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                                                                   EXHIBIT 10.52

CONFIDENTIAL PORTIONS OF THIS DOCUMENT HAVE BEEN REDACTED AND SEPARATELY FILED
WITH THE COMMISSION.

                      AMENDMENT TO PATENT LICENSE AGREEMENT

THIS AMENDMENT TO THE PATENT LICENSE AGREEMENT dated May 8, 1995, is entered
into this 15th day of January 2002 ("Effective Date") between InterDigital
Technology Corporation ("ITC"), a Delaware corporation with a mailing address of
[**], Wilmington, DE 19801, and NEC Corporation ("Licensee"), a company
organized and existing under the laws of Japan, with a mailing address [**],
Japan.

                                    PREAMBLE

WHEREAS, ITC and Licensee are parties to an existing Patent License Agreement,
dated May 8, 1995, covering certain TDMA-based products manufactured and sold by
Licensee (the "Prior Agreement");

WHEREAS, a substantial dispute (the "Dispute") has arisen between Licensee and
ITC as to whether royalties are owed by Licensee for its sale in Japan of
Covered Infrastructure Equipment/1/ and Covered Subscriber Units compliant with
PHS and PDC Covered Standards;

WHEREAS, the parties have engaged in both a mediation and an arbitration dispute
resolution process pursuant to the Prior Agreement with respect to such dispute,
and are desirous of settling the dispute amicably;

WHEREAS, the parties have agreed upon a settlement of the dispute, wherein the
settlement provides:(i) for certain amendments to the Prior Agreement, the
principal amendment providing for certain payments to ITC in lump sum amounts in
exchange for a paid-up license for Covered Subscriber Units and Covered
Infrastructure Equipment compliant with PHS and PDC Covered Standards, and (ii)
for a new license agreement

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/1/ Capitalized terms undefined herein shall have the meaning ascribed to them
in the Prior Agreement.

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involving Covered Subscriber Units and Covered Infrastructure Equipment
compliant with Narrowband CDMA and Third Generation (as defined in such new
agreement) ("3G Agreement"); and

WHEREAS, the lump sum amounts provided for under the settlement referenced
herein are based upon the existing rights and obligations of the parties under
the Prior Agreement, including without limitation the [**] provision of Section
7(g) of the Prior Agreement.

NOW, THEREFORE, in consideration of the mutual promises contained herein, and
intending to be legally bound, the parties agree as follows:

     1.   Paid Up License for PHS and PDC. Licensee irrevocably and
          unconditionally agrees to pay to ITC the non-refundable lump sum
          amount of $53,000,000. Payment of such amount shall be made on the
          following installment basis by wire transfer to ITC's bank account to
          be designated by ITC in advance:

            .  On or before April 10, 2002:           $US 13,250,000
            .  On or before December 31, 2002         $US 13,250,000
            .  On or before April 10, 2003            $US 13,250,000
            .  On or before December 31, 2003         US$ 13,250,000

          In consideration of such payment and in recognition of the fact that
          the $26,939,280 was previously paid under the Prior Agreement, the
          license granted under Section 2 of the Prior Agreement, with respect
          to Covered Subscriber Units and Covered Infrastructure Equipment
          compliant with PHS and/or PDC Covered Standards ("Covered PHS/PDC
          Products"), shall be considered fully paid up and irrevocable and
          shall survive any termination of the Prior Agreement; provided,
          however, that the royalty obligation as regards

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          any Covered PHS/PDC Products also compliant with Third Generation or
          Narrowband CDMA (each as defined in the 3G Agreement) shall be
          determined in accordance with the terms of the 3G Agreement. In
          addition, with respect to any other Covered Subscriber Unit or Covered
          Infrastructure Equipment also compliant with Third Generation or
          Narrowband CDMA (e.g., GSM/FDD Covered Subscriber Unit), no royalty
          shall be payable under the Prior Agreement for such other product, so
          long as Licensee has paid, or is to pay, a royalty in accordance with
          the terms of the 3G Agreement with respect to such other Covered
          Subscriber Unit or Covered Infrastructure Equipment. Licensee may
          deduct applicable Japanese source withholding taxes from the payments
          hereunder, it being understood that both parties agree that the entire
          amount of US$53,000,000 is subject to the Japanese source withholding
          taxes. Licensee shall furnish ITC with the evidence that any such
          withholding tax has been paid.

          It is understood that if the Prior Agreement is substituted at
          Licensee's election by another patent license agreement as a result of
          the operation of the most favored licensee rights provisions of the
          Prior Agreement, any royalty obligation under such substitute
          agreement relating to Covered Subscriber Units and Covered
          Infrastructure Equipment compliant with only PHS and PDC shall not
          apply.

     2.   (Reserved).

     3.   Infrastructure. With regard to Infrastructure Equipment compliant with
          GSM and IS-54/136, Licensee agrees to pay ITC a royalty of [**]% of
          the Net Selling Price of each such sale, if any, of said
          Infrastructure Equipment from May 8, 1995 through December 31, 2006.
          Such royalty payments shall be made on each such sale, if any, by
          Licensee or its Affiliates anywhere in the

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          world, without regard to the provisions of Section 5(c) or Section 7
          (other than Section 7(e)(iv)) of the Prior Agreement. Thereafter, any
          royalty obligations with regard to such Infrastructure Equipment shall
          be governed by the terms of the Prior Agreement.

     4.   Meaning of Paragraphs 5(c)(ii) and (iii) of Prior Agreement. The
          parties agree that, as used in Paragraphs 5(c) (ii) and (iii) of the
          Prior Agreement, the clause "but only if said counterpart contains
          claims which do not differ materially from those of the [**] Patent"
          shall in each occurrence, for the purpose of settlement, be hereafter
          deemed to refer to substantial differences between the issued non-U.S.
          patent claim(s), which issue from non-U.S. [**] patent applications
          that share a common specification with the U.S. patent, and Licensee's
          products compliant with a Covered Standard, such that infringement of
          such non-U.S. claims cannot be found. The parties further agree that,
          based on the audit conducted as part of the Dispute, Licensee has
          correctly accounted for use of the pre-paid units, including the
          application of credits under the [**] clause of the Prior Agreement,
          and that such credits shall continue to be available to Licensee with
          regard to its royalty obligations under the Prior Agreement.

     5.   Adjustment.
          (1) If, after the Effective Date of this Amendment Agreement,
              Licensee or its Affiliates acquires any entity which, prior to
              such acquisition, sold PDC or PHS Covered Subscriber Units or
              Covered Infrastructure Equipment without a license from ITC for
              the Licensed Patents, then Licensee shall pay ITC royalties of
              (i) $[**] for each PDC Covered Subscriber Unit and PHS Covered
              Subscriber Unit, and (ii) [**]% of the Net Selling Price of PDC
              or PHS Covered Infrastructure Equipment sold by such entity prior
              to such acquisition by Licensee; provided, however, that if such

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              acquisition occurs later than twelve (12) months after the
              Effective Date of this Amendment, Licensee shall have the option,
              to be exercised via written notice to ITC within sixty (60) days
              of the completion date of such acquisition, to have such sales be
              construed as unlicensed. In such situation, ITC shall have
              recourse to seek damages and/or royalties from any entity,
              including Licensee or its Affiliates, against whom legal action
              may be brought. In addition, provided such entity, at the time of
              being acquired by Licensee, had annual sales of PDC and/or PHS
              Covered Subscriber Units in excess of [**] units, in the
              aggregate, or had annual sales of PDC or PHS Covered
              Infrastructure Equipment of [**] U.S Dollars ($US [**]), the
              parties shall negotiate in good faith an equitable adjustment to
              the lump sum amount provided in Article 1 herein for sales after
              the date of the acquisition, provided that in lieu of adjustment
              to the lump sum amount provided in Article 1 herein, Licensee
              shall have the option to pay royalties to ITC at the royalty rates
              provided for in (i) and (ii) above with respect to PDC or PHS
              Covered Subscriber Units or Covered Infrastructure Equipment sold
              by, or ascribed to, the acquired entity after the date of the
              acquisition. Such negotiated adjustment amount will be based upon
              the ratio of Licensee and its Affiliates' total sales of the PDC
              and PHS Covered Subscriber Units and Covered Infrastructure
              Equipment from the period January 1, 1995 through December 31,
              2001 and the acquired entities sales of the PDC and PHS Covered
              Subscriber Units and Covered Infrastructure Equipment over the
              same period, less any royalties, if any, paid by Licensee for
              sales by the acquired entity prior to the date of acquisition
              pursuant to the first sentence of this Article 5. Any dispute as
              to the adjustment amount owed shall be made subject to resolution
              under the Dispute Resolution Procedures of the Prior Agreement.
              The parties shall also negotiate such an adjustment amount if
              Licensee acquires, over time, a number of

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              entities, such that, in the aggregate, there existed annual sales
              of at least [**] Covered Subscriber Units or [**] U.S Dollars
              ($[**] US) of Covered Infrastructure revenue at the time of being
              acquired by Licensee. Sales by the acquired entities of non-PDC
              and non-PHS Covered Subscriber Units and Covered Infrastructure
              Equipment after the time of being acquired by Licensee, shall be
              controlled by the Prior Agreement. For sales by the acquired
              entities of non-PDC and non-PHS Covered Subscriber Units and
              Covered Infrastructure Equipment prior to the time of being
              acquired by Licensee, then Licensee shall pay ITC royalties of (i)
              $[**]US for each non-PDC Covered Subscriber Unit and non-PHS
              Covered Subscriber Unit, and (ii) [**]% of the Net Selling Price
              of non-PDC or non-PHS Covered Infrastructure Equipment; provided,
              however, that if such acquisition occurs later than twelve (12)
              months after the Effective Date of this Amendment, Licensee shall
              have the option, to be exercised via written notice sent to ITC
              within sixty (60) days of the conclusion date of such acquisition,
              to have such sales be construed as unlicensed.

          (2) To the extent Licensee or its Affiliates acquires an entity
              already licensed by ITC to the Licensed Patents, for the first
              twelve (12) months after the acquisition, the royalty obligation
              of such entity for royalty obligated sales volumes related to such
              entity shall be defined in such other license agreement with ITC.
              After the 12 month period, royalty obligations for all PDC and PHS
              Covered Subscriber Units and Covered Infrastructure Equipment
              sales made by, or ascribed to, the previously licensed acquired
              entity shall be determined as set forth in paragraph (1) above (as
              for unlicensed entities, either as an adjustment to the lump sum
              or running royalties, at Licensee's option); and royalty
              obligations for all non-PDC and non-PHS Covered Subscriber Units
              and Covered Infrastructure Equipment sales made by, or ascribed
              to, the previously licensed acquired

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              entity after such acquisition shall be controlled by the terms of
              the Prior Agreement.

          (3) The above paragraphs (1) and (2) shall not apply in cases Licensee
              or its Affiliates acquires Licensee or any entity which is already
              Licensee's Affiliates at the time immediately prior to the
              acquisition.

     6.   Confidentiality/Press Release. Unless otherwise required by law,
          government regulations, stock exchange listing rules or court order,
          the parties shall maintain as strictly confidential the royalty terms
          of this Amendment Agreement and any proprietary information disclosed
          under, or as a result of the negotiation of, this Amendment Agreement,
          provided that each party may disclose in confidence the royalty terms
          to (i) its outside counsel or accountant, or (ii) its financial
          advisors or prospective acquiring or acquired entity in connection
          with its prospective M&A transactions. Further, ITC and/or IDC may
          issue a press release having the content shown in Exhibit 1, attached
          hereto. Licensee may also issue a press release regarding the fact of
          the execution of this Amendment Agreement and the settlement of the
          arbitration. To the extent ITC and/or IDC desires to modify an agreed
          upon press release, or Licensee desires to issue a press release, such
          desiring party shall provide the other party with an advance copy of
          its respective proposed press release for review, consent and comment;
          whereby consent by the other party shall not be unreasonably withheld
          or delayed.

     7.   Prior Agreement. Except as provided herein, all other terms and
          conditions of the Prior Agreement remain unaltered and in full force
          and effect.

                          Signatures on following page.

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IN WITNESS WHEREOF, the parties have executed this Agreement by their duly
authorized representatives.

INTERDIGITAL TECHNOLOGY CORPORATION

By: /s/ William J. Merritt
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Dated: January 14, 2002
      ---------------------------------


NEC CORPORATION

By: /s/ [**]
   ------------------------------------

Dated: January 15, 2002
      ---------------------------------

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                                Index of Exhibits

EXHIBIT 1:     PRESS RELEASE

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