MEMS Switch Puts SoC Radios On The Cusp

June 9, 2003
This MEMS switch technology for multiband/multimode RF systems heralds the anticipated system-on-a-chip radio.

Slowly, microelectromechanical systems (MEMS) devices have found homes, mostly in optical switching and processing. STMicroelectronics has now stretched their reach by demonstrating an RF MEMS switch for use as a band and circuit reconfiguration switch in multiband/multimode RF systems.

The device also has potential as a transmit/receive (Tx/Rx) switch in cell phones and other radios. Today, most Tx/Rx switches are separate devices made with gallium-arsenide MESFETs or PIN diodes. STM's MEMS version can be fully integrated into the silicon RF chip, drawing closer to a system-on-a-chip (SoC) radio while lowering costs.

Benefits derived include superior insertion loss and isolation figures. STM's switch measured an insertion loss of only 0.18 dB with an isolation factor of -57 dB at 2 GHz on a 15-Ù-cm substrate. Other vital benefits include 3 W of continuous RF power handling and superior linearity. A two-tone test showed the intermodulation products to be 82 dB below the tone levels at 2.4 GHz.

The STM switch uses an unusual combination of thermal and electrostatic actuation. It consists of a floating 400- by 50- by 1-µm nitride beam with two contacts designed to provide a metal-to-metal bridge between two conductors of a 50-Ù line. At each end of the beam is a small resistive heating element. When 20 mA is applied to the elements, they produce a temperature that causes the beam to bend and ultimately make the interconnection. The bimorph effect produces bending because of different thermal expansion coefficients of two materials in the structure. Actuation time is about 200 µs.

To hold the switch contacts in place, the heating current is removed and a static field is set up by dc voltage applied between a capacitor element within the beam and the circuit ground plane. Removing the voltage causes the contacts to separate within about 30 µs.

As developments unfold in this technology, particularly in switching time, the switch will suit an even wider range of RF applications.

See associated figure

STMicroelectronicswww.st.com

Sponsored Recommendations

Board-Mount DC/DC Converters in Medical Applications

March 27, 2024
AC/DC or board-mount DC/DC converters provide power for medical devices. This article explains why isolation might be needed and which safety standards apply.

Use Rugged Multiband Antennas to Solve the Mobile Connectivity Challenge

March 27, 2024
Selecting and using antennas for mobile applications requires attention to electrical, mechanical, and environmental characteristics: TE modules can help.

Out-of-the-box Cellular and Wi-Fi connectivity with AWS IoT ExpressLink

March 27, 2024
This demo shows how to enroll LTE-M and Wi-Fi evaluation boards with AWS IoT Core, set up a Connected Health Solution as well as AWS AT commands and AWS IoT ExpressLink security...

How to Quickly Leverage Bluetooth AoA and AoD for Indoor Logistics Tracking

March 27, 2024
Real-time asset tracking is an important aspect of Industry 4.0. Various technologies are available for deploying Real-Time Location.

Comments

To join the conversation, and become an exclusive member of Electronic Design, create an account today!