Positive feedback excites spontaneous oscillations at the resonant frequency of the cavities. The two cavity klystron is a widely used microwave amplifier operated by the principles of velocity and current modulation. A novel feature of this design is a cavity which is simultaneously excited at two frequencies. Two cavity klystron as the name implies, this klystron uses two cavities. At a very high temperature, the cathode emits electrons. Pdf lowfrequency klystron for accelerator applications. Cavity type structures are the resonant structures.
It is known by this name due to its reflex action of electron beam. In the middle of these cavities, there is a grid allowing the electrons to pass. The name of this klystron is taken due to its reflex act of electron beam. The application for klystron with integral cavities is usually credited in the early 1939 to hahn and metcalf and to russell and sigurd varian, two brothers that. In klystron, each cavity operates independently and there is no mutual coupling. Two cavity oscillator klystrons have the advantage of being among the lowestnoise microwave sources available, and for that reason have often been used in the illuminator systems of missile. Oct 17, 2019 let us understand twt and klystron basics before we look into comparison between the two.
Microwave engineering example problems in this chapter, let us have some fun by solving a few numerical problems related to microwaves. Those electrons passing the first cavity gap at zeros of the gap voltage o r signal voltage pass through with. Content introduction of two cavity klystron construction of two cavity klystron two cavity klystron amplifier performance characteristics application 3. Introduction a klystron is a vacuum tube that can be used either as a generator or as an amplifier or as an oscillator, at microwave frequencies. Interaction in klystron occurs only at the gaps of resonant cavities. Lowfrequency klystron for accelerator applications. Depending on this, the electrons coming out of the electron gun, get their pace controlled. Reflex klystron microwave tubes klystron, reflex klystron, magnetron and twt reflex klystron is single cavity variable frequency microwave oscillator reflex klystron that works on reflections and oscillations in a single cavity 4.
The two cavity klystron is the simplest klystron tube. In this klystron, a single pair of grids does the functions of both the buncher and the catcher grids. Oct 03, 2016 on this channel you can get education and knowledge for general issues and topics. However, with the addition of intermediate cavities and other physical modifications, the basic two cavity klystron may be converted into a multicavity power klystron, capable of both highgain and highpower output. What is a klystron amplifier, types, differences and their. Dhanalakshmi college of engineering department of ece ec6701. View and download powerpoint presentations on two cavity reflex klystron ppt. Pdf complex dynamics of a twocavity klystron oscillator.
A reflex klystron consists of an electron gun, a cavity with a pair of grids and a repeller plate as shown in the above diagram. Two cavity klystron amplifiers working, amplification. Microwave communication questions and answers pdf free download for ece mcqs objective type interview questions lab viva manual gate cat syllabus. Dhanalakshmi college of engineering department of ece. Firstly, as we know that klystrons are used as amplifiers for microwave frequency and conventional vaccum tubes cant be used due to interelectrode capacitance and lead. All electrons injected from the cathode arrive at the first cavity. Amplification of such two cavity klystron is low and hence multi cavity klystrons are used. Pdf the effect of space charge on bunching in a twocavity. Linear beam tubes two cavity klystron hello my name is rajbala, i am pursuing phd under the guidance of professor. This klystron is totally dissimilar from cavity klystron because it has a single cavity and used for modulation otherwise demodulation. Klystron multi cavity klystron, reflex klystron, working.
Typical klystron failure modes burntout or shorted cathode filament beam interception erodes output cavity rf breakdown erodes the output cavity multipactoring on or near the output window sputters metal onto the ceramic window, resulting in breakdowns slow vacuum leak contaminates poisons the cathode. Working the first grid next to the cathode controls the number of electrons in the electron beam and focuses the beam. Find powerpoint presentations and slides using the power of, find free presentations research about two cavity reflex klystron ppt. Complex dynamics of a two cavity klystron oscillator with delayed feedback. The klystron amplifier can be used as an microwave oscillator or amplifier at low and high frequencies. Pdf simulation study of a wband broadband extended. A klystron amplifier uses different cavities which control the electric field around the axis of the tube. It is a narrow band device due to use of resonant cavities. These will set up a field in the third cavity, which produces more concentrated bunches and. Klystron, thermionic electron tube that generates or amplifies microwaves by controlling the speed of a stream of electrons. The major difference between klystron and twt is that klystron cavities are replaced by structure of helix shape in twt. The configuration shown in the figure is correct for oscillator operation.
Following are the benefits or advantages of klystron. Due to the number of the resonant cavities klystrons are divided up into two or multicavity klystrons, and reflex or repeller klystrons. Reflex klystron amplifier, microwave klystron amplifier. Now understand the concept of reflex klystron in microwave engineering in details through following questions and answers. However, a two cavity klystron oscillator is usually not constructed because, when the oscillation frequency is varied, the resonant frequency of each.
The voltage accelerates the dc electron beam to a high velocity before injecting it into the grids of the buncher cavity. The first cavity together with the first coupling device is. There are two cavities known as buncher and catcher cavity. Philips 55395 high power tunable twocavity klystron with internal feedback for use as continuous wave generator within the range from 8600 to 10 000 bcs. When used as an amplifier, the weak microwave signal to be amplified is applied to the buncher cavity through a coaxial cable or waveguide, and the amplified signal is extracted from the catcher cavity. Microwave engineering cavity klystron tutorialspoint. While a conventional klystron has one interaction gap per cavity. The main difference between two cavity reflex klystron amplifier. 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. This name is given by the name of its inventor robert sutton, it allow the passage of electron beam through a single resonant cavity.
The eik can be considered as a refinement of both two cavity klystron and coupled cavity twt. What is the principle of operation of a multicavity klystron. First of all, consider an electron a which passes through the resonator gap when the voltage across the gap is zero. Klystron amplifier the klystron amplifier can be used as an microwave oscillator or amplifier at low and high frequencies. A klystron uses special cavities which modulate the electric field around the axis the tube. Reflex klystron amplifier electronics club microwave. On each side of the cavity hole is a grid that the electrons pass through. Ece questions and answers on microwave engineering with explanation for various interview, competitive examination and entrance test. The vacuum tube consists of a cathode, which is heated by a filament. Klystrons are a special type of vacuum tubes that find applications as amplifiers and oscillators at microwave frequencies. The twocavity klystron is the simplest klystron tube. The multi cavity klystron consist of a glass envelope in which there is an electron gun composed of heater and cathode. To make an oscillator, the output cavity can be coupled to the input cavity s with a coaxial cable or waveguide. Important question and answers on reflex klystron with.
The simplest klystron tube is the twocavity klystron. For a gband sheet beam extended interaction klystron sbeik, an eightgap extended output cavity that operates in the 2. The electric field on the resonator keeps on changing its direction of the induced field. It is widely used microwave amplifier operated by principles of velocity and current modulation. The two cavity klystron in figure 27a and b may be used either as an oscillator or an amplifier. Request pdf on jun 1, 2019, shasha li and others published improvement of output performance in gband extended interaction klystron with narrow coupling cavity find, read and cite all the. There is anode used to attract the electrons emitted from the cathode. Two cavity klystron amplifier in the two chamber klystron, the electron beam is injected into a resonant cavity. Jul 31, 2018 technical article introduction to the two cavity klystron amplifier july 31, 2018 by mark mitchell klystron amplifiers are used in a variety of industries, including satellite systems, television broadcasting, radar, particle accelerators, and in the medical field. In the reflex klystron the same cavity is used for both bunching and catching. The reflex klystron contains a reflector plate, referred to as the repeller, instead of the output cavity used in other types of klystrons. In this video, i have explained two cavity klystron amplifier with following points 1.
The two cavity amplifier klystron is readily turned into an oscillator klystron by providing a feedback loop between the input and output cavities. The operation of reflex klystron is a little bit different from the two cavity klystron because there is only one cavity. A klystron is a microwave vacuum tube using cavity resonators to produce velocity modulation of the electron beam and produce amplification. Introduction to the twocavity klystron amplifier technical. Pdf the effect of space charge on bunching in a two. The klystron was the first embodiment of the velocity modulation principle. A grid is placed in the middle of these cavities to allow the electrons to flow.
To understand the modulation of the electron beam, entering the first cavity, lets consider the electric field. Cavity of a repeller klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron repeller klystron. Two cavity klystron amplifier is not lownoise device. It is given the name reflex klystron because of its reflex action of electron beam. After the electron gun there are two focusing electrodes used to keep the electron beam in the center around the glass envelope. The following figure depicts an example of multi cavity klystron amplifier. This single cavity is work like a buncher as well as catcher cavity. Assume that input signal is smaller than dc accelerating voltage. The electrons are originally accelerated to high velocity by a potential of several hundred volts and enter a narrow gap that forms part of a cavity resonator system see. The basic process by which a two cavity klystron amplifier operates is as follows.
In this tube there are two microwave cavity resonators, the catcher and the buncher. Improvement of output performance in gband extended. In order to achieve higher overall gain, one way is to connect several two cavity tubes in cascade, feeding the output to each of. Sep 21, 2017 content introduction of two cavity klystron construction of two cavity klystron two cavity klystron amplifier performance characteristics application 3. The two cavity klystron is a widely used microwave amplifier operated by the principles of velocity and density modulation. Thus the device used for amplifying microwave signals is known as two cavity klystron in the year 1937, american engineers russell and sigurd varian developed klystrons. The helix travelingwave tube twt, the coupledcavity twt, the forwardwave am plifier fwa, and the backwardwave amplifier and oscillator bwa and bwo are also 0type tubes, but they have nonresonant periodic structures for electron inter actions. The first difference is that and two cavity klystron there are two cavities, whereas in reflex klystron there is only one cavity which access both buncher cavity and catcher cavity. Difference between two cavity klystron and reflex klystron.
Oct 01, 2014 0type tube is the twocavity klystron, and it is followed by the reflex klystron. The first cavity together with the coupling device is termed as a buncher. The feedback path provides energy of the proper delay and phase relationship to sustain oscillations. Two cavity klystron amplifiers working, amplification and. It has two microwave cavity resonators the catcher and the buncher.
If a fraction of the output power is fed back to the input cavity and if the loop gain has a magnitude of unity with a phase shift of multiple 27t, the klystron will oscillate. Velocity modulation process in two cavity klystrons microwave linear beam tubes o type duration. If the instantaneous rf potentials on the two sides of a magnetron cavity are of opposite polarity, the operation is in the. 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. Extended interaction klystron eik technology preserves the ruggedness and high power capability of the conventional klystron. The simplest klystron tube is the two cavity klystron. With the signal applied in the first cavity, we get weak bunches in the second cavity. Microwave engineering ece questions and answers page 2. The principle of velocityvariation, first used in heil oscillators, was also used in other microwave amplifying and oscillating tubes. Modified image based on a drawing by christian wolffcc bysa 3. Microwave engineering example problems tutorialspoint.
The effect of space charge on bunching in a two cavity klystron. The power gain of a two cavity klystron amplifier is about 30 db. Instead of traveling only once through a straight driftspace, as in the two resonator klystron, the beam is turned back on itself by a retarding field. Due to this fact, usually it is used in the transmitter and not in the receiver. Linear beam tubes are of two types, cavity type and slow wave structure type.
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