MEMS Array Mass Tuning for Ringing and Intermodulation Control
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Solution Overview
Problem
Microelectromechanical systems (MEMS) devices experience harmonic and intermodulation distortion at higher RF power levels due to mechanical resonance and vibrational modes, leading to unwanted noise and signal distortion, especially when tone frequency spacings are small, and reliance on gas damping increases the risk of arcing and mechanical degradation.
Innovation Solution
The solution involves spreading out the resonant frequencies of individual MEMS elements by selectively varying the masses of the beams, either by adding or subtracting mass from non-active areas, and customizing the drive signal characteristics, such as capacitance and resistance values, to create a spread-spectrum noise floor, reducing the magnitude of noise tones and mitigating ringing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If MEMS devices operate at higher RF power levels, then signal strength is improved, but harmonic and intermodulation distortion increases due to mechanical resonance and vibrational modes
Solution Approach 1:
The patent applies local quality by varying the mass of individual MEMS elements within the array. Each element has a customized mass that shifts its resonant frequency, creating local differences in dynamic characteristics. This ensures that when operating at higher RF power levels, the distortion products from individual elements are spread across different frequencies rather than concentrating at a single resonant frequency, thereby reducing overall harmonic and intermodulation distortion.
Solution Approach 2:
The patent implements parameter changes by modifying the mass parameter of MEMS elements to alter their resonant frequencies. By changing the mass of individual elements, the system shifts the resonant frequencies away from the operating frequency and its harmonics. This parameter modification allows the device to operate at higher RF power levels without exciting mechanical resonance that would generate excessive distortion.
2Productivity
If tone frequency spacing is reduced, then channel capacity is improved, but beat frequency and harmonic products increase leading to unwanted noise
Solution Approach 1:
The patent applies local quality by assigning different masses to individual MEMS elements, creating local variations in resonant frequency. When multiple elements are operated simultaneously with small tone frequency spacing, each element's unique resonant frequency prevents synchronized beating and harmonic product generation, thereby maintaining high channel capacity while reducing unwanted noise.
Solution Approach 2:
The patent implements preliminary action by pre-configuring the mass distribution of MEMS elements before operation. This preliminary mass customization ensures that resonant frequencies are already spread out and do not coincide with tone frequencies or their harmonics, preventing beat frequency and harmonic product issues before they can occur during high-capacity multi-tone operation.
3Stability of the object's composition
If gas damping is used to reduce ringing, then mechanical resonance is suppressed, but risk of arcing and mechanical degradation increases
Solution Approach 1:
The patent replaces the mechanical gas damping system with an electrical solution. By varying the mass of MEMS elements to shift resonant frequencies away from operating frequencies, the system eliminates mechanical ringing without requiring gas damping. This substitution removes the gas environment that would otherwise be needed, thereby eliminating the risk of arcing and gas-related mechanical degradation while maintaining ringing suppression.
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 approach effectively reduces intermodulation distortion and harmonic products by distributing noise energy across a wider frequency spectrum, reducing the likelihood of arcing and mechanical degradation, while maintaining device performance without increasing production costs or complexity.
Implementation Method 1
Ohmic MEMS switches are controlled by electrostatically controlled cantilevers, clamped beams or plates
Implementation Method 2
A capacitive MEMS switch or varactor uses a moving plate, beam, diaphragm, comb or sensing element, which changes the capacitance
Implementation Method 3
a first movable electrostatic plate elastically connected to a first structure
Data Source
AI summary
Described embodiments include a microelectromechanical system (MEMS) array comprising a first MEMS device that includes a first movable electrostatic plate elastically connected to a first structure, the first movable electrostatic plate having a first mass, a first fixed electrostatic plate, and a first drive circuit having a first drive output coupled to the first fixed electrostatic plate. There is a second MEMS device that includes a second movable electrostatic plate elastically connected to a second structure, the second movable electrostatic plate having a second mass that is different than the first mass, a second fixed electrostatic plate, and a second drive circuit having a second drive output coupled to the second fixed electrostatic plate.