40-W CW broad-band spatial power combiner using dense finline arrays

This paper presents a broad-band spatial power-combining system based on ta pered-slot antenna arrays integrated in a standard WR-90 waveguide environm ent. The system is designed using a modular tray architecture, providing fu ll waveguide-band frequency coverage and an excellent thermal environment f or a set of monolithic-micro wave integrated-circuit (MMIC) amplifiers. The shape of the tapered-slot or finline structures was optimized to minimize return loss and provide a broad-band impedance transformation from the wave guide mode to the MMIC amplifiers. A prototype eight-element array using co mmercial GaAs MMIC power amplifiers yielded a maximum of 41-W output power (continuous wave) with a gain variation less than +/-1.2 dB within the enti re band of interest, The average combining efficiency over the operating ba nd was estimated at 73%, The results suggest the efficacy of the design and a strong potential for higher powers by moving toward a greater number of MMIC's per tray and a larger number of trays, Should the 100-W system be re alized in the near future, our combiner system will become a promising cand idate to challenge the dominant position currently claimed by the traveling -wave tube amplifiers.