Microelectromechanical-systems (MEMS) technology has been commonly applied to RF components with moving parts, such as single-pole, double-throw (SPDT) switches, varactors, and inductors. Until now, low-voltage-actuated MEMS devices have been rare. With the introduction of the DKM812-3 RF switch from Dow-Key Microwave Corp. (Ventura, CA), however, 3 V is all that is needed to control this commercial MEMS reflective SPDT switch. With sufficiently low power consumption for portable applications, the SPDT MEMS switch is well suited for use through 6 GHz.
The MEMS SPDT switch consists of a moving part (a cantilever) that is shifted to different positions by a magnetic field. The magnetic field is manipulated by the applied control voltage. The technology has been in existence since the 1970s in the forms of temperature and pressure sensors, with accelerated development taking place in the 1990s thanks to funding from the Defense Advanced Research Projects Agency (DARPA). Since MEMS technology offers potential for tiny switches and other microwave components through about 50 GHz, both commercial and military developers have pushed the technology toward RF and optical applications.
The DKM812-3 RF switch (see figure) improves in efficiency and versatility over the company's earlier MEMS single-pole, single-throw switch (see Microwaves & RF, November 2001, p. 104). It can be used in a variety of applications, including automatic test equipment (ATE), wireless local-area networks (WLANs), Global Positioning System (GPS) receivers (Rxs), wireless handsets, and smart antennas. It features low insertion loss of typically 0.15 dB or less at 1 GHz and typically 0.3 dB or less at 6 GHz. The isolation is 30 dB at 1 GHz and more than 20 dB at 6 GHz, and the return loss is 14 dB or better from 100 kHz to 6 GHz. The tiny switch consumes less than 3 mW power.
The reflective RF switch handles average RF power of 2 W and as much as 3 W power on peaks. The device has been found to perform without compression at input power levels to +37 dBm at 2.4 GHz. The switch has an input third-order intercept point of +65 dBm minimum.
Although this device is specified for 10 million cycles, similar MEMS devices have been found to provide well over 100 million operations without degradation in performance. The MEMS switch, which is rated for operating temperatures of −40 to +85°C, is housed in a JEDEC MO-220 package that measures 7 × 7 × 1.5 mm. Dow-Key Microwave Corp., 4822 McGrath St., Ventura, CA 93003-7718; (805) 650-0260, FAX: (805) 650-1734, Internet: www.dowkey.com.