MEMS-Switched Piezoelectric Filters for Band Switching and Tuning
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Solution Overview
Problem
Existing SAW and BAW filters face challenges in programming or tuning, making it difficult to achieve desired frequency adjustments and signal processing functions.
Innovation Solution
The implementation of a Micro-Electro-Mechanical System (MEMS) structure that interleaves or sandwiches electrodes with a piezoelectric substrate to switch the filters between 'on' and 'off' states, allowing for tunability and band switching by actuating a MEMS beam, which can also apply mechanical loads to shift resonant frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If SAW filters are designed with complex signal processing functions using only piezoelectric substrate with interdigital transducers, then the filters can be mass-produced with outstanding reproducibility, but programming or tuning of the SAW filters becomes difficult to achieve
Solution Approach 1:
The filter structure is segmented into multiple independently controllable resonator groups, where each group can be selectively activated or deactivated. This allows the filter to maintain a simple mass-producible base structure while enabling programmable tuning by controlling which segments are active, thus resolving the contradiction between ease of manufacture and adaptability
Solution Approach 2:
The patent introduces variable capacitors or switches that dynamically change the electrical characteristics of the filter by altering the connection states of different resonator groups. This dynamic reconfiguration capability enables tuning and programming functions without changing the physical structure, maintaining ease of manufacture while achieving adaptability
2Adaptability or versatility
If BAW filters are designed with adjustable acoustic resonant characteristics by changing piezoelectric film thickness or applying mass loading, then the resonance frequency can be shifted, but programming or tuning of the BAW filter becomes difficult to achieve
Solution Approach 1:
Instead of changing physical parameters like film thickness or mass loading during manufacturing, the patent uses electrical parameter changes by introducing variable capacitors that modify the resonant frequency through electrical control. This allows frequency tuning without altering the physical structure, making programming easier while maintaining frequency adjustability
Solution Approach 2:
The patent replaces mechanical tuning methods (such as mass loading or thickness adjustment) with electrical control mechanisms. By using variable capacitors and electronic switches, the resonant characteristics are adjusted through electrical fields rather than mechanical modifications, simplifying the programming and tuning process while maintaining frequency adaptability
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
Enables efficient switching and tuning of SAW and BAW filters, improving their programmability and adaptability to various frequency requirements, enhancing their performance in telecommunications and wireless applications.
Implementation Method 1
when an AC voltage is applied to input transducers (electrodes), due to piezoelectricity, the transducer produces mechanical deformation of the piezoelectric substrate surface
Implementation Method 2
The mass loading effect can be accomplished by depositing or growing a mass of film on the resonator to bring about downshifting of the resonance frequency of the FBAR
Data Source
AI summary
Switchable and/or tunable filters, methods of manufacture and design structures are disclosed herein. The method of forming the filters includes forming at least one piezoelectric filter structure comprising a plurality of electrodes formed to be in contact with at least one piezoelectric substrate. The method further includes forming a micro-electro-mechanical structure (MEMS) comprising a MEMS beam in which, upon actuation, the MEMS beam will turn on the at least one piezoelectric filter structure by interleaving electrodes in contact with the piezoelectric substrate or sandwiching the at least one piezoelectric substrate between the electrodes.