RF MEMS Switch And The Application Research In Phase Shifter

Radio Frequency Micro-Electro-Mechanical System(RF MEMS) has more and more attention in the field of modern communication. Thanks to their own characteristics, RF MEMS can avoid some serious disadvantage which usuraly appears in PIN and MOSFET switches. Also it can match to high-intensive system, with some advantage including low power, good RF characteristics, easy integration and so on. So it is important to research RF MEMS switches and their application.First the paper briefly introduces the development of RF MEMS switch and MEMS phase shiffter at home and abroad. Then compares some usural driving mechanism such as electrostatic, electromagnetic, electrothermal, piezoelectric and shape memory metal(SMA) switches. It sets up switch mechanical models and electromagnetic models with ohmic contact and capacitive coupling RF MEMS switches. It includes the flexibility coefficient, voltage drop, ohmic and impedance which are all applicable to canltilever and clamped beam switches. By optimizing switch model, it optimizes switch design, and stuctures a quasi-four-bit distributed MEMS transmission line(DMTL) phase shiftter with the MEMS capacitive switches which have been designed above. The DMTL phase shiftter adapts to 40G hertz band and the voltage drop of the RF MEMS switches is about 20 volts. Phase shiftter is by the composition of fifteen switches which are distributed periodically on the coplanar waveguide, and can achieve 23.95 degrees phase step. The unit length of this phase shiffter is 144 microns, with high resistance silicon substrate and silicon nitride dielectric layer. There is a 0.8 microns thickness oxide on the face of substrate. It simulates the mechanical deformation of the RF MEMS swich by ANSYS soft, simulates the S coefficient by HFSS soft. The simulation results can completely validate the rationality of the phase shiffter.