US2433074A - High-frequency coupling device - Google Patents

Description

w G TULLER 2,433,074 HIGH-FREQUENCY COUPLING DEVICE Flled July 2 1943 mmvroa 0mm! 63 ELLE/ BY W v 'flTTX Dec. 23, 1947.

Patented Dec. 23,. 1947 HIGH-FREQUENCY COUPLING DEVICE WilIi'amGi' Tullentwatertowii; Ma's'sl', assignsfic Massl ai'corporation of R'ayth'eo'm' Manufacturing Company, Newton,

' Delaware Application J uly. 2 1943, -Serial= N o2 493,224 r 4 cl'aimsr (Cl. 178 -44) This inventionrelates to" guided" electromag netic'wave transmission, and more particularlyto Another object is :to :producesuch a-"coupling by.

asimple and. .compacttstructure.

The:- foregoing; and other. objects ;of. this .in-

vention will be best understoodfrom thejfol lowing description of.an.exemplification-thereof,

reference: being hadito; the: accompanying draw-- ingI wherein:

Fig. 1 isasection through my novel coupling."

system taken alongline .l-l of Fig. 2; and

Fig. Zis. a. section: taken along line.2-2-- of Fig; 1..

The couplingsystem. shown comprises a-icoaxial conductor. transmission line consisting of a tubular conductor l having-a neutral conductor 2, said:

transmission line being coupled-to ahollow dielectric waveguide Themembersl Land 3 are: formed :01 highly conducting material,- such as copper or brass. The wave guide 3 is preferably of rectangular cross-section having a long side Aland a short side-: Oneend'of the tubular conductor I is joined to one long side 4 of the wave guide3which is provided with an opening therein-substantially of' the-size of thetubular conductor l through'which the-conductor 2pro- J'ects for 'a substantial distanceinto the wave guide 3.

When electromagnetic waves of sufficiently high frequency are transmittedalong the coaxial conductor transmissionlin'e, the 'ab'ove coupling ar rangement will excite'tlie-wave'guide 3 in what is knownas the-'IEt'n mode; and such waves will be propagated down through the wave guide. The TEo,1 mode is that=mode"in' which the electric vector of the propagatedcwave is always transverse to the direction of propagation of the wave in the wave guide. There is a single maximum of field distributionalong'one side of the wave guide, and no such maximumialong thewother' sldeofi said wave guide: Inzrthearrangements which I have illustrated, the single maximum-will occur alongthe longlside ofthe'wave guide: The TEo,1 mode is the simplest and most commonly 2f used? mode of 'exbitation of "wave guides of this' typ r N Inordr for thecenergylofthe wave which is propagated along such a system to be efiectively' and efiiciently transferred from the coaxial conductor transmission line to the Wave guide, it is desirable that there be no reflections atthe point of coupli-n'gbetween these two 'sy'stemss For 'this pose tlie impe dance Oi the -conductor wmen extends into the wave guide 3 and forms aprobeshould be matched to the impedance of the coaxial conductor transmission line. I have found that if-thetprobeend of the conductor 2-is terminated by a partial spherical member 6, that i s, a spherical member which iswflattened in the plane..where it meets the probe end or said conductor 2; b'ear'ingthe proper relationship both to: the :diameter of. the conductor 2" andto-th'eim side. diameter. of the conductor l, the impedance ofthecoaxial conductor transmission line can be matched with the-impedance of the probe and thus produce the desired. refiectionless coupling.

Insuoh an arrangement also a-reflecting platel is locatedin the wave guide S at the proper distance behind th'e probe-so asto form a resonant chamber termination for said wave guide.

I have found that using. the following notation: S =diameter of partial sphere 6 A=diameter of conductor 2, Binner diameter ofecondu'ctor l Thus, for exam'ple, in a coupling arrangement in which theinner di'ameterofthe conductor I was .81 2-in'ch th'e diameter of the conductor 2 was .375

inch and the diameter of the partial sphere 6 was-.4375 inch, substantiallyno reflection occurredat the coupling point.

ternal cross-section, and the :probe extended into the wave guide .965 inch.

A consideration of. the above equation shows that as: th ratioof B/A;increases,-the ratio of S/A decreases. Thus, iforexampleywhere the internal-diametenof theconductonl was 1.527 inches and the diameter of the conductor 2 was .625 inch, the diameter-of the partial-sphere 6* was likewise '.625 inch. In order for-proper open 1 ation,-thepartial sphere 1 6 should be attached to the conductor 2- so i that the section through the 1 partial sphere in the plane where-it is attached-to the conductor should be of the same size as the In-this case thewave guide was 1.344 inches by 2.834 inches in in'-' cross-section of the conductor. Thus the last example cited represents a limiting case in which the member 6 is a hemisphere. If the ratio of B/A were to be increased beyond that indicated, the ratio of S/ A would be less than one, and therefore the condition of matched section of the partial sphere and the cross-section of the conductor would not ordinarily be obtained. However, for conditions of this kind I have found that the end of the conductor 2 as it approaches the partial sphere 6 may be gradually decreased in diameter so as to afford at least a one-to-one ratio between the diameter of the partial sphere and the reduced diameter of the end of the conductor 2.

Coaxial conductor transmission lines and dielectric wave guides, such as I have described above, are usually designed to carry electromagnetic waves of approximately a predetermined wave length in the wave guide, which wave length may be represented by A. In Fig. 1 I hav designated the distance between the reflecting surface of the plate 1 and the center of the probe as L. Theoretical considerations have indicated that L should be about I have found, however, that proper operation is secured in my arrangement when L is approximately I have found that coupling systems constructed in accordance with the foregoing principles have enabled the transmission of substantially increased quantities of electromagnetic power therethrough. Also I have found that such a coupling arrangement remains matched in its impedance to the impedance of the coaxial conductor transmission line over a relatively substantial frequency variation in the electromagnetic wave without further adjustment. It is to be understood that the numerical values of particular systems which I have listed above are given merely by Way of example, and it is further understood that the principles of my inventionmay be applied to a wide variety of coupling systems.

What is claimed is:

1. A coupling system comprising a coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a hollow wave guide, said inner conductor extending into said hollow wave guide through an opening in a side wall of said wave guide and forming a probe, said probe being placed in a transverse electric mode-exciting relationship With respect to said hollow wave guide, said outer conductor being connected to said wall, said probe terminating in a member comprising a portion of a sphere, the diameters of said member, said probe and said outer conductor bearing approximately the relation where S is the diameter of the member, A is the diameter of the probe and B is the inner diameter of the outer conductor.

2. A coupling system comprising a coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a hollow wave guide, said inner conductor extending into said hollow wave guide through an opening in a wall of said wave guide and forming a probe, said probe being placed in a, transverse electric modeexciting relationship with respect to said hollow wave guide, said outer conductor being connected to said wall, said probe terminating in a spherical member which is flattened in the plane where it meets said probe, the area of the flattened portion being equal to the cross-sectional area, of said probe, and an electromagnetic wave-reflecting plate disposed across said wave guide at one side of said probe and spaced from the center of said probe a distance approximately equal to onesixth of the wave length of the electromagnetic wave which said wave guide is adapted to transmit.

3. A coupling system comprising a coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a hollow wave guide, said inner conductor extending into said hollow wave guide through an opening in a side wall of said wave guide and forming a probe, said probe being placed in a transverse electric mode-exciting relationship with respect to said hollow wave guide, said outer conductor being connected to said wall, said probe terminating in a member comprising a portion of a sphere, the diameters of said member, said probe and said outer conductor bearing approximately the relation . where S is the diameter of the member, A is the diameter of the probe and B is the inner diameter of the outer conductor, and an electromagnetic wave-reflecting plate disposed across said wave guide at one side of said probe and spaced from the center of said probe a distance approximately equal to one-sixth of the wave length of the electromagnetic wave which said inner guide is adapted to transmit.

4. A coupling system comprising a coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a rectangular hollow wave guide, said inner conductor extending into said hollow wave guide through an opening in a side wall of said wave guide and forming a probe, said probe being placed in the TEo,1 mode-exciting relationship with respect to said hollow wave guide, said outer conductor being connected to said wall, said probe terminating in a member comprising a portion of a sphere, the diameters of said member, said probe and said outer conductor bearing approximately the relation REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,147,717 Schelkunoff Feb. 21, 1939 2,307,012 Barrow Jan. 5, 1943 2,316,151 Barrow Apr. 13, 1943 Certificate of Correction Patent No. 2,433,074. December 23, 1947.

WILLIAM G. TULLER It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Column 2, line 42, for 1.344 read 1.384; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 9th day of March, A. D. 1948.

THOMAS F. MURPHY,

Assistant aommzsswner of Patents.

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