PTAB

IPR2025-00373

Kangxi Communications Technologies Shanghai Co Ltd v. Skyworks Solutions Inc

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Apparatus and Methods for Biasing Power Amplifiers
  • Brief Description: The ’101 patent is directed to a power amplifier (PA) and a biasing circuit that addresses gain variation during startup. The invention provides a temporary current boost to the PA’s bias current to compensate for reduced gain caused by thermal effects as the circuitry warms up, thereby achieving a flatter gain response over time.

3. Grounds for Unpatentability

Ground 1: Obviousness over Ishimaru - Claims 1-2, 10-11, 17-18, and 20-22 are obvious over Ishimaru.

  • Prior Art Relied Upon: Ishimaru (Application # 2009/0212863).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Ishimaru is a parallel disclosure to the ’101 patent, as it addresses the identical problem of PA gain variation at startup due to thermal effects with a nearly identical solution. Ishimaru disclosed a power amplifier system with a “speedup circuit” that functions as the claimed “gain correction circuit.” This circuit uses a time-dependent signal generator (capacitor 121 and resistor 136) to shape an enable signal into a control current. This control current is then amplified by a current amplifier (transistor 119) that pulls a correction current from a primary biasing circuit, temporarily boosting the PA’s bias current to correct for low gain at startup. Petitioner contended that transistor 119 in Ishimaru’s circuit is a current amplifier that functions as a current mirror, satisfying the limitation added during prosecution to secure allowance of the ’101 patent claims.
    • Key Aspects: The argument centered on the assertion that the very feature relied upon for patentability—a current amplifier including a current mirror—was already present in Ishimaru’s single-transistor implementation, which performs the same function of replicating and amplifying a current to correct for gain variation.

Ground 2: Obviousness over Ishimaru in view of Harrison - Claims 1-2, 10-11, 17-18, and 20-22 are obvious over Ishimaru in view of Harrison.

  • Prior Art Relied Upon: Ishimaru (Application # 2009/0212863) and Harrison (a 2005 book titled “Current Sources & Voltage References”).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground was presented as an alternative in the event the Patent Owner successfully argues that the term “current mirror” requires at least two transistors, a construction that Ishimaru’s single-transistor (119) implementation might not satisfy. Ishimaru taught the overall system for correcting startup gain variation. Harrison taught a basic, well-known two-transistor current mirror that was a staple of analog circuit design for biasing and coupling circuit stages. Petitioner argued for replacing Ishimaru’s single-transistor current amplifier with Harrison's standard two-transistor current mirror.
    • Motivation to Combine: A POSITA would combine Ishimaru’s bias correction circuit with Harrison’s conventional two-transistor current mirror to achieve predictable benefits. The modification would provide improved design flexibility, better isolation between circuit stages, and more granular, linear gain control by adjusting transistor size ratios, which is a known advantage of such mirrors. Ishimaru provided motivation by addressing slight variations in gain that require precise control, which Harrison’s well-controlled circuit would facilitate more effectively than Ishimaru’s single-transistor amplifier.
    • Expectation of Success: A POSITA would have had a high expectation of success in making this combination. It involved substituting one known circuit block (a single-transistor amplifier) with a standard, functionally equivalent, and more advantageous circuit block (a two-transistor current mirror) to achieve well-understood improvements in performance and tunability.

4. Key Claim Construction Positions

  • Petitioner argued that the claim terms should be given their plain and ordinary meaning and that the prior art renders the claims unpatentable under any reasonable construction.
  • However, the petition preemptively addressed a potential dispute over the term “current mirror.” Ground 1 asserted that Ishimaru’s single-transistor amplifier met the plain meaning of the term. Ground 2 was provided as an alternative to show obviousness even under a narrower construction potentially advanced by the Patent Owner (based on related litigation) that a “current mirror” must comprise at least two transistors with tied bases.

5. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under Fintiv is inappropriate. Citing Director guidance, it asserted that Fintiv factors do not apply to parallel U.S. International Trade Commission (ITC) proceedings. Furthermore, the co-pending district court litigation was stayed pending the outcome of the ITC investigation.
  • Petitioner also argued that denial under §325(d) would be improper because the key prior art references, Ishimaru and Harrison, were not before the examiner during the original prosecution of the ’101 patent.

6. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-2, 10-11, 17-18, and 20-22 of the ’101 patent as unpatentable.