Tunable In-Phase Power Divider for 5G Cellular Networks

A tunable power divider that operates in the 28-GHz band for future 5G mobile systems is presented. The proposed power divider can be used in the feeding network of the antenna array of a cellular network for a beamforming purpose. The proposed design is a modification of the traditional Wilkinson power divider and has the ability to change the output power division ratio continuously. To realize that, two varactor-loaded L-shaped open-ended stubs are connected to the two branch lines of the device to ensure the flatness of the power division. Moreover, two asymmetrical coupled lines are adopted in the output ports and a stepped-impedance transformer is added at the input port to enhance their matching across different power divisions and wide frequency range. A prototype is developed and tested. A tuning power ratio range from 1: 1 to 1: 2.3 across the band (27- 29 GHz) is achieved. The return losses are more than 13 dB, while the isolation is more than 10 dB across that band. In addition, the simulated and measured amplitude and phase imbalances are less than 0.2 and 0.5 dB, and 5 degrees and 12 degrees, respectively, from the ideal values.