Design of balanced power divider with wide common-mode suppression band

In this paper, a balanced power divider (PD) is designed and implemented in a three-layer configuration. It consists of two tightly stacked microstrip Wilkinson PDs with a shared ground plane in the middle layer. With both dumbbell-shaped and partially interdigital open-ended slots embedded in the common ground, the designed balanced PD can yield a high common-mode (CM) suppression level over a very wide frequency band without degrading the differential-mode (DM) performance. A close examination of this design reveals that good CM suppression mainly comes from the blocking of the ground-plane current path by the open-ended slots in the ground plane. In addition, the proposed balanced PD also exhibits a very wide CM isolation band. A prototype of the proposed balanced PD is realized. The measured fractional frequency bandwidth for CM suppression is 68% and for CM isolation is 93%.