Since the dawn of electronic warfare, RF engineers have relied on the vacuum tube — specifically the traveling wave tube amplifier (TWTA) — to produce high microwave frequencies of up to 100 GHz and very high power levels over a broad bandwidth. While solid-state amplifiers are smaller and lighter than TWT amplifiers, even the most impressive gallium nitride (GaN), silicon LDMOS, or GaAs RF power transistors produce at most just over 1 kW of RF power, and then only at comparatively low frequencies.
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