US3248595A

US3248595A - Radio frequency apparatus

Info

Publication number: US3248595A
Application number: US173703A
Authority: US
Inventors: Rudolph A Dehn
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1962-02-16
Filing date: 1962-02-16
Publication date: 1966-04-26
Anticipated expiration: 1983-04-26
Also published as: DE1616907A1; GB1033016A

Description

April 26, 1966 R. A. DEHN 3,248,595

RADIO FREQUENCY APPARATUS Filed Feb. 16, 1962 Il g3 25 by United States Patent O 3,248,595 RADIO FREQUENCY APPARATUS Rudolph A. Deliri, Schenectady, N.Y., assigner to General Electric Company, a corporation of New York Filed Feb. 16, 1962, Ser. No. 173,703 9 Claims. (Cl. S15-5.16)

This invention relates to radio frequency (RF.) apparatus and more particularly to new and improved means for combining the operation and output of a plurality of space-charge control tubes.

High power levels of microwave frequency electromagnetic wave energy are customarily produced by such power tube devices as magnetrons, klystrons and traveling wave tubes. However, these devices require quite high operating voltages and also require heavy magnetic fields for focusing or other operating effects on electrons within the devices.

Microwave frequency electromagnetic wave energy may also be produced with space-charge control devices such as the planar electrode tube structures known to those skilled in the art. Such devices are operative with relatively low operating potentials, due to the close spacing of electrodes within the devices, and require no magnetic field for focusing or otherwise influencing the electrons. However, the power output of the space-charge control devices heretofore known in the art has been quite limited and is not comparable to the power levels produced by the other devices previously mentioned, such as magnetrons or the like.

It is frequently desirable to have a source of relatively high power level electromagnetic wave energy which does not require the high operating voltages or the large magnetic fields of the magnetrons, klystrons, traveling wave tubes or the like. For example, such a source of power is quite desirable in microwave heating applications including the electronic ovens presently being produced which utilize high frequency energy in the cooking of foods. However, the planar electrode space-charge control devices known in the art do not provide sufficiently high power levels to operate such devices and, accordingly, magnetrons have generally been used for this purpose even though they require high operating voltages and large magnetic iields.

Also, when space-charge control tubes, such as triodes and tetrodes, are operated in grounded grid fashion, radio frequency energy is required to accelerate electrons from the cathode across the cathode grid gap. This results in an equivalent positive input conductance in shunt with the capacitive susceptance of the cathode-grid electrodes. Now, if a plurality of such tubes are to be operated in a periodically loaded waveguide resonator, the mentioned conductance will make the attenuation in the grid-cathode resonator high; and the radio frequency input signal will not appear equally at all tubes in the circuit. In order to avoid excessive attenuation and achieve more uniform excitation of the tubes, the tube input admittance must be appropriately decoupled from the waveguide resonator.

It is, accordingly, an object of this invention to provide a new and improved source o-f microwave frequency electromagnetic wave energy.

It is another object of this invention to provide a new and improved source of microwave frequency electromagnetic wave energy which is operable from a relatively low voltage source and which requires no magnetic lield for operation.

`It is yet another object of this invention to provide new and improved means for combining the operation and output of a plurality of space-charge control electron discharge devices including an input waveguide resonator periodically loaded by a plurality of such devices and 3,248,595 Patented Apr. 26, 1966 ice means for effectively decoupling the input admittance of the tubes from the resonator, thereby to avoid excess-ive attenuation and to achieve uniform excitation of the tubes by an input signal introduced into the waveguide resonator.

It is a further object of this invention to provide a device for combining the operation of a plurality of spacecharge control tubes in a manner which affords maximum mode separation and provides for substantially the total power handling capabilities of the number of devices so combined.

Briefly stated, and in accordance with one embodiment of the invention, radio frequency apparatus is provided which comprises an input resonant waveguide and an output resonant waveguide. A plurality of equally spaced space-charge control devices are mounted in the waveguides with the cathode-grid interaction gaps thereof coupled to the input waveguide and the corresponding concentrically opposite grid-anode interaction gaps thereof coupled to the output waveguide. The grid-anode gaps are coupled to the output waveguide in a longitudinal plane extending through the center of the output waveguide while the cathod-grid gaps are coupled to the input waveguide in a longitudinal plane which is laterally or transversely spaced from the center of the input waveguide. Provided in each waveguide and each at a point midway between e-ach adjacent pair of control devices are a plurality of passive capacitive elements. The waveguides are thus each periodically loaded by alternate active and passive capacitive elements and preferably the periodic spacing between adjacent elements is 1A the length of an electromagnetic wave in the waveguides when the waveguides are resonated at a predetermined frequency. The devices are biased in the usual manner known to those skilled in the space-charge control tube art and a standing electromagnetic wave of the aforementioned predetermined frequency is induced in the input waveguide by means of any suitable coupling device. The standing electromagnetic Wave in the input resonator controls the emission of electrons from the cathodes of the devices and the resultant density-modulated electrons traverse the grid-anode circuit and induce a corresponding standing electromagnetic wave in the output waveguide. Suitable means are provided for extracting electromagnetic wave energy from the output resonant structure. The off-center positions of the devices relative to the input waveguide effectively decouples the input admittance of the devices from the waveguide. If desired, the space-charge control devices can be either constructed integrally with the waveguides or as separate tubes detachably mountable in the waveguides.

For a better understanding of my invention, reference may be had in the accompanying drawing in which:

FIGURE 1 is a sectional view of apparatus constructed according to one embodiment of the invention;

FIGURE 2 is a view taken along the sectional lines 2 2. of FIGURE l and looking in the direction of the arrows;

FIGURE 3 is an wdiagram showing a graphical relation between the frequency of operation of a periodicallyloaded waveguide and the phase shift per section of such a waveguide;

FIGURE 4 is a sectional view similar to that of FIG- URE l and shows a second embodiment of the invention; and

FIGURE 5 is a View taken along the lines 5 5 in FIGURE 4 and looking in the direction of the arrows.

Referring now to FIGURE l, therein is shown radio frequency apparatus constructed according to one embodiment of the present invention. This apparatus includes an input resonator 2 and an output resonator 3.

Each of the resonators comprises an electrically-shorted section of a substantially rectangular waveguide and the resonators are juxtaposed so as to have a common wall 4 separating the

resonators

2 and 3. The input resonator 2 is provided with suitable input means, such as an inductive coupling loop 2a, at one end and the output resonator 3 is provided with suitable output means, such as an inductive coupling loop 3a, at the opposite end.

From the outset, it is to be understood that the waveguides need not have a rectangular cross-sectional configuration but can be of any desired cross-section. Also, and as seen in FIGURE 2, the

resonators

2 and 3 are not vertically aligned but -are relatively offset. The purpose and advantages of this arrangement will be discussed in detail hereinafter.

The upper and lower walls of the

resonators

2 and 3 are suitably `apertured to provide sever-al aligned equally spaced tube sockets therein. Positioned in such sockets are space charge control devices generally designated 5. Each device 5 comprises a suitable envelope structure 6 and constitutes a triode including a cathode 7, a control grid 8 Iand an anode 9 which are suitably spaced and mutually insulated. The cathode 7, grid 8 and anode 9 are provided with suitable

coaxial contacts

11, 12 and 13, respectively, which, when the devices 5 are inserted in the sockets in the waveguides, make suitable coaxial electrical contact with the respective walls of the waveguides. Specifically, the cathode contacts 11 engage the lower wall of the input waveguide 2, the grid contacts 12 engage the intermediate, or common, wall 4 and the anode contacts 13 engage the upper wall of the output waveguide 3. In this manner the cathode-grid interaction regions (7, `8), or gaps, of the tubes are coupled to the input waveguide for enabling energy exchange interaction between any electromagnetic wave in the input circuit and electron flow across the grid-cathode space or interaction gap. The grid-anode interaction regions (8, 9), or gaps, of the tubes are similarly coupled to the output waveguide for enabling inducement therein of electromagnetic Wave energy. It is to be understood from the foregoing that while the devices 5 are disclosed as discrete devices detachably mounted in the waveguide circuits, they could, if desired, be constructed integrally with the waveguides. In such a structure the complete assembly, including the waveguide sections, could be evacuated and hermetically sealed.

Interposed midway between each adjacent pair of devices 5 and yaligned therewith in both the input and output waveguides is a passive, or dummy, capacitive element 15. Each element 15 in the input section is substantially identical in capacitance value to each of the corresponding reaction gaps defined by the cathode-grid and each element 15 in the output section is substantially identical in such value to each corresponding gridanode gap of the devices 5. It is to be understood that the capacitance values of the cathode-grid and grid anode values may be of different values dictated by the electronic of the devices 5. Also, the spacing between the outermost devices 5 and the end walls of the waveguides is the same as between adjacent devices 5 and dummy elements 15. Thus, the

waveguides

2 and 3 are each uniformly periodically loaded with alternate active and passive capacitive elements. The elements 15 can be capacitors defined by upstanding conductive posts, as shown, or can be constructed in any suitable alternative manner. The electrical spacing between adjacent active and passive elements and between the end walls of the resonators and the outermost capacitive elements is preferably 1A of the loaded waveguide wave length at a predetermined operating frequency which results in electric field maxima and minima being located, respectively, at the reaction gaps Iand passive elements. This general arrangement of input and output resonators periodically loaded with alternate active and passive capacitive gaps of equal value and operation such that the field maxima and minima are located, respectively, at active and capacity gaps, does not constitute the entirety of the present invention which is an improvement thereover, but is the invention disclosed and claimed in copending U.S. application S.N. 173,724 of M. R. Boyd et al. filed concurrently herewith and assigned to the same assignee as the present invention. The present invention involves the combination of space-charge control devices and such periodicallyloaded resonators, but also means for avoiding excessive attenuation of an input signal in a periodically-loaded input resonator and achieving uniform excitation of the space-charge control devices by that input signal.

The operation of the above-described apparatus is as follows: The space-charge control devices are operated in a grounded grid fashion, inasmuch as the control grids for the devices are directly connected to the walls of the resonators. An accelerating direct current field is established lbetween each of the grids 8 and the associated anodes 9 in any suitable manner (not shown). The cathodes 7 can -be energized in `any suitable manner, as by the filamentary heaters schematically shown, and so as to emit electrons under the infiuence of an electric field of the proper polarity. An input signal is supplied to input resonator 2 through the input loop 2a, with the input signal establishing a standing electromagnetic wave of the aforementioned predetermined freqeuncy in the input resonator 2. Inasmuch as the end portions of the resonator 1 are short circuited, whereby an electric field minimum must there exist, electric field maxima are established at each of the cathode-grid gaps and electric field minima `at each of the passive elements 15. An alternating electric field in accordance with the input signal and of maximum magnitude is established between each of the cathodes 7 and its respective associated control grid 8. Electrons are emitted from each of the cathodes under the influence of the positive half cycles of the alternating signal thereby established and these electrons pass through the control grids and enter the grid anode gaps wherein they are subjected to the accelerating direct current field therein. Thus, bunches of electrons are delivered to each of the anode members in accordance with the standing input signal wave in the resonator 2 and these bunches of electrons induce a corresponding electromagnetic wave in the output resonator 3. The energy exchange between the bunches of electrons and the induced electromagnetic wave in the grid-anode gaps delivers electromagnetic Wave energy to the wave, in a manner well known to those skilled in the space-charge tube art. Electromagnetic wave energy can be extracted from the output resonator 3 through the output coupling means 3a.

In the above-discussed operation the passive capacity elements 15 serve to maintain the desired operation wherein the electric field maxima occur in the resonators at the interaction gaps of the space charge control devices 5. Also, the described periodic loading serves to afford maximum mode separation. This latter function will be better understood from a discussion of the propagation and wave-supporting characteristics of the periodicallyloaded waveguides provided in the above-described structure. In such structure an electromagnetic wave in either of the

resonators

2 and 3 is presented with periodically arranged capacitances in the form of either the cathodesgrid gaps and the passive elements 15 in resonator 2 or the grid-anode gaps and the passive elements 15 in resonator 3. Thus, each of the

resonators

2 and 3 is, in effect, an electrically-shorted section of a periodically loaded waveguide with the periodic loading afforded by alternate interaction gaps of space-charge control tubes and passive capacitive elements.

FIGURE 3 is -an wdiagram and shows the graphical relation of the phase shift per section of matched periodically-loaded waveguides as a function of the frequency of an electromagnetic wave within one of such waveguides. As seen in FIGURE 3, each of the loaded waveguides has alower limit of frequency, or lower cut-off frequency, below which energy will not be propagated therethrough. As the frequency increases above the lower cut-off frequency, propagation becomes possible; and if the frequency is continuously increased above cutoff, a frequency will ultimately be reached where the spacing between adjacent periodic capacitances in the periodically-loaded waveguide becomes equal to half of a waveguide wavelength. At this frequency, the phase shift between adjacent capa-citances is equal tol 1r radians. The reilection from a capacitance then reinforces the reflection from the immediately preceding periodic capacitance land the overall effect in a long waveguide is total reflection and no propagation. The matched periodicallyloaded waveguide thus serves as a band-pass filter for frequencies between these upper and lower cut-olf frequencies. The matched periodically-loaded waveguide also has pass bands and stop bands at higher frequencies, but they are of no interest for the present discussion.

While the matched periodically-loaded waveguide can support an electromagnetic wave having a frequency of yany value within the pass band, an additional limitation exists when the periodically-loaded waveguide is made resonant by terminating the ends in short circuits, as is the case for the above-described resonators. Resonance occurs in the short-circuited periodically-loaded waveguides only at those frequencies in which the structure is an integral number of loaded guide half wave lengths long and in such waveguides the total phase shift along the guides must thus be an integral multiple of 1r. In other words, resonance occurs only at frequencies at which the difference in phase of the wave at two adjacent periodic capacitances is vrn/N Where N is the number of sections into which the line is divided by the periodic capacitances and n is an integer in the interval w=I to n=N. Thus, lf he resonators 2 and 3 are capable of supporting electromagnetic waves only of the frequencies indicated at positions 16-23 of FIGURE 3, with each of these frequencies having a phase shift per sec- OII Of vr/S, 11"/4, 31r/8, '1r/2, 51r/2, 31r/4, 71r/8 and 1r r3.- dians, respectively. It is noted that all of these frequencies lie between the lower cut-olf frequency and the upper cut-E frequency of the lirst pass band of the periodically-loaded waveguide.

It is known that maximum energy transfer between an electromagnetic wave and an interaction gap occurs when electrons see the greatest possible integrated electric ield when passing through the gap. As mentioned above, the described loading Iincluding alternate lactive and passive gaps and operation of the apparatus at the mentioned predetermined frequency are effective for maintaining the apparatus operative stably in the 1r/2 mode in which the electric field maxima in the waveguides coincide with the positions of the interaction gaps. Thus, efficiency is maximized. Also in the 1r/2 mode maximum mode separation is obtained. Additionally, the described operation enables the production of high power output with the low voltages at which the space-charge control devices 5 characteristically operate. This enables power production at levels which are generally not attainable with such devices. Also, it minimizes power supply requirements.

When space-charge control tubes are operated in `a grounded grid fashion, as is the case in the operation of the above-described apparatus, radio frequency energy accelerates electrons from the cathodes of the tubes across the cathode-grid interaction region. This results in an equivalent positive input conductance in shunt with the capacitive susceptance of the cathode-control grid electrodes. If, as in accordance with the present invention, a plurality of such tubes are operated in a periodicallyloaded input waveguide resonator, this conductance tends to make the attenuation of the input resonator high and cause the input radio frequency signal not to appear equally in all of the interaction regions defined by the cathodes and the respective control grids. The abovedescribed offset arrangement shown in FIGURE 2 locates the tube interaction gaps and passive elements therebetween on a line spaced parallel to the center line of the input Iwaveguide. This avoids excessive attenuation and achieves uniform excitation of the several tubes by decoupling the individual unit input admittances from the input waveguide resonator 2. The output resonator 3 is centered about the control grid-anode interaction rcgions of the devices 5 in order to achieve maximum energy transfer from the passing electrons to the standing electromagnetic Wave therein, thus to achieve maximum gain and efficiency.

FIGURE 4 shows a cross-sectional view of another embodiment of the invention. The apparatus shown therein includes input and

output resonators

25 and 26, respectively, similar to the resonators of the structure of FIGURE l, but the resonators of FIGURE 4 are supported in spaced parallel relation rather than being juxtaposed and having a common wall, as is the case in FIGURE 1.

The resonators 2S and 26 include input and output coupling means shown as inductive loops designated 25a and 26a, respectively. Also, each resonator comprises an electrically-shorted section of waveguide and is suitably adapted for having tetrode-type space-charge control devices 27 mounted therein. Each device 27 comprises a suitable envelope structure 28 containing a cathode 29, a control grid 30, a screen grid 31 and an anode 32, which electrodes are suitably spaced and mutually insulated. The cathode 29, control grid 30, screen grid 31 and anode 32 are provided with suitable

coaxial contacts

33, 34, 3S and 36, respectively, which, when the devices are mounted in the waveguides, make suitable coaxial electrical contact with the respective walls of the waveguides. Specifically, the

contacts

33 and 34 engage the lower and upper walls, respectively, of the input waveguide 25 and the

contacts

35 and 36 engage the lower and upper walls, respectively, of the output waveguide 26. Thus, the cathode-control grid interaction regions, or gaps, of the tubes are coupled to the input waveguide for interaction between any electromagnetic wave energy therein and electron flow across the cathodethe devices 27 can be either discrete detachable structures as illustrated or, if desired, can be constructed integrally with the waveguides in a single evacuated and hermetically sealed device.

The

waveguides

25 and 26 are provided with passive, or dummy, capacitive elements 37 which are located in the same positions and serve the same functions as the capacitive elements 15 of the above described iirst embodiment. Additionally, the same spacing is provided between the device 27 and passive elements 37 for periodically loading the waveguides in the same manner and for the same purpose as described above.

Additionally, and as seen in FIGURE 5, the output waveguide 26 is centered about the screen grid-anode interaction regions of the devices 27 and passive elements 37 therebetween in order to achieve maximum energy transfer to the standing electromagnetic wave induced in the output waveguide, thereby to achieve maximum gain and eiciency. However, the input Waveguide ZS is offset relative to the output waveguide and thus the cathode-control grid interaction regions of the devices 27 and passive elements 37 therebetween are transversely spaced from the longitudinal center or axis of the input waveguide. In this embodiment also, the olf-center relationship serves to avoid excessive attenuation of the input signal and achieves uniform excitation of the devices by that signal by effectively decoupling the individual unit input admittances from the input Waveguide.

The operation of the device of FIGURE 4 and 5 is as follows: An accelerating D.C. potential is established in any suitable manner (not shown) between the control grids 30 and screen grids 31. The cathodes 29 can be maintained at the same potential as the control grids 30 if desired and the anodes 32 maintained at the same potential as the screen grids 31. An input signal at the above-mentioned predetermined frequency is induced in the input resonator 25 through input means 25a. Electrons leave the cathode members 29 under the influence of the positive half cycles of the induced wave and the leaving electrons, in passing between the control grids 30 and screen grids 31 are accelerated to a relatively high velocity and enter the interaction regions between the screen grids and the anodes 32 at this relatively high velocity. The passage of electrons through the interaction region induces a corresponding standing electromagnetic wave in the output resonator 26. Maximum energy transfer from the electrons in the screen grid-anode interaction regions to the electromagnetic wave in the output resonator is obtained if the electrons enter the interaction regions during the negative half cycles of the induced electromagnetic wave, whereby the electrons are decelerated a maximum amount and deliver, or surrender, the maximum possible energy to the electromagnetic wave.

Either the triode apparatus of FIGURES 1 and 2 or the tetrode apparatus of FIGURES 4 and 5 can be operated in class C operation, so as to provide maximum eiciency, by providing suitable biasing means upon the cathode members of the devices therein. When so operated, the biasing voltage prevents electrons from leaving the cathodes except during the short portion of the input cycles centered about the positive crest of the alternating control-grid-cathode field. The electrons therefor enter the output resonators in discrete groups or bunches so as to provide the most eflicient energy transfer to the output resonator.

Either of the devices of FIGURES 1 `and 2 or FIG- URES 4 and 5 can be operated as an amplifier to amplify an input signal or can be operated as an oscillator so as to constitute a source of electromagnetic wave power. Any of the suitable feedback arrangements known to those skilled in the art can be utilized in producing suitable oscillation in the devices.

While the invention is thus shown and the modes of operation of specic embodiments described, the invention is not limited to use in these shown embodiments. Instead, the foregoing will suggest many modifications to those skilled in the art and which will lie within the spirit and scope of the invention. It is specifically intended that the invention include structures wherein the input and output resonators are relatively ofset both with and without the passive members positioned between adjacent active elements or devices. Also, the invention is not limited to use in structures having only four electron discharge devices mounted therein, `but can be used in a structure having any desired number of such devices. Further, the invention is not limited to use in structures in which the input and output resonators are straight sections of rectangular waveguides, but can equally well be used in devices in which the resonators are curved sections of waveguide and wherein the cross-sectional conguration of the waveguide is other than rectangular. It is thus intended that the invention be limited in scope only by the appended claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A multiple beam radio frequency apparatus comprising a pair of parallel resonant input and output waveguides each periodically loaded by alternate space-charge control devices and passive capacitive elements, said devices each including a cathode-grid gap coupled to one of said waveguides and a correspondingly directly opposite grid-anode gap coupled to the other of said waveguides, means for establishing in said one waveguide a standing electromagnetic wave having an electric field maxima occurring at each cathode-grid gap and a minima occurring at each said passive element therein, whereby an amplified electromagnetic wave is induced in said other waveguide corresponding to said wave in said one waveguide and having electric field maxima and minima occurring, respectively, at said grid-anode gaps and passive elements therein, said waveguides being positioned in adjacent relationship so that the center line of one is in spaced parallel and transverse relationship to the corresponding center line of the other, said space charge devices being positioned and extending into each said waveguide so that each said device is along the center line of said one waveguide but transversely spaced from the said corresponding center line of said other waveguide and means for extracting radio frequency energy from said other waveguide.

2. A multiple beam radio frequency apparatus comprising a pair of parallel resonant offset waveguides each periodically loaded by means including a plurality of alternate equally-spaced electric discharge devices and passive capacitive elements, said devices each including one interaction gap coupled to one of said waveguides and another corresponding opposite and concentric interaction gap coupled to the other -of said waveguides, said one interaction gap being located off the center line of said one waveguide and its concentrically opposite interaction gap being located on the center line of said other waveguide, and means for establishing a standing electromagnetic wave in said one waveguide and extracting energy from said other waveguide.

3. A multiple beam radio frequency apparatus comprising a pair of parallel resonant offset input and output waveguides each periodically loaded by means including a plurality of equally-spaced space-charge control devices and alternate passive capacitive elements, said devices each including a cathode grid interaction gap coupled to said input waveguide and a grid-anode interaction gap coupled to said output waveguide, said cathode-grid gap being located off the center line of said input waveguide and said grid-anode gap being located in said output waveguide in concentrically opposite relationship to said cathode-grid gap and on the center line of said output waveguide, and means for establishing a standing electromagnetic wave 1n said input waveguide and extracting energy from said output waveguide.

fl.l A multiple beam radio frequency apparatus comprislng a pair of parallel resonant elongated input and output waveguides each periodically loaded by plural alternate space-charge control devices and plural passive capacitive elements, said devices each including a cathode-grid gap coupled to said input waveguide at a point spaced from the center line thereof and an opposite corresponding concentric grid-anode gap coupled to said output waveguide directly opposite said cathode-grid gap and, at the center line thereof, means for establishing in said input waveguide a standing electromagnetic wave having an electric field maxima occurring at each said cathode-grid gaps and a minima occurring at each said passive elements therein, whereby an amplified electromagnetic wave is induced in said output waveguide corresponding to said wave 1n said input waveguide and having electric eld maxima and minima occurring, respectively, at said gridanode gaps and passive elements therein, and means for extracting radio frequency energy from said output waveguide.

5. A multiple beam radio frequency apparatus compising a pair of parallel resonant waveguides having a cornmon wall section, each said waveguide being periodically loaded by means including a plurality of alternate equallyspaced space-charge control triodes, said triodes and passive gap elements each including a cathode-grid gap coupled to one of said waveguides at a point spaced transversely from the center line thereof, and a grid-anode gap directly opposite said cathode-grid gap and coupled to the other of said waveguides on the center line thereof, and means for establishing a standing electrmagnetic wave in said one waveguide and extracting energy from said other waveguide.

6. Radio frequency apparatus according to claim 5, wherein the means for periodically loading said waveguides includes a passive capacitive element positioned midway between each adjacent pair of space-charge control triodes in each said waveguide, the capacitive elements in each waveguide being in concentric and opposite relationship to each other, and along the center line con taining the said triodes.

7. A multiple beam radio frequency apparatus comprising a pair of adjacent spaced parallel longitudinally extending waveguides, each said waveguide being periodically loaded by means including a row of a plurality of alternate equally-spaced space-charge control tetrodes and passive capacitive elements, said tetrodes each including a cathode-control grid gap coupled to one of said waveguides at a point spaced transversely from Ithe center longitudinal axis thereof and an opposite screen grid-anode gap coupled to the other of said waveguides along the 1ongitudinal axis thereof, and means for establishing a standing electromagnetic wave in said one waveguide and eX- tracting energy from said other waveguide.

8. A multiple beam radio frequency apparatus according to claim 7, wherein the means for periodically loading said waveguides includes a row of passive capacitive element positioned midway between each adjacent pair of space-charge control tetrodes in each said waveguides, the said capacitive element in each waveguide being in opposite and concentric relationship to each other.

9. A multiple beam klystron apparatus comprising in combination,

(a) a pair of adjacent input and output longitudinally extending waveguides of substantially rectangular and identical cross-section,

(b) each of said waveguides being periodically loaded by a row of alternating equally spaced plural spacecharge control devices and plural passive capacitive gap elements,

(c) said waveguides being positioned in transverse olfset lrelationship to eachother,

(d) each of said space charge control devices including a cathode-grid gap in said input waveguide and anodegrid gap in said output waveguide,

(e) said row of space charge control devices having the anode-grid gaps thereof positioned in a longitudinal plane extending through the longitudinal axis of said output waveguide,

(f) said row of space charge control devices having a cathode-grid gap thereof in concentric and opposite relationship to said anode-grid gap and positioned in said input waveguide -so that the said cathode-grid gaps are positioned in a plane extending through the longitudinal axis of said input waveguide and parallel to the said longitudinal plane of said output waveguide,

(g) means establishing a standing electromagnetic wave in said input waveguide having an electrical eld maxima occurring at each said space-charge control device ,and a minima occurring at each said passive gap element ltherein whereby an amplified electromagnetic wave is induced in said output waveguide corresponding to said wave in said input waveguide,

(h) and output means for extracting radio frequency energy from said output waveguide.

References Cited by the Examiner UNITED STATES PATENTS 2,353,742 7/ 1944 McArthur 315-516 2,745,910 5/1956 Dehn 333-83 X 2,899,647 4/ 1959 Willwacher etal. 333--83 X 2,920,229 1/ 1960 Clarke 315-516 2,920,286 1/ 1960 Havstad 333-83 X HERMAN KARL SAALBACH, Primary Examiner.

ARTHUR GAUSS, S. CHATMON, JR., Examiners.

Claims

1. A MULTIPLE BEAM RADIO FREQUENCY APPARATUS COMPRISING A PAIR OF PARALLEL RESONANT INPUT AND OUTPUT WAVEGUIDES EACH PERIODICALLY LOADED BY ALTERNATE SPACE-CHARGE CONTROL DEVICES AND PASSIVE CAPACITIVE ELEMENTS, SAID DEVICES EACH INCLUDING A CATHODE-GRID GAP COUPLED TO ONE OF SAID WAVEGUIDES AND A CORRESPONDINGLY DIRECTLY OPPOSITE GRID-ANODE GAP COUPLED TO THE OTHER OF SAID WAVEGUIDES, MEANS FOR ESTABLISHING IN SAID ONE WAVEGUIDE A STANDING ELECTROMAGNETIC WAVE HAVING AN ELECTRIC FIELD MAXIMA OCCURRING AT EACH CATHODE-GRID GAP AND A MINIMA OCCURRING AT EACH SAID PASSIVE ELEMENT THEREIN, WHEREBY AN AMPLIFIED ELECTROMAGNETIC WAVE IS INDUCED IN SAID OTHER WAVEGUIDE CORRESPONDING TO SAID WAVE IN SAID ONE WAVEGUIDE AND HAVING ELECTRIC FIELD MAXIMA AND MINIMA OCCURRING, RESPECTIVELY, AT EACH GRID-ANODE GAPS AND PASSIVE ELEMENTS THEREIN, SAID WAVEGUIDES BEING POSITIONED IN ADJACENT RELATIONSHIP SO THAT THE CNETER LINE OF ONE IS IN SPACED PARALLEL AND TRANSVERSE RELATIONSHIP TO THE CORRESPONDING CENTER LINE OF THE OTHER, SAID SPACE CHARGE DEVICES BEING POSITIONED AND EXTENDING INTO EACH SAID WAVEGUIDE SO THAT EACH SAID DEVICE IS ALONG THE CENTER LINE OF SAID ONE WAVEGUIDE BUT TRANSVERSELY SPACED FROM THE SAID CORRESPONDING CENTER LINE OF SAID OTHER WAVEGUIDE AND MEANS FOR EXTRACTING RADIO FREQUENCY ENERGY FROM SAID OTHER WAVEGUIDE.