[2] CHEN V C,LI F,HO S S,et al. Micro-Doppler effect in radar: phenomenon, model, and simulation study[J]. IEEE Transactions on Aerospace and Electronic Systems, 2006,42(1):2-21.

[3] YANG Yang,HOU Chunping,LANG Yue,et al. Person identification using micro-Doppler signatures of human motions and UWB radar[J]. IEEE Microwave and Wireless Components Letters, 2019,29(5):366-368.

[5] GARRY J L, SMITH G E. Experimental observations of micro-Doppler signatures with passive radar[J]. IEEE Transactions on Aerospace and Electronic Systems, 2019:55(2):1045-1052.

[7] FU Wenjie, YAN Yang, LI Xiaoyun, et al. The experiment of a 220 GHz gyrotron with a pulse magnet[J]. Journal of Infrared Millimeter & Terahertz Waves, 2009,31(4):404-410.

[8] YAN Y, LI X, YUAN X, et al. A 0.423 THz second harmonic gyrotron oscillator[J]. Chinese Journal of Electronics, 2013, 22(2):415-418.

[9] NIU Xinjian,LEI Chaojun,LIU Yinghui,et al. Study of the effect of the electron beam parameters on a 0.4 THz second harmonic gyrotron[J]. IEEE Transactions on Electron Devices, 2014,61(9):3324-3328.

[10] ZHANG Tianzhong,ZHAO Qixiang,YU Sheng,et al. The nonlinear simulation, design and experiments on 0.42 THz gyrotron with gradually tapered complex cavity[J]. Vacuum, 2015,125(4):85-92.

[12] LOHRMANN D R. A coherent mm-wave radar using an incoherent transmitter[J]. Microwave Journal, 1991,34:150,152,154.