Antenna with a hemispheric radiation pattern and heatproof radiating elements.

p0001The present invention relates to an antenna with quasi-hemispherical diagram and radiating portion supporting the heat.

p0002an antenna on aircraft and gear used animated with great speed, subject to significant temperature increases, for communications of any kind between the aircraft and in particular the ground or satellites and for their navigation their control, their pursuit, for example.

p0003The antenna of the invention can transmit and receive on a center frequency in a wide range of a few hundred MHz to several GHz, but with a relatively wide bandwidth, of the order of 10 to 15% of this frequency Central.

p0004The antenna of the invention is especially able to withstand temperatures exceeding 1000 ° C.

p0005is already known an antenna consisting of a waveguide, of which one end forms the radiating part and is flush with the outer surface of the carrier aircraft, the antenna excitation portion being connected to the other end of the guide wave and inwardly away from the surface of the aircraft subject to the temperature rise. Even in case of wear of the radiating end, due to the heating, the waveguide structure remains. To put part of excitement to the guide bottom, away from heat, the waveguide is filled with a refractory dielectric material This refractory material, however, increases the weight of the antenna. In addition, the radiation pattern of such antenna is not hemispherical.

p0006For the record, here also mention the possibility of placing the antenna in the thermal protection of a thick layer of dielectric but that deforms the radiation pattern too.

p0007especially we know the antenna "sword", which derives from folded whip antenna, with one end fixed to a ground plane, which is orthogonal to the plane of the antenna, and a remote excitation point beyond the end to the ground - this is called a shunt power -.

p0008For the purposes specified above, the blade antenna, however, is not entirely appropriate. The edge of the antenna parallel to the ground plane is too far from it and would therefore be exposed to excessive temperature rise and if crushing the antenna on the ground plane, closer to the edge of the ground plane , bandwidth, which normally is satisfactory will deteriorate.

p0009From the blade antenna, the applicant has therefore sought to define an antenna capable of meeting the above requirements and thus it offers its invention.

p0010The present invention relates to a quasi-hemispherical diagram antenna, to radiating part attached directly to a ground plane and capable hearth under severe temperature conditions and excitation portion, electrically connected to the radiating part, remote from celle- above, characterized in that the radiating portion includes at least one solid monopolar element comprising a foot of large width and small height fixed to the earth plane and extended by a wide radiating wing extending parallel to the ground plane near this one.

p0011Thanks to the collapsed configuration of the monopole antenna of the invention, it can easily be embedded in the body or a protective coating thereof, so that its radiating wing is recessed from its outer surface or flush and not be so too subjected to temperature rises. With the extent of the radiating wing and its massive, the antenna of the invention has good bandwidth, in any case much better than a too narrow blade antenna.

p0012Note that the plaintiff, to move the antenna to antenna sword of his invention, does not confine itself to expand the first but has also demonstrated inventiveness.

p0013Indeed, he was known by the article "Zncreasing the beamwidth of a microstrip radiating element, Sanford Klein, pages 126-129, in International Symposium Digest, June 18-22, 1979 IEEE Antennas and Propagation Society 79 CHl 456-3AP University of Washington, Seattle, Washington, "an antenna consisting of a copper layer printed on one side of a substrate, and a ground plane deposited on the other side of the substrate. Now, such printed circuit antenna, in addition to having poor resistance to heat, which can take off the substrate layer of copper, and although it has a glowing extended wing, has a mediocre bandwidth This article not only therefore could not provide a useful teaching but could even a priori deter the plaintiff to go in the direction of his invention.

p0014In a preferred embodiment of the antenna of the invention, it comprises a group of four identical solid unipolar elements arranged in square and associates in two orthogonal pairs along the diagonals of the square, each of two opposing elements which can be placed symmetrically to the center square and out of phase each other and out of phase compared to 900 shower deu) other items.

p0015With this arrangement of the antenna elements with spatial and temporal quadrature, the field radiated by the antenna of the invention has a circular polarization.

p0016Advantageously, the antenna elements are disposed within a housing closed by a radome flush with the outer surface of thermal shield plates of an aircraft fuselage.

p0017In this case, the bottom of the housing may constitute the antenna ground plane, the monopole elements and the housing can be made in one piece and even the housing, the monopolar elements and a heat shield plate can be made as a single piece.

p0018The invention will be better understood using the following description of several embodiments of the antenna of the invention with reference to the accompanying drawings, in which<ul><li>- Figure 1 shows a sectional view of a first embodiment of the inventive antenna;</li><li>- Figure 2 shows a sectional view of a second embodiment of the inventive antenna;</li><li>- Figure 3 shows a sectional view of a third embodiment of the antenna of the invention; </li><li>- Figure 4 shows a sectional view of a fourth embodiment of the antenna of the invention.</li></ul>

p0019Referring to Figure 1, the antenna of the invention is mounted on the fuselage 1 of an aircraft, covered with thermal protection plates 2 fixed to the fuselage 1 by spacers 3.

p0020The antenna comprises a radiating portion 4, an energizing portion 5 and a set of coaxial feed 6.

p0021The radiating part 4 is accommodated in a conductive housing 1, attached to the fuselage by means of spacers 8 and slid between the shielding plates 2 with, here, the interposition of an annular seal 11.

p0022The antenna receiver housing has a flat bottom 9 and a cylindrical wall 10. Near the free edge of the wall 10, extends internally to it, an annular shoulder 12 for receiving a first end 13 of radome protection of the radiating portion 4 of the antenna and closing the housing 7. the wall of the thermal protection plates 2, adjacent to the housing 7 is formed, close the housing 7, to present a portion of annular recess 14 for receiving a second radome protection 15, flush with the outer surface of the plates 2.

p0023The radiating portion 4 of the antenna has, in this case, four elements identical monopolar massive - we see in Figure 1 that the elements 16 ', 16 ‴ - each consisting of a 17 foot, very wide and low height, here perpendicular to the bottom 9 of the housing and extended by a planar radiating wing 18 extending parallel to the bottom 9 of the housing recessed relative to the outer protective radome 15. the wings 18 have a rectangular radiating surface (square ) and the elements 16 are arranged in a square, with the feet 17 of the four elements respectively extending along the four sides of the square. The elements 16 are associated in pairs - 16 'and 16˝, one hand, and 16 ‴ and 16'^vOn the other hand, the elements 16˝ and 16 '^v not being visible in Figure 1 - to form two orthogonal pairs along the diagonals of the square, the two elements of each pair being opposed and positioned symmetrically to the center square.

p0024Figure 1 cutting plane intersects the radiating flanges of two adjacent elements 16 ', 16 ‴ of the respective two pairs.

p0025Each monopole element 16 is solid and is formed in one piece with the bottom 9 of the housing 7.

p0026The energizing portion 5 monopolar elements 16 remote from the radiating part 4 of the antenna. In the example, it is fixed under the fuselage 1 by fasteners 19.

p0027This excitation portion 5 is in fact constituted of a distribution member, the four radiating elements, power arriving through a connector 20 - it could also extend in the extension of this distributor device as shown 21 in dashed -, and phase distribution of these four elements. The phases of the supply, between the distributor and the radiating wings 18, on which are located the points of excitation of the monopole elements 24 is effected by the conductive cores 25 of the four coaxial cables 6, the outer conductive sheath 26, outcropping the caseback which on the one hand, they are fixed, are taken to the ground. The bottom 9 of the housing 7 thus forms the ground plane of the monopole elements 16. On the other side, the sheaths 26 of the cables 6 pass through the body 1 via an insulating gasket 27 and are connected to répartite; ir 5 through here a sliding contact 28.

p0028The feeding of four monopolar elements 16, by the dispatcher 5 is here such that the two elements of each pair (16 ', 16˝; 16 ‴, 16'^v) Are in phase opposition (180 ° phase shift) and that each element is in phase quadrature (90 ° phase shift) with the one and the other of the two elements of the other pair. Thus, the field radiated by the antenna which has just been described, with four elements respectively in spatial and temporal quadrature, has a circular polarization.

p0029Coaxial cable 6 are filled with an insulating material of ceramic type resistant to high temperatures.

p0030The thermal protection plates are made of refractory material, for example composite, based on carbon protected against oxidation.

p0031The radiating monopole elements are, for example, metal or composite material, conductor and protected against oxidation.

p0032The antenna which has just been described is a quasi-hemispherical radiation pattern; its radiating portion 4 can hearth under severe temperature conditions, for example caused by high speeds or re-entry into the layers of the atmosphere; its bandwidth is satisfactory.

p0033The embodiments of Figures 2-4 of the antenna of the invention are identical to that just described, except mainly the receiving housing of the radiating portion.

p0034In the embodiment of Figure 2, the housing 37 has no radome landing shoulder. The protective plates 32 do not have either radome receiving recess. The single radome 35 liver cover for the housing 31, with an upper portion 31 that rests on the cylindrical wall 30 of the housing and extends the walls of adjacent plates 32, and a cylindrical skirt 34 which fits within the casing and is extended by an annular ring 33 that rests on the bottom 39 of the housing. In addition, in this embodiment of Figure 2, the radiating elements 36 are not formed in one piece with the housing but attached and fixed by welding on the bottom 39 thereof.

p0035In the embodiment of Figure 3, the shielding plates 42 adjacent to bostier 47 are again provided with an annular recess portion 44 for receiving an annular outer flange 41 extending the cylindrical wall 40 of the housing 47 and a radome sole 45, formed by a plate superimposed on the flange 41 and extending the walls of the plates 42. the housing 41 has no sharp.

p0036In the embodiment of Figure 4, the radiating elements 56, the housing 51 and adjacent shielding plates 52 are formed of a single piece of composite material. An annular recess 54 is formed in the plates 52, around the cylindrical wall 50 of the housing, for receiving a plate-radome 55 extending the walls of the protective plates.