Ka-band distributed microelectromechanical systems transmission line phase shifter using metal air metal switch

A new approach for designing a two-state unit cell for a six-bit distributed coplanar waveguide microelectromechanical systems (MEMS) phase shifter is proposed in this study. The proposed structure includes metal air metal (MAM) capacitors as switches and consists of a unit cell with one MEMS and two MAM switches to produce two phase shifts per unit cell. In the first state, the MAM switches are pulled down and a 5.625 degrees phase shift is achieved, and in the second state, the MEMS switch is actuated to yield a phase shift of 11.25 degrees. The designed structure is modeled using equivalent transmission line circuit model and simulated in the Ka-band at 34 GHz, employing advanced design system (ADS), ANSOFT HFSS and COMSOL software. Based on the modeling and simulation results, the root-mean-square (RMS) phase error is 1.4 degrees, and maximum return loss and minimum insertion loss for all 64 states are better than -10.1 and -1.45 dB, respectively. The main advantages of the designed structure are its small size, low loss, low phase error and a simple phase shift mechanism. A fabrication process is also proposed for the distributed MEMS transmission line (DMTL) phase shifter that shows the feasibility of the proposed design. The proposed structure can be easily scaled to other bands and used in applications with more bits as complex as phased array antennas.