” as justification for broadening the
scope of the ’627 patent to include one-dimensional signal
points. This reliance is misplaced. Properly understood
in the context of the ’627 patent and the surrounding
sentences, the phrase on which Rembrandt relies merely
relates to the variable N and the contemplation of N two-
dimensional signal constellations.
    Rembrandt correctly highlights our repeated warn-
ings against confining claims to a particular embodiment
and the need to avoid importing limitations from the
specification into the claims. Phillips, 415 F.3d at 1323.
Generally, a claim is not limited to the embodiments
described in the specification unless the patentee has
demonstrated a clear intention to so limit the claim’s
scope. i4i Ltd. P’ship v. Microsoft Corp., 598 F.3d 831,
843 (Fed. Cir. 2010). But this concern is tempered by the
consideration that “[a]n inventor is entitled to claim in a
patent what he has invented, but no more.” MySpace,
Inc. v. Graphon Corp., 672 F.3d 1250, 1256 (Fed. Cir.
2012). A determination of what was invented requires
examination of the entire patent with particular focus on
the specification. Id. For example, in MySpace, Inc., we
declined to read a preferred embodiment into the claims
and found that the specification was “devoid of a clear
indication that the invention should be limited to one
particular type of database . . . .” 672 F.3d at 1257.
Similarly, in Symantec Corp. v. Computer Associates
International, Inc., 522 F.3d 1279, 1290-1291 (Fed. Cir.
2008), we determined that the district court unduly
limited the scope of the claims to a single personal com-
puter because the specification failed to expressly define
19                             REMBRANDT TECH     v. CABLEVISION

the relevant terms nor did it suggest that it had adopted a
special definition.
    Where the specification clearly limits the invention to
a particular form, however, it is appropriate to construe
the claims consistently with that limitation. In Edwards
Lifesciences LLC v. Cook Inc., 582 F.3d 1322, 1329 (Fed.
Cir. 2009), after examination of the specification, we
limited the claimed graft devices as intraluminal. We
explained that, “when the preferred embodiment is de-
scribed in the specification as the invention itself, the
claims are not necessarily entitled to a scope broader than
that embodiment.” Edwards, 582 F.3d at 1329 (citing
Chimie v. PPG Indus. Inc., 402 F.3d 1371, 1379 (Fed. Cir.
2005)); see also Honeywell Int’l, Inc. v. ITT Indus., Inc.,
452 F.3d 1312, 1318 (Fed. Cir. 2006) (holding that the
claims were limited to fuel filters, despite the fact that the
claims contained no fuel filter limitation, because “[o]n at
least four occasions, the written description refers to the
fuel filter as ‘this invention’ or ‘the present invention. . . . ’
”). Here, the ’627 patent repeatedly refers to the “present
invention” as a specific improvement on a known system
and as limited to using two-dimensional signal points.
The specification clearly defines the dimensionality of
signal point and contemplates no variation on that sys-
tem. Accordingly, Rembrandt is incorrect that the district
court imported a limitation from the specification in its
construction of signal point.
     Finally, Rembrandt argues that the doctrine of claim
differentiation requires a construction of signal point
without a dimensional limitation. Rembrandt notes that
independent claim 15 specifically recites a “2N-
dimensional constellation,” while independent claim 11
includes no such limitation. Similarly, claim 13 recites
“[t]he method of claim 11 wherein said channel symbols
REMBRANDT TECH   v. CABLEVISION                          20

are 2N-dimensional channel symbols, N>1.” ’627 patent
col. 11 ll. 65-67.
     The doctrine of claim differentiation stems from “the
common sense notion that different words or phrases used
in separate claims are presumed to indicate that the
claims have different meanings and scope.” Seachange
Int’l, Inc. v. C-COR Inc., 413 F.3d 1361, 1368-1369 (Fed.
Cir. 2005) (quoting Karlin Tech. Inc. v. Surgical Dynam-
ics, Inc., 177 F.3d 968, 971-72 (Fed. Cir. 1999)). Although
the doctrine is at its strongest “where the limitation that
is sought to be ‘read into’ an independent claim already
appears in a dependent claim,” Liebel-Flarsheim Co. v.
Medrad, Inc., 358 F.3d 898, 910 (Fed. Cir. 2004), there is
still a presumption that two independent claims have
different scope when different words or phrases are used
in those claims. Kraft Foods, Inc. v. Int’l Trading Co., 203
F.3d 1362, 1365-69 (Fed. Cir. 2000); see also Tandon Corp.
v. U.S. Int’l Trade Comm'n, 831 F.2d 1017, 1023 (Fed.
Cir. 1987). The doctrine is not a hard and fast rule,
however; it “only creates a presumption that each claim in
a patent has a different scope” and “the written descrip-
tion and prosecution history [may] overcome any pre-
sumption arising from the doctrine of claim
differentiation . . . .” Kraft, 203 F.3d at 1368 (internal
quotations omitted); see also Edwards Lifesciences, 582
F.3d at 1331.
     There is no reason to apply the doctrine of claim dif-
ferentiation, however, where, as here, the district court’s
construction does not render any claim redundant or
superfluous. Andersen Corp. v. Fiber Composites, LLC,
474 F.3d 1361, 1370 (Fed. Cir. 2007). Claims 15 and 13
both add limitations not found in claim 11, namely “divid-
ing said stream of input bits” and “selecting an individual
channel symbol” in claim 15 and “said interleaving step
[of claim 11] causes every Nth signal point in said inter-
21                          REMBRANDT TECH   v. CABLEVISION

leaved signal point stream to be the Nth signal point of a
respective one of said channel symbols” in claim 13. ’627
patent col. 11 l. 40-col. 12 l. 35. The claims thus have a
different scope under the district court’s construction and
Rembrandt’s reliance on claim differentiation is mis-
placed.
    Even assuming that the claims, as construed by the
district court, “cover substantially the same subject
matter . . . overlapping patent claims are not unusual,
and the overlap does not require us to construe” signal
point as including one-dimensional signal points. See
Andersen Corp., 474 F.3d at 1370. Ultimately, “the doc-
trine of claim differentiation can not broaden claims
beyond their correct scope, determined in light of the
specification and the prosecution history and any relevant
extrinsic evidence.” Multiform Desiccants, Inc. v. Medzam
Ltd., 133 F.3d 1473, 1480 (Fed. Cir. 1998).
    There is, moreover, a practical reason why claims 13
and 15 recite “wherein said channel symbols are 2N-
dimensional channel symbols” and “2N-dimensional
constellation,” respectively, while claim 11 does not. Each
claim includes the additional restriction that the variable
N have a value greater than one. Absent use of the
language “2N-dimensional,” these limitations on the
variable N would lack antecedent basis.
                       CONCLUSION
    The district court correctly construed “signal point” as
“a point on a 2-dimensional constellation having a pair of
coordinates representing two components of a correspond-
ing signal.” We see nothing in the ’627 patent that is
directed towards anything other than an improvement on
the system described in the ’625 patent or is not limited to
a two-dimensional signaling scheme. Because Rembrandt
admits that Defendants do not infringe under that con-
REMBRANDT TECH   v. CABLEVISION                       22

struction, affirming the judgment below is appropriate on
that basis alone. We do not reach the parties’ remaining
arguments and express no opinion on the other construc-
tions entered by the district court.
                      AFFIRMED
                          COSTS
   Each party shall bear its own costs.