All Solid-State Transmitter (ASTRAM) for Next-Generation Ground-Based Planetary Radar

This paper presents the development of a newtype of transmitter for next-generation ground-basedplanetary radar. The transmitter is based on mature,reliable solid-state technology, and provides analternative to traditional amplifier tube-basedtransmitter systems. The technology described is ascalable transmitter system that utilizes a low-lossmethod of power combining the RF outputs of multipleGallium Nitride (GaN)-based Monolithic MicrowaveIntegrated Circuits (MMICs) in parallel to achieve acoherent amplified output signal. The power combiningtakes place within modular devices that we refer to asspatial power combining amplifiers (SPCAs). The SPCAdiscussed in this paper combines an arrangement ofsixteen 85 W MMIC amplifiers to produce ~1.3 kWcontinuous-wave power at a center frequency of8.56 GHz. The modular nature of the SPCA units allowsthem to be further combined hierarchically viawaveguide-combining techniques to form scalable highpowertransmitter systems. This paper presents the basicarchitecture and full laboratory characterization of an Xbandsolid-state SPCA unit, including key deviceperformance results, reliability analysis, andenvironmental sensitivities.