US 3005986 A
Description (OCR text may contain errors)
Oct. 24, 1961 R. H. REED 3,
PARALLEL STRIP TRANSMISSION ANTENNA ARRAY Filed June 1, 1956 A TTORNE Y.
United States Patent j 3,005,986 PARALLEL STRIP TRANsMIssroN ANTENNA ARRAY RichardH. Reed, Los Angeles, Calif., assignor to Hughes Aircraft Company, Culver City, Caiifi, a corporation of Delaware Filed June 1, 1956, SenNo. 588,921 6 Claims. (Cl. 343-810) This invention relates to antenna arrays, and particularly to microwave antenna arrays which are light, rugged and compact.
Antenna arrays for aircraft and other mobile installations usually should be of minimum size and weight. Such arrays usually should conform to the streamlining of the airplane and, preferably, should be integral with the aircraft structure. For these purposes, the arrays are usually associated with a protective radome of the desired shape. Antenna arrays heretofore built have usually required that the components of the array provide mechanical rigidity as Well as the desired electrical characteristics. Such construction usually substantially increases the size and weight of the energy transmitting and radiating elements. In addition, further elements often are needed witirthis construction to support-the array from the ground plane. These factors have heretofore meant that dipole arrays could not be employed, except in a few locations, without materially decreasing the streamlining of the installation in which they were employed. In particular, it has heretofore been difiicult to arrange a light and compact streamlined array providing desired illumination from a central region of one of the planar surfaces of an aircraft.
lt is therefore an object of this invention to provide an improved antenna array which is characterized by ruggedness, simplicity of construction, compactness and lightness in weight.
It is a further object of this invention to provide an improved dipole array employing a smaller and lighter but at the same time stronger mechanical arrangement than has heretofore been employed in the art.
Yet another object of this invention is to provide an improved microwave dipole array useful in a central region. of a planar surface, which array is extremely compact but at the same time is mechanically strong and also provides desired illumination characteristics.
An antenna array provided in accordance with this invention may be arranged around a plane-surface radome structure. The plane-surface radome may be sandwiched between and. supportthe strips of a parallel-strip transmission line. Radiation patterns may then be provided from flat strip dipole elements extending from each of the strips and, like the strips, sandwiching the radome. With this construction, the transmission line and dipoles may be bonded to the radome, which may itself be honeycombed or otherwise apertured for weight reduction. Such -a structure is extremely light in weight because the electrical elements are fully supported by the radome and need not have independent structural strength. Additionally, the structure is extremely compact because supporting stubs or other means for separating from a ground plane are not necessary.
The novel features of this invention, as well as the invention itself, both as to its organization and method of operation, may best be understood when considered in the" light of the following description, when taken in connection with the accompanying drawing, in which like reference numerals refer to like parts, and in which:
FIG. 1 is a perspective view, partially broken away, of a linear microwave array in accordance with this in- 3,005,986 Patented Oct. 24, 1961.
vention which employs a central feed and a honeycomb radome;
FIG. 2 is a fragmentary View, partly broken away, showing detailed features of the central feed system, the array and the honeycomb radome of the arrangement of FIG. 1;
FIG. 3 is a fragmentary cross-sectional view of the arrangement of FIG. 1, and
FIG. 4 is a simplified perspective view of an aircraft employing two antenna arrays in accordance with the invention.
An arrangement for practicing the invention, referring now to FIG. 1, may employ a plate-like supporting structure 10 or panel of plastic material. The supporting structure 10 may comprise a radome or other structural element for use on an aircraft. The structure 10 may describe a flat or curved planar surface depending on the shape to which it is to conform or the arrangement of the array. The plastic employed may be any one of a number of substances well known in the art which are nonconducting and substantially pervious to electromagnetic wave energy. The structure or panel 10 is preferably multiapertured, the apertures transverse to the. plane of the structure it permitting decreased weight while retaining strength and rigidity. As shown, the apertures may be in a honeycomb pattern. It will be understood, however, that apertures need not be employed and that the material need not even have a low dielectric constant in some applications. Under particular conditions, a solid dielectric might be desired.
A linear antenna array 2! may be arranged on the supporting structure it in a central region of the surface of the structure 10. The linear antenna array 20' comprises a parallel strip transmission line 22 including a pair of fiat elongated transmission strips 24. These transmission strips .24- may be successively widened in step-wise fashion, and also varied in length to provide desired illumination characteristics. The array 20 shown employs two successive steps 26 on each end of the elongated strips 24 to provide a broadside array. The broad faces of the parallel strips 24 are placed against the supporting structure 10 and on opposite side of the supporting structure 16. The two strips 24 are parallel and coextensive with each other. The thickness of the supporting structure 10 is dependent upon the separation between the transmission strips 24, which in. turn is dependent upon the wave length of the energy transmitted. As shown in FIG. 1, supporting structure 10 almost fills the space between the two transmission strips 24. For all practical microwave applications, this provides sufficient thickness to insure structural strength and mechanical rigidity.
Radiating elements 28 are coupled to and substantially normal to each of the parallel strips 24 and have their broad faces against the supporting structure 10'. The radiating elements 28 are flat strip dipole elements roughly corresponding in section to the transmission strips 24 themselves. These radiating elements 28 are preferably made integral with the transmission strips 24 but may be mechanically attached to the strips 24. The radiating elements 28 are arranged in dipole pairs, with the individual members of each pair being coupled to a different transmission strip 24 and thus being on opposite sides of the radome it). The dipoles and transmission strips 24 provide a radiating array which may be called a transmission line radiator.
The transmission line 22 is center fed by a coaxial line 3%} and a coupling probe 32. Transmission lines such as transmission line 22 may, however, be fed elsewhere than at their centers. The arrangement may be seen in more detail in FIGS. 2 and 3, to which figures reference is now made. The transmission lines 24 and the dipole members 28 are mechanically coupled to the supporting structure by suitable nonconductive bonding material 40, such as a glass cloth or other plastic material well known in the art. The bonding material 40 does not disturb the electrical characteristics of the system but does provide firm and positive attachment of the parts of the array to the supporting structure 10. The bonding material 40 may be arranged as a sheet on the supporting structure 10, with the transmission strips 24 and the dipole members 28 being sunk into the bonding material 40. Thus a flush, streamlined surface is provided.
A two-dimensional antenna array (not shown) may be provided by the employment of a second linear antenna array spaced from the first on the same radome, or placed on a second, adjacent radome. The elements of the second array can be like those of the first array and thus need not further be described.
In operation, electromagnetic wave energy fed by the coaxial line 30 to the linear antenna array 20 energizes the system to provide the desired illumination. It will be understood that any two-dimensional illumination desired could be provided by a second linear antenna array in like manner. Energy transmitted along the transmission lines 24 from the center-feed coupling probe 32 will thus be radiated from the dipole members 28. Other desired illuminations can be obtained by adjustment of the characteristic impedance of the line formed by the parallel strips 24.
It will now be apparent that the use of a plate-like supporting structure 10 providing a radome function between associated transmission strips 24 and dipole members 28 bonded to the supporting structure it) provides many improvements over the prior art. A flush antenna array is provided which may be arranged to conform to the outer surfaces of an airplane 50, as shown in FIG. 4. The array might be substantially flat, as shown on the tail surface of the airplane 50, or curved, as may be seen on the airplane 50 body. Further, the array might be spaced away from the body or made flush with the body, as shown. In either arrangement the structure is thinner and more streamlined than the arrays of the prior art. A desired radiation pattern can be provided from any central region of a planar surface, although it will be apparent the device is not restricted to such use. The flat strip elements 28 which are used for dipoles and the transmission lines 24 derive their strength from the supporting structure 10 and need have only minimum structural rigidity. This integral construction also, in efiect, eliminates the need for using spaced supporting stubs extending from a separately disposed ground plane. Prior art dipole arrays have been restricted to a spacing of M4 Wavelengths between the array and the ground plane, and have used supporting stubs of A/ 4 length. With the present array no such restrictions are imposed, and spacings of only A/ 8 have been successfully used.
Thus there has been described an improved antenna array. An integral construction may be used in which a supporting structure is sandwiched between the trans mission strips and dipole elements of an array. By this arrangement the size and weight of the antenna elements may be minimized and the stream-lining and compactness of the array improved.
What is claimed is:
1. A microwave antenna array comprising: a central, substantially nonconductive, planar member having a plurality of transverse apertures; conductive strip members on each side of said planar member and spaced apart from each other, the broad faces of said strip members lying substantially parallel to the plane of said planar member and said strip members each including transmission and radiating elements, said strip members together providing a radiating array; and sheets of bonding material on each side of said planar member, coupling said strip members to said planar member.
2. A microwave antenna array comprising: a substantially nonconductive planer structure having a plurality of transverse apertures defining a honeycomb pattern; two conductive strip members, each adjacent a different side of said planar member and substantially parallel thereto, said strip members each including elongated portions parallel to each other and defining a parallel stn'p transmission line, and also including radiating elements, each individual radiating elements of each of said strip members being paired to an element of the other strip member to form a dipole; two sheets of substantially nonconductive bonding material, each sheet lying between a different one of said strip members and said planar member and coupling them together; and means for feeding wave energy to said transmission line.
3. A microwave antenna array comprising: a substantially nonconductive panel having a plurality of transverse apertures; a transmission line radiator in a central region of the surface of said panel and comprising two flat strips each on a different side of said panel and having a plurality of radiating strips extending outwardly therefrom in the same plane, each radiating strip being paired with and extending oppositely from a radiation strip of the other parallel strip to form a dipole therewith; and two sheets of nonconductive bonding material in the same central region of the surface of said panel, each sheet coupling a different one of said parallel strips to said panel and providing with said strip a flush outer surface for the assembly.
4. A microwave antenna array comprising: a multiapertured planar supporting radome of a material pervious to wave energy; a parallel strip transmission line, the individual ones of said parallel strips being disposed on opposite sides of said radome and adjacent thereto; a plurality of strip dipole members coupled individually to the separate ones of said parallel strips and lying adjacent said radome in the plane of the strips to which they are coupled, each dipole member of one of the parallel strips being paired with and extending oppositely from a dipole member of the other one of the parallel strips to form a dipole therewith; means including a layer of glass cloth for bonding said parallel strip transmission line and said dipoles to said radome; and means including a coaxial line electrically coupled to said parallel strip transmission line and mechanically coupled to said radome for feeding said transmission line.
5. An improved antenna array which is characterized by lightness in weight, simplicity, and compactness, said array comprising: a substantially flat radome having a plurality of apertures forming a honeycomb pattern; a transmission line in a central region of the surface of said radome and comprising coextensive parallel strips, having successively widened portions arranged to provide desired illumination, With the individual ones of the strips being disposed on opposite sides of the radome and lying flat along said radome; a plurality of fiat strip dipole members integral with and extending normally from each individual strip of the transmission line, said dipole members also lying fiat along said radome and being arranged in dipole pairs consisting of a dipole member from each of said strips; bonding means including layers of glass cloth mechanically coupling said parallel strips and said dipole members to said radome, said glass cloth defining a flush surface with said parallel strips and dipole members; and coaxial feed means centrally feeding said transmission line and mechanically coupled to said radome.
6. A dipole array comprising: a multiapertured planar radome member, a parallel strip transmission line coupled to said planar radome member, the strips of said transmission line being disposed on opposite sides of said planar radome member, dipole elements comprising a plurality of strip members coupled individually to the strips of said transmission line and disposed in the planes thereof and extending therefrom at spaced points therealong, and energy feed means coupled to said radome structure anii electrically coupled to said transmission line at a selected point therealong for energizing the dipole elements With energy transmitted along the transmission line.
References Cited in the file of this patent UNIT ED STATES PATENTS 6 Higgins et al. Aug. 5, 1947 Doerner Oct. 14, 1952 Havens July 7, 1953 Arditi et a1. Dec. 11, 1956 Chu Dec. 29, 1959 FOREIGN PATENTS Canada Feb. 15, 1955 Great Britain Aug. 1, 1951