Improving MEMS Sensor Accuracy with a Co-located Reference Structure
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.
Original patent title: “MEMS sensor with movable Z-axis sensing element”
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. Granted to Analog Devices in 2015 with 21 claims and 4 forward citations, and it is expected to expire in 2032.
Coverage
What does this patent actually cover?
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 (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 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 (AbstractabstractA short summary at the front of the patent describing the invention. Not legally binding.Read more →). 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.
The gap
What does this patent 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.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The innovation lies in integrating a separate, electrically coupled reference structure directly with the movable sensing mass, and arranging the main MEMS structure radially outward from it. This specific arrangement allows the reference to effectively cancel out common-mode environmental noise, significantly boosting measurement accuracy without needing complex external compensation.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Smartphone accelerometers for screen rotation and step counting
Wearable fitness trackers for activity monitoring
Automotive airbag deployment sensors
Industrial control systems requiring precise vibration monitoring
Drone flight stabilization systems
Why it matters
The bigger picture
Accurate z-axis motion sensing is vital for many modern devices, from stabilizing drone flight to precisely tracking activity in wearables. This patent's approach to using an integrated reference structure helps ensure that these tiny sensors provide reliable data, even in changing conditions. This reliability is crucial for the performance and safety of products that depend on precise motion detection.
Filed
April 2, 2012
Granted
January 27, 2015
Market context
Who's building on this
Companies in this space
Analog Devices Inc., the assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, is a leading global manufacturer of high-performance analog, mixed-signal, and digital signal processing integrated circuits, including MEMS sensors. Other major players in the MEMS sensor market, such as Bosch Sensortec, STMicroelectronics, and NXP Semiconductors, continuously develop and refine sensor designs for improved accuracy and reliability across various applications.
Market impact
This patent contributes to the ongoing drive for higher accuracy and reliability in MEMS sensors. By providing a method to inherently compensate for environmental variations, it enables the development of more robust and precise devices. This directly impacts markets requiring stable motion sensing, from consumer electronics like smartphones and wearables to critical applications in automotive safety systems and industrial automation, fostering trust in sensor data and enabling new functionalities.
Claim 1 — Plain English
What this patent covers
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.
The clever bit
The innovation lies in integrating a separate, electrically coupled reference structure directly with the movable sensing mass, and arranging the main MEMS structure radially outward from it. This specific arrangement allows the reference to effectively cancel out common-mode environmental noise, significantly boosting measurement accuracy without needing complex external compensation.
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.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
PatentBrief Score
Impact Score
Early stage
Citation count
14/40
Early citations
Claim breadth
14/20
Broad claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
5/20
Granted 10–20 years ago
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$51K – $164K
Midpoint $102K · 5.5 yr remaining · industry ×1.5
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
The original legal language
Original claims
21 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Judy, M. W., & Zhang, X. (2015). Improving MEMS Sensor Accuracy with a Co-located Reference Structure (U.S. Patent No. 8,939,029). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/8939029/mems-sensor-with-movable-z-axis-sensing-element-8939029
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does Improving MEMS Sensor Accuracy with a Co-located Reference Structure cover?
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.
Who owns patent US 8939029?
Analog Devices owns this patent, granted in 2015.
When does this patent expire?
This patent is expected to expire on April 2, 2032, when the invention enters the public domain.
What is patent US 8939029 cited by?
This patent has been cited by 4 later patents that build on its ideas.
What problem does this patent solve?
Accurate z-axis motion sensing is vital for many modern devices, from stabilizing drone flight to precisely tracking activity in wearables. This patent's approach to using an integrated reference structure helps ensure that these tiny sensors provide reliable data, even in changing conditions. This reliability is crucial for the performance and safety of products that depend on precise motion detection.
What does this patent NOT cover?
Does not cover MEMS sensors that lack a dedicated reference structure electrically connected to the main movable sensing part.
Same assignee
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