WO1996018219A1

WO1996018219A1 - Low weight antenna element

Info

Publication number: WO1996018219A1
Application number: PCT/SE1995/001464
Authority: WO
Inventors: Göran JAKOBSSON; Bo Sundvall
Original assignee: Saab Ericsson Space Ab
Priority date: 1994-12-07
Filing date: 1995-12-06
Publication date: 1996-06-13
Also published as: SE9404238L; SE9404238D0

Abstract

An antenna element is described. It is intended to be incorporated in a group antenna for satellite and comprises a ground plane (1) and at least one radiation disc (4, 6), connected to means for supplying desired electromagnetic radiation, preferably within the microwave range. An essentially centrally located upright (5, 7) is arranged to retain said radiation disc at a distance from the ground plane (12). The antenna element is in particular characterized in that the upright is made of a dielectric material having a low loss factor tan δ.

Description

Low weight antenna element

The present invention relates to an antenna element, in particular incorporated in a group antenna for satellite, comprising a ground plane and at least a radiation disc, connected to means for supplying desired electromagnetic radiation, preferably within the microwave range, an essentially centrally located upright being arranged to retain said radiation disc at a distance from the ground plane.

This antenna element is intended for mobile satellite communication, preferably with a common antenna for transmission and reception and is normally arranged for a simple or twofold polarization. The requirements of such an antenna element is that it must have a low weight and good electric characteristics, i.e. it must have low losses and generate low intermodulation products. Antenna elements of the kind mentioned in the beginning are known since long having a multitude of different designs. Usually they have been constructed having two radiation discs and an upright integrated in one metal piece. Such antenna elements are relatively heavy and have electric losses.

Thus, the object of the present invention is to achieve an antenna element of the kind mentioned in the beginning that is very light and has good electric characteristics.

According to the invention such an antenna element is characterized in that the upright is made of a dielectric material having a low loss factor tan δ. The radiation disc and the reflector disc should be made of electrically linear materials, such as pure aluminium, copper or silver, but not of materials that can generate mixing products, i.e. intermodulation products, of several different signals. Such materials can be alloys, ferromagnetic materials, etc. It is also critical that no connections metal-to-metal exist.

In a preferred embodiment the upright is made in the shape of a thin-walled pipe, suitably of a polymer such as epoxide resin, cyanate ester, preferably reinforced with fibers, for example of silica. The material of the upright should have a loss factor tan δ < 0.005.

The radiation disc can be designed as a ring, attached to the exterior side of the upright, which in this case can have only one diameter. Alternatively, the upright can made in sections having decreasing diameters as seen axially from the ground plane, so that at least one step is formed for supporting an annular radiation disc.

In the case where the radiation disc is constituted of a circular washer, the upright is made of at least two pipe sockets between which the radiation disc is secured.

The invention will be described in greater detail in the following with reference to the accompanying schematic drawings in which

Figure 1 shows, in a perspective view, an embodiment of an antenna element according to the invention,

Figure 2 shows the same object, in an elevational view of a vertical, central section,

Figure 3 shows, in a perspective view, part of an antenna element according to the invention,

Figure 4 shows an elevational view of a vertical, central section in a second embodiment of the antenna element of Figure 3, and

Figure 5 shows a corresponding view of a third embodiment of the antenna element of

Figure 3.

In Figures 1 and 2 the reference number 1 denotes a ground plane, here in the form of a cup having a cylindrical wall 2. A first pipe socket 3 is adhesively attached centrally to the ground plane 1 , the socket being part of a thin-walled upright which is made of a polymer such as epoxide resin or cyanate ester, reinforced with silica fibers. Then a first radiation disc 4 having the shape of a circular washer is adhesively bonded on top of said pipe socket 3, the disc being of an electrically linear metal such as pure aluminium. A second pipe socket 5 then follows, also adhesively attached and being part of the upright, supporting a second, adhesively bonded radiation disc 6 having a configuration similar to that of the first radiation disc, followed by a third pipe socket 7, also adhesively attached, on top of the second radiation disc 6. A reflector disc 8 is adhesively attached to the topmost portion of the third pipe socket 7. The supply points for signals incoming to the first radiation disc are referenced 9 and 10. In Figure 2, showing the supply point 9 in a sectional view, it is seen that it is made having no metal contact between a connection pin 11 and the radiation disc 4. The signal is in this case coupled capacitively, through a pipe 12 integral with the radiation disc 4, according to prior art. A dielectric sleeve 11a works as a guide for the connection pin 11. Alternatively, the connection pin can be located on the under side of the ground plane 1 and be electromagnetically coupled, through a slot therein, directly to a first radiation disc. Actually, the number of supply points for signals incoming to the first radiation disc can be one, two, three or four.

A second embodiment of an antenna element according to the invention is illustrated in Figures 3 and 4. Here the upright is constituted of a thin- walled pipe 13 of a polymer as in Figures 1 and 2. Annular first and second radiation discs 14 and 15 are attached adhesively to the thin-walled pipe 13 by means of adhesive 16, 17. A third embodiment is illustrated in Figure 5. Here the upright is formed of three cylindric sections 18, 19, 20 having decreasing diameters as seen from the bottom, so that support steps are formed for the first and second radiation discs 21 and 22.

Claims

1. An antenna element, in particular incorporated in a group antenna for satellite, comprising a ground plane (1) and at least one radiation disc (4, 6) connected to means (9, 10) for supplying desired electromagnetic radiation, preferably within the microwave range, an essentially centrally located upright (3, 5, 7) being arranged to retain said radiation disc at a distance from the ground plane, characterized in that the upright is made of a dielectric material having a low loss factor tan δ.

2. An antenna element according to claim 1, characterized in that the upright is made as a thin-walled pipe.

3. An antenna element according to claim 1 or 2, characterized in that the upright is made of a polymer, such as epoxide resin, cyanate ester, preferably reinforced with fibers, for example of silica.

4. An antenna element according to any of claims 1 to 3, characterized in that the upright is made of a material having a loss factor tan δ < 0.005.

5. An antenna element according to any of the preceding claims, characterized in that the radiation disc has the shape of a ring (14, 15), attached to the exterior side of the upright (13).

6. An antenna element according to claim 5, characterized in that the upright is made in sections (18, 19, 20) having decreasing diameters as seen axially from the ground plane (1) so that at least one step is formed for supporting a radiation disc (21 , 22).

7. An antenna element according to any of claims 1 to 4, characterized in that the radiation disc has the shape of a circular washer (4, 6) and the upright is made of at least two pipe sockets (3, 5, 7) between which the radiation disc (6) is attached.

8. An antenna element according to any of claims 1 to 7, characterized by a reflector disc (8) attached to the upright (3, 5, 7) above at least one radiation disc (4, 6).