Micromachined RF Switch and Filter Using LIGA Process
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Solution Overview
Problem
Conventional methods for fabricating microwave filters and RF switches are labor-intensive, capital-intensive, and result in large resonant structures, limiting the miniaturization of microwave components, while existing waveguide fabrication processes do not efficiently incorporate high-Q and low-volume filters or low-loss RF switches.
Innovation Solution
The use of micromachined quasi-lumped elements and a comb drive-based RF switch fabricated during the LIGA process, where patterns for waveguides and signal controllers are created on a mask, allowing for the integration of filters and switches within the waveguide, utilizing a sacrificial layer for movable parts and electroplating for conductor formation, enabling high-aspect ratio waveguides and reduced volume components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional methods are used to fabricate microwave filters and RF switches, then the manufacturing process is labor-intensive and capital-intensive, but the component volume remains large
Solution Approach 1:
The patent combines the fabrication of waveguides, filters, and RF switches into a single integrated LIGA manufacturing process. Multiple components that would traditionally be manufactured separately are now fabricated simultaneously in one monolithic structure, reducing overall component volume while maintaining manufacturing feasibility through process integration
Solution Approach 2:
The LIGA process enables three-dimensional micromachining with high aspect ratios, allowing filters and switches to be embedded within the waveguide structure rather than being separate planar components. This vertical integration into the third dimension significantly reduces the overall volume occupied by these microwave components
2Volume of moving object
If large resonant structures are used as filters during waveguide fabrication, then the filter Q is adequate, but the filter volume is large
Solution Approach 1:
The filter is segmented into discrete quasi-lumped elements (capacitors and inductors) rather than using a single large resonant structure. This segmentation allows the filter to be miniaturized while maintaining the necessary resonant characteristics through the coordinated arrangement of smaller functional elements
Solution Approach 2:
The patent transitions from distributed resonant structures to quasi-lumped element equivalents by changing the electrical parameters and physical dimensions of the filter components. This parameter transformation enables significant volume reduction while preserving the filter's quality factor through optimized lumped element designs
3Loss of energy
If conventional RF switch fabrication methods are used, then the switch can be manufactured, but the process is time-intensive and the switch loss is high
Solution Approach 1:
The RF switch fabrication is merged with the waveguide and filter manufacturing process. The same LIGA steps used to create the waveguide structure and filter elements are also used to form the switch components, eliminating separate fabrication steps and reducing overall manufacturing time while achieving low-loss performance through integrated design
Solution Approach 2:
A sacrificial layer is used as an intermediary during the electroplating process to enable the formation of movable switch parts. This temporary layer facilitates the creation of complex switch geometries with precise tolerances that would be difficult to achieve directly, resulting in low-loss switches while maintaining process efficiency
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 high-Q filters with reduced volume and low-loss RF switches, achieving efficient signal control with minimal insertion loss and compact size, suitable for microwave telemetry transmitters and receivers.
Implementation Method 1
When an actuating voltage is applied to the anchors, the comb drive draws the metal plunger into a gap on the coplanar waveguide to short the lines and shut off the transmission
Implementation Method 2
When the actuating voltage is removed, the spring will return the plunger to its normal position, and the signal transmission starts
Implementation Method 3
Radiation travels through the mask and reaches a photoresist layer on a substrate. The irradiated portions are removed and channels are formed on the substrate
Implementation Method 4
A metal is filled into the channels to form the conductors of the waveguide and the signal controllers
Data Source
AI summary
A method for fabricating a signal controller, e.g., a filter or a switch, for a coplanar waveguide during the LIGA fabrication process of the waveguide. Both patterns for the waveguide and patterns for the signal controllers are created on a mask. Radiation travels through the mask and reaches a photoresist layer on a substrate. The irradiated portions are removed and channels are formed on the substrate. A metal is filled into the channels to form the conductors of the waveguide and the signal controllers. Micromachined quasi-lumped elements are used alone or together as filters. The switch includes a comb drive, a spring, a metal plunger, and anchors.