Variable Capacitor With Piezoelectric Actuator
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Solution Overview
Problem
Existing variable capacitance elements using MEMS technology face challenges such as large size due to the need for sufficient surface area for electrostatic actuators, high voltage requirements, and increased mass of mobile electrodes with piezoelectric actuators, leading to reduced operational efficiency and compatibility issues in battery-powered circuits.
Innovation Solution
A variable capacitance element comprising a plurality of single capacitance elements with a fixed electrode, a floating electrode, and a piezoelectric actuator, where the floating electrode is moved closer or farther from the fixed electrode using a separate drive section, allowing for controlled capacitance changes with reduced mass and voltage requirements, enabling efficient resonance and modulation control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If electrostatic actuators are used to move floating electrodes, then the variable capacitance element can be driven by relatively low voltage, but the actuator electrodes require sufficient surface area resulting in large overall area
Solution Approach 1:
The patent transitions from planar electrode arrangements to a three-dimensional stacked configuration with multiple capacitor electrode pairs arranged vertically. This dimensional change allows the floating electrode to be moved by piezoelectric actuators attached to the fixed electrode, eliminating the need for large surface area electrostatic actuator electrodes while maintaining effective capacitance control through vertical stacking of multiple capacitor units.
Solution Approach 2:
The patent replaces electrostatic actuators with piezoelectric actuators for moving the floating electrode. Piezoelectric materials convert electrical energy directly to mechanical displacement, providing sufficient actuation force without requiring large electrode surface areas, thus resolving the contradiction between low voltage operation and compact area.
2Speed
If piezoelectric actuators are used to move floating electrodes, then the response speed increases, but the dimensions of mobile electrodes must increase leading to increased mass and slowed operation
Solution Approach 1:
The patent divides the variable capacitance element into multiple discrete capacitor electrode pairs stacked vertically, with each pair having its own piezoelectric actuator. This segmentation allows the total capacitance to be achieved through parallel combination of smaller capacitor units, keeping individual mobile electrode masses low while maintaining fast response speeds through the inherent speed advantage of piezoelectric actuation.
Solution Approach 2:
The patent arranges multiple capacitor electrode pairs in the vertical dimension rather than expanding mobile electrode area in the horizontal plane. This vertical stacking achieves the required total capacitance through increased number of parallel capacitor units rather than increased size of individual electrodes, thereby maintaining low mass while achieving fast response through piezoelectric actuation.
3Reliability
If electrostatic actuators are used, then the capacitance can be changed by moving electrodes, but a relatively high voltage around 10 V is required making it difficult to use in battery-powered circuits
Solution Approach 1:
The patent replaces electrostatic actuators with piezoelectric actuators that can achieve the required electrode displacement at lower voltages suitable for battery-powered operation. Piezoelectric materials generate mechanical strain directly from applied voltage, providing sufficient actuation force at voltages compatible with portable devices while maintaining reliable capacitance control through precise displacement of the floating electrode.
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
The solution enables miniaturization, reduced power consumption, and high response speed while maintaining a large capacitance change rate, suitable for high-frequency applications and battery-powered devices, with the ability to form resonant and oscillation circuits efficiently.
Implementation Method 1
a variable capacitance element comprising a plurality of single capacitance elements with a fixed electrode, a floating electrode, and a piezoelectric actuator, where the floating electrode is moved closer or farther from the fixed electrode using a separate drive section
Data Source
AI summary
Provided is a variable capacitance element comprising a plurality of single capacitance elements that each include (i) a fixed electrode provided on a surface of a substrate, (ii) a floating electrode provided to be separate from the fixed electrode and facing the fixed electrode, and (iii) an actuator that moves the floating electrode closer to or farther from the fixed electrode; and a floating electrode driving section that supplies the actuators with drive power to move the floating electrodes, such that a combined capacitance of the plurality of single capacitance elements becomes a prescribed capacitance.