US2496242A

US2496242A - Antenna system

Info

Publication number: US2496242A
Application number: US546181A
Authority: US
Inventors: William E Bradley
Original assignee: Philco Ford Corp
Current assignee: Space Systems Loral LLC
Priority date: 1944-07-22
Filing date: 1944-07-22
Publication date: 1950-01-31
Anticipated expiration: 1967-01-31

Description

W. E- BRADLEY ANTENNA SYSTEM Jan. 3L 195@ Filed July 22, 1944 INVENTOR. VVzZ/fam Efi aa/sg Patented Jan. 31, 1950' UNITED STATES ANTENNA SYSTEM William E. Bradley, Swarthmore, Pa., assignor, by mesne assignments, to Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania.

Application July 22, 1944, Serial N 0. 546,181

24 Glaims. 1

My invention relates in general to the field of signalling systems and more particularly concerns a novel and improved antenna structure.

In high frequency transmission systems, en ergy is ordinarily radiated from an antenna array suitably supported and fed from a resonant transmission line. The nature of the antenna structure is of course dependent upon the desired type of transmission.

The feeding system generally comprises a coaxial transmission line properly terminated and tuned by matching stubs so that a maximum energy transfer may occur. In certain ultra-high frequency transmission systems, as for example, radio ranging or radar, it is particularly desirable to utilize a duplex transmission system re quiring two antenna arrays. Heretofore, in the energization of such a double antenna structure, numerous problems have arisen which were primarily concerned with the mutual interference of the electrical feeders and the antenna radiating structure. Thus, for example, if two antenna ar rays were stacked one above the other, and en ergized from individual coaxial feeders, then the feeder for the upper array would interfere with radiation from the lower antenna array.

Accordingly it has generally been essential that the antenna arrays be separated or that the feeders be energized from opposite ends of the duplex antenna structure. This of course unnecessarily complicated the support of antenna structures upon towers, masts and the like.

My invention contemplates'and has as a primary object an antenna feeding system which permits the stacking of a plurality of antenna arrays, all of which are energized from a single end thereof, and which preclude mutual interference between antenna radiation and feeder systems. Each individual antenna array consists of a coaxial resonator short circuited at theupper end and driven from the lower end by a coaxial line with dipole elements coupled into the resonator at half wave intervals along the resonator.

Individual coaxial feed lines are provided for each of the antenna arrays, and may be driven from suitable oscillating sources. The inner con ductor of the resonator for the lower antenna array is hollow and supports therein an additional concentric feeder which extends up through the lower antenna structure and enters the coaxial resonator of the upper antenna array. This last mentioned inner feeder is energized from the oscillating system feeding the upper antenna structure and accordingly serves as the transmission line for the upper antenna struc ture.

The lower antenna structure is properly matched by a tuning stub connected to the coaxia1 resonator associated with the lower antenna structure. This tuning stub which also may be fed in the manner to be described,

contains the central conductor of the lower antenna structure serves as a suitable means for removing the central feeder for the upper antenna structure from the stacked array of antennae. Accordingly, both antenna arrays are fed from a single end of the multiple structure.

The proper terminating characteristic impedance for each of the two antenna structures is maintained by suitably dimensioning the feeding system, and by properly coupling each antenna element to the coaxial resonators associated therewith.

It is thus an object of my invention to provide a novel and improved duplex antenna structure.

Another object of my invention is to provide a duplex antenna structure energized from a single end thereof without mutual interference.

A further object of my invention is to provide a. multiple antenna radiating structure wherein a plurality of concentrically disposed conductors are utilized to feed the individual antenna radiating structures without mutual interference.

These and other objects of my invention will now become apparent from the following detailed specification taken in connection with. the accompanying drawings in which:

Figure 1 is a cross-sectional schematic view of one modification of a duplex antenna.

Figure 2 is a cross-sectional schematic view of a modification of the duplex antenna principle i1- lustrated in Figure 1.

Referring now to Figure 1, the mechanical detail of a duplex antenna structure will now be described. As illustrated, a metallic structure I i is utilized as the principal support for the double antenna array. This metal member may of course be mounted suitably upon a tower or upon the mast of a ship or the like, dependent upon the particular application of the duplex transmission system. Supported upon the metallic structure I l are the two antenna arrays No. l and No. 2 to be utilized during the transmission or reception of signals, and comprising essentially, a lower array of antenna elements l2 and an upper array of antenna elements l3. These individual antenna elements illustrated at 12 and 53 are rigidly supported upon the metallic structure l l, and suitably insulated therefrom. The driving terminals of the unit antenna elements shown at it and 13 enter the outer metallic structure I 5 through suitable apertures, such as l4.

It is to be understood that the antenna arrays I2 and is illustrated in Figure 1 are merely rep-' resentations of possible antenna structures. As there are many types of antenna arrays which the number and disposition of the antenna elements 1!? and #3 are, of course, dependent upon the directional character of the radiation and the location thereof. Other than indicating a possible modification of my duplex antenna structure, these schematic illustrations of antenna elements at i2 and I3 played no part in the fundamental considerations of the present invention.

A suitable coupling I5 is provided at the lower end of the metallic structure it for a feeder which is connected to the transmission circuit of the apparatus concerned. This feeder may comprise a coaxial cable coupled tothe duplex antenna structure by a connection at coupling l5 so that the outer sheet of the coaxial cable contacts the metallic outer structure H and the inner concentric conductor of th coaxial cable contacts concentric conductor ll rigidly supported within the metallic structure H. Thus, throughout the lower antenna array No. 1, the inner and outer concentric metallic members ll and I! respectively form a coaxial resonator 2! into which the antenna elements i2 are coupled.

At the upper end of the lower antenna array No. l a metal insert 22 is provided to seal the cylindrical resonator between the concentric members H and H.

in order to insure the transfer of maximum energy from the coaxial feeder coupled to the duplex antenna structure at 5 to the lower antenna array 12, it is essential that the chamber 2! be properly matched or tuned. Accordingly, a matching section 25 is connected to metallic member I l at the aperture 23 therein. Similarly, a hollow conductor 21 concentric with and extending from section 25 is connected to the inner concentric conductor [1 at an aperture 26 thereof.

The coaxial conductors 25 and 21 form an annular chamber 31 within which is mounted an annular member 32 axially movable therein.

From the above structural description, it will now be evident that the input impedance to the antenna array No. l is controlled by the amount of penetration of the driving terminals of the antenna elements l2 through the apertures [4 as well as by the specific design of the antenna elements. movement of the annulus 32 which in practice has a mean position approximately wave length from aperture 23. p

The exact length of the stub chamber 3| will transmission system. For the upper antenna array No. 2. the innermostcoriductor 44 and its conductive shield ll provide the necessary feeder circuit.

Ihe central conductor 44 as stated is concentrically located within conductive shield 11 and is maintained in this position by a plurality of solid dielectric spacers as, for example, 5!, which may be made one-half wave length long to preclude undesirable impedance mismatches along the line.

At point 52 of the innermost conductor 44, an extension lead 53 is joined thereto. 52 is located on the longitudinal axis of the matching stub and accordingly within the matching stub 25 an arrangement of three concentric conductors eXistsas in the main section of the antenna structure/ The conductor 53 extends through its shielding conductor 27 and beyond the matching stub 25 and terminates at the coupling unit 54 which comprises essentially a threaded section of the conductor 21. v

The outer shield 250i the matching stub is extended at 55 to enclose an additional section of the shield 21. Accordingly, at coupling unit 54, a connector from a coaxial cable may be attached so that the shield of the coaxial cable contacts the innermost conductor 21 of the concentric antenna 7 arrangement.

Thus, energy may be fed from the coaxial cable coupling to the antenna structure at 54 through the coaxial line comprising the central conductor 53 and the outer conductor 21 to the junction A further control is provided by axial of course be determined by experimental means.

It is thus clear from the foregoing that the lower antenna array comprising the antenna elements I2 is energized by a coaxial feeding system cornprising an outer conductor II and an inner concentric conductor IT. This coaxial section of conductors which feeds the unit antenna elements is terminated at 22. The feeding system illustrated for the unit antenna l2 thus corresponds in many respects to conventional feeding systems for a single antenna structure.

The upper end of the outer conductor II, as previously described, supports the antenna elements of the upper antenna array No. 2 and is capped by a metallic plate 4|. 7

Between the metallic termination 22 and the cap 4! in the outer conductor H, a coaxial resonator 43 is formed by the conductor I l and conductor 42 concentric with conductor II.

The concentric line conductor 42 is the flared extension of feeder 44 which extends upwardly along the axis of the cylindrical conductor ll. Accordingly, the concentric feeder system extending through the lower antenna array comprises three concentrically spaced conductive members. For the lower antenna array No. l, the conductors II and I7 form the necessary thereof with the central conductor 44 and the outer conductor 11. This coaxial system feeds energy up through the antenna structure illustrated to the concentric arrangement of coaxial conductors I l and 42 in the upper antenna array As illustrated, the conductor I! is flared at 6! to connect with conductor H, and the central conductor 44 is flared at 62 to form concentric conductor 42. Hollow concentric conductors H and 42 form therebetween a resonant chamber 43. This chamber 43 terminates at the upper end thereof in the metallic-cap 41. Although the diameters of the inner and outer conductors of the coaxial system feeding the resonant chamber 43 are altered beyond the metallic terminal 22, it is well known that the characteristic impedance of th line may be maintained at a constant value if a proper ratio of conductive diameters is maintained.

The antenna elements I3 of the upper antenna array No. 2 terminate within the chamber 43 between the inner and outer concentric conductors II and 42 through apertures formed in conductor H and suitably insulated therefrom.

The amount of penetration of the driving terminals of the antenna elements 13 through the apertures and the specific design of the antenna elements control the input impedance to antenna array No. 2. A further control is provided by a tuning stub as will now be described.

At the lower end of the antenna structure, the central conductor i1 is extended below the junction point 52 in order to provide a matching stub 63 for the feeder system comprising central conductor 44 and its associated shield conductor IT. The matching stub 63 is tuned by a metallic shorting bar 65 which may be experimentally axially positionedto provide a matching impedance for the transmission line such that maximum energy transfer will take place from the The point input at coupling unit 54 to the resonant chamber 43 of the upper antenna array No. 2. The member 65 (Figure 1)- will in practice have a mean position approximately wave length from aperture 26.

It is thus evident that at coupling unit 54 a concentric line may be jointed thereto in order to energize the upper antenna array No. 2. The energy transmitted to the upper antenna array is confined entirely to an electromagnetic field within conductor H. In this manner, the electromagnetic energy fed to resonator section 43 extends concentric with the resonator energizing the lower antenna array No. l, but, as is evident from Figure I, cannot affect the field within resonator 2!. The field within resonator 2! is in turn energized by a coaxial system extending from coupling unit I5 and comprising the outer metallic shield l l and the concentric conductor 11.

Thus, the conductor ll acts as a common dividing barrier and restricts the electromagnetic en ergy to the space between itself and either of the concentric conductors shown.

Since each of the feeding systems for the antenna arrays is completely shielded from the other feeding systems, mutual interference is completely eliminated. Furthermore, within each of the coupling units for the antenna arrays, a matching stub is provided for the resonator of the other antenna array.

It is evident that the antenna arrays No. 1 and No. 2 may be energized singly or simultaneously at different frequencies without cross-coupling therebetween. They may simultaneously transmit or receive or may simultaneously transmit over one antenna array and receive on the other antenna array.

The basic concept illustrated in Figure l of a multiple of concentric feeders for an antenna array may be applied to antenna structures in various different manners.

As illustrated in Figure 2, the three concentric conductors may be utilized to energize a single antenna array in such a manner that energy is fed into the center of the unit antenna structure. The application of energy to a radiating system in this manner is of particular advantage where broad band transmission characteristics for an antenna system are desired. As illustrated, an outer hollow conductor H encloses two concentric conductors l2 and 13 which extend to. the center 74 of an array of antenna elements 15 suitably insulated and supported in apertures 10. Of course, as previously mentioned, the antenna array utilized and the extent of penetration thereof through apertures l0 will depend upon the type of transmission characteristics desired, and is not to be considered as part of the present invention.

At point 16 of the innermost conductor '13, an enlarged diameter hollow conductor 11 is attached and extends to the top of the radiating structure. The attached conductor 1! of increased diameter corresponds essentially to the central hollow conductor 12 which terminates at 1B. The energy to be radiated is fed into this antenna structure through the small diameter transmission line formed by the central conductor 13 and its enclosing shield 12.

A suitable coupling unit for a coaxial line which in turn is coupled to the oscillating system may be provided. Energy is transmitted up this coaxial system to point 18 at which point it enters the resonant chamber Bl between enlarged diameter section 11 andthe outer shield H, and resonant chamber 82. between the shield ll and the concentric conductor 12. It is evident therefore that energy flows from the termination. 18 of the small diameter coaxial field transmission line to the upper andIlower section of resonant chamber 8i, and accordingly is fed to the center pletely avoided. The duplex antenna structure illustrated and described above is of course subject to many modifications without altering the basic. concept of absence of cross-coupling and other interference. a i

I thus prefer not to be bound by the specific disclosures hereinabove set forth, but only by the appended claims.

I claim: i i

1. In a system for feeding a plurality of antenna arrays; a first pair of concentric conductors, an antenna array terminating. in the chamber formed by said concentricconductors; a second pair of concentric conductors, an extension of the inner conductor of said first pair constituting the outer conductor of said second pair of concentric conductors and an antenna array terminating in the chamber formed by said second pair of concentric conductors.

2. In a system for feeding a plurality of antenna arrays; a first resonant hollow chamber comprising a first outer cylindrical wall, a firs inner concentric wall forming with said outer cylindrical wall said, first resonant hollow chamber and having a closed end and having a circuit connection at its opposite end for electrically exciting said first chamber, a second resonant hollow chamber comprising a second outer cylindrical wall, a second inner concentric wall forming with, said second outer cylindrical wall said second resonant hollow chamber, said second chamber being mounted in axial alignment with said first chamber and having a circuit connection at its end juxtaposed to said first chamber for electri-- cally exciting said second chamber. a 3'. In a. system for feeding a; plurality of antenna arrays; a first resonant chamber comprising a cylindrical wall member and having a closed end and having a, circuit connection at its opposite end for electrically exciting said chamber, a second resonant chamber comprising a cylindrical wall member mounted in axial alignment with said first chamber and having a circuit connection at its end juxtaposed to said first chamber for electrically exciting said second chamber, and means whereby said last mentioned circuit connection extends longitudinally along said first chamber without electrical interference therewith.

4. In a system for feedinga plurality of ans tenna arrays; a plurality of hollow resonant chambers in axial alignment; each chamber comprising cylindrical wall members; circuit means for independently exciting eachof said antenna arrays from one end. of said axially aligned chambers, and means rorpreventing terference between said exciting means or one of said resonant chambers and any other resonant chamber.

5. In a system for feeding a plurality of antenna arrays; a plurality of hollow resonant chambers, each of said chambers being formed between an inner and outer concentric wall, the extension of the inner concentric wall comprising a wall of another of said chambers and conductor means extending along the axis of said one of said chambers for feeding current to said another of said chambers.

6. In a system for feeding a plurality of antenna arrays; a plurality of hollow resonant chambers in axial alignment; each chamber comprising cylindrical wall members; circuit means for independently exciting each of said antenna arrays from one end of said axially aligned chambers and a shield extending along the longitudinal axis of said chambers for said circuit means.

7. In a system, a plurality of antenna arrays; a plurality of hollow resonant chambers in axial alignment; each chamber comprising cylindrical wall members; circuit means for independently exciting each of said antenna arrays from one of said axially aligned chambers and a shield extending along the longitudinal axis of said chambers for said circuit means, each of said chambers having individual tuning means.

8. In a system for feeding a plurality of antenna arrays, a first section comprising an outer cylindrical wall; an inner concentric wall formingwith said first wall a hollow chamber, a conductor extending along the axis of said walls and a closure terminating said chamber at one end; a second section comprising an outer cylindrical wall, an inner concentric wall forming with said first wall a hollow cylindrical chamber, said conductor fiaring out at the end of said first hollow chamber and forming said inner concentric wall, and the extension of said first mentioned inner wall forming said second mentioned wall.

9. In a system for feeding a plurality of antenna arrays, a first section comprising an outer cylindrical wall; an inner concentric wall forming with said first wall a hollow chamber, a conductor extending along the axis of said walls and a closure terminating said chamber at one,

end; a second section comprising an outer cylindrical wall, an inner concentric wall forming with said first wall a hollow cylindrical chamber, said conductor flaring out at the end of said first hollow chamber and forming said inner concentric wall, and the extension of said first mentioned inner wall forming said second mentioned wall, and an aperture at one end of said first section and means for providing circuit connections to said conductor through said perforation.

10. In combination, a plurality of antenna arrays, each of said arrays being stacked end to end with respect to each other; means including independent feeder systems individual to each antenna array for individually energizing its associated antenna arrays from one end of said stack, and means for precluding electrical interference between antenna radiation of said arrays and said feeder system.

11. In combination, a plurality of antenna arrays, each of said arrays being stacked end to end with respect to each other; 7 means including independent feeder systems individual to each antenna array for energizingall of said antenna arrays from one end of said stack, each individual antenna array comprising a coaxial resonator short circuited at the upper end thereof, antenna elements coupled into each of the resonators, and a coaxial line for individually driving each antenna array.

12. In combination, a plurality of antenna arrays, each of said arrays being stacked end to end with respect to each other; means including independent feeder systems individual to each antenna array for energizing all of said antenna arrays from one end of said stack, each individual antenna array comprising a coaxial resonator short circuited at the upper end thereof, antenna elements coupled into each of the resonators, and a coaxial line for individually driving each antenna array from its lower end;

13. In combination, a plurality of antenna arrays, each of said arrays being stacked end to end with respect to each other; means including independent feeder systems individual to each antenna array for energizing all of said antenna arrays from one end of said stack, each individual antenna array comprising a coaxial resonator short circuited at the upper end thereof, and antenna elements coupled into its associated resonator at half wave intervals.

14. In combination, a plurality of antenna arrays, each of said arrays being stacked end to end with respect to each other; means including independent feeder systems individual to each antenna array for energizing all of said antenna arrays from one end of said stack, each individual antenna array comprising a coaxial resonator short circuited at the upper end thereof, and antenna elements coupled into its associated resonator, the inner conductor of the resonator for the lower antenna array being hollow and supporting therein a coaxial line for driving the coaxial resonator of the upper antenna array.

15. In a system for feeding a plurality of antenna arrays; a plurality of hollow conducting chambers in axial alignment; circuit means for independently exciting each of said antenna arrays from one end of said axially aligned chambers, and a tuning stub connected to one of said conducting chambers and forming the energizing connection for the other of said conducting chambers.

16. In an electrical system, a first and second coaxial hollow conductor forming therebetween a resonant chamber, an extension of said first hollow conductor, a conductor extending along the axis of said hollowconductors and forming a hollow conductor coaxial with the extending conductor; said last mentioned conductors forming a second resonant chamber, a tuning stub for said first mentioned resonant chamber connected to said first and second conductors at apertures therein, said conductor extending along the axis of said tuning stub and forming the excitation conductor for said second resonant chamber.

17. In an electrical system, a first and second coaxial hollow conductor forming therebetween a resonant chamber, an extension of said first hollow conductor, a conductor extending along the axis of said hollow conductors and forming a hollow conductor coaxial with the extending conductor; said last mentioned conductor forming a second resonant chamber, a tuning stub for said first mentioned resonant chamber connected to said first and second conductors at apertures therein, said conductor extending along the axis of said tuning stub and forming the excitation conductor for said second resonant chamber,

and a tuning stub for said second resonant chamber, and form ng the excitation conductor for said resonant chamber.

18. In a system for an antenna array, a resonant chamber; a feeder circuit including a conductor for exciting said chamber and a shield for said conductor extending up into said chamber and terminating at an intermediate section in said chamber, and an enlarged hollow conductor secured to said conductor at said intermediate section and extending longitudinally there rom to form the inner wall thereat of said resonant chamber, whereby said chamber is excited from a point intermediate its ends.

19. In an antenna system. a stack com rising a plurality of antenna arrays, individual feeder circuits, resonant sections for each of said arrays fed from one side of said system, one of said resonant sections terminating one of said antenna structures compriing a hollow cylindrical cond ctor and a second hollow concentric conductor, and a tuning stub connected to the co axial resonator associated with the lower antenna structure and containing the central conductor of the lower antenna structure, said tuning stub comprising the central feeder for the upper antenna array.

20. In a system for feeding a plurality of antenna arrays; a first pair of concentric conductors, an antenna array terminating in the chamber formed by said concentric conductors; a second pair of concentric conductors, an extension of the inner conductor of said first pair constituting the outer conductor of said second pair of concentric conductors and an antenna array terminating in the chamber formed by said second pair of concentric conductors, and a central conductor extending along the axis of said first pair of conductors and forming the inner concentric conductor of said second pair of conductors.

21. In an electrical system, a first pair of conductors comprising an inner and outer coaxial conductor and forming a first resonant chamber, a second pair of coaxial conductors forming a second resonant chamber and comprising an inner and an outer coaxial conductor, an extension of the outer conductor of said first pair of coaxial conductors being the inner conductor of the second pair of said coaxial conductors, said first resonant chamber extending from the end of said second resonant chamber, a T-joint in said first pair of conductors, a T-joint in said second pair of conductors, and means for energizing the said first pair of conductors from one branch of said T-joint, and means for energizing said second pair of coaxial conductors from said second branch of said T-joint.

22. A triple-conductor coaxial system comprising an inner and outer coaxial conductor and forming a first resonant chamber, a second pair of coaxial conductors forming a second resonant chamber and comprising an inner and an outer coaxial conductor, an extension of the outer conductor of said first pair of coaxial conductors being the inner conductor of the second pair of said coaxial conductors, said first resonant chamber extending from the end of said second resonant chamber, a T-joint in said triple-conductor coaxial system, a short-circuiting plug in the inner circuit of said coaxial system placed a quarter-wave length away from said T-J'oint along one branch of said T-connection, input terminals for feeding energy into said outer circuit of said triple-coaxial system in the same branch of said T-joint, the short-circuiting stub placed in the outer circuit of said system onequarter of a wave length from said T-joint, and input connections in the same other branch of Tjoint for introducing energy into said inner circuit of said triple-conductor system.

23. In a system for feeding a plurality of antenna arrays, individual feeder circuit for each of said antenna arrays, a resonant chamher individual to each of said antenna arrays, each of said antenna arrays being connected to their individual resonant chambers for extracting energy therefrom, and means for connecting each of said individual feeder circuits to their individual resonant chambers from one end of said antenna arrays without conflicting with the energy fed to the other of said antenna arrays comprising an outer and. inner coaxial wall forming a first resonant chamber and an inner and outer wall connected to its individual feeder circuit and forming a second resonant chamber, the outer wall of said first chamber extending beyond the end of said first chamber to form the inner Wall of said second chamber at a section beyond the end of said first chamber and connected to its individual feeder circuit.

24. In a system for feeding a plurality of antenna arrays, an individual feeder circuit for each of said antenna arrays, a resonant chamber individual to each of said antenna arrays, each of said antenna arrays being connected to their individual resonant chambers for extracting energy therefrom, means for connecting each of said individual feeder circuits to their individual resonant chambers from one end of said antenna arrays without conflicting with the energy fed to the other of said antenna arrays comprising an outer and inner coaxial wall forming a first resonant chamber and an inner and outer wall connected to its individual feeder circuit and forming a second resonant chamber, the outer wall of said first chamber extending beyond the end of said first chamber to form the inner wall of said second chamber at a section beyond the end of said first chamber and connected to its individual feeder circuit, and the inner wall of said first chamber extending beyond said first chamber and co-axial with the walls of said second chamber for connecting to the feeder circuit individual to said first chamber.

WILLIAM E. BRADLEY.

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

UNITED STATES PATENTS