DOCSLIB.ORG

Magnetron Tubes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Magnetron Tubes Magnetron Tubes - Click on images to enlarge. Tyne gives examples of early experiments on tubes where magnetic fields generated by solenoids control the flow of electrons. De Forest and Von Lieben patented some kinds of such electron devices and Moorhead sold the A-P solenoid tube for a while. - Cyclotron type magnetrons In 1921 A. W. Hull described for the first time static characteristics of a device called magnetron (1). Actually the tube was a diode, with a filament in a coaxial cylindrical plate. The plate cylinder was surrounded by a winding, used to generate a magnetic field. The radial electric field and the superimposed magnetic field forced electrons to follow circular orbits before reaching anode. When the magnetic field was increased, radius of the orbits became smaller and smaller until electrons could no longer reach the plate, so causing the cut-off of the anode current. Hull also noted that the tube could sustain self-oscillations in a resonant circuit, when biased near to the border between conduction and cut-off,. Fig. 1 – a) Draft of the Hull original diode. b) Diagram of the experimental circuit. c) Ferranti GRD7 was a didactic tube used to demonstrate the operation of Hull diode. d) 2B23 is a magnetically actuated switch. Click to enlarge. The cylindrical anode magnetron oscillates in the so-called cyclotron mode, as the result of a sinusoidal voltage built up between cathode and anode. It was found that oscillation occurred following the relation λB = constant, where B was the intensity of the magnetic field. It was also noted that the period of oscillations was equal to electron transit time from cathode to anode and back. Since 1924 E. Habann proposed a split anode magnetron design, in order to have more stable oscillations at higher frequencies. In 1936, Cleeton and Williams reached frequency as high as 47 GHz with such a structure. - Negative resistance types The split anode magnetron may also operate in a different mode, not depending upon the transit time, as far as it is small when compared with the period of oscillation. Under the effect of a strong magnetic field, electrons follow spiral trajectories, describing several complete loops and being preferably attracted by the segment having the lower potential. In 1936 G. R. Kilgore succeeded in observing trajectories, made luminous by the introduction in the bulb of some gas to permit ionization. Kilgore obtained efficiency as high as 25% at 600 MHz with 100W input power. General Electric built some split anode fluid-cooled magnetrons, capable of delivering about 150W at frequencies between 15 and 1200 MHz. The four registered types used in radar jammers, 5J29, 5J30, 5J32, 5J33 and ZP-599 were introduced during WWII. They are described in ‘Very High-Frequency Techniques’, Vol. II, Radio Research Laboratory, Harvard University. Fig. 2 – A) Early split anode magnetron. B) Complete oscillator, also showing the magnetic field generating coil, surrounding the glass bulb. C) CW10 is a split anode magnetron used in the mid thirties for UHF experiments of radio-localization. D) To operate at higher frequencies, resonating circuit was moved into the glass bulb in this RCA A-103A, operating at 3 GHz. E) 5J29 was a split anode magnetron manufactured by General Electric capable of generating 150W at 400 to 700 MHz. The tube was fluid-cooled through the hollow anode legs. (Click to enlarge.) The structure shown in figure 2B may also contain more than two anode plates, as in figure 3A. Fig. 3 - A) The draft of an eight-anode interdigital magnetron. Plate tabs all around the cathode sleeve are alternately welded to the two side rings. In the above samples two rods connect the two opposite anode rings to the external resonating circuit. B) A 12-segment British GEC experimental magnetron. GEC made several similar devices, as this 8-segment prototype and CV79. D) The German RD4Ma uses filamentary tungsten cathode. E) In the 3J22 anodes are connected to ring seals to operate within an external cavity. Click on the image to enlarge. Interdigital or squirrel-cage magnetrons are split-anode types with as many rotating spokes as the fingers connected to one of the two side rings. The higher the number of finger pairs, the smoother their operation at low magnetic field. As we will see later in the section dedicated to voltage tunable magnetrons, interdigital structures can also operate without resonating circuit, their output frequency depending only upon the applied anode voltage. - The ‘Turbator’: a split anode design with integral resonator In the forties Brown Boveri was a supplier of high-frequency communication systems based upon available German triodes. The need of operating at higher frequencies, in order to transmit several channels on the same carrier, forced them to move to a split-anode magnetron with integral resonator, in order to obtain the required high spectral purity. A similar solution can be found in the coaxial magnetron, where a vane structure is surrounded by the resonating cavity. Here images of the BBC MD 10/2000 ‘Turbator’ and of a coaxial type, the Litton L-5035. - Microwave multi-cavity magnetrons (Traveling-wave type) Fig. 4 – A) Laboratory multi-cavity magnetron by Alekseroff and Malearoff. B) The first 8-cavity E.1189 prototype made at GEC. B) Sample of early strapped magnetron by the Sayers group at Birmingham. Click to enlarge. In 1934 Samuel at Bell Telephone had proposed multi-cavity structures, forerunners of the high power devices in use since WWII. The multi-cavity magnetron was subsequently investigated in Russia by Alekseroff and Malearoff. Between 1934 and 1935 K. Posthumus at Philips developed a four segment magnetron. Posthumus also left a theoretical treatment of the rotating electron clouds, which gave the relations between the tube geometry, as the number of anode segments, and the intensity of electrical and magnetic fields. In 1937 Herriger and Hülster recognized the phase-focusing by which electrons were synchronized. Nevertheless, until WWII magnetron was just a physic laboratory oddness. Around the late ‘930s, when the war was rapidly approaching, military pushed the search for high power sources at considerably high frequencies to make possible the airborne installation of radar sets. Power obtainable at the time with triodes dropped sharply above a few hundreds megahertz. Much higher frequencies were required both for easier installation of antennas in airplanes and for higher resolution, to detect small targets. Multi-cavity magnetron structures were then investigated in Great Britain as RF power generators at microwave frequencies. - The early high-power multi-cavity magnetron Multi-cavity structures were not new when the first high-power microwave magnetron was assembled by J.T. Randall and H.A.H. Boot at Birmingham University. The relevant departure from the early experimental devices was the use of an external anode block which greatly simplified heat dissipation. The six hole-and-slot prototype, sealed by wax and water-cooled, operated while continuously pumped from 21 February 1940. RF bursts of about 500W were generated at about 3 GHz. GEC was asked to assemble industrialized prototypes, known as E-1188. Six units were built, all with filamentary tungsten cathode and water cooling. Six-cavity anode blocks were machined at Birmingham using a revolver chamber as drilling template. Soon later they were followed by a six-cavity E-1189 design, modified for air-cooled pulsed operation. An annular eight-fin radiator was brazed to the anode to improve cooling. The anode block length and the end spaces were reduced to fit the unit into a standard permanent magnet. The center hole diameter of anode was increased, hosting a thoriated-tungsten spiral wire. Taking advantage of the parallel experience of Gutton at SFR, Paris, a second sample with more efficient indirect-heated oxide-coated cathode was also successfully tried. The No. 2 sample operated very satisfactorily in pulsed operation, giving about 1 kW at 1000 gauss and 12 kW peak output pulses at about 1400 gauss. The design E-1189 was modified again with eight-cavity anode block, to operate efficiently at 1000 gauss in the pole pieces of a standard 6-lbs magnet. The 8-slot design had a larger center hole to accommodate a 10 mm diameter oxide-coated cathode cylinder. Four units were built, presumably from 18 July 1940. Two of them were used to run performance and life tests on the modified design, while the other two units were sealed and serialized as E.1189 No.12 and No 13. Test results are given in this report by Megaw, dated 11 October 1940. A sample believed to be the first one of the four eight-slot prototypes is on display in the collection. See E-1189 prototype for more information. The sample No. 12 was picked up by Bowen on 11 August 1940 and brought to U.S. and Canada by the Tizard Mission. This sample gave origin to the countless magnetron types designed in America and used in radar application through the war and after. The sample No. 13 was used by Megaw to fully characterize the new variant, as reported in his 1946 paper. Fig. 5 – From left: the prototype of the multi-cavity magnetron by Randall and Boot, the six-cavity anode block of early prototypes, and the sample of E1189 S.N. 12, brought to America by the Tizard Mission and now on display at the National Museum of Science and Technology in Ottawa. Click to enlarge. Once in America the sample No.12 was operated at the Bell laboratory in a 1050 gauss magnetic field, giving an astonishing output power estimated in 15 kW at 9.8 cm (*10). This figure was 750 to 1000 times higher than the power the best Western Electric high-frequency triodes could give at the time (*11).
Load more

Recommended publications
  • 5.1 Audio and Video System L T
    5.1 AUDIO AND VIDEO SYSTEM L T P 4 - 4 Unit:- I (22 Periods) Audio System 1.1 Basics of Working Principle, Construction, polar pattern, frequency response & application of Carbon, moving coil, velocity, crystal, condenser & cordless microphones. 1.2 Basics of Working Principle, Construction, polar pattern, frequency response & application of direct radiating & horn Loud Speaker. Basic idea of woofer, tweeter, mid range, multi-speaker system, baffles and enclosures. crossover networks, Speakers column. UNIT: 2 (20 Periods) SOUND RECORDING:- 1- Fundamentals of Sound recording on Disc & magnetic tape. Brief principle of sound recording. Concept of tape transport mechanism 2- Digital sound recording on tape and disc. Brief concept of VCD, DVD and Video Camera. 3- Principle of video recording on CDs and DVDs. Recordable and Rewritable CDs. Idea of pre-amplifier, amplifier and equalizer system, stereo amplifiers. Unit:3 (12 Periods) ACOUSTIC REVERBERATION:- 1- Reverberation of sound. Absorption and Insulation of sound. Acoustics of auditorium sound in enclosures. Absorption coefficient of various acoustic materials. (No mathematical derivations). Unit 04 (10 Periods) VIDEO CAMERA:- 1- Main features, Working principle, Area of application, Identification of various stages and main components, of single tube camera, ENG camera. TEXT BOOKS 1. A. Sharma- Audio Video & TV Engineering- Danpat rai & Sons. 2. Benson & Whitaker - Television and Audio Handbook- McGrawHill Pub. LIST OF PRACTICAL’S 1- Study of different features and Measurement of directivity of various types of microphones and loudspeakers. (Approximate). 2- Draw the frequency response, bass and treble response of stereo amplifier. 3- Channel separation in stereo amplifier and measurement of its distortion. 4- Installation and operation of a stereo system amplifier.
    [Show full text]
  • Numerical Studies and Optimization of Magnetron with Diffraction Output (MDO) Using Particle-In-Cell Simulations
    Old Dominion University ODU Digital Commons Electrical & Computer Engineering Theses & Dissertations Electrical & Computer Engineering Fall 2015 Numerical Studies and Optimization of Magnetron with Diffraction Output (MDO) Using Particle-in-Cell Simulations Alireza Majzoobi Old Dominion University Follow this and additional works at: https://digitalcommons.odu.edu/ece_etds Part of the Electromagnetics and Photonics Commons, and the Physics Commons Recommended Citation Majzoobi, Alireza. "Numerical Studies and Optimization of Magnetron with Diffraction Output (MDO) Using Particle-in-Cell Simulations" (2015). Master of Science (MS), Thesis, Electrical & Computer Engineering, Old Dominion University, DOI: 10.25777/f6se-9e02 https://digitalcommons.odu.edu/ece_etds/1 This Thesis is brought to you for free and open access by the Electrical & Computer Engineering at ODU Digital Commons. It has been accepted for inclusion in Electrical & Computer Engineering Theses & Dissertations by an authorized administrator of ODU Digital Commons. For more information, please contact [email protected]. NUMERICAL STUDIES AND OPTIMIZATION OF MAGNETRON WITH DIFFRACTION OUTPUT (MDO) USING PARTICLE-IN-CELL SIMULATIONS by Alireza Majzoobi B.Sc. September 2007, Sharif University of Technology, Iran M.Sc. October 2011, University of Tehran, Iran A Thesis Submitted to the Faculty of Old Dominion University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE ELECTRICAL AND COMPUTER ENGINEERING OLD DOMINION UNIVERSITY December 2015 Approved by: Ravindra P. Joshi (Director) Linda Vahala (Member) Shu Xiao (Member) ABSTRACT NUMERICAL STUDIES AND OPTIMIZATION OF MAGNETRON WITH DIFFRACTION OUTPUT (MDO) USING PARTICLE-IN-CELL SIMULATIONS Alireza Majzoobi Old Dominion University, 2015 Director: Dr. Ravindra P. Joshi The first magnetron as a vacuum-tube device, capable of generating microwaves, was invented in 1913.
    [Show full text]
  • Design and Simulation of 8-Cavity-Hole- Slot Type Magnetron on Cst-Particle Studio
    DESIGN AND SIMULATION OF 8-CAVITY-HOLE- SLOT TYPE MAGNETRON ON CST-PARTICLE STUDIO A Dissertation Submitted in Partial Fulfillment of the Requirement for the Award of the Degree of MASTER OF ENGINEERING In Wireless Communication Submitted By SALMA KHATOON 801563022 Under Supervision of Dr. Rana Pratap Yadav Assistant professor, ECED ELECTRONICS AND COMMUNICATION ENGINEERING DEPARTMENT THAPAR UNIVERSITY, PATIALA, PUNJAB JULY, 2017 ii ACKNOWLEDGEMENT I would like to express my profound exaltation and gratitude to my mentor Dr. Rana Pratap Yadav for his candidate guidance, constructive propositions and over whelming inspiration in the nurturing work. It has been a blessing for me to spend many opportune moments under the guidance of the perfectionist at the acme of professionalism. The present work is testimony to his activity, inspiration and ardent personal interest, taken by him during the course of his work in its present form. I am also thankful to Dr. Alpana Agarwal, Head of Department, ECED & our P.G coordinator Dr. Ashutosh Kumar Singh Associate Professor. I would like to thank entire faculty members and staff of Electronics and Communication Engineering Department who devoted their valuable time and helped me in all possible ways towards successful completion of this work. I am also grateful to all the friends and colleagues who supported me throughout, I thankful all those who have contributed directly or indirectly to this work. I would like to express my sincere gratitude to all. Salma Khatoon ME (801563022) iii ABSTRACT In wireless communication technologies, three types of modulation have been used in modern radar systems commonly – pulse (as a particular type of amplitude); frequency; and phase modulation respectively.
    [Show full text]
  • A Brief History of Microwave Engineering
    A BRIEF HISTORY OF MICROWAVE ENGINEERING S.N. SINHA PROFESSOR DEPT. OF ELECTRONICS & COMPUTER ENGINEERING IIT ROORKEE Multiple Name Symbol Multiple Name Symbol 100 hertz Hz 101 decahertz daHz 10–1 decihertz dHz 102 hectohertz hHz 10–2 centihertz cHz 103 kilohertz kHz 10–3 millihertz mHz 106 megahertz MHz 10–6 microhertz µHz 109 gigahertz GHz 10–9 nanohertz nHz 1012 terahertz THz 10–12 picohertz pHz 1015 petahertz PHz 10–15 femtohertz fHz 1018 exahertz EHz 10–18 attohertz aHz 1021 zettahertz ZHz 10–21 zeptohertz zHz 1024 yottahertz YHz 10–24 yoctohertz yHz • John Napier, born in 1550 • Developed the theory of John Napier logarithms, in order to eliminate the frustration of hand calculations of division, multiplication, squares, etc. • We use logarithms every day in microwaves when we refer to the decibel • The Neper, a unitless quantity for dealing with ratios, is named after John Napier Laurent Cassegrain • Not much is known about Laurent Cassegrain, a Catholic Priest in Chartre, France, who in 1672 reportedly submitted a manuscript on a new type of reflecting telescope that bears his name. • The Cassegrain antenna is an an adaptation of the telescope • Hans Christian Oersted, one of the leading scientists of the Hans Christian Oersted nineteenth century, played a crucial role in understanding electromagnetism • He showed that electricity and magnetism were related phenomena, a finding that laid the foundation for the theory of electromagnetism and for the research that later created such technologies as radio, television and fiber optics • The unit of magnetic field strength was named the Oersted in his honor.
    [Show full text]
  • The Radio Amateurs Microwave Communications Handbook.Pdf
    1594 THE RADIO AMATEUR'S COM ' · CA 10 S HANDBOOK DAVE INGRAM, K4TWJ THE RADIO AMATEUR'S - MICROWAVE COMMUNICATIONS · HANDBOOK DAVE INGRAM, K4TWJ ITABI TAB BOOKS Inc. Blue Ridge Summit, PA 17214 Other TAB Books by the Author No. 1120 OSCAR: The Ham Radio Satellites No. 1258 Electronics Projects for Hams, SWLs, CSers & Radio Ex­ perimenters No. 1259 Secrets of Ham Radio DXing No. 1474 Video Electronics Technology FIRST EDITION FIRST PRINTING Copyright © 1985 by TAB BOOKS Inc. Printed in the United States of America Reproduction or publication of the content in any manner, without express permission of the publisher, is prohibited. No liability is assumed with respect to the use of the information herein. Library of Congress Cataloging in Publication Data Ingram, Dave. The radio amateur's microwave communications handbook. Includes index. 1. Microwave communication systems-Amateurs' manuals. I. Title. TK9957.154 1985 621.38'0413 85-22184 ISBN 0-8306-0194-5 ISBN 0-8306-0594-0 (pbk.) Contents Acknowledgments v Introduction vi 1 The Amateur 's Microwave Spectrum 1 The Early Days and Gear for Microwaves- The Microwave Spectrum- Microwavesand EME-Microwavesand the Am- ateur Satellite Program 2 Microwave Electronic Theory 17 Electronic Techniques for hf/vhf Ranges- Electronic Tech- niques for Microwaves-Klystron Operation-Magnetron Operation-Gunn Diode Theory 3 Popular Microwave Bands 29 Circuit and Antennas for the 13-cm Band-Designs for 13-cm Equipment 4 Communications Equipment for 1.2 GHz 42 23-cm Band Plan-Available Equipment- 23-cm OX 5
    [Show full text]
  • Theory of Injection Locking and Rapid Start-Up of Magnetrons, and Effects of Manufacturing Errors in Terahertz Traveling Wave Tubes
    Theory of Injection Locking and Rapid Start-Up of Magnetrons, and Effects of Manufacturing Errors in Terahertz Traveling Wave Tubes by Phongphaeth Pengvanich A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Nuclear Engineering and Radiological Sciences) in The University of Michigan 2007 Doctoral Committee: Professor Yue Ying Lau, Chair Professor Ronald M. Gilgenbach Associate Professor Mahta Moghaddam John W. Luginsland, NumerEx © Phongphaeth Pengvanich All rights reserved 2007 For Mom and Dad ii ACKNOWLEDGEMENTS I would like to express my deep gratitude to my advisor, Professor Y. Y. Lau, who has never ceased to inspire and motivate me throughout my graduate student career. Professor Lau not only taught me Plasma Physics, but also showed me how to be a good theoretician and how to be passionate about my work. I can never thank him enough for his continuous guidance and support in the past five years, and I have always considered myself very fortunate to have him as my mentor. Professor Ronald Gilgenbach was the first person who captured my interest in Plasma Physics when I was still an undergraduate. Since then, he has given me many advices and ideas for my work, and has provided me with an opportunity to teach a Plasma laboratory class. I would like to thank him for his tremendous help. I wish to thank Professor Mahta Moghaddam for serving on my dissertation committee, and for her thoughtful comments. I thank Dr. John Luginsland of NumerEx for his continuous advices and updates on the injection locking and the manufacturing error projects.
    [Show full text]
  • Microwave Communications - Mcqs (1- 5
    Microwave Communications - MCQs (1- 5. Rainfall is an important factor for 300) fading of radio waves at frequencies above 1. __________ is the progressive decrease A. 10 GHz of signal strength with increasing B. 100 GHz distance. C. 1 GHz A. Radiation D. 100 MHz B. Attenuation 6. Theoretically electromagnetic radiation C. Modulation field strength varies in inverse proportion D. Propagation to the square of the distance, but when atmospheric attenuation effects and the 2. Calculate the effective earth’s radius if absorption of the terrain are taken into the surface refractivity is 301. account the attenuation can be as high as the inverse _______ power of the distance. A. 8493 km B. 8493 mmi A. Third C. 6370 km B. Fourth D. 6370 mi C. Fifth D. Sixth 3. If k-factor is greater than 1, the array beam is bent 7. What do you call an attenuation that occurs over many different wavelengths A. Away from the earth of the carrier? B. towards the ionosphere, A. Rayleigh fading C. towards the earth B. Rician fading D. towards the outer space C. Wavelength fading 4. the antenna separations (in meters) D. Slow fading required for optimum operation of a space diversity system can be calculated from: 8. Which of the reception problems below that is not due to multipath? A. S = 2λR/L A. Delayed spreading B. S = 3λR/L B. Rayleigh fading C. S = λR/RL C. Random Doppler shift D. S = λR/L D. Slow fading where R = effective earth radius (m) and L = path length (m) 9.
    [Show full text]
  • The Transistor Revolution (Part 1)
    Feature by Dr Bruce Taylor HB9ANY l E-mail: [email protected] t Christmas 1938, working in their small rented garage in Palo Alto, California, two The Transistor enterprising young men Acalled Bill Hewlett and Dave Packard finished designing a novel wide-range Wien bridge VFO. They took pictures of the instrument sitting on the mantelpiece Revolution (Part 1) in their house, made 25 sales brochures and sent them to potential customers. Thus began the electronics company Dr Bruce Taylor HB9ANY describes the invention of the that by 1995 employed over 100,000 people worldwide and generated annual tiny device that changed the course of radio history. sales of $31 billion. The oscillator used fve thermionic valves, the active devices that had been the mainstay of wireless communications for over 25 years. But less than a decade after HP’s frst product went on sale, two engineers working on the other side of the continent at Murray Hill, New Jersey, made an invention that was destined to eclipse the valve and change wireless and electronics forever. On Decem- ber 23rd 1947, John Bardeen and Walter Brattain at Bell Telephone Laboratories (the research arm of AT&T) succeeded in making the device that set in motion a technological revolution beyond their wildest dreams. It consisted of two gold contacts pressed on a pinhead of semi-conductive material on a metallic base. The regular News of Radio item in the 1948 New York Times was far from being a blockbuster column. Relegated to page 46, a short article in the edition of July 1st reported that CBS would be starting two new shows for the summer season, “Mr Tutt” and “Our Miss Brooks”, and that “Waltz Time” would be broadcast for a full hour on three successive Fridays.
    [Show full text]
  • Cavity Magnetron 1 Cavity Magnetron
    Cavity magnetron 1 Cavity magnetron The cavity magnetron is a high-powered vacuum tube that generates microwaves using the interaction of a stream of electrons with a magnetic field. The 'resonant' cavity magnetron variant of the earlier magnetron tube was invented by John Randall and Harry Boot in 1940 at the University of Birmingham, England.[1] The high power of pulses from the cavity magnetron made centimeter-band radar practical, with shorter wavelength radars allowing detection of smaller objects. The compact cavity magnetron tube drastically reduced the size of radar sets[2] so that they could be installed in anti-submarine aircraft[3] and Magnetron with section removed to exhibit the escort ships.[2] At present, cavity magnetrons are commonly used in cavities. The cathode in the center is not visible. The waveguide emitting microwaves is at the left. microwave ovens and in various radar applications.[4] The magnet producing a field parallel to the long axis of the device is not shown. Construction and operation All cavity magnetrons consist of a hot cathode with a high (continuous or pulsed) negative potential created by a high-voltage, direct-current power supply. The cathode is built into the center of an evacuated, lobed, circular chamber. A magnetic field parallel to the filament is imposed by a permanent magnet. The magnetic field causes the electrons, attracted to the (relatively) positive outer part of the chamber, to spiral outward in a circular path rather, a consequence of the Lorentz force. Spaced around the rim of the chamber are cylindrical A similar magnetron with a different section cavities.
    [Show full text]
  • The Development of E1189, the First British Cavity Magnetron
    The development of E1189, the ‘British cavity magnetron’ Abstract: No doubt that the British cavity magnetron originated from the prototype devised at Birmingham by Randall and Boot. What until today has been partially ignored is the subsequent work done by Eric Megaw at GEC, essential to obtain that powerful, versatile and easily reproducible microwave generator that everyone today simply knows as ‘magnetron’. The recent finding of samples and documents coming from the GEC Archives, after the shutdown of the GEC-Marconi, made it possible the full reconstruction of what Megaw really did in those days. Foreword: In 1921 A. W. Hull at General Electric for the first time described static characteristics of a device called magnetron. Actually the tube was a diode, with filament coaxial to the cylindrical plate. The bulb was surrounded by a winding, used to generate a magnetic field. The radial electric field and the superimposed magnetic field forced electrons to follow curved orbits before reaching anode. Hull noted that, gradually increasing the magnetic field, radius of the orbits became smaller and smaller, until electrons could no longer reach the plate, so causing the cut-off of the anode current. Hull also noted that, when biased near to the border between conduction and cut-off, the tube could sustain self-oscillations in a resonant circuit. Fig. 1 – a) Draft of the Hull original diode. b) Diagram of the experimental circuit. c) Ferranti GRD7 was a didactic tube used to demonstrate the operation of Hull diode. d) 2B23 is a magnetically actuated switch. The cylindrical anode magnetron oscillated in the so-called cyclotron mode, as result of a sinusoidal voltage built up between cathode and anode.
    [Show full text]
  • Microwave Engineering
    BVRIT HYDERABAD College of Engineering for Women Department of Electronics and Communication Engineering Hand Out Subject Name: Microwave Engineering Prepared by (Faculty(s) Name): Ms. Rama Lakshmi G, ECE Year and Sem, Department: IV Year- I Sem, ECE Unit – I: Microwave Transmission Lines-I and Rectangular Guides Important Points / Definitions: Electromagnetic waves are oscillations that propagate through free space with a velocity of light The electric and magnetic fields vary with time and are governed by Maxwell‟s equation. The transmission line theory is strictly applicable to those conductors which have go and return path i.e. those which can support a TEM waves. Microwaves are electromagnetic waves whose frequencies range from 1GHz to 1000 GHz. Microwaves propagate through various microwave circuits, components and devices that acts as section of microwave transmission lines. These devices are known as waveguides. The coaxial transmission line is the most widely used for high frequency applications. The dominant mode in a coaxial line is the TEM mode although higher modes do exist at high frequencies. The mode having the highest cut off wavelength is known as dominant mode of the waveguide and all other modes are called higher mode. The lowest order higher order modes in coaxial cables are TE11 and TM01. Dominant mode transmission is almost always low-loss and distortion less transmission. Strip lines are modifications over two wire transmission line and coaxial line. A hollow metallic tube of uniform cross section for transmitting electromagnetic waves by successive reflections form the inner walls of the tubes is called a waveguide. The parallel strip line is similar to a two conductor transmission line because it consists of two perfect conductors with dielectric in between.
    [Show full text]
  • The Cavity Magnetron*
    THE CAVITY MAGNETRON* By H. A. H. BOOT, Ph.D.,I and J. T. RANDALL, D.Sc., F.R.S.,T Associate Member. (The paper was frst received l5th February, and in revised form 3rd July, 1946.) ST'MMARY mid-plane sectional drawing (at right angles to the cylindrical This paper gives an account of the discovery of the cavity magnetron axis) ofFigs. 1(a) and 1(ô). The general type ofdesign illustrated in the University of Birmingham by the authors, and of subsequent developments in that laboratory including the discovery by Sayers of what is now known as strapping. From October, 1939, to August, 1941, the work was carried out by the authors who, from June, 1940, received much technical help from S. M. Duke. Sayers began work on the magnetron in the summer of 1941 and his ideas on modes led almost immediately to the introduction of straps. Sayers's detailed work will later be the subject of a separate paper. (1) INTRODUCTION (à) As the group of workers originally engaged on the production Fig. l.-End view of resorlator systens. of centimetre waves in the Physics Department of the Type (a) is based on a Hertzian dipole while (à) is based on a short{ircuited quarter University wave Iine, of Birmingham has been gradually disbanded since the autumn of 1943, it may not be inapt to recall the inception of this work in Fig. 1(a) was the first to be used in Birmingham, and a and the.early ideas concerning the magnetron. Initially, under photograph of one of the first six anode blocks to be made is Oliphant, a considerable attempt was made by Sayers and others given in Fig.
    [Show full text]