Design of 3-Bit Digital DMTL Phase Shifter for C- to Ku-Band Applications

Microelectromechanical (MEMS) technology is an important platform where we can design systems which can perform at RF and millimeter wave frequencies. Such systems include the MEMS phase shifters. This paper presents the design and simulation of a 3-bit Digital Phase-Shifter based on the Distributed MEMS transmission Line (DMTL) technique, constituted with 28 capacitive shunt switches. The design is optimized to work between C-to Ku-band of frequencies but the best results are obtained at 15GHz frequency which is useful for wireless communications in Ka band. The MEMS phase shifters generally have low insertion loss, high isolation and uses low power which can further be added up to construct low cost and light weight phased array antennas. The DMTL phase shifters are designed with a CPW line loaded with capacitive shunt switches for easier access to the ground. The capacitive shunt switches are highly reliable and capable of handling high amount of RF power. The change in the phase velocity of the signal travelling through CPW line is achieved by pulling down the MEMS switches by the application of DC control voltage on the central conductor line. The digital phase shifter consists of three bits designed to obtain 45o, 90o and 180o phase shift. The spacing between the switches is 250μm. The insertion loss is calculated at -0.73dB.