Theoretical Circuit Analysis of Bidirectional Dual-band Absorptive Common-Mode Filter

This paper presents a bidirectional dual-band absorptive common-mode filter for I/O connectors in duplex communication systems. Based on a previously proposed bidirectional single-band common-mode filter architecture, we extend it to achieve dual-band functionality through circuit analysis. The filter features dual-band matching and feedback networks designed to target WiFi frequencies at 2.4 GHz and 5.5 GHz, enabling suppression and absorption of common-mode signals at both frequency bands. Finally, commercial simulation software is utilized to verify the proposed equivalent circuit architecture, confirming its differential-mode and common-mode operational bandwidth characteristics.