Modified parallel-coupled filter with two independently controllable upper stopband transmission zeros

Abstract

A microstrip cross-coupled filter with two independently controllable transmission zeros on upper stopband is presented. The initial filter structure is a conventional Chebyshev-response parallel-coupled filter that can be easily realized by the analytical method. The newly proposed coupling/shielding lines can effectively control the cross and main couplings without changing the original filter layout. This approach allows a designer to eliminate the tedious segmentation method, which is usually used to establish the relation between the coupling coefficient and physical distance between resonators. A three-order filter is designed and fabricated for demonstration.