A Novel Patterned Ground Structure With Shunt and Series Lumped Elements for Synthesizing Absorption Common-Mode Filters

To synthesize an absorption common-mode filter (A-CMF) in a two-layer printed circuit board, patterned ground structures (PGSs) have been studied in the past few years. A conventional PGS consists of slotlines and shunt lumped elements across slots. On the contrary, the proposed new PGS uses both shunt and series lumped elements (SSLEs) in a ground plane with a closed-loop asymmetrical coplanar strip. To validate the proposed SSLE PGS, two circuits of bidirectional A-CMFs are developed to absorb common-mode (CM) noise in the 2.4 GHz industrial scientific medical (ISM) band. The one with higher CM noise absorption bandwidth is finally implemented and demonstrated in this article. Besides, nonideal CM return current paths are considered to modify the ideal circuit and reduce the discrepancies between the full-wave and circuit simulations. The measurement results show that the proposed bidirectional A-CMF attains CM noise absorption from 2.29–2.57 GHz for electromagnetic interference suppression in the 2.4 GHz ISM band. Most of all, the proposed work reveals a notable differential-mode −3 dB bandwidth up to 16.3 GHz with an ultracompact size of 0.0143
$\lambda _g^2$
.