MEMS Tunable Filter Bank Using Common Geometry GCA Devices
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Solution Overview
Problem
Conventional filter banks for RF communications are large in size and consume high power due to the use of discrete components, and MEMS-based solutions are complex to manufacture with different geometries for switches and capacitors, leading to increased costs and complexity.
Innovation Solution
The use of MEMS horizontal gap closing actuator (GCA) devices with common geometries to form both switches and adjustable capacitors, allowing for the fabrication of filter banks with reduced complexity and cost, using either thick metal inductors or without them, to create various filter types such as low pass, high pass, band pass, and band stop filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If discrete components are used to form filter banks, then frequency coverage is achieved, but device size becomes large
Solution Approach 1:
The patent combines multiple filter functions into a single integrated MEMS device structure. Multiple capacitive elements are integrated within one chip, eliminating the need for separate discrete components for each filter function, thus reducing overall device size while maintaining broad frequency coverage
Solution Approach 2:
The MEMS filter bank is designed to perform multiple filter functions (low-pass, high-pass, band-pass, band-stop) within a single device. The same physical structure can be configured to provide different filter responses, making the device universal and eliminating the need for multiple separate filters
2Area of stationary object
If miniature filters are used to reduce size, then device dimensions are reduced, but power consumption increases
Solution Approach 1:
The patent replaces traditional active filter components (operational amplifiers, transistors) with passive MEMS capacitive elements. The filtering function is achieved through mechanical displacement of MEMS structures that modify capacitive coupling, eliminating the need for high-power active components while maintaining small device dimensions
3Adaptability or versatility
If MEMS devices with different geometries are used for switches and capacitors, then functionality is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent employs a single MEMS comb drive structure that can serve multiple functions. By controlling the displacement and configuration of the same basic structure, the device can function as both switches and capacitors, eliminating the need for different geometries and simplifying the manufacturing process
Solution Approach 2:
The patent uses dynamically reconfigurable MEMS structures where the same physical element can change its function based on its state. The comb drive structure can be positioned to create capacitive coupling for filtering or to establish conductive paths for switching, allowing one geometry to perform multiple functions
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 approach results in a more compact and power-efficient filter bank design with simplified manufacturing, capable of operating over a wide range of frequencies with fewer components, reducing overall size and development costs while maintaining reliable performance.
Implementation Method 1
A micro-electro-mechanical system (MEMS) filter bank employs horizontal gap closing actuator (GCA) devices with common geometries to form both switches and adjustable capacitors
Data Source
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Figure 3A~3C
AI summary
A filter device is provided including a substrate (302) and a plurality of horizontal gap closing actuator (GCA) devices (550) disposed on a first surface of the substrate. The plurality of GCA devices includes and one or more GCA varactors (700). Each one of the plurality of horizontal GCA devices includes at least one drive comb structure (602a, 602b, 702a, 702b), at least one input/output (I/O) comb structure (616a, 676b, 716a, 716b), and at least one truss comb structure (604, 704) interdigitating the drive comb and the I/O comb structures. The truss comb structure is configured to move along a motion axis between at least a first interdigitated position and a second interdigitated position based on a bias voltage applied between the truss comb structure and the drive comb structure.