Traveling wave tube working fundamentals operations. The technique is illustrated by its application to a 70. The basics of travelling wave tube amplifiers scm01 roberto dionisio, claudio paoloni european space agency lancaster university roberto. The twt demonstrates more than 700w radiofrequency peak output power within a 2.
The ability of thz wave to penetrate some materials that are usually opaque to both visible and infrared radiation attracts a lot of research interests. The principle of the twt is to amplify an applied em wave of a speci. Twt being an linear beam device mainly used in microwave amplifier in which the bunching occurs continuously and to extend the interaction we introduce slow wave structure so that the electrons beam rf signal move with same velocity in the same direction. Most of the swss proposed so far do not support all the goals mentioned above. Study of propagating characteristics for folded waveguide twt.
A design study for a wband travelingwave tube twt using a staggered doublevane slow wave structure combined with a sheet electron beam shows that an output power of over 1 kw should be possible. The new wavering helical wrh slowwave structure for. This type of slow wave structure tends to be limited to frequencies below 100 ghz, above which ringbar and other structures may be employed. Simulation and microfabrication development of foldedwaveguide slow wave circuit for thz twt 2 communication 16. The twt package, which provides points for attachment to the using.
Slow wave structures act to reduce the group velocity of a transmission line, or increase its group delay compared to a normal fast wave structure. Google as you are already aware of the procedure of generation of electron beam and the usage of slow wave structure to ensure the interaction of rf wave with electron beam in the helical str. Slow wave structures are useful in shrinking electricallylong elements. The feature of the ringloop slow wave structure is high coupling impedance and low harmonic wave components. Belonging to the traveling wave tube family, it is an oscillator with a wide electronic tuning range.
What makes the travelling wave tube twt able to amplify. Fullwave analysis of the high frequency characteristics of. A simple method based on the physics characteristics to get the main parameters of folded waveguide traveling wave tube twt circuit is present. Modeling and characterization of a slowwave structure for a sheetbeam subthz twt amplifier. Ringloop slow wave structure a ring loop twt uses loops as slow wave structure to tie the rings together. The slow wave structure has been modeled and coldtest characteristics data were obtained. This paper describes the analysis of helix slow wave structure sws for a high efficiency space traveling wave tube that is carried out using ansoft hfss and cst microwave studio, which is a 3d electromagnetic field simulators.
Travelling wave tube basics, working and applications twt. Modeling and characterization of a slow wave structure for a sheetbeam subthz twt amplifier. Glenn research center, cleveland, ohio a finnedladder structure has been in vented in an effort to improve the design of the slow wave circuit of a traveling wave tube twt. Equivalent circuit analysis of a ring bar slow wave structure for highpower traveling wave tubes. A wideband twt universally uses helical slow wave structure sws as the interaction structure due to its nonresonant behaviour and consequent wide bandwidth potential 1.
Investigation of angular logperiodic folded groove waveguide. This unique ringloop slow wave structure used in these pulsed twt s provides high gain at kilowatt peak rf power levels without oscillation. Therefore, the sws holds the key to improving the performance of twts. But owing to changes of propagating character by reflecting of waveguide bend and electron beam hole, stopband can be formed. Analysis of coupledcavity slowwave structures for space twt. Metamaterialbased slow wave structures for travelling wave tubes. The point of departure for the design effort was a prototype twt. From the measured results, the trapezoidal vane structure appeared to be. The rf performance of a twt is primarily decided by the design of the helix slow wave structure. In this paper, a novel wband slow wave structure sws for traveling wave tube twt amplifier supporting a sheet beam is proposed. Design of helix slowwave structures for high efficiency twts. A backward wave oscillator bwo, also called carcinotron a trade name for tubes manufactured by csf, now thales or backward wave tube, is a vacuum tube that is used to generate microwaves up to the terahertz range. A design study for a wband traveling wave tube twt using a staggered doublevane slow wave structure combined with a sheet electron beam shows that an output power of over 1 kw should be possible.
The slow wave structure gives the twt its wide bandwidth. Such a device could significantly extend the range of possibilities for microwave beam control at the high level of radiated power. What is the purpose of slow wave structures used in twt. The new wave ring helical wrh slow wave structure for traveling wave tube amplifiers nasser panahi 0 s. The analytical design of a folded waveguide slowwave. Waveguide structure with an inner rod supporting slow wave propagation allows one to combine a twt amplifier and a surface wave radiating antenna in a single hybrid device. Pdf equivalent circuit analysis of a ring bar slowwave. Evaluation of some slowwave vane structures for a miniature. A microwave slowwave circuit that supports a traveling wave of electromagnetic energy with which the electron beam can interact.
H and e plane loaded slow wave structure for wband twt. In twt, since the beam can be accelerated only to velocities that are about a fraction of the velocity of light, slow wave structures are used. A design study for a wband travelingwave tube twt using a staggered doublevane slowwave structure combined with a sheet electron beam shows that an. The interaction between electromagnetic wave and electron beam has also been analyzed qualitatively. Therefore ringloop traveling wave tube has advantages of high gain 4060 decibels, small dimension, higher operating voltage and less danger of the backward wave oscillation. These devices are capable of higher power levels than conventional helix twts, but have significantly less bandwidth of 515 percent and lower cutoff frequency of 18 ghz. Finnedladder slow wave circuit for a twt impedance and gain per unit length are increased. Slow wave structures are special circuits that are used in microwave tubes to reduce wave velocity in a certain direction so that the electron beam and the signal wave can interact. Relativistic twt with a rod slowwave supporting structure. A kaband travelingwave tube twt was fabricated with a folded waveguide fwg as its slow wave structure. Pdf analysis of a coupledcavity slow wave structure for. Analysis of a coupledcavity slow wave structure for a twt.
In this paper slow wave structures with some improved parameters and properties are introduced as the solution to the. Oct 04, 2017 travelling wave tube basics, working and applications twt by engineering funda, microwave devices engineering funda. Folded waveguide circuit fwc is an ideal slow wave structure for broadband power traveling wave tube twt in millimeter wave. For twt high power bandwidth gain at least 20% of the proposed design of slowwave systems type chain connected resonators representing the waveguides periodically blocked by the same orifice with slits communication with one or more channels for the passage of electrons. The sws is based on a rectangular waveguide with hplane and eplane loaded metal corrugations. Mar 26, 2020 the slowwave structure sws, where the beamwave interaction occurs, is the core part of a twt, and it determines many of the characteristics of the twt. Operation is similar to that of a klystron, except that coupledcavity twts are designed with attenuation between the slow wave structure instead of a drift tube. This paper describes an approach of designing a coupledcavity slow wave structure ccsws for a high power traveling wave tube twt using hfss code, which is a 3d high frequency. Role of helix thickness in the field analysis and characterisation of the slowwave structure of a broadband twt. In the slow wave structure, the electromagnetic wave velocity is kept synchronized with the electron beam velocity to generate interaction and energy exchange between them. A test structure of the proposed h and eplane loaded hel sws with purposely.
The bandwidth and other performance like gain eciency etc. Ghorannevis 0 0 plasma physics research center, science and research branch, islamic azad university, tehran, iran in this paper, the new slow wave structure called wave ring helix to enhance the power of the traveling wave tubes is introduced. Simulation and microfabrication development of folded. It is shown that the use of a section with increased phase velocity increases the beam efficiency of a twt while reducing the generation of second harmonic power. Twt s using this structure provide beam efficiencies as high as 25 percent without collector depression. The twt, because of its construction and working principle has enormous bandwidths and low noise. A wideband twt universally uses helical slowwave structure sws as the interaction structure due to its nonresonant behaviour and consequent wide bandwidth potential 1. Pdf modeling and characterization of a slowwave structure. Analysis of helix slow wave structure for high efficiency. Travelling wave tube basics, working and applications twt by engineering funda, microwave devices engineering funda.
The heated cathode at one end of the tube produces a beam of electrons and is attracted to the collector at the other end of the tube. Two approaches of simulating the dispersion and impedance characteristics of the helix slow wave structure have been discussed and compared with measured results. The dispersion characteristics of six vane type slow wave structures were experimentally measured near 1 ghz to determine applicability in an electrostatically focused 30 ghz miniature traveling wave tube twt. The stwt studied in this paper is a helix traveling wave tube. Design of folded waveguide slowwave structure for band. H and eplane loaded slowwave structure for wband twt. An important component of the twt is the slow wave structure sws, where the electron beam interacts with a slow electromagnetic wave leading to energy transfer from the beam. The traveling wave tube can be used as a medium or high power microwave, amplifier. The helix pitch for the input section has been selected to establish the. Schematic of a thz travelling wave tube with planar rf slow wave structure and sheet beam. Equivalent circuit analysis of a ring bar slowwave structure for highpower travelingwave tubes. Role of helix thickness in the field analysis and characterisation of the slow wave structure of a broadband twt. The collector that collects the spent electron beam emerging from the slowwave circuit. Excitation of a slow wave structure michigan state university.
The study in the paper can provide some references for the design of coupledcavity slow wave structure for space twt. This is achieved by passing the em wave through a slow wave structure sws simultaneously with an electron beam, such that waveand beam pass through the structure with similar velocities, for the em wave this is determined by. Figure 1119 shows the exponential signal growth along the travelingwave tube, but it is not to scale the actual gain could easily exceed 80 db. The formulas of dispersion and interaction impedances of the hybrid modes are obtained by combining the helmholtz equation with the appropriate boundary conditions.
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