PTAB

IPR2024-01457

Kangxi Communication Technologies Shanghai Co Ltd v. Skyworks Solutions Inc

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: RADIO FREQUENCY DEVICES HAVING REDUCED INTERMODULATION DISTORTION
  • Brief Description: The ’194 patent discloses radio-frequency (RF) switch systems designed to reduce interference and intermodulation distortion (IMD). The claimed solution involves a specific configuration of series and shunt switch circuits with capacitors positioned between an antenna node and transmit/receive nodes to improve performance, particularly against low-frequency blocker signals.

3. Grounds for Unpatentability

Ground 1: Claims 1-11 are obvious over Huang in view of the knowledge of a POSITA.

  • Prior Art Relied Upon: Huang (Application # 2011/0254614) and the general knowledge of a Person of Ordinary Skill in the Art (POSITA).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Huang discloses the identical circuit topology claimed in the ’194 patent for a high-power, semiconductor-based, single-pole double-throw (SPDT) transmit-receive switch. Huang’s disclosure of a first series FET switch (220) between an antenna node (201) and transmit node (202), and a second series FET switch (230) between the antenna and receive nodes (203), allegedly maps to the claimed switch circuits. Further, Huang’s blocking capacitors (211, 215) are positioned in series with these respective switches, and its shunt arms include shunt FETs (240, 250) connected to ground and additional blocking capacitors (213, 217), mirroring the limitations of independent claims 1 and 4.
    • Motivation to Combine: Petitioner contended that a POSITA would have been motivated to apply well-known electrical engineering principles to Huang’s disclosed circuit. The primary argument centered on the inherent function of capacitors. A POSITA would understand that the "blocking capacitors" in Huang’s circuit inherently function as high-pass filters, a standard technique for inhibiting known low-frequency "blocker" signals from mixing with desired fundamental-frequency signals. This modification was presented as a simple application of textbook principles to solve the well-known problem of IMD in RF switches.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success because using series capacitors to block low-frequency signals is a fundamental and predictable technique. Sizing the capacitors to achieve the desired frequency response for a WLAN application, as disclosed in Huang, was argued to be a routine design choice with predictable outcomes for improving IMD performance.

Ground 2: Claims 1-11 are obvious over Seshimo in view of the knowledge of a POSITA.

  • Prior Art Relied Upon: Seshimo (Japanese Patent Publication No. JP 2006-121217) and the general knowledge of a POSITA.
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Seshimo, like Huang, discloses the same "particular configuration" of components as the ’194 patent in a high-frequency semiconductor switching circuit used in a Personal Handyphone System (PHS). Seshimo’s Figure 3 allegedly shows a first switch circuit (MOSFET T2) and second switch circuit (MOSFET T1) connected between an antenna node (RF_COM) and transmit/receive nodes (RF_2, RF_1). Petitioner mapped Seshimo’s capacitors C3 and C2 to the claimed series capacitors. The first and second shunt arms in Seshimo allegedly include shunt switches (MOSFETs T4, T3) and capacitors (C7, C5), corresponding to the remaining limitations of independent claims 1 and 4.
    • Motivation to Combine: The motivation argument mirrored that of Ground 1. Petitioner argued that a POSITA would recognize the well-known problem of interference in RF switches and would be motivated to use the capacitors disclosed in Seshimo for their inherent high-pass filtering properties. A POSITA would combine Seshimo's disclosed circuit with the knowledge that such a capacitor arrangement is a known solution for preventing low-frequency blocker signals from degrading performance, thereby improving the switch's linearity and reducing IMD.
    • Expectation of Success: The expectation of success was based on the predictability of capacitor behavior. A POSITA would expect that selecting appropriate capacitance values for C2 and C3 in Seshimo's circuit—a conventional design task—would predictably filter out-of-band blocker signals and improve switch performance for the target PHS application.

4. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under Fintiv is inappropriate. Although a parallel district court case exists, it was stayed pending the outcome of a co-pending ITC investigation. Petitioner cited the Director's June 2022 Guidance Memo stating that the PTAB will not discretionarily deny petitions based on applying Fintiv to a parallel ITC proceeding.
  • Petitioner also argued that denial under 35 U.S.C. §325(d) is inappropriate because the asserted prior art references, Huang and Seshimo, were not cited or considered during the original prosecution of the ’194 patent. Therefore, the challenges were not cumulative to the Examiner's search.

5. Relief Requested

  • Petitioner requests institution of IPR for claims 1-11 and cancellation of those claims as unpatentable under 35 U.S.C. §103.