rf phase shifter using mems switches on a tapered coplanar waveguide

This paper presents the analysis and design of tapered coplanar waveguide based RF phase shifter using MEMSswitches for microwave and millimeter-wave applications. The equivalent circuit of the phase shifter has been analyzed withthe capacitances of MEMS switches in both up and down states. A control voltage applied between the center conductorand the switch’s membrane actuates it and pulls down the membrane, creating a slow-wave transmission line. The loadingcapacitance gets added up with the line capacitance, thus varying the characteristic impedance of the line. This change inimpedance varies the phase velocity, thereby producing a phase shift. The use of tapered coplanar waveguide as an alternative to the conventional waveguide produces an increase in phase shift per unit length with a small increase in insertion loss.By accurate design of the taper sections, the losses can be reduced further.