US2923895A - Dual-mode bifurcated waveguide transducer - Google Patents

Description

Feb. 2, 1960 c w, CURTIS ETAL 2,923,895

DUALMODE BIFURCATED WAVEGUIDE TRANSDUCER Filed Oct. 1, 1956 Fig. 3.

INVENTORS. Charles W.Cur1is, Roben L.Foge|,

ATTORNEY United States Patent DUALMODE BIFURCATED WAVEGUIDE TRANSDUCER CharlesW. Curtis, Manhattan Beach, and Robert L. Fogel, Torrance, Calif., assiguors to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Application October 1, 1956, Serial No. 613,023 3 Claims. c1. ass-9 This invention relates to a waveguide transducer and more particularly to a waveguide structure which permits the selection of predetermined modes.

' In wave energy transmission systems it is often desirable to provide for propagation of more than one signal using a common frequency by utilizing various wave energy modes as separate channels. It is well known in theart that twqdominant modes such as the TE and the TE -modeof the square waveguide will propagate independently because they are orthogonal. The practical problem associated with this problem is to excite or to extract wave energy in one mode independent of the ther mode. One transducer having the above indicated properties which has been. used in the past to; perform thisfunction comprises a circular waveguide to which-two rectangular waveguides are radially coupled by way of apertures. The longitudinal axes of the two rectangular 2,923,895 Patented eb. 2,

ducer of this invention, a cruciform waveguide adapted to propagate the two orthogonal TE and TE wave and the circular waveguides are mutually perpendicular. a it This waveguide transducer which is fully described in A Broad-Band Dual-Mode Circular Waveguide Transducer by R. D. ,Tompkins, IRE Transaction on. Microwave Theory and Techniques,.published by the Institute of RadioEngineers, Inc., vol. MIT-4, number 3, page 181 (July 1956), involves the transformation of orthogonal TE -modes of the circularwaveguide to the dominant TE -modes of two separate and orthogonally positioned rectangular waveguides. This, as well as other prior art transducers, give rise to relatively high reflections due to the non-symmetry of the junctions and less isolation between the channels than desirable. Further, this type of transducerrequires the excitation of an aperture, namely, the rectangular opening in the circular waveguide wall to which the rectangular waveguide is coupled. All sys- It is therefore an object of this invention to provide a waveguide transducer adapted to independently excite or extract wave energy in two orthogonal modes without the use of auxiliary matching or absorption components or the inclusion of electrical short circuit terminations.

It is a further object of this invention to provide a symmetric waveguide transducer having negligible reflection loss, a high order of isolation, and which is capable of handling large amounts of power, both when exciting and when extracting one of the modes.

It is a still further object of this invention to provide a waveguide transducerwhich is simple in construction, has a high efl'iciency, and which is broad-band in operation.

In accordance with the dual-mode waveguide transenergy modes may be bifurcatedinto two rectangular waveguides each adapted to propagate a different one of the two orthogonal wave energy modes. Thistransducer is a device which along one direction of propaga tion separates two orthogonal wave energy modes, and along the other direction of propagation combines two orthogonal wave energy modes.

Fig. 1 is a perspective end view of the bifurcated waveguide transition of this invention, Fig. in shows the electric field vector distribution thereof;

Fig. 2 is a cutaway perspective side view of the waveguide transducer of Fig. 1; and H Fig. 3 is a cross-sectionalview taken along the line 33 of the waveguide transducer of Fig.2.

The novel features which are believed to be character istic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connectionwith the accompanying drawing in which an embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawingis for the purpose of illustration and description only, and is not intended as a definition of the limits of the invention. Referring now to the drawing wherein like numerals are used throughout to designate likeparts, thereare shown different views of the dual-mode bifurcated waveguide transducer in accordance with this invention. I A first rectangular 12 is curved along its direction of elongation about its broad walls 14 and 16. A second rectangular waveguide 20 having longitudinal axis 22 is curved along its direction ofelongation about its narrow walls 24- and 26. The first and the second waveguides 10 and 20 are brought into coincidence with one another by removing obstruct- 10 and 20 terminate and a'straight portion commences.

The waveguides 10 and 20 may thereforebe regarded as having lost their identity as individual waveguides and instead define a cruciform waveguide 30 having longitudinal axis 32.

Whereas from a structural point of view the waveguide transducer of this invention may be regarded as a coinbinationof two intersecting rectangular waveguides, it, is nevertheless useful to describe the waveguide structure from a functional viewpoint. From a functional viewpoint, the invention comprises a cruciform waveguide 30 which is bifurcated into two rectangular waveguides 10 and 20 which are spatially disposed with respect to one another so that thenarrow walls of one are parallel to the broad walls of the other, and whose longitudinal axes 12 and 22 define a plane.

Fig. 1a depicts the orthogonal modes which the cruciform waveguide 30 is adapted to propagate. These are respectively similar to the TE -mode and the TE -mode of the square waveguide. This nomenclature indicates the orthogonal nature of the two modes but otherwise is a not helpful after the wave energy propagated through the modes will separate after passing point 28 so that the waveguide 10 having a longitudinal axis first and the second waveguide and 20 each are excited in their respective dominant mode.

The symmetry of the wave energy transducer of this invention which results by the bifurcation prevents any cross coupling between the modes and therefore assures ofa high degree of isolation. Further, the two rectangu lar: waveguides are excited directly, in contradistinct-ion from aperture excitation, which provides for better broad band: operation and large power handling capacity.

The applications which involve the employment of the dual-mode'bifurcated waveguide transducer of this invention are very numerous as is immediately apparent to thoseskil-led in the: art. Generally, the cruciform waveguide is "coupled by standard techniques such as a quarter wave transformer or a tapered section to a Waveguide of more. conventional cross-section and adapted to propagate orthogonal waveguide modes; Such conventional crosssections, of course. are square or circular.

One application of the bifurcated transducer utilizes the property that orthogonal modes may be; transmitted along a squareor. circular waveguide independent of one another. It is therefore possible to effect the excitation and the subsequent transmission of independent wave energy signals along a single square or circular waveguide. Each of; .the two independent signals is, excited in one or the other, of thereotangular waveguides 10 and 26. The two signals will then, be propagated in the cruciform waveguide; 30. as; orthogonal modes. To. separate the twosigual's, a second; bifurcated wave energy: transducer ma be, coupled to, the transmission system having corresponding rectaugularwaveguides either parallel or' perpendicular to the first transducer.

7 Another application of this bifurcated waveguide transducer involves conventional duplexing. Here the cruciform waveguide is coupled to a 45 degree rotator such as an isolator employing a ferromagnetic ceramic element which is: subjected to a longitudinal constant magnetic field. Suc'h isolators are well known. in the. art. The combination of, the bifurcated transducer and the isolator prvide duplexing action when one rectangular waveguide is. coupled to-a transmitter, the second waveguide is cou pled toareceiver and the output of the isolator is coupled to an antenna.

Still another application of the bifurcated wave energy transducer of this invention is the excitation of a wave energy antenna. Such excitation modes include circular polarization, elliptical polarization or plane polarization along one or two predetermined planes depending on the respectiveamplitude and phase excitation of the, first and. second waveguide.

What is claimed is: t

'1'. A dual-mode bifurcated waveguide transducer com-. prising: a first rectangular waveguide including parallel broad walls curved along its direction of elongation about said' broad walls and terminating in a first straight portijoh, said first waverguide, defining a first longitudinal axis; and a. second rectangular waveguide including parallel narrow Walls curved along-"its-d-irection of elongation about said narrow walls and terminating in a second straight portion, said second waveguide defining a second longitudinal axis, said first and said second waveguides being spatially oriented with respect to one another so that the broad walls of said first waveguide are parallel to the narrow Wall's of said-secondf waveguide, and coupled to one another by-progre's'siv'ely increasing intersection so thatsaid first straight portion and said second straight portion combine. to. provide a'cruciforrn wave guide having a third longitudinal axis lying in a plane'defined by said first and said second longitudinal axes and coinciding therewith alongsaid straight portion.

2a A waveguide transducer for coupling energy'between a common waveguide section and twoindividual waveguide arms, the modes supported in each of the different individual arms and in the common section being orthogonal with respect to eah other, said transducer comprising: a first curved rectangular waveguidehaving planar broad walls andcurv'ed narrow walls; and a second rectangular waveguidefiliavin'g planar narrow walls and curved broad walls, tliebroad walls" of the two waveguides lying in planes which are normal with respect to each other, said waveguides merging into a common cruciform rectangular waveg'uide body defining two rectangular waveguides normal to each other and coli'near with eachother, said waveguides being I'n'erg'ed along the lines of intersection of the walls thereof and having matching internal apertures such that'the interior of each waveguide is of-atl'ea'st full; cross section and such that a central portion of each of saidwaveguides at the common cruciform body is common with the, other of said waveguides.

3. A dual mode bifurcated waveguide transducer comprising: a first rectangular waveguide including parallel broad walls, curvedalong its direction of elongation about said broad walls, and terminating in 'a-fir's't straight rectangula'r waveguide portion; and a second rectangular wave guide including parallel-narrow walls, curved along its direction of elongation about said narrow walls, and terminating in a second"straight portion, the planes of the broad walls of said first and second waveguides being normal with respect to each other and the directions of curvature of the curved walls therein being opposite in direction, the straight portions of each of said waveguides being colinear, the, bodies of said waveguides merging into each other so that a common cruciform waveguide body is provided by the straight 'sectionsof saidl'rect'angular waveguides. h v

References Cited in the file of this patent UNITED STATES PATENTS Kat'zih Nov; 14, 1944 2,364,371 Katzin a- Dec. 5, 1944 2,441,574 Ja /nestle at May 1:8, 194% 2,540,839 Southworth ...e Feb. 6, 1951

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