Design of various Coplanar Waveguide RF MEMS Phase Shifters

Abstract

This paper presents the modeling and analysis of Radio Frequency (RF) Microelectromechanical System (MEMS) phase shifter using various structures of transmission lines. The proposed phase shifter designs consists of various structures of coplanar waveguide (CPW) loaded with MEMS switches. The loading of MEMS switches contributes a phase change which had been proven effective for the design of phase shifter with low loss, low parasitic and high linearity. The shunt switch’s capacitance is varied by applying an analog bias voltage across the center conductor of the CPW line and MEMS bridge, which in turn varies the characteristic impedance of the transmission line, producing the phase shift. Periodic loading of transmission line with MEMS bridges produces increased phase change, resulting in more phase shift compared with the non-biased condition. The results presents a comparison between RF MEMS phase shifter design with a conventional phase shifter with new structures of CPW lines, with increased per unit length phase shift. The proposed phase shifter design can operate up to 15GHz with a measured return loss below −12 dB and with a loss less than 1dB/phase shift at 10 GHz.