Segmented MEMS Bridge Switches With Lower RF Parasitics
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Solution Overview
Problem
Existing MEMS switches face issues with insufficient differences in electrical parameter values between up and down states, significant parasitic capacitances and inductances, and damage from stresses and strains during movement.
Innovation Solution
A MEMS device with a substrate, signal conductor, ground conductors, and a MEMS bridge having switching signal and ground conductor regions that are movable to change capacitances or resistances, eliminating the need for a continuous conductive path through the bridge, reducing insertion loss, and distributing mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a continuous electrically conductive path is provided through the MEMS bridge from the switching signal conductor region to the anchor, then mechanical support and structural stability are improved, but parasitic capacitances and inductances increase, degrading electrical performance
Solution Approach 1:
The MEMS bridge is segmented into electrically isolated conductive regions (signal conductor region and ground conductor region) that are mechanically connected but electrically separated by dielectric layers. This segmentation allows the bridge to maintain structural integrity through mechanical connectivity while eliminating continuous electrical pathways that generate parasitic effects.
Solution Approach 2:
Dielectric layers are introduced as intermediary materials between conductive regions of the MEMS bridge. These dielectric layers provide mechanical support and structural stability while electrically isolating adjacent conductive regions, thereby preventing the formation of continuous conductive paths that would create parasitic capacitances and inductances.
2Reliability
If the MEMS bridge is made robust to withstand stresses and strains during movement between up and down states, then reliability is improved, but the bridge becomes more prone to damage from the very stresses it must bear
Solution Approach 1:
The MEMS bridge is divided into multiple conductive regions separated by dielectric layers, creating a modular structure where stresses and strains are distributed across multiple interfaces rather than concentrated in a single continuous conductive path. This segmentation enhances the bridge's ability to withstand operational stresses while maintaining structural integrity.
Solution Approach 2:
The MEMS bridge employs composite construction with alternating layers of conductive materials and dielectric materials. This composite structure provides both mechanical strength to withstand stresses and strains during actuation, while the dielectric layers prevent electrical breakdown and damage under stress conditions.
3Ease of operation
If the difference in electrical parameter values between up and down states is increased, then switching performance is improved, but parasitic effects become more significant, offsetting the gains
Solution Approach 1:
By segmenting the bridge into isolated conductive regions, the patent achieves large changes in capacitance and resistance between up and down states without creating continuous conductive paths. The segmented structure allows electrical parameters to vary significantly with bridge position while minimizing parasitic effects that would otherwise limit switching performance.
Solution Approach 2:
The patent utilizes changes in electrical parameters (capacitance, resistance) as the bridge moves between up and down states. The segmented structure with dielectric layers enables these parameter changes to be maximized while keeping parasitic capacitances and inductances minimized, thereby improving overall switching performance.
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 enhances the difference in electrical properties between states, reduces parasitic effects, and minimizes stress on the MEMS bridge, leading to improved performance and reliability in RF applications.
Implementation Method 1
A MEMS switch comprises a signal line support on a substrate and a MEMS bridge, which is moveable relative to the signal line between the first and second states, thereby changing at least one capacitance and/or resistance
Implementation Method 2
the electrically conductive switching region being movable, relative to the substrate, between first and second positions, to thereby change the impedance (e.g. capacitances) between the switching signal conductor region and the signal conductor
Data Source
AI summary
A microelectromechanical systems (MEMS) device comprising: a substrate; a signal conductor supported on the substrate; ground conductors supported on the substrate on either side of the signal conductor; and a MEMS bridge at least one end of which is mechanically connected to the substrate by way of at least one anchor, the MEMS bridge comprising an electrically conductive switching portion, the electrically conductive switching portion comprising a switching signal conductor region and a switching ground conductor region, the switching signal conductor region being provided over the signal conductor and the switching ground conductor region being provided over a said ground conductor, the electrically conductive switching region being movable relative to the said signal and ground conductors respectively to thereby change the inductances between the switching signal conductor region and the signal conductor and between the switching ground conductor region and the respective ground conductor, wherein there is no continuous electrically conductive path extending from the switching conductor region to the at least one anchor. Capacative and ohmic switches, a varactor, a phase shifter, a tuneable power splitter/combiner, tuneable attenuator, SPDT switch and antenna apparatus comprising said devices.