MEMS Variable Capacitor Linear Tuning via Segmented Electrodes
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Solution Overview
Problem
Existing RF block variable capacitors face challenges in maintaining consistent phase noise characteristics due to non-linear capacitance variation with applied voltage.
Innovation Solution
A MEMS variable capacitor design featuring a first electrode, a floated second electrode, and a fixed third electrode with adjustable gap, supported by spring structures, allowing capacitance adjustment through voltage application from separate electrodes, ensuring RF signals do not interfere with mechanical spring structures, thereby achieving linear capacitance variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage is applied to adjust capacitance in conventional variable capacitors, then capacitance value changes, but capacitance variation is non-linear causing inconsistent phase noise characteristics
Solution Approach 1:
The capacitor structure is segmented into multiple electrodes (first electrode, second electrode, third electrode) with distinct functional roles. The first and second electrodes form the RF signal path, while the third electrode is dedicated to capacitance adjustment via voltage application, separating the RF signal function from the tuning function to achieve linear capacitance variation.
Solution Approach 2:
The third electrode acts as an intermediary element that mediates between the applied voltage and the capacitance adjustment. By applying voltage to the third electrode rather than directly to the RF electrodes, the patent achieves linear capacitance variation and consistent phase noise characteristics.
2Adaptability or versatility
If RF signal is applied across electrodes used for capacitance adjustment, then capacitance can be tuned, but mechanical spring structures are exposed to RF signals causing reduced Q value
Solution Approach 1:
The electrode system is segmented into RF signal electrodes (first and second electrodes) and a tuning electrode (third electrode). This segmentation allows the RF signal to be confined to specific electrodes while the tuning electrode handles capacitance adjustment, preventing RF exposure of mechanical structures and maintaining high Q value.
Solution Approach 2:
The capacitance tuning function is extracted from the RF signal path by using a separate third electrode. The voltage for capacitance adjustment is applied to the third electrode, which is electrically isolated from the RF signal path, thereby protecting the mechanical spring structures from RF exposure and preserving high Q value.
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 enables consistent phase noise characteristics and high Q values by isolating RF signals from mechanical structures and providing linear capacitance variation with voltage adjustments.
Implementation Method 1
the second electrode is floated from the first electrode by spring structures
Implementation Method 2
a first electrode, a second electrode that is floated on the first electrode, and a fixed third electrode capable of variably-adjusting a capacitance value by adjusting a gap between the first electrode and the second electrode
Data Source
AI summary
Disclosed is a MEMS variable capacitor, the capacitor including a first electrode, a second electrode that is floated on an upper surface of the first electrode, and a third electrode capable of variably-adjusting a capacitance value by adjusting a gap between the first electrode and the second electrode.