FR2764123A1 - RIGID ANTENNA AND CORRESPONDING MANUFACTURING METHOD - Google Patents

Abstract

A rigid antenna intended to be mounted on an aircraft has an internal conductive assembly comprising a plurality of linear conductive elements (4a - 4d) interconnected by a plurality of conductive elements wound (5a - 5c) on insulating supports (6 - 8). An outer protective casing (3) made of a fiberglass composite material surrounds the internal conductive assembly to ensure tightness while allowing the passage of electro-magnetic radiation.

Description

RIGID ANTENNA AND CORRESPONDING MANUFACTURING METHOD

  The invention relates to a rigid antenna, more particularly intended to be mounted on an aircraft, in

  especially on a helicopter or on an airplane.

  The invention also relates to a method of

  manufacture of an antenna according to the invention.

  The invention is particularly useful for ensuring high frequency communications in the 2 MHz band. To this end, wired antennas have already been used consisting of a cable stretched between several points outside the hull of an airplane or helicopter: although the wired antennas are light, their considerable length complicates their installation, especially in the case of helicopters

reduced dimensions.

  To replace the wire antenna, it has been proposed to use tubular antennas constituted by a rigid conductive tube of a determined length, carried by equally rigid arms fixed to the hull of the aircraft. Document FR 2 680 282 describes a tubular antenna of this type, comprising a tube carried by masts, the tube consisting of an insulating tubular support on which is helically wound a conductive tape protected externally by an insulating coating after winding

on the tubular support.

  This known antenna is generally satisfactory, but has insufficient radiation in the high frequency range located below 6 MHz. In addition, the antenna adjustment device constituted by an adapter with capacitive coupling adjustable by ring adjustable in position does not make it possible to carry out a capacitive adaptation usable on the entire band of

  frequency between 2 and 30 MHz.

  The invention aims to remedy the drawbacks of the known technique by providing a new rigid antenna ensuring communications on all the bands useful for aviation in the range between 2 and 30 MHz, having a reduced length allowing easy installation on all types of aircraft. The subject of the invention is a rigid antenna, intended to be mounted on an aircraft, comprising an internal conductive assembly comprising a plurality of linear conductive elements connected together by a plurality of conductive elements wound on insulating supports, and comprising, in addition, an external protective envelope made essentially of material substantially transparent to electromagnetic radiation,

  preferably of electrically insulating material.

  According to other characteristics of the invention: - each linear conductive element is made of light metal or a light metal alloy, at least partially coated with a small thickness of material having good electrical conductivity and thermal; - at least one coiled conductive element comprises two coils, the first of which comprises a first large number of contiguous turns and the second of which, wound in opposite direction to the first, comprises a second lower number of non-contiguous turns, of conductive wire or cable externally isolated; - at least one coiled conductive element includes a predetermined number of non-contiguous turns, wire or

  externally insulated conductor cable.

  - according to a first alternative embodiment of the invention, the antenna has a linear structure

substantially cylindrical.

  - according to a second alternative embodiment of the invention, the antenna has a folded structure

  contained in a profiled envelope.

  Preferably, the outer protective envelope

  is made of fiberglass composite material.

  In the first alternative embodiment, the outer protective casing is closed at both ends by ends made of light metal or of alloy

  light metal externally insulated.

  In the second embodiment of the invention, the outer protective envelope is provided

  connecting flanges to the hull of an aircraft.

  Advantageously, in the two alternative embodiments, each linear conductive element is centered in each insulating support by at least one ring in

electrically insulating material.

  The invention also relates to a method of manufacturing a rigid antenna comprising the following steps: a) mounting at least one timing ring on linear conductive elements; b) assemble each setting ring to an insulating support; c) winding at least one conductive element on at least one insulating support; d) ensuring the electrical connection of the linear and wound conductive elements according to a conductive assembly; e) coating said conductive assembly with an external protective envelope made essentially of material substantially transparent to electromagnetic radiation. The invention will be better understood thanks to the

  description which follows, given by way of example not

  limiting with reference to the accompanying drawings in which: - Figure i shows a sectional view with partial cutaway of a first variant of

realization of the invention.

  - Figure 2 shows a sectional view with partial cutaway of a second variant of

realization of the invention.

  Referring to Figure 1, a rigid antenna according to the invention has a linear structure

substantially cylindrical.

  The antenna is mounted on an aircraft in a known manner according to document FR 2 680 282 by locking on a conductive arch of a mast head with

quick opening.

  For this purpose, the antenna according to the invention comprises two conductive rings 1, 2. The conductive ring 1 is located on the high frequency side, while the ring

  conductor 2 is located on the ground side.

  In the space between the conductive rings 1, 2, extends an outer protective casing 3 made of material transparent to electromagnetic radiation, preferably of composite material

fiberglass.

  The envelope 3 contains an internal conductive assembly comprising a plurality of linear conductive elements 4a, 4b, 4c, 4d connected together by a plurality of wound conductive elements 5a, 5b, 5c, on supports

insulators 6, 7, 8.

  Each linear conductive element 4a to 4d is made of light metal or a light metal alloy, preferably from a thin tube having a diameter of the order of a centimeter. The sections of metal tube are connected together by the insulating supports 6, 7, 8 and are centered inside these insulating supports by rings 9a to 9j of electrically insulating material, preferably of composite material

fiberglass.

  To ensure good electrical continuity and good thermal distribution, each linear conductive element 4a to 4d is coated at least partially with a small thickness of material having good electrical and thermal conductivity. Advantageously, for this purpose, the outer half-perimeter of each linear conducting element is covered with an adhesive film 10 of thickness less than one millimeter of a flexible strip of

copper with beryllium.

  This coating can also be carried out by

  shooping or any other coating method.

  On the first insulating support 6, a first large number of contiguous turns of externally enamelled copper wire are wound in order to produce a first coil; then a second lower number of non-contiguous turns of externally insulated conductor cable is wound in the opposite direction. Preferably, the diameter of the fine enameled copper wire is less than 1 mm, while

  that the section of the conductor cable is greater than 2 mm2.

  After the two coils have been produced on the first insulating support 6, the electrical connection is made between the coils mounted in parallel and the linear conductive element by coating a small thickness of conductive material: for this purpose, the adhesive tape is advantageously used. beryllium copper aforementioned to achieve electrical continuity in lia and llb by completely surrounding the insulating support 6. Preferably, each insulating support 6 to 8 is produced by cutting glass fiber composite tube whose ends are surrounded by a conductive coating to ensure the electrical connection of all the elements of the

conductor mounting.

  On the second section 7 of fiberglass composite tube, a coiled conductive element is produced which is substantially identical to that produced on section 6, by a first winding of contiguous turns of enamelled conductive wire followed by a second winding of non-contiguous turns of externally insulated conductor cables. In each case, each wound conductive element 5a or 5b thus produced comprises two coaxial coils coupled in parallel and wound in opposite directions to each other. The large number of contiguous turns of enamelled copper wire is preferably between 80 and 150 turns, while the lower number of non-contiguous turns of externally insulated conductor is preferably between 5 and 50 turns. The winding diameter is preferably greater than 2 cm and corresponds substantially to the outside diameter of the insulating support 6 or

7.

  The timing rings 9a to 9j made of fiberglass composite are fixed to the linear conductive tube 4a to 4d by means of a metal screw embedded in a bore and screwed into a thread made in the linear conductive tube 4a to 4d. The assembly of the wedging or centering rings 9a to 9d to the corresponding insulating supports 6 to 8 is carried out by bonding using an adhesive of the Araldite type (trademark registered by the company under Swiss law

CIBA).

  The third wound conductor element 5c is produced by winding on the insulating support 8 a number of non-contiguous turns of a conductor externally insulated according to a predetermined number between

and 120 turns.

  After assembly step by step, and establishment of the electrical connection of all the elements 1, 4a, 5a, 4b, 5b, 4c, 5c, 4d and 2 in this order to form a conductive assembly connecting the conductive rings 1 and 2, we sets up the outer protective casing 3 preferably made of material

  fiberglass composite, either by assembling half

  shells glued to each other by means of aforesaid adhesive or by successive assembly of tubular elements on a mandrel and fitting of the conductive ring. The second end piece 13 is shaped as a tightening nut to be screwed onto a threaded rod 12 trapped in the end of the tube 4d and secured to this end by means of two screws 14, 15. After tightening and bonding of the assembly,

  sealing is achieved by bonding the first endpiece 16.

  The two end caps (13 and 16) are advantageously made of light metal or of a light metal alloy isolated externally, by anodization or

  by applying an insulating coating.

  The antenna thus produced has a substantially cylindrical linear structure with a diameter less than

5 cm.

  Referring to Figure 2, a rigid antenna according to the invention has a folded structure contained

in a profiled envelope.

  The reference numbers identical to the figures in FIG. 1 designate identical elements or

  functionally equivalent to the elements in Figure 1.

  On the high frequency side, the antenna is connected to the device by an externally insulated antenna cable passing through a conduit made in the envelope

  outer 3 in fiberglass composite material.

  The outer protective envelope is provided with flanges 20 and 21 for connection and mounting on the hull of an aircraft. These connection flanges 20 and 21 can be externally insulated or conductive so as to provide electrical continuity with the hull of the aircraft. The linear conductive elements 4a to 4c produced by sections of light metal alloy tube are connected to sections 6, 7, 8a and 8b in composite glass fiber forming an insulating support for the wound conductive elements 5a to 5d similar to the wound conductive elements 5a to 5c described with reference to the

figure 1.

  The assembly of the linear conductive tubes to the insulating support tubes is carried out in a similar manner by means of wedging rings 9 or by other equivalent mechanical means (screwing, gluing, press mounting). The electrical connection can be made by soldering, shooping type coating, by means of lugs or equivalent assembly. In FIG. 1, the wound conductive element 5c situated on the mass side comprised a single coil with a predetermined number of non-contiguous turns comprised between and 120 turns, while, in FIG. 2, the last two wound conductive elements 5c and 5d located on the mass side are substantially identical and each comprise a predetermined number of non-contiguous turns of externally insulated conductive wire between 5 and 60 turns and are connected together by a length 22 of wire

  or externally insulated conductor cable less than 1 m.

  In both cases, the rigid antenna according to the invention is preferably manufactured using a method comprising the following steps: a) mounting at least one wedging ring on a linear conductive tube; b) assemble each setting ring to an insulating support; c) winding at least one conductive element on at least one insulating support to produce at least one coiled conductive element; d) ensuring the electrical connection of the linear and wound conductive elements according to a conductive assembly; e) coating said conductive assembly with an external protective envelope made essentially of

fiberglass composite material.

  In the first embodiment, the outer protective casing 3 extends between the conductive rings 1 and 2, while in the second embodiment of the invention, the outer protective casing 3 extends between the two flanges

  connection 20 and 21 to the hull of the aircraft.

  The assembly of the outer casing around the conductive assembly thus produced is carried out by making a waterproof sheath. It can be done by molding, injection, compression, pultrusion, or by other

equivalent techniques.

  As can be seen, in both cases, the end caps 13 and 16 or the external protrusions 23, 24 of the casing 3 can be aerodynamically profiled, so as not to significantly increase the drag of the aircraft carrying the rigid antenna according to the invention. The invention described with reference to two particular embodiments, is in no way limited thereto, but on the contrary covers any modification of structure and any variant embodiment within the scope and spirit of the invention.

Claims (11)

  1. Rigid antenna, intended to be mounted on an aircraft, comprising an internal conductive assembly comprising a plurality of linear conductive elements (4a - 4d, 22) connected together by a plurality of wound conductive elements (5a - 5d) on insulating supports (6 - 8, 8a, 8b), and further comprising an outer protective casing (3) made essentially of material substantially transparent to electromagnetic radiation,   preferably of electrically insulating material.   2. Antenna according to claim 1, characterized in that each linear conductive element (4a - 4d) is made of light metal or of light metal alloy, coated at least partially with a small thickness of material having good electrical and thermal conductivity . 3. Antenna according to claim 1 or claim 2, characterized in that at least one coiled conductive element (5a, 5b) comprises two coils, the first of which comprises a first large number of contiguous turns and the second of which, coiled in opposite direction to the first, has a second lower number of non-contiguous turns of externally insulated conductive wire or cable. 4. Antenna according to claim 1 or claim 2, characterized in that at least one coiled conductive element (5c, 5d) comprises a predetermined number of non-contiguous turns of externally insulated conductive wire or cable. 5. Antenna according to any one of   Claims 1 to 4, characterized in that the antenna   has a substantially cylindrical linear structure (figure 1).   6. Antenna according to any one of   Claims 1 to 4, characterized in that the antenna   has a folded structure contained in an envelope profiled (Figure 2).   7. Antenna according to any one of   previous claims, characterized in that   the outer protective casing (3) is made of fiberglass composite material.   8. Antenna according to any one of   previous claims, characterized in that   the outer protective casing (3) is closed at two ends by end caps (13, 16) made of light metal or   light metal alloy externally insulated.   9. Antenna according to any one of   Claims i to 7, characterized in that the envelope   (3) external protection is provided with flanges (20, 21)   connection to the hull of an aircraft.   10. Antenna according to any one of   Claims 1 to 9, characterized in that each element   linear conductor (5a - 5d) is centered in each insulating support by at least one ring (9, 9a - 9j) in electrically insulating material.   11. A method of manufacturing a rigid antenna comprising the following steps: a) mounting at least one ring (9) of wedging on elements (5a - 5d) linear conductors; b) assembling each setting ring (9) to an insulating support (6 - 8, 8a, 8b); c) winding at least one conductive element on at least one insulating support (6 - 8, 8a, 8b), to produce at least one wound conductive element (5a - 5d); d) ensuring the electrical connection of the linear conductive elements (4a - 4d) and wound in a conductive arrangement; e) coating said conductive assembly with an outer protective casing (3) essentially of material   substantially transparent to electromagnetic radiation.