Research On Applications Of Staggered Double Vane Slow-wave Structure

Slow wave structure (SWS) is the core part of the linear beam vacuum electrondevices (VEDs) for generating or amplifying the microwave. The sheet beam electrondevices have become a new research direction in the vacuum devices communitybecause these devices were proved to be an effective way to provide much higher outputpower relative to traditional pencil beam counterparts. The VEDs with lower operationband in the microwave and millimeter wave spectra have been studying for a long timeand they are relatively more reliable and steady. A grate number of these devices havebeen put in the military and industrial applications. With the development of the solidstate devices (SSDs), some low power vacuum devices have been replaced by them.However, the SSDs operating in short millimeter wave band have not yet developed andmost of them are under studying. The VEDs can easily operate in the band and everhigher frequency bands, nevertheless most of these devices are still in developing. Withthe rapid advancement of modern microwave techniques, the demand for high operationband and high output power devices becomes more and more active, and it is the aimfor the researchers. In conclusion, it is the grate science value and practical significanceto study the high power short-millimeter wave vacuum electron devices.Base on the staggered double vane SWS, the W-band and140GHz band sheet beamhigh power traveling-wave tubes (TWTs) and backward wave oscillators (BWOs) werestudied in the dissertation with theory analysis, computer simulations and experiments.Some RF components for these devices and an electron optical system for this kind ofsheet beam devices were proposed. A staggered double vane TWT operate with pencilbeam and the corresponding electron gun were presented. Finally, a numericalcalculation method-virtual boundary element method was theoretically studied and itwas applied in the calculation for a multistage depressed collector. The main contentsand keys of innovation are as follows:(1) The staggered double vane structure was intensively analyzed from its modestructure, field structure, spatial harmonic, dispersion characteristics and interactionimpedance, and it was proposed to apply on W-band and140GHz-band sheet beam TWTs. The corresponding transaction structures for circuit and the input and outputcouplers were proposed which keep a low attenuation and reflection parameters of theRF system for the tubes. A concentrated attenuator which can eliminate the oscillationbut maintain a low circuit reflection was proposed and such attenuator guarantee asteady operation. Particle-in-cell (PIC) simulation revealed that the W-band TWT canproduce very high power in a broad band. This study laid a solid foundation fordeveloping broad band high power short-millimeter wave amplifiers.(2) The application of staggered double vane to W-band and140GHz-band sheetbeam BWOs were proposed after analyzing the feature of BWO. The operation modeand spatial harmonic which are best fit for BWO were selected and the operation bandsand the corresponding tuning voltage scopes were predicted. The two sheet beamstaggered double vane BWO were constructed after presenting its circuit transitionstructure and output coupler. The simulation results show that the W-band and140GHz-band BWO can offer watt-class steady average power in a relative wide band.These studies offered a solution for large power short-millimeter wave radiationsources.(3) After the studying of the sheet beam devices, a sheet beam electron gun wasproposed, a sheet beam multi-stage depressed collector were invented and a periodicalcusped magnet focus stack was designed. Finally an electron-optical system wasestablished. Numerical calculation results demonstrated that the gun can produce therequired sheet beam, the focus stack can achieve a good-quality sheet beam focus, theelectrons can uniformly land on the electrodes of the collector and the collectorefficiency was high but with low backflow rate. Such study provides a completeelectron-optical system solution for sheet beam devices and laid a foundation fordeveloping high efficiency sheet beam vacuum devices.(4) The staggered double vane SWS was applied to W band pencil beam TWTthrough which can greatly alleviate the focus problem relative to sheet beam TWT.Calculation results show that it can produce over200W peak power in the band of88-103GHz providing a constant input power of0.1W. The beam focus was easy forsuch TWT therefore it is suitable for the application in the situation that the low ormiddle power is needed.(5) A computer numerical calculation method named virtual boundary element method was proposed for multistage depressed collector design. The theoreticalfoundation of such method for calculating the axial symmetry collector was discussed.This method can solve the problem of bigger error when calculation open structure withtraditional method and it also avoid the singular integral which the boundary elementmethod can not deal. It is fast and accurate in calculation. Accordingly, atwo-dimensional simulation code for collector calculation was written and anaxial-symmetric four-stage depressed collector was calculated and a good result wasobtained. Such method has a high practical value in designing high efficiency collector.(6) The processing scheme of the RF system for the W-band sheet beam staggereddoubled vane TWT was designed. The SWS and transition structure, input/outputcoupler and an impedance converter were fabricated, respectively. These componentswere combined to a RF system with the complete signal path and its transmissionperformance was tested. This experiment examined the transmission characteristics ofthe W-band staggered double vane TWT RF system and it is useful for futureinvestigation.