US3176300A

US3176300A - Adjustable slotted wave guide radiator with coupling element

Info

Publication number: US3176300A
Application number: US340014A
Authority: US
Inventors: John A Kuecken
Original assignee: Avco Corp
Current assignee: Avco Corp
Priority date: 1964-01-24
Filing date: 1964-01-24
Publication date: 1965-03-30
Anticipated expiration: 1982-03-30

Description

March 30, 1965 J. A. KUECKEN 3,176,300

ADJUSTABLE SLOTTED WAVE GUIDE RADIATOR WITH COUPLING ELEMENT Filed Jan. 24, 1964 2 Sheets-Sheet l INVENTOR.

J OHN A. KUECKEN.

"MM M gmfiw 7 1. 7 701 ATTORNEYS.

March 30, 1965 J. A. KUECKEN 3,176,300

ADJUSTABLE SLOTTED WAVE GUIDE RADIATOR WITH COUPLING ELEMENT Filed Jan. 24, 1964 2 Sheets-Sheet 2 INVENTOR.

JOHN A. KUECKEN 3,17 6,304 ADJUSTABLE SLOTTED WAVE GUIDE RADIATOR WITH CGUPLENG ELEMENT John A. Kuecken, Cincinnati, Ohio, assignor to Avco Corporation, Cincinnati, Ohio, a corporation of Delaware Filed Jan. 24, 1964, Ser. No. 340,914 3 Claims. (Cl. 343-767) This application is a continuation-in-part of U.S. application Serial No. 91,168, filed February 23, 1961, now abandoned.

The present invention relates to wave guides for use in ultra-high frequency techniques, and specifically to a novel and readily adjustable wave guide radiator or slot antenna.

A primary object of the invention is to provide a radiator including a coupling element which is adjustable over a wire range of electrical admittances.

Another object is to provide a radiator which is not so subject to cross-polarization problems as conventional radiators.

A further object of the invention is to provide a radiator which is readily mechanically adjustable. This feature is of particular worth in wave guide arrays involving a plurality of slot-type radiators, the entire array being conventionally subject to radical impairment of its desired characteristics in the event of misalignment of one or more of the slots.

An ancillary object is to reduce the close tolerances and critical character normally required in slot antenna fabri cation.

Another important object of the invention is to provide the combination of a rectangular wave guide formed with a normally substantially non-radiating slot extending parallel to the electric field and across the short side of the guide, and a trombone-shaped, substantially inductive coupling element mechanically positioned obliquely to bridge the slot and to provide a slot looped by the magnetic field.

A related object of the invention is to provide a radiator including a plurality of such slots and coupling elements.

A further object of the invention is to provide such a combination in which the coupling element is adjustable both as to angularity relative to the slot and penetration of the wave guide.

The use of slotted rectangular wave guides in microwave transmission and reception would be materially enhanced if simple means were available for adjusting the coupling and radiation properties. The need for a practical solution of this problem led me to the concept of a combined slot and element radiator adjustable for wide admittance characteristic. This invention accomplishes these objectives and offers advantages which, it is believed, constitute a significant contribution in wave guide techniques.

For a better understanding of the present invention, reference is made to the following description of the appended drawings, in which:

FIG. 1 is a perspective view of the combination of a rectangular slotted wave guide and a hairpin-type coupler in accordance with the invention;

FIG. 2 is a fragmentary sectional view taken along line 22 of FIG. 1 and looking in the direction of the arrows;

FIG. 3 is a perspective view of a modified embodiment of a slotted rectangular wave guide and trombone-type coupler in accordance with the invention which is adjustable both as to penetration and angular relation to the slot; and

FIG. 4 is a sectional View through the collet and seal plate utilized in positioning the coupling element.

While the invention is simple in its mechanical presenta- United States Patent "ice tion, the theoretical considerations involved are complex. The Wave guide 10 is a conventional rectangular wave guide such as the type RG49/U, operating in the TE mode. The significance of this designation is that the electrical field of the guide is transverse to the longitudinal axis of the guide and has no component in the direction of such axis. This mode is often referred to as the dominant mode of a rectangular wave guide. The electrical field extends between the two parallel walls which are most closely spaced-i.e., between the top wall 11 and the bottom wall. Now, assume that .a slot 12 is formed in side wall 13 and that the central axis of this slot extends in the vertical direction-4e, parallel to the electrical field. A wave guide slotted in this manner will not radiate any substantial amount of energy. Vertical slot 12 produces negligible magnetic coupling between the wave guide and outer space, because the slot is transverse to the magnetic flux and does not substantially interfere with the flow of currents in the guide wall. A vertical sloti.e., a slot along the short side dimension-does not substantially electrically couple the wave guide to-outer space, because no electrical field terminates on side Wall 13.

The theoretical factors here involved are well expressed in Electronic and Radio Engineering, Terman, pp. 128- 135, particularly pp. 133 and 134, McGraw-Hill Book Company, New York, 1955.

As indicated in the Terman text just referred to, and by numerous other authorities such as Antennas, Kraus, page 356, McGraw-Hill Book Company, New York, 1950, it was classically taught that slots of this character should be cut in inclined fashion in order to make them radiate. While Airborne Radar, Povejsil, Raven, and Waterman, pages 526, D. Van Nostrand Company, Inc., New York, 1961, points out the advantages of side wall slots, this authority again shows them tilted. See also Principles and Practice of Radar, Penrose and Boulding, page 412, D. Van Nostrand Company, Inc., London, 1949. Various workers in the art recognized this characteristic of shortside-slotted rectangular wave guides, operating in the dominant mode, and made efforts to solve the problem. U.S. patent to Shanks et 221., 3,004,259, is an example. Shanks et al. provide ferric stubs which distort the normal magnetic field within the guide. Shanks et al. do not disclose any practical means for individually adjusting these stubs. Now the combination in accordance with the present invention provides inductive coupling so that magnetic phase sensitivity is very small. By contrast to Shanks et al., any magnetic field distortion in the combination of the present invention is held to a minimum. Additionally, the present invention provides a readily adjustable combination.

In accordance with the invention, the slotted wave guide '10 is caused to radiate by the provision of a hairpin loop surface conductor 14, the bight 15 of which is inclined at an angle to the slot, and the

feet

16 and 17 of which are transverse to the side wall 13. The hairpin is inserted into the wave guide, and the feet slide tightly into suitably formed

apertures

18 and 19 in the Wave guide side wall 13, in trombone-like fashion.

By the provision of simple means for adjusting the coupling and radiation properties of a slotted wave guide, the present invention materially enhances the field of usage of such wave guides in microwave transmission and reception.

The depth of insertion of the loop 14 in the wave guide determines the admittance or coupling characteristic with reference to external loads. 7

Magnetic fields within the guide induce voltages in the loop 14 and cause the wave guide slot to radiate. The degree of coupling between the wave guide and outer space-i.e., the radiation fieldis varied by' controlling the penetration of the loop orthemechanical dimensions 7 of the loop. In practice, generally only one adjustment is made, and the loop may be secured in place by soldering the feet to the waveguide at the apertures; Additionally, the; admittance may, be controlled by varying the angularity (here shown as 45 degrees) of the'l-oop'with re spect to the slot. Such a variation may be accomplished a by providing additional pairs of apertures in the wave guide at different angular relationships with respect to the slot, selectmg the desired pair of apertures, and then filling in those unused, as with solder.

The embodiment of FIGS. 1 and 2 has been reducedto from opposite sides of the slot when the coupling is to be reversed.

In addition to the

screws

26 and 27, the plate, is fastened to the side wall waveguide byan additional screw practice, and measurements made at a frequency of 5400 megacycles. parameters were as follows:

Width of slot 0.11 inch. Distance between slot and closed end of the wave guide f length. Angle of (i,e.-, angle between the central axis, of the slot and an imaginary line between the two feet ofthe hairpin) 45de gr'ees.

Penetration of loop into wave guide From 17 to 31 7 millimeters.

Nature of hairpin M inch wire.

Distance between the two hairpin feet 0.3 inch.

The. advantages of a radiator invention are:

(1) Adjustable energy-coupling over a wide range;'

in accordance with the arrays are employed;

In the successfullytested embodiment, the

, a (2) Reduction of cross-polarization when Wave guide 1 32. The sides of the arcuate slot 28 are wedge-shaped, as shown at 33 and 34, so that as the plate 23 is securely fastened in place, the Wedge surfaces 33 and 34 press the I fingers 30 of a collet 29 against'the portion 17 of the hairpin element, maintaining it in the desired position of adjustment, so far as penetration of the wave guide of the coupling element is concerned. 7

The large skirt 35 on the upper side of the collet serves asa dust cover and weather seal for the, wave guide if Quarter wave I a In FIG. 4 the to'p'of portion (3) Slots in the wave guide elements may be milled w-itha single setting of the milling machine and without great precision, when a multi-slot array is fabricated;

(4) This radiator is conveniently, mechanicallyadjustable in the operating location;

(5) This radiator may beemployed when the wave guide is excited in any of the TE modes, and its;utility i-s not limited to the dominant mode.

In FIGS.) 3 and 4 there is shown an adjustable version of the invention. The reference numerals 10311, and 13' designate elements which are so substantially identical necessary. The collet makes a tight connection of short electrical length immediately 'at the point where the hairpin emerges from the wave guide wall, since the colletis pressed into boththe hairpin portion 17 and the wave guide Wall to obtain the wedge action.- Thus, good electrical contact and extremely low inductance are assured. 117 is broken away for clarity in illustration, j

While there have been shown and described what. are at'pre'se'nt cons'ideredto be the preferred embodiments of the invention,it will be understood by those skilled in the 3 art that various modifications and changes may be made therein without departingifrom the' true scope of'the invention as defined in'the appended claims, as by operating in other TE'modes, for example.

I claim; e V 1. The combination of a rectangular wave guide operating in aTE mode and formed with a normally substantially non-radiating slot extending parallel to the'electrical fieldand ac'ro'ssthe short side of the guide, and a hairpin-,

shaped substantially inductive coupling element mechanically positioned in the guide obl-iquelywith respect to the magnetic field behind the slot'to bridge the slot andto providea loop linked by the magnetic field, said coupling element-being formed with feet and said, guide having apertures adjustably receiving said-feet in; trombone to corresponding elements in, FIGS. 1 and 2 as not to re- V quire'fu-rther and repetitious description. Element 14 of FIG. 3 is identical to the element 14 of FIG.'1." In the embodiment of FIGS..3 and 4, the short side 13' of the wave guide is provided with symmetrically arranged opposed

arcuate slots

21 and 22; one on each side of the radiating slot 12. Portion 17 of the trombone element 14 projects through the slot 22. and portion l6 through the slot 21. It will be observed th=atthis arrangementpermits the angular relationship of the plane of the trombone element-to a central plane passed through the slot 12, to be adjusted as desired. After such adjustment is made, 'the' andpositioning means for adjusting the angular posidesired position of the coupling element is maintained or secured by a pair of pinch and s'ealplates. such 23,

one associated'withportion 17 and one associated with a portion lfi. .1 The plates are alike so that thedesc ription will be cohfined to plate 23, it being shown as removed troni the wave guide for purposes of clarity in description; The plate issecured in aperturesi24 and-'25 in the'wave guide by

screws

26 and 27, it being understood that the fashion. p I e a e 2. The combination ofa rectangular wave guide operatingin aTE mode and formed with a" normally substantially non-radiating slot extendingparallelt o the electrical field and across the short side of the guide, a hairpin-shaped substantially inductive coupling ele- ;ment mechanically positioned in the guide obliquely I with respect to the'm'ag'netfield behind the slot to bridge the slot and to provide a loop linked by the magnetic "field, said coupling element being formed with feet and said-guide'having curved slots for receiving lsaid feet', I

tion of said coupling element. 3. The combination inaccordancelwith'claim 2' in .which the positioning means comprises a pair of clamp plates having curved slotsinjregistrywith the first-mentioned curved slots, and; further having collets through which the feet of the coupling element project.

screws are loosened'when theadjustment of the element I 14 is being made and then tightened to secure that element in the desired adjustment. Portion 17 of that element projects not only through arcuate slot 22' but also through a a slot 28 in plate 23 of approximately half the arcuate I length of slot 22. Thisarrangement permits'portion 17,

for example, to be varied in position along the

slots

22 and 28.

'It is reiterated that the semi-circular slots 21 and-22 of the slot. such rotation adjusts the coupling of the I IZ efei-ence'sCitedbY Examiner" 7 HER MAN KARl. SAALBACH, Primary Examiner.

ELIIQLIBERMAN, Examiner.

Claims

1. THE COMBINATION OF A RECTANGULAR WAVE GUIDE OPERATING IN A TE MODE AND FORMED WITH A NORMALLY SUBSTANTIALLY NON-RADIATING SLOT EXTENDING PARALLEL TO THE ELECTRICAL FIELD AND ACROSS THE SHORT SIDE OF THE GUIDE, AND A HAIRPINSHAPED SUBSTANTIALLY INDUCTIVE COUPLING ELEMENT MECHANICALLY POSITIONED IN THE GUIDE OBLIQUELY WITH RESPECT TO THE MAGNETIC FIELD BEHIND THE SLOT TO BRIDGE THE SLOT AND TO PROVIDE A LOOP LINKED BY THE MAGNETIC FIELD, SAID COUPLING ELEMENT BEING FORMED WITH FEET AND SAID GUIDE HAVING