A Review of Microwave Vacuum Devices in China: Theory and Device Development Including High-Power Klystrons, Spaceborne TWTs, and Gyro-TWTs

Lately, R&D of microwave vacuum electron devices (MVEDs) has played a very important role in the technologies of broadcasting, communication, radar, remote imaging, electronic countermeasures, materials research, deep space exploration, and wave spectroscopy. In the 1970s, this widespread role could not have been predicted, as the development of vacuum electron devices faced a serious challenge from solid-state electron devices. However, in solid-state electron devices, the electron stream is a conduction (ohmic, collisional) current, whereas in vacuum electron devices, the current is a convection (ballistic, collisionless) current. So the vacuum is perfect for high-power devices needing high-power electron currents, especially because vacuum electron devices are intrinsically superior at handling high power or high power density, giving vacuum electronics research an edge in high power and high frequency [1]-[5].