MEMS PN-Junction Sensor Eliminates Abnormal Voltage Signals
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Solution Overview
Problem
Micro-electro mechanical sensors face challenges in decoupling sensing signals for magnetic force and acceleration when using a common proof mass, leading to increased complexity in signal processing and accuracy issues.
Innovation Solution
The introduction of a micro-electro mechanical apparatus with a PN-junction, comprising a movable mass with P-type and N-type semiconductor layers, and a conductive layer, which prevents abnormal voltage variations in the readout circuit by maintaining a reverse bias, allowing for simultaneous detection of magnetic force and acceleration without signal coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a common proof mass is used to sense both magnetic force and acceleration, then the device size is reduced, but the sensing signals become coupled and signal processing complexity increases
Solution Approach 1:
The movable mass is divided into distinct functional regions: a first movable structure for magnetic force sensing and a second movable structure for acceleration sensing. This segmentation allows each structure to be optimized for its specific sensing function while sharing the same physical mass, thereby reducing overall device size while avoiding signal coupling complexity
Solution Approach 2:
Different regions of the movable mass are赋予 different properties: the first movable structure is configured with specific geometric characteristics for magnetic force detection, while the second movable structure has different geometric characteristics optimized for acceleration detection. This local differentiation enables simultaneous sensing of both physical quantities without signal interference
2Volume of moving object
If a common proof mass is used to sense both magnetic force and acceleration, then the device size is reduced, but measurement precision deteriorates due to signal coupling
Solution Approach 1:
The movable mass is divided into distinct functional regions: a first movable structure for magnetic force sensing and a second movable structure for acceleration sensing. This segmentation allows each structure to be optimized for its specific sensing function while sharing the same physical mass, thereby reducing overall device size while avoiding signal coupling
Solution Approach 2:
The first and second movable structures are designed with asymmetric geometric configurations optimized for their respective sensing functions. The first movable structure has geometry optimized for magnetic force detection, while the second movable structure has different geometry optimized for acceleration detection, enabling precise simultaneous measurement without interference
3Power
If alternating current is inputted into the coil, then magnetic force sensing is enabled, but abnormal voltage variations occur in the readout circuit
Solution Approach 1:
The harmful induced current effect is extracted and eliminated by using a direct current source instead of alternating current. The coil is driven by DC current, which produces a stable magnetic field for force sensing without causing charge accumulation and induced current artifacts in the readout circuit
Solution Approach 2:
The electrical parameter of the coil drive is changed from alternating current to direct current. This parameter change eliminates the time-varying nature of the drive signal, preventing induced current generation while maintaining the magnetic field generation capability needed for magnetic force sensing
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the accuracy of measuring magnetic force and acceleration by eliminating abnormal sensing signals and improving the sensitivity of the micro-electro mechanical apparatus, enabling more precise signal processing and reduced complexity.
Implementation Method 1
Lorentz Force F is induced by the coil 13 and the magnetic field B, which drives the movable mass 11 to rotate
Implementation Method 2
The movable mass comprises a first P-type semiconductor layer 121, a first N-type semiconductor layer 122 and a first PN-junction 123
Data Source
AI summary
A micro-electro mechanical apparatus having a PN-junction is provided. The micro-electro mechanical apparatus includes a movable mass, a conductive layer, and an electrode. The movable mass includes a P-type semiconductor layer and an N-type semiconductor layer. The PN-junction is formed between the P-type semiconductor layer and the N-type semiconductor layer. The micro-electro mechanical apparatus is capable of eliminating abnormal voltage signal when an alternating current passes through the conductive layer. The micro-electro mechanical apparatus is adapted to measure acceleration and magnetic field. The micro-electro mechanical apparatus can be other types of micro-electro mechanical apparatus such as micro-electro mechanical scanning micro-mirror.