An RF-MEMS Switch With Low-Actuation Voltage and High Reliability

We report a novel radio-frequency (RF) microelectromechanical systems switch with low-actuation voltage and long lifetime by adopting a design approach in which a freely moving contact pad structure opens and closes the switch through electrostatic actuation. Unlike electrostatically actuated suspended beam or bridge contact pad structures, the freely moving contact pad can be reliably operated at a low-actuation voltage of 4.5 V because actuation energy is not used in elastic deformation of a suspension. At a frequency of 50 GHz, an insertion loss of 0.5 dB and an isolation of 55 dB were obtained from the switch. Measured delay times for switch-on and switch-off were 120 and 130 ns, respectively. After 200 billion cyclic actuations with signal RF power of 0 dBm by cold switching, actuation voltages remained the same; insertion loss and isolation were maintained below 0.59 and 54 dB, respectively; and delay times for switch-on and switch-off have no change at 50 GHz. However, when the switch slants to any direction over 28°, the actuation voltage increases over 5 V because movement of the movable lower contact pad is obstructed by friction between the movable contact pad and the guard poles.