An Isolated Three-Way Power Combiner via Magnetically Coupled Microstrip Ring Probes

This research presents a Ka-band isolated threeway power combiner using a six-port E-plane waveguide coupler (SEWC) and a magnetically coupled transition from the waveguide to the microstrip line. To achieve phase coherency, magnetic ring probes with different rotation directions are designed. The experimental results indicate an amplitude imbalance within the range of +/- 0.8 dB at frequencies between 30 and 40 GHz. The isolation exceeds 22 dB, and all return losses are better than 16.2 dB. When three GaN power amplifiers with output power ranging from 8 to 10 W are integrated, the active combiner generates radio frequency (RF) power up to 25.8 W within the 30 to 40 GHz band. This translates to an average combining efficiency of 88.6% and a power-added efficiency exceeding 14.7%.