US2740848A

US2740848A - Polygonal multiple tube system

Info

Publication number: US2740848A
Application number: US402112A
Authority: US
Inventors: Charles J Starner; Franklin E Talmage
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1954-01-04
Filing date: 1954-01-04
Publication date: 1956-04-03
Anticipated expiration: 1973-04-03
Also published as: BE534619A; GB766612A; DE961812C; FR1118792A; NL193734A; NL91521C

Description

April 3, 1956 c. J. STARNER ETAL 2,740,848

POLYGONAL MULTIPLE TUBE SYSTEM Filed Jan. 4, 1954 3 Sheets-Sheet 1 Z? I I var/0r 7 i 73 fig -1 5 I I 7 (72 t ATTOR NE 1 April 3, 1956 c. J. STARNER ETAL 2,740,848

POLYGONAL MULTIPLE TUBE SYSTEM Filed Jan. 4, 1954 3 Sheets-Sheet 2 INVENTORS CHAIFLES Smxwzz FKA/VKl/IV E, 721M465 ATTORNEY April 1956 c. J. STARNER ETAL 2,740,848

POLYGONAL MULTIPLE TUBE SYSTEM Filed Jan. 4, 1954 3 Sheets-Sheet 3 INVENTORS cHA/FZES J Saw/v54; f /FANKu/v E. ZZLMAGE MW-M 11 TTOR NE Y 2,740,848 POLYGONAL MULTIPLE TUBE SYSTEM Charles J. Stamer, Haddonfield, and Franklin E.Talmage, Westmout, N. 1., assignors to Radio Corporation of America, a corporation of Delaware Application January 4, 1954, Serial No. 402,112 25 Claims. (Cl. 179-171) structed by arranging a plurality of vacuum tubes in circular fashion in annular re-entrant input and output cavities. At higher frequencies, annular cavities common to a plurality of vacuum tubes may not be suitable because the volumes of the cavities become too great to achieve the desired frequency of operation. The inherent internal capacitances of the plurality of vacuum tubes require that the volume of the cavities be smaller than can actually be obtained with the geometry of annularcavities. It is therefore a general object of this invention to provide a multiple tube system including resonant cavities having a configuration enabling operation at higher frequencies than have heretofore been possible.

It is another object of this invention to provide a.

multiple tube system including polygonal resonant cavities which inherently suppress undesired circulating modes of oscillation. t

It is another object to provide a multiple tube resonant cavity system which is less expensive to manufacture than previously known systems and which utilizes flat metallic sheets.

It is a further object to provide a multiple tube system including improved means for tuning the input and output circuits over a wide range of frequencies. A still further object of the invention is to provide a novel multiple tube system having a geometry enabling the charging current flowing thru the tube seals to be more uniformly distributed around the peripheries thereof so that the heating of the seals is reduced.

In one aspect, the invention comprises an amplifier including a plurality of electron discharge devices or vacuum tubes electrically coupled in parallel thru the medium of a complex, generally polygonal physical structure. The invention will be described, by Way of example, as having a generally pentagonal input cavity and a gen-' erally pentagonal output cavity, and having five vacuum tubes operatively disposed in the two cavities. The elements of the physical structure will be described in their relation with a metallic horizontal pentagonal separation plate separating the input cavity therebelow from the output cavity thereabove. The'structure is generally symmetrical about (though not a figure of revolution about) an imaginary vertical center line passing thru the center of the horizontal pentagonal separation plate. p 7 Five vacuum tubes are located in five circular apertures at the five corners of the pentagonal separation plate. The tubes extend down'into'the inputcavityandf up into the output cavity. The input cavity is in the form of a'pentagonal prism coextensive with the pentagonal separation plate and having a coaxial pentagonal reentrant member which may be adjusted axially to vary the volume of the input cavity. The pentagonal re-entrant member is arranged relative to the pentagonal separation plate so that the five corners of one are opposite thefive sides of the other. A coaxial input line includes a center conductor. connected .to the center of the separation plate and an outer. conductor connected to'a circular aperture in the re-entrant member. An adjustable impedance matching device is incorporated in the input coaxial line.

The output cavity is formed between the metallic sepa-' ration plate and a larger parallel pentagonal metallic output plate spaced thereabove. The respective sides of the pentagonal separation plate and the pentagonal output; plate are parallel. A fixed coaxial pentagonal re-e'ntrant structure extends thru the output plate into the output cavity. The corners of the pentagonal re-entrant structure are opposite the sides of the pentagonal output plate. An output coaxial line includes a center conductor connected to the. separation plate and an outer conductor connected to the edges of a circular aperture in the reentrant structure. An adjustable impedance matching device is incorporated in the output coaxial line. Five adjustable coaxial line shorted stubs are connected thru the re-entrant structure to the output cavity to serve as shunt inductors which are variable to adjust the output coupling consistent with the bandwidth requirements.

' All points along the periphery of the pentagonal output cavity are in communication with a downwardly extending transmission line, and all points along the inner edge of the output cavity adjacent the re-entrant structure are in communication with an upwardly extending coaxial transmission line. The downwardly extending, and the upwardly extending, transmission lines together constitute an output tuning line electrically a half wave length. The downwardly extending transmisison line is formed between an outer pentagonal prismatic wall connected to the outer edge of the pentagonal output plate, and a uniformly spaced inner pentagonal prismatic wall connected to the outer edge of the pentagonal separation plate. The upwardly extending transmission line is formed between-an outer pentagonal prismatic wall connected to a pentagonal aperture in the pentagonal output plate, and a uniformly spaced inner pentagonal prismatic wall connected to the outer edge of the pentagonal re-entrant structure. ,The efiective lengths of the two lines are adjustable by moving shorting bars axially between the inner and outer walls of the respective lines. The anodes of thefive vacuum tubes the pentagonal plate, the controland screen grids are,

input platen V 1 These and other objects and aspects of the invention will appear from a reading of the following more detailed Referring'now to the' drawings for description of a 7 section corresponding to that shown in Fig. 4 and showing the parts in a different ad- .justable'position.

five tube amplifier accordingto this invention, a separation plate forms a partition between an input cavity 11 and an output cavity 12. The separation plate 10 is pentagonal in shape and has five circular apertures near the five corners to receive five tetrode' vacuumtubes or electron discharge devices 13 which may'be RCA type 6166 tubes. The control grid contact ring 14 of each of the tubes '13 is contacted by: spring fingers "15 which have areas separated from the separation plate ltl'by mica dielectric plates'16. The control grids ofthetubes are thus capacitively coupled to the separation plateltl. The screen' grid contact ring 17 of each of"the"tubes 13 is similarly capacitivelv-coupled to the separation plate 10 thru spring fingers 18 and mica dielectric plates The input cavity 11 is formed between the separation plate 10 and parallel spaced coextensive input plate 20. The input plate 20 has a pentagonal aperture thru which a pentagonal reentrant member"21*extends into'th'e input cavity 11. The five peripherab sides of'the pentagonal input cavity 11' are closedbyfive vertical 'plates'22 to form a pentagonal prismatic wall. The walls 22"ext'eiid downwardly from the 'input plate 29 "for reasons which will appear as the description'proceeds. The input plate 20 is provided "with five rectangular wells 24 having springsockets 25 receptive to thefilament prongs 26 of the'tub'es 13; The tube filaments are capacitively coupled 'to 'the input plate 20 thru sockets 25; and dielectric sheets 27 to the walls of the wells 24 in the input plate 20. An input coaxial- 1ine'29 is connected thru an adjustable impedance matching device 30 to the input cavity 11, the center conductor'80 being connected thru conductors 77 and 31 to the center of the separation plate 10, and the'outer conductor 87 "being connected thru slidingcontacts': 88,1'0i21l3blfi member 85 and contacts 32 to a cylindrical depending fl'ange 33 forming a part of the re-entrant" member 21." The reentraut member 21 includes'a circular aperture 34 providing communication from the input impedance match ing device 30 to the interior of the input'cavity 11'. "T he re-entrant member 21 is reciprocable along 'the'vertical axis of the system by means of five input'cavity tuning rods 35, one of which is visible'in Fig. l and'all'of which are shown by dotted line circles in Fig. 2.' The" tuning rods 35 are moved axially in unison to vary the position of the re-entrant member 21 and thus vary" the volume or tuning of the input cavity 11; Contact is maintained'between the re-entrant member 21 and the input plate 20 by means of sliding contacts 36. it i It will be noted by reference to Fig. 2 that the peripheral edge of thte input cavity 11 is formed by the pentagonal prismatic walls 22, and that the inner edge of the input cavity 11 is primarily'determined' by thepentagonal prismatic walls 37*of. the: re entrant member '2ll Itwill also be noted that the pentagonal walls 22 and the pentagonal walls 37 are'oriented in such a way that the angles or corners of one. are radially'opposite the s des of the other. It will further be noted that'the five vacuum tubes are positioned between the five corners of the walls 22 and the five sides of the walls 37L By this construction, the volume within the input cavity 11 is suflicieiitly small so that'the'cavity will resonate at very high frequencies. The construction, being such as to include numerous angles, inherently attenu'ates'any undesired circulating modes of oscillation which might otherwise be present. It will'be understood, that' the input cavity 11 is primarily defined in the horizontal plane by the pentagonal

prismatic walls

22 and 37. However, the area between the re-entrantmernb'er 21 and the separation plate 10 is also part of the input cavity 11. Input energy is supplied to cavity 11 frdni input coaxial line 29 through the circular aperture 34fand the impedance matching device 30. l I; "I

The output cavity 12 will now be described w i th re:

erence to Figs. 1 and 3. In Fig. 3 theoutlipe of, the

pentagonal separation plate 10 is shown by a dotted line 22. The output cavity 12 is formed between the separation plate 10 and a pentagonal output plate 40 which is in parallel spaced relationship above the separation plate 10. The output plate 40 has pentagonal peripheral edges parallel with, and extending beyond the edges of the separation plate 10. A downwardly extending pentagonal prismatic wall or skirt 41 is connected to the peripheral edge of output plate 40. The pentagonal prismatic wall 41 is equally spaced on all sides from the pentagonal prismatic wall 22 to provide therebetween five rectangular volumes constituting a transmission line within which five rectangular shorting bars 43 (Figs. '1 and 2) are reciprocable. Metallic shorting bars 43 are maintained in electrical contact with

walls

22 and 41 by means of sliding

contacts

44 and 45. The five shorting bars 43 are moved in unison by means of five tuning rods 46, one of which is shown in Fig. 1 and allofwhich are shown by dotted line circles in Fig. '2. "Referring to Figs. 1 and 3, a fixed re-entrant structureextends into the output cavity 12. The re-entrant structure eomprises'a pentagonal base plate 48 having its "peripherycoiinected to a pentagonal prismatic wall 49. The fixed

re-entrant structure

48, 4 9 is maintained in spaced relation with the separation plate 10 by means of insulators 50, one of which is shown in Fig. 1. The output'plate 40 has a pentagonal aperture, the edge of which is connected to apentagonal prismatic wall or skirt5 2 extending upwardly in equally spaced relationship surrounding the pentagonal prismatic wall 43 of the

re-entrant structure

48, 49. The five rectangular volumesenclosedbetwee'n the

walls

49 and 52 constituting a"tran'smission line are closed at the top by means of five rectangular metallic shorting bars 53 having contact fingers 54 and'55 slidably engaging the

walls

52 and 49, respectively. The rectangular shorting bars'53 are moved in unison by five adjusting rods 56, one of which isv shown in Fig. l, and'all of which are shown in Fig. 3.

- apparent that the output cavity 12 is in communication at its periphery with a downwardly-extending'tuning line formed between the pentagonal

prismatic walls

22 and 41, and that the inner portions of the cavity 12 are in communication with an upwardly-extendirig tuning line formed between the pentagonal prismatie Walls"49 and 52/ The distance from the lower shorting bars 43 to the upper shorting bars 53 is electricallya half wave in length at the mean operating frequency'. 1 The output cavity 12 is thus tuned by varying in unison, all of-the shorting bars 43, and/or varying in unison all of the shorting bars 53.

' It 'is thus far Electrical energy is taken from the output cavity 12 by'means of an output coaxial line having a center conductor 58 connected'to-the separation plate 10, and having an outer'conductor 59 connectedto the edge of a circular aperture in the base plate 48 of the re -

entrant structure

48, 49. It is apparent that the output cavity 12 is in communication with the space between the coaxial output conductors 58' aiid'59 thru the space between the separation plate' 10 and the base plate 48 of the re entrant structure 48, 49'. Technically, the space between

theplates

10 and 48 is'a part of'the output cavity 12;

The output plate '40 is provi'ded with five circular apertures at thefive corners to receivethe five vacuum tubes 13, As shown in Fig. l, the anode contact ring 61 of each of tubes'13 makes';electrical contact with spring fingers 62 which are spaced from the output plate 44) by means of dielectric mica -sheets 63.

It will be noted-by' reference to Fig. 3 that the pentagonal prismatic walls '22 and 41 defining the outc edge of thefoutput. cavity 12 are related with the pentag'tinal prismatic walls 49. and 52 defining the inner edge of the output cavity 12 in such a way as to minimize thevolu ne'within the output cavity 12. The inner iti l ter. pi i agd al walls are arranged so that the i'slfi Iqiicornersoii one are opposite the sides of the b hat- B 't i a ang men the put-.- vi y. can be tuned to a higher frequency than would otherwisebe possible while employing tubes-of a given power rating or size.

Five adjustable coaxial line shorted stubs are connected thru the re-e ntrant structure to the output cavity 12 to serve as shunt-inductors which may be adjusted for that degree of output coupling which is consistent with the bandwidth requirements. Each coaxial line shorted stub consists of a-center conductor 65 connected to the separation plate 10, and an outer conductor 66 connected to the edge of a circular aperturein the base plate 48 of the

re-entrant structure

48, 49. It will be noted from Fig. 3 that the shorted

stubs

65, 66 are placed in the corners of the re-entrant structure-48, 49' and outside the central area of the re-entrant structure which is occupied by the

coaxial output line

58, 59. This con struction is such as to further a primary object of this invention which is to amplify high power radio frequency energy at very high frequencies. N

The effective or electrical length of each of the shorted

coaxial stubs

65, 66 is adjustably determined by the position'of a shorting ring 68 connected by a cradle 69 to an adjusting rod 70. together the

conductors

65 and 66 at the location of the rings. Axial movement of the adjusting rods 70 varies the shunt inductance coupled to the output cavity 12. The shunt inductors are adjusted to provide that degree of'overcoupling from the output cavity 12 to the out- 7 which results in the desired;

put coaxial line 58, 59 H frequency response characteristic over the bandof frequencies being amplified.

Included within the output

coaxial line

58, 59 is animpedance matching device in .the form of a discontinuity in the coaxial line which may be adjustedin positionalong 'the line. The impedance matching device consistsof a cylindrical sleeve 70' around and. spaced from the center conductor 58 by means ofapertured discs 71 and- 72. Sliding electrical contact'is'maintained between the peripheral edges of

discs

71 and 72 by means vofsliding metallic spring contacts 73. The assembly .is movable along the coaxial output line, by means ofa rod 74 .ex-

tending thru a longitudinal slot .75 in the/outer conductor 59. The device is positioned about}: half wavelength from the output cavity 12 and is adjusted so that the circuit formed by the discontinuity-and the length of the coaxial line is electrically resonant, giving. an impedance transformation which results in a pure resist-. ance at the separation plate 10.

Referring now to Figs. 1 and 4, the input impedance matching device generally designated 30 consists of two fixed inner conductors 77 and 78 both connected at 79 Ring 68 directly connects to the center conductor80 of the input coaxial line 29.

Both of the inner conductors 77 and. 78 are connected at their opposite ends to the separation plate 10, thru conductive members 81 and31.

The impedance matching device 30 also includes two. I

outer conductors

82 and 83 both connected at their lower ends to an annular flange 84 extending inwardly from.

a metallic cylinder 85. ,Theltop ends of the

outer conductors

82 and 83 are similarly'connected thru an annular flange 86 to the metallic cylinder 85. The

outer conductors

82 and 83, and the cylinder are rotatable as a unit. 'The lower end of cylinder 85 is maintained in electrical contact with the outer conductor 87 of the input coaxial line 29 by means of spring contac'ts88,

and the upper end of cylinders 85 is maintained in elec-' trical contact with the depending flange 33 of the input re-entrant member 21 by means of spring contacts 32.

The'outer conductors

82 and 83 may be rotated relative to the inner conductor 77 and 78 by rotating the cylinder 85.' When the outer conductors and cylinder are rotated 90 degrees from the position shown in Fig. 4, theparts-bear the relative relationships shown in Fig. When the inner-and outer conductorsbear the' relationship shown in Fig. 4, the capacitancefabetweenm tively narrow band of component frequencies.

6 the- -inner and-outer conductors is a maximum; 'and when the parts are in the positions shown in Fig. '5, the capacitance; is a minimum. The inner conductors may be positioned anywhere between the two extremes shown in Figs. 4 and 5.

The five vacuum tubes 13 are each supplied with operating potentials as follows: The secondary coil 90 of a filament transformer 91 is connected thru leads 92 to the spring sockets 25 engaging the filament prongs 26 of the tube 13. The leads 92 are by-passed to ground at a distance of a quarter-Wavelength from the tubes so that the secondary coil 90 of transformer 91 is at ground potential so far as the radio frequencies are concerned.

The control grid contact ring 14 on tube 13 is connected thru spring contacts 15 thru a lead 93 to the negative terminal E0 of a source of unidirectional potential. A bypass capacitor 94 is connected to ground at a point a quarter wavelength from the tube. The screen grid contact ring'17 of tube 13 is connected thru spring contacts 18 and a lead 95 contained in -a shielding tube (not shown) to the positive terminal 96 of a source of unidirectional screen grid potential. The lead 95 is also bypassed to ground at a point a quarter wavelength from the tube. The anode contact ring 61 of tube 13 is connected thru spring contacts 62, lead 97 and plate resistor 98 to the 13+ terminal of a source of unidirectional potential. The line 97 is by-passed to ground at aquarter wavelength from the tube.

The five tube amplifier shown and described herein by way of illustrating the invention, is capable of providing I 50 kilowatts of radio frequency output peak power at any frequency in the range between 174 and 216 megacycles. This frequency range includes channels 7 thru 13 in the very high'fr'equency television broadcasting band presently employed in the United States. Ten kilowatts of radio frequency energy to'be amplified is applied thru the input coaxial line 29 to the amplifier. The input energy applied to the amplifier maybe that obtained from a standard 10-kilowatttelevision transmitter. The amplifier is designed to amplify television picture signals having fre-. quency components extending over a band which, according to present standards, is 4.5 megacycles wide. The sound signals of a television broadcast are normally amplified in a separate amplifier designed to amplify a rela- The amplified sound signals are normally combined with the amplified picture signals in a diplexer or filteiplexer from which the combined signal is applied to a radiating antenna.

In the operation of the multi-tube amplifier of this invention, radio frequency input energy is applied thru theinput ,coaxial line 29 and thru the input impedance matching device 30 to' the input cavity 11. The input cavity '11 is tuned by adjusting its volume to the particular frequency being amplified. This adjustment is made by moving the input re-entrant member 21 thru the medium of the five tuning rods '35 until the input cavity 11 is tuned to the desired frequency. The

outer conductors

82 and 83 of the input impedance matching device 30 are rotated relative to the fixed inner conductors 77 and 78 to a position which provides the optimum impedance match, between the input line 29 and the input cavity 11. This position is found by minimizing the measured standing wave ratio on line 29. The tuning adjustment (re-entrant member 21) and the impedance matching adjustment (device 30) are mutually dependent and are mutually varied to minimize the standing Wave ratio on input line 29.

The energy within the input cavity 11 is applied between the control grids and filaments of the five amplifiervacuum tubes 13. The amplified radio frequency energy appears between the anode electrodes and the screen grid electrodes of the five tubes 13 from whence it is coupledto the output cavity 12. The output cavity 12 is tuned to the frequency being amplified by adjusting the effec- .tive length ofthe double endedoutput' tuning wave line which is definedby coaxial inner and outer pentagonal prismatic walls. The ettective length of the outputtuning line is adjusted by moving the five shorting bars 43 inunison at the lower end of the guide, and/or moving the five shorting bars 53 in unison at the upper end of the tuning wave guide. The output cavity 12 is tuned to the desired frequency when the eifective electrical distance from the lower'shorting bars 43 to the upper shorting bars 53 is a half wavat the desired mean frequency of operation. The double ended line is the means by which the anode circuit of the amplifier is tuned.

Energy. from the output cavity 12 is coupled to the output coaxial line 58, '59. The coupling between the output cavity 12 and the output coaxial line is optimized by adjusting the five shunt inductors. The shunt inductors are in the form of shorted coaxial stubs each including an. inner conductor 65 and an outer conductor 65. The eifective length of each shorted stub is determined by, the position ofthe. shorting ring, 68 slideably located between the inner conductor 65 and: the outer conductor 66, They shunt inductors are adjusted to. provide that degree of. overcouph'ng between. the output cavity 12 and the output coaxial line, 58, 59, which results in the. desired broadband-pass characteristic.

An output impedance matching device. 70', 71, 72 forms a discontinuity in the coaxial output line 58, and its position along the line may be adjusted to tune the secondary circuit; formed by the length of output line between theseparation plate and the discontinuity. The impedance matching device is normally positioned at a distance of approximately a half-wavelength from the output cavity 12, and its exact position is adjusted thru the medium of the adjusting rod 74 extending thru a slot 75 in the outer conductor 59. of the output coaxial line.

The polygonal. multiple, tube system of this invention has been shown and described in the form of an amplifier. It will, of course, be understood that the teachings of this invention are not limited. to amplifiers, but are applicable to oscillators and other forms of translating circuits as well. to peritagonalarrangements, but is also applicableto other polygonal arrangements What is claimediisi 1Q A resonant cavity having a volumein the geometricalform of a polygonal prism with a coaxial polygonal prismatic aperture therein, said prism and said aperture having an equal number of sides, said prism and said aperture being oriented so that the corners of one are opposite the sides of the other.

' 2. A resonant cavity as defined in claim 1 and in addition a vacuum tube electrically coupled thereto and physically disposed at least partially within said cavity between a corner of said prismjand an adjacent side. of said aperture. j

3. The combination of a resonant cavity having a volume, in the form of a polygonalprism ofn sides with. a coaxial prismatic apertureof n sidestherein, said aperture being oriented relativeto the prism so that they corners of one are opposite the sides of the other, and n electron discharge devices electrically coupled thereto and physically disposed betweenthen cornersof said prism and the n sides of said aperture.

4. A resonant cavity having a volume in the geometrical form of apolygonal prism with a coaxial polygonal prismatic re-entrance therein, said prism and said reentrancehaving an equal number of sides, said prism and said re-entranoe beingdisposed with theacorners of. one opposite. the sides oi the other.

5. A resonant cavity as defined in claim 4., and in addition an electron discharge device electrically. coupled theretov and physically disposed at least partially within.

said. cavity between. a, cornerof said prism .and an adjacent sideof said re-entrance,

6, The, combination. of, a resonant .cavity. havinga. ,vvol-t Obviously, the invention is not limited time in the form of a polygonal prism oi n sides with a coaxial prismatic rc-entrance of it sides therein, said reentrance being oriented relative to the prism so that the corners of one are opposite the sides of the other, and n vacuum tubes electrically coupled to said resonant cavity and physically disposed between the n corners of said prism and the n sides of said re-entrance.

7. A resonator system comprising first and second spaced polygonal end plates connected at their peripheries by sidewalls to define a polygonal prismatic cavity, said first end plate having a polygonal aperture therein, said polygonal end plate having the same number of sides as said polygonal aperture therein, the corners of one being opposite the sides of the other, a polygonal prismatic re -entrant member disposed in said polygonal aperture, said re-entrant member having a circular aperture therein, and a coaxial line having an outer conductor connected to the edge ofsaid circular aperture, and having an inner conductor connected to said second end plate.

8. A resonator system asdefined in claim 7 wherein said polygonal prismatic re-entrant member is axially movable'to vary'the' volume within said cavity.

9. A resonator system as defined in claim 7, and in addition, a plurality of electron discharge devices electrically coupled to said cavity and physically disposed in said cavity between said sidewalls and said reentrant member.

10. A resonator system as defined in claim 7, and in addition, a plurality of electron discharge devices electrically coupled to said cavity and physically disposed in said cavity in the spaces between the corners formed by said sidewalls and the sides of said polygonal re-entrant member.

11'. A resonator system as defined'in claim 10 wherein said polygonal prismatic re-entrant member is axially movable to vary the volume of said cavity.

12. A resonator system comprising first and second spaced polygonal end plates, said second end plate having a polygonal aperture therein, the edges of said aperture beingopposite the peripheral edges thereof, a polygonal prismatic re-entrant member having sidewalls and a base plate extending into said polygonal aperture, a polygonal skirt connected at one end to the polygonal aperture in said second end plate in equally spaced relationship around the sidewalls of said re/entrant structure, said skirt and the sidewalls of said re-entrant structure definingtherebetween a tuning line in communication with the cavity between said first and second end plates, and two polygonal coaxial spaced skirts having corresponding ends connected respectively to the peripheral edges of said first and second end plates to define therebetween a second tuning line incommunication with the cavity between said fii st. and second end plates.

13-. A resonator system as defined'in claim 12, and in addition, a plurality of electron discharge deviceselectrically coupled to said cavity, and physically disposed in thecavitybetween said first and second end plates.

14. A resonator system as defined in claim 12, and in addition, shortingmeans in said'tuning lines to determine the effective electrical lengths thereof.

15. A resonator system as defined inclaimlZ, wherein said base plate of said re entrance structure has a circular aperture, and in addition, a coaxial line having an outer conductor connected to the edge of said circular aperture, and having an inner conductor connected to said firstend plate.

16 Areson'ator system as def ned in claim 15 wherein said baseplateof said re-entrant structure includes a second circular aperture, and in addition, a coaxial line tuning stub including-an outer conductor connected to the edgeof said secondcircular aperture,- and including a center conductor connected to said first end plate.

17. A resonatorsystem as;d efined in claim 16, and in addition; means toyarycthe etiective-electrical. length of said ,tuningstub'.

relation therewith, said input 18. A multiple tube system comprising a polygonal separation plate, a polygonal input plate in parallel spaced plate being provided with a polygonal aperture, a polygonal prismatic re-entrant member extending thru said polygonal aperture, sidewalls connecting the peripheral edges of said separation plate and said input plate, whereby a polygonal input cavity is formed, said re-entrant member having a circular aperture, a coaxial line having an outer conductor connected to the edge of said circular aperture and having an inner conductor connected to said separation plate, a polygonal output plate in parallel spaced relation on the opposite side of said separation plate, said output plate being provided with a polygonal aperture, a polygonal prismatic re-entrant structure disposed within said polygonal aperture, an enclosure connecting the peripheral edges of said output plate and said separation plate, whereby to form an output cavity, said re-entrant structure having a circular aperture, and an output coaxial line including an outer conductor connected to said circular aperture and an inner conductor connected to said separation plate, and a plurality of electron discharge deviceselectrically coupled to said input and output cavities and physically disposed therein.

19. A multiple tube system as defined in claim 18, and in addition, a polygonal prismatic tuning line in communication with said output cavity.

20. A multiple tube system as defined in claim 18, and in addition, a plurality of coaxial line shorted stubs coupled thru said re-entrant structure to said output cavity.

21. A multiple tube system as defined in claim 18, and in addition, an impedance matching device operatively connected between said input coaxial line and said input cavity.

22. A multiple tube system as defined in claim 18, and in addition, an adjustable impedance matching device positioned within said output coaxial line.

23. A radio frequency translating device comprising, a plurality of electron tubes disposed in a circle about an axis, said tubes having input and output electrodes, a

I first cavity resonator common to and electrically cou- 24. A radio frequency translating device as defined in. claim 23 wherein each of said cavity sections have an axis common with said axis about which the tubes are disposed.

25. A radio frequency translating device as defined in claim 23 wherein at least one of the cavity sections of each of said first and second cavity resonators is adjustable in axial length to tune the respective resonator.

References Cited in the file of this patent UNITED STATES PATENTS 2,473,777 Belchlyn June 21, 1949 2,487,619 Usselman Nov. 8, 1949 2,554,501 Preist May 29, 1951 2,562,323 Martin July 31, 1951 2,565,113 Baker Aug. 21, 1951