Simulation Investigation of Backward Wave Oscillation of Millimeter-wave TWT
毫米波行波管返波振荡的仿真研究

HFSS is used to simulate helical, contrawound helix and coupled-cavity Slow-Wave Structures(SWS), which work in Ka-band, to investigate the backward-wave oscillation of millimeter-wave TWT. The results show that, space harmonics, which axial space harmonic number and azimuth space harmonic number are unequal, are evident in helical SWS, the SWS runs a risk of backward oscillation near the mode. Relatively, contrawound helix shows excellent ability in restraining backward oscillation by improving interaction impedance and the normalized frequency which can work without backward oscillation. And coupled-cavity should avoid working around those frequencies where phase shifts per cavity are or .