Development of an Unbalanced-to-Balanced Filtering Power Divider With Sequential Rotation Phase Characteristic

This letter presents a new development of an unbalanced-to-balanced filtering power divider (FPD) with sequential rotation phase states of 0^∘, 90^∘, 180^∘ , and 270^∘ at four output ports. To satisfy the phase requirement at output ports, a fresh insight of 90 ∘ phase-shifting characteristic is brought from the perspective of electric field distributions on the open-and short-circuited transmission line (TL) models. Building upon this phase-shifting concept, an unbalanced-to-balanced FPD for application in sequential rotation feeding network is presented, which obviously distinguishes from the conventional method of cascading multiple discrete devices. To verify the proposed concept, a design example is excogitated and measured. The results show that the aforementioned phase states with equal amplitude are successfully achieved at four output ports. Meanwhile, the developed FPD also exhibits phase bandwidth of 37% and impedance bandwidth of 8.5%, regarding the criterion of better than 15-dB return loss.