Reconfigurable band pass filter based on DMTL structure

This paper presents the design and optimization of CPW (coplanar waveguide) based tunable band pass filter by using RF MEMS capacitive switches and distributed MEMS transmission line (DMTL). To achieve tunability we have used Twelve MEMS capacitive type switches (six fixed-fixed types and six cantilever type). The center frequency and bandwidth tunability can be achieved by actuating shunt (fixed-fixed) and series (cantilever type) switches respectively. Tunable filter performance is mainly depending on the switches individual performance. Actuation voltage, return loss, insertion loss are the basic performance parameters of any RF MEMS switch. Electromechanical and RF performance analysis of the switches are initially carried out to analyze the performance without integrating with the DMTL structure. The designed shunt and series switches require 15 and 22V respectively to reach the beam 2/3 of the initial gap. Electro-mechanical analysis of the switches is carried out for different conductor materials, dielectric materials, different beam widths, different dielectric thickness values, and different air gap vales. After integration of the switches with DMTL structure to get the optimized filter a detailed electromagnetic analysis of various parameters and materials are done. Simulation results shows that return loss and insertion loss is improved by using this structure. The center frequency of the filter has the variation from 0.2-1 GHz with band pass return loss of -22.5dB. The band width tuning of nearly 0.7 GHz with band pass insertion loss of -3dB is achieved.