Dual-Band Differential Filter Using Broadband Common-Mode Rejection Artificial Transmission Line

A new balanced dual-band bandpass fllter with strong common-mode rejection is presented in this paper. Common-mode rejection is provided by a section of a periodic microstrip difierential line that behaves as a low-pass fllter under common-mode operation. In contrast, the difierential line exhibits very good all-pass behavior under difierential mode operation. This structure is combined with a difierential dual-band bandpass fllter based on embedded resonators. Simulations and experiments conflrm that the combined structure has good common-mode rejection within the passbands of the dual-band difierential fllter.