Tv receiver conversion for velocity modulation, april 1951. Increasing the disturbance amplitude results in disc formation. Reflex klystron is also known as a sutton klystron. Home communication systems reference and training manuals figure 49. It is known by this name due to its reflex action of electron beam. The microwave tube uses transit time in the conversion of dc power to radiofrequency rf power.
The next tongue twister we had to contend with was infinifocus hd crts, which turned out to refer to the muchevolved cathode ray tube that, with its longer neck, higherperformance scan velocity modulation, and improved electronic gun, runs rings around standard tubes. Full text of klystrons and microwave triodes see other formats. On return, the electron beam once again enters the same grids which act as a buncher, therby the same pair of grids acts. This page compares bwobackward wave oscillator vs bwabackward wave amplifier and mention difference between bwo and bwa including applications, principle of operation and features. Microwave engineering cavity klystron tutorialspoint. The reflex klystron contains a reflector plate, referred to as the repeller, instead of the output cavity used in other types of klystrons. Velocity modulation how is velocity modulation abbreviated.
Solidstate modulator for klystron gyrotron conditioning. Solidstate modulator for klystrongyrotron conditioning, testing and operation diversified technologies, inc. Now refer to figure 49 and notice that 2 a short time after. They are velocitymodulated tubes that are used in radars as amplifiers or oscillators. The klystron is mounted directly on the top cover of the modulator.
This microwave generator, is a klystron that works on reflections and oscillations in a single cavity, which has a variable frequency. Doherty and drain modulation envelope tracking receiver amplifier designs klystron iot ldmos transistor. Multicavity klystron s magnetic field coil assembly. Bwo vs bwadifference between bwo and bwa in rf microwave. Important question and answers on reflex klystron with. Velocity modulation definition of velocity modulation at. Their work was preceded by the description of velocity modulation by a. Velocity modulation occurs in the gap of the input resonator, the ultrahighfrequency field in the gap periodically accelerating half a cycle and decelerating half a cycle. Unfortunately, however, the term velocity modulation has also gained acceptance in an entirely different sense, as the velocity modulated klystron tube. Microwave engineering kg reddy college of engineering. Ppt slac klystron lectures powerpoint presentation free. The interchange of power is accomplished by using the principle of electron velocity modulation and lowloss. The figure1 depicts cross section of backward wave oscillator.
This name is given by the name of its inventor robert sutton, it allow the passage of electron beam through a single resonant cavity. Depending on this, the electrons coming out of the electron gun, get their pace controlled. In its effect on the momentum of the electrons, the rf gap field produces velocity modulation and, in modulating the. Cv67 reflex klystron, velocity modulated oscillator klystron reflex. Apr 01, 2016 1 deflection modulation is customarily referred to as velocity modulation since the lateral velocity of the scanning spot is modulated in the horizontal direction. The klystron power supply skps610 has built in modulation facilities of amplitude and frequency modulation. The oscillator consists of two closedloop floatingdrift. Velocity modulation definition and meaning collins. Group velocity is defined as energy propagation velocity. Applegate diagram showing beam electrons velocity and density modulation. Cv67 reflex klystron, velocity modulated oscillator. It was invented by the brothers russell and sigurd varian at stanford university. Kinematic theory of velocity modulation in this section and in the next, we present the theory.
Why is pulse modulation required in reflex klystron. Klystron works on the principle of velocity modulation of electrons. After the electron gun there are two focusing electrodes used to keep the electron beam in the center around the glass envelope. A klystron uses special resonant cavities which modulate the electric field. Another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron figure 29. However in our application is it amplitude modulation which must be transferred through the klystron by the directcomb loops to suppress phase modulation of the beam6,1, and so this simpler. Operation is similar to that of a klystronexcept that coupledcavity twts are designed with attenuation between the slowwave structure instead of a drift tube. Microwave tubes as microwave source oscillators and amplifiers. The velocity modulation results from 1 velocity modulation at injection, and 2 the periodic acceleration and deceleration of the electrons by the gap field. The multi cavity klystron consist of a glass envelope in which there is an electron gun composed of heater and cathode. Ppt slac klystron lectures powerpoint presentation.
As shown in the given diagram it is composed of heater, cathode, focusing electrodes and repeller anode. Lowpower klystrons are used as oscillators in terrestrial microwave relay communications links, while highpower klystrons are. For this article, however, we will focus on another popular type. Klystronsthese are often called velocitymodulation tubes. As the beam has crossed a certain path, the velocity modulation become a modulation of. The electric field on the resonator keeps on changing its direction of the induced field. Klystrons back to main index go to the klystron index. A klystron is a specialized linearbeam vacuum tube, invented in 1937 by american electrical engineers russell and sigurd varian, which is used as an amplifier for high radio frequencies, from uhf up into the microwave range. In the buncher cavity, the electron beam undergoes the force a low energy alternate field that modulates the electron velocity. To understand the impact of the current modulation in a klystron, we have to understand both the. Modulator components are all accessible, and are mounted in plugin modules on the side walls of the oil tank which holds the pulse transformer and klystron socket.
One major type is the reflex klystron, which is used primarily as an oscillator. Multiphysics design of a ghz klystron alberto leggieri, davide passi, rocco citroni. The klystron was the first significantly powerful source of radio waves in the microwave range. Microwave engineering reflex klystron tutorialspoint. The next step is to take useful power from the beam. In passing across a gap the timevarying properties of the beam change because of its initial velocity modulation and also because of the electric field of the gap.
Electrical engineering stack exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. Unfortunately, however, the term velocity modulation has also gained acceptance in an entirely different sense, as the velocitymodulated klystron tube. Current modulation results from the beams interaction with the rf fields in a cavity, and in turn is responsible for driving modulation in the next rf cavity. Comsol conference 2015 grenoble multiphysics design of a klystron buncher the analysis follows a multiphysics model approach, in order to prevent alterations of the electromagnetic em behavior, while exposing the device to these multiple physics factors. Computational investigation on the effect of velocity. Electron beam current modulation in a klystron is the key phenomenon that accounts for klystron gain and rf power generation. One present version of the clw modulator meets the following performance. Tianjin radio and television tower amplifier designs 6. This change has a direct effect on the design of the klystron modulator. A klystron uses the kinetic energy of an electron beam for the amplification of a highfrequency signal. In the floating drift klystron, electrons pass successively through the gaps of cavity resonators see figure 1. The microwave tube was developed when the use of the frequency spectrum went beyond 1,000 megahertz and into the microwave range. Used in early 10 cm radar systems as a local oscillator. The difference between reflex and twomulti cavity klystron is that, reflex klystron uses single cavity for modulationdemodulation.
Klystron an ultrahighfrequency electronic vacuum device in which a steady stream. The advent of vacuum tubes, klystron being one of its kind is. The microwaves can be radiated either without modulation or 11740. Even if magnetron structures were described since the twenties, more serious investigation on velocity modulated or vm tubes started around the second half of the thirties, to overcome the. Would you like to make it the primary and merge this question into it. Klystron article about klystron by the free dictionary. A loop coupling is used inside the cavity to get the output. The present study concerns low velocity jets and hence no turbulence model has been incorporated. The electrons pass through the cavity and undergo velocity modulation, which produces electron bunching and the beam is repelled back by a repeller plate kept at a negative potential with respect to the cathode.
Hansen was instrumental in the development of the klystron and was cited by the varian brothers in their 1939 paper. The electron beam is velocity modulated when it first passes through the cavity. Reflex klystron or repeller klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron repeller klystron. Klystrons can be used in the uhf region 300 mhz to 3 ghz up to 400 ghz. This amplitude modulation is generally used along with vswr measurements in slotted line technique. Now understand the concept of reflex klystron in microwave engineering in details through following questions and answers. Reflex klystron consists of an electron gun, a cathode filament, an anode cavity, and an electrode at the cathode potential. The net effect of velocity modulation is to form a currentdensity modulated beam that varies at the same rate as the gridsignal frequency. Reflex klystron is a microwave device that works on principle of velocity modulation in addition to current modulation. The results of computer simulation of a twostage millimeterwave klystron oscillator are reported. The reflex klystron is an oscillator with a built in feedback mechanism. The oscillator consists of two closedloop floatingdrifttube klystrons with the output cavity. Modulator components are all accessible, and are mounted in plug in modules on the side walls of the oil tank which holds the pulse transformer and klystron socket.
Velocity modulation definition of velocity modulation by. Velocity modulation definition at, a free online dictionary with pronunciation, synonyms and translation. Amplifier digital efficiencyreceiver klystron 6% tetrode 9% bi. In a reflex klystron, a small modulation of the repeller voltage is more often employed to fix the emitted frequency to that of a microwave resonator by a phase locking loop technique. Comsol conference 2016 munich multiphysics design of a ghz klystron the analysis follows a multiphysics model approach, in order to prevent alterations of the electromagnetic em behavior, while exposing the device to these multiple physics factors. Modulation is accomplished by varying the velocity of the beam, which causes the drifting of electrons into bunches to produce rf. Klystron multi cavity klystron, reflex klystron, working. For waves composed of two components with different frequency. Klystrons make use of the transittime effect by varying the velocity of an electron beam. The klystron was the first embodiment of the velocity modulation principle. Velocity modulation definition is modification of the velocity of a stream of electrons by imparting alternate accelerations and decelerations to the electrons in such a way that they are caused to bunch together with the result that each bunch causes a cycle of current as it passes an output electrode. Klystron tube article about klystron tube by the free. For small modulation amplitudes in the appropriate frequency range, bulging of the liquid jets with finite periodicity is observed.
Cavity of a repeller klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron repeller klystron. All these components are enclosed in a glass envelope. The modulator is the dc power supply for the klystron. Pdf computer simulation of a twostage millimeter wave. This year marks the 60th anniversary of the birth of the klystron at stanford. Basic klystron rf power input rf drive rf power output energy modulation d v z,0, i 0 v z,0, i 1 modulate decelerate v c e z e z velocity bunching beamtube must not propagate the rf backward wave or the tube can oscillate.
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