Study On A Type Of Slow Wave Structures Used In The Microwave Source

Traveling wave tube (TWT) is the most important type of microwave vacuumtube. It has been frequently used as millimeter wave radar, guidance, tactical andstrategic communication, electronic countermeasure, remote sense, radiationmeasurement and so on. Its performance directly influences the level of the weaponequipments, and it has importantly realistic significance for the study on the new typeof high power and short mm-wave traveling wave amplifiers. In this dissertation, wehave made detailed study on a type of slow wave structures (SWS). Several importantand valuable results which bring forth new ideas are achieved and listed as thefollowing:First, rectangular waveguide structure with dielectric loaded on the up-and-downplates is studied based on dielectric loaded cylindrical waveguide. First, the dispersionrelation is given by equivalent circuit and field matching, and the electromagneticenergy excited by a bunched relativistic electron beam is obtained by calculating theR/Q value. Second, the influence of dipole mode on the stability of electron beam isanalyzed. Finally, we design a high power microwave generation device. Test resultsare in good agreement with the predictions.Second, a new scheme using the photonic crystal as the shielding tube of travelingwave tube (TWT) slow wave structure (SWS) is put forward, and the feasibility of thisscheme is proved. Mode analysis is done as to this structure. Based on the forbiddenband characteristic of photonic crystal, the dispersion and coupling impedance ofphotonic crystal SWS are calculated. The analysis of the calculation results shows that,photonic crystal has an important effect on the TWT SWS in oriented selecting mode.The work of this paper lays the foundation for TWT realizing higher mode operation.Third, a kind of photonic crystal grating slow-wave circuit, cross-sectiondistributing two-dimensional photonic crystal slow-wave circuit (CD2DPhSWC), wasproposed. And the way of design for CD2DPhSWC was put forward, too. To simplythe design, the way was actualized by two steps. The two steps are the calculation ofthe photonic band gap (PBG) for the TE polarization and the dispersion of the equivalent rectangular waveguide grating. The numerical results explain that thebandwidth of the traveling wave tubes (TWTs) based on CS2DPhSWC is wider, andthe operating voltage is lower, than that of the rectangular waveguide grating.Correspondingly, the cost of the TWTs will decrease.Four, for solving the processing precision and power capacity of foldedwaveguide traveling wave tube operating in3mm band and above, a new kind offolded waveguide slow wave structure of which finite periodic structure is irregular isproposed. Firstly, we give the reason why using this structure can enhance couplingimpedance of high harmonic efficiently, and derivative the expressions of thedispersion and coupling impedance. A group of design parameters which are optimizedis obtained by the numerical calculation, and this is the authority of operating point oftraveling wave tube. Finally, the gain is obtained by MAFIA particle simulationsoftware.