Research Of MEMS Phase Shifter Based On Left-handed Metamaterials Transmission Lines

Recently, tunable left-handed metamaterials (LHM) microwave devices basedon MEMS technology becomes one of the popular issues in microwave field.Because of its special electromagnetic properties, LHM have been widely applied inthe design of new microwave devices. RF MEMS switches have the advantages oflow loss, low power and good linearity in high frequency. They are ideal switcheswhich can be used to design phase shifters with high performance.Firstly, this paper describes the working principle of resonant type andtransmission line-type LHM. Acorrding to the transmission line theory and theeffective medium theory, equivalent circuits of unit LHM are proposed. By applyingNicolson-Ross-Weir method, this paper deduces the relational expression aboutextracting effective permittivity and effective permeability. After that, fundamentalequations of loaded line phase shifters’ working principle are introduced. Then, theequivalent circuit of MEMS phase shifters based on LHM is established. Thesestudies offer theory basis for the design and optimization of2-bit phase shifters.Secondly, this paper sets up the mechanical model and circuit model of RFMEMS shunt switch and discusses how switch parameters affecting the workperformance. Based on this theory, the statics and transient dynamics simulation ofRF MEMS shunt switch are carried on by using ANYSY software. Also, theinfluences of switch dynamic performance resulted from the length of bridge, metalmaterials and coefficient of elasticity are dicussed.Finally, full-wave simulation of resonant type and transmission line-type LHMare done by using Ansoft HFSS softwave. By means of extracting effectivepermittivity and effective permeability, the proposed LHM transmission lines areproved to have left-handed properties. Since transmission line-type LHM have lowerloss and wider bandwidth than resonant type LHM, the2-bit phase shifter isachieved by properly addinig RF MEMS switches on transmission line-type LHM.Simulation results show that at24GHz, the four phase statuses are0o、90.1o、180.4oand277.4o, respectively. Moreover, the insertion loss is better than-2.6dB and thereturn loss is lower than-10.6dB in the frequency band of23GHz～27GHz.