Synthesis of Bandstop Filters With Ultra Wide Upper Passbands

A new LP prototype-to-distributed bandstop mapping is defined to synthesize BSF´s with controllable upper pass bandwidths. The synthesized filters involve resonators made up of commensurate OC and SC stubs coupled by inverters. It is shown that when inverters are approximated by several unit elements (UE) then their contribution to the response increases appreciably upon optimization. Thus, a novel approach is developed which can be used to synthesize BSF´s with contributing UE´s having ultra wide upper pass bands. Examples are presented with stopband centered at 1 GHz and having upper passband extending to 18 GHz.