A broad-band transmission line spatial power combiner (SPC) is proposed in this paper, which uses a square coaxial (Squarax) transmission line (TL). This structure has some advantages over the traditional circular coaxial spatial power combiner, which have been described in this paper. Fin-Line to microstrip transitions are inserted into the Squarax TL, in order to allow an easy integration of Monolithic Microwave Integrated Circuit (MMIC) Solid State Power Amplifier (SSPA). The Squarax SPC geometry allows the feeding of a higher number of MMIC than in a Waveguide SPC, so that this structure ensures high power outputs and small sizes, together with theoretical DC frequency cut-off. In this work, the design and simulation of a passive 4-18 GHz Squarax SPC are reported.
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