Balanced-to-Balanced and Balanced-to-Unbalanced Power Dividers With Ultra-Wideband Common-Mode Rejection and Absorption Based on Mode-Conversion Approach

In this paper, for the first time, a balanced-to-balanced (B-B) power divider (PD) and a balanced-to-unbalanced (B-UB) PD with ultra-wideband common-mode (CM) rejection and absorption characteristics are introduced based on a new design approach. The design of B-B and B-UB PD structures is using one core circuit to provide power dividing/combining and differential-mode-to-common-mode (DM-CM) converters to realize mode conversion at the balanced ports. With the use of the DM-CM converter, the boundary condition on the symmetric plane of the core circuit is then reversed. Specifically, a perfect-electric wall will be formed along the symmetric plane of the core circuit under the CM operation, with a perfect-magnetic wall under the DM operation. Based on this characteristic, the proposed B-B and B-UB PDs can then achieve wideband CM suppression and absorption with some proper designs. The measured results show that the transmission coefficients of CM operation for the proposed B-B and B-UB PDs are all less than -15 dB with a fractional bandwidth about 200%. In addition, the measured CM absorption rate is higher than 85% with a fractional bandwidth about 71.2% and 116% for the proposed B-B and B-UB PDs, respectively.