|Publication number||US2557391 A|
|Publication date||Jun 19, 1951|
|Filing date||Oct 7, 1942|
|Priority date||Oct 7, 1942|
|Publication number||US 2557391 A, US 2557391A, US-A-2557391, US2557391 A, US2557391A|
|Inventors||Carl Okress Ernest|
|Original Assignee||Westinghouse Electric Corp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (13), Referenced by (9), Classifications (8)|
|External Links: USPTO, USPTO Assignment, Espacenet|
June 19, 1951 V E. c. oKREss 2,557,391
i COUPLING DEVICE FO MICROWAVE ENERGY Filed Oct. 7, 1942 y 3 Sheets-Sheet 1 INVENTOR E C` O/f/FSS ATTORNEY June 19, 1951 E. c. oKREss COUPLING DEVICE FOR MCROWAVE ENERGY s sheets-sheet 2 Filed Oct. '7. 1942 Rx. w m.
June 19, 1951 E. c. oKREss COUPLING DEVICE FOR MICROWAVE ENERGY K Filed Oct. 7, 1942 3 Sheets-Sheet 5 INVENTOR E'. C. OAT/:'55s
ATTORNEY Patented `lune 19, 1951 UNlTED STATES PATENT OFFICE ooUPLING DEVICE Fon MICRO-WAVE ENERGY f l v Ernest Carl Okress, Montclair, N. J., assigner to Westinghouse Electric Corporation, East Pittsburgh, Pa'., a corporation of Pennsylvania Application October 7, 1942, Serial No. 461,135
8 Claims. (C1. 178--44) 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.
While coupling devices per se are known in the art, difficulties have been experienced in connection therewith both as to the efficiency, as to the tuning ,and as to the mechanical assembly. In this latter respect it has been found diflicult .to construct a frictional coupling device with such accuracy that the metallicparts will not either in assembly or in use introduce strains upon the glass envelope portion and immediately o r ultimately cause a crack or other rupture therein which renders the device inoperative or grossly ineicient as to require discarding the entire coupling device.
It will be recognized by those skilled in the art .that a coupling device is in effect a `short length of coaxial line with a loop o r other terminal for introduction into the generator and that Aconsequently, since the generator is evacuated and the wave guide with which the device is coupled is not evacuated, a .dielectric has to be interposed in the energy path for maintaining the evacuation of the generator. Various schemes have been suggested and tried, and it appears most `effective to extend rthe coaxial pick-up rod portion of the terminal from the generator Y to the wave guide with said `rod `portion passing transversely through the wave guide .and intersecting the center line of the wave guide at right angles, the portion of the rod Within the wave guide constituting what may b e appropriately termed an antenna. To accomplish this desider- `atumy a dielectric envelope, of glass, :issealed at one end to the tubular portion of the coaxial line and is sealed at its other end toa distant part of the rod portion of the coaxial line, said dielectric envelope extending with the rod through the wave guide and the two areas of sealing above mentioned being at oppositeexterior portions of the wave guide. This .construction necessitates that there shall be not only this inechanical attachment to theparts mentioned but, of necessity, means to establish the required .antenna reactance and radiation resistance in order that the waveguide maybe matched to an input having an impedance less than twicethe Aappropriate characteristic Wave guide impedance.
An object .of the invention is to overcome the aforementioned difliculties and to improve the coupling device both mechanically and 'froman leiiiciency standpoint.
'adjustments for the reflecting and tuning means which is entirely outside of t he evacuated area and in operation introduces no movement of the envelope for the evacuated area or of any parts extending ,thereinto Y vStill further objects of the invention are sirnplieitv .of parte, ease and permanence 0i' assembly, and adaptability Ato known generators and wave guides.
Additional objects of the invention 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 drawings in which like numerals of reference indicate similar parts throughout the several views,
Figure 1 isa sectional view longitudinally of my improved coupling device and of a Wave guide with which it is associated;
Figures 2 and 3 are cross sections on lines I-II and III-1.11.1, IBSpeCiiVelY, .Of Figure il;
Figures 4, 5 and 6 are sectional views of the character o f Figure 1, but left partly in elevation, and .each .showing a meded construction;
illustrated in said drawing and referring initially to the construction of YFigures 1, .2 and .3; the reference numeral Ill designates a part of a known ultra-high frequency generator from which waveenergy is derivable through la coaxial line means which includes a current Iprobe or loop vIl ofsuitable shape situated within a cavity I2 of the generator. The interior of said generator, including said cavity, is evacuated and .it isJ of Course, essential .to maintain the vacuum .throughout the useful life of said generator.
Normally the current probe orjloop Il is exposed direetlyte theevaeuated cavity.
The desigieratum istotransfer energy` picked .up by the probe .erleep te .a'hollow waveguide L3 Situated .exterior te the generator `and the hollow of which is not evacuated. Wave guides in `general are known to. the art and constitute e means .by ,Whieh .electromagnetic energy' is prepagatedr from one .place .te .another .befereits ultimate transmission in free space or utilization in some other instrumentality. Usually wave guides are rectangular in cross section with one dimension greater than the other for purposes of obtaining the desired mode of oscillation and polarization of the wave that may be transmitted. The cross-sectional dimensions have a definite relation to the character of the wave being transmitted, but need not be discussed in this specication. Suffice it to say, that the terminal sections here disclosed are suitable for launching the transverse electric, TEoi, mode or Hoi wave. For a more extended discussion of modes and waves involved reference may be made to an article by L. J. Chu and W. L. Barrow, entitled Electromagnetic waves in hollow metal tubes of rectangular cross section published in Proceedings of Institute of Radio Engineers, vol. 26, No. l2, December 1938, beginning page 1520, and of especial interest, page 1532.
The coupling device per se comprises, in addition to current probe or loop I I above mentioned, a coaxial line of which the center rod I4 is the axial portion and is a continuation of the said current probe, that portion of said rod which is within the wave guide being termed the antenna, and that part from the generator to the wave guide being termed the pick-up portion. The rod is of tungsten, copper and/or other suitable metal and projects from the generator to and vertically through the wave guide medially between the side walls thereof thereby intersecting the center line of said wave guide. 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 I5 which preferably is also copper, axially alined and projecting upwardly therefrom, both the thimble and the tube having central passages I1, 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 of substantially the same diameter throughout its length as said sleeve. The sleeve and glass envelope are of materials having substantially the same co-eicient of expansion and by preference f 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 or December 1, 1936 to Howard Scott, said material being sold under the trade name of Kovan Glass envelope 20 extends upwardly through the wave guide and is sealed, as with reentrant stem 22 to the central rod I4 at a position on said rod above the wave guide, said rod in this instance extending through the seal and projecting from the upper end of the envelope. Standing upright above the wave guide to which it is attached, is a. sleeve-like metallic housing 23 coaxial with the said rod and envelope. The envelope and rod both project into said housing.
Located within said housing above the envelope and around the projecting end of rod I 4 is an annular hollow piston 24 having an outer cylindrical skirt portion 25 and an inner cylindrical skirt portion 26 connected at their upper ends by an annular end wall 2'I. This piston 24 accordingly provides a central bore or passage 28 axially therethrough and provides between said cylindrical skirts 25 and 2B an annular downwardly opening chamber 29 the depth of which from open end 30 to end wall 2'I is a coaxial quarter wave length in the dielectric present, which in this instance is air. It is appropriate to point out that central bore 28 is considerably larger than the diameter of the rod affording ample clearance to avoid contact therewith notwithstanding imperfections of manufacture, misalinement from assembly or distortions in use. Furthermore, a similar clearance or gap 3I is provided between the outside cylindrical skirt 25 and the housing 23 containing the same. These clearances are necessary in view of the fact that in operation very high currents seek to traverse the space between the rod I4 and housing 23 and a sliding contact connecting those parts is generally electrically undesirable and mechanically detrimental. The chamber 29 of the piston is a coaxial quarter-wave length deep, with a high impedance at the open end 36, which acts as a mirror or perfect open coaxial line.
Support and adjustment for the piston 24 is obtained by a screw 32, threaded through the end of the housing 23 and shown with a knurled head 33 at its outer end for manipulation by hand. A lock nut 34 on the screw can be tightened against the housing and retain the screw in its adjusted position. The inner end of the screw is provided with a flare 35 of inverted cup-like shape with the lower rim thereof secured to the end wall 24 of the piston. The flare 35 is of adequate depth to accommodate the upper end of the rod I4 projecting thereinto. The proper antenna reactance can be obtained by adjusting the position of the piston 24 in the tube or housing 23.
The introduction of the proper radiation resistance for the antenna is accomplished by provision of an appropriate closure for one end of the said wave guide. Preferably said closure comprises a piston 38 rectangular in cross section to correspond to the shape of the wave guide and having a skirt portion 38 forming an interior chamber 39 which is a quarter wave length deep and opens toward the coupling device. This piston provides an end wall 40 from which said skirt 38 projects. On the other side of the end wall 40 from the said skirt is a reduced portion or neck 4I which connects with a rectangular head portion 42 of appropriate size to have sliding t with the interior face of the wave guide. It will be noted from the drawing that the skirt portion 38 is of less dimension than the inside dimension of the wave guide so as to provide a gap 43 between said skirt portion and the wave guide. There exists a high impedance at the forward open end 6I since the piston chamber is a quarter wave-length deep, referred to wave guide wave length. In order to adjust this piston for altering the radiation resistance of the antenna the head 42 thereon is connected to a screw 44 rotatyA fixed closure 4'I is screwed to the end of the wave guide as by being attached to a collar 48 which partly engirdles the end margin of the wave guide and retained thereon by suitable means, such as screws 49. Adjusting screw 44 has a suitable finger piece such as the knurled knob 50 and is retained in adjusted position by a lock nut 5I adapted to be turned tightly against the end of xed housing 41.
Electrical continuity between the upper end lsaid rings, envelope sleeve i6.
of coaxial tube I and the adjacent wave guide bottom wall is obtained by means set forth in and `forming the subject matter of co-pending appli- -opposed on the outside of the envelope by a metallic ring 53 the upper end of which connects with the wave guide. Surrounding the metallic ring 53 is a glass ring 54 having the same dielectric constant as the glass of the envelope. This glass ring is interposed between the metallic ring and a lower housing 55 which extends from thimble l5 to the wave guide and is concentric with The glass ring, metallic ring and enlargement 52 are of a length substantially equal to a quarter coaxial wave length in the dielectric represented by the glass.
It may now be pointed out that an essential feature of the present invention resides in the v provision of a piston of quarter wave length depth out of contact from the surrounding wall of the structure in which it is used. While Figure 1 illustrates use of two such pistons both of which are adjustable at any time, it is equally within the scope of the invention to provide a piston which can be adjusted at the source of manufacture and permanently soldered in place after the adjustment has been made. A modification illustrative of this permanently adjusted structure is shown in Figure 4. Referring to this View in detail, envelope 25 with its contained coaxial rod Ma together with supporting thimble l5 and lower housing 55 conforms to the construction al ready described. Upper housing 23a differs from the preceding construction in that it is open at its upper end. A piston 2da is situated in the housing 23a said piston having outer and inner cylindrical skirts 25a and 25a with an upper end wall 21a. As before, a central bore or passage 28a. is provided through the cylindrical inner skirt leaving ample clearance for the rod ille.
Between the said inner and outer skirts 25a and 26a an annular downwardly opening chamber 25a depth of which from open end 35a to end wall 21a is a quarter coaxial wave length in air. At the upper side of end wall 2id is a reduced portion or neck '56 which connects thereabove with a head 5l the size and shape of which is such that it ts within the open upper end of housing 23a. After adjustment has been made this head is soldered, as at 553, to the housing and retains that adjusted position thereafter. It is to be noted that although head 5l nts the housing there is a gap Sla separating the outer skirt 25a from contact with said housing.
Piston for radiation resistance yadjustment is provided, and adjustment accomplished in a manner similar to the construction heretofore described. In this instance, piston 35a is rectangular and provides a skirt portion 38a forming a chamber 39a therein with a depth to the end wall 45a equal to a quarter wave length in air, referred to wave guide wave length. At the outer side of said end wall lila is a reduced portion or neck 41a and therebeyond a head 42a. The headis of appropriate dimension and has a sliding t with the wave guide whereas the skirt portion 38a is of a smaller dimension so as to leave a clearance or gap 43a 'between the skirt and the wave guide. After the piston is located at the desired adjusted position at the place of manufacture it is permanently secured las by solder 59.
While the foregoing construction has many advantages outstanding amongst which is the fact that the open front edge of the piston constitutes a high impedance and, therefore, makes it immaterial as to the structure o1' impedance at the rear of the piston, certain advantages are to be gained by reversing the piston and having the solid wall toward the front and the open end projecting vrearward with modifications in the depth of cups however. Essential among these differences is the fact that the latter construction permits closer association of the piston to the center line of the wave guide in the instance of the piston on the axis of the probe or closer to the center line of the probe in the instance of the piston at the end of the wave guide. Also the coaxial quarter wave length rather than the wave guide wave length is used in determining the depth of the inverted rectangular cup 36h. Reversing the piston has the effect of a movable shorted line instead of a movable open line as in Figure l. A construction including pistons Zlib and h having the solid faces 2lb and 40h thereof forward is illustrated in Figure 5. Care is taken in this construction of Figure 5 to maintain high impedance at the planes 35h and Sib of the open rear ends of the respective pistons and low impedance at the forward closed ends thereof. Parts in Figure 5 are designated by the same reference numerals as used in connection with the description of Figure l, but with the addition of the letter b thereafter, so that repetition of description is not believed necessary here. It is to be here noted that pistons 26th and 350 are a coaxial quarter wave length deep.
lIn connection with the construction shown in Figure 5 the flare 35h for reversed piston 24h extends into the chamber 25h of the piston to the middle part of end wall 2lb to which it is secured. Likewise with respect to the other piston 3th, neck Mb extends axially within the chamber 39h of piston 35i) to the forward end wall 4Gb thereof to which it is likewise attached. As in the preceding construction of Figure l, the piston in each instance is separated from the part of the device surrounding the same. In this instance the high impedance is at the gap at the rear open end of the piston whereas the low impedance is at the forward closed end of the piston.
In Figures 6 to 8 an ultra-high frequency generator lc is indicated with probe Hc entering cavity I2C and projecting therefrom transversely through a wave guide H30 by virtue of rod or v antenna formed as a continuation of said antenna. Thimble having tube Hic next its inner bore, Kovar sleeve and tubular boro-.- silicate glass envelope 2Go are provided as before, together with enlargement 52C on the tube |50 within the envelope and metallic and glass rings 53e and 511C opposed thereto on the outside of the envelope for constituting an impedance section and electrical continuity at the longer dimension bottom wall of the wave guide. In this showing an impedance section is provided in the upper housing above the wave guide.
Describing this upper impedance section more in detail, the same comprises a metallic enlargement S2 of the coaxial quarter wave length in glass.` This lenlargement ts upon the rod Mc and is silver soldered, as at 63. The outer peripheral surface of this enlargement is next the glass envelope. Outside the envelope, of same length as and directly opposed to the said enlargement is a metallic ring 64 and next thereto is a glass ring 65 both of substantially coaxial vquarter wave length in glass. The glass ring ts within an upper housing 66 shown as made in two sections for enabling assembly to be accomplished more readily. The position of this electrically shorted line is readily obtained once the characteristics of the particular type of generator is established. This section obtains effect of an electrical shorting and no high frequency passes therebeyond. This completely avoids heretofore troublesome arcing and corona occurring at the outer end of rod or antenna |40 between said antenna and housing.
At the end of the wave guide, is provided a reversed piston 36e having skirt 38e providing a chamber 39e to a forward end wall 40e such that the chamber is a quarter wave length deep in air referred to free space wave length. The piston is supported by a head 42e which fits the wave guide, a neck portion Mc extending from said head into the piston chamber and connected to the mid part of the forward end wall 40o. As in previously described constructions, the skirt 38c of the piston is spaced from the several walls of the wave guide leaving a gap 43e therebetween. The adjustment of the proper radiation resistance is achieved by the movement of piston 36e and when accomplished said piston is soldered, as at 59o in place.
The reversed piston tuning means above described may be used with other constructions of coupling devices, such as the rugged commercial structure shown in Figure 9. The piston structure is identical in Figure 9 with that in Figure 6, wherefore description is not repeated and parts may be identified by the same numerals but with substitution of letter d after each. Similarly the upper impedance section of Figure 9 is also like that of Figure 6 and a corresponding use of numerals is made.
In Figure 9, ruggedness of structure is obtained by utilizing an inverted cup 61 of Kovar at the top of the glass portion of the envelope d is sealed at its rim to the glass. Rod Idd is secured to the end wall of this inverted cup at the inside thereof. By virtue of the impedance section in front of the Kovar cup, little energy escapes thereto.' Maximum rigidity and maintenance of accurate spacing of parts is obtained by use of the said inverted cup and by securing the rod thereto.
Referring to Figures 1 and 4, the forwardly facing open ended pistons 36 and 36a represent open lines, and the forward plane at 6l and Ela of each is substantially a half wavelength distant from the respective rod or antenna I4 and Ma. Similarly, in the same figures, with regard to the coaxial line pistons 24 and 24a, the forward open end of each is a quarter wave length distant from the center line of the respective wave guide i3 or i3d. With the reversed or inverted skirt pistons of Figures 5 to 9, showing the shorted line assembly, the forward plane of the piston in each case is the solid wall 4Gb, 45e and 40d, and this is at a distance of a quarter wave length distant from the rod or antenna |417, Mc or 14d. With the coaxial construction, the forward plane of the piston represented by solid wall 2lb, Figure 5, and the forward end of the corresponding impedance sections in the upper housings,
are substantially a half wave length from the centerline of the respective wave guide |31), l3c and I3d. Exact location of the forward planes of the several pistons is then made so as to produce the particular antenna radiation resistance and antenna reactance required at the point of termination and so are not strictly multiplesof quarter wave lengths.
Since the various details of construction, as well as the precise relation and functioning of parts, are subject to variation and change Without departing from the inventive concept or scope of the invention, it is intended that all matter contained in the specification or illustrated in the drawing, shall be interpreted as exemplary and not in a limiting sense. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein shown and described and all statements of the scope of the invention herein set forth as a matter of language which might be said to fall therebetween.
1. A coupling device from an ultra high frequency generator to a wave guide, comprising an elongated sealed and evacuated envelope, a rod of which a part constitutes a pick-up portion and a part constitutes an antenna, both of said parts of the rod being within the vacuum of the envelope, said rod extending longitudinally of said envelope, said envelope and rod being transverse to and projecting through said wave guide and the wave guide having one portion for conveying energy from the region surrounding the antenna and having a directly opposite enclosure portion terminating outwardly from the antenna of the order of an odd quarter wave length therefrom, vand a closure for the second mentioned portion, said closure having as part thereof a piston-like member having a closed end and an open end and forming with the enclosure portion a resonant system by which high impedance is established at the open end and low impedance at the closed end of the said member.
2. A coupling device from an ultra high frequency generator to a wave guide, comprising an elongated Sealed and evacuated envelope, a rod of which a part constitutes a pick-up portion and a part constitutes an antenna, both of said parts of the rod being within the vacuum of the envelope, said rod extending longitudinally of said envelope, said envelope and rod being transverse to and projecting through said wave guide and the wave guide having one portion for conveying energy from the region surrounding the antenna and having a directly opposite enclosure portion terminating outwardly from the antenna of the order of an odd quarter wave length therefrom, and a closure for the second mentioned portion, said closure having a piston as part thereof said piston having its cross-sectional dimensions less than the corresponding dimensions of the wave guide thereby forming a gap between the piston and Wave guide, and said piston having an open to and projecting through said wave guide and the wave guide having one portion for conveying energy from the region surrounding the antenna and having a directly opposite enclosure portion terminating outwardly from the antenna of the order of an odd quarter wave length therefrom, and a closure for the second mentioned portion, said closure having a piston as part thereof said piston having a skirt portion therearound open at one end and closed at the other and of smaller outside dimensions than the inside dimensions of the wave guide, thereby forming a peripheral gap between said skirt and Wave guide, and said skirt providing an open quarter wave-length cavity therein by which impedance is minimized at said closedend across the gap.
4. A coupling device from a source of resonant frequency to a Wave guide, comprising a wave guide and an elongated envelope projecting therethrough, an antenna extending longitudinally of said envelope connected to the source of resonant frequency and having an extension projecting through the end of the envelope, a metallic housing over said extension of the antenna and end of said envelope thereat coaxial with said antenna and joined to said Wave guide, and a piston in said housing outside of said envelope and around said extension and out of contact from said housing and electrically coupled with low impedance to said housing for current flow, said antenna being substantially a predetermined distance from said wave guide the value of which establishes the required antenna reactance, whereby the same resonant frequency existing in the envelope is transferred to the wave guide.
5. A coupling device from a source of resonant frequency to a Wave guide, comprising a wave guide and an elongated envelope projecting therethrough, an antenna extending longitudinally of said envelope connected to the source of resonant frequency and having an extension projecting through the end of the envelope, a metallic housing over said extension of the antenna and end of said envelope thereat coaxial with said antenna and joined to said wave guide, a piston in said housing outside of said envelope for providing impedance matching between said source and wave guide, said piston being out of contact'from both said housing and said antenna extension, and means productive of low impedance by Way of said piston from said antenna extension to said metallic housing for providing current flow from said antenna extension to the wave guide, whereby the same resonant frequency existing in the envelope is transferred to the wave guide.
6. A coupling device from a source of resonant frequency to a Wave guide, comprising a wave guide, and an elongated envelope projecting therethrough, an antenna extending longitudinally of said envelope connected to the source of resonant frequency and having an extension projecting through the end of the envelope, a metallic housing over said extension of the antenna end of said envelope thereat coaxial with said antenna and joined to said wave guide, a piston in said housing outside of said envelope and out of contact from and electrically coupled with low impedance to both said housing and said antenna substantially at a common plane transverse to said housing and antenna.
'7. A coupling device from a source of resonant frequency to a wave guide, comprising ua wave guide and an elongated envelope projecting therethrough, an antenna extending longitudinally of said envelope connected to the source of resonant frequency and having an extension projecting through the end of the envelope, a metallic housing over said extension of the antenna and end of said envelope thereat coaxial with said antenna and joined to said wave guide, and a piston in said housing outside of said envelope for providing impedance matching between said source and wave guide, said piston having an end wall and a skirt with the skirt having a longitudinal dimension of an odd quarter wave length paralleling said housing and said skirt being out of contact from said housing and providing means in conjunction therewith productive of low impedance at one end of the piston for current flow from said antenna extension to said housing.
8. A coupling device from a source of resonant frequency to a wave guide, comprising a Wave guide and an elongated envelope projecting therethrough, an antenna extending longitudinally of said envelope connected to the source of resonant frequency and having an extension projecting through the end of the envelope, a metallic housing over said extension of the antenna and end of said envelope thereat coaxial with said antenna and joined to said wave guide, and a piston in said housing outside of said envelope, said piston having an end wall and a skirt with the skirt having a longitudinal dimension of an odd quarter wave length and said skirt being out of contact from said housing, said skirt having its open end toward the wave guide and its end wall at the end of the skirt away from the wave guide.
ERNEST CARL OKRESS.
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|International Classification||H01J23/54, H03H2/00, H01J23/00|
|Cooperative Classification||H01J23/54, H03H2/006|
|European Classification||H03H2/00T1, H01J23/54|