Miniature Klystron for CubeSats

We report progress on a miniature klystron amplifier for 1U (10×10×10cm) CubeSats with output power of 32 watts at Ka band (35.6 GHz) and saturated gain of 35 dB. Three beam testers have been built for testing the cathode and focusing structure. A narrow band microwave amplifier is currently under construction and will be discussed. CubeSats have become the great enabling technology for space science missions. They allow access to space for as little as $100K. Constellations of CubeSats are envisioned to generate earth surface images via synthetic aperture radar. But a radar with significant power is required at the water window of the atmosphere around 35 GHz. Solid state power amplifiers are inadequate because of their low efficiency and inability to radiate heat from a satellite of such limited surface area. The paper describes several innovations in the construction which were necessary to meet the unprecedented efficiency, size, mass, and cost constraints. Modeling was done to characterize beam parameters, RF cavities, the focusing structure, beam- cavity interactions, couplers-RF windows, the electron gun and collectors.