Broadband Absorptive Common-Mode Filter Based on H-Shaped Defect Ground Structure

A broadband absorptive common-mode (CM) filter based on an H-shaped defect ground structure (DGS) is proposed in this paper. The filter suppresses CM noise by periodically etching H-shaped defect structures with different sizes along the return path of the differential lines, while maintaining the integrity of the differential signal. It achieves a CM suppression over 20 dB within the frequency range of 1.83 GHz to 6.38 GHz. Further, the filter achieves absorption by embedding a resistor in the etched structure to dissipate reflected noise. By operating within the frequency ranges of 2.06 GHz to 3.14 GHz and 4.83 GHz to 6.88 GHz, the CM noise absorption efficiency can surpass 90%, effectively eradicating CM noise in the Wi-Fi frequency bands of 2.4 GHz and 5 GHz. The size of the filter is approximately 0.17λ
g
×0.41λ
g
.