US 3172111 A
Description (OCR text may contain errors)
March 2, 1965 L. D. BREETZ 3,172,111
MULTI-POLARIZED SINGLE ELEMENT RADIATOR Filed Aug. 30, 1962 2 Sheets-Sheet l A N D PHASE RELATIONSHIP POWER RATIO RADIO FREQUENCY ENERGY OPERATING DEVICE INVENTOR LOUIS D. BREETZ BY M M W M1 ATTORNEY March 2, 1965 1.. D. BREETZ 72,111
MULTI-POLARIZED SINGLE ELEMENT RADIATOR Filed Aug. 30, 1962 2 She ets-Sheet 2 INVENTOR. LOUIS D. BREETZ ATTORNEY United States Patent Ofi ice 3,172,111 Patented Mar. 2, 1965 3,172,111 MULTI-POLARIZED SINGLE ELEMENT RADIATOR Louis D. Breetz, ()xon Hill, Md, assignor to the United States of America as represented by the Secretary of the Navy Filed Aug. 30, 1962, Ser. No. 220,966 13 Claims. (Cl. 343730) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
This invention relates to antenna systems in general and in particular to antenna systems having polarization variation properties.
In the early usage of radar systems for the detection of ships and aircraft, the predominantly horizontal extent of such large targets and the generally more convenient horizontal orientation of linear antenna elements such as dipoles and yagi antennas provided natural complements to each other. The advent of long, small diameter missiles and the desire to detect them at great distances during the initial propulsion phase as Well as in a possibly tumbling or otherwise changing aspect while in orbit has brought about a condition in which attention must be given to polarization optimization. Polarization diversity in itself is nothing new. Spiral antenna elements as well as crossed dipoles are well known and can be used in various ways to achieve polarization variation. A real difficulty arises however in connection with the detection of objects in orbit, where to achieve the required sensitivity and directivity it is not uncommon to stretch an array of dipole antenna elements in a line for several thousand feet along the earths surface. Such large arrays provide impedance matching problems particularly where the relatively low impedance dipoles are used and also are of characteristically narrow bandwidth. Thus it is not unusual to find that folded dipoles have advantages particularly when it is possible to place the dipoles at right angles to the longitudinal axis of the string of dipoles constituting the array. This arrangement is not too well adapted to convenient use with crossed dipole structures and hence is not suited to polarization diversity applications.
Accordingly it is an object of the present invention to provide an array of folded dipoles suited for polarization diversity operation.
Another object of the present invention is to provide a folded dipole antenna system having polarization diversity capabilities.
Another object of the present invention is to provide a folded dipole having all active components in a single plane and capable of producing linearly polarized fields in orthogonally related planes as well as circularly polarized fields of either sense and various intermediate elliptical polarization fields.
Another object of the present invention is to provide a polarization variable antenna in which the individual elements are of such configuration as to resist relative deflections which would alter the relationship of the various polarizations.
Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
FIG. 1 shows an embodiment of a single antenna ele ment and feed system therefor constructed in accordance with the teachings of the present invention.
FIG. 2 shows an array of elements of FIG. 1.
In accordance with the teachings of the present invention, a polarization diversity antenna system is pr vided which is particularly suited for arrays having a large number of elements. The system employs elements each described as a duplex folded dipole the elements being cou pled to a radio frequency operative device through power ratio and phase controlling apparatus whereby the desired polarization is obtained in the coupling of the elements to space.
The duplex folded dipole provides very flexible operation in that it is capable of producing One or the other of orthogonally related linear polarization plane couplings or of producing circular polarization coupling of either sense or again, when proper feed conditions exist, of providing intermediate elliptical polarization coupling. A duplex folded dipole as that term is used here contains a plurality of parallel conductors disposed in close proximity, the conductors being approximately a half wave length in overall extent or some multiple thereof. The conductors are typically disposed in one plane with the center conductor being interrupted for a portion of its length at approximately the center thereof, all conductors being connected together at their outer ends. The duplex folded dipole is fed in two Ways, first at the inner-ends of the center discontinuous conductor and secondly at the centers of the other conductors. The two feeds thus described can be either simultaneous or alternating according to some desired sequence. The result for either single feed is the production of linearly polarized radiation, the polarization being in orthogonally related planes for the two different feeds individually. If the feeds are simultaneous, of the same effective power, and possess quadrature phase relationship, the radiation from the antenna element is circularly polarized. Where the effective powers are different and the effective phasing is other than 0, 270 and 360, the polarization is elliptical with the axial-ratio and orientation of the major axes depending upon the power ratio of the two feeds and the phasing. The sense of circular polarization depends upon the relationship of the quadrature phasing of the two feeds being for example of one sense when one quadrature related feed is leading with respect to the other and of the opposite sense when the relationship is lagging. Almost an infinite variety of linear polarization planes is possible when the effective radiation for the two feeds is in phase or 180 phasing merely by varying the effective power ratio for the two feeds.
Care has been exercised to speak in terms of effective power because of the fact that the impedances of the two antenna feeds is quite different. Normally the center conductor feed is several hundred ohms while the feed to the outer conductors is between 500-1000 ohms.
It must also be appreciated that speaking in terms of feed power while apparently limiting to transmit operation is merely for convenience of expression since the basic principle is equally applicable to the receive operation.
With reference now to FIG. 1 of the drawings, the apparatus shown therein as previously mentioned contains a typical embodiment of an antenna element and system constructed in accordance with the teachings of the present invention. The typical antenna element defined as a duplex folded dipole is made up of basic components 10 and 11 which are disposed substantially in axial alignment and with a small separation of their adjacent ends 12 and 13 to provide an overall dipole of approximately a halfwave length or some multiple thereof if desired or convenient as the discontinuous conductor mentioned in the preceding discussion. Such a basic antenna structure as thus far described is of course readily recognized as including a conventional center fed half-wave dipole.
To this half-wave dipole of components 10 and 11 are added the coextensive cooperative components 14 and 15 which are disposed in a common plane with components 10 and 11 and substantially parallel thereto. Components 14- and 15 are continuous and of uniform dimensions throughout their half-wave extent. The outer ends of components 1%), 11, 14 and 15 are connected together by means of conductive members 16 and 17. The resulting planar structure is a device in which all portions thereof are subjected to the same external forces which would tend to produce deflection so that relative distortion of the elements is not particularly troublesome as would be the case with crossed dipoles mentioned in the introduction to the specification in which, for example, wind pressures on one dipole of crossed dipoles can be considerably different from the wind pressure on the other.
Two feed connections for the duplex folded dipole of FIG. 1 are provided. The first feed is a conventional form of feed for folded dipoles having only a single side member 14 or 15 which is at the ends 12 and 13 of the center components 19-11. This basic feed is of approximately the 300 ohm impedance of typical folded dipoles.
A second feed for the duplex folded dipole is provided at substantially the centers of the components 14 and 15 which are fed in push-pull relation to each other. The feed at the centers of components 14 and 15 has substantially higher impedance than that at the points 12 and 13. By making the components 10 and 11 of considerably larger diameter than the components 14 and 15 reduction of the impedance at points 12 and 13 is effected. Similarly changing the spacing of the components 14 and 15 from the components 14} and 11 provides some control of the impedance at the centers of components 14 and 15.
With the basic feed to the points 12 and 13 being linearly polarized, radiation or coupling results in which the plane of polarization is substantially parallel to the plane of the components 110-11, 14 and 15. On the other hand with feed at the center of components 14 and 15, linear polarization also results, however, it has a plane of polarization which is orthogonally related to that of the first case. When the two feeds bear a quadrature phase relationship a peculiar situation results in that the two radiations combine to effectively produce circular polarization. Where the feed relationship is other than quadrature, various polarization combinations result.
The two feeds are connected to a radio frequency energy operative device 18, such as a transmitter or receiver or combination through a control device 19 which may typically contain a variable power splitter and variable phase control devices whereby the power ratio and phase relationship may be adjusted.
The field intensity pattern for the antenna of FIG. 1 is in general similar to that of a folded dipole for both polarization planes being maximum normal to the longitudinal axis of the element. An E-plane field Pattern for both modes of approximately 90 degree beamwidth between the three db levels and an H-plane pattern of approximately 160 degrees between the three db levels was obtained in a typical experimental installation for this duplex dipole placed over a ground plane.
As in a normal folded dipole, or any dipole for that matter, the field pattern can be adjusted appreciably by changing the spacing between the element and the ground plane. In this respect this element is similar to other dipole elements.
In a typical embodiment of the apparatus of FIG. 1 intended for half wave operation at a frequency of 108 megacycles per second, the overall length of the components including members 16 and 17 was typically 54 inches with a center to center spacing of the components 14 and 15 being 5 inches, components and 11 being disposed midway between 14 and 15. The spacing of the feed points 12 and 13 was typically 1 inch While the components 14) and 11 were constructed of material having 1% inch diameter, the diameter of components 15 and 14 and the members 16 and 17 being approximately of an inch. It was determined that the impedance at points 12 and 13 under such conditions as outlined under the foregoing was approximately 280 ohms whereas the impedance fed at the centers of components 14 and 15 was approximately 700 ohms.
FIGS. 2 indicates a typical arrangement wherein a plurality of duplex folded dipole antennas of the type of FIG. 1 can be effectively placed in an array for purposes of achieving improved sensitivity and directivity. The particular array is such as would find utility in an upward looking system for the detection of the passage overhead of earth satellites. A refilector 50 of wire mesh is mounted substantially horizontally above the surface of the earth.
Above the reflector 50 a plurality of duplex folded dipoles 51 are placed. These dipoles are individually disposed normal to the longitudinal axis of the array with the plane of the components (10-11, 14, 15 of FIG. 1) also perpendicular to the axis of the array. The elements are spaced a half wavelength apart along the longitudinal axis and suitably supported as from the reflector support structure by members 52.
The members 52 also provide as by a hollow construction, a shielded passage for the feed lines and, with suitable insulation, fixed relative positioning of the elements in the central region.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
What is claimed is:
1. An antenna element comprising, first and second rod-type components disposed one end of one to one end of the other with their longitudinal axis in substantial coincidence, the adjacent ends being insulated from each other, the overall extent along the longitudinal axis to the outer ends being substantially a multiple including unity of a half wavelength.
third and fourth rod-type components substantially a multiple including unity of half wavelengths long disposed adjacent and parallel to the combination of the first and second components, in substantially the same plane and with the ends in substantially the same planes as the outer ends of the first and second components,
means connecting the outer ends of the first and second components to the adjacent ends of the third and fourth components,
first energization means for enabling energization of said first and second rod-type components as a halfwave dipole antenna,
and second energization means for enabling energization of each of said third and fourth rod-type components at a point substantially intermediate their respective outer ends.
2. An antenna element comprising, first and second rod-type components disposed one end of one to one end of the other with their longitudinal axes in substantial coincidence, the adjacent ends being insulated from each other, the overall extent along the longitudinal axis to the outer ends being substantially a multiple including unity of a half-wave length,
third and fourth rod-type components substantially a multiple including unity of a half wavelength long disposed adjacent and parallel to the combination of the first and second components, in substantially the same plane and with the ends in substantially the same planes as the outer ends of the first and second components,
means connecting the outer ends of the first and second components to the adjacent ends of the third and fourth components,
first transmission line means for connecting to the first and second components at the adjacent ends thereof, second transmission line means for connecting to the 23 third and fourth components at the centers thereof,
a radio frequency operative device,
and means for coupling the said device to said transmission lines in selected relative phase and power ratio.
3. An antenna according to claim 1 wherein said second energization means enables energization of said third and fourth rod-type components in push-pull relation to each other.
4. An antenna according to claim 3 wherein said first and second energization means include means for selectivity energizing said first and second rod-type components as a unit and said third and fourth rod-type components as a unit either individually or simultaneously.
5. An antenna according to claim 1 wherein said first and second rod-type components are of identical uniform cross-section, and wherein said third and fourth rod-type components are of identical uniform cross-section but of a cross-section smaller than said first and second rodtype components.
6. An antenna according to claim 1 wherein said first and second energization means include means to enable energization of said first, second, third and fourth rodtype components in selected relative phase and power ratio.
7. The combination comprising a plurality of antenna elements as defined in claim 1 arranged in linear array with their planes disposed in parallel relationship to each other and spaced substantially a half-wave length apart, and a planar radiant energy reflector for said linear array lying in a plane substantially perpendicular to the parallel planes of said plurality of antenna elements.
8. The combination of claim 7 wherein said reflector is a wire mesh.
9. A transmit-receive duplex antenna comprising in combination,
a first antenna unit defined by a pair of conductive elements forming a center-fed half-wave dipole,
a second antenna unit defined by a pair of linear conductors, each of said conductors being coextensive with the length of said dipole and positioned on opposite sides of said dipole elements in parallel and planar relationship therewith, said conductors having energy feed connections at a point substantially intermediate their respective outer ends,
means connecting the outer ends of said dipole elements to the outer adjacent ends of said pair of conductors,
and radio frequency operating means operatively associated with said first and second antenna units to selectively enable said antenna units to operate individually or simultaneously.
10. A duplex antenna according to claim 9 wherein said conductors are of uniform cross-section but smaller than the cross-section of said dipole elements.
11. A duplex antenna according to claim 9 wherein said radio frequency operating means include adjustable means to enable said first and second antenna units to operate in selected phase and power ratio relationship.
12. The combination comprising a plurality of duplex antennae as defined in claim 11 arranged in a linear array with their planes disposed in parallel relationship to each other and spaced substantially a half-wave length apart,
and a planar radiant energy reflector for said linear array lying in a plane substantially perpendicular to the parallel planes of said plurality of duplex antennae.
l3. duplex antenna comprising,
a three conductor folded dipole having the center conductor interrupted substantially at the center thereof to enable said center conductor to operate as a center-fed half-wave dipole,
connection means at the center of each of the outer conductors of said folded dipole to enable said outer conductors to operate as an antenna unit,
and means for selectively enabling said operationally formed center-fed half-wave dipole and said operationally formed antenna unit to operate individually or simultaneously.
References Cited by the Examiner UNITED STATES PATENTS 2,234,744 3/41 Thomas 343-804 X 2,345,735 4/44 Douma 343-804 X 2,703,840 3/55 Carmichael 343-804 2,825,061 2/58 Rowland 343-743 X 2,953,781 9/60 Donnellan et al. "343-858 HERMAN KARL SAALBACH, Primary Examiner.