PTAB

IPR2025-00692

T-Mobile USA Inc v. Smart RF Inc

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Digital Multi-Band Predistortion Linearizer with Nonlinear Subsampling Algorithm in the Feedback Loop
  • Brief Description: The ’204 patent discloses a digital predistortion system for multi-band transmitters. The system is designed to compensate for non-linearities in a power amplifier by using an "indirect learning" architecture that employs a feedback loop with a subsampling receiver to analyze the amplifier's output and update the predistortion algorithm.

3. Grounds for Unpatentability

Ground 1: Obviousness over Peroulas Alone or in View of Cidronali - Claims 1-15 are obvious over Peroulas in view of Cidronali.

  • Prior Art Relied Upon: Peroulas (WO 2012/129768) and Cidronali (a 2009 workshop paper).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Peroulas disclosed a nearly identical multi-band predistortion architecture for a transmitter. It taught a MIMO Pre-Distortion Module that compensates for power amplifier non-linearity using an indirect learning approach, where feedback is taken from both the predistorter output and the power amplifier output. This feedback is fed into a MIMO Capture Buffer and Digital Signal Processor (DSP) to update the predistortion functions. Petitioner contended that Peroulas’s disclosure of concurrent feedback signals being captured and digitized inherently taught or suggested the claimed concurrent sampling. The central disputed limitation, sampling at a subsampling frequency, was argued to be an obvious implementation choice, as subsampling was a well-known technique for such feedback loops.
    • Motivation to Combine: Alternatively, Petitioner asserted a person of ordinary skill in the art (POSITA) would combine Peroulas with Cidronali. Cidronali explicitly taught a subsampling receiver for dual-band digital predistortion systems to achieve "extreme flexibility and coherent dual-band down-conversation." The motivation for this combination was driven by the well-known benefits of subsampling: reducing cost, complexity (fewer ADCs), and power consumption. These benefits directly addressed the recognized need in the art to lower the implementation cost of predistorters, a goal also stated by Peroulas.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because incorporating subsampling into Peroulas’s system was a straightforward modification. It would only change the mechanics of how the feedback signal is sampled before being fed into the MIMO Capture Buffer, without altering the fundamental predistortion technique taught by Peroulas.

Ground 2: Obviousness over Posti Alone or in View of Cidronali - Claims 1-15 are obvious over Posti in view of Cidronali.

  • Prior Art Relied Upon: Posti (Patent 6,999,523) and Cidronali (a 2009 workshop paper).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Posti disclosed a multi-frequency carrier transmitter that used an indirect learning architecture to linearize distortion from a power amplifier. Posti’s system included a plurality of digital modulators for predistortion and an adaptive predistorter that received feedback from both the power amplifier output and the digital modulator outputs. Petitioner asserted that Posti’s disclosure of sampling a part of the transmitted signal in a feedback loop met the "concurrent sampling" limitation. As in Ground 1, Petitioner argued that using a subsampling frequency was an obvious, well-known technique a POSITA would have understood to apply to Posti’s feedback loop.
    • Motivation to Combine: If Posti alone was deemed insufficient, Petitioner argued a POSITA would combine Posti with Cidronali for the same reasons as in Ground 1. Posti recognized the desirability of reducing transmitter costs, and Cidronali’s subsampling technique provided a known solution to reduce component count, cost, and power consumption while improving system flexibility. The combination would efficiently implement Posti’s feedback path.
    • Expectation of Success: Modifying Posti’s system to include subsampling would be simple and predictable. It could be achieved by setting the sampling frequency of Posti’s existing ADC according to well-known subsampling principles or by implementing a single subsampling receiver as taught by Cidronali. This would not require any structural modification to Posti’s core architecture.

4. Key Claim Construction Positions

  • Petitioner proposed that all claim terms be given their plain and ordinary meaning. However, to aid the Board, Petitioner provided context for "band" and "channel," which were not defined in the ’204 patent.
  • Petitioner argued a POSITA would understand a "band" to be a continuous range of frequencies and a "channel" to be a signal path within a band. In the context of the ’204 patent’s dual-band transmitter, each input signal path to a predistorter, with its corresponding frequency range, represents a "channel." This interpretation was argued to be critical for showing how the prior art, which disclosed multi-band or multi-frequency systems, met the claim limitations directed to multiple channels and bands.

5. Arguments Regarding Discretionary Denial

  • Petitioner argued the Board should not exercise its discretion to deny institution under either 35 U.S.C. §325(d) or §314(a) (Fintiv).
  • §325(d): The primary references relied upon (Peroulas, Posti, and Cidronali) were never cited, discussed, or applied during the prosecution of the ’204 patent.
  • Fintiv (§314(a)): Petitioner argued against denial based on parallel district court litigation because the litigation was in a very early stage. The court had not issued any substantive rulings, and the claim construction hearing was not scheduled until May 2025, after the statutory deadline for an institution decision. Petitioner also noted that the trial date of November 2025 was uncertain due to case complexity and multiple parties, and that the merits of the petition were particularly strong and compelling. Further, Petitioner stipulated that if the IPR is instituted, it will not pursue any ground raised or that reasonably could have been raised in the parallel litigation.

6. Relief Requested

  • Petitioner requests institution of inter partes review and cancellation of claims 1-15 of the ’204 patent as unpatentable.