US2960693A

US2960693A - Antenna support

Info

Publication number: US2960693A
Application number: US714237A
Authority: US
Inventors: Henry J Fry
Original assignee: Melpar Inc
Current assignee: Melpar Inc
Priority date: 1958-02-10
Filing date: 1958-02-10
Publication date: 1960-11-15
Anticipated expiration: 1977-11-15

Description

Nov. 15, 1960 H. J. FRY

ANTENNA SUPPORT Filed Feb. 10, 1958 fig I 1N VENTOR ATTORNEY i at 2,960,693 Patented Nov. 15, 1960 ANTENNA SUPPORT Henry '1. Fry, Arlington, Va., assignor to Melpar, Inc., Falls Church, Va., a'corporation-o'f New York Filed-Feb. 10, 1958, Ser. No. 714,237

4 Claims. (Cl. .343-765) mounted rearwardly thereof The disadvantage of this type of support, that is, having the pivot point behind the antenna, is that 'it requires a very heavy structure "behind the reflector-in order to maintain'the proper surface o'f'the reflector. Also,'the warping effect on-the re- 'flector caused by the antenna feed adds to the requirementof a heavy structurebehind the reflector.

The present invention overcomes this objection-in the preferred form by providing 'asupporting means between the reflector and the antenna feed. This supporting means is located at or near the center of gravity of the antenna device and the pivot-pointis thus placed on the supporting means. The reflector and the antenna feed are attached to an oval-shaped member by tubular rod members. The oval-shaped member is movably mounted -on a yoke member which has drive means attahedthereto and therefor.

-Further, this invention is also concerned with 'an antennadevice that minimizes-the effectivenessofjjamming long-range radar systems. At the present time, many radar installations produce noinformation at all regarding theazimuth position of an incoming aircraftbecause the jammingequipment onzthe aircraft is capable-of producing a signal on the radar lindicator no matter what the radar antenna bearing position might be. This occurs because the high powerpresently available to jammers is received on the antenna sidelobes although'the-side lobe gain might be some 20 db or more below the' basicantenna gain.

The obvious solution to this jamming problem involves a reduction in the antenna side lobe level. Many 'difierent attemptsat side lobe reduction have been-undertaken during the past years. The results of the majofity of these attempts indicate only marginal success. -In general, these radar systems were all concerned'with reductions in the close-in side lobes which are caused by diflraction phenomena. These side lobes are-normally associated with the edge eflects of the'reflector or lens forming the antenna and, consequently, cannot be eliminated and only-with great difiiculty can bereducedbelow 30 db.

Theside lobe problem associated with minimizing the effect of an airborne jamrner is considerably diiterent from that of minimizing close-in lobes. This problem involves levels of the order-of 50 db down; the side lobe reduction is not required in regions close to "the main beam but, rather, in regions away from the beam. These lobes are normally associated not with diffraction but, rather, with scattering of energy fromthe reflector edges and from the feed assembly. It is possible to minimize this scattered energy by obtaining side lobes of-the order of 50 db. This type of side lobe reduction is carried out by encasing the antenna in'a tunnel-like structure which surrounds'the reflector 'and effectively capturesthe scattered energy. One end of the tunnel is fastened to the reflector, while the other end serves as'the antenna aperture.

An object of the present invention is the provision of a movably mounted antenna device Which may be tilted during rotation by power means.

Another object is rto'provide an adjustable construction of the-antenna device mounting whereby it may bemoved to any azimuth settingup to the full 360, and raised to any desired angle of 'elevation.

A further object of the invention is the provision'of a movably mounted radar antenna device having a side 'lobereduction tunnel for minimizing the effectiveness of jamming a radar system.

Still another object is to provide a considerablylighter antenna device that can be constructed so that the reflector surface has a minimum of external forces tending to warp it and consequently requires a minimum of structural parts.

An additionalobject is-the provision of-an antenna reflector which needs only 'a surface capable of supporting its own weight and'shape substantially at the 'center of gravity of the antenna device.

These and other objects of the present invention are realized by the provision of supporting a movably mounted oval-shaped member on a vertical rotatable yoke substantially at the-centero'fgravity of the antenna device. The oval-shaped member further supports a paraboloidal reflector and'an antenna feedassem'bly :by means of rod members and the like which are attached to the ovaltration only, and not as a limitationupon .the scope of the'invention, which is defined in the appended claims.

In the drawings: Figure 1 is a perspective view of'the preferred embodiment of the present invention'applieditothereflector of a search radar installation;

Figure 2 is a sideview of Figure -l; and Figure 3 is za mo'dified form of thepresent invention using a tunnel'structure.

'In accordance withone embodiment of the invention,

as illustrated rinFigures '1 and 2, the antenna device which is indicated "by reference numeral 10, has a-stationary base plate '12 upon .WhiCh the antenna device 10 is placed thereon. rAacasing 14 is mounted on the .base 12 forhousingtherotatingmeans which is comprised of a gearing-assembly :16 anda-motor 18. .A yoke '20.-has

uprightly outwardly curved bar portions 22, 2'4 and a "vertical shaft portion 26'which is rigidly connected downwardly to the midway junetional point of the bar portions :22, 24. The .vertical shaft .26 is rotated by the driven gearing assembly 16.

'An' oval-s'haped member 28 is pivotably .mounted on the uppermost-ends-of the

bar portions

22, 24. The oval-shaped member 28 iscurved with the exception of a flat bottom ,portion 30, the purpose of which will more fully appear hereinafter. A platform 32 is located at one of the uppermost ends of the bar portion 24 and has mounted thereona gearing assemble 34-and a motor 36. This

driving mechanism

34, 36 engages the substantially vertically disposed, metallic oval-like member 28 which is supported in spaced relation from a paraboloidalreflector 38 by a plurality of radially spacedapart tubular rod members 40. The rod members shown "on the lower side thereof are angular-1y disposed relative to the horizontal to contact the flat bottom portion 30 of the oval-shaped member 28. The reflector 38 is fed by a horizontally polarized electromagnetic wave through a wave guide 42 and a feeder 44 from a transmitter (not shown). The feeder 44 is rigidly connected to the oval-shaped member 28 by the wave guide 42 and by a pair of tubular rod members 46. The entire feeding means is positioned below the horizontal scanning plane and the reflector axis. The energy is reflected in a predetermined pattern which is controlled by the configuration and size of the reflector 38.

Referring to the two arrows in Fig. 1, it is readily seen that the antenna device may be continuously rotated by the driving mechanism 16, 18 in azimuth and selectively tilted by another

driving mechanism

34, 36 during rotation to any desired angle of elevation. Further, the yoke supporting means 20 is located at or near the center of gravity of the antenna device which gives a more reliable, rigid, and lighter type of antenna support thereof.

In another embodiment of the invention which is illustrated in Fig. 3, the structure of the antenna device is similar to that of the embodiment of Figs. 1 and 2 with the following exception. A solid wall member 48 which has a tunnel-like configuration is utilized in lieu of the open cage-like structure disclosed in the preferred embodiment. The feeder 44 is spaced from the bottom of the tunnel 48. The tunnel has a reflector that is mounted at one end thereof and the other end extends substantially beyond the feeder 44 and serves as the antenna aperture. The tunnel 48 is pivotably mounted by a yoke 20 and drive means similar to the preferred form. Likewise, the tunnel antenna device may be continuously rotated and selectively tilted by said drive means.

The tunnel 48 and the supporting yoke structure are of a novel design. The skin of the tunnel 48 is the same as the surface of the antenna and the hairflex is preferably laced to the tunnel surface 48 with nylon thread. The tunnel 48 can be made so that complete sections of the tunnel and the hairfiex can be fabricated elsewhere and joined together at the antenna site. The structure as shown is a truss type design which provides lightness and incorporated convenient points of dismantlement for ease of transportation.

An experiemental investigation of side lobe reduction through the use of specific tunnel techniques indicates that a 40 db to 50 db reduction is possible in the 60 to 180region with only slight loss in gain and slight increase in beam width at the lesser tunnel depths. In the extreme tunnel depths a reduction of the near side lobes is possible but an added loss in gain appears at these depths and tunnel configurations.

The above described tunnel construction has been found to reduce considerably secondary lobe formation, for example, to such an extent as to improve greatly the operation of aircraft landing systems embodying the same.

Thus, the invention, as illustrated in Figure 3, comprises obtaining a reduction of objectionable side lobes in the radiation pattern by thepredetermined construction of the tunnel.

Although the invention has been described with reference to the transmission of radio energy it will be apparent to those skilled in the art that the constructions described herein may also be used for reception of other energy.

Further, while there has been here described what is at present considered two embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention.

What is claimed is:

1. In a radar antenna device, a compact balanced antenna unit comprising a paraboloidal reflector having a plane of symmetry which substantially includes the axis of the radiation pattern therefrom, a feeder means for furnishing thereto electromagnetic wave energy having a polarization axis parallel both to said reflector and to said symmetrical plane, said feeder means being located in a plane parallel and contiguous to said symmetrical plane of said reflector to accommodate the passage of the radiated energy thereto, oval-shaped means for supporting said reflector and said feeder means, said oval-shaped means having flat portions to permit the radiated energy to be distributed more readily from said feeder means to said reflector; a yoke member having a vertical shaft portion and upwardly outwardly curved bar portions for supporting said oval-shaped means on the upper ends of said bar portions whereby said antenna unit is maintained in a balanced condition; drive means engaging said oval-shaped means for selectively tilting said antenna unit to any desired angle of elevation; and additional drive means engaging said vertical shaft portion for rotating said antenna unit in azimuth.

2. In a radar antenna device, a compact balanced antenna unit comprising a paraboloidal reflector having a plane of symmetry which substantially includes the axis of the radiation pattern therefrom, a feeder means for furnishing thereto electromagnetic wave energy having a polarization axis parallel both to said reflector and to said symmetrical plane, said feeder means being located in a plane parallel and contiguous to said symmetrical plane of said reflector to accommodate the passage of the radiated energy thereto, oval-shaped member for supporting said reflector and said feeder means, said oval-shaped member having a plurality of supporting rods rigidly fastening said oval-shaped member to the outer periphery of said reflector, said oval-shaped member having flat portions to permit the radiated energy to be distributed more readily from said feeder means to said reflector; a yoke member having a vertical shaft portion and upwardly outwardly curved bar portions for supporting said oval-shaped member on the upper ends of said bar portions whereby said antenna unit is maintained in a balanced condition; drive means engaging said oval-shaped member for selectively tilting said antenna unit to any desired angle of elevation; and additional drive means engaging said vertical shaft portion for rotating said antenna unit in azimuth.

3. In a radar antenna device, a compact balanced antenna unit comprising a paraboloidal reflector having a plane of symmetry which substantially includes the axis of the radiation pattern therefrom, a feeder means for furnishing thereto electromagnetic wave energy having a polarization axis parallel both to said reflector and to said symmetrical plane, said feeder means being located in a plane parallel and contiguous to said symmetrical plane of said reflector to accommodate the passage of the radiated energy thereto, a solid Wall oval-shaped member for supporting said reflector and said feeder means, said oval-shaped member having flat portions to more readily permit the radiated energy to be distributed from said feeder means to said reflector; a yoke member having a vertical shaft portion and upwardly outwardly curved bar portions for supporting said oval-shaped member on the upper ends of said bar portions whereby said antenna unit is maintained in a balanced condition; drive means engaging said oval-shaped member for selectively tilting said antenna unit to any desired angle of elevation; and additional drive means engaging said vertical shaft portion for rotating said antenna unit in azimuth.

4. A radar antenna device comprising a stationary base, means including a vertical shaft for rotating said antenna device in azimuth, a casing mounted on said base for housing said rotating means; a yoke member including said vertical shaft and uprightly outwardly curved bars; an oval-shaped member pivotably mounted on the ends of said bars, said oval-shaped member having a flat bottom portion; means mounted at one of the ends of said bar portions for moving said oval-shaped member to any desired angle of elevation; at paraboloidal reflector; a plurality of supporting rods rigidly fastening said ovalshaped member to the outer periphery of said reflector, several of said supporting rods are bent downwardly to engage said flat bottom portion; a feeder means positioned at a lower level than said reflector for furnishing electromagnetic wave energy to said reflector; a plurality of additional supporting rods rigidly fastening said feeder means to said oval-shaped member, one of said additional rods constituting a wave guide member; the structural arrangement of said flat-bottomed oval-shaped member and of said bent supporting rods allowing the radiated energy from said feeder means to be distributed more readily over said paraboloidal reflector.

References Cited in the file of this patent UNITED STATES PATENTS 2,530,098 Van Atta Nov. 14, 1950 2,554,119 Perham May 22, 1951 2,617,032 Allison Nov. 4, 1952 2,719,921 Cairnes Oct. 4, 1955 2,842,767 Darrouzet July 8, 1958 2,877,459 Brown et a1 Mar. 10, 1959