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This paper presents the analysis and design of tapered coplanar waveguide based RF phase shifter using MEMS switches for microwave and millimeter-wave applications. The equivalent circuit of the phase shifter has been analyzed with the capacitances of MEMS switches in both up and down states. A control voltage applied between the center conductor and the switch's membrane actuates it and pulls down the membrane, creating a slow-wave transmission line. The loading capacitance gets added up with the line capacitance, thus varying the characteristic impedance of the line. This change in impedance 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. [ABSTRACT FROM AUTHOR]