Power Combining Techniques for Space-Borne GaN SSPA in Ka-Band

Highly Efficient power combining techniques are mandatory for developing solid state power amplifiers (SSPAs) for high frequency space applications. Indeed, SSPAs are designed starting from medium power components, in the range of few watts, that are combined in such a way that the equipment efficiency is kept as maximum as possible. Planar structures such as branchlines or Wilkinson provide good isolation between ports but their losses become prohibitive when both peak power and frequency are in the range of hundreds of watt and tens of GHz, respectively. In these cases, waveguide structures result to be the most appropriate. On this way, the paper presents the design and experimental characterization of two distinctive structures conceived for spatially combine sixteen 10 W Gallium nitride monolithic microwave integrated circuit for realizing a Ka-band (17.3 GHz-20.2 GHz) SSPA with more than 125 W of saturated output power.