Varactor With Dual Membranes Resisting Acceleration
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Solution Overview
Problem
MEMS-based varactors are sensitive to mechanical vibrations and accelerations, making it difficult to maintain a stable and adjustable capacitance value, which is undesirable for applications in information technology and high-frequency technology.
Innovation Solution
A varactor design with two movable membranes and a rigid substrate, where both membranes move in the same direction under acceleration, maintaining a constant capacitance value by adjusting the distance between the membranes and the actuator surfaces, and using a parallel connection of capacitance values to achieve a stable total capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single movable membrane is used in the varactor, then the structure is simple, but the capacitance value becomes sensitive to acceleration and mechanical vibrations
Solution Approach 1:
The single movable membrane is divided into two separate movable membranes (first and second movable membranes) positioned on opposite sides of the substrate. Each membrane forms its own capacitor with the actuator electrode, and their combined effect compensates for acceleration-induced capacitance variations while maintaining structural simplicity.
2Adaptability or versatility
If the distance between membrane and actuator is varied to adjust capacitance, then the capacitance tuning range is improved, but the sensitivity to acceleration increases
Solution Approach 1:
The two movable membranes are positioned symmetrically on opposite sides of the substrate at equal distances from the actuator electrode. When acceleration occurs, one membrane moves closer to the actuator while the other moves farther away, creating opposing capacitance changes that cancel each other out, thereby eliminating acceleration sensitivity while preserving full capacitance tuning capability.
3Reliability
If a rigid substrate is used to reduce acceleration sensitivity, then the capacitance stability is improved, but the device complexity increases
Solution Approach 1:
The rigid substrate serves as a fixed reference plane positioned equidistantly between the two movable membranes. This equipotential positioning ensures that acceleration forces affect both membranes equally and oppositely, allowing the substrate to provide mechanical stability without requiring complex active compensation mechanisms.
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 varactor provides a capacitance value that is insensitive to acceleration and mechanical vibrations, allowing for adjustable and stable operation, while also being resistant to interference and capable of fine-tuning within a large capacitance range.
Implementation Method 1
If a direct voltage is applied between the actuator electrode and the metallic membrane, the electrostatic forces of the actuator cause a displacement of the membrane
Implementation Method 2
The actuator electrode and the metallic membrane represent a plate capacitor from which a capacitance value can be tapped
Data Source
AI summary
The invention relates to a varactor with an actuator, wherein the first actuator surface (2a) of the actuator is embodied on a substrate (1), and a second actuator surface (2b) is embodied on a first movable membrane (3a). In this context, the first movable membrane (3a) is arranged above an upper side (1a) of the substrate (1). A second movable membrane (2b) is arranged below a lower side (1b) of the substrate (1) facing away from the upper side (1a). The invention further relates to a varactor system made from two such varactors.