PTAB

IPR2020-01027

Dell Inc v. Neodron Ltd

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Petition
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1. Case Identification

2. Patent Overview

  • Title: Touch Sensor with Compensation for Retransmission
  • Brief Description: The ’580 patent describes a method for improving the accuracy of a capacitive touch sensor. The technology aims to reduce errors caused by "retransmission"—where charge from a drive signal is incorrectly coupled through a user's multi-touch contact—by using a secondary capacitance measurement (e.g., self or cross-capacitance) to compensate or adjust the primary mutual capacitance measurement signals before determining valid touch points.

3. Grounds for Unpatentability

Ground 1: Claims 1-12 are obvious over Yousefpor in view of Chang.

  • Prior Art Relied Upon: Yousefpor (Application # 2010/0060608) and Chang (Patent 8,587,555).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Yousefpor taught the core elements of the independent claims, including a touch sensor with drive and sense lines for mutual capacitance measurement. Yousefpor addressed correcting distorted readings from "negative pixels" caused by retransmission in poorly grounded multi-touch events. It disclosed performing a secondary "reverse stimulation" (a self-capacitance measurement) on the sense lines and using an iterative algorithm to compensate the mutual capacitance signals. Petitioner asserted that Chang addressed a similar retransmission problem, which it termed "water stains" or "conductive impurities," and also taught using both self and mutual capacitance measurements. To the extent Yousefpor performs its self-capacitance measurement on the sense lines, Petitioner argued Chang taught the interchangeability of drive and sense lines, making it obvious to perform the self-capacitance measurement on the drive lines as claimed.
    • Motivation to Combine: A POSITA would combine Yousefpor and Chang because both references addressed the same well-known retransmission problem in capacitive touch sensors, albeit using different terminology ("negative pixels" vs. "water stains"). Both proposed solutions using a combination of mutual and self-capacitance measurements, which were known design choices. Petitioner contended a POSITA would be motivated to incorporate Chang’s teachings on the interchangeability of drive/sense lines into Yousefpor’s system to create a more compact and efficient design.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because the combination involved applying predictable and well-understood measurement techniques to known hardware. The modifications were routine software and hardware adjustments with predictable outcomes for solving the common problem of signal error from retransmission.

Ground 2: Claims 1-12 are obvious over Yousefpor in view of Krah.

  • Prior Art Relied Upon: Yousefpor (Application # 2010/0060608) and Krah (Patent 9,746,967).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that the combination of Yousefpor and Krah taught all limitations of the challenged claims. As in Ground 1, Yousefpor provided the foundational system of using mutual and self-capacitance measurements to correct for "negative pixels." Krah, which shares an inventor and assignee with Yousefpor, also addressed the same "negative pixel" retransmission problem. Crucially, Krah explicitly taught performing a "cross-capacitance" measurement—driving one drive line and sensing on another drive line in the same axis—to detect the negative pixel effect. Krah then used these cross-capacitance signals to "compensate sense signals" from the mutual capacitance measurement. This directly mapped to the claimed method of using a secondary measurement on the first set of lines (drive lines) to adjust the primary measurement.
    • Motivation to Combine: A POSITA would be highly motivated to combine these references. They share an inventor (Yousefpor), were assigned to the same entity (Apple), address the identical problem of "negative pixels" from retransmission, and share nearly identical system architecture diagrams. Petitioner argued that these interrelated references reflect a continuous design effort, and a POSITA seeking to solve the retransmission problem would have naturally looked to and combined the specific compensation techniques disclosed in both. Krah’s use of cross-capacitance was a specific, improved implementation of the general compensation scheme taught by Yousefpor.
    • Expectation of Success: Success would be highly expected given the substantial overlap between the references. The combination involved integrating techniques from two patents that were part of the same research and development effort, directed to the same architecture and problem, making the integration straightforward and predictable for a POSITA.

4. Key Claim Construction Positions

  • Petitioner argued that no terms required explicit construction but, in view of a parallel ITC investigation, adopted constructions issued by the Administrative Law Judge in that proceeding. Key adopted constructions included:
    • "after sending the third set of signals...": Construed as "after (not while) sending the third set of signals..." This construction was used to show that the prior art’s sequential, non-concurrent measurement steps met the claim limitations.
    • "adjusting the second set of measured values...": Construed as "changing the second set of measured values..." Petitioner used this construction to map the prior art’s compensation algorithms, which mathematically changed initial measurement values, to the claim language.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-12 of the ’580 patent as unpatentable under 35 U.S.C. §103.