Tri-state RF MEMS Switch With Latching Membrane
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Solution Overview
Problem
Conventional RF switches only offer one or two output signals per input signal and lack a latching mechanism to maintain the output signal when the input voltage is removed, increasing device complexity and requiring a more complex configuration to achieve three output signals.
Innovation Solution
A tri-state RF switch design featuring a membrane with conductive pads that can latch into one of three states, allowing three output signals per input signal, with a latching mechanism that maintains the state even when the input voltage is removed, utilizing a membrane with compressive stress and conductive pads to contact signal lines across gaps between substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional RF switches are used to provide multiple output signals, then the number of output signals can be increased, but the device complexity increases significantly
Solution Approach 1:
The device is segmented into three distinct wells (first well, second well, third well) formed in the substrate, with each well containing separate signal lines and driving electrodes. This segmentation allows independent control of three output signals while maintaining a unified structural framework, resolving the contradiction between providing multiple outputs and maintaining simplicity.
Solution Approach 2:
The membrane structure serves multiple functions simultaneously: it acts as a mechanical element that can deflect to connect different signal lines, provides latching capability through its bistable design, and enables three-state operation. This multi-functionality allows a single membrane structure to replace what would traditionally require multiple separate switches, reducing overall device complexity while providing three output signals.
2Reliability
If conventional RF switches are used without latching mechanism, then the device structure remains simple, but the output signal cannot be maintained when input voltage is removed
Solution Approach 1:
The membrane is pre-stressed during fabrication to create a bistable structure with two stable equilibrium positions. This preliminary action of introducing residual stress during manufacturing enables the membrane to maintain its deflected state without continuous driving voltage, providing latching functionality. The prestress is introduced through controlled deposition conditions or subsequent heat treatment processes that create internal stress in the membrane layers.
Solution Approach 2:
The membrane's mechanical parameters (stress state, curvature) are changed during fabrication to create a bistable system. By controlling the deposition conditions, thickness, and material composition of the membrane layers, the system achieves two stable states that correspond to the latched positions. This parameter change from a single-stable to a bistable configuration enables signal maintenance without continuous power input.
3Adaptability or versatility
If a tri-state RF switch is implemented using conventional switches, then three output signals can be achieved, but the configuration becomes more complex
Solution Approach 1:
Three separate switch functions are merged into a single membrane structure that can simultaneously or sequentially connect to three different output signal lines. The membrane's ability to deflect toward different driving electrodes allows one physical element to perform the function of three separate switches, simplifying the configuration while maintaining three-output capability.
Solution Approach 2:
The switch mechanism transitions from a planar two-dimensional configuration to a three-dimensional structure with the membrane deflecting in the vertical dimension. This dimensional change allows the membrane to access multiple output states by deflecting toward different wells, enabling tri-state operation without requiring multiple separate planar switch 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
The tri-state RF switch simplifies the device configuration by providing three output signals per input signal and maintains a stable output state without the need for continuous input voltage, reducing complexity and enhancing signal stability.
Implementation Method 1
The membrane may be formed with a predetermined compressive stress
Implementation Method 2
a first driving electrode formed in the first well; a second driving electrode and a third driving electrode formed in the second well and the third well, respectively
Data Source
AI summary
A tri-state RF MEMS switch includes: a first well formed in a first substrate; a first input signal line and a first output signal line forming a first gap therebetween in the first well; a post bar forming a boundary between the second well and third well in the second substrate; a second input signal line and a second output signal line, and a third input signal line and a third output signal line forming a second gap and a third gap in the second well and the third well, respectively; and a membrane disposed between the first substrate and the second substrate such that the membrane crosses the first, second and third gaps, the membrane including a first conductive pad, a second conductive pad, and a third conductive pad thereon to face the first, second and third gaps, respectively.