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Sept. 24, 1946. “A. c. Em 2,408,033" COUPLING- SYSTEM Filed March l7,' 1942 v _ I BYQ INVENTOR A. C.‘ BECK - A TTOR/VEV Patented Sept. 24, 1946 ._ 2,408,033 UNITED STATES PATENT OFFICE 2,408,033 COUPLING SYSTEM Alfred 0. Beck, Red Bank, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. 2., a corporation of New York ‘ Application March 17, 19h, Serial No. 435,016 4 Claims. (Cl. 17s-44) 1 2 This invention relates to microwave coupling devices and more particularly to wave-guide transmission line coupling arrangements. In accordance with the preferred embodiment ’ of the invention a coaxial line having an imped ance Z is coupled to a main quadrilateral wave As disclosed in the copending application of H. T. Friis, Serial No. 435,017, ?led concurrently with the instant application, impedance match guide having a considerably larger impedance as, ‘ for example, ‘ll-Z, through a rectangular wave guide having characteristic impedance of 22 and folded in the plane containing its long trans ing over a band of frequencies between a coaxial line or conductive channel and a main wave verse dimension which plane is perpendicular to guide, and unilateral wave propagation in the the plane of polarization of the electric vector. wave guide, may be effected without the use of a 10 The end apertures of the'folded wave guide sec piston. re?ector by’ means of a rectangular wave tion are superimposed so that their short trans? guide folded or looped in the plane of its short verse dimensions are aligned. The coaxial line is transverse dimension, that is, in the plane of coupled through aimultifrequency matching de polarization of the propagated electric wave com~ vice of the type disclosed in‘ applicant’s copend ing application, Serial No. 429,358, ?led February ponent. In this arrangement the end apertures of the folded guide are superimposed and joined to an end ori?ce of the main guide and the co~ axial line is connected to the longitudinal center point of the looped guide. Also, for multifre quency operation, each of the two branches of the folded guide includes a twisted 90 degree po larity changer for securing colinearly polarized wave components in the superimposed folded guide apertures. While the folded guide cou pling is suitable for use in many microwave sys tems, the polarity changers aside from being more or less difficult to manufacture, cause a certain amount of loss and it now appears desir. able to employ folded wave guide coupling sec tions having no quadrature polarity changers of l the twisted type. In this vconnection applicant has discovered that, contrary to the teaching of the prior art, rectangular wave guides may be equals the combined parallel impedance of the branches or folded guide sections, and the serially connected apertures of the loop section have a bent or curved in the plane of the long transverse dimensions or, stated differently, in a plane per pendicular to the polarization plane of the elec tric component utilized in the wave guide, with out substantial loss and, in fact, with only slight ly greater loss than that sustained in guides fold ed or curved in the plane of polarization. It is one object of this invention to secure in single frequency and multifrequency systems, each comprising a wave guide coupled to a trans mission line, unilateral propagation in the wave guide without utilizing a reflecting piston and with minimum loss. It is another object of this invention to match the impedances of a dielectric channel and a line channel Without using auxiliary adjustable ap paratus or quadrature polarity changers of the twisted wave-guide type. It is still another object of this invention to obtain a multifrequency folded wave-guide cou pler which does not include twisted portions and which is simpler in construction than the cou plers heretofore utilized. As used herein the term “quadrilateral” gener ically includes the terms “rectangular” and “square,” and the term “rectangular” excludes “square.” 1942, to the longitudinal center point of the rectangular folded wave guide; and the superim posed end apertures are joined to an end ori?ce of the main quadrilateral wave guide. In opera tion, the wave components or wavelets in the two branches of the loop section have, at the longi tudinal center point mentioned above, equal phase angles and are similarly polarized. Since the end apertures of the loop are equally distant from the center point and since the folded guide is not bent in the plane of polarization, the wave lets at the superimposed apertures are in phase angle agreement and are similarly polarized, whereby a wave of maximum intensity is propa gated unilaterally in the main quadrilateral guide. Moreover, as explained in the copending' Friis application, the coaxial line impedance total impedance equal to‘ that of the quadrilateral ‘ guide. J Hence, the folded guide section functions as a transformer for matching the impedances of the coaxial line and the main Wave-guide over a band of microwave carrier frequencies. The invention will be more fully understood from a perusal of the following‘speci?cation ta ken in conjunction with the drawing on which like reference characters denote elements of sim ‘ilar function and on which: Fig. 1 is a perspective View of one embodiment of the invention; and Fig. 2 is a side or elevational View of the same embodiment. ‘ Referring to Figs. 1 and 2, reference numeral I designates a translation device for transmitting or receiving microwaves and numeral 2 denotes a conductive channel or coaxial line connected thereto. The line channel 2 is connected through a rectangular wave guide section 3 folded or looped in the plane of its long, transverse dimen sion b to a quadrilateral main wave guide or di- ‘ electric channel ll and a radiating or receiving antenna such as a horn 5. The inner conductor 60 6 of coaxial line 2 is attached to the folded guide 2,408,033 3 section 3 at the longitudinal mid-point ‘I of the looped guide through a multi-frequency coupling device of the type disclosed in applicant’s copend ing application mentioned above and comprising 4 Although the invention has been explained in connection with a certain embodiment thereof, it should be understood that it is not to be limited to this arrangement inasmuch as other appara an adjustable sleeve member 8. As explained in Cl tus may be employed in successfully practicing the invention. More particularly, the folded my application mentioned above, the sleeve is adjusted and a particular value for the short transverse dimension a of the loop 3 selected such wave-guide coupling section and the main wave guide may each have a square instead of a rec tangular cross section. Also, any other type of conductor 6 has the proper length and impedance 10 line, such as a balanced line, and even a dielectric wave-guide channel, may be employed in place for matching over a carrier band of frequencies of the coaxial line; and the invention may be the characteristic impedance Z of line 2 to the utilized for coupling a balanced line to a dielectric total folded guide impedance comprising the im channel or for coupling two dielectric channels. pedances of the two loop branches I0 and I I con What is claimed is: nected in parallel. Thus, assuming the line 2 has 15 1. A dielectric channel-transmission line cou a characteristic impedance Z equal to 100 ohms, pling device comprising a rectangular wave-guide each of the loop branches II] and I I has a char section for conveying wave components polarized acteristic impedance 22 equal to 200 ohms, and in the plane of one transverse dimension, said the two impedances in parallel equal the line im pedance. The main dielectric channel has a 20 section being looped or curved in the plane of the ‘ other transverse dimension and having superim characteristic impedance, IIZ, which may be taken posed apertures, the section being connected at as the value of its input or send end impedance since the length of the main guide 4 is great rela its mid-point to said line and at its super-imposed tive to the wave-length employed and may be apertures to said channel. considered in?nite. Inasmuch as the apertures 25 2. A. quadrilateral dielectric wave channel l2 and I3 are superimposed with their transverse transmission line coupling device comprising a dimensions a aligned, the characteristic im folded rectangular wave guide having a short pedances of the apertures are serially associated transverse dimension equal substantially to one and their total impedance, GZ, equals the send half of the short transverse dimension of said end impedance and the characteristic impedance 30 channel, said folded guide having its end aper of guide 4. , tures superimposed for junction with said chan In operation, assuming device I is a transmit nel and an aperture at an intermediate pointv ter, while the energies conveyed between the de for junction with said line, the two paths con vice I and the horn 5, and propagated in the necting said intermediate point with said chan branches I0 and I I, flow relative to point 1 in op 35 nel ibeing electrically equal, said guide being en ergized with waves polarized in the plane of its posite or bilateral directions, the combination in cluding looped section 3 functions to produce only short transverse dimension and folded in the unilateral propagation in the dielectric channel plane of its long transverse dimension. 3. In combination, a quadrilateral wave guide 4. Arrows I4, I5, I6 and I1 denote the directions of propagation in line 2. branch I0, 'branch I I and 40 having a given impedance and an end ori?ce, a guide 4. respectively. The wavelets propagated in transmission line having a di?erent impedance, and means for matching said impedances and for directions [5 and I6 have, at center point ‘I, the same (zero) phase angle and are similarly polar producing unilateral propagation in said guide ized as shown by arrows I8 and IS in a'direction comprising a rectangular wave-guide section hav aligned with the short transverse dimension a 45 ing an impedance intermediate said impedances and the exposed exciter 9. that is. in a vertical and a curvature in the plane'of its long trans direction in the plane of the drawing. Contrary verse dimension, said section having superim to the ‘effect secured in a system of the copending posed end apertures joined to an end‘ ori?ce of Friis ‘application, the curvature in the coupling said quadrilateral guide, said line projecting into 50 section 3 does not shift the polarity of these wave said section at its mid-point in a direction coin lets since the curvature is only in a plane per cident with the short transverse dimension of pendicular to the direction of polarization. said section. a that the exposed. exciter portion 9 of the inner Moreover. the branches I i) and II are of equal 4. In a system for transmitting transverse elec length so that in apertures I2 and I3 the wave tric waves. a quadrilateral wave guide having an lets are similarly polarized, as shown by arrows 55 end ori?ce. a coaxial line, and means for connect ing said guide and line and matching their ime 20 and 2!. and combine to form a maximum vec tor. resultant 23 in the main wave-guide chan nedances over a band of frequencies several hun dred megacycles wide, said means comprising a nel 4. rectangular wave guide folded in the plane of the Thus. in accordance with the invention the sys 60 transverse dimension perpendicular to the polar tem or combination illustrated by Figs. 1 and 2 ization of the transverse electric wave and hav and comprising a multi-frequency coaxial line ing superimposed end apertures joined to an end to-wave guide. coupling device, a wave-guide cou ori?ce of said quadrilateral guide. the character pling section folded in the plane perpendicular to the plane of polarization of the electric vector 65 istic impedance of the rectangular guide being equal to twice that of said line and to one-half and a main dielectric channel. functions to match that of the cuadrilateral guide, a multifreouency the impedances of a line channel and a dielectric impedance coupler connecting‘ said line to the channel. without re?ection losses and without mid-point of said folded guide. whereby corn-v losses due to changing the polaritv of the wave component. over a hand of carrier frequencies in nonents transferred between said line and said cluding several hundred megacycles. At the same time the combination functions to produce ,uni lateral or one way propagation in the quadrilat eral wave guide 4. ?rst rectangular guide have the same polarity endsama phase angle at the iunction of the su perimposed‘ end apertures with said end ori?ce. ALFRED C. BECK.