Design and Experimental Validation of a Compact Eight-Way Radial Coaxial Power Combiner for K/Ka-Band Applications

This paper presents the design, fabrication, and experimental validation of a compact eight-way radial coaxial power combiner operating in the K/Ka-band. The proposed architecture employs a radial coaxial topology with eight peripheral ports and a central oversized coaxial feeder, combined with a tapered impedance-matching core specifically designed to compensate for the intrinsic impedance variation associated with radial coaxial propagation. This approach enables broadband operation and uniform power distribution in a compact and manufacturable structure. The electromagnetic performance of the combiner has been optimized through full-wave simulations and validated by experimental measurements. The fabricated prototype shows operation over the 22 to 32 GHz frequency range, with an input return loss better than −10 dB over most of the band, with some degradation in the mid-band region, and values below −20 dB near the band edges. When operating as a power divider, the measured insertion loss per output port is approximately −12 dB, confirming effective power splitting and good amplitude balance among the eight ports. The good agreement between simulated and measured results confirms the validity of the proposed combiner architecture. Owing to its compactness, broadband behavior, and compatibility with standard coaxial interfaces, the proposed combiner represents a promising solution for high-performance solid-state power amplifier systems in spaceborne and millimeter-wave communication applications. In addition, the absence of dielectric loading and the use of an oversized coaxial geometry suggest a high power-handling capability, comparable to that of other coaxial spatial combiners reported in the literature.