US2521732A - Rotating antenna scanning system - Google Patents

Description

Sept. 12, 1950 M. KLINE 2,521,732

ROTATING ANTENNA SCANNING SYSTEM Filed Oct. 25, 1944 INVENTOR. MORRIS KLINE ATTORNEY outside thereof. sides of the gap should *bematched. I have Patented Sept. 12, 1950 ROTATING ANTENNA SCANNING SYSTEM ,Morris Kline,Little Silver, 'N. J assignor to the United States of America as represented by the Secretary of War Application October 25, 1944, Serial No. 560,298

Claims. 7 (01. 250-3355) .(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 ,0. G. 757) The invention described herein may'bemanufactured and used by or for the Government for governmental purposes, without the payment to meofany royalty thereon.

My present invention relates to switches, and more particularly, to switches for controlling the flow of high-frequency energy in transmission lines, especially, but not necessarily, incoaxial transmission lines.

While not limited thereto, one application of my present invention is to the control, in a scanning antenna system, .of the transfer of energy successively to or froma plurality of antenna elements which are :mounted, .in cadvance of .aparabolic reflector, forrotationin-a vertical or :horizontal planeabouta central-point located along the axis of said;reflector. By this arrangement, the direction of radiation ,or-response of the system is periodically shifted through a predetermined angle,-at,a predetermined ;rate, to continuously scan a ,preselected vertical or horizontal sector of space.

It has heretofore been proposed, in order to control-the successive transfer of energy in ;a

scanning antenna system ofthe character above described, to employ brush contact or capacity switches. .I have found, however, that the former type'ofswitch sparks at high voltage, :andthe latter type requires delicate adjustment of the spacing of the plates to. obtainproper capacity .and still prevent voltage breakdown.

Bothtypes are therefore unsatisfactory.

Hence, it is themain-object of my present invention to provide a switch which is capable of handling radioefrequency energy at high power levels'withoutxthe danger of breaking down, and with. a minimum loss of such energy.

It is a further object of mypresent invention .toprovidea switch,:having the above characteristics, which is simple in construction, and easy and economical to fabricate and assemble.

These, and other objects :and advantages of -my present invention, which will be better understood as the detailed description thereof ,pro- Igresses, are attainedin 'thefollowing manner:

.I havepfound that iftwo transmissionlines,

energy, and :even :this loss canrbe reduced by :providing chokes at the: facing ends of the lines so that energy; is prevented from leaking to 1 the Of course, the lines onbotn metal therein. these findings by providing said piece of metal polarized, half-wave dipoles further found that the transfer of energy across said gap can be blocked by placing a piece of My present invention utilizes scribed, andin the. annexed drawingshown, what is at present considered a preferred embodiment of theswitches ofmy present invention. It is, however, to be clearly understood that my presentinvention is not limited to said embodiment, inasmuch as changes .thereinmay be made without the exercise of invention and within the true spirit and scope of the claims hereto appended.

In .said drawing, the single figure is a perspective view of ascanm'ng antenna system incorporating a switch made in accordance with the principles of mypresent invention.

Referring now more in detail to the aforesaid preferred embodiment-of my present invention,

with.particularvreference--to the drawing illustrating the same, thenumeral 5 generally designates a transmitting and/or receiving antenna system. Said system includes a parabolic re- :flector 6 having, for example, an aperture of about 5 feet, and a focal length of about 20 inches. Said system further includes a plurality, here shown asfounof preferably vertically l, which are mounted, atthe ends of parallel-fed, coaxial transmission-line sections 8, for rotation about ,acentral point located along theaxis of therefiectorg6, approximately 37 inches from the ver- ,;tex;thereof. The outer endof each transmission ,line sectionB should be such a distance from theaxis of rotation thereof.that,..for about .of .its rotation, the dipole Fl carried thereby is more or less in the focalplane ofthe reflector .6. If desired, the transmission-line sections 8 may further be provided with parasiticallyexcited reflecting .elements ,9 disposed at an appropriate distance to the rear of the dipoles l.

,Aswi1l be obvious to those skilled the ,art,

of 90 to each other. The inner ends thereof are supported at the outer ends of radial spider arms which extend from a hub (not shown) mounted upon the shaft ll of a driving motor l2. The-shaft ll extends through a central, oversized opening i3 formed in a'metal disc M which constitutes the above-referred to shutter, and at the outer end of said shaft, there is mounted another hub 15, provided with radial spider arms [6 supporting, 'at their outer ends, additional transmission-line sections H. The latter constitute parallel-fed branches of a transmission-line slip joint [8, mounted for rotation at the end of a transmission line l9, which may be connected to a radio transmitter or receiver or, through appropriate known circuits. to both a transmitter and a receiver. The transmission-line sections 8 and I! are so disposed with respect to each other as to present between the aligned ends thereof gaps of somewhat less than about A; of an inch, the facing ends or said transmission-line sections being provided, preferably, with shorted quarter-wave sections 2i so as to prevent radiation by leakage, and thereby hold the loss of energy resulting from the transfer across the gap to a minimum. Furthermore, the line sections 8 and I! should be matched to each other, and to the equipment at the end of the line H.

The disc M, which is supported between the transmission-line sections 8 and I! in any suitable manner, has a sector cut out of the same, as at 22, the cut-out sector covering about 70 of arc, and being symmetrically disposed about the axis of the parabolic reflector 3, facing said reflector. While the cut-out sector has been described as covering about 70 of arc, it is to be understood that the size of the sector depends on the use to which the switch is being put. In the embodiment under consideration, the switch is being used for lobe shifting, and it has been found that if it is desired to shift the direction of radiation or response of the antenna system through about 45, symmetrical with respect to the axis of the specific reflector described, 70 is a proper size for said cut-out sector. This is not to be construed as a limitation.

By means of the foregoing arrangement, energy may be transferred between the transmission-line sections 8 and I! only when the facing inner ends thereof are exposed to each other through the cut-out sector 22 of the disc I4. Now, inasmuch as the disc I4 is fixed, and the transmission-line sections 8 and I1 rotate as a unit, only that dipole whose associated transmission-line sections are momentarily sweeping past the cut-out sector 22 of said disc is effectively connected to the equipment at the ground end of the line i9.

This completes the description of my present invention, and it will be noted from all of the foregoing that I have provided a switch which is capable of handling radio-frequenc energy at high power levels, which is simple and inexpensive, and which is amenable to a wide variety of applications and uses.

Other objects and advantages of my present invention will readily occur to those skilled in the art to which the same relates.

I claim:

1. In combination with a scanning antenna system which includes a stationary parabolic reflector, a plurality of rotating antenna elements mounted for rotation about a point along the axis of said reflector; and a switch for controlling the transfer of energy successively to and from 4 said rotating antenna elements from and to said reflector thereby periodically shifting the direction of radiation of said system, said switch including a corresponding plurality of discontinuous transmission lines having a corresponding plurality of air gaps, said lines being connected to respective antenna elements through said gaps; a stationary shutter member disposed in the gap presented by the discontinuity in each of said transmission lines; said shutter having an open sector permitting said transfer of energy and means for moving said transmission lines relative to said shutter member and said sector to control the transfer of energy across said gaps and to scan a preselected sector of space by rotating said antenna elements with respect to said reflector.

2. A scanning antenna, system including a source of radio energy, a parabolic reflector, a plurality of antenna elements mounted for rotation about a point along the axis of said reflector; and a switch for controlling the transfer of energy successivel to and from said rotating antenna elements from and to said reflector thereby periodically shifting the direction of radiation of said system, said switch including a corresponding plurality of parallelly-connected discontinuous transmission lines having a corresponding plurality of air-gaps, each of said lines being connected on one side to said source of radio energy and on the other side to a corresponding antenna element through a corresponding airgap; a stationary disc, having a sector of predetermined size cut out of the same, said disc being disposed in the gaps presented by the discontinuity in each of said transmission lines; and means for moving said transmission lines and said antenna elements relative to said disc to control the transfer of energy across said gaps to said antenna elements.

3. In combination with a scanning antenna system which includes a stationary parabolic reflector, a plurality of antenna elements mounted for rotation about a point on the axis of said reflector, and a switch interposed between a source of radio energy and said antenna elements for controlling the transfer of energy successively to the rotating antenna elements when they scan a predetermined angular sector with respect to said parabolic reflector, said switch comprising a corresponding plurality of pairs of coaxial transmission lines having a corresponding plurality of gaps in said lines, a stationary shutter disposed in said gaps and having an open sector whose angle is equal to said predetermined angular sector, and means for simultaneousl rotating all of said pairs of transmission lines and said antenna elements as a unit relative to said shutter to allow the transfer of energy across said gaps only to that single antenna element whose corresponding gap is within said sector.

4. A scanning antenna system including a parabolic reflector, a plurality of antenna elements mounted for rotation about a point along the axis of said reflector, said antenna elements being connected to a source of radiant energy through a common concentric line and a corresponding plurality of parallelly connected concentric branch lines whereby each of said antenna elements is connected to said source through said common line and a corresponding branch line, said parallelly connected concentric branch lines each having an air gap, said air gaps lying in a single plane, said air gaps normally permitting transmission of said energ through said branch lines to said antenna elements, a stationary shutter disposed in said air gaps, a cut-out sector in said stationary shutter permitting transmission of said energy through the branch line positioned within said sector to the corresponding antenna element, and means for rotating said concentric branch lines and said antenna elements as a unit with respect to said stationary shutter, thereby controlling the transfer of said energy across said gaps from said source to an antenna element. 1

5. A scanning antenna system including a main stationary concentric line connected to a source of radiant energy, a plurality of rotatable concentric branch lines coupled to said main line, said branch lines each terminating in a rotatable antenna element, a stationary parabolic reflector, said branch lines and said antenna elements being mounted for rotation about a point along the axis of said reflector, said branch lines each having an air gap, said air gaps being disposed in a single plane, a stationar shutter disposed in said gaps and said plane and having a cut-away sector permitting electrical coupling between said source and said antenna elements when a corresponding concentric branch line and its air gap 6 are within said sector, a frame for mechanically integrating said branch lines and said antenna elements, and means for rotating said frame, said branch lines and said antenna elements for sequentially controlling the transfer of said ener y to said antenna elements, whereby the rotation of the energized antenna element with respect to said reflector produces scanning of a preselected sector in space by said radiant energy.

MORRIS KLINE.

REFERENCES CITED The following references are of record in the file of this patent:

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