Proposal of Quasi-Lumped Coplanar Stripline Resonators for Balanced Filter With Intrinsic Common-Mode Rejection

In this paper, a class of coplanar stripline (CPS) resonators with inherent capacitance and inductance is proposed. Its unified equivalent circuit is investigated to characterize the quasi-lumped resonators. Several variants of the proposed CPS counterparts are further presented to enlarge the capacitance and inductance, so that the desired resonance could be reached at a lower frequency step by step. Afterwards, the LC equivalent circuit and transmission-line (TL) model are derived to design a second-order differential-mode (DM) bandpass filter while the common-mode (CM) rejection is intrinsically obtained by virtue of the balanced CPS structure. Finally, the proposed balanced filter is simulated, fabricated and measured to validate the utility of the desired resonance and intrinsic CM suppression.