THE BEGINNING OF RF MEMSMicroelectromechanical Systems (MEMS) have been developed since the 1970s for pressure and temperature sensors, accelerometers, gas chromatographs, and other sensor devices. MEMS switches for low-frequency applications have also been demonstrated in the early 1980s but remained a laboratory curiosity for a long time. They are essentially miniature devices that use a mechanical movement to achieve a short circuit or an open circuit in a transmission line. But in 1990But in -1991, under the support of DARPA (Defense Advanced Research Projects Agency), Dr. Larry Larson at the Hughes Research Labs in Malibu, California, developed the first MEMS switch (and varactor) that was specifically designed for microwave applications [1]. However, and as usual with any leap in technology, it was far from mature and had poor yield and virtually no reliability. Still, it demonstrated excellent performance up to 50 GHz, far better than anything that could be achieved with GaAs devices.The initial results of Larson were so outstanding that they stirred the interest of several groups in the U.S. government; and by 1995, Rockwell Science Center and Texas Instruments both had developed an outstanding RF MEMS switch. The Rockwell switch was a metal-to-metal contact type, suitable for DC-60 GHz applications, while the Texas Instruments switch was a capacitive contact switch, suitable for 10-120 GHz applications. The rest is history; by 1998, the University of Michigan, The University of California, Berkeley, Northeastern University, MIT Lincoln Labs, Columbia University, Analog Devices, Northrup Grumman, and several other companies were actively pursuing RF MEMS devices. By 2001, there were more than 30 companies work-