{
  "patent_number": "US 8939029",
  "country": "US",
  "title": "Improving MEMS Sensor Accuracy with a Co-located Reference Structure",
  "original_title": "MEMS sensor with movable Z-axis sensing element",
  "summary": "This patent describes a tiny sensor (MEMS) that measures motion, especially up-and-down (z-axis), by including a special stable reference part electrically connected to the moving part, which helps cancel out environmental noise and makes measurements much more accurate.",
  "what_it_does": "The patent details a Micro-Electro-Mechanical System (MEMS) sensor designed for improved accuracy. It features a main MEMS structure with a movable mass, which is the part that actually senses motion, built on a substrate (Claim 1). Crucially, it includes a separate reference structure that is electrically connected, or 'coupled,' to this movable mass (Claim 1). This reference structure is positioned radially inward, meaning the main MEMS structure surrounds it (Claim 1, Claim 2). By applying an electrical potential and measuring changes in capacitance between the sensing element (movable mass + reference structure) and electrodes on the substrate (Claim 16), the sensor can detect z-axis motion. The reference structure's purpose is to provide a stable baseline, helping the sensor ignore environmental changes like temperature fluctuations that might otherwise throw off its measurements, thus increasing accuracy (Abstract). For example, in a smartphone's accelerometer, this design would help ensure that a measurement of the phone dropping is accurate, even if the phone's internal temperature has changed.",
  "what_it_does_not_cover": [
    "Does not cover MEMS sensors that lack a dedicated reference structure electrically connected to the main movable sensing part.",
    "Does not cover MEMS sensors where the main movable sensing part is not positioned radially outward from the reference structure.",
    "Does not cover MEMS sensors where a surface of the reference structure is not largely on the same plane as a surface of the main movable sensing part.",
    "Does not cover MEMS sensors without a z-plane reference electrode positioned beneath the reference structure, coplanar with the z-plane MEMS electrode."
  ],
  "filed": "2012-04-02",
  "granted": "2015-01-27",
  "expires": "2032-04-02",
  "status": "active",
  "holder": "Analog Devices",
  "holder_url": "https://patentbrief.org/company/analog-devices",
  "inventors": [
    {
      "name": "Michael W. Judy",
      "url": "https://patentbrief.org/inventor/michael-w-judy"
    },
    {
      "name": "Xin Zhang",
      "url": "https://patentbrief.org/inventor/xin-zhang"
    }
  ],
  "times_cited": 4,
  "tags": [
    "consumer_electronics",
    "semiconductors",
    "telecommunications",
    "automotive",
    "aerospace"
  ],
  "abstract": "A MEMS sensor includes a substrate and a MEMS structure coupled to the substrate. The MEMS structure has a mass movable with respect to the substrate. The MEMS sensor also includes a reference structure electrically coupled to the mass of the MEMS sensor. The reference structure is used to provide a reference to offset any environmental changes that may affect the MEMS sensor in order to increase the accuracy of its measurement.",
  "url": "https://patentbrief.org/patent/us/8939029/mems-sensor-with-movable-z-axis-sensing-element-8939029",
  "markdown_url": "https://patentbrief.org/patent/us/8939029/mems-sensor-with-movable-z-axis-sensing-element-8939029/md",
  "google_patents_url": "https://patents.google.com/patent/US8939029",
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}