US3509571A - Radome antenna - Google Patents

Description

Apr-'il 28, 1970 H. s. JONES, JR ET AL 3,509,571

RADOME ANTENNA Filed June 16. 1967 Us. Cl. 343-771 4 Claims ABSTRACT OF THE DISCLOSURE An integrated radome antenna structure fully utilizing the dielectric material from which a radome is fabricated., The elemental antenna is a slotted array designed from metallic-plated, dielectric-loaded, wave-guide which is an integral part of the radomeD The wave-guide is formed on the radome by copper plating the inner and outer surfaces of the radome to form the at longitudinal surfaces of the wave-guideo The edges of the wave-guide are formed by interlacing a mesh wire partition transverse to the surface of the radome The result is a completely enclosed di electric filled cavity for use as an antenna radiator, when slots are placed thereina (CROSS REFERENCE TO RELATED APPLICATION Sen No., 417,523 filed Dec., 10, 1964, now Patent No., 3,346,865 by Howard Sa Jones, JrD

BACKGROUND OF THE INVENTION' Airborne or vehicle carried radar equipment is almost always covered by a plastic or dielectric radome which is substantially transparent to electromagnetic energy but which provides mechanical protection for the equipment and contributes to the streamlining on the vehicle. Situated within the radome itself is the antenna system for the radar equipment., Although such structures have served their purpose satisfactorily in the past, they have become less satisfactory with the increased complexity and sophis-5 tication of todays modern radar equipment, and there has been a pressing need for a reduction in both bulk and cost of radar equipment, With. the advent of simple and compact phase shifting devices electrical scanning of radar antennas has become practical, and several actuated an= tenna arrays have been replaced with xed arrays,1 There has thus resulted some decrease in size, weight and expense in radar equipment. However, these improvements while abating the problem have not eliminated it., The search for other and more adequate solutions has continued focusing attention on the radar antenna structure itselt, and various attempts have been made to mount the antenna flush with the skin of the vehicle to achieve a reduction in the bulk of the equipmenta Until the applicants discovered that the antenna could be integrated with the radome, these attempts had not been entirely satisfactory, )In prior art devices very little use has been made of radomes other than for mechanical purposes. However, as described in application SerH No 417,523 tiled Dec 10, 1964 by applicant iones, an investigation into the design of a class of dielectric-loaded, slotted wave-guide antennas suggested the possibility of incorporating antennas of this type into radome structures. A further study indicated a high degree of compatibility between this type of antenna and radome designs commonly used in guided missiles, For example, most of the dielectric materials used today in the construction of radomes are the same as the dielec tric substrates used in the design of flat dielectric loaded slot arrays Moreover, the thickness of the material used can be thel samen .ln the abovementioned copending application the ari-- 3,509,57l Patented Apr, 28, 197@ tenna described is a slotted wave-guide antenna array fabricated as an integral part of' a dielectric radome cir cuit The wave-guide for the array is formed by drilling holes through the radome surface at close intervals in rectangular pattern to form the perimeter of the wave-guide section.7 The holes as well as the exterior and interior surfaces of the radome enclosed by them are electroplated with copper or other suitable metal, The result is a waveguide section, the broad walls of which are formed by the plated portions of the inner and outer surfaces of the radome, and the edges of which are formed by the electroplated holes through the radomeL Of course, provisions are made to leave radiating slots on the broad exterior face of the wave-guide in the electroplating process This technique has resulted in a highly satisfactory and very compact radar antenna system, It has been found in use, however, that this mode of construction. weakens the radome itselfu It is therefore an object of this invention to provide a radar antenna which occupies no space Within the radome, is extremely light weight, and is very inexpensive to .manufacturea lt is another object of this invention to provide a radar antenna integrated with the radome while not impairing the strength of the radome,

It is further object of this invention to provide a radome-antenna configuration which will permit simultane ous manufacture of the antenna with the radomeu BRIEF DESCRIPTION OF THE DRAWINGS The specific nature of the invention, as well as other objects, aspects, uses, and advantages thereof, will clearly appear from the following description and from the accompanying drawing in which:

FIGURE l is a typical embodiment of our invention utilizing a cylindrical radome section which is cut away to give a side view of the slotted wave-guide.

FIGURE 2 is another embodiment of our invention shown in a conical radome which has been cut away to give a top-crosssectional View of the slotted wave-glide section,

FIGURE 2a: is a view of the bottom broad wall and the wires forming the edges ot' the `.waveguide section shown in FIGURE 2., ""i

FIGURE 3 is a side cross-sectional view of the wave guide section of the embodiment of FIGURE l showing the means by which a signal is coupled to the antenna.

DESCRIPTION OF T PREFERRED EMBODIMENTS Referring to FIGURE l of the drawings, there are shown slotted wave-guide antenna arrays 11 and 12 fabri cated as an integral part of a cylindrical dielectric radome section 10 A side view of slotted wave-guide antenna array 1]. is shown by cutting away a portion of radome 10 so that an isometric cross-section is obtainede Radome l@ is of a conventional type made of xyybeeglass, but the entire interior surface 17 of radomeldhasheenplated with copper., The edges of wave-guide section 11 are formed by lacing wire 13 through the thickness of the radome transverse to its surfaces. The laced wire pattern, such as that shown in FIGURE 1, formed by wire 13 is a coniiguration that will minimize the radiation of electromagnetic energy along the edges while at the same time maintaining the strength of the radome at this juncturea TheA portion of the outer surface of radome 10 within the perimeter formed by laced wire 13 is plated with cop per to form the broad outer Wall 14 of wave-guide section ille. As a result of the above described construction tech nique, a radome-antenna combination of sufficient strength to withstand the rigors of a military environment sangen is obtained with electrical characteristics similar to the radome-antenna combination described in 'application Ser., No. 417,523, mentioned above Another embodiment of our inventionis shown in FIG. URE 2. In this embodiment the laced wire described in the embodiment of FIGURE 1 is replaced with rigid wires spaced close together in vertical position in a rectangular pattern to form the edges of: the wave-guide. In FIGURE 2 a conventional conical fiber glass radome is shown with a section thereof cut away to reveal the construction of the slotted wave-guide. Although not shown in the figure, the entire interior surface of radome 20 is copper plated, as was the case in the embodiment of FIGURE 1, Rigid wires 23 are placed in a vertical position on the interior copper plate in a rectangular pattern so that a wave-guide, such as that shown in FIG- URE 1, will be formed. The wires 23 must be placed closely together to minimize the electromagnetic energy that could be radiated along the edges, while at the same time maintaining the strength of the radome at this juncture. Once the wires are in place, the resin impregnated glass filament winding layers are interlaced through the wires until the desired radome thickness is achieved. When the radome is subjected to its curing temperature under pressure, it will produce a unified solid structure. The top broad Wall of the wave-guide can then be formed by copper plating the outer surface of the radome 20 within the perimeter formed by wires 23.

The mode of construction described in FIGURE 2 is more clearly shown by reference to FIGURE 2a in which is shown a thin metal sheet 25 which would form the interior surface of the radome. Wires 23 are placed in a vertical position in a rectangular pattern on the metal sheet.tSheet 25 with wires 23 in place is positioned on the mandrel that is used to lay-up the radome, and the layers of ber glass are placed on sheet 25 being interlaced through wires 23.

In FIGURE 3 is shown the means by which a signal is coupled to the radome antenna described in FIGURE 1 or FIGURE 2. In FIGURE 3 is shown a side cross-secm tional view of the radome-antenna of FIGURE 1 in which like numbers describe like elements. The waveguide antenna is excited from a standard coaxial waven guide input 31 located along a longitudinal center line a length equal to one quarter wave length of the signal to be transmitted in the dielectric medium away from the row of wires 13 forming an end wall of the wave guiden The -at dielectric has a low impedance and matches very well with a 50 ohm coaxial input An antenna system designed as an integral part of a radome fully utilizing the dielectric radome structure herein described has been developed and constructed. The results of an evaluation of the electrical performance were excellent compared with those of conventional systems and the antennas constructed as herein described d have been found to have sufficient strength to withstand the stresses and strains introduced by military applications.,

It will be apparent that the embodiments shown are only exemplary and that various modification can be made in construction, such as using different dielectric materials, different plating metals and plating processes, and arrangement, such as different antenna congurations, within the scope of the invention as defined in the appended claims;

We claim:

'1. An integral radome-antenna structure comprising:

(a) a radome made of thin low loss dielectric material having an interior and exterior surface, the interior surface of said radome being completely plated with a conductive metal,

(b) a metal wire partition perpendicular to the inm terior and exterior surfaces of said radome enclosing an area of said surfaces of said radome and placed between said surfaces,

(c) said exterior surface of said radome being plated with a metal within the perimeter formed by said partition, whereby said partition and the portions of said interior and exterior surfaces of said radome enclosed by said partition form a wave-guide.

(d) at. least one radiating slot in an exterior surface of said wave-guide,

(e) connecting means adapted to receive a signal to be transmitted and to conduct said signal into said wave-guide.

2. The integral radome antenna of claim I in which said connecting means is positioned a distance equal to one-quarter wave length of the signal to be transmitted from an end of said wave-guide on the longitudinal center of said 'wave-guideB 3. The integral radome-antenna of claim I wherein said partition comprises a wire laced through the thickness of said radomeD 4. The integral radome-antenna of claim 1 wherein said partition com-prises a plurality of vertical wires set in said plated inner surface of said radome, said wires being perpendicular to said inner surface and extending to said outer surfaceH References Cited UNITED STATES PATENTS 2,761,137 8/1956 Van Atta et al. 343--785 3,155,975 11/1964 Chatelain a 343-785 ELI LIEBERMAN, Primary Examiner USt CL XR, 343-708, 872

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