Novel balanced filters with high common-mode suppression using slotline structure

In this paper, a number of novel balanced filters for various applications are presented with intrinsic high common-mode(CM) suppression using slotline structure. Boundary conditions under differential-mode(DM) and CM signals are briefly discussed in order to explain the DM transmission and CM suppression in the microstrip-to-slotline(MS) conversion. Then several balanced filters are proposed aiming at various applications such as wideband, ultra-wideband and narrowband fields. Results of all these works show high CM rejection, indicating the advantage of slotline structure that the CM stopband is no need to be considered any more while the DM passband could be designed independently.