US2653272A

US2653272A - Ultrahigh-frequency generator

Info

Publication number: US2653272A
Application number: US582917A
Authority: US
Inventors: Ramo Simon
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1945-03-15
Filing date: 1945-03-15
Publication date: 1953-09-22
Anticipated expiration: 1970-09-22
Also published as: GB696810A

Description

Sept. 22, 1953 s. RAMO ULTRAHIGH-FR* EQUENCY GEIEERATGR Filed March 15, 1945 Inventor:

Flam o, 5.1% tomey Slmon b 17%? y His 0 Patented Sept. 22, 1953 ULTBAHIGH-FREQUENCY GENERATOR Simon Ramo, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application March 15, 1945, Serial No. 582,917

'1 Claims. (Cl. 315-) My present invention relates to ultra high frequency systems and it has for its primary object the provision of a new and improved'generator of waves of extremely short length.

In the design and construction of oscillators for generating waves of extremely short length of the order of one or two millimeters, difliculties have been encountered because of the progressive deterioration of the usual methods of using electrons to produce amplification, both because of the short transit times of the electrons and of the very large ohmic losses in the circuits. An even more important limitation is the difficulty of bringing the'resonating structure of the generator in close proximity with a suflicient number of electrons. Essentially,v the resonators employed in such generators are closed chambers with holes or apertures which permit electrons to pass therethrough. The amount of current required for the excitation of such resonators when one attempts generation of waves having a wave length of the order of one millimeter is too great for the relatively small region through which this current is permitted to pass. Thus, for example, the current required for the generation of wave lengths of one millimeter is approximately the same as that required for the generation of wave lengths of one centimeter. However, when a resonant structure of the usual type is reduced to the size required for the one millimeter wave there is not sufiicient space available for passage of a current of the magnitude required to excite the resonator.

It is another object o1 my invention to provide a new and improved ultra high frequency resonant circuit for use in the generation of extremely short wave lengths.

It is a further object of my invention to provide a new and improved ultra high frequency electron discharge device.

It is still another object of my invention to provide a new and improved ultra high frequency generator of the reflex oscillator type.

It is a still further object of my invention to provide a new and improved ultra high frequency resonant circuit adapted to be enclosed in an electric discharge device and having multiple circuits for generating large amounts of short wave energy.

It is still another object of my invention'to provide a new and improved ultra high frequency device for generating waves of extremely short wave length and in which the generation of longer waves is prevented.

It is a still further'object of my invention to provide a new and improved grid structure for an ultra high frequency electron discharge device.

Briefly stated, my invention consists in the employment in an ultra high frequency generator of the reflex oscillator type of a porous resonating structure which can be substantially saturated with the-electrons and in which the resonant structures are formed from very thin wires, the wires being constructed in a network so that the resonant system is multiple in character, the resonator being divided into a large number of short wave length cells by the network of fine wires.

For a better understanding of my invention,

reference may be had to the following description taken in connection with the accompanyand side views, respectively, of a single resonator of the multiple resonator of Fig. 2; and Fig. 5 is a schematic illustration of an ultra high frequency system employing the short wave generator of Fig. 1.

In the portion of the electrode structure of a high frequency generator illustrated in Fig. 1, there is shown a source of electrons in the form of a cathode I having a flat disk emitting surface and heated by a suitable filament 2. Electrons emitted by the cathode Iare focused by a focusing electrode in the form of a grid 3 supplied with suitable negative potentials with respect to the cathode I. The focused electrons are directed toward a reflector collector electrode 4 and, in their passage toward the reflector 4, pass through a multiple resonator structure comprising two layers 5 and 6 of fine parallel wires separated by a layer I of transverse wires. The electrode elements described above are enclosed in an envelope indicated schematically by the numeral 1a.

The construction of the grid resonator 5-4 may best be understood by reference to the perspective view of Fig. 2. The fine parallel wires 5 and 6 form the bottom and top layers, respectively, of a nearly rectangular cross section wave guide resonator, while the transverse wires I form the sides of such a guide. The wires I like:-

wise function to short-circuit the parallel wires,

aosas're 3 I; 6 at the point of intersection.- The spacing between the parallel transverse wires 1' is made equal to a multiple of a half wave length at the desired operating frequency of the oscillator.

Figs. 3 and 4 show the vertical and side views, respectively, of a single half wave length open wire line resonator of the multiple resonator structure of Fig. 2. As is indicated, the electron stream 8 from the cathode i of the discharge device passes on both sides of the individual half wave length open lines. Since the wires 5, 6 are spaced relatively close together, the electrons of the stream have 'a more eflective coupling with the individual resonators of the multiple resonator structure, the space in each of the rectangular openings being substantially completely saturated with electrons and substantially every electron is actively coupled with the resonators, i. e., every electron has a direct influence or excitation effect on the resonators. Thus, in the complete tank circuit formed by the grid wires 5, 6, I, there is a greater volume of space available for the active space charge, thus allowing larger ultra high frequency currents of extremely short wave lengths to be generated.

The electric discharge device of Fig. 1 operates generally according to velocity modulation principles, the electron beam from the cathode I beingivelocity modulated periodically so that successive groups of electrons are alternately accelerated and decelerated, tending to group the electrons in the component parts of the beam after these parts have traversed the velocity modulation gaps. The particular form of electric discharge device described operates in accordance with reflex principles. Thus, after undergoing velocity modulations, electrons are given an opportunity to assume a charge density distribution incident to the effect of the velocity modulation and are reversed in the directions of travel to reenter the short wave length cells of the cavity resonators, delivering energy to the electromagnetic fields thereof.

v In the device of Fig. 1, the electron beam is established by virtue of the unidirectional potential impressed between the resonator -1 and the cathode I from any suitable source of voltage, such as the battery 9. The electrons of the electron beam initially assume the velocity determined by the accelerating potential impressed upon the grid wires 5'|. A negative potential I ments 1.

with respect to the cathode disk I is impressed on the focusing grid 3 which tends to direct the electrons of the beam into component parts, illustrated by the arrows ill, which pass through the parallel gaps formed in the grid wires 5 and 6. As they pass through each of these rectangular openings in the grid structure 5-1, the electrons excite each of the individual resonators toset them into oscillation and establish across the gaps between the wires 5, 6 an alternating ultra high frequency potential incident to the electromagnetic field which exists within each of the individual resonators. By virtue of the alternating nature of this potential, electrons, which are in the region between the planes of wires 5, 5 during periods of time when the wire 5 is positive with respect to the wire 6, will undergo an acceleration. Consequently, the electrons, after traversing the grid structure, proceed into the region of the field produced by the retarding reflector collector electrode 4. The potential of the electrode 4, furthermore, may be negative with respect to the cathode, as well as being negative to the resonator structure, such negative potential 4 being supplied by any suitable source of voltage, such as the battery II. The distance which the electrons proceed in their path beyond the grid 5 is a function of the kinetic energy of each electron, this kinetic energy being. determined by the voltage used to accelerate the electrons. The electrons are reversed by the potential of the electrode 4 to re-enter the cavity resonator and deliver additional energy to the resonator according to reflex oscillator principles.

One of the advantages of the resonator structure described above is that there is greater utilization of the volume of space between the cathode I and the reflector electrode 4 for the active space charge, thus permitting the generation of larger currents of extremely short wave length. In the operation of the oscillator, the gap at which velocity modulation takes place receives its high frequency voltage from each of the given individual resonator elements constituted by the portions of grid wires 5, 6 between the short-circuiting elements 1.

An additional advantage of the resonator structure illustrated is the fact that this particular arrangement eliminates the possibility of gen-- erating oscillations at a wave length longer than the distance between the short-circuiting ele- The structure, therefore, is especially suited for generation of waves of extremely short length, viz., of the order of a few millimeters. Moreover, in the multiple resonator structure, there is no problem of strapping or joining the individual resonators, the wires 1 functioning both as such connectors as well as short-circuits for lower frequencies. The grid structure itself is basically very simple and may be constructed by the windingof parallel wired grids.

In Fig. 5, there is illustrated schematically an ultra high frequency system which is particularly adapted for communication systems employing very high frequencies, as well as radar imaging systems and systems for meteorological investigations. In this system, an electronic discharge device of the form shown in Fig. 1 and having an enclosing envelope 1! is placed at the focal point of a parabolical reflector l3 and the leakage by radiation from all of the multiple resonators of the grid structure of the device is utilized to form a beam directed by the reflector i3.

While I have shown particular embodiments oi. my invention, it will of course be understood that I do not wish to be limited thereto since various modifications may be made, and I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An ultra high frequency oscillator comprising an electric discharge device having a cathode, a reflector electrode, and a resonant structure located between said electrodes, said structure comprising two layers of parallel wires forming a plurality of parallel connected sections of open wire transmission lines, and transverse conductors disposed between said layers at points spaced apart by a distance equal to an integer number times a half wave length at the desired operating frequency of said oscillator.

2. An ultra high frequency electron discharge device including electrode means for establishing an electron discharge and an electron pervious resonant electrode structure positioned in the path of said discharge and comprising a plurality of spaced conducting loops each positioned in a plane parallel to the path of said discharge, said loops being electrically resonant at the desired operating frequency of said device.

3. An ultra high frequency electron discharge device including electrode means for establishing an electron discharge and an electron pervious resonant electrode structure positioned in the path of said discharge and comprising a plurality of spaced rectangular conducting loops each positioned with its plane parallel to the path of said discharge, said loops being electrically resonant at the desired operating frequency of said device.

4. An ultra high frequency electron discharge device including a cathode and an electrode for establishing an electron discharge in said device, and a resonant electrode structure in the path of said discharge comprising a plurality of layers of spaced wires, each wire in each layer being in alignment with a corresponding wire in another layer, the wires in each said layer being spaced apart to permit the passage of electrons through said layer and being positioned transversely to the path of electrons in said discharge, said wires forming multiple resonators electrically resonant at the operating frequency of said device.

5. An ultra high frequency electron discharge device including a cathode and an electrode for establishing an electron discharge in said device, and a resonant electrode structure in the path of said discharge comprising a plurality of parallel layers of spaced parallel wires, each wire in each layer being in alignment with a corresponding wire in another layer, ,the wires in each said layer being spaced apart to permit the passage of electrons through said layer and being positioned transversely to the path of electrons in said discharge, said wires forming multiple resonators electrically resonant at the operating frequency of said device.

, 6. An ultra high frequency electron discharge device including means for establishing an electron discharge and a resonant electrode structure positioned in the path of said discharge comprising a plurality of layers of spaced wires positioned transversely to the path of said discharge, the wires in each said layer being spaced apart to permit the passage of electrons through said layer and being aligned with corresponding wires in the other layer, and conductive means disposed between said layers shortcircuiting corresponding wires in each of said layers at predetermined longitudinally spaced points thereof.

7. An ultra high frequency electron discharge device including means for establishing an electron discharge and a resonant electrode structure positioned in the path of said discharge comprising a plurality of parallel layers of spaced parallel wires positioned transversely to the path of said discharge, the wires in each said layer being spaced apart to permit the passage of electrons through said layer and being aligned with corresponding wires in the other layer, and conductive means disposed between said layers shortcircuiting corresponding wires in each of said layers at predetermined longitudinally spaced points thereof.

SIMON RAMO.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 22,580 Nouromtsefi et al. Dec. 19, 1944 1,353,976 Stoekle Sept. 28, 1920 1,465,381 Trimble Aug. 21, 1923 1,666,071 Perryman Apr. 17, 1928 1,844,319 Hatt -l Feb. 9, 1932 2,043,659 Herriger June 9, 1936 2,087,252 Gumi July 20, 1937 2,105,924 Mendenhall Jan. 18, 1938 2,115,866 Lux May 3, 1938 2,205,475 Hollmann June 25, 1940 2,244,747 Varian et a1 June 10, 1941 FOREIGN PATENTS Number Country Date 560,982 GreatBritain May 1, 1944