1、APPLICATION NOTES ON PULSE MAGNETRONS FORMULATED BY JEDEC ELECTRON TUBE COUNCIL JEDEC PUBLICATION NO. 42 PRICE $2.00 EIA TEPY2 b3 W 3234b00 0008797 T 9 . This material was prepared by JT-13.1 Subcommittee on Magnetrons and represents the thoughts of industry repre- sentatives of magnetron manufactur
2、ers. Considerable material in this document was found in the WADC Technical Report 58-446 entitled “Techniques for Application of Electron Tubes in Military Equipment“. The committee hopes this information will be useful to users of magnetrons and especially system designers planning to employ magne
3、trons. Published by ELECTRONIC INDUSTRIES ASSOCIATION Eq$neering Department 11 WEST Mnd STREEX, NEW YO= 36, Ne Y. 1 EIA TEP42 b3 3234b00 0008798 I W SECTION 1.1 1.2 1.3 1d-t TABLE OF CONTENTS TITLE INTRODUCTION (Definition, Description, General Cons truc t i on) MAGNETRON TEST SPECIFICATIONS (Notes
4、about types of tests) ESSENTIAL TUBE INFORMATION (Needed by Tube Manufacturers) 1.3.2 Primary Magnetron Properties 1.3.3 Type of Environment-Secondary Magnetron Properties 1.3.4 Environmental Conditions und.er which the tube must operate 1.3.10 Electrical 1.3.41 1.3.49 1.3.61 EFFECT 1.4.1 1.4.24 1,4
5、.27 1.4.30 Mechanical Thermal Magnet i c OF THE SYSTEM ON THE TUBE Electrical Mechanical Thermal Measurements of System and Tubes as a Unit PAGE - 1 3 7 7 7 8 9 16 17 19 20 20 24 25 25 EIA TEP42 63 W 3234600 0008799 3 = SECTION le1 - INTRODUCTION 1.1.1 DEFINITION AND FUNCTION OF THE TUBE . 1.1.2 Mag
6、netrons are defined as :* electron tubes “characterized by the interaction of electrons with the electric.field of a to produce a-.e power output.“ This type of tube is often used - when there is need for a device that will generate high power *t at microwave frequencies, as, for example, in the tra
7、nsmitter of a microwave radar system. Although such a transmitter may operate only in very short pulses and at a low duty factor, the peak power required during this operation may be very .high. For such applications, the magnetron-type oscillator is well suited. - q circuit element in crossed stead
8、y electric and magnetic fields 1.1.3 The choice of transmitter tube for a radar system under design largely influences the ultimate capability of that system. It determines the peak and average power available, the pulse shape, the spectral purity that can be achieved, and. many other of the limitin
9、g characteristics of the system. It does not, however, determine.whether or not, nor to what extent, these limiting features are actually achieved. To obtain the desired reliability in performance of a system being designed, it is necessary not only that a tube with the required inherent capability
10、be chosen, but also that the system be so designed and operated that this capability can be realized, O 1-.1,4 A magnetron is an extremely nonlinear device, its character- istics being functionally dependent on the instantaneous values of the imposed cond.itions, It is responsive to many phenomena w
11、hich characterize its electrical and mechanical environment, some of the relations between response and stimulus being quite subtle. Some of the stimuli have in fact not yet been firmly kdentified, and ther-efore all cause and effect relationships cannot be precisely defined. Al- though magnetrons o
12、f many different designs have been used with considerable success, the designer incorporating these into systems being designed to meet new requirements must relate all available knowledge of their properties to his equipment requirements if he is to avoid the many possible pitfalls. c 1.15 DESCRIPT
13、ION AND GENERAL CONSTRUCTION OF TUBE 1.1.6 Structurally, a magnetron is a vacuum diode on which a magnetic field is imposed. The genera of magnetrons to be discussed. here, utilize a cylind.rica1 cath0d.e coaxial with an annular anode in whic,h a number of resonant cavities are . formed. Electrons e
14、mitted by the cathode move in the inter- action space between cath0d.e and. anode under the combined O %IRE Standards on Electron Tubes: Definitions of Terms, 1957, (57IRET.S2), Proc. IRE, 524 983-3.010(1957) e - 1 . EIA TEP42 63 W 3234b00 0008800 b W influence of the radLa1 d-c electric field and a
15、n axial, ex- ternally supplied., static magnetic field Unlike electron tube types of more general applicability, such as triodes and tetrodes, the magnetron is a complete energy-converting package, requiring only a power supply, usually direct current, and a load to absorb the r-f output. With most
16、lower-frequency tube types, the design of the associated, circuitry is largely under the control of the circuit designer. The magnetron, like certain other microwave tubes providing in one package a source of electrons, a means of influencing their motion, an electromagnetic resonabor, an interactio
17、n mechanism for con- verting d.-c power to r-f power, and a means for coupling the r-f power out, removes many details of the overall circuitry design of a magnetron system from the reach of the circuit designer. EIA TEP42 b3 3234600 0008801 = SECTION L2 MAGNETRON TEST SPECIFICATION 1.2.1 Magnetron
18、Specifications are commonly published in the form of absolute maximum and minimum ratings, simultaneous oper- ating conditions, and test conditions, all in one document. . It has now become customary in military specifications to corresponding entry in the test specification. However, in many other
19、specifications there are absolute ratings not .% exclude from the ratings any item which is not verified by a -. . conforming to this rule, 1.2.2 ABSOLUTE RATINGS 1.2.2.1 The absolute ratings are values which must not be exceeded under any foreseeable combination of measurement errors, line voltage
20、variations, and envkronmental changes, They must, therefore, not be used as design center values. They are limiting values beyond which operation of the tube may be unsatisfactory, and may cause permanent damage to the tube. or equipment. Operation below,.minimum ratings may be just as unsatisfactor
21、y as operatzlonabove maximum ratings. Each parameter is to be considered individually and must not be exceeded even if all other parameters are well within their . limits, The new philosophy which requires testing at the maximum ratings allows simultaneous operation at the maximum ratings provided n
22、o other rating is exceeded, The older O specifications do not allow this condition, 1 2.2.2 I. 1.2.3 1.2.3.1 O 1*283*2 In some cases, absolute ratings represent the limits to which adequate testing has been carried rather than physical limita- tion of the tubeo For special applications it may then b
23、e possible to establish higher limits after suitable tests have been run tio demonstrate satisfactory performance and life. But it must be remembered that extensive and costly testing may be required to establish new limitso In other cases absolute ratings have been arbitrarily established and may o
24、r may not represent permissible opemting points. Absolute ratings are now sometimes d.ivided into i.nd.ependent and de- pendent parameters. This division 5s for convenience in setting out the limits, both of which are equally mandatory. SIMULTANEOUS OPERATING CONDITIONS When published, these represe
25、nt conditions recommended by the manufacturer for normal design center operation of the hbe, It is the responsibility of the equipment designer to ensure that the regulation and measurement errors of the equipment are together less than the margin between the Simultaneous Operating Conditions and th
26、e Absolute Ratings. When two or more sets of Simultaneous Operating Conditions are published, it is generally permissible to find inter- mediate operating cond.itions by linear interpolation between 3 EIA TEP42 63 = 3234b00 0008802 T the published values. Por example, if the Simultaneous Ope rating
27、C0nd.i t i ons inc 1ud.e tP Du ib loo usec o 001 28 a SOO usec o 001 18 a then operation at tp = 2 usec should. be at a nominal current ib = 25.4, a. Operation which is not intermediate between the published conditions should be viewed with suspicion and referred. to,the tube manufacturer, even if n
28、o Absolute Rating appears to be exceeded. Owing to the cost of tubes and life tests, it is impracticable for the manufacturer to establish all possible Simultaneous Operating Conditions, but he frequently has knowled.ge of performance in some regions other than those published. 1.2.3.3 Where excepti
29、onal reliability is required., it will generally be obtained by staying close to a recommended set of Simultaneous Operating Conditions which the manufacturer will furnish if they are not published. as part of the tube ratings. Reliability is not necessarily improved by, say, reducing the input - th
30、is may lead. to moding or to insuf- ficient back bombardment to maintain the cathode temperature, and may thus actually sacrifice reliability. 1.2.4.1 Much of the material describing magnetrons includes the test specifications as well as the ratings. These tests are the purchase specifications by wh
31、ich the tube is made and sold,. It d.oes not follow that the tube can be used. satisfactorily at these levels under field. conditions. These tests will normally be run und.er the ideal conditions of all unspecified parameters, such as VSWR, ambient temperature, pressure, et. Those tests which are de
32、signed to exhibit the ability of the magnetron to operate under a given condition (as opposed to d.efinitive tests, such as frequency, etc,) are normally specified to be run und.er the most severe conditions of operating of the parameters being evaluated The test conditions, therefore, must not be i
33、nterpreted as license to the equipment designer to operate under any but the specified ratings. 1.2.4.2 The basic purpose of a specification for a magnetron is to define or specify its performance or properties under certain conditions, Since the vast majority of magnetrons find their ultimate end u
34、se in government equipment, most specifications for magnetrons follow the format of MIL-E-1. There are now in existence several variations of this format, 1.2,4.3 The newest format has the tests divided into several cate- gories which are discussed as follows: u. 0 O 4 EIA TEP42 b3 W 3234b00 0008803
35、 I = 1.2.4.3.1 Qualification Tests 1.2.4.3.2 1.2.4 3 . 3 1.2.4.3.4 1.2.k.3.5 These tests are performed only at qualification inspection. The intent of these tests is to evaluate those .basic char- acteristics which will remain unchanged unless a very major modification is made in the tube design. Pe
36、riodic Check Tests tween the often inadequate qualification inspectiop Tap Q. . be- ) This is a new group of tests designed to bridge the tests and the often expensive and time consuming design tests. Jn this category may appear tests which in the past may have been either Q.I. or design tests. The
37、tests are performed on three samples-per year and the failure of a sample will give rise to a review of the quality of the tube to determine whether it is inferior in qualiby level to that established during qualification inspection. The basic intent is to eliminate those cases, admittedly few, wher
38、e a parameter or characteristic only tested at the outset of the design has deteriorated to a point where the tube is no longer satisfactory, while at the same time avoiding the necessity to resort to a lot by lot inspec- tion to insure adequate coverage of the specific character- istic. Measurement
39、 Acceptance Tests, Part 1 These are the tests normally shown on older Tube Specifica- tion Sheets (TSS) as Production Tests; They are performed on a lot sampling basis with a combined A.Q.L, These tests cover the critical parameters likely to be affected by day- to-day variations in assembly and pro
40、cessing. Neasurement Acceptance Tests, Part 2 These are the tests normally shown on older TSS as Design, Special Design, and tests with special sampling plans The terms “3esign“, etc., have been droppedand instead the test is indicated by speci.fying the specific A the latter fact is important.as on
41、e of the aims is to eliminate inspection plans other than those in MIL-STD-.lOSA, which with its appendix on Expensive Testing, is considered adequate for all purposes, except those covered by Periodic Check Tests, Degradation Rate Acceptance Tests This group covers those tests in which a deteriorat
42、ion in performance is expected and where the degree of d.eteriora- tion is evaluated, emgo, shock, fatigue test, etc. Such tests are more often than not shown as Quaification tests in present magnetron specification sheets, even though these qualities in the tube can deteriorate over periods of manu
43、facture due to variations in quality of assembly, tool wear, etc. Most of these tests have now been made I EIA TEP42 b3 3234b00 0008804 3 W a Periodic Check Tests, but cases may arise on specific tube types where, due to the special application of the tube, . e.g., missiles, it is considered necessa
44、ry to evaluate such characteristics on a more frequent basis. In such an instance, the tests should be shown under this new category with the A.Q.L. and inspection level. stated, 1.2.4.3.6 Acceptance Life Tests The purpose of an acceptance life test is to check whether a random sample of a lot will
45、have a prescribed life when tested under a set of specified conditions. is high and the sample size is correspondingly high, the statistical method used. usually results in an accurate measure of probable average life of the lot. When the lot . size is small and the sample very small (for example, o
46、ne tube per month), the results may not be necessarily indica- tive of average tube life. However, the specification usually requires that before shipment of a lot is permitted, the selected sample pass a fixed percenta e of life (usually 80%). which must be checked at prescribed intervals. These ma
47、y be either fixed limits or various percentages of initial results d.epending on the application of the tube. When production Various life test end points (LTEPT are specified a 2.2.4.3.7 Special Test and Symbols A dagger (#) symbol is used to d.enote those tests which must be performed after a hold
48、ing period. The holding period. is such that before a tube is tested a sufficient time has elapsed. to weed out tubes which are going gassy or leaking. Where there is more than one such test the order may be indicated in the tube specification. A single asterisk denotes a design test which in the ne
49、wer format is called Measurement Acceptance Test, Part 2. A double asterisk denotes a Qualification Test. 1.3.2 L . 1.363 - EIA TEP42 b3 = 3234b00 0008805 5 = SECTION ln3 ESSENTIAL TUBE INFORMATION The magnetron functions as a self excited microwave oscil- lator, Multicavity magnetrons may be used as pulsed or continuous-wave oscillators at frequencies ranging from approximately 100 to 100,000 Mc. The magnetrons presently under discussion are designed to operate under pulsed con- ditions. system under consideration, the applications engineer must first determine the compatibil
