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

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