EP0493237A1 - Rotary curtain antenna with dipoles - Google Patents

Abstract

The antenna is a rotary dipole antenna comprising a base (M1), a rigid armature (M, P1-P8, B1-B4) rotatably mounted on the base, a plurality of wire dipoles (D1-D8) fixed on the armature and means (C1-C4) for supplying each dipole with electrical energy from a first end thereof. In order to ensure good fixing of the dipoles, the rigid reinforcement extends opposite at least the first end of each dipole and this first end is fixed directly to the rigid reinforcement, while the second ends of the dipoles are either fixed directly on the rigid frame or connected to it by a catenary (K1, K2, K7) resting on the frame. Application to the design of power antennas in the HF range. <IMAGE>

Description

The invention relates to a rotary dipole antenna comprising a rigid armature rotatably mounted on a base, a plurality of wire dipoles fixed on the armature in a determined position, each dipole comprising two ends, and means for supplying each dipole with energy. electric from a first end of it. In all that follows, and in the claims, the terms “first end of the dipole” designate the supply point of the dipole, that is to say the place where the junction is made with the two-wire line which connects it. feeds.

It is an antenna intended to radiate a large power, for example 500 kW, in the HF range (3 to 30 MHz).

An antenna of this type is already known, in which the rigid armature essentially extends outside of an area in which the wire dipoles are arranged, these being interconnected so as to form a curtain, this the latter being fixed by its ends to the rigid reinforcement by means of catenaries.

Although satisfactory, such an antenna has several drawbacks. Due to the peripheral arrangement of the rigid armature, it extends substantially beyond the curtain of dipoles, which gives the antenna a large footprint, greater than that imposed by its electrical operation. Furthermore, the curtain of dipoles being held only by its edges, it deforms significantly under the effect of the wind until it comes into contact with the rigid reinforcement. Finally, access by maintenance personnel to different points of the antenna is delicate since the dipole curtain cannot be used as a support for this purpose.

The problem which the invention aims to solve is to propose an antenna of the kind mentioned at the beginning of the presentation, does not have the above drawbacks, while limiting as much as possible the complexity of the rigid reinforcement, and therefore the cost of the antenna as a whole.

This problem is solved according to the invention by the fact that the rigid reinforcement extends opposite at least said first end of each dipole by which it is supplied with electrical energy and in that this end is fixed directly to the rigid frame, the second ends of the dipoles not fixed directly on the rigid frame being connected to the latter by a catenary bearing on the frame.

Thus, according to the invention, the rigid armature is arranged to support each wire dipole in the most stressed place both mechanically and electrically, that is to say at the first end above, while its second end may be maintained more briefly, by means of a catenary.

• la figure 1 est une demi-vue en perspective d'une première face d'une antenne rotative selon l'invention ;
• la figure 2 est une demi-vue montrant une deuxième face de l'antenne ; et
• la figure 3 est une vue de côté partielle de l'antenne.

Other details and advantages of the invention will appear during the following description of a nonlimiting embodiment, with reference to the appended drawings in which:

• Figure 1 is a half perspective view of a first face of a rotary antenna according to the invention;
• Figure 2 is a half view showing a second face of the antenna; and
• Figure 3 is a partial side view of the antenna.

The rotary antenna shown in the figures is a double antenna comprising two arrays of dipoles and a set of switches for connecting one or the other of the two arrays to a device for feeding the antenna. Depending on the network connected, the antenna is a low range antenna Ab 4/4 / 0.5 - 6/7/9/11 MHz or a high range antenna Ah 4/4/1 - 13/15/17/21 / 26 MHz; it is recalled that, according to the international electrical definition of antennas, for example the designation 4/4 / 0.5 - 6/7/9/11 MHz corresponds to an antenna intended to operate in the bands of 6, 7, 9 and 11 MHz (which gives approximately a half wavelength of 18 m at the central operating frequency of 8.47 MHz) and having 4 groups of 4 superimposed dipoles, the difference between two groups being equal to the half wavelength at the center frequency and the lowest group being at a distance from the ground equal to 0.5 times this wavelength. The antenna power is 500 kW.

The antenna comprises a vertical metal central mast M having a base M1 made of reinforced concrete, intended to rest on the ground. The base M1 comprises a circular sole M2 of great thickness on which is arranged a tubular enclosure M3. The sole M2 is partially buried in the soil S.

The M3 tubular enclosure houses the auxiliary circuits of the antennas. It is accessible to personnel by an M5 door.

The central mast M rests on the tubular enclosure M3 by means of a gear ring M6 and a drive mechanism not shown makes it possible to rotate it around a longitudinal axis of the latter.

The low range antenna Ab comprises four pairs of horizontal metal beams P1 to P8 arranged in a median longitudinal plane of the central mast M. This antenna being symmetrical with respect to a plane perpendicular to said median longitudinal plane, the description relating to half of antenna shown in Figure 1 applies to the other half not shown. The beams of each pair such as P1, P2 are disposed respectively on either side of the mast M and are fixed by one end to the latter by means of an articulation X so as to be able to pivot in said median longitudinal plane. The beams P1, P2, P7, P8 of two pairs of upper and lower beams respectively extend over approximately half the width of the antenna - that is to say a little more than one wavelength at the central working frequency dipoles carried by these beams - while the beams P3 to P6 pairs of intermediate beams, located between the previous ones, extend over about a quarter of the width of the antenna, just over half a wavelength.

The upper beams P1, P2 are kept horizontal by means of an inclined stay H1 and fixed between an upper end of the central mast M and a region of the beams distant from their free end. The intermediate beams P3, P4 are supported by a vertical shroud H2 fixed between a middle region of the upper beams P1, P2 and a free end of the intermediate beams P3, P4. The intermediate beams P5, P6 located directly above the previous ones are supported by a vertical stay H3 connecting the free ends of the beams P3, P5 and P4, P6 respectively. The lower beams P7, P8 are supported by a vertical stay H4 fixed between the corresponding upper beam P1, P2 - at the point of attachment of the inclined stay H1 - and a corresponding point of the lower beams P7, P8.

The beams P1, P2, P7, P8 of the upper and lower pairs of beams each carry two transverse arms B1, B2 respectively disposed in a median region of the beam and at a free end thereof, and having a length substantially equal to the quarter of the wavelength, at the central working frequency. In addition, another transverse arm B3 of neighboring length is fixed on the central mast M, between the beams of each of these pairs of beams.

Each beam P3 to P6 of the pairs of intermediate beams carries a single transverse arm B4 disposed in the vicinity of a free end of this beam and of length identical to those carried by the pairs of upper and lower beams.

At a free end of each transverse arm B1 to B4 is arranged a rod T extending upwards, parallel to the central mast M, over a short length relative to the length of the transverse arm. The rod T of the transverse arm B2 carried by the free end of each upper beam P1, P2 is equipped, at a free end, with a pulley O with an axis parallel to the transverse arm while the corresponding rod of each lower beam P7, P8 is equipped, at a free end, with two pulleys O juxtaposed, arranged on either side of the rod T and axis parallel to the transverse arm B2. The free end of each lower beam P7, P8 also carries a pulley O with an axis parallel to the previous ones.

Each upper beam P1, P2 also carries a rod T1 of short length at its free end and a rod T2 whose length is of the order of magnitude of a quarter of the wavelength, at the central operating frequency, this rod being distant from the end of the beam; the two rods T1, T2 are directed upwards. Each lower beam P7, P8 carries two similar rods T1, T2 directed downwards.

The mast M, the beams P1-P8, the transverse arms B1-B4 and the rods T1, T2 each consist of a metal tube.

Between the transverse arms B1-B3 situated opposite the upper beam P1 are mounted two wire dipoles D1, D2 constituted in a manner known per se by a cylindrical cage of six parallel conductive wires which are distant from each other. One of them D2 is fixed between the two free ends of the rods T carried by the transverse arms B1, B3, and the other is fixed between the transverse arm B1 and to a catenary K1 bearing on the pulley O carried by the arm B2 and that carried by the arm B2 of the lower beam P7; a weight L1 is fixed to a free end of the catenary K1 and ensures the tensioning of the catenary and the dipole D1.

Two wire dipoles D7, D8 are similarly mounted opposite the lower beam P7, the dipole D7 being tensioned by means of a catenary K2, bearing on the other pulley O carried by the transverse arm B2 of this beam, and of a weight L2.

Opposite the two pairs of intermediate beams P3, P4 and P5, P6 are arranged two pairs of dipoles wired D4, D4 and D6, D6, the dipoles of each pair being interconnected by one end and fixed at their other end to the end of the rods T carried by the two transverse arms B4, B4 arranged on either side of the mast central M. The tensioning of these dipoles is ensured indirectly by the catenary K1, knowing that the transverse arms are likely to deform somewhat. Furthermore, on each half of the antenna, a wire dipole D3, D5 is fixed between the end of said rods T and the catenary K1 laterally skirting the antenna.

A catenary K7 is suspended from the free end of the upper transverse arm B3: to this catenary are fixed the ends of the dipoles D4 and D6 distant from the transverse arms B4.

Each of the dipoles D1 to D8 has a slightly reduced length compared to the wavelength at the central operating frequency λ, namely 0.8λ, that is to say still about 14 m.

The dipoles are supplied in pairs by means of a two-wire supply line. Thus the four pairs of dipoles D1-D2, D3, D4, D5, D6 and D7, D8 located on the half antenna of Figure 1 are supplied by four supply lines C shown schematically in this figure and whose the fixing means will be specified later on in the description of FIGS. 2 and 3.

Each supply line C starts from the end of the transverse arm B1-B4 supporting the pair of dipoles, goes along this arm then the corresponding beam P1, P3, P5, P7 until it reaches the central mast M and goes along it to reach the tubular enclosure M3. Power line portions extending vertically are tensioned by means of helical springs G1 arranged directly above them.

A reflector Rb extends over substantially the entire surface of the low range antenna Ab. It comprises two parts arranged on either side of the central mast M and consisting of a layer of horizontal conductive wires F spaced from each other by a distance of the order of 1 m. The wires F are fixed at one end to the central mast M by a conductive link, and at one end either on a catenary such as K3-K5, or for some on the rods T1 carried by the upper P1 and lower P7 beams . The catenaries K3, K5 extend between the end of the rods T1 and the central mast M, bearing on the rods T2 of greater length, carried by the upper and lower beams, while the catenary K4 extends between the free ends of these beams. The catenary K3, K5 are connected to the rods T1 by a helical tension spring G2. As for the catenary K4, it is fixed on the upper beam P1 by one end and carries a weight L3 at its other end, which rests on the pulley O of the lower beam P7.

Between its two ends, each wire F of the reflector Rb is fixed at several points at which it crosses either a rod such as T2, or a guy wire such as H1-H4, or again vertical conducting wires F1. The vertical wires F1 extending between the catenary K3 and the upper beam P1 on the one hand, and between the two upper beams P1 and lower P7 on the other hand are tensioned by a helical spring G2 fixed between their lower end and the neighboring beam.

It has been observed that the discontinuity created by the presence of the central mast M in the reflector Rb does not appreciably modify the behavior of the latter, at the frequencies concerned.

The dipole groups D1-D8 are fixed at the following four heights above the ground: 17.7 m; 35.4 m; 53.1 m; 70.9 m. As for the gear ring M6, it is located as close as possible below the reflector Rb, ie at a height slightly above 8 m. Finally, the central mast M rises to a height of about 80 m and barely protrudes above the reflector Rb, itself extending over a height equal to 0.25λ, at the central frequency of use , above the highest dipoles D1, D2.

The high range antenna Ah shown in FIGS. 2 and 3 is similar to the low range antenna Ab and the description relating to the latter is applicable to it, the corresponding elements being assigned with lowercase letters. Naturally, its dimensions are adapted to the central frequency at which it operates, so that its dipoles d1 to d8, of length equal to approximately 7 m, are arranged at the following four heights from the ground: 15.9 m; 23.9 m; 31.8 m; 39.8 m.

The high range Ah antenna is distinguished however by the fact that its reflector Rh is not located in a median longitudinal plane of the central mast M but is offset therefrom so that its wires f extend continuously from a catenary side k4 to the other. The beams p1 to p8, which are still located in the plane of the reflector Rh, are therefore not pivotally fixed on the central mast M directly, but on bars v transverse to both the reflector Rh and the central mast M and fixed rigidly on the latter. Similarly, the shrouds h1 are fixed to such a bar v. These transverse bars v are all connected together by guy lines h5, each guy line being fixed between the free ends of two adjacent bars v with the interposition of a helical tension spring g3.

Furthermore, a rod t3 is fixed to the free end of the lowest crossbar v and extends vertically downwards so as to maintain the wires of the reflector Rh in this region.

Along and above each beam p1-p8 of the high range antenna and each beam p1-p8 of the low range antenna is fixed a guardrail j1 (Figure 2) facilitating the access of maintenance personnel to the different antenna points. A guardrail j2 (Figure 3) is also fixed along each transverse arm b1-b4 or B1-B4.

The dipole supply lines include a horizontal line portion c1 (respectively C1 for the low range antenna) running along part of each guardrail j1 and each guardrail j2, to supply two adjacent dipoles such as d1, d2, a first portion of vertical line c2, C2 grouping the supply of two groups of two superimposed dipoles d1, d2 and d3, d4, a second portion of vertical line c3, C3 connecting two first portions c2, C2, and a third portion of vertical line disposed inside the central mast M and bringing together all of the feed wires of each antenna.

Each first portion of vertical line c2 is stretched between the guardrail j1 of a beam p1 located above and the beam p3 located below, the connection with the latter being effected by a helical tension spring g1 (FIG. 3) . Each second portion of vertical line c3 is fixed between two horizontal bars v1, v2, fixed in two regions of the central mast M distant from each other, always with the interposition of a helical tension spring g1.

Several advantages result from the structure described above. The presence of a metal frame extending over the width and the height of the antenna gives it great rigidity allowing it to withstand fairly large forces due to wind or frost; this frame is made up of all the beams P1 to P8 and the transverse arms B1-B4. The dipoles D1-D8 are, at numerous points, directly connected to this armature, which ensures that the latter are well maintained and in particular prevents them from coming into contact with the reflector Rb. Each reflector Rb, Rh also directly benefits from the rigidity of the armature since several of the elements allowing its maintenance (rods T1, T2; vertical wires F1; shrouds H1-H4) are fixed on this armature. The supply lines themselves C1-C4 are supported on this frame in their horizontal portions or are stretched between two points thereof in their vertical portions, whereas in the prior art they had to be maintained by specific catenaries great length joining the peripheral attachment points of the antenna.

This frame also allows easy access to different points of the antenna for maintenance, especially at the end of the transverse arms along which the supply lines extend.

It will also be noted that this armature does not extend substantially beyond the dimensions imposed by the electrical regime of the antenna, that is to say the dimensions of the low range reflector Rb. This is in particular due to the original way of tensioning the dipoles: while in the prior art the dipoles were stretched from points located very outside the antenna, they are stretched here from the pulleys O located in the surface of the reflector Rb, which reduces the value of the forces to be applied to the lateral catenary K1. This is also due to the fact that the main stiffening elements that are the beams P1-P8 are interposed at the very heart of the reflector, whereas according to the prior art, the stiffening elements were located outside the limits of the reflector.

In addition, the particular structure of the base M1 makes it possible to have a large part of the volume of reinforced concrete as high as possible so as to better maintain the central mast M and to reduce the volume of buried concrete, as well as to benefit from same time of a technical room, while according to the prior art most of the volume of concrete was located in the sole M2.

Claims (10)

1.- Rotary dipole antenna comprising: - a rigid frame (M, P1-P8, B1-B4) rotatably mounted on a base (M1); - a plurality of wire dipoles (D1-D8) fixed on the armature in a determined position, each dipole comprising two ends; and - means (C1-C4) for supplying each dipole with electrical energy from a first end thereof;
characterized in that the rigid reinforcement extends opposite at least said first end of each dipole (D1-D2) and in that this end is fixed directly to the rigid reinforcement, the second ends of the non-fixed dipoles directly on the rigid frame being connected to it by a catenary (K1, K2, K7) bearing on the frame. 2. Antenna according to claim 1, characterized in that the armature comprises a vertical mast (M), a plurality of pairs of horizontal beams (P1-P8) arranged in a plane parallel to the mast and fixed thereon, the beams (P1, P2; P3, P4) of each pair being arranged on either side of a median longitudinal plane of the mast (M), the dipbles (D1-D8) extending along and at a distance from the beams (P1-P8), each beam carrying, opposite each of said first ends of the dipoles, a horizontal arm (B1-B4) fixed transversely on the beam and supporting these ends, said catenary (K1, K2, K7) being supported on other horizontal arms fixed transversely on at least some beams (P1, P7) or on the mast (M), opposite some of said second ends of the dipoles. 3.- antenna according to claim 2, characterized in that it comprises several pairs of dipoles arranged end to end horizontally, each pair comprising two dipoles (D1, D2) arranged end to end and fed at their first common end, a point of connection between said pairs arranged end to end being fixed to one of the transverse arms (B3) or to a catenary (K7), the second ends of the dipoles (D1, D2, D5, D7) neighboring the lateral edges of the antenna being fixed on a catenary (K1, K2) bearing on a pulley (O) and carrying a weight (L1, L2) at a lower end. 4. Antenna according to claim 3, characterized in that it comprises at least three horizontal rows of superimposed dipoles, two pulleys (O) being disposed respectively opposite the two ends of two upper (D1, D2) and lower rows ( D7, D8) and being fixed on a transverse horizontal arm (B2) carried by a beam (P1, P7) situated opposite these two rows, a catenary (K1, K2) being fixed at each of the ends of these two rows, bearing on the pulley (O) and carrying a weight (L1, L2) at a lower end, one or more intermediate rows of dipoles (D3, D4; D5, D6) located between the upper and lower rows having two ends fixed respectively at the catenary (K1) relating to the upper row of dipoles. 5.- Antenna according to any one of claims 2 to 4, characterized in that it comprises, for each dipole (D1), a supply line (C1) carried by the transverse arm (B1) and the beam ( B1), on which said first end of the dipole (D1) is fixed, and by the mast (M). 6.- Antenna according to any one of claims 2 to 5, characterized in that the beams (P1-P8) are fixed on the mast (M) so as to be able to pivot around an axis (X) perpendicular to a plane containing these beams, a stay (H1-H4) connecting a point of each beam (P1, P8), distant from said axis (X), at a point of said reinforcement located above the axis (X). 7.- Antenna according to claim 6, characterized in that each guy (H1) relating to an upper beam (P1, P2) is inclined relative to the mast (M) and is connected to an upper end thereof, while that each guy (H2-H4) relative to a beam (P3, P5, P7) located directly above an upper beam (P1, P2) is parallel to the mast (M) and is connected to a corresponding point on a beam (P1, P3) located above. 8.- Antenna according to any one of claims 2 to 7, characterized in that it comprises a reflector (Rb) including a plurality of horizontal (F) and vertical (F1) wires located in a plane containing the beams (P1 -P8), a lateral catenary (K4) extending between two upper (P1) and lower (P7) beams and bearing on two free ends thereof, vertical rods (T1, T2) fixed in a region d end of these upper (P1) and lower (P7) beams and oriented respectively upwards and downwards, ends of the horizontal wires (F) being fixed to the lateral catenary (K4) and to the vertical rods (T1, T2) , a fixing being carried out at each crossing point between any horizontal wire (F) or beam (P1-P8) and any vertical wire (F1) or rod (T1, T2) or a stay cable (H1, H4). 9.- Antenna according to any one of claims 2 to 8, characterized in that the beams (p1-p8) extend in a plane distant from the mast (M), bars (v) fixed on the mast, transversely to said plane and opposite the beams, supporting them, a guy (h5) parallel to the mast (M) connecting two free ends of any two bars (v) arranged one below the other, and connecting the bar (v) supporting the upper beams (p1, p2) to a bar (v) located above. 10.- Antenna according to any one of the preceding claims, characterized in that it comprises a reflector (Rb) including a plurality of horizontal wires (F) and in that said base (M1) is made of reinforced concrete and comprises a tubular enclosure (M3) extending vertically to the vicinity of a lower edge of the reflector (Rb).

Images