Shenzhen Huiding Technology Co Ltd v. Synaptics Inc

1. Case Identification

• Case #: IPR2015-01741
• Patent #: 8,338,724
• Filed: August 17, 2015
• Petitioner(s): Shenzhen Huiding Technology Co., Ltd.
• Patent Owner(s): Synaptics Incorporated
• Challenged Claims: 1-26

2. Patent Overview

• Title: Methods and systems for detecting a position-based attribute of an object using digital codes
• Brief Description: The ’724 patent describes systems for detecting the position of an object (e.g., a finger) on a touch-sensitive surface. The core technology involves applying modulation signals, generated using a plurality of distinct digital codes like those in spread spectrum techniques, to sensor electrodes and then demodulating the resultant signals to determine the object's position.

3. Grounds for Unpatentability

Ground 1: Obviousness over Smith in view of Mulligan - Claims 1-3 and 6-26 are obvious over Smith and Mulligan.

• Prior Art Relied Upon: Smith (a 1999 MIT doctoral dissertation titled "Electric Field Imaging") and Mulligan (Application # 2004/0119701).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Smith taught the core inventive concepts of the ’724 patent, including the application of spread spectrum techniques like Code Division Multiple Access (CDMA) and Direct Sequence Spread Spectrum (DSSS) to capacitive touch sensing. Smith allegedly disclosed using distinct digital codes, such as maximum length codes generated by Linear Feedback Shift Registers (LFSRs), to simultaneously drive multiple transmitter electrodes. The resulting signals are measured by receiver electrodes, and the system determines an object's proximity based on the demodulated signals. Mulligan was presented as disclosing a conventional capacitive touch screen structure with orthogonal arrays of sensor bars, providing a well-known environment for implementing Smith's advanced signaling techniques.
  • Motivation to Combine: Petitioner contended a person of ordinary skill in the art (POSITA) would combine Smith's sophisticated signal processing methods with Mulligan's common touch-screen electrode layout. The motivation was to apply Smith's demonstrated improvements in signal-to-noise ratio (SNR) and multi-channel sensing to a standard, practical touch screen design like Mulligan's, thereby creating a device with improved accuracy and usability.
  • Expectation of Success: A POSITA would have a high expectation of success because both references operate in the same field of capacitive sensing, and applying Smith's signal modulation/demodulation scheme to Mulligan's electrode array was a straightforward integration of known principles.

Ground 2: Anticipation by Dietz - Claims 1-3, 6, 7, 13-21, and 23-26 are anticipated by Dietz.

• Prior Art Relied Upon: Dietz (Patent 6,498,590).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that Dietz, which predates the ’724 patent’s priority date by several years, disclosed every element of the challenged claims. Dietz described a multi-user, multi-touch system that uses CDM to allow simultaneous touch detection. It taught transmitting uniquely identifiable signals to an array of antennas (electrodes) by applying different time-delayed (i.e., phase-shifted) versions of the same pseudo-random bit sequence to each antenna. Petitioner argued that these phase-shifted sequences constitute the "distinct digital codes" recited in the claims. Dietz further disclosed a receiver that cross-correlates the received signal with the original sequence to detect touches and a processor that analyzes the coupled signals to determine touch locations, mapping directly to the claimed system.

Ground 3: Obviousness over Dietz in view of Gerpheide - Claims 8, 10-12, and 22 are obvious over Dietz and Gerpheide.

• Prior Art Relied Upon: Dietz (Patent 6,498,590) and Gerpheide (Patent 5,565,658).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground built upon the teachings of Dietz by incorporating Gerpheide’s method for interference rejection. Dietz provided the foundational multi-touch system using CDM. Gerpheide taught a capacitance-based proximity sensor that addresses noise and interference by adaptively adjusting its operating frequency. Specifically, Gerpheide disclosed a frequency generator that automatically selects a reference frequency that is not coherent with spurious signals, thereby improving measurement reliability. This teaching was argued to meet claim limitations related to adjusting signals based on electrical effects.
  • Motivation to Combine: A POSITA would combine Dietz with Gerpheide to enhance the robustness of the multi-touch system. Dietz already recognized the benefit of using spread spectrum techniques for interference robustness. A POSITA would be motivated to further improve this robustness by incorporating Gerpheide’s well-known technique of adaptive frequency adjustment to combat unpredictable noise sources, a common problem in capacitive sensing systems.
  • Expectation of Success: Success was expected because both patents address interference in multi-electrode capacitive sensors. Integrating Gerpheide’s frequency adjustment into Dietz's system was presented as a predictable solution to a known problem.
• Additional Grounds: Petitioner asserted additional obviousness challenges, including combinations adding Jaeger (Patent 7,084,860) for its disclosure of specific well-known codes (e.g., Walsh, Gold codes) and Cho (European Patent No. 1,289,181) for its teachings on adaptive modulation based on channel quality.

4. Key Claim Construction Positions

• "distinct digital codes": Petitioner proposed this term be given its plain and ordinary meaning: "digital codes that are different from one another or each other." This broad construction was intended to encompass various methods of creating distinctness, such as using different code sequences or phase-shifted versions of the same sequence, as taught in the prior art.
• "mathematically independent": For claims requiring this property, Petitioner argued the specification supports a construction of "substantially orthogonal." This interpretation does not require perfect mathematical orthogonality, but only that the codes are distinct enough "to produce meaningful independent results," aligning with the properties of pseudo-random codes used in the prior art.

5. Relief Requested

• Petitioner requested the institution of an inter partes review and the cancellation of claims 1-26 of the ’724 patent as unpatentable.