Tunable SAW Filter with Electrostatic Actuator
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Solution Overview
Problem
Existing SAW filters face challenges in programming or tuning, making it difficult to achieve desired frequency responses and signal processing functions within a single package.
Innovation Solution
The development of switchable and tunable SAW filters using a moveable ground electrode and actuators that can be electro-statically moved to interleave with fixed electrodes, allowing for activation or deactivation of the filter, enabling frequency tuning by adjusting the position of the electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a moveable electrode structure with actuators is implemented, then the filter becomes tunable and switchable, but the device complexity increases
Solution Approach 1:
The patent implements a moveable ground electrode that can be dynamically repositioned relative to the IDT fingers using electrostatic actuators. This dynamic structure allows the filter to be tuned to different frequencies by changing the overlap between the moveable electrode and fixed electrodes, enabling adaptability while maintaining a relatively simple overall architecture.
Solution Approach 2:
The patent changes the physical position parameter of the ground electrode to achieve frequency tuning. By electrostatically moving the ground electrode to different positions, the electrical characteristics of the filter are modified, allowing the same physical structure to operate at multiple frequencies without requiring multiple fixed filter designs.
2Adaptability or versatility
If electrostatic actuators are used to move the moveable electrode, then frequency tuning is enabled, but manufacturing precision requirements increase
Solution Approach 1:
The patent replaces traditional mechanical tuning mechanisms with electrostatic actuators. Instead of using mechanical screws, levers, or motors to adjust electrode positions, the invention uses electrostatic forces to move the ground electrode, eliminating complex mechanical transmission components and reducing the associated manufacturing precision requirements for mechanical parts.
Solution Approach 2:
The moveable ground electrode is implemented as a thin film structure that can be electrostatically actuated. This thin film approach allows for precise positioning through electrical control while being compatible with standard semiconductor fabrication processes, reducing the need for high-precision mechanical assembly.
3Reliability
If the moveable electrode is positioned to interleave with fixed electrodes, then the filter activates, but the risk of misalignment increases
Solution Approach 1:
The patent uses electrostatic fields as an intermediary mechanism to achieve precise alignment of the moveable electrode with the fixed electrodes. The electrostatic attraction between charged surfaces provides a self-aligning force that guides the moveable electrode into the correct interleaved position, reducing the risk of misalignment compared to purely mechanical positioning methods.
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 allows for efficient switching and tuning of SAW filters without adding series resistance or decreasing the effective Q factor, enabling precise control over signal propagation and frequency response.
Implementation Method 1
electro-statically moving a moveable electrode of the filter by applying a drive voltage to at least one actuator
Implementation Method 2
when an AC voltage is applied to input transducers, due to piezoelectricity, the transducer produces mechanical deformation of the piezoelectric substrate surface
Data Source
AI summary
Switchable and/or tunable filters, methods of manufacture and design structures are provided herein. The method of forming the filters includes forming at least one piezoelectric filter structure comprising a plurality of electrodes formed on a piezoelectric substrate. The method further includes forming a fixed electrode with a plurality of fingers on the piezoelectric substrate. The method further includes forming a moveable electrode with a plurality of fingers over the piezoelectric substrate. The method further includes forming actuators aligned with one or more of the plurality of fingers of the moveable electrode.