X-band compact coaxial power combiner for high-power applications

A four-way power combiner with small cross-sectional size and high power capacity is investigated in this study. The design is based on the cascaded structure of three rectangular hybrid rings and one coaxial-to-waveguide transition. The combiner consists of coaxial and waveguide structures to ensure high power capacity. The compact cross-sectional size (0.71 lambda x 0.74 lambda at the centre frequency) is achieved by employing transverse electric magnetic (TEM)-mode coaxial line structures. A prototype power combiner is fabricated and tested to verify the design results. It has been demonstrated that the proposed power combiner has a power capacity of 16 kW. The return loss is better than 25 dB, isolation degree higher than 27 dB, and amplitude imbalance within 0.16 dB limits in the operating band 8-9 GHz, validated with both simulations and experiments. The proposed structure is suitable for kW-level power combining and it can also be implemented in planar forms for a wider range of applications.