Single-Pole Eight-Throw RF MEMS Rotary Switch

Abstract

The design, fabrication, and measured performance of a novel single-pole eight-throw radio-frequency (RF) microelectromechanical systems (MEMS) rotary switch are described. The concept of this rotary switch is based on the adaptation of the axial gap wobble motor. A prototype switch has been made using separately fabricated stator, rotor, and cap components that are then assembled. A rigorous procedure was setup to investigate the direct current (dc) contact resistance over a total of four million rotor contact closures, with half a million closures made on each of the eight stator contacts. It was found that there was no obvious systematic trend in contact resistance over time. An average contact resistance of 2.5 Omega was recorded; however, values as low as 1.0 Omega were also found. The assembled rotary switch demonstrated an excellent RF performance. With the inclusion of feed lines, the insertion loss was 2.65 dB at 20 GHz, after renormalizing the measurement reference impedance. When the loss of the feed lines is subtracted, the worst-case on-state intrinsic insertion loss of the rotary switch is only 2.16 dB at 20 GHz. A worst-case off-state isolation of 31 dB was also measured over the 20-GHz bandwidth. The effective performance figure-of-merit for this switch in an arbitrary position was calculated to be 10.7 THz. To the authors' knowledge, this is the first example of a true single-pole multiple-throw RF MEMS rotary switch