Reconfigurable Balanced Dualband Bandstop Filter

This paper introduces a novel architecture of reconfigurable balanced (differential) dualband bandstop filter (BSF). In differential mode (DM), each symmetrical bisection of the filter incorporates in-series cascade of two tunable dualband bandstop sections whereas high CMRR is achieved by loading open stubs to the symmetry plane of the branch line structure. To validate the proposed topology, a microstrip prototype is designed and fabricated. Both simulation and measured results show a good agreement with each other.