The Theory And Research Of Terahertz High Harmonic Traveling Wave Tube

With the rapid development of science and technology,new research and development direction is derived from of the cross subject.such as the terahertz technology.Frequency of terahertz wave is between infrared and microwave,because of its unique superiority,terahertz wave is widely used in mass communication,electromagnetic confrontation,detection.But lack of high power and low cost terahertz radiation sources are limit the development of terahertz technology.We combine the higher harmonic mechanism of free electron laser with the principle of traveling wave tube,a new kind of vacuum terahertz source-high harmonic frequency doubling travelling wave tube(HHTWT)have been designed.This device has adopt the low price of millimeter wave source as drivers,the output signal is terahertz signal.HHTWT has the advantage that the big output signal power and output frequency is adjustable.Two section of the slow wave line in HHTWT work in different frequency,but they have the same phase velocity,so make the design process difficulty.A 346 GHz HHTWT designed in this paper,the input signal frequency is from 84.5 GHz to 84.5 GHz,the power of input signal is 100 mw,the output signal frequency is 338 GHz-338 GHz,bandwidth of 12 GHz,the output power of about 100 mw.And to work in the D band HHTWT experimental results are analyzedIn this paper,the main work includes:1)selection of folded waveguide as the HHTWT slow wave line,design the slow wave line of two pieces of work in different frequency band,modulation period of center frequency 86.5 GHz,the center frequency of 346 GHz in radiation section,and to analyze the high frequency characteristics.2)to work in the terahertz band electron optical system design and simulation of gun type for Pierce no gate electron gun,for PPM focusing system.19 k V electron gun working voltage,working current 15 ma,stream channel radius of 0.08 mm.The cathode emission density Jk = 7 a/cm2,diversion coefficient,the cathode surface to plane,radius of 0.3 mm.Generally in the plane of the cathode surface for focusing of electron gun is difficult,and laminar flow resistance is poorer,after a series of simulation and optimization finally got better effects of laminar flow and focus.3)note wave of HHTWT carried on the detailed analysis of the interaction between design HHTWT slow-wave structure,complete in its optimization.The cut-off frequency modulation period is 75 GHZ,75 cycles.The cut-off frequency of 300 GHZ in radiation section,40 cycles.Output signals for four times the size of the input signal frequency,and frequency spectrum purity,low harmonic signal.4)the terahertz band HHTWT design difficulty is big,the high technical requirements,so we have to work in the first harmonic HHTWT D band three times the processing test.Test results show that the components in the input signal of 43.3 GHz to 45.3 GHz,power 200 mw in 130 GHz ? 136 GHz,the output power of 50 mw ? 500 mw output signal.Proved HHTWT can generate and enlarge higher harmonic signal,provides a theory in the terahertz band HHTWT experimental basis.