Lowpower klystrons are used as oscillators in terrestrial microwave relay. It is possible to produce oscillations in a klystron device which has only one cavity, through which electrons pass twice. Multi cavity klystron two cavity klystron used as lowpower. Microwave engineering ece questions and answers this is the electronics and communication engineering questions and answers section on microwave communication with explanation for various interview, competitive examination and entrance test. Three power sources are required for reflex klystron operation. Klystron multi cavity klystron, reflex klystron, working. Why is pulse modulation required in reflex klystron. Another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron figure 29. Reflex klystron used as a lowpower microwave oscillator 2. Buncher cavity is the input cavity at which the electrons are bunched and the catcher cavity is the output cavity at which the output is taken but in reflex klystron only one cavity is present where. The passthrough effect, therefore, contributes to the overall operating efficiency of the transmitter. The main difference between two cavity reflex klystron amplifier. Explain the principle of operation of reflex klystron oscillator with a neat diagram.
To understand the operation of a reflex klystron i think you need to start with a basic understanding of a tuned circuit made up from a capacitor c and inductor l. Klystron power supply, klystron tube, isolator, frequency meter, variable attenuator, detector mount, waveguide stand, vswr meter and bnc cable. A collector is present at the end to collect the electrons. Reflex klystron free download as powerpoint presentation. These reflex klystrons continued to occupy a significant position in the testing world, and by the mid80s, reflex klystrons were available up into the 100s of gigahertz. What is the operating principle of reflex klystron.
Microwave and radar engineering presents the essential features of microwave and radar engineering. Electron beams are produced from a source and the cavity klystrons are employed to amplify the signals. To study the characteristics of the reflex klystron tube and to determine its electronic tuning range. The reflex klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron figure 29. Reflex klystron consists of an electron gun, a cathode filament, an anode cavity, and an electrode at the cathode potential. I was an aetm3c in the navy and also remember those local oscillators. 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.
The expected lifetime of a tetrode in uhf service is usually shorter than a klystron ofthesamepowerlevel. Reflex klystron oscillator operation application of. Microwave engineering reflex klystron tutorialspoint. My apologies for the long answer but this is a complicated bit of technology and needs an appreciation of the physics behind it. Reflex klystron is also known as a sutton klystron. The basics how capacitors work working principle duration. After passing through the resonant cavity they are reflected by a negatively charged reflector electrode for another pass through the cavity, where they are then collected. Reflex klystron working, oscillator and applegate diagram engineering funda. Microwave engineering cavity klystron tutorialspoint. Reflex klystron working, oscillator and applegate diagram. Scribd is the worlds largest social reading and publishing site. The microwaves flow into the waveguide, which transports them to the. Now understand the concept of reflex klystron in microwave engineering in details through following questions and answers. When switch on the circuit, the electrons starts emitting from the cathode.
The principle of velocityvariation, first used in heil oscillators, was also used in other microwave amplifying and oscillating tubes. A klystron is a vacuum tube that can be used either as a generator or as an amplifier of power, at microwave frequencies klystron types there are two basic configurations of klystron tubes 1. Microwave and radar engineering book oreilly media. Typicallifetimesof8,000to15,000hourshavebeenreported. The essential elements of klystron are electron beams and cavity resonators. The klystron was the first embodiment of the velocity modulation principle. Reflex klystron article about reflex klystron by the. The reflex klystron contains a reflector plate, referred to as the repeller, instead of the output cavity used in other types of klystrons. Other articles where twocavity klystron is discussed. 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.
The electrons are fired into one end of the tube by an electron gun. 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 velocities of electrons emitted from the cathode are modulated to produce a densitymodulated electron beam. These electrons move at a uniform speed towards the anode until they are attracted by it. Oscillators,in this video we will learn generation of microwave frequencies using reflex klystron oscillator. Additional cavities serve to velocitymodulate the electron beam and produce an increase in the energy available at the output. Avalanche diode construction, working and its applications. In the reflex klystron, the electron beam passes through a single resonant cavity. Reflex klystron vacuum tube electromagnetism scribd.
Lowpower klystrons are used as oscillators in terrestrial microwave relay communications links, while highpower klystrons are used as output tubes. The bunches of electrons excite microwaves in the output cavity of the klystron. Klystron oscillator reflex klystron traveling wave tube magnetron. It was used as a local oscillator in some radar receivers and a modulator in microwave transmitters the 1950s and 1960s, but is now obsolete, replaced by semiconductor microwave devices. This is the reflex klystron oscillator, which will now be described. In this video, i have explained reflex klystron with following points 1. Frequency extension source modules to extend signal generator capability from 50 to 325 ghz. Explain the oscillation mechanism and the electron trajectory concept of magnetron oscillator. 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.
Microwave engineering ece questions and answers page 6. The reflex klystron also known as a sutton tube after one of its inventors, robert sutton was a low power klystron tube with a single cavity, which functioned as an oscillator. Klystron and microwave department capabilities and xband. Reflex klystron oscillator pdf source of an electronbeam and the radiofrequency por tion of the klystron is independent of the electron source. Cavity of a repeller klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron repeller klystron. An avalanche diode is a one kind of diode that is designed to experience an avalanche breakdown at a particular reverse bias voltage. F input signal to the buncher cavity with the help of loop coupling. The reflex klystron oscillator is a lowpower, lowefficiency microwave oscillator, illustrated schematically in figure 118.
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. The reflex klystron makes use of velocity modulation to transform a continuous electron beam into. The whole set up is as shown in the following figure. This article discusses about a brief information about the construction and working of an avalanche diode. With the applegate diagram, describe the mechanism of operation of two cavity klystron amplifier. What is the operating frequency and power output of a. Multi cavity klystron two cavity klystronused as lowpower. The bunching cavities regulate the speed of the electrons so that they arrive in bunches at the output cavity. It focuses on the needs of students who take up the subject at undergraduate and postgraduate levels of electronics and communications engineering courses. Slow wave structures are also otype but have nonresonant periodic structures for electron interactions. What are the modes that exist in a reflex klystron. Since all intermediate cavities in a multicavity klystron operate in the same manner, a.
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