US2671857A - Micro-microwave generator - Google Patents

Description

r h e. 40,...

March 9, 1954 Filed Feb. 11, 1944 l I OSCILLATOR' AMPLIFIER z H 0 I.

. llll J. M. CAGE MICRO-MICROWAVE GENERATOR 2 Sheets-Sheet l INVENTOR. dHA/M 6465,

March 9, 1954 CAGE 2,671,857

MICRO-MICROWAVE GENERATOR Filed Feb. 11, 1944 2 Sheets-Sheet 2 OSClLLATPR VIM/v.44. C465,

Patented Mar. 9, 1954 UN I TED STAT ES FAT EN T OFFICE 2,671,857 MICRO-MICROWAVE GENERATOR John M. Cage, Upper Montclair, N. J. Application February 11, 1944, Serial No. 521,950

5 Claims.

This invention relates generally to electromagnetic wave generators, particularly for the wave length region between presently known microwaves, on the one hand, and infra-red on the other, or in other words, in the mega-megacy'cle region. The present invention may be characterized generally as dealing with improvements and refinements in the type of micro-microwave generator disclosed in my copending application entitled Radiovision System, filed August -30, 1943, Serial No. 500,577. As more fully disclosed in said copending application, such a generator is employed in a system designed to detect or visualize objects obscured by darkness, fog, dust, haze, or the like, the generator being utilized, for instance, to direct a beam of generated waves of micro-micro dimensions to the field of view, and a suitable receiver device being provided which is designed to respond to rays reflected back from objects in the field of view. Or, as another instance, the receiving device may respend to a beam received directly from the generator; for example, a receiver carried by an airplane may receive waves radiated from generators outlining or indicating a landing strip.

The generator comprises, generally speaking, a multiplicity of minute metal particles mounted on an insulation base, and periodically charged by a suitable high voltage, and then permitted to discharge. During the discharge, the particles oscillate at their own resonant frequency, and in this oscillating state, generate micro-microwaves which may be reflected or beamed to the field of view. The particles oscillate at a resonant frequency governed by their size, and it is hence possible to generate micro-microwaves of various wave lengths by choosing particle sizes of various gradings. A particle size of approximately one hundred mesh results in generated frequencies of approximately two million megacycles', such as are suited to the purposes at hand, being not seriously interfered with by fog, snow, and the like. is given, or course, as merely typical of the invention, and not as limitative thereoi i.

The general object of the present invention is the provision of an improved and relatively highpower micro-microwave generator of the type indicat'ed.

With this brief preliminary outline of the subject in mind, the invention, including its various specific objects, features, and accomplishments, will be most readily understood by referring to the accompanying drawings and detailed description, disclosing one present preferred and illustrative embodiment thereof.

In the drawings:

Fig. l is a diagram showing one form of improved generator and an energizing therefor;

Fig. 2 is a longitudinal section through the generator, the View being somewhat diagrammatic in nature;

Fig. 3 is a detailed sectionon line ti 3 oi 2';

Fig. 4 is a vertical sectional view 'snownrg the generator tube mounted Within a parabolic re-- fie'c'tor;

Fig. '5 shows a modified generator aha energiz ing system;

Figs. 6 and 7 show further modified generators in accordance with the invention; and

Figure -8 is a section on line B -8 of Figure 'l.

Referring first to the embodiment of 14, the generator includes a generator tube 'll) com prising an evacuated envelope H widen mounted a fil'ainent {2, a grid l8, a'plate or anode l4. overlying the plate is an insulation element I 5, and mounted on the latter, on itsrace away from the plate It, is a layer [6 of fine metal particles or filings, arranged to be insulated frorn one another. 'lihe wave length that will be gen erated depends largely upon the particle size and hence may be varied to suit requirements by choice of the particle size employed. Using, Alnico metal and a particle size of amino ima'tely the order or one hundred mesh, I have roduced wave lengths in the approximate region of 153 mu, or in other words, of around two million megacycles. (ionta'caing and connectedto this layer of metal particles is a connector trip or element II. By means presentl to be described, a high voltage is periodically between the plate M and the connector strip H, whereby the particles are subjected to a voltage gradient and hence become charged. Each metal particle becomes in effect a part of a condenser plate, and thus assumes a high charge. When the charging voltage is subsequently dropped or interrupted, the particles dis charge and are setinto a state of oscillation, generating the desired micro-microwaves, which are picked up and utilized as later to be described.

In Fig. 2, I have shown a present preferred form of generator tube in accordance with the invention, which will now be described in more detail. The filament 12, as indicated, of a double helic'ally wound type, and has leads 2i and 22 extending through the base end of the envelope H. The grid l'3 is illustratively shown as comprising a helix, mounted on supports 23 and M, to one of which is connected a grid lead 25' extending through the base end of the envelope. The plate I4 comprises a sleeve surrounding the grid, and mounted on supports 28, which extend through the head end of the envelope and have connected thereto the plate lead 29. The insulation element I5 illustratively comprises a sleeve mounted on the cylindrical plate l4, and this sleeve may be made of a suitable ceramic substance such as porcelain. The metal particles are mounted on the exterior surface of the sleeve [5. They may be imbedded directly in the surface of the sleeve, or cemented thereto in any suitable manner. For instance, they may be mounted on the sleeve by incorporating them in a coating of glaze applied thereto. One preferred method of producing the layer consists in spraying the ceramic sleeve with a solution of colloidal silver and then firing below the melting point of silver, no glaze being used. The metal particles of the final layer are closely spaced from one another, or in contact; they may be regarded either as surface insulated from one another, or as in conductive relation with one another, but with small resistances between particles.

The particle connector element or strip I! which is in electrical contact with the particle layer, extends lengthwise of the sleeve [5 and contacts or overlies a band of particles It. It may be sealed to the ceramic sleeve by a coat of glaze. The connector strip l! is connected by a short lead 30 to a support 3| mounted in the base of the envelope and provided with an exterior connection lead 32. I

The power of the generator is increased by use of a metal plate 36 extending longitudinally along the outside of the sleeve l5 at a point diametrically opposite from the connector strip l1, and it is mounted on and electrically connected to the particle layer It by means of a connector strip 31, which may be similar to the connector strip l1. This connector strip 3! and the plate 36 are not connected to the external circuit.

The present illustrated energizing system for the generator tube is shown more particularly in Fig. 1. The filament leads 2| and 22 are energized from the secondary of a step down transformer 40, the primary of which may be supplied with current from a 120 volt line. As here shown, the secondary of this transformer is center-tapped and connected to the lead 32 which connects with particl layer connector strip I1.

The external plate and particle connector strip leads 29 and 32 are supplied with a suitable source of high direct current voltage, for instance, twenty-five to thirty kilovolts. This direct current power may be obtained from any suitable source, as for instance from a suitable rectifier, such as the one conventionally indicated generally by the numeral 42.

An oscillator 50, for instance of 100 kilocycles, though this is not to be taken in a limitative sense, has its output amplified by a suitable vacuum tube amplifier 5|, and the output terminals of the latter are connected one to generator grid lead 25, and the other to particle connector strip lead 32. The oscillator 50 is preferably either of a saw-tooth or square wave type, producing steep wave front voltage waves, or in other words, producing voltage changes within minimum tim intervals.

The direct current power supply 42 normally impresses a high voltage between the plate M of the generator tube and the particle connector strip l7, thus subjecting the metal particles to an extremely high voltage gradient, and causing them to be charged to high potentials. This charging voltage to which the metal particles are subjected is periodically varied in accordance with the output of the oscillator 50, which will be seen to be improssed across the filament I 2 and grid l3.

When the grid voltag relative to the filament (governed by the amplified oscillator voltage) swings more negative, th filament to plate space current of the tube is decreased or interrupted, and the full D. C. charging voltage is impressed between the plate and particle layer [6. When the grid voltage then swings back (becomes less negative or more positive) a substantial space current flow from filament to plate, and it will be seen that this space current flow is in parallel with the condenser formed by the plate and particle layer, with the result that the voltage drop across the latter is substantially decreased, so that the charged particles are permitted to discharge, and are thus set into oscillation. By employing an oscillator 50 of saw-tooth or square Wave characteristics, the voltage impressed between the charging plate and the particle layer can be increased and/or decreased within minimized time intervals. I have found it of advantage to charge the particles with a relatively steep front voltage wave, and it is likewise of advantag to discharge the particles by removing the charging voltage in a minimum time interval. Obviously, use of a saw-tooth Wave will permit the particles either to be charged or discharged with a steep sided Wave, and use of a square wave oscillator will permit both.

The plate 36 acts as a kind of capacitor or energy distributing element, which tends to cause an equal distribution of potential over the pe riphery of the particle surface, and is found in practice to increase the radiation from the generator.

The generator tube of Fig. 2 is shown in Fig. 4 as mounted within a parabolic reflector 60, being understood to be located with its particle layer in the region of the focal point of the refiector. The reduced rearward end portion of the tube is shown as fitted within an aperture at the back of the reflector, While the plate lead 29 is shown as passing through the wall of the reflector by means of an insulator 6 I. l

The discharging metal particles of th particle layer I6 are set into intensive oscillation, as previously described, and the frequency of this oscillation will vary depending principally upon particle size, all as heretofore described. The oscillating particles generate micro-microwaves" which are radiated therefrom, and these are reflected by the parabolic reflector 60 and beamed to the field of vision.

It will be evident that my wave generator is in the nature of a condenser, comprising a condenser plate mounted adjacent one face of an insulation layer and another condenser plate in the form of a particle layer applied to the opposite face of said insulation layer, directly opposite the first-mentioned plate. A connector element then contacts the particle layer. By this arrangement the condenser structure of the generator has a maximum capacity, a maximum potential gradient is established, and each particle assumes a large charge. Each individual particle is charged proportionately to the potential difference between the plate and the particle. The resistance between particles is relatively small, and under the high charging voltage, electrical activity oscillating over the particle layer aa'rnesm or over or between the particles, i. e., electricity jumping: from particle. to particle; may. be; ob.- served. during both. charge and discharge.

The charging system for the generator may be or. various types, such ior instance; as that. closed in. my: copending. application. entitled Ra.- d'iovisionsystem, SerialNo. 500,577, filed August 30-, 194431,. in. which case. a space. current not. being required, the evacuated envelope nught be omitted. Other typical. modifications in both the charging systems and the generator will now be described.

Fig. shows schematically a generator without an envelope, and a modified charging system. The generator comprises an insulation sleeve 50, on the outside surface of which is alayer 5| of metal particles forming one plate. of the condenser structure. The other plate consists of. a metallic sleeve 52 contacting the inside surface of sleeve 50. Contacting particle layer 5| is a metallic connector strip 53, while diametrically opposite from the latter is a metallic strip 54 carrying a plate element 55, the latter elements not being connected into the external circuit- A suitable source of direct current power is provided, here being shown as in the form of a rectifier-filter combination 5B. The positive output terminal of the latter is connected by a lead 51 to the plate 60 of a triode Bl. The negative output terminal of the DC power supply is connected by lead 64 to plate 52. An oscillator 65, preferably either square wave or saw-tooth, has one output terminal connected by lead 66 to the grid 61 of triode BI, and its other output terminal connected by lead 68 to the filament or cathode 69 of said triode. A C-bias battery may be provided in the filament-grid circuit of this triode, as indicated. Particle layer contact strip 53 is connected by lead H to cathode lead 68, which is grounded.

The wave generator will be seen to be included as a condenser in series in the plate circuit of triode 6|. The output saw-tooth or square wave from oscillator 65 impressed on the grid of the triode controls the total voltage and causes abrupt voltage changes across the generator, which periodically charge the particles of the layer 5| and permit said particles to discharge at their resonant frequency.

I have also shown in Fig. 5 the optional use of a variable tuning inductance connected across the condenser structure of the generator. This inductance permits the generator circuit to be tuned to resonance, whereby an optimum delivery of power from the generator may be gained.

I have now disclosed one case (Figs. 1-4) wherein the generator is enclosed in an evacuated envelope, and a second (Fig. 5) wherein the generator is not so enclosed. Enclosure in an evacuated envelope, while not essential, is advantageous in that under such conditions the particles will accept a higher charge before discharge takes place. On the other hand, use of a generator enclosed within an envelope in which a small amount of gas, like neon, is introduced is advantageous because of lowered resistance between particles, which is conducive to increased duration of the oscillatory discharge.

In Fig. '6 I have disclosed a modified generator enclosed Within a glass or ceramic envelope 80, which may be either evacuated, or gas containing. This envelope is here illustratively shown as in the general form of a parabola, with a 6; closed tnontwal'l 8t... 'I-heinside of the paraboliir sidezwalLM iscoatediwith' alayerlnot metazli. particles, which are. contacted toward the front end wall. of. the envelope by a metallic band 84:. corresponding to the plate at of. Fig. 2; A.- com. tact. button; 85: at the: rearward end. of the en: velope: makes. connection with the; particle layer". and anoutside; metallic; plate or'shell $6} contacts the, outside. surface. of the parabolic side wall. The external connections 81 and 88 are made to button 85. and shell as, respectively. It willbe evident that the genera-tor of Fig. (imay be used, for example, in such a circuit as is shown in 1 Fig. 5.

Finally,- in Figs; 7 and 8-, I- have shown asimplified but-elfective generatorstructure in accordance with the invention, comprising a flat insulation plate ametallic condenser plate, 91" contacti'ng one surface thereof, a particle layer 92 contacting the opposite surface thereof, and a contact strip 63 extending transversely across the center of layer 92 and making contact therewith. Metal strips 94, parallel to strip 93, contact the upper and lower edges of the particle layer. External connections 95 and 96 are made to strip 93 and plate 9!, respectively. It will be evident that here again, as in each of the earlier described embodiments, the particle layer comprises one plate of a condenser structure, whereby the individual particles may be charged to optimum potentials, and will hence deliver optimum power upon resonant discharge.

The invention has now been described by way of a specific disclosure of several present illustrative embodiments thereof. It will be understood, however, that this is for illustrative purposes only, and that various changes in design, structure, and arrangement may be made without departing from the spirit and scope of the invention or the appended claims.

I claim:

1. A wave generator embodying an insulation layer, a layer of metal particles adjacent one face of said insulation layer, a metal plate adjacent the opposite face of said insulation layer, and a connector element overlying and contacting said particle layer immediately opposite an area of said plate.

2. A wave generator embodying an insulation sleeve, a layer of metal particles adjacent one face of said sleeve, a cylindrical metal plate adjacent the opposite face of said sleeve, and a connector element overlying and contacting said particle layer immediately opposite said cylindrical plate.

3. A wave generator embodying an insulation layer, a layer of metal particles adjacent one face of said insulation layer, a metal plate adjacent the opposite face .of said insulation layer, a connector element overlying and contacting said particle layer immediately opposite an area of said plate, and an evacuated envelope enclosing said members.

4. A wave generator system embodying a layer of metal particles, a metallic connector element contacting said layer, a plate parallel to but spaced from said layer, an electronic tube including anode, grid and cathode elements, an anode circuit for said tube including a source of direct current power and said plate and connector element in series and a source of alternating current impressed across the grid and cathode elements of said tube.

5. A wave generator system embodying a layer of metal particles, a metallic connector element contacting said layer, a plate spaced and insulated from said layer, a tuning inductance connected between said connector element and plate, an electronic tube including anode, grid and cathode elements, an anode circuit for said tube including a source of direct current power and said plate and connector element in series and a source of alternating current impressed across the grid and cathode elements of said tube.

JOHN M. CAGE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,618,499 White Feb. 22, 1927 1,655,270 H1111 Jan. 3, 1928 1,830,175 Podliasky NOV. 3, 1931 1,872,274 Goldsborough Aug. 16, 1932 1,945,039 Hansell Jan. 30, 1934 Number Name Date 1,951,731 Kassner Mar. 20, 1934 1,960,142 De Pam'agua May 22, 1934 1,995,175 Gill Mar. 19, 1935 2,021,907 Zworykin Nov. 26, 1935 2,075,377 Varian Mar. 30, 1937 2,171,980 Hansell Sept. 5, 1939 2,189,985 Hichok Feb. 13, 1940 2,265,796 Boersch Dec. 9, 1941 2,270,479 Schroter Jan. 20, 1942 5, 4 Frundt et a1. Mar. 28, 1944 FOREIGN PATENTS Number Country Date 127,712 Australia Apr. 11, 1932 OTHER REFERENCES Page 123, Phys. Review," vol. 21, 1923, article by McAllister.

Images