RPX Corp v. ParkerVision Inc

1. Case Identification

• Case #: IPR2014-00946
• Patent #: 6,266,518
• Filed: June 12, 2014
• Petitioner(s): Dr. Michael Farmwald and RPX Corporation
• Patent Owner(s): ParkerVision, Inc.
• Challenged Claims: 1, 27, 82, 90, and 91

2. Patent Overview

• Title: Method and System for Down-Converting an Electromagnetic Signal
• Brief Description: The ’518 patent discloses methods and systems for down-converting a radio frequency (RF) signal to a lower frequency, such as an intermediate frequency (IF) or baseband. The technology operates by "aliasing" the input signal, defined as sampling at a rate less than or equal to twice the frequency of the input signal, and is described as transferring either negligible or non-negligible amounts of energy during the sampling process.

3. Grounds for Unpatentability

Ground 1: Claims 1, 27, 82, 90, and 91 are anticipated by Estabrook under 35 U.S.C. § 102(b)

• Prior Art Relied Upon: Estabrook ("The direct conversion receiver: Analysis and design of the front-end components," Ph.D. dissertation, Stanford University, 1989).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Estabrook discloses a direct conversion receiver that anticipates every limitation of the challenged claims. Estabrook teaches sampling a carrier signal at an aliasing rate (using a local oscillator frequency equal to the carrier frequency, where N=1) over non-negligible aperture periods (approximately 50% of the control signal period) to maximize current transfer and minimize conversion loss. The system integrates energy on a capacitor during the "on-time" and generates a baseband signal by transferring this energy to a load during the "off-time." Petitioner asserted that the resulting "sawtooth" voltage waveform shown in Estabrook is the same type of signal the patent owner described as the hallmark of its invention. The disclosure of impedance matching circuits and the apparatus structure allegedly anticipates claims 82, 90, and 91.

Ground 2: Claims 1, 27, 82, 90, and 91 are anticipated by Avitabile under 35 U.S.C. § 102(b)

• Prior Art Relied Upon: Avitabile et al. (“S-band digital downconverter for radar applications based on a GaAs MMIC fast sample-and-hold,” IEE Proc. On Circuits, Devices and Systems, 1996).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner contended that Avitabile describes a down-converter using sub-harmonic sampling (e.g., down-converting a 1 GHz signal with a 250 MHz sampling rate, where N=4), which is an aliasing rate disclosed as a preferred embodiment in the ’518 patent. Avitabile uses non-negligible aperture periods and discloses that charge is accumulated on a capacitor over multiple samples. The down-converted signal is described as the voltage across this capacitor, which Petitioner argued meets the limitation of "generating the baseband signal from the integrated energy." Furthermore, Avitabile discloses that energy is discharged from the capacitor during the hold period ("droop off"), which transfers energy to a load during the switch off-time, anticipating claim 27 and satisfying the patent owner's narrower litigation-based claim construction.

Ground 3: Claims 1, 27, 82, 90, and 91 are anticipated by Weisskopf under 35 U.S.C. § 102(b)

• Prior Art Relied Upon: Weisskopf ("Subharmonic Sampling of Microwave Signal Processing Requirements," Microwave Journal, May 1992).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Weisskopf discloses a sub-harmonic sample-and-hold circuit for down-conversion that explicitly teaches setting the sampling aperture to one-half the period of the carrier signal to maximize energy transfer. Weisskopf describes accumulating charge on a capacitor and explicitly states that the process "converts most of the sampled energy to the baseband spectral replica." Petitioner asserted this anticipates the claims under the broadest reasonable interpretation. Crucially, Weisskopf discusses two alternative approaches: using a high-impedance load to minimize energy discharge and using a low-impedance load where substantial energy is discharged. This dual disclosure was argued to anticipate the claims regardless of whether a broad interpretation (no discharge required) or the patent owner's narrower interpretation (discharge required) is adopted. Weisskopf's disclosure of impedance matching structures was also mapped to the limitations of claims 90 and 91.

4. Key Claim Construction Positions

• "(Generating the baseband signal)... from the integrated energy": This term was central to the petition. Petitioner argued that the patent owner, in related district court litigation, improperly asserted a narrow construction requiring the "discharge of energy from a storage device" to generate the signal. Petitioner contended that this construction was advanced solely to avoid prior art.
• Petitioner's Proposed Construction: The broadest reasonable interpretation, consistent with the specification, is generating the signal using the integrated energy in any way. This includes the voltage that exists across the capacitor itself, which represents the down-converted signal, without necessarily requiring a separate discharge step. Petitioner argued the patent owner's narrow construction would improperly exclude numerous embodiments described in the ’518 patent, such as sample-and-hold circuits where the voltage is held, not discharged. Petitioner used its anticipation arguments to show the prior art met the claims even under the patent owner's narrower construction.

5. Relief Requested

• Petitioner requested institution of an inter partes review and cancellation of claims 1, 27, 82, 90, and 91 of the ’518 patent as unpatentable.