Passive Wireless Switch Circuit for MEMS Control
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Solution Overview
Problem
Conventional silicon-on-insulator (SOI) switches in wireless devices exhibit higher 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 passive wireless switch circuit that uses a smaller number of voltage circuits to control a larger number of MEMS switches, passively generating constant voltages from RF signals to identify and activate selected MEMS switches, eliminating the need for active components and reducing leakage and power consumption, while minimizing conductive traces and routing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional SOI switches are used in wireless devices, then the device can support multiple applications with dynamic circuit couplings, but the on-resistance and off-capacitance increase leading to degraded RF efficiency and performance
Solution Approach 1:
The patent replaces conventional silicon-on-insulator (SOI) switches with microelectromechanical systems (MEMS) switches. The MEMS switch uses a movable conductive plate that can be positioned to create or break electrical connections, substituting the solid-state switching mechanism of SOI switches with a mechanical micromachined structure. This substitution achieves lower on-resistance and off-capacitance, thereby reducing insertion loss and improving RF efficiency while maintaining the ability to dynamically couple circuits for multiple applications
2Ease of operation
If a larger number of voltage circuits are used to control MEMS switches, then each switch can be independently controlled, but the routing complexity and footprint of the apparatus increase
Solution Approach 1:
The patent merges multiple voltage control signals into a single shared voltage line that distributes control voltage to multiple MEMS switches simultaneously. Instead of providing separate voltage circuits for each switch, the invention uses a common voltage distribution network that can selectively activate different switches based on which RF signal is present on the shared antenna, thereby reducing routing complexity and footprint while maintaining independent control capability
Solution Approach 2:
The single voltage circuit is designed to serve multiple functions by controlling multiple different MEMS switches that protect different RF circuits. The voltage circuit can dynamically switch between controlling different MEMS switches based on the detected RF signal frequency, making the voltage control system universal rather than dedicated to a single switch, thus reducing overall device complexity
3Speed
If active components are used in the voltage circuit to generate control voltages, then the switching response can be faster, but the leakage and power consumption increase
Solution Approach 1:
The voltage circuit uses the RF signal itself as the energy source to generate the control voltage needed to actuate the MEMS switch. The rectifier circuit converts the RF voltage directly into a control voltage without requiring external active components or additional power sources. This self-service approach allows the circuit to operate passively, eliminating continuous power consumption and leakage associated with active components while maintaining sufficient switching response speed through the energy harvested from the RF signal
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 solution reduces unwanted insertion loss, improves RF efficiency, and enhances the performance of wireless devices by effectively controlling multiple MEMS switches with fewer voltage circuits, thus minimizing power consumption and routing complexity.
Implementation Method 1
an antenna configured to absorb a radio frequency (RF) signal and corresponding to an RF voltage
Implementation Method 2
a bulk acoustic wave (BAW) structure coupled to the antenna and configured to resonate at a selected frequency bandwidth to convert the RF voltage to a boosted RF voltage higher than the RF voltage
Implementation Method 3
a rectifier circuit configured to generate a constant voltage based on the boosted RF voltage
Implementation Method 4
A microelectromechanical systems (MEMS) switch configured to be closed in response to receive a constant voltage exceeding a threshold voltage
Data Source
AI summary
A passive wireless switch circuit and related apparatus are provided. In examples discussed herein, an apparatus includes a smaller number of voltage circuits configured to control a larger number of microelectromechanical systems (MEMS) switches. The voltage circuits passively generate a number of constant voltages based on a number of radio frequency (RF) signals to collectively identify each of the MEMS switches. A decoder circuit decodes the constant voltages to identify a selected MEMS switch and provides a selected constant voltage higher than a defined threshold voltage to close the selected MEMS switch. As such, it may be possible to eliminate active components and/or circuits from the passive wireless switch circuit, thus helping to reduce leakage and power consumption. It may be further possible to reduce conductive traces between the voltage circuits and the MEMS switches, thus helping to reduce routing complexity and footprint of the apparatus.