Wire-Based MEMS Switches Harvest RF Energy for Low Power IoT
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Solution Overview
Problem
Conventional silicon-on-insulator (SOI) switches in wireless devices exhibit high on-resistance and off-capacitance, leading to degraded RF efficiency and performance due to higher figure-of-merit, which can be improved by replacing them with microelectromechanical systems (MEMS) switches.
Innovation Solution
A wire-based MEMS apparatus featuring a MEMS control bus and passive MEMS switch circuits that generate a constant voltage exceeding a threshold, eliminating the need for active components and reducing power consumption by harnessing RF voltage from an RF signal, thereby enabling low-power operation for applications like the Internet-of-Things (IoT).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional SOI switches are used, then device integration is straightforward, but on-resistance and off-capacitance increase leading to degraded RF efficiency
Solution Approach 1:
The patent replaces conventional electronic SOI switches with MEMS switches that use mechanical movement of a movable electrode to control electrical connectivity. This mechanical substitution enables near-zero on-resistance when closed and near-zero off-capacitance when open, dramatically improving RF efficiency while maintaining manufacturability through established MEMS fabrication processes
2Ease of operation
If active components are used in MEMS control circuits, then switching control is achieved, but leakage and power consumption increase
Solution Approach 1:
The patent employs passive MEMS switch circuits that harvest energy from the RF control signals themselves to actuate the MEMS switches. The circuits use energy recovery techniques where energy stored in capacitors during the off-state is reused during the on-state transition, eliminating the need for external power sources and active components, thereby achieving zero static power consumption and minimal leakage
Solution Approach 2:
The patent changes the operational parameters of the MEMS switch control by using high-voltage RF signals (e.g., 30-50V) that can directly charge the MEMS capacitor to exceed the pull-in voltage threshold. This parameter change allows the switch to be actuated by the RF signal itself without requiring additional active control components, reducing power consumption while maintaining effective switching control
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 reduces leakage and power consumption, enhancing RF efficiency and performance by utilizing passive MEMS switches with a lower figure-of-merit compared to conventional SOI switches, thus supporting improved wireless device functionality.
Implementation Method 1
The passive MEMS switch circuit can generate the constant voltage(s) based on a radio frequency (RF) voltage(s), which may be harvested from an RF signal(s) received via the MEMS control bus
Data Source
AI summary
A wire-based microelectromechanical systems (MEMS) apparatus is provided. In examples discussed herein, the wire-based MEMS apparatus includes a MEMS control bus and at least one passive MEMS switch circuit. The passive MEMS switch circuit is configured to close a MEMS switch(es) by generating a constant voltage(s) that exceeds a defined threshold voltage (e.g., 30-50 V). In a non-limiting example, the passive MEMS switch circuit can generate the constant voltage(s) based on a radio frequency (RF) voltage(s), which may be harvested from an RF signal(s) received via the MEMS control bus. In this regard, it may be possible to eliminate active components and/or circuits from the passive MEMS switch circuit, thus helping to reduce leakage and power consumption. As a result, it may be possible to provide the passive MEMS switch circuit in a low power apparatus for supporting such applications as the Internet-of-Things (IoT).