PTAB

IPR2020-00514

NXP USA Inc v. Impinj Inc

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Key Events
Petition

1. Case Identification

2. Patent Overview

  • Title: Increasing Dynamic Range of RFID Tag Self-tuning
  • Brief Description: The ’816 patent describes Radio-Frequency Identification (RFID) integrated circuits (ICs) and tags that perform self-tuning. The technology aims to maximize the power extracted from a received RF wave by adjusting a variable impedance in a matching network between the antenna and the IC, particularly addressing issues that arise when the tag is detuned.

3. Grounds for Unpatentability

Ground 1: Obviousness over El Waffaoui ’016 and El Waffaoui ’279 - Claims 1, 3-5, 8, 10-12, 15, and 17-19 are obvious over El Waffaoui ’016 in view of El Waffaoui ’279.

  • Prior Art Relied Upon: El Waffaoui ’016 (Patent 8,730,016) and El Waffaoui ’279 (Patent 7,944,279).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that El Waffaoui ’016, the primary reference, discloses the core elements of the challenged independent claims. This included an RFID tag with a variable impedance (implemented as a switched capacitor bank), a tuning circuit to adjust it, and a rectifier with serially-coupled stages to extract power. Critically, Petitioner asserted that ’016 teaches the two-phase tuning process central to the ’816 patent: (1) a "first time period" where the tuning circuit is disabled and the variable impedance is set to an initial value (e.g., 50% capacitance) when the extracted voltage is low, and (2) a "second time period" after the voltage rises, where the tuning circuit is enabled to actively tune the impedance.
    • Prior Art Mapping (Dependent Claims): For dependent claims 3 and 4, which require using different voltages from different rectifier stages during the first and second time periods, Petitioner contended that ’016 alone was insufficient. While ’016 teaches setting an initial impedance at a low voltage (0.5V) and active tuning at a higher voltage (>1V), it does not explicitly state that these voltages come from different rectifier stages. Petitioner argued that El Waffaoui ’279 remedies this by teaching a charge pump with cascading rectifier stages that explicitly output different "intermediate voltages" for use by various logic components within the RFID tag.
    • Motivation to Combine: Petitioner asserted that a Person of Ordinary Skill in the Art (POSITA) would combine these references for several reasons. First, El Waffaoui ’016 expressly incorporates the application that became the ’279 patent by reference. Second, the patents share a common inventor and were assigned to the same entity, suggesting a related line of development. Third, both patents are in the same technical field of RFID tag tuning. A POSITA seeking to implement the two-voltage-level system suggested in ’016 would naturally look to a related patent like ’279, which provides a known and direct method for generating multiple, different voltage levels from a single rectifier structure.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success because combining the teachings was straightforward. Applying the multi-voltage output rectifier from ’279 to the RFID circuit of ’016 was a predictable way to source the different voltages needed for the initial (low-power) and active (high-power) tuning phases, using existing and compatible circuit designs.

Ground 2: Obviousness over El Waffaoui ’016, El Waffaoui ’279, and El Waffaoui ’729 - Claims 6, 13, and 20 are obvious over El Waffaoui ’016 in view of El Waffaoui ’279 and El Waffaoui ’729.

  • Prior Art Relied Upon: El Waffaoui ’016 (Patent 8,730,016), El Waffaoui ’279 (Patent 7,944,279), and El Waffaoui ’729 (Patent 9,430,729).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground built upon the combination in Ground 1 to address the limitations of dependent claims 6, 13, and 20. These claims require the initial impedance tuning to be performed using a specific type of "zero-gate-voltage switch," such as a "floating-gate transistor including a control gate." While El Waffaoui ’016 discloses using MOSFET switches in its capacitor bank, it does not specify this particular type. Petitioner argued that El Waffaoui ’729 provides this missing element by explicitly disclosing the use of non-volatile, floating-gate transistor switches in a tunable capacitor bank for a passive RFID apparatus.
    • Motivation to Combine: Petitioner contended that a POSITA would be motivated to incorporate the switches from ’729 into the circuit of ’016 to solve a well-known "start-up problem" in passive RFID tags. El Waffaoui ’729 explicitly explains that its non-volatile switches can be set to an initial state (e.g., closed) even in the absence of an RF signal and its corresponding power. This allows the tag’s capacitor bank to have a default capacitance value, ensuring the tag is coarsely tuned and can successfully power up when it enters an RF field. A POSITA would integrate this known solution from ’729 into the ’016 design to gain this explicit, stated advantage of improved reliability. The shared inventorship and technical field among all three references further supported this motivation.
    • Expectation of Success: A POSITA would have expected success because this modification involved substituting one known type of switch (a generic MOSFET) with another known, improved type of switch (a floating-gate transistor) to achieve a predictable benefit (alleviating the start-up problem). The implementation would be well within the skill of a POSITA.

4. Relief Requested

  • Petitioner requests the institution of an inter partes review and the cancellation of claims 1, 3-6, 8, 10-13, 15, and 17-20 of Patent 9,471,816 as unpatentable.