Multi-Mode and Ultra-Wideband Common-Mode Filter Based on Asymmetric Short-Stub Loaded Resonator

In this paper, a novel ultra-wideband common-mode filter (CMF) has been proposed based on the asymmetric short-stub loaded resonator (ASSLR). This CMF consists of a pair of meandered differential lines, the proposed resonator using ASSLR and the ground plane. By applying ASSLR to the CMF design, multiple resonant modes can be introduced in the single CMF unit-cell under the even-mode operation, and correspondingly generate four CM transmission zeros within 12 GHz. As a result, the simulated results show that the proposed CMF can achieve ultra-wide CM stopband from 2.5 to 11.1 GHz (S cc21 < -10 dB) with 126.5% fractional bandwidth. In addition, with the low insertion loss and flat group delay for differential-mode, the proposed CMF is expected to keep good signal integrity of differential signals.