Songklanakarin Journal of Science and Technology (SJST) (Dec 2012)

RF phase shifter using MEMS switches on a tapered coplanar waveguide

  • Nataraj Boothalingam,
  • Porkumaran Karantharaj

Journal volume & issue
Vol. 34, no. 6
pp. 645 – 651

Abstract

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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.

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