The Squarax Amplifier: An Electromagnetic and Thermo-mechanical Innovation

This paper describes a novel broad band Spatial Power Combiner (SPC) Amplifier based on Square Coaxial (Squarax) Transmission Line (TL), able to tolerate the Thermo-Mechanical effects due to the transistor heating. In the proposed SPC, Fin Line to microstrip transitions (FLuS) are inserted into the Squarax TL, in order to connect many Monolithic Mi- crowave Integrated Circuit (MMIC) Solid State Power Ampli¯er (SSPA) while maintaining an easy integration. The proposed structure has some advantages over the traditional SPC's. The Squarax SPC geometry allows the feeding of a higher number of MMIC than in a Waveguide SPC, and its straight pro¯le allows to connect simple and low-cost square or rectangular heat-sink devices with high thermal dissipation attitude. Conversely, coaxial SPC needs apposite circular heat-sinkers that requires expensive custom production. Squarax structure ensures high power outputs and small sizes, together with theoretical DC frequency cut-o®. In this work, a 16 cards Squarax SPC in the operative bandwidth 4{18 GHz has been designed, able to account for 32 MMIC SSPA's. The design Electromagnetic and Thermo-structural simulation of the proposed device are shown.