US2908904A - Antenna system - Google Patents

Description

L. c. VAN ATTA. ET AL 2,908,904

ANTENNA SYSTEM Filed Aug. 26, 1955 United "States Patent ANTENNA SYSTEM Lester C. Van Atta and Mack D. Adcock, Pacific Palisades, and Thomas-Kinaga, Los Angeles, Calif., as- I signers to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Application August 26, 1955, Serial No. 530,826

3 Claims. (Cl. 343708) This invention relates to antenna systems, and particularly to radiating antenna arrays which may be used in high speed aircraft.

'. Modern aircraft are increasingly using electronic equipment for. communication and navigation. It is usually essential that there be as little' interference as possible with the normal operation of the aircraft. Specifically, the electronic equipment should be as light in weight as practicable, and introduce as little air resistance as possible.

Structures which employ a portion of the aircraft itself asan antenna structure are known. For example, a portion of a vertical tail surface may be employed as a radiating surface for the aircraft. Such antennas are usullyelectiically isolated from the remainder of the aircraft by a section of dielectric material. When it has been desired to provide an additional antenna array, the mechanical and electrical arrangements have not been entirely satisfactory. The supplemental antenna arrays heretofore used have been heavy or have adversely affected the streamlining of the aircraft, or both. Further, the types of coupling employed to cross the dielectric isolating section have introduced excessive capacitance into the structure, caused excessive signal loss, or increased dangers due to voltage breakdown and lightning discharge: It has been particularly diflicult to provide a supplemental antenna array which has an omnidirectional horizontal pattern, and which at the same time has the desired mechanical properties and which can be fed without the insertion of undesired electrical properties into the system.

.It is therefore an object of this invention to provide an improved aircraft antenna structure having less effect on, aircraft performance and better electrical characteristics than the antennas of the prior art.

It is another object of this invention to provide a compact and lightweight supplemental antenna arrangement for use with an antenna comprised of a portion of an aircraft body.

- It is a further object of this invention to provide an improved supplemental antenna arrangement for an aircraft antenna utilizing an isolated portion of a control surface, the supplemental antenna providing negligible wind resistance and being relatively free from lightning discharge effects, excessive capacitance, and the possibility of voltage breakdown.

; It is still another object of this invention to provide an improved antenna arrangement for aircraft, which arrangement presents a minimum of air resistance and an omnidirectional pattern in the horizontal plane.

' 'It is another object of this invention to provide an improved supplemental antenna arrangement for the vertical control surface of an aircraft.

' An antenna structure in accordance with this invention may utilize as one radiating body a portion of an electrically isolated aircraft vertical control surface. A

supplemental antenna comprising a rectangular wave guide section may be mounted on a topmost portion of 2,908,904 Patented Oct. 13, 1959 ice the vertical control surface. The rectangular waveguide section may have radiating slots in each side parallel to the direction of movement of the aircraft, to provide an omnidirectional pattern in the horizontal .plane and a narrow pattern in the vertical plane. Streamlining sections fore and aft of the supplemental antenna may mini mize the air resistance presented by the antenna without affecting the radiation pattern afforded. Signals may be provided to the supplemental antenna through a dielectric coupling member comprising a dielectric waveguide within a dielectric cover. The dielectric coupling member is arranged to span the elements which electrically isolate the vertical control surface radiating body from the remainder of the aircraft. The dielectric coupling member feeds the supplemental antenna without introducing undesired electrical characteristics into the vertical control surface antenna arrangement.

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, partly broken away, of'a portion of an aircraft employing an antenna arrangement, including a supplemental antenna and a dielectric coupling member, in accordance with this invention;

Fig. 2 is a detailed perspective broken away section of a dielectric coupling member which may be employed in the arrangement of Fig. 1, and

Fig. 3 is a detailed perspective view of a supplemental antenna which may be employed in the arrangement of Fig. 1.

An antenna array in accordance with the invention, referring now to Figs. 1, 2, and 3, may be mounted on and include a portion of an aircraft body 10. The antenna arrangement may include a portion of a vertical I from the remainder of the aircraft 10 by a band of elecelectrical portions.

trically isolating material, such as a dielectric material. The isolating body 16 thus'defines an electrical gap between the tail cap portion 14 and the body of the aircraft 10, and divides the vertical control surface 12 into two The tail cap portion 14 may therefore comprise a planar wave energy radiating structure, and may be fed by energizing means (not shown) mounted in the body of the aircraft 10. The tail cap 14 may be at least partially hollow, or provided with an internal aperture for coupling associated elements.

A supplemental antenna 20 chiefly comprising a rectangular waveguide 22 having radiating slots 24 on the opposite faces thereof, may be mounted on an uppermost point of the tail cap portion 14. The broad faces of the rectangular waveguide 22 are parallel to the normal direction of movement of the aircraft 10, and the radiating slots 24 are provided in each of these broad faces. In accordance with techniques well known in the antenna art, the radiating slots may be so positioned as to provide an omnidirectional pattern in the horizontal plane, and a relatively narrow pattern in the vertical plane. A pair of streamlining sections 26 may be mounted fore and aft, respectively, of the rectangular waveguide 22, to provide a smooth fairing for the rectangular waveguide antenna 22 in the normal direction of movement of the aircraft 10. A dielectric coupling member 30, best seen in Fig. 2, may be employed to bridge the dielectric isolating body 16 shown in Fig. l. The dielectric coupling member 30 may include a central cylindrical dielectric waveguide 32 having slightly expanded end portions 34 and pointed tips 36. A cover comprising a hollow cylindrical dieach end encompasses the central cylindrical dielectric waveguide 32. Each of the end portions 34 of the dielectric waveguide 32 registers with a different one of the horns 40 coupled to the cylindrical shell 38, and forms therewith a transition section. Elongated tips of the horn sections 40 may be coupled to conductive waveguide sections 42, 44 including circular to rectangular transition sections. A first of the conductive waveguides 42 couples the dielectric coupling member 30 to the supplemental antenna 29 through the hollow central section of the tail cap 14. The second of the conductive waveguides 44 couples the dielectric coupling member 30 to the associated electrical epuipment in the aircraft 10. The shell 38 may be pressurized, if desired.

In operation, still referring to the figures of the drawing, the tail cap antenna 14 is energized by a source within the aircraft 10, and thereby provides a radiation pat tern at a frequency band determined by the physical configuration of that portion of the vertical control surface 12. The supplemental antenna 20 mounted on top of the tail cap antenna 14 provides a separate radiation pattern from the pattern provided by the tail cap antenna 14. Note that the rectangular waveguide antenna 22 employed is small with respect to the vertical control surface 12 and that the radiating slots 24 are exposed, to provide the desired omnidirectional horizontal pattern without interference. The streamlining sections 26 reduce the air resistance of the supplemental antenna 22 to a negligible amount, without affecting the radiation pattern of the supplemental antenna 22. Thus the arrangement provided avoids difficulties heretofore encountered through the use of cylindrical waveguides and cumbersome, energy absorbing, radomes.

Electrical isolation of the tail cap antenna 14 from all but the energy supplied directly to it is maintained by the use of the primarily dielectric coupling member 30. Energy provided from the equipment in the aircraft through the conductive waveguide 44 is impressed on one end of the dielectric coupling member 30 at a horn 40. The energy at the horn is transferred to the end 34 of the central cylindrical dielectric waveguide 32, passes along the waveguide 32 to the opposing end, and is transferred through the other horn 40 to the conductive waveguide 42 at the opposing end. The conductive-waveguide 42 impresses the energy on the supplemental antenna 22. The pointed tips 36 on the dielectric waveguide 32 form, with the elongated tips on the horns 40 coupled to the dielectric shell 38, a smooth transition section, without reflection effects, for the transfer of energy.

The presence of this type of dielectric coupling member 30 within the dielectric isolating body 16 maintains the tail cap antenna 14 electrically separate from the remainder of the aircraft 10. Thus the tail cap antenna 14 is protected against voltage breakdown, and no capacitance is introduced beyond the inherent capacitance of the system. Further, dangers due to lightning discharge are also minimized. Note that the cylindrical shell 38 in the dielectric coupling member 30 permits the coupling member 30 to be pressurized, and at the same time provides structural strength and rigidity for the system. The coupling arrangement thus provided may be employed in the microwave frequency range, obviating the need for complicated coupling arrangements heretofore used with other frequencies. The tail cap antenna arrangement will, by its nature, operate in a frequency band materially different from that of the microwave frenquency.

Thus there has been provided an improved antenna structure for employment in aircraft. An omnidirectional horizontal pattern may be provided without disturbing the performance of an antenna integral with the airplane, and without introducing undesired electrical effects or adversely affecting the performance of the integral antenna.

What is claimed is:

1. An antenna structure for employment with an aircraft having a vertical control surface and comprising: a band of dielectric material mounted between the ends of said vertical control surface and separating said surface into two portions, the furthest portion of the vertical control surface from the aircraft body providing a wave energy radiating surface arranged to radiate energy in a first predetermined frequency band; a rectangular waveguide member mounted in the uppermost portion of said furthest portion, said rectangular waveguide including radiating apertures on each side thereof parallel to the longitudinal axis of said vertical control surface and being arranged to radiate energy in a second predetermined frequency band; a pair of streamlining surfaces, mounted fore and aft, respectively, of said rectangular waveguide on the radiating portion of the vertical control surface and defining with said rectangular waveguide a streamlined projection; waveguide means within the radiating portion of the vertical control surface and coupled to said waveguide antenna for supplying energy thereto; and a coupling member mounted within said band of dielectric material, said coupling member including a central cylindrical shell of dielectric material, a pair of horn members, one mounted on each end of said central shell coaxial therewith and pointing away from said shell, and a tubular dielectric waveguide mounted within and coaxial with said shell, and including a pointed tip portion at each end thereof, each of said tip portions being in registry with the narrow portion of a different one of the horn members coupled to said cylindrical shell, one of said horn members being an input member and adapted to be responsive to energy to be applied to said rectangular waveguide member, the other of said horn members being an output member and coupled to the waveguide means for supplying energy to said rectangular waveguide antenna.

2. A dual antenna structure for an aircraft having a vertical control surface and comprising: a dielectric isolating section isolating the upper portion of said vertical control surface electrically from the remainder of the aircraft, said upper portion thereby providing a radiating surface for radiating energy in a first predetermined frequency band; a rectangular waveguide antenna, mounted in the top portion of said vertical control surface upperportion, and including radiating slots in each side thereof parallel to the usual direction of flight of the aircraft for radiating energy in a second predetermined frequency band, the pattern of radiation provided by said rectangular waveguide antenna being substantially omnidirectional in the horizontal plane and relatively narrow in the vertical plane; streamlining sections mounted in said vertical control surface upper portion adjacent said rectangular waveguide antenna, said two streamlining sections being fore and aft, respectively, of said rectangular waveguide antenna with respect to the usual direction of movement of said aircraft; a dielectric coupling member mounted within the dielectric isolating section in the vertical control surface and including a central cylindrical dielectric waveguide having pointed end portions, a dielectric cover member encompassing said central cylindrical waveguide and coaxial therewith, and a pair of terminating metal transition members, each encircling the point at a different end of said central cylindrical dielectric waveguide and forming with the associated point a transition section for the transfer of energy; and conductive waveguide means within said vertical control surface upper portion and coupling said dielectric coupling member to said rectangular waveguide antenna.

3. A dual antenna structure comprising: a conductive structure having a substantially planar surface; a dielectric isolating section within said conductive structure at an intermediate point and isolating a terminal portion of said conductive structure electrically from the remainder first antenna and coupling said dielectric waveguide to said second antenna.

References Cited in the file of this patent UNITED STATES PATENTS Southworth Aug. 6, 1946 Babcock et a1. May 19, 1953 cal Feb. 1, 1955 Kandoian et a1. Dec. 6, 1955

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