DCT

3:25-cv-02680

Fractus SA v. ResMed Inc

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Amended Complaint
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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 3:25-cv-02680, S.D. Cal., 09/02/2026
  • Venue Allegations: Venue is based on Defendant's alleged residence and regular and established place of business within the Southern District of California, including corporate offices in San Diego, and the commission of infringing acts within the district.
  • Core Dispute: Plaintiff alleges that Defendant's wirelessly-enabled medical devices, such as CPAP machines, infringe five patents related to miniature, multi-band, and high-isolation internal antenna technologies.
  • Technical Context: The technology concerns advanced antenna designs that enable compact wireless devices to operate efficiently across multiple frequency bands, a critical feature for modern electronics with integrated connectivity.
  • Key Procedural History: The complaint alleges that Plaintiff first provided Defendant with notice of the patents-in-suit in June 2021. The parties engaged in correspondence through 2021 and 2022, during which Plaintiff offered to provide infringement claim charts under a non-disclosure agreement, which Defendant allegedly declined. This history may be relevant to the allegations of willful infringement.

Case Timeline

Date Event
2003-02-19 '349 Patent Priority Date
2004-01-30 '365 Patent Priority Date
2004-01-30 '887 Patent Priority Date
2005-07-21 '960 Patent Priority Date
2005-07-21 '458 Patent Priority Date
2013-01-29 '960 Patent Issue Date
2013-06-04 '365 Patent Issue Date
2013-11-26 '349 Patent Issue Date
2014-03-18 '887 Patent Issue Date
2014-08-19 '458 Patent Issue Date
2021-06 Fractus sends initial notice letter to Resmed
2022-11 Fractus sends additional notice to Resmed
2026-09-02 Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 8,456,365 - "Multi-Band Monopole Antennas for Mobile Communications Devices"

The Invention Explained

  • Problem Addressed: The patent addresses the challenges of designing small, internal antennas for mobile devices that can operate efficiently across multiple frequency bands without performance being significantly impaired by neighboring electronic components within the device's cramped confines Compl. p. 5 ¶¶1-9 '677 Patent, col. 1:40-62
  • The Patented Solution: The invention proposes a multi-band monopole antenna comprising multiple radiating arms connected to a common conductor, with at least one arm being partially shaped according to a "grid-dimension curve" and with portions of the arms arranged on different planes '365 Patent, abstract '365 Patent, col. 2:24-40 This geometric complexity allows the antenna to achieve multi-band performance in a compact, three-dimensional form factor suitable for integration into small devices '365 Patent, col. 2:41-53
  • Technical Importance: This approach enabled the integration of complex, multi-band antennas directly into the housing of wireless devices, facilitating the trend toward smaller, more functional products without sacrificing wireless performance Compl. ¶14

Key Claims at a Glance

  • The complaint asserts independent claim 1 Compl. ¶29
  • Essential elements of claim 1 include Compl. ¶28:
    • A mobile communication device comprising a device housing, a printed circuit board (PCB) with a ground plane and communication circuitry.
    • A multi-band antenna inside the housing, which includes an antenna element operating in cooperation with the ground plane.
    • The antenna element comprises a common conductor and first and second radiating arms.
    • The common conductor includes a feeding port coupled to a feeding point on the PCB.
    • At least a portion of the first and second radiating arms are arranged on different planes.
    • The first radiating arm is at least partially shaped according to a grid-dimension curve.
  • The complaint does not explicitly reserve the right to assert dependent claims, though this is standard litigation practice.

U.S. Patent No. 8,674,887 - "Multi-Band Monopole Antenna for a Mobile Communications Device"

The Invention Explained

  • Problem Addressed: The patent addresses the need for miniature multi-band antennas that can be effectively integrated into mobile devices while maintaining performance, a persistent challenge in wireless device design '887 Patent, col. 1:17-38
  • The Patented Solution: The invention describes a multi-band antenna secured to a mounting structure within a device, where at least part of a radiating arm is shaped as a "space-filling curve." This curve is defined by a specific set of geometric rules, including comprising at least ten connected segments shorter than a tenth of the operating wavelength, with no two adjacent segments forming a longer straight line '887 Patent, abstract '887 Patent, col. 2:50-67 This technique allows a physically short conductor to behave as an electrically longer one, enabling miniaturization.
  • Technical Importance: The use of space-filling curves provided a method to significantly reduce the physical size of antennas required for lower frequency bands (such as cellular bands), which was a key enabler for smaller and more integrated handheld devices Compl. ¶14

Key Claims at a Glance

  • The complaint asserts independent claim 1 Compl. ¶40
  • Essential elements of claim 1 include Compl. ¶39:
    • A mobile communication device with communications circuitry and a circuit board having a ground plane.
    • A mounting structure positioned within the device.
    • A multi-band antenna secured to the mounting structure, comprising a common conductor with first and second radiating arms.
    • A "space-filling curve" constituting at least part of the first radiating arm.
    • The space-filling curve is defined by a series of geometric constraints, including having "at least ten segments that are shorter than a tenth of a free-space operating wavelength" and being connected at angles such that "no pair of adjacent segments defines a longer straight segment."
  • The complaint does not explicitly reserve the right to assert dependent claims.

U.S. Patent No. 8,593,349 - "Miniature Antenna Having a Volumetric Structure"

  • Technology Synopsis: The patent describes a miniature antenna system where the perimeter of a radiating arm defines a "grid dimension curve" '349 Patent, abstract The technology uses specific mathematical properties of the antenna's shape (a non-periodic curve with a grid dimension greater than 1.3) and a non-planar structure to achieve miniaturization and functionality in wireless devices Compl. ¶50
  • Asserted Claims: The complaint asserts claim 15 Compl. ¶51
  • Accused Features: The antenna systems within the Resmed AirCurve 10, AirSense 10, and Connectivity Module products are accused of infringement Compl. ¶51

U.S. Patent No. 8,362,960 - "Handheld Device with Two Antennas, and Method of Enhancing the Isolation Between the Antennas"

  • Technology Synopsis: This patent addresses the problem of interference between multiple antennas in a single device. It claims a specific geometric layout for a handheld device with two antennas on a "substantially rectangular ground plane," where the antennas extend in directions "substantially parallel" to "substantially orthogonal" sides of the ground plane, enhancing electrical isolation between them Compl. ¶61
  • Asserted Claims: The complaint asserts claim 1 Compl. ¶62
  • Accused Features: The antenna systems within the Resmed AirCurve 11 and AirSense 11 products are accused of infringement Compl. ¶62

U.S. Patent No. 8,810,458 - "Handheld Device with Two Antennas, and Method of Enhancing the Isolation Between the Antennas"

  • Technology Synopsis: Similar to the '960 Patent, this invention also concerns enhancing isolation between two antennas in a wireless device. It claims a specific arrangement where a first multi-band antenna and a second single-band antenna are located internally and extend parallel to different sides of a rectangular ground plane, with the first antenna being "substantially close to the first side" Compl. ¶72
  • Asserted Claims: The complaint asserts claim 1 Compl. ¶73
  • Accused Features: The antenna systems within the Resmed AirCurve 11 and AirSense 11 products are accused of infringement Compl. ¶73

III. The Accused Instrumentality

Product Identification

  • The accused instrumentalities are the Resmed AirSense 10, Resmed AirCurve 10, Resmed Connectivity Module, Resmed AirSense 11, and Resmed AirCurve 11 products (collectively, the "Infringing Products") Compl. ¶15

Functionality and Market Context

  • The accused products are medical devices (CPAP machines) that provide "built-in wireless connectivity, including for remote monitoring and management" Compl. ¶15 This wireless functionality is alleged to be "central to the health benefits and commercial value of the Infringing Products" Compl. ¶15
  • The complaint provides teardown photographs of the Resmed AirCurve 10, which show a printed circuit board containing a Taoglas antenna module allegedly implementing the patented technology Compl. pp. 9-12 An annotated photograph of the Resmed AirCurve 10's internal components identifies the device housing, printed circuit board, communication circuitry, and antenna Compl. p. 9 Similarly, teardown photos of the Resmed AirCurve 11 show a printed circuit board with a first antenna for mobile communication services and a second antenna for Bluetooth connectivity Compl. p. 28

IV. Analysis of Infringement Allegations

'365 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A mobile communication device, comprising: a device housing; a printed circuit board, the printed circuit board comprising: a ground plane layer; a feeding point; a communication circuitry... The Resmed AirCurve 10 is alleged to be a mobile communication device containing a device housing, a PCB with a ground plane, and communication circuitry. ¶30a col. 2:24-31
a multi-band antenna capable of operating at multiple frequency bands, the multi-band antenna including an antenna element; wherein the antenna element operates in cooperation with the ground plane layer; The accused product's antenna allegedly operates in multiple frequency bands (including GSM 850/1900 and various LTE bands) in cooperation with the PCB's ground plane. ¶30b col. 2:32-35
the antenna element comprising: a common conductor; a first radiating arm connected to the common conductor; a second radiating arm connected to the common conductor; wherein the common conductor includes a feeding port, the feeding port being coupled to the feeding point; The accused antenna allegedly includes a common conductor with first and second radiating arms, and a feeding port coupled to the PCB's feeding point. ¶30c col. 2:36-40
wherein at least a portion of the first radiating arm and at least a portion of the second radiating arm are arranged on different planes; The accused antenna is allegedly folded into a three-dimensional shape, arranging portions of its radiating arms on different planes. ¶30d col. 2:41-43
wherein the first radiating arm is at least partially shaped according to a grid-dimension curve; and The shape of the first radiating arm allegedly defines a grid-dimension curve with a calculated grid dimension (Dg) of 1.37, which is greater than 1. ¶30e col. 2:44-46
wherein the printed circuit board, the communication circuitry, and the multi-band antenna are arranged inside the device housing. The accused product's PCB, communication circuitry, and antenna are all allegedly contained within the device housing. An annotated photograph shows these components inside the device housing Compl. p. 12 ¶30f col. 2:47-50
  • Identified Points of Contention:
    • Scope Questions: A central question may be whether the term "mobile communication device" as used in the patent can be read to cover a stationary medical device like a CPAP machine, which, while containing mobile communication technology, is not itself a handheld mobile device in the conventional sense.
    • Technical Questions: The infringement allegation hinges on whether the accused antenna's shape meets the claim's requirement of being "at least partially shaped according to a grid-dimension curve." The complaint provides a calculation to support this Compl. p. 12, but the defense may challenge the methodology or the applicability of this mathematical construct to the physical object, raising a key evidentiary question for the court.
      '887 Patent Infringement Allegations
Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A mobile communication device comprising: communications circuitry; a circuit board comprising a ground plane and a feeding point... a mounting structure... a section of the mounting structure extending over the circuit board; The Resmed AirCurve 10 is alleged to be a mobile communication device containing circuitry, a PCB with a ground plane, and a mounting structure that extends over the PCB. An annotated image shows these components Compl. p. 16 ¶41a col. 2:50-58
a multi-band antenna secured to the mounting structure and laterally offset from an edge of the ground plane... The accused product's antenna is allegedly secured to the mounting structure and positioned laterally offset from the PCB's ground plane edge. ¶41b col. 2:59-61
the multi-band antenna comprising: a common conductor coupled to the feeding point; first and second radiating arms coupled to and extending from the common conductor; The accused antenna allegedly comprises a common conductor coupled to the feeding point on the PCB, with first and second radiating arms extending from it. ¶41c col. 2:62-64
a space-filling curve constituting at least a part of the first radiating arm, wherein the space-filling curve comprises at least ten segments that are shorter than a tenth of a free-space operating wavelength..., each of the segments being connected to its neighboring segments at an angle such that no pair of adjacent segments defines a longer straight segment... The first radiating arm of the accused antenna allegedly comprises a shape with more than ten segments, each shorter than λ/10 for the LTE 12 band, that meets the specific angular and non-collinear requirements of a "space-filling curve" as defined in the claim. The complaint provides a supporting annotated image with measurements Compl. p. 18 ¶41d col. 2:65-3:8
  • Identified Points of Contention:
    • Technical Questions: The primary point of contention will likely be a highly factual analysis of whether the accused antenna's geometry strictly meets all the positive and negative limitations of the "space-filling curve" as recited in the claim. This includes the number of segments, segment length relative to wavelength, the angles between segments, and the non-periodicity requirements. Any deviation from these precise geometric rules could form the basis of a non-infringement defense.

V. Key Claim Terms for Construction

  • For the '365 Patent

    • The Term: "grid-dimension curve"
    • Context and Importance: This is a technical, mathematically-defined term central to claim 1. Its construction is critical because infringement depends on whether the physical shape of the accused antenna is "partially shaped according to" this specific type of curve. Practitioners may focus on this term because the complaint's infringement theory relies on a specific calculation of the "Grid dimension (Dg)" Compl. p. 12, making the definition and method of calculation a focal point of the dispute.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The patent states the first radiating arm is "at least partially shaped" according to the curve, which may support an argument that an exact match is not required and that any shape exhibiting the general characteristic of a grid-dimension curve would suffice '365 Patent, col. 8:9-10
      • Evidence for a Narrower Interpretation: The patent may provide specific examples of grid-dimension curves (such as curves derived from Hilbert or Peano curves) in the detailed description or drawings, which could be used to argue that the term should be limited to such specific, highly complex geometries '365 Patent, col. 6:40-54

  • For the '887 Patent

    • The Term: "space-filling curve"
    • Context and Importance: This term is given a detailed, multi-part definition directly within claim 1. Its interpretation is crucial as it forms the core of the novelty for miniaturization. Practitioners may focus on the sub-clauses of the definition, such as "wherein any periodicity of the space-filling curve... involves a periodic structure having a period defined by a non-periodic curve comprising at least ten connected segments." The complexity of this language suggests it will be a central point of contention in applying the claim to the accused product.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The claim preamble states the curve constitutes "at least a part of the first radiating arm," which may support an argument that not the entire arm needs to conform to the complex definition, only a portion of it '887 Patent, col. 2:65-66
      • Evidence for a Narrower Interpretation: The claim itself provides a long and explicit definition with multiple geometric constraints (e.g., "at least ten segments," "shorter than a tenth of a free-space operating wavelength," "no pair of adjacent segments defines a longer straight segment") '887 Patent, col. 2:67-3:8 This extensive intra-claim definition provides strong evidence for a narrow construction that requires strict satisfaction of every listed constraint.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges induced infringement for all asserted patents. It claims Defendant provides products along with advertising, marketing, training, and technical support that instruct and encourage customers to use the products' built-in cellular technology in an infringing manner Compl. ¶31 Compl. ¶42 Compl. ¶53 Compl. ¶64 Compl. ¶75 The complaint cites Defendant's website, which allegedly promotes the benefits of this wireless connectivity Compl. ¶31
  • Willful Infringement: The complaint alleges willful infringement based on pre-suit knowledge. It states that Plaintiff first notified Defendant of the patents-in-suit and the alleged infringement in a June 2021 letter, with subsequent communications in 2021 and 2022 Compl. ¶¶17-20 The complaint alleges that Defendant continued its infringing activities despite having actual knowledge of the patents and the infringement allegations Compl. ¶22

VII. Analyst's Conclusion: Key Questions for the Case

  • A core issue will be one of geometric and mathematical scope: can Plaintiff prove, through expert testimony and technical evidence, that the physical shapes of the antennas in Resmed's medical devices satisfy the highly specific and complex definitions of "grid-dimension curve" and "space-filling curve" as recited in the patents? The case may turn on a granular, feature-by-feature comparison of the accused products against these intricate claim limitations.
  • A second key question will address configurational infringement: for the patents directed to enhancing isolation between two antennas, does the physical arrangement of the antennas within the Resmed AirSense 11 and AirCurve 11 products-relative to each other and to the device's ground plane-fall within the specific spatial configurations claimed in the '960 and '458 patents?
  • An important secondary question will concern willfulness: did Defendant's alleged refusal to sign a non-disclosure agreement to review Plaintiff's infringement charts, followed by its continued sales of the accused products, constitute willful or egregious conduct sufficient to support an award of enhanced damages, should infringement be found?