MEMS Tunable Capacitor with Ferroelectric Dielectric for Continuous Adjustment
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Solution Overview
Problem
Existing tunable capacitors in RF and microwave communications systems face limitations in achieving continuous capacitance tunability and large capacitance switching ratios, particularly in RF MEMS switches and electrically tunable dielectrics, which restrict their application in reconfigurable antennas and phase arrays.
Innovation Solution
A MEMS tunable capacitor design combining a movable electrode with a MEMS switch and a ferroelectric tunable dielectric, such as BST, allowing independent control of dielectric spacing and dielectric properties, enabling continuous capacitance adjustment by varying the gap between capacitor plates and tuning the dielectric material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a MEMS switch is used to control dielectric spacing, then capacitance switching ratio is improved, but continuous capacitance tunability is limited
Solution Approach 1:
The patent combines a MEMS switch mechanism with a ferroelectric tunable dielectric material in a single capacitor structure. The MEMS switch controls the spacing between capacitor plates while the ferroelectric dielectric provides continuous capacitance tuning through voltage control, merging the advantages of both technologies to achieve both high switching ratio and continuous tunability
Solution Approach 2:
The capacitor uses a composite dielectric structure combining air (or vacuum) and ferroelectric material. The ferroelectric dielectric layer is positioned between the capacitor plates, creating a composite dielectric system that enables continuous capacitance adjustment while maintaining the mechanical switching capability of the MEMS structure
2Adaptability or versatility
If a tunable dielectric is used for continuous capacitance tuning, then continuous tunability is improved, but capacitance switching ratio is reduced
Solution Approach 1:
The patent merges the tunable dielectric material with a MEMS mechanical switching mechanism in a unified capacitor design. The ferroelectric dielectric enables continuous tuning while the MEMS switch provides discrete spacing control, together achieving both high switching ratio and continuous tunability that neither component could achieve alone
3Volume of moving object
If ferroelectric dielectric with high dielectric constant is used, then device size is reduced, but device complexity increases
Solution Approach 1:
The patent exploits the voltage-dependent dielectric constant of ferroelectric materials to achieve continuous capacitance tuning. By changing the electrical parameter (applied voltage) rather than physically changing the dielectric material or geometry, the system achieves tuning functionality while maintaining a compact structure
Solution Approach 2:
The ferroelectric dielectric serves multiple functions simultaneously: it provides high dielectric constant for compact size, enables continuous capacitance tuning through voltage control, and works in conjunction with the MEMS switch to achieve both discrete switching and continuous adjustment. This multi-functionality reduces the need for additional components
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 design achieves a large continuous tuning range with improved power handling and linearity, reducing device size and parasitic resistances, while preventing electrode pull-in and allowing for full-range capacitance control, enhancing the performance of tunable antennas and filters.
Implementation Method 1
second capacitor electrode movable by a MEMS switch to vary the capacitor dielectric spacing
Implementation Method 2
ferroelectric tunable dielectric, such as BST, allowing independent control of dielectric spacing and dielectric properties
Data Source
AI summary
A MEMS tunable capacitor comprises first and second opposing capacitor electrodes, wherein the second capacitor electrode is movable by a MEMS switch to vary the capacitor dielectric spacing, and thereby tune the capacitance. A tunable dielectric material and a non-tunable dielectric material are in series between the first and second electrodes. The tunable dielectric material occupies a dimension gd of the electrode spacing, and the non-tunable dielectric material occupies a dimension g of the electrode spacing. A third electrode faces the movable second electrode for electrically controlling tunable dielectric material. A controller is adapted to vary the capacitor dielectric spacing for a first continuous range of adjustment of the capacitance of the MEMS capacitor, and to tune the dielectric material for a second continuous range of adjustment of the capacitance of the MEMS capacitor, thereby to provide a continuous analogue range of adjustment including the first and second ranges. This arrangement provides independent control of the MEMS function and the dielectric tuning function, and enables a continuous adjustability.