Design and Analysis of Distributed MEMS Transmission Line (DMTL) based Tunable Band Pass Filter

Abstract

In this paper, we have designed a Distributed MEMS Transmission line (DMTL) based Tunable Band Pass Filter. DMTL is a coplanar waveguide (CPW) periodically loaded with continuously-variable MEMS capacitors. We have proposed two types of switches i.e. fixed-fixed type and cantilever type which are designed by FEM Tool. We have optimized the RF MEMS Switches and each switch is simulated. Fixed-fixed switch has the Spring constant of 26.73 N/m, pull-in voltage of 15V, switching time of. 38ns, up and down state capacitances of 0.142 pf,4.05 pF, return losses is in the range of -.005 to −.035dB, and insertion losses is in the range of −11 to −24dB. Series cantilever switch has the spring constant of 6.42 N/m, pull-in voltage of 26V, switching time of 110μs, up and down state capacitances of. 02 fF,.24 pF, return losses is in the range of −.007 to −.011dB, and insertion losses in the range of −5 to −70dB. The electromagnetic simulation of the filter has been carried out with the help of HFSS without switch, the center frequency is obtained at 1GHz, and an insertion loss of nearly −5dB. When these switches are integrating with CPW transmission line to get tuning of both the center frequency and bandwidth, the filter operates at the UHF and L band (frequency range of. 1-3GHz). Within the tuning range the filter has the insertion loss of less than 5dB which is always required.