A General Method for Balanced-to-Unbalanced Filtering Out-of-Phase Power Divider Design

In this paper, a new method to develop balancedto-unbalanced (BTU) filtering out-of-phase power divider (PD) is presented. Based on the comparison between BTU filtering out-of-phase PD and balanced-to-balanced (BTB) filter, it is found that the BTU filtering out-of-phase PD can be constructed by combining a BTB filter and an additional parallel four-port network. The design equations are derived and corresponding circuit models are given. Finally, a prototype is designed to verify the theoretical prediction. The design procedure and parameter selection are detailed. The good performance and the consistency between the simulated and measured results verify the design theory.