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Dec. 17, 1946. J. R. FORD ULTRA H IGH FREQUENCY OSCILLATION GENERATOR Filed Feb. 5, 1944 NS1wQKY x-.LQXWG s 2,412,805 2 sheets-sheet 1 \ 9 \ \ \ \ \ \ \ \ \ \ \+ \ ` AIV WN. INVENTOR. BY ÜòH/v 1€. 4Fcuaß Arme/vih Def, A17, 1946. 1R. @RD 2,412,805 lULTRA HIGH FREQUENCY OSCILLATION GENERATOR Filed Feb. 5, 1944 2 Sheets-Sheet 2 CA 73900 E ¿fé/o Amaai T11, a4 mobs 6,9m _ ì INVENTOR. J'aH/l ,9. Paca BY Patented Dec. 17, 1946 2,412,805 UNITED -STATES PATENT OFFICE v,2,412,805 "ULTRA VHIGH FREQUENCY >OSCILLAT'ION GENERATOR John R. Ford, 'Narberth, Pa., assignor to Radio >Corporation of America, -a-corporation of Dela Ware Application vFebruary 5, 1944, Serial No. 521,179 '11 Claims. (Cl. Z50-36) 2 >the wall grid tubular conductor forming the common of the two concentric resonators and 'which Ul reasonably constant output level over its entire V"range, in which both feed back and'frequency of "operation are adjusted simultaneously by Va, single control. megacycles and having 'a fre quency range of vthree or four to one. A further object is to providean ultra high fre employing a “lighthouse tube” llllm'tllbe; -Fig. 3'is a cross-section of the slider arrange ' ment used in both resonators; and Figs. 4, 5 “and 6 show, .diagrammatically only, nators with the sliders in different positions along the lengths of the conductors. The Aaverage po cathode and gan is graphically illustrated for'the different slider positions. Referring `to Fig, 1, there is shown a vacuum >tube I of generally ¿known “lighthouse” -type, ~ rternal Vcircuit elements. VIn practice, the anode, cathode andîgrid electrodes within'the evacuated glassenvelope are positioned 'very close to each other. The anode within the tube’forms one en'd 30 lof 'a metallic cylinder which is connected to `the General Electric type GLI-446 triode. The details - of this “lighthouse” tube are now well known in the art and described in “Electronic Industry,” September, 1944, page 178; and in “Science News The cathode Almere complete description ofthe invention A'follows in conjunction with drawings, wherein: Fig. `1 is a view, »partly yin cross-section, of an ultra high 'frequency oscillator system embodying the principles of the invention; Fig. 2 ` is a perspective view of that portion of, ' for the radio frequency energy flowing between the grid G and conductor 4. The resonator’formed of conductors 3, ll is tunedïby means of slider 6 which is a circular aiîairen gaging the inner surface of 3 and the outer v`sur face of ll. Conductor 4 is hollow and accommo dates in its -interior a hollow "cylindrical lcon 'ductor 5 which >is capacitively coupled at one end 2,412,805 now through the vacuum tube II. In the ar to the anode ring A. The ring A is separated from the conductor 5 by means of a mica spacer 1 which comprises part of a by-pass condenser for radio frequency energy flowing between the anode A and conductor 5. The inner surface of conductor rangement shown in Fig. 4, the oscillator pro duced oscillations at 1500 megacycles, The voltage curve between anode and cathode for the desired mode of oscillation is shown in the l! forms with conductor 5 a concentric line reso nator which is tuned by means of av circular me tallic slider 6' engaging both conductors Il and 5. It should be noted that sliders 6 and 6’ for the different resonators are staggered in position. The two sliders B and Iì' are unicontrolled over links 9 and suitable gearing I5 operated by a handle H. Conductor 4 which forms a common conductor for both resonators is provided at one end with solid line immediately below the circuit arrange ment. The arrangement of Fig. 5 shows the slots 8 completely uncovered by the slider 6 which is now in a position intermediate the ends of the cathode-grid line resonator. In the arrange ment of Fig. 5, the oscillator operated at about 900 megacycles, and the average potential across the slots is shown by the solid curve which slopes more gradually. The dotted line curve shows the voltage that would exist between anode and a plurality of slots 8 for capacitively coupling both resonators together externally of the tube I. Slider 5 is adjustable over the entire length of the slots 8, thus adjusting the effectiveness of cathode for the three-quarter mode of oscilla tion. The slots are positioned at a null for this last voltage. The arrangement of Fig. 5 shows the sliders in the extreme right position, in which location the oscillator operated at about 400 megacycles. It should be noted (Fig. 6) that the these slots. Stated in another way, the slider B is average potential across the slots between anode adjustable from a point near the grid electrode where there would be no capacity coupling and cathode conductors is close to the maximum possible, while the slots are positioned near a through the slots to a point well beyond the slots null for the voltage that would exist between where the slots are completely effective. A grid leak resistor R shunts the condenser 25 anode and cathode for the three-quarter mode of oscillation. In Figs. 5 and 6, the three-quarter formed by the grid ring G and the spaced tubu mode voltage curves are shown dotted, while the lar grid conductor ll. Anode polarizing potential desirable one-quarter voltages are shown in solid is supplied from a source B+ to the anode via a lines. It will be noted that the oscillator pro rod II. High energy loss material, such as iron 30 duced its highest frequency at the one-quarter dust core I2, surrounds the rod II and is in mode when the cathode-grid line resonator is sulated from the tubular anode conductor 5 by shortest, and this is the case with the slots means of an insulation tube II3 which may be covered over by the slider 6. Due to the loading paper. This iron dust core prevents the radio on the resonators by the Vacuum tube, the maxi frequency energy from iiowing along rod II. If mum voltage (EAK) across the slots in the case desired, the iron dust core can be replaced by of Figs. 5 and 6 is a greater fraction of the conducting rubber. The means for keeping the voltage which would be present with no loading vacuum tube I in position has not been shown for the sake of simplifying the drawing, although it by the vacuum tube than that obtainable in the will be understood that such means may include 40 case of Fig. 4. In the practice of the invention, the slots are suitable springs for exerting pressure on the so dimensioned and positioned that feed back at socket of the vacuum tube in the direction of the the desired frequency of oscillations is consider line resonators. ably greater than that for higher frequencies The construction of the slots in the grid line corresponding to higher modes of oscillation. conductor li is illustrated in more detail in Fig. 2. Because of the greater feed back at the desired The construction of the sliders Ii and 6’ is illus trated in Fig. 3 which shows a cross-section of frequencies, the oscillator is constrained to >one of these sliders. The effective length of the generate oscillations at only the desired fre slider 6 is such that it can substantially com quency. The slots are preferably located near pletely cover the slots 8 in the grid line 4 when or at a voltage (anode-cathode) maximum point for the desired mode of oscillation, which point Apositioned. at the extreme left of Fig. 1. In the operation of the oscillator shown in is also a voltage minimum for the undesired mode, Fig. 1, there is always some capacity feed back thus providing a considerable difference in feed between the two resonators 3, II and 4, 5 through back for the two modes. To obtain the Ygreatest the interelectrode capacities of the tube I. The benefits of the invention, this difference in feed slots 8 in tubular conductor ¿i augment this inter- , back between the cases of the desired mode and electrode capacity coupling to a desired degree. the undesired mode should be the greatest pos The slots serve to boost the feed back at the sible, although the benefits of the invention'can lower frequencies of operation and also decreases be achieved so long as there is any appreciably the tendency for the oscillator to produce oscilla greater feed back at the desired mode than at tions at higher modes of oscillation. This is the undesired mode. The slots should be located Ashown more clearly by reference to Figs. 4, 5 and 6 which show the sliders 6 and 6’ in three dif ferent positions along the lengths of the resona tors, and also s‘now the average potential Ear-Ic across the slots between anode and cathode con near the grid electrode, as shown, in order to ductors 5 and 3, respectively. sponding to, let us say, the third‘harmonic of the lowest frequency, then the slots should be posi -tioned near the end of the grid line farthest removed from the vacuum tube, and in this posi tion the greatest feed back will be at the higher mode (third harmonic) of oscillation, and oscilla tion will take place only at the higher mode. The exact position of the slots and their exact With an oscillator of the type shown in Fig. 1 operating over a frequency range from 400 mega cycles to 1500 megacycles, the illustration of Fig. 4 shows the arrangement of the sliders 6 at a point near the grid electrode where the slots Il are ineffective to provide capacity coupling there through. The slider 6, it will be seen, covers the slots and shields the resonators from each other. The yonly feed back which exists in this case is obtain a wide range of frequencies by adjusting the position of the sliders. However, if it is de sired to obtain only a single frequency corre dimensions are best determined by experiment *12,412,805 .higher frequencies. Y .sin order to obtain ¿themaximum»eifectfat-fthese -v utput from‘ithe‘oscillator -maybe .taken from »coaxial line M. ~ -.-. ¿probe l.I3rconnectedto‘theiinnerconcluctor»of-a ‘.In -one embodiment successfully Ytried `Yout Vin ` . A fianode, vwhereby 'sa-id last two ¿conductors ¿form ‘mon wall with said .ñrst resonator, said coin ' ` , Ainon wall having ¥a _ plurality ‘of Aslots lthere *feedback between _said two resonators, a'tuning gpr-actice, thetuned'grid-anode Vline resonator-had 'slider forsaid nrst ‘resonator adjustable'in posi a 4surge impedance -of forty '-ohms, 7while the `tion between-.the hollow conductors of said lfirst tuned grid-cathoderesonator'had'atwentyiohm --resonator .fand having such aXial length as 'to ,surge impedance. AThese lines Awere about seven 10 ¿control the .coupling between said resonators :inches long. vThe ~- anode was :byepassed to .the irad-iotfrequenoy anode conductor 5 by a 150g/lf. concentric capacitor `"I‘ egrid was ~connected-by means of an annular spring to the tubular grid> through fsaid slots, 'said :slider -in fone .position iendering `said slots completely ineffective, and „anotherltunine slider for said other resonator. ~` An oscillation generator comprising a vac conductor through an annular three plate `-ca- l5 uum tube having grid, anode and cathode elec pacitor, the annular spring forming the central trades, a concentric line resonator having an `¿plateaof the `capacitor.- ."I'FwdßOS” annular-.mica outer l:hollow conductor coupled -to vsaid :cathode „discs .served as :the >:,dielectrlc. One :disc lwas rand 1an inner ‘hollowf'conductor coupled `to said ¿painted'fa :thinline ofaquadagtomakefai5000 grid, another hollow conductor coaxially rar `„ohm ggridleak. the :grid l'conductor 4 had ïsix V'20 4ranged within `said last conductor'and coupled slots »3/8” -wide :starting Yat fthe ¿grid >condenser to said anode, whereby said last two conductors .and .running l” away from lthe vacuum tube. form `another concentric line resonator having The ‘B+ supply lwas 250 volts positive impressed -a >common wall with said first resonator, said `on conductor Il through .;a ¿5600 o resistor. common lwall having a plurality of slots there ' e osccillator system vhad ‘a frequency `range :35 through .arranged symmetrically around one por „fiom 400 mcfto 1200 inc. on thereof _to enable feed back between said i» Y atis-clailned is: wo resonators, a tuning slider for said nist oscillation generator coinnrising a vac~ resonatoi adlustable in position over the length uum tube >having grid, anode and cathode elec of said resonator for controlling the effective .trodes, sa rc'oncentric line `resonator:coupled be- :l0 ness of said slots, said .slider having-a length .connecting together rthe .inner 'and outer yicon- 40 concentric line resonator having-an outer hollow 1 2 An oscillation generator compmsing a vacuum tube having grid anode and cathode elec- Ycoupled one end forma to said concentric anode, whereby said last two at conductors line reso nator having a common wall with said ñrst tween said grid and cathode, another concentric „o of slots therethrough near the end coupled to any tuned desiredtofrequency at whichwavelength the resonators having such axial length as to control the cou- 5U are be one-quarter long pline slots between saidso resonators Said Slots, electrically said being positioned through and dimensioned of oscillation,is greater than for any higher mode duce a desired frequency of operation, the volt- 55 uum tube having grid, anode and cathode elec age across said slots is appreciably greater for trodes, a concentric line resonator having an the desired frequency than for any other mode outer hollow conductor coupled to said cathode of oscillation. v . An oscillation generator comprising aivac- and an inner hollow conductor coupled to said grid, another hollow conductor coaxially ar uum tube having grid, anode and cathode elec- To ranged within said last conductor and coupled trodes, a concentric line resonator having an outer hollow conductor coupled to saidfcathode to said anode, whereby said last two conductors form another concentric line resonator having "2,412,805 back between said two resonators, a tuning slider for said first resonator being adjustable in posi- -polarizing potential to -said anode, a metallic cy lindrical tuning slider for each of said resona tion between the hollow conductors of said first resonator and having such axial length as to con- tors, the tuning slider for one of said resonators being adjustable in position between the hollow trol the coupling between said resonators through 5 conductors thereof and having such axial length said slots, said slider in one position rendering `said slots completely ineffective, and another tuning slider for said other resonator, a con- as to control the coupling between said resonators through said slots, said sliders being in staggered relation, and unicontrol means for said sliders. ducting rod coaxially arranged within the inl0. An oscillation generator comprising a vac nermost hollow conductor of said anode-grid lo uum tube having grid, anode and cathode elec~ resonator for supplying said anode with anode polarizing potential, and high loss materialk sur- trodes,aconcentric line resonator having an outer -hollow conductor coupled to said cathode -and an inner hollow conductor coupled to said grid, an other hollow conductor coaxially arranged within im said last conductor and coupled to said anode, whereby said last two conductors form another rounding said rod and insulated from said innermost hollow conductor for absorbing radio íre.quencv energytending to flow along said rod. '7. An ultra high frequency oscillation generator comprising a vacuum tube having grid, anconcentric line resonator having a common wall iode and cathode electrodes, a concentric line reswith said ñrst resonator, said common wall hav onator having an outer cylindrical hollow coning a'pluraltiy of slots therethrough near one end -ductor coupled at one end to said cathode and 20 thereof to enable feed back between said two res an inner cylindrical hollow conductor coupled at onators, a tuning slider for said i'lrst resonator the same end to said grid, a conductor coaxially adjustable in position over the length of said res arranged within said last conductor and also couonator for controlling the effectiveness of said pled at one end to said anode, whereby said last slots, said slider having a length which is an ap two conductors form a concentric line resonator 25 preciable fraction of the length of said slots, said having a common wall with said first resonator, slider in one position rendering said slots com said common wall having a plurality oi slots pletely ineiiective, and another _tuning slider for therethrough at one portion to enable feed back said other resonaton'and means for controlling between said resonators, a metallic cylindrical the movement of said sliders simultaneously.v tuning slider for each of said resonators, the tun- 30 ll. An oscillation generator comprising a vac ing slider for one of said resonators being adjustuum tube having grid, anode and cathode elec able in position between the hollow conductors trodes, a concentric line resonator having an out thereof and having such axial length as to con- er hollow conductor coupled at one end to said trol the coupling between said resonators through cathode and an inner hollow conductor coupled said slots, said sliders being in staggered relation, 35 at its adjacent end to said grid, another hollow and unicontrol means for said sliders. conductor coaxially arranged within said last 8. A generator in accordance with claim 6, conductor and coupledat its correspondingly lo characterized in this that said high loss material cated end to said anode, whereby said last two ‘is an iron dust core. ' conductors form another concentric line resona- 9. An ultra high frequency oscillation genera- 40 tor having a common wall with said i’irst resona tor comprising a vacuum tube having grid, antor, said common wall having near its end which ode and cathode electrodes, a concentric line is connected to said vacuum tube a plurality of resonator having an outer cylindrical hollow con- slots therethrough to enable feed back between ductor coupled at one end to said cathode said two resonators, a tuning slider for said first and an inner cylindrical hollow conductor cou- "w resonator adjustable-in position over the length pled at the same end to said grid, another of said resonator for controlling the effectiveness cylindrical hollow conductor coaxially arranged within said last conductor and also coupled at one end to said anode, whereby said last two conductors form a concentric line res- oo of said slots, said slider having a length which is an appreciable fraction of the length of said slots, said slider in one position rendering said slots completely ineffective, and another tuning onator having a common wall with said ñrst res- slider for said other resonator, and means for onator, said common wall having a plurality of controlling the movement of said sliders simul slots therethrough at one portion to enable feed back between said resonators, a conductor within taneously. said innermost hollow conductor for supplying , JOHN R. FORD.