Research On The High Frequency Structure Of A W-band Gyro-twt With Periodic Dielectric Loaded Circuits

Compared with conventional Traveling Wave tube, The gyro-TWT has the advantage of higher power, higher efficiency, higher gain and wider bandwidth capabilities in millimeter wave band. More and more countries pay attention to the gyro-TWT after the first gyro-TWT was been invented. But it is uneasy to solve the instability problem which is due to its working-principles.In this thesis, its main ideas are how to restrain the self-oscillation. Based on the fundamental principles of gyro-TWT, the dispersion equation of it has been derived, and the principles of gyro-TWT which its high frequency structure is constructed with period rings of dielectric and copper has been analyzed also. A kind of high frequency structure of W-band is driven by a50kV2A helical electron beam with a velocity ratio of1.3was attained by numerical computation. After simulation and optimization by MAGIC software, the result performs maximum peak output power of25.9kW,25.9%efficiency at center frequency,71-dB saturated gain, and5.1GHz absolutely bandwidth. The I/O structure has been designed by numerous calculations. HFSS and ANSYS software are used to analyze them.The main contents are as follows:1. The beam-wave interaction has been studied though small signal theory, and the dispersion equation of gyro-TWT. The graph of dispersion has been drawn based on the dispersion equation of gyro-TWT, then the physical mechanism of self-oscillation and back-wave-oscillation. The influence to the stability of gyro-TWT has been derived on theory. And then some parameters, such as start-oscillation length and start-oscillation length current The results show that2.35cm is the shortest start-oscillation length.2. The gain of gyro-TWT has studied though large signal theory, and it then been calculated. The largest output power point is at the length of14cm.3. The principles of gyro-TWT which its high frequency structure is constructed with period rings of dielectric and copper has been derived. The relationship of decrement per unit length and start-oscillation length has been attained by numerical calculation. After calculation, the crude parameters of high frequency structure with period rings of dielectric and copper are attained.4. After simulation and optimization by MAGIC software, the final parameters are confirmed:waveguide radius is2cm,the length of last copper waveguide is2.3cm, he length of period loaded waveguide is11.2cm(the length of dielectric ring per period is0.42cm, he length of copper ring per period is0.31cm), the thickness of dielectric layer is0.05cm, dielectric ε=10-j11. The result performs maximum peak output power of25.9kW,25.9%efficiency at center frequency,71-dB saturated gain, and5.1GHz absolutely bandwidth.5、The input-output structure has been studied on theory, and the parameters are been obtained by numerical calculation. The design of input-window input-output structure and output window are finished. HFSS software is used to analyze them, the thermal analysis for output window has also been finished。...