{
  "patent_number": "US 8146425",
  "country": "US",
  "title": "How a MEMS Sensor Uses a Reference to Improve Z-Axis Accuracy",
  "original_title": "MEMS sensor with movable z-axis sensing element",
  "summary": "This patent describes a tiny sensor that measures up-and-down motion more accurately by including a special surrounding structure that helps cancel out environmental interference.",
  "what_it_does": "This MEMS (Micro-Electro-Mechanical System) sensor improves accuracy by using a dedicated reference structure. The sensor includes a main MEMS structure with a part that can move, called a movable mass, all built on a substrate. Crucially, a separate reference structure is placed radially outward from the main MEMS structure and is electrically connected to the movable mass (Claim 1). This setup allows the sensor to measure changes in capacitance between the movable part and an electrode on the substrate (Claim 16). By comparing or offsetting measurements using the reference structure, the sensor can become more accurate, especially for detecting motion along the z-axis (up and down). For example, if temperature changes affect the entire chip, the reference structure helps the sensor distinguish actual motion from environmental noise.",
  "what_it_does_not_cover": [
    "Does not cover MEMS sensors that do not include a separate reference structure.",
    "Does not cover reference structures that are not positioned radially outward from the main MEMS structure.",
    "Does not cover reference structures that are not electrically connected to the movable mass of the MEMS structure.",
    "Does not cover MEMS sensors that measure motion using methods other than changes in capacitance.",
    "Does not cover MEMS sensors primarily designed for motion sensing along the x or y axes, as the claims focus on z-axis measurement."
  ],
  "filed": "2008-09-05",
  "granted": "2012-04-03",
  "expires": "2028-09-05",
  "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": 22,
  "tags": [
    "semiconductors",
    "consumer_electronics",
    "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 positioned radially outward from the MEMS structure. 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/8146425/mems-sensor-with-movable-z-axis-sensing-element",
  "markdown_url": "https://patentbrief.org/patent/us/8146425/mems-sensor-with-movable-z-axis-sensing-element/md",
  "google_patents_url": "https://patents.google.com/patent/US8146425",
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  ]
}