US2008690A - Oscillator system - Google Patents

Description

July 23, 1935.

J. B. DOW

OSCILLATOR SYSTEM Filed July 1, 1932 INVENTOR tlnni nys B. D0 w.

ATTORNEY Patented July 23, 1935 OSCILLATOR SYSTEM 7 Jennings B. Dow-,' Washington, LC assignor to 7 Radio Corporationof America, a corporation of Delaware Application July '1, :19s2 ;seria1-No. accuse f9 cl ims. (erase -self.

(Granted under "the" act of March 3, 1883, as

' amended April 3'0, 1928; 370 0. G. 757).; V

invention relates broadly to oscillatorsystemsand more particularly to; a'balanced o'scil-' latorsy'ste'm.

.....On'e-of the objects of my invention is to provide. a balanced bridge type of oscillation generator; A ,3 Another object of my invention'is to provide abalancedoscillatorin which the frequency of oscillation is relatively: free from the influence of external circuits which may be coupled to the system. r I vA still further object of my invention is toiprov-ide'a balanced bridge type of oscillation gen erator, the output portion of which forms noessential part of the oscillation generating means. Other: and further objects of my invention will be understood from thespecificationhereinductance, capacity and resistance are in part,

transferred in the form of eguivalences into the oscillation generator. This transfer 'of equivalencesresults in changing, those electrical constantsi'of the system which determine the frequency of oscillation and thus'makes the frequency o'f'oscillation' a function of the load. A

present invention -covers a method of arranging the oscillation generator and its output work circuit in a balanced or bridge arrange ment so thatthe'efiect of variable load conditions wilt-be reduced.

- I 'In' th'e circuit of- Fig. 1, reference character lin- 'di'cates an electron tube having" a cathode 2, a contro1 grid-3',an inner anode 4 and an outer anode 5} The tube maybe ofthe conventional dour-clement type or it may be of a type especially designedfor this kind of service. The cathode 2 is heatedby battery' 8-and isconnected to the'rotor of a conventional split Variable con- -denser: 'l-.--Obvious1y two or more condensers in series with the center connection maderto the cathode might Just as" well be employed. 2 The are sectionsof the'fcondenser 'l are connected to the opposite ends of .an inductance-and together iorm resonant circuit 9. One end oflthe resonant circuit 9 is connected "through a blocking condenser IO vtocontrol grid 3. 'A grid leak ll connectsthe control gridand cathode for biasing the former at the desired potential; The opposite end of resonant circuit 9 connects to inner anode A which is supplied at the proper positive potential withwrespect to cathode 2 b'ylits i connection to anode battery. .l2 through chokeicoil l3.

The circuit thus farjdescribed is theiamiliar Colpitts oscillator. and" with such a circuit, .it is conventional practicertoi connect or couple the load to resonant circuit 9.- In the particular fcrmof my invention: shown in Fig. 1,,I do; not do this in the'conventional manner but instead, I

derive energy from. the. oscillator through the medium of an output circuit connected between outer anode'5 and a point along inductance 8. The outer anode 5 is .maintainediat the desired potential with respecttocathode 2 by its connece tion to anode battery .52 through choke coil i l. The output circuit comprises blocking condenser l5 and resonant circuit, H5 in series connection between outer ancdeft and'ta'p connection ll :alonginductance '8. Resonant circuit. It consists of inducta'nceul'S an'dvariable capacity IS in parallel; :Reson'ant circuit. l6 may be tuned to the samesfrequency as resonantcir'cuit 9.01" it may be tuned to al harmonically related one.

7 Resonant circuit lfi' may bereplaced by any other: form of impedance such as an inductance or aresista'nce; Choke coils;rl3 and I4 mayalso :be-repla'ced byothenhigh impedancesl such as resistances. The'1remainder-0f the circuit of Fig. comprises:balancing condenser 20 connected-betwe'encontrolgrid 3 and outer anode 5. The 'functionof balancing" condenser 20 will be madeicle'ar in what follows. i

Fig. z shows in simplified formthe equivalent high.frequency portion'of the circuit of Fig. 1. .All partsof Fig. 1- whichiare not essential'to an understanding of the 'principles of my invention are omitted from the :circuit of Fig. 2. In the circuit oi Fig. 2-:the cathode .2, control grid 3, inner anode Land'outer. anode 5. are indicated attlie apexes of the bridge. Reference character vCa.idenotesithatportion-of condenser l of Fig.

1.which isbe'tween control grid 3 andcathode 2. The grid to cathode intereleme'nt capacity is'con-- z'si'deredxlumpe'dwithithat of capacity'cv'a. Reference character Cisdenotes that portionof con.- denser jl of Fig; lwhich is betweencathode 2 and inner anode 4.4 Theinterelement capacity between cathode and inneranode. is considered lumped with, capacity Cit. Inductance 8 isbetween .control-grid 3- -andg inner anode 4 as in Fig.

the interelement capacity between inner anode 4 and outer anode 5 whereas C20 denotes the capacity of balancing condenser 20 of Fig. l which is connected between control grid 3 and outer anode 5. Resonant circuit l6 which comprises the high frequency portion of the output circuit is connected between outer anode 5 and a point along inductance 8. Now, C; is fixed by the design of tube employed, and the ratio Cva/Cn, may be fixed by the design of condenser 1. Therefore if- C20 is so chosen that,

V zo C71? V- then, neglecting electron flow, an alternating potential across inductanceB will not produce a potential between cathode 2 and outer anode 5 nor will an alternating potential be produced across resonant circuitlO if tap ll on inductance 3 is so placed that it suitably divides the impedance of'inductance. 8. This is equivalent to stating that the generated oscillations, neglecting electron flow, are not coupledtothe output circuit l6 through the interelement capacities of the tube.

From Equation (1) it may be deduced that any suitable impedances Z may be employed in place of the capacities C. Using the same subscripts as indicated in Equation (1) it will then be seen that the following generic equation is to be satisficd by the conditions under which the system my invention may be operated:

Further consideration will show that the oscillation generating portion of the circuit acts so as to satisfy the conditions required for oscillation, for determining the frequency and for causing pulses of electrons tobe projected through the grid-like structure of inner anode 4 to the outer anode 5. The pulses of electrons impinging upon outer anode 5 cause correspondingva'riations-in potential across choke coil. l4 and coin.- cidentally,.across resonant. circuit Hi to which the desired load may. be coupled.

As previously stated, the oscillation generating portion of the circuitof Fig. 1 is of the Colpitts type. Obviously. any other form of oscillator might have been employed with equal facility, for example, had the Hartley type been chosen Equation (2) would still hold; The only difference in that case would be that branches C78 and 07b of Fig. 2 would be inductive whereas inductance 8 would be replaced by a capacity branch.

My invention comprises meansxfor balancing out the effect of interelement impedance which may exist betweenan auxiliary element and those elements of an oscillation generator which may be positioned within the same electron tube. It will be noted that Equations (1) and (2) are inde pendent 'of any steady potentials which may exist or be impressed in the circuit. It is also apparent from the equations that they are independent of the frequency and amplitude of the existing alternating potentials.

Ihave found the oscillator circuit of my invention highly stable in its operation and while I have described it in certain of its preferred embodiments I desire it to be understood that modifications may be made and that no limitations are intended other than are imposed by the scope of the appended claims.

The invention described herein may be manufacturedand used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

' What I claim asnew and desire to secure by Letters Patent of the United States is as follows: -1. An oscillation generator comprising an electron tube having a cathode element, a control grid element, and a grid-like anode element, and branch circuits connecting said elements, in combinationwith a second anode element within said tube and a branch circuit interconnecting said second anode element with said control grid, the

characteristics of said combination being such that the impedance of the branch between said control grid element and said second anode element is substantially equal to the product. of the interelement impedance between said'grid-like anodeelement and said second anodes element, and that of the; branch circuit between said cathode element and said control grid'element divided by the impedance of the branch circuit between said cathode element and said grid-like anode element, and inaddition to said combination an output circuit connecting said second anode element with a point along the branch circuit between said control grid element and said grid like anode element.

, 2. An electron tube having a cathode, a con trol grid and a grid-like anode, circuits interconnecting said electrodes wherewith an oscillation generator is provided, a second anode within said tube having a reactive connection with said con trol grid, and ,an output circuit disposed between said second anode and a point along that one of said oscillation generator circuits which inter-.- connects the control grid and the grid-like anode, the arrangement being such that the alternating potential produced upon said. second "anode through the interelement capacity existent be.-

tween said anodes is substantially equal to and opposite in phase to that induced upon said second anode through said reactive connection.

the frequency generated, means including a resonant circuit for operatively associating said in-.-

put and output circuits with oneanother so. as'to produce oscillations, a resonant ;circuit interconnecting said fourth electrode and a point along the aforesaid resonant circuit, and means whereby the effect of interelement capacities in producing high frequency potentials ,upon said fourth electrode is substantially neutralized.

4. An oscillationgeneratorincluding an ,electron tuberhaving a cathode element, acontrolgrid element and a: grid like anode element, and branch circuits connecting said elements, in com.- bination with. an auxiliary element within said tube and a branch circuit interconnecting said auxiliary element with said control? grid, the characteristics of-v said combination-being :such

that the impedance of the branch between said control grid element and said auxiliary element is substantially equal to the product of the interelement impedance between said grid-like anode element and said auxiliary element, and that of the branch circuit between said cathode element and said. control grid element, divided by the impedance of the branch circuit between said cathode element and said grid-like anode element, and in addition to said combination, a resonant circuit disposed in series connection between said auxiliary element and a point along the branch circuit between said control grid element and said grid-like anode element.

5. An electron tube having a cathode, a control grid and grid-like anode, circuits interconnecting said electrodes wherein an oscillation generator is provided, an auxiliary electrode within said tube having a reactive connection with said control grid, and a work circuit disposed between said auxiliary electrode and a point along that one of said oscillation generator circuits which interconnects the control grid and the grid-like anode, the arrangement being such that the alternating potential produced upon said auxiliary electrode through the interelement capacity existent between said grid-like anode and said auxiliary electrode is substantially equal to and opposite in phase to that induced upon said auxiliary electrode through said reactive connection.

6. In a device for generating oscillations, an

electron tube at least three electrodes of which in combination with input and output circuits therefor are adapted to generate oscillations, an auxiliary electrode within said tube, means including a resonant circuit for operatively associating said input and output circuits with one another so as to produce oscillations, a-second resonant circuit disposed between saidauxiliary electrode and a point along the aforesaid resonant circuit, and means whereby the effect of interelement capacities in producing high frequency potentials upon auxiliary electrode is substantially neutralized.

'7. In a device for generating oscillations, an electron tube at least three electrodes of which in combination with interconnecting circuits therefor are adapted to generate oscillations, an auxiliary electrode within said tube and an additional circuit connecting said auxiliary electrode with a point along one of said first mentioned circuits, and means whereby the effect of interelement capacities in producing high frequency potentials upon said auxiliary electrode is substantially neutralized.

8. A device for generating oscillations in accordance with claim '7 wherein said additional

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