US2434508A - Coupling device - Google Patents

Description

Jan. 13, 1948. E. c. oKREss ET Al.

COUPLING D EVICE Filed Sept. 2, 1942 INVENToRs E c', @fr/e555 PazX/YHKP Kaff/sf.

y W/wuk I/vwL ATTORNEY Patented Jan. 13, 1948 2,434,508 ooUrLiNG DEVICE Ernest C. Gkress, Montclair, N. J.,

and Polykarp Kusch, New York, N. Y., assignors to Westinghouse Electric Corporation, Pa., a corporation of Pennsylvania East Pittsburgh,

Application September 2, 1942, Serial No. 457,024

14 Claims.

This invention relates to coupling devices and more particularly to a coupling device for microwave energy, as, for instance, from the source of generation of the energy to a wave guide or other means of transmission of the energy from such source to effectuate its use. The coupling device is in effect a short length of coaxial line with a loop terminal for introduction into the generator, and the present invention is an improvement upon our former application, S. N. 440,274, filed April 24, 1942, entitled Coaxial lines, now U. S. Patent 2.404,085.

Interpositioning of ay dielectric, under ordinary conditions in the path of wave propagation, introduces an impedance discontinuity and consequently a disruption or partial loss of transmitted energy. Yet a dielectric has to be employed in connection with the output means from an evacuated generator to maintain the generator vacuum and at the same time have the protruding part of the output means not under vacuum. The desideratum, not heretofore accomplished, is to transfer the full derivable wave energy from an evacuated chamber to a transmission line or means not under vacuum, and this desideratum constitutes the primary object of the present invent'ion.

Another object of the invention is to accomplish the stated desideratum by a coupling means of improved construction.

A further object of the invention is to transfer the wave energy, with negligible loss, from an evacuated generator to a wave guide not under vacuum.

Again, an object of the invention is to provide a coupling device wherein the wave energy from the generator to the output line is along good conductors.

Yet another object is to provide a coupling device wherein the wave energy from the generator in its travel to the output line is kept out of contact from the metal-to-dielectric seal.

Still further objects oi the invention are simplicity of parts, ease and permanence of assembly, and adaptability to known generators and wave guides.

Additional objects will appear to those skilled in the art both by direct reference thereto as the description proceeds and by implication from the context.

Referring to the accompanying drawing in which like numerals of reference indicate similar parts throughout the several views,

Figure 1 is a longitudinal sectional View of a coupling device embodying the present invention and shown in associated relationship to a generator and a wave guide, and

Figures 2, 3 and 4 are cross sections of said device taken on lines II--II, III- III and IV-IV of Fig. 1 respectively.

In the specic embodiment of the invention illustrated in said drawing, the reference numeral I0 designates a part of a known ultra high frequency generator from which wave energy is derivable through an output provided wtih a loop II situated within a cavtiy I2 of the generator. The interior of said generator, inclusive of said cavity, is evacuated and it is, of course, essential to maintain the vacuum throughout the useful life of said generator. Normally thev loop I I is exposed directly to the vacuum space. In our above-identified application the loop is enclosed in a pocket open to external atmospheric pressure and the pocket inserted into the generator cavity, but such structure interposes a dielectric in the wave path, which is somewhat objectionable from eiciency and other standpoints. However, it has proven to be much more objectionable in the past to nterpose the sealing means within the coaxial line from the loop or at the part of said coaxial line where coupling with another line occurs. This is especially true when, for purposes of taking advantage of Kovar seals, that alloy is employed, it being a poor conductor and to be avoided if possible so far as electromagnetic energy exposure is concerned. Nevertheless, according to the present invention, this type of external sealing is accomplished with a minimum of eciency losses of energy transfer occurring as in the prior art. It should be borne in mind that the immediate desideratum is efficient transfer or conduct of the wave energy from the evacuated cavity of the generator to a hollow wave guide I3 that is not evacuated.

Generally defined, a wave guide is a hollow pipe by means of which electromagnetic energy is propagated from one place to another before its ultimate transmission in free space or utilization in some other instrumentality. A wave guide is characterized by presence of a dielectric, such as air, Within a metallic pipe engirdling the dielectric. The cross-sectional dimensions of the guide have a definite relation to the character of the wave transmitted thereby. Usually wave guides are rectangular in cross section with one dimension greater than the other for purposes o f obtaining the desired mode of oscillation and polarization of the wave that may be transmitted. Accordingly, the wave guide I3 shown is of rectangular cross section, and for convenience of description the longer dimension will be referred to as horizontal and the shorter dimension as vertical, but it is to be understood such designations are arbitrary and not in any sense limitations.

The coupling device per se comprises, in addition to loop above mentioned, a coaxial line of which the center rod I4 is in continuation of one leg of the loop, is of tungsten and projects from the generator to and vertically through the wave guide medially between the side walls thereof. The cooperating tubular portion of the coaxial guide is constituted by a conductive base or mounting thimble I5, as of copper, and by a tube I6, which preferably is also copper, axially alined and projecting upwardly therefrom, both the thimble and the tube having central passages |`I, I8, respectively, of which one is a continuation of the other. The upper end of said tube I6 is substantially at the level of the lower horizontal wall of the wave guide but does not have any contact therewith.

Also projecting from the upper end of said thimble, preferably coaxial with the said tube I6, but of less length than said tube, is a sleeve I9 the upper end of which is sealed vacuum tight to an end margin of a long glass envelope 20 of substantially the same diameter throughout its length as said sleeve. The sleeve and glass envelope are of materials having substantially the same coeicient of expansion and by preference the glass is borosilicate glass and the sleeve is an alloy of nickel, cobalt, manganese and iron in accordance with disclosure of Patent 2,062,335 of December 1, 1936, to Howard Scott, said material being sold under the trade name of Kovar. This alloy and glass obtain a very rugged seal both because the coefficients of expansion are substantially the same and because of the tenacious adhesion and for the further reason that a fine featheredge is not required. In the microwave art here involved, Kovar has been found inadequate as a conductor under certain conditions, as it is not only highly dissipative but if a large quantity of energy is permitted to flow through the Kovar-glass seal there is a likelihood of failure of the seal and consequent loss of vacuum at the wavelength band of present concern. The construction employed in the present invention requires no flow of micro-wave energy in the Kovar or next to the surface thereof. The ilow of the micro-wave energy is within the passages I'I, I8 between the coaxial rod and its engirdling thimble and sleeve.

As shown, the upper end of thimble I is provided with stepped-down sockets the outer upper one receiving the end margin of the "Kovar sleeve, and the inner-lower one receiving the end margin of the coaxial line tube I6. Both the sleeve and tube are soldered in place in their respective sockets in the thimble, preferably with the use of a gold-eutectic solder indicated applied at 2|, 2|.

Glass envelope 20 extends upwardly through the wave guide and sealed, as with reentrant stem 22 to the central rod I4 which in this showing projects through and above the envelope. Standing upright above the wave guide to which it is attached, is a sleeve-like upper metallic housing 23. The envelope 2i) projects into said upper housing and the protruding end of rod I4 is likewise therein. Also within said housing and located above the envelope is a hollow piston 24 the skirt portion whereof is directed downwardly and is preferably a depth of an odd quarter Wavelength in air of the wave being promulgated. The lower rim portion of the skirt portion of this piston is provided with an outer circumferential bead 25 for frictional engagement with the inside surface of the housing 23. Preferably a plurality of vertical slits 2G in said skirt portion which also cut through the bead and through the lower edge of the skirt permit flexing of the end portions of the piston wall between slits. This construction obtains the desired frictional contact of piston and housing. Within the hollow of said piston and of equal length as the aforementioned skirt portion, is an inner tubular skirt portion 21 also having vertical slits from the lower edge thereof whereby said inner skirt portion will obtain a desired frictional contact with the upper end portion of the central rod I4 where protruding above the envelope. An adjusting screw 28 with its lower end swiveled to the top of the piston projects upwardly with threaded engagement through the housing and retained in adjusted position by lock-nut 29. Said piston is thereby adjustable to occupy a position of a half wave-length above the center line of the wave guide, so that the longitudinal current maximum on the center rod conductor occurs near the central plane of the guide. It may also be here noted that one end of the wave guide may have a closed end 30 a quarter-wave length, referred to the guide, from the said central rod for reecting energy and directing all of the derived energy in one direction in the wave guide. The position of this wall 3!) from the center conductor or rod I4 acts to reduce whatever impedance was established by the setting of piston 24. Generally, however, position of said wall 30 is such that the maximum E-vector in* tensity is established coaxial with the axis of said rod I4 in the guide.

For accomplishing purposes of the present invention electrical continuity between the upper end of coaxial tube I6 and the adjacent wave guide bottom wall is obtained, but by means avoiding physical engagement 0f those parts thereat. The structure employed comprises radially enlarging a definite length of the coaxial tube |6 as at 3| next the upper end of said tube so that the outer peripheral face of the enlargement is substantially in contact with the glass of the envelope. On the outside of the envelope directly opposed to said enlargement, and of equal length, is a metallic ring 32 which is likewise substantially in contact with the glass of the envelope but on the outside thereof. Engirdling the metallic ring 32 is a ring 33 of glass or other material having the same dielectric constant as the glass of the envelope. Mention may be made at this time that While necessity of exaggeration of thicknesses seems to make the axial length of said glass ring noticeably shorter than the enlargement 3|, in actual practice the metal of ring 32 overlying upper end of glass ring 33 is sufficiently thin so that the diierence in lengths is accounted for in compensation for end eifects. The common length of said enlargement, metal ring and glass ring is equal to a quarter wave length, as measured in the dielectric, of the wave energy being promulgated. Observation is made at this time, that the wave-length in a dielectric such as glass is materially shorter than in air, and in the present showing, length of the enlargement and rings represents a single quarter wave-length for the glass dielectric as compared with the depth of the heretofore described piston 24-which-represents asinglequarter wave-length in air.

:Outside -of the glass ering is a lower fhousing '34 of ymetal coaxial with AIthe V'several -parts within and extending from the wave guide i|`3 =to the mounting'thimble |5 and secured to lboth, asby soft solder 35, 35. The space below the rglass ring within the said 4lower housing 34 iis noncritical, the housing only fforming ythat space `incidental toits function `of maintaining `proper relationship vof generator and vwave guide.

v-In operation, micro-wave energy is picked up by loop I-l from the generator or other source, land is'guided along the passage formed fbetween tube It* and center rod I4 fior-ming the lcoaxial line. At the gap area 31 at the -upper :end of tube t5 a -verylcw impedance lis encountered 4as contrasted with a highimpe'dancerat the-gaplarea 38 lat the lower end of enlargement A3J by 'virtue ofthe quarter wave-'length annular chamber 33, mathematical proof oi which is evident to -those versed in the micrc-waveart. 'Theresulting -e'fiect, by virtue of this operation of 'the limpedance section constituted 'by -said enlargement, rings and associated part ofthe envelope, -is effectof :electrical continuity,7 between theuppercen'd ofthe said tube I'G and the encircling part of 'the metallic ring 132 and wave guide :wall .at 531. Thus the low impedance at r31 :is utilized to `obtain full vpower coupling from the vconcentric vline of ithe coupling device to the wave guide.

I Since-the various details of. construction,-as-we1l as the :precise relation and functioningof parts, :are-subject to variation and change without departing from the .inventive .concept or-"scope of the invention, it `fis intended Ithat all matter contained in the specication .or illustrated in the drawing. shall be interpreted as .exemplary and :notina limiting sense. vItiisalso tobe understood that the following claims ,are intended tocover all of the generic and specific lfeatures .of the invention herein shown and described -and `all statements of-.the scope ofthe invention herein set forth as a matter of language )which :might be said to fall therebetween.

We claim:

1. A coupler device comprisingahollow'mounting thimble, a, sleeve projecting axially from said thimble. an envelope sealed to said sleeve, a central.coaxial rod within said sleeve and envelope, and a conductive tube Awithin said sleeve and envelope secured at one end ,tosaid thimble and projecting through and beyond said sleeve a clistance more than a Quarter wave-'length ofthe wave energy promulgated therethrough.

2. A coupler device comprising-a-hollow mounting thimble, a sleeve projecting axially from said thimblean envelope sealed to -said sleeve, a central coaxial rod .within said sleeve and envelope,

alconductive tube withinsaidsleeve and envelope secured atene end to -saidthimble and projecting through and beyond said sleeve a-distance more than a ,quarter wave-length of the wave energy promulgated therethrough, and -a wave -guide ytraiflsverse to saidtube -and rode-and substantially at the .level .-of the -end -of sa'id Jtube away Afrom the said thimble.

3. A coupler device comprising a hollow mounting thimble, a sleeve projecting axially from said thimble, an envelope sealed to said sleeve, a central coaxial rod within said sleeve and envelope, a conductive tube within said sleeve and envelope secured at one end to said thimble and projecting through and beyond said sleeve a distance more than a quarter wave-length of the wave energy promulgated therethrough, :a .wave guide transverse to said tube and rod and substantially zat the ylevel .of the end of :said tube 4away Efrom the -said thimble anda housing sealing the tube and sleeve said `housing being attached vto the said thimble at one .end and to the wave guide at the other end.

y4. Acoupler device comprising a hollow mounting thimble, a sleeve projecting axially :from said thimble, an envelope sealed to said sleeve, a central coaxial rod within said sleeve and envelope, aconductive tube ywithin said sleeve and-envelope secured at oneend to said thimble and projecting ,through and beyond said sleeve a distance more V,than a quarter wave-length of the wave energy .promulgated therethrough, `a Wave guide transverse to said tube and rod and substantiallyat the ,level of the end of said tube away from .the said thimble, a housing surrounding the tube :and sleeve said housing being attached to the ,said .thimble at one end and to the wave guide -at the'other end, and impedance matching means situated at the bottom of the Wave guide and between the said housing and envelope.

5. A ,coupler device Acomprising a coaxial line having va rod and a tube of which the rod projects upwardly beyond the tube, an envelope sealin g the varea occupied by the tube and part of the area occupied by the rod, said rod projecting through said-envelope, a wave guide, said rod and'envelope-projecting through said wave guide, said-waveguide having an end wall an odd quarter Wave-length ydistance from said rod, and a piston `Opposite the end of said envelope and rod situated substantially a half wave-length 4from said -wave guide.

6. A coupler device comprising a coaxial v'line having a rod and a tube of which the rod project'supwardlybeyond the tube, an envelope sealingthe area occupied bythe tube and part of the area voccupied by the rod, said -rod projecting through-said envelope, a Wave guide, said rod and envelope -projecting through said wave guide, said wave guide having an end wall an odd ouarter wave-lengthdistance from said rod, a piston op- -`posite the end of said envelope and rod situated substantially a half wave-length from said Wave guide, and means Afor adjusting said piston.

7. A `coupler .device comprising a coaxial line structure having -an envelope, said structure prokviding a central rod anda tube within said envelope ifor transmission of electrical waves of substantially -xed wave length in air and correspondingly :xed `Wave length in the dielectric of -the envelope, :said tube having an enlargement .-nextan end thereof within the envelope, said enlargement thaving a length equal to .an odd quarter Wave length of the wave length in the dielectric of the envelope, and means on the exterior of said envelope constructed and arranged to present 4low impedanceand eiect of electrical continuity to said end of said tube enlargement for transmission ofvelectrical energy from the interior to ftheexterior of said envelope.

18. A coupler device comprising a coaxial line structure having an envelope, said structure providing a central rod and a tube Within said envelope for transmission of electrical Waves of substantially xed wave-length in air and correspondingly xed wave length in the dielectric of the envelope, said tube having an enlargement next an end thereof within the envelope, said enlargement having a length equal to an odd quarter wave length of the wave length in the dielectric of the envelope, and means on the exterior of said envelope for transmission of electrical energy from the interior of said envelope, said means comprising a metallic ring and a dielectric ring having substantially the same dielectric constant as the dielectric of the envelope.

9. A coupler device comprising a coaxial line structure having an envelope, said structure providing a central rod and a tube Within said envelope for transmission of electrical Waves of substantially fixed wave length in air and correspondingly xed Wave length in the dielectric of the envelope, said tube having an enlargement next an end thereof within the envelope, said enlargement having a length equal to an odd quarter wave length of the wave length in the dielectric of the envelope, and means on the exterior of said envelope for transmission of electrical energy from the interior of said envelope, said means comprising a metallic ring and a dielectric ring having substantially the same dielectric constant as the dielectric of th'eenvelope and having a length substantially equal to the length of said enlargement.

10. A coupler device comprising a coaxial line structure having an envelope with an outer end, said structure providing a central rod and a tube terminating Within said envelope for transmission of electrical Waves of substantially xed Wave length in air and correspondingly xed Wave length in the dielectric of the envelope, said tube being out of direct contact with said rod, means opposite said tube on the exterior of said envelope for transmission thereto of electrical energy from the interior of said envelope, a metallic housing connected with said tube and extending beyond said outer end of the envelope, and a piston in said housing opposed to the outer end of the envelope for Wave reflection.

11. A coupler device comprising a coaxial line structure having an envelope with an outer end, said structure providing a central rod and a tube terminating Within said envelope for transmission of electrical Waves of substantially xed Wave length in air and correspondingly fixed Wave length in the dielectric of the envelope, said tube being out of direct contact with said rod, means having a length equal to Aan odd quarter Wave length in the dielectric of the envelope said means situated on the exterior of the envelope for transmission thereto of electrical energy from the interior of said envelope, a metallic housing connected with said tube and extending beyond said outer end of the envelope, and a piston in said housing opposed to the outer end of the envelope for Wave reflection, said piston being hollow toward said envelope a depth substantially equal to a quarter wave length in air of the aforesaid Wave length.

12. A coupler device comprising a coaxial line structure having an envelope with an outer end, said structure providing a central rod and a tube within said envelope for transmission of electrical Waves of substantially xed wave length in air and correspondingly xed wave length in the dielectric of the envelope, said tube having an next an end thereof within the envelope, said enlargement having a length equal to an `odd quarter Wave length of the Wave length in the dielectric of the envelope, means on the exterior of said envelope for transmission of electrical energy thereto from the interior of said envelope, a metallic housing connected with said tube and extending beyond said outer end of the envelope, and a piston in said housing opposed to the outer end ofthe envelope for wave reflection. 13. A coupler device comprising a coaxial line structure having an envelope with an outer end, said structure providing a central rod and a tube Within said envelope for transmission of electrical waves of substantially xed Wave length in air and correspondingly xed Wave length in the dielectric of the envelope, Said tube having an enlargement next an end thereof Within the envelope, said enlargement having a length equal to an odd quarter Wave length of the wave length in the dielectric of the envelope, means on the exterior of said envelope for transmission of electrical energy thereto from the interior of said envelope, said means comprising a metallic ring and a dielectric ring having substantially the same dielectric -constant as the dielectric of the envelope, a metallic housing connected with said means and extending beyond said outer end of the envelope, and 'a'piston in said housing opposed to the outer end of the envelope for wave reflection.

14. A coupler device comprising a coaxial line structure having a sealed evacuated envelope, said structure providing a central rod and a tube Within and subject Vto the vacuum of said envelope and having an end within said envelope and out of direct contact'with said rod, and external circuit conductive means opposite said tube on the exterior of said envelope, said means and tube having indirect connection with resultant uncertain impedance of the electrical path along the indirect connection, and said means providing a quarter-wave line shorted at said end of the tube and constructed and arranged to'present low impedance at said end and effect of direct electrical continuity from said tube within said envelope to said means exterior of the envelope and shunting out the said indirect connection and uncertain impedance.

enlargement ERNEST C. OKRESS. POLYKARP KUSCH.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,281,550 Barrow May 5, 1942 2,184,729 Bailey Dec. 26, 1939 2,264,124 Schreiner Nov. 25, 1941 2,167,201 Dallenbach July 25, 1939 2,338,306 Smyth Jan. 4, 1944 2,169,305 Tuniek Aug. 15, 1939 2,144,222 Hollmann Jan. 17, 1939 2,382,217 Fancher Aug. 14, 1945

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