Simulation Investigation of Backward Wave Oscillation of Millimeter-wave TWT
Lu De-jian①② Wang Zi-cheng① Liu Pu-kun①
①(Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China) ②(Graduate University of Chinese Academy of Sciences, Beijing 100039, China)
Abstract：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 π 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 π or 2π.
2008, Vol. 30 
