In the floating drift klystron, electrons pass successively through the gaps of cavity resonators see figure 1. Staggertuned klystron with cavities resonant outside passband us65807a us3195007a. Velocity modulation an overview sciencedirect topics. Due to the dc voltage in the cavity, a radio frequency rf noise is generated.
Arsenjewaheil and oskar heil wife and husband in 1935, though the varians were probably unaware of the heils work. Klystron beambunching lecture international nuclear information. Each slanting line represents a plot of an individual electrons distance over time. And in the cavity gap, the velocity of the electrons is modulated. A klystron is a cavity acting as buncher and catcher is used as microwave tube for. A klystron is an electron tube in which the following processes may be distinguished.
Difference between velocity and current modulation in klystron. When all ports are terminated in their characteristic impedances, there is free transmission of. An experimental investigation of velocitymodulated electron. However, space charge repulsion modified by the drift tube causes the beam to debunch. Their work built on the description of velocity modulation by a. Development of a steady state simulation code for klystrons. The phase velocity of the wave along the coil for free space case in ms is. The electric field on the resonator keeps on changing its direction of the induced field. A klystron also known as a klystron tube or klystron amplifier is a vacuum tube that is used to oscillate and. Ep0181214b1 beam tube with density plus velocity modulation. Klystron tube is basically an amplifier device, which amplifies the microwaves in terms of gain and peak power output. So, working principle of reflex klystron is velocity and current modulation. Free download in pdf microwave engineering multiple choice questions and answers for competitive exams.
The variation in the velocity of electrons while moving inside the tube is known as velocity modulation. Velocity modulation at the input cavity creates density modulation at the output cavity c. The operating frequency of klystrons and magnetrons is set by the cavity resonators. An electron beam is formed in an electron gun and passed through the gaps associated with the two cavities fig. In the last years, several works have investigated the influence of a fermi velocity modulation in the electronic and transport properties of graphene 20,21,22,23,24,25,26,27,28,29,30. It usually provides display for beam voltage, beam current and repeller voltage.
Density modulation at the input cavity creates velocity modulation at the output. The radiated power due to current density modulation m j. Klystron definition of klystron by the free dictionary. The velocity modulation process takes place as before, but analysis shows.
This amplitude modulation is generally used along with vswr measurements in slotted line technique. In an electron tube, a region substantially free of externally applied. Downstream, this velocity modulation results in a current modulation as some of the electrons overtake others. For example, microwaves can be propagated through free space utilizing. The theory of such a device has been studied by many authors, but the detailed comparison of the theory with practical results is generally difficult, owing to the high operating frequency. Velocity modulation definition of velocity modulation by. Reflex klystron is a microwave device that works on principle of velocity modulation in addition to current modulation. Reviewer in microwave communications ece board exam. Such a system was called an optical klystron buncher okb 9. Arsenjewaheil and oskar heil wife and husband in 1935, though. The phase velocity of the wave along the coil for free space case in m.
Thus twocavity klystron amplifier utilizes the kinetic energy of moving electron beam for signal amplification. Klystron tube article about klystron tube by the free. Aug 19, 2020 a klystron also known as a klystron tube or klystron amplifier is a vacuum tube that is used to oscillate and amplify microwave frequency signals. So, electron beam is injected from the cathode and that injected beam travel with a uniform velocity till the cavity. The velocity modulation is converted to a beam current modulation downstream, which induces an amplified version of the input signal in the output cavity. Hansen was instrumental in the development of the klystron and was cited by the varian brothers in their 1939 paper. In the klystron, the electron beam passes through a hole in a resonant cavity which is connected to the source rf signal. Note that of parameters 26, only parameters 2 and 6 are free. Feb 15, 2020 in a klystron amplifier, velocity modulation of the electron beam is produced by the catcher cavity. A periodic variations of the longitudinal velocities of the electrons forming the beam in a region confining a radiofrequency field b conversion of the velocity variation into conductioncurrent modulation by motion in a region free from radiofrequency. The reflex klystron uses a singlecavity resonator to modulate the rf beam and extract energy from it.
Advantage of using gaas in mesfet as compared to use of silicon is option a. An electronic oscillator can also be made from a klystron tube when the second cavity resonator is fed back to the first one with a coaxial cable or waveguide. Klystron article about klystron by the free dictionary. Sep 06, 2019 what is the difference between klystron tube and twt. These short solved questions or quizzes are provided by gkseries. Depending on this, the electrons coming out of the electron gun, get their pace controlled. Pipe is designated by a nominal pipe size based uponthe id inside diameter of the most common wall thickness. Introduction to the twocavity klystron amplifier technical. An applegate diagram illustrating the bunching of electrons caused by the velocity modulation effect of a klystron on a number of representative electrons 24 per cycle. Jun 04, 2020 from wikipedia, the free encyclopedia. Microwave engineering quiz microwave engineering multiple. Scribd is the worlds largest social reading and publishing site. A high velocity electron beam produced by the accelerating anode is passed through a buncher cavity, drift space, catcher cavity and finally collected by the collector terminals. The klystron power supply skps 610 has built in modulation facilities of amplitude and frequency modulation.
As the electron beam moves through a klystron s intercavity drift space. To understand the modulation of the electron beam, entering the first cavity, lets consider the electric field. Once the electrons leave the buncher cavity, they drift with a velocity given by velocity modulation equation along in the field free space between the two. A report will be given about a line type modulator with a peak power output of 62. Us3195007a staggertuned klystron with cavities resonant. Klystron works on the principle of velocity modulation of electrons. Jan 12, 2020 velocity modulation process in two cavity klystrons video lecture from microwave linear beam tubes o type chapter of microwave communication subject for all engineering students.
Another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron figure 29. It is a velocity modulated tube in which the velocity modulation process produces a densitymodulated beam of electrons. The electron beam injected from the cathode is velocity modulated by the cavity gap voltage. For proper operation, a magnetron must be accompanies by a permanent magnet. First in the world to be free of cd and cr vicdfree output fluorescent surface. Alternatively, the equation of velocity modulation can be given by 4. Frequency modulation at the input cavity creates velocity modulation at the output cavity b. Tech regular degree examination, november 2017 scheme. Derivation of velocity modulation in reflex klystron. The 2 cavity klystron amplifier is widely used microwave amplifier, operated by the principles of voltage and current modulators.
In the linear region, this process produces oscillations. 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. The klystron was the first embodiment of the velocity modulation principle. A klystron uses the kinetic energy of an electron beam. The effect of velocity modulation produces bunching of the electron beam or current modulation. The velocity and current modulation take place in the cavity gap. It uses velocity modulation in order to transform continuous electron beam into corresponding microwave power.
The distances between cavities in a klystron are chosen to be approximately onequarter of a plasma wavelength for opt,imal bunching. These short objective type questions with answers are very important for board exams as well as competitive exams. A klystron is a cavity acting as buncher and catcher is used as microwave tube for option a. Efficient microwave tubes usually operate on the theory of electron velocity modulation concept the electron transit time is used in the conversion of dc power to rf power linear beam o tubes the paramount o type tube is the two cavity klystron followed by the reflex klystron. The coupledcavity twt overcomes this limit by twr the helix with a series of coupled cavities arranged axially along the beam. Reflex klystron vacuum tube manufactured goods free 30. Klystron microwave test bench gunn microwave test bench. Microwave engineering cavity klystron tutorialspoint. Moreover it uses repeller inplace of catcher cavity. In the drift tube after the cavity this velocity modulation gives rise to a grouping opposed by the coulombian repulsion forces. Pdf design of rf cavities and rf section of s band klystron. In klystron strong electrostatic fields are required for its operation efficiently.
Our present choice is a l o w v oltage 25kv klystron with a modulation anode, periodic permanent magnet ppm focusing and a sheet beam with an aspect ratio of 30. One of the earliest and simplest forms of velocity modulation device is the 2cavity klystron described by the varian brothers in 1939. Reflex klystron or repeller klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron repeller klystron. The slope of each trajectory is proportional to each electrons velocity. An electron tube used to amplify or generate ultrahigh frequency by means of velocity modulation. Their work was preceded by the description of velocity modulation by a. 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 process in two cavity klystrons. All of these tubes use the same basic bunching of electrons to provide the amplification process, and differ largely in what process causes the velocity modulation to occur.
His original patent, device for and method of controlling high frequency currents, was filed in and granted in difference between velocity and current modulation in klystron. Reflex klystron is a single cavity klystron that can be used as low power microwave oscillator. As we have already discussed in the introduction that klystron is based on the principle of velocity modulation. The difference between reflex and twomulti cavity klystron is that, reflex klystron uses single cavity for modulation demodulation. It had been widely used for radar systems in second world war2. Beam tube with density plus velocity modulation publication number ep0181214b1 ep0181214b1 19900117. Helical waveguides have very nonlinear dispersion and thus are only narrowband but wider than klystron. It was invented by american electrical engineers russell and sigurd varian. Development of a steady state simulation code for klystrons core.
Important question and answers on reflex klystron with. It houses am modulation, fm modulation and external modulating signal functionalities. Velocity modulation in klystron amplifier electronics and. 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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