Reflex klystron oscillators have been built which give useful output at frequencies greater than 100,000 mc, or 100 gc. Klystron types presentday klystrons fall into three categories. Avalanche diode construction, working and its applications. Familiarity with the working of drive mechanism of a tape recorder. As shown electron beam is generated by electron gun which passes through the space between input cavity i. Intensive work, however, has led to products that offer higher output powers and extended operating lifetime, while retaining the benefits inherent in tetrode devices. Define reflex klystrons, some characteristics and applications. To study the characteristics of the reflex klystron tube and to determine its electronic tuning range.
The microwaves flow into the waveguide, which transports them to the. Reflex klystron working, oscillator and applegate diagram. In the reflex klystron, the electron beam passes through a single resonant cavity. 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 bunching process as well as output taken. 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. Normally we use separate components in devices such as radio transmitters and receivers but as frequencies increase the two components merge into one structure and become a. Other articles where twocavity klystron is discussed. Slow wave structures are also otype but have nonresonant periodic structures for electron interactions. The expected lifetime of a tetrode in uhf service is usually shorter than a klystron ofthesamepowerlevel. Klystron works on the principle of velocity modulation of electrons. 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. This article discusses about a brief information about the construction and working of an avalanche diode.
A small hole in the broad wall of the waveguide is provided, through which output coupling pin of klystron tube enters into the waveguide. Reflex klystron working free download as powerpoint presentation. Calculate optimum repeller space, rf power output, efficiency and the bandwidth over. Explain the principle of operation of reflex klystron oscillator with a neat diagram. Microwave engineering ece questions and answers page 6. 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. A klystron is a specialized linearbeam vacuum tube, invented in 1937 by american electrical. The reflex klystron contains a reflector plate, referred to as the repeller, instead of the output cavity used in other types of klystrons. When there is no signal voltage on the pair of sockets 6, then, with button 2. View and download powerpoint presentations on reflex klystron ppt. 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. Electron beams are produced from a source and the cavity klystrons are employed to amplify the signals. 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.
Reflex klystron oscillator pdf source of an electronbeam and the radiofrequency por tion of the klystron is independent of the electron source. Microwave tubes reflex klystron mechanically, reflex oscillator designed for use as a cw power source over a frequency. The main difference between two cavity reflex klystron amplifier. Oscillators,in this video we will learn generation of microwave frequencies using reflex klystron oscillator. The bunching parameters measure deviations of the multiplicity distribution from a poisson distribution. 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. A collector is present at the end to collect the electrons. Sep 27, 2017 in this video, i have explained reflex klystron with following points 1. A reflex klystron is an obsolete type in which the electron beam was reflected back along its path by a high potential electrode, used as an oscillator. Klystron for high gradient accelerator research, in aip conf. The passthrough effect, therefore, contributes to the overall operating efficiency of the transmitter. Product description a small hole in the broad wall of the waveguide is provided, through which output coupling pin of klystron tube enters into the waveguide.
Reflex klystron telecommunications engineering mechanics. The klystron was the first embodiment of the velocity modulation principle. The reflex klystron oscillator is a lowpower, lowefficiency microwave oscillator, illustrated schematically in figure 118. Lowpower klystrons are used as oscillators in terrestrial microwave relay. Optimization of micromachined reflex klystrons for operation at terahertz frequencies. 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. Reflex klystron consists of an electron gun, a cathode filament, an anode cavity, and an electrode at the cathode potential. Moreover it uses repeller inplace of catcher cavity. Reflex klystron the analysis of a reflex klystron is similar to that of a twocavity klystron to some extent and is subjected to the following approximations. What is the basic principle involved in microwave tubes.
Why is pulse modulation required in reflex klystron. It is possible to produce oscillations in a klystron device which has only one cavity, through which electrons pass twice. Yes, they had a bellows that was externally adjusted to cause the separation between grids that coupled to a resonant chamber as reflex. With the applegate diagram, describe the mechanism of operation of two cavity klystron amplifier. What is the difference between velocity modulation. 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. Mar 24, 2016 working of reflex klystron oscillator. In klystron strong electrostatic fields are required for its operation efficiently. This hole is exactly located in the center of broad wall because the. The multi cavity klystron consist of a glass envelope in which there is an electron gun composed of heater and cathode.
Twystron is a hybrid amplifier which uses a combination of klystron and slow wave structures. 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 electron beam is accelerated towards the anode cavity. A nanoklystron consists of a highdensity cathode, bunching tube, rf resonator, shaped repeller and rf. Klystron multi cavity klystron, reflex klystron, working. Microwave engineering reflex klystron tutorialspoint. In this klystron, a single pair of grids does the functions of both the buncher and the catcher grids. The twocavity oscillator klystron normally generates more power than the reflex klystrontypically watts of output rather than milliwatts. In this video, i have explained reflex klystron with following points 1. Explain about construction and working principle of magnetron oscillator 47 a diode which produces negative resistance effect is normally used as low power oscillator at microwave frequencies in transmitter and local oscillator in receiver.
Typicallifetimesof8,000to15,000hourshavebeenreported. The name klystron comes from the greek verb klyzo referring to the action of waves breaking against a shore, and the suffix. The principle of velocityvariation, first used in heil oscillators, was also used in other microwave amplifying and oscillating tubes. When switch on the circuit, the electrons starts emitting from the cathode. 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. Microwave engineering cavity klystron tutorialspoint. Fault finding and preventive maintenance in tape recorders. The bunching cavities regulate the speed of the electrons so that they arrive in bunches at the output cavity. I was an aetm3c in the navy and also remember those local oscillators. Explain the working of a twt amplifier with neat sketch. F input signal to the buncher cavity with the help of loop coupling. Reflex klystron used as a lowpower microwave oscillator 2. The essential elements of klystron are electron beams and cavity resonators.
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. Klystron power supply, klystron tube, isolator, frequency meter, variable attenuator, detector mount, waveguide stand, vswr meter and bnc cable. Wafer application of reflex klystron bendix reflex klystron vacuum tube bendix ka band klystron klystron tube ka band reflex klystron text. Explain the oscillation mechanism and the electron trajectory concept of magnetron oscillator. An avalanche diode is a one kind of diode that is designed to experience an avalanche breakdown at a particular reverse bias voltage. Jan 16, 2017 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. Since there is no reflector, only one highvoltage supply is required. The bunches of electrons excite microwaves in the output cavity of the klystron. The whole set up is as shown in the following figure. In statistics as applied in particular in particle physics, when fluctuations of some observables are measured, it is convenient to transform the multiplicity distribution to the bunching parameters. The electrons are fired into one end of the tube by an electron gun.
My apologies for the long answer but this is a complicated bit of technology and needs an appreciation of the physics behind it. The operation of reflex klystron is understood by some assumptions. Reflex klystron article about reflex klystron by the. A reflex klystron is operated at 5 ghz with dc beam voltage v, beam current 20ma, repeller space l cm for 3 1 4 mode, cavity gap 2mm, repeller voltage 500v. How reflex klystron works electrical engineering stack exchange.
A reflex klystron is an obsolete type in which the electron beam was reflected back along its path by a. Multi cavity klystron two cavity klystron used as lowpower. Multi cavity klystron two cavity klystronused as lowpower. The difference between reflex and twomulti cavity klystron is that, reflex klystron uses single cavity for modulationdemodulation. Another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron figure 29. These electrons move at a uniform speed towards the anode until they are attracted by it. The reflex klystron makes use of velocity modulation to transform a continuous electron beam into. Frequency extension source modules to extend signal generator capability from 50 to 325 ghz. Pdf optimization of micromachined reflex klystrons for operation.
Article pdf available in ieee transactions on microwave theory and. Reflex klystron article about reflex klystron by the free. Cavity of a repeller klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron repeller klystron. The electron gun emits the electron beam, which passes through the gap in the anode cavity. The paramount o type tube is the two cavity klystron followed by the reflex klystron. This is the reflex klystron oscillator, which will now be described.
Cavity grids and repeller are plane and parallel, and also very large in extent. The reflex klystron another tube based on velocity modulation, and used to generate microwave energy, is the reflex klystron figure 29. Their work was preceded by the description of velocity modulation by a. Reflex klystron oscillator operation application of. Three power sources are required for reflex klystron operation. What is a klystron amplifier, types, differences and their applications. Electrons are not intercepted by the cavity anode grid. Klystron oscillator reflex klystron traveling wave tube magnetron.
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