PTAB

IPR2025-00727

T-Mobile USA Inc v. Smart RF Inc

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Adaptive predistortion device and method using digital receiver
  • Brief Description: The ’345 patent relates to wireless radio systems that use signal predistortion to counteract distortion introduced by power amplifiers. The invention specifically claims the use of digital receiver technology to convert analog RF feedback signals into digital signals for processing and determining the required predistortion.

3. Grounds for Unpatentability

Ground 1: Obviousness over Wright - Claims 1, 2, 5-8, and 11 are obvious over Wright.

  • Prior Art Relied Upon: Wright (Patent 6,587,514).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Wright taught an adaptive digital predistortion system for RF signals that compensates for power amplifier (PA) nonlinearity and memory effects. Wright’s system included an I/Q modulator controlled by amplitude and phase look-up tables (LUTs), a control module (ACPCE) that models the PA using feedback signals, and updates the LUTs accordingly. Wright disclosed using a digital receiver to process the amplified output signal (the second feedback signal).
    • Motivation to Combine (Implicit): Petitioner argued that while Wright did not expressly disclose using a digital receiver for the predistorted signal (the first feedback signal), it would have been obvious to a Person of Ordinary Skill in the Art (POSITA). Since Wright’s control module (ACPCE) is digital, it required the analog RF feedback signals to be converted to complex baseband. A POSITA knew this could be done with either an analog I/Q demodulator or a digital receiver. Using a digital receiver was a known, predictable solution to the known problem of analog components introducing unwanted distortion.
    • Expectation of Success: A POSITA would have had a high expectation of success, as Wright already taught the necessary digital receiver architecture for processing other feedback signals in the system.

Ground 2: Obviousness over Wright and Jin - Claims 3, 4, 9, and 10 are obvious over Wright in view of Jin.

  • Prior Art Relied Upon: Wright (Patent 6,587,514) and Jin (Patent 6,693,974).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Wright provided the foundational predistortion system as detailed in Ground 1. Jin taught an adaptive digital predistortion circuit that specifically used an Adjacent Channel Power Ratio (ACPR) measurement sub-step to optimize the PA’s performance. Jin’s method involved comparing feedback signals to a predetermined ACP profile (based on a communication standard) and updating the predistorter to maximize the PA’s power efficiency while remaining within regulatory limits. This directly mapped to the limitations of claims 3, 4, 9, and 10, which require updating the predistortion based on an ACPR linearity metric.
    • Motivation to Combine: A POSITA would combine Jin with Wright to solve the well-known problem of ensuring RF transmitters comply with regulatory standards for adjacent channel interference, a problem Wright acknowledged. Jin provided an express solution for optimizing PA performance under these constraints. Combining a known optimization technique (Jin) with a compatible system (Wright) to achieve a predictable improvement (regulatory compliance and efficiency) was a strong motivation.
    • Expectation of Success: A POSITA would expect success because Jin’s ACPR measurement technique was designed for digital predistortion systems like Wright’s and utilized standard signal processing techniques (e.g., Fast Fourier Transform) that were well within the capabilities of a POSITA.

Ground 3: Obviousness over Booth and Leyendecker - Claims 1, 2, 5, 6, and 11 are obvious over Booth in view of Leyendecker.

  • Prior Art Relied Upon: Booth (Patent 6,512,417) and Leyendecker (Patent 5,867,065).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner stated that Booth disclosed a digital predistortion system for an analog RF input signal that compensates for PA distortion, including memory effects. However, Booth did not explicitly disclose using an indirect modeling architecture or multiple digital receivers. Leyendecker taught these missing elements: a "direct inverse" (or indirect) modeling subsystem and the use of digital receivers to translate RF feedback signals to complex baseband. Petitioner argued that adding Leyendecker's indirect modeler and digital receivers to Booth's system rendered the challenged claims obvious.
    • Motivation to Combine: A POSITA would be motivated to incorporate Leyendecker’s indirect model into Booth to gain its known advantages, such as reduced computational complexity and enabling real-time operation. Further, a POSITA would be motivated to use Leyendecker’s digital receivers to solve the known problem of analog feedback path components introducing distortion not attributable to the PA, thereby improving the accuracy of the predistortion. Booth itself cited Leyendecker as relevant prior art.
    • Expectation of Success: The combination would have been simple and predictable. It involved adding known components (e.g., couplers, delays) and implementing digital receivers using conventional DSP circuitry as taught by Leyendecker to improve the performance of a system like Booth's.

4. Arguments Regarding Discretionary Denial

  • Petitioner argued that the Board should not exercise discretionary denial under §325(d) because none of the prior art references relied upon in the petition were cited or considered during the original prosecution of the ’345 patent.
  • Petitioner also contended that discretionary denial under §314(a) based on Fintiv factors was inappropriate. Petitioner asserted that the trial date in the parallel district court litigation was uncertain and likely to be pushed past the statutory deadline for a Final Written Decision (FWD), the court had not issued any substantive rulings, and the merits of the petition are exceptionally strong. Furthermore, Petitioner stipulated that if the inter partes review (IPR) is instituted, it will not pursue any ground raised or that could have been reasonably raised in the petition in the parallel litigation.

5. Relief Requested

  • Petitioner requests institution of IPR and cancellation of claims 1-11 of the ’345 patent as unpatentable under 35 U.S.C. §103.