Ka-Band Wideband-Gap Solid-State Power Amplifier: General Architecture Considerations

Motivated by recent advances in wideband-gap (WBG) gallium nitride (GaN) semiconductor technology, there is considerable interest in developing efficient solidstate power amplifiers (SSPAs) as an alternative to the traveling-wave tube amplifier (TWTA) for space applications. This article documents the general architecture considerations pertinent to developing SSPA architectures that can enable a 120-W, 40 percent power-added efficiency (PAE) SSPA at 31 to 36 GHz. This article develops an estimated loss budget for the common elements of these SSPA architectures. It then considers the bandwidth effects of the monolithic microwave integrated circuits (MMICs) and various combiners/dividers used that influence the performance of the SSPA architecture. Finally consideration is given to possible MMIC power levels, efficiencies, and gain. Using these factors, this article develops MMIC and power-combiner requirements for an SSPA architecture to reach the goal of 120 W with a 40 percent PAE.