EP0634058B1 - Directional antenna, in particular a dipole antenna - Google Patents

Abstract

In order to produce a directional antenna which is superior to those of the prior art, and especially a dipole antenna which is easier to manufacture and of simpler design, and also has enhanced electrical properties, the dipole with its circuit balancing element (7) according to the invention is made of the material of the reflector (5). The dipole and the circuit balancing element (7) project from the reflector wall (5) through corresponding areas which are cut out and/or punched out, up to a region (11) where they join with the remaining material of the reflector wall (5), and are preferably bent outwardly in relation to the plane of the reflector wall in the region of the point (11) where they immediately join with the remaining material of the reflector wall (5).

Description

The invention relates to a directional antenna, in particular a dipole antenna according to the preamble of claim 1.

Dipole antennas are often used as symmetrically fed directional antennas. In principle, it is a horizontal or vertical, symmetrical linear antenna fed in the middle, depending on the polarization of the electromagnetic waves. If the dipoles are offset by 90 ° to one another, a circularly polarized electromagnetic wave can ultimately also be generated.

The directional antenna consisting of one or more dipoles usually includes one or more radiators, which essentially consist of the two dipole halves and the so-called symmetry loop, via which the dipole, which usually consists of the two rod halves, is offset with an offset to the reflector wall carrying it is oriented essentially parallel, but also in an angular form.

A directional antenna according to the prior art formed from a dipole antenna, or dipole field for short, is explained with reference to FIGS. 10a to 10c.

The directional antenna shown in Figures 10a to 10c comprises a dipole field 1 with z. B. two dipoles 3, which are arranged in front of a conductive, flat or shaped reflector 5 at a distance from it. In the example shown, the arrangement thus comprises two radiators 2, which are arranged at a distance a in parallel alignment with one another and with an offset b in front of the reflector wall.

The two dipoles 3 shown in FIGS. 10a to 10c are held and fastened to the reflector 5 by means of a so-called symmetry 7, which usually consist of two holding rods 7 'running vertically to the reflector wall 5 and carrying the dipoles 3.

The entire arrangement is usually protected in what is known as a radome 9, that is to say a protective housing.

The radiation diagram in the E and H planes of a dipole field is essentially determined by the shape and the mechanical dimensions of the reflector and the number and arrangement of the dipoles.

In order, for example, to achieve different directional characteristics in the dipole antenna previously known according to FIGS. 10a to 10c, both the reflector width c, i.e. the width of the reflector wall 5, as well as the distances a for the lateral offset transversely to the parallel dipoles 3 and the distance b from the dipoles to the reflector 5 can be varied.

Directional antennas are used for the current mobile radio networks used with vertical polarization, which have a horizontal directional characteristic of approx. 60 ° to 120 ° at the 3 dB point. These values can be achieved with one or two radiators in the arrangement shown. However, the arrangement of the dipoles 3, the symmetry loop 7 and including the connection point 11 of the symmetry loop 7 on the reflector 5, the so-called base point 11, and the offset must be optimized for any desired half-value width.

This means that when implementing an antenna family according to the desired half-value width, different radiators and different positions on the reflector are required.

The dipole antennas described in accordance with the prior art each comprise a plurality of individual parts which then have to be mechanically connected to one another. This is done through the common connection methods, such as. B. screws, welding, soldering. The individual components for the dipole rods, the balancing loop and the connection points 11 for attachment to the reflector can be tubular, flat or else shaped depending on requirements. The individual parts are manufactured with the usual manufacturing tolerances. This also applies to the assembly in the assembled state.

It must be borne in mind that the manufacturing-related tolerances also affect the electrical properties (e.g. VSWR) of the single radiator and, if several radiators are arranged, the impedance of the entire antenna.

This requires close tolerances to be maintained, particularly for series production, both for the individual parts and for the assemblies.

When assembling the individual parts, it must also be taken into account that mechanical connection points can also have retrospective effects on the antenna function. If several RF carrier frequencies are present at the individual connection points of the individual parts at the same time, they can mix with non-linearities and generate intermodulation products which have a disruptive effect on the operation of a mobile radio network. This effect can be exacerbated by contact corrosion if the materials are paired poorly and used for a long time.

A generic dipole arrangement, in which a dipole emitter formed as a sheet metal part is screwed to the reflector, has become known from DE 91 04 722 U1. In order to simplify the construction of a dipole and to reduce the manufacturing and material costs, it is proposed that the dipole halves and the support struts carrying the dipole halves, i.e. the so-called symmetry, as a uniform stamped and bent part made of sheet metal , preferably made of aluminum sheet. For this purpose, the dipole halves are U-shaped and open to the reflector. Adequate stiffening of the support struts is to be achieved by suitable sheet metal deformations such as embossing, beads, folding etc.

At the base, the support struts are provided with corresponding holes so that the dipole thus produced can be screwed onto the reflector.

The dipole is attached to the reflector using screws. For this purpose, holes are drilled at the foot of the support struts, so that the screws mentioned for the fixed attachment of the dipole on the reflector can be passed through and tightened on the reflector. However, this mechanical connection has the disadvantages mentioned above.

It is therefore an object of the present invention to overcome the disadvantages of the prior art and to provide a directional antenna, in particular a dipole antenna, which is comparatively simple to produce compared to the prior art and also has improved electrical properties.

The object is achieved according to the features specified in claim 1. Advantageous embodiments of the invention are specified in the subclaims.

The present invention achieves significant improvements over the prior art with surprisingly simple means.

On the one hand, the invention provides that the dipoles of the dipole antenna, including the so-called symmetry loop, i.e. that is, the holding struts for the dipoles are cut out of the material of the reflector wall, for example punched out, and only with an electrically conductive connection point being left to the remaining material of the reflector wall. The dipole antenna is then simply folded out, i.e. Bend out or edge the radiator including the dipole to form the so-called base at the junction from the radiator to the reflector wall. A laborious, time-consuming assembly of various individual parts, which results in problems with the tolerances to be observed, is no longer necessary.

The contour cuts can be exactly reproduced with high-precision tools, for example in the form of a computer-controlled laser or using a coordinate punching tool with tight tolerances. The spotlight and reflector are made of the same material. Thereby above all, possible contact corrosion can be avoided.

However, it is particularly advantageous that there are no mechanical connection points at which the disadvantages described in the prior art can occur.

The alignment of the radiator with respect to the plane of the reflector can be carried out at different angles. This allows a problem-free adaptation to a desired dipole field on the one hand and on the other hand enables a particularly flat design. Directional diagrams with half-widths of approx. 60 to 120 ° can be realized simply by using different bending angles.

In a preferred embodiment of the invention, a very flat design of such a dipole antenna can be realized. Due to a V-shaped course of the symmetry, an electrical length of approximately λ / 4 is achieved, although the dipole is, for example, a distance of approximately λ / 8 from the reflector.

Since the base point of the spotlight is continuously conductive to the reflector, this construction principle is particularly suitable for feeding by means of a strip line

Further advantages of the invention lie in the diverse possibilities of feeding.

A feed can take place, for example, with a coaxial cable or else with a strip line, with one half of the balancing loop and the reflector being able to be used as an outer conductor.

Figur 1a bis 1c:

eine schematische Draufsicht und Längsseiten- und Quersseitenan-sicht eines ersten Ausführungsbeispieles der Erfindung;

Figur 1 d:

eine ausschnittsweise vereinfachte perspektivische Darstellung eines aus dem Reflektor herausgeklappten Strahlers;

Figur 2 :

eine Quer- oder Stirnseitenansicht eines in anderem Winkel gegenüber der Reflektorwand ausgerichtet verlaufenden Strahlers;

Figur 3 :

eine weitere Querseiten- oder Stirnseitenansicht bei in einem geschlossenen Radom untergebrachten Dipolantenne;

Figur 4a und 4b :

eine schematische Draufsicht und Querseitenansicht auf eine Dipolantenne einschließlich einer Anspeisung der Dipole in Streifenleitertechnik;

Figur 5 :

eine Quer- oder Stirnseitenansicht auf ein zu Figur 4b abgewandeltes Ausführungsbeispiel einer Dipolantenne;

Figur 6a und 6b :

eine Draufsicht und eine Queroder Stirnseitenansicht auf eine Dipolantenne mit einer Anspeisung der Dipole in Streifenleitertechnik mit Trägersubstrat;

Figur 7 :

eine Quer- oder Stirnseitenansicht einer gegenüber Figur 6b abgewandelten Dipolantenne;

Figur 8a und 8b :

eine Draufsicht und eine Quer-oder Stirnseitenansicht auf eine Dipolantenne mit einer Einspeisung der Dipole in Koaxialtechnik;

Figur 9 :

eine Quer- oder Stirnseitenansicht auf einen zu Figur 8b abgewandelten Dipol;

Figur 10a bis 10c :

eine Draufsicht, Längsseiten-und Querseitenansicht auf eine Dipolantenne nach dem Stand der Technik.

Further advantages, details and features of the invention follow from the exemplary embodiments shown with reference to drawings. The individual shows:

Figure 1a to 1c:

is a schematic plan view and long side and transverse side view of a first embodiment of the invention;

Figure 1 d:

a fragmentary simplified perspective view of a radiator folded out of the reflector;

Figure 2:

a transverse or end view of a radiator aligned at a different angle with respect to the reflector wall;

Figure 3:

a further transverse side or end view with dipole antenna housed in a closed radome;

Figures 4a and 4b:

a schematic plan view and transverse side view of a dipole antenna including a feed of the dipoles in strip line technology;

Figure 5:

a transverse or end view of an embodiment of a dipole antenna modified to Figure 4b;

Figures 6a and 6b:

a plan view and a transverse or frontal view of a dipole antenna with a feed of the dipoles in stripline technology with carrier substrate;

Figure 7:

a transverse or end view of a dipole antenna modified compared to Figure 6b;

Figures 8a and 8b:

a plan view and a transverse or end view of a dipole antenna with a feed of the dipoles in coaxial technology;

Figure 9:

a transverse or end view of a dipole modified to Figure 8b;

Figure 10a to 10c:

a plan view, longitudinal side and transverse side view of a dipole antenna according to the prior art.

A first exemplary embodiment according to the invention for a directional antenna, i.e. a dipole antenna, shown with two dipoles.

As can be seen from the schematic perspective illustration according to FIG. 1d, the essentially L-shaped form of a dipole 3 with the symmetry 7 assigned to the respective two parts of the dipole is punched out of the material of the reflector 5, for example by means of a computer-controlled laser or a coordinate punching tool the connection point 11 to the reflector wall, that is to say at the base, by bending or edging according to the desired bending angle α. In the exemplary embodiment according to FIGS. 1a to 1d, the angle α is approximately 30 to 60 °.

According to FIG. 1d, an opening 13 is left in the reflector field 5 in the area of the punched out, which but generally does not necessarily have to be disadvantageous for the transmitting and receiving function of the directional antenna in general, it may even have advantages. The forward / backward ratio of the dipole field can be influenced by targeted dimensioning of the punched-out shape in the form of the opening 13.

If necessary, however, the opening 13 could also be closed with electrically conductive material, for example by gluing on a metal foil, it being possible for the metal foil to be provided with a metal layer formed on the rear side without making a galvanic contact with the reflector plate.

By changing the distance between the two dipoles and by changing the bending angle and thus changing the distance of the dipoles 3 from the plane of the reflector 5, a specific horizontal radiation diagram can be set. In other words, an adjustment of the radiation diagram can be made possible only by changing the bending angle α.

In addition, if required, the production of a directional antenna with different geometrical dimensions, that is to say a different size for the distance a between the dipoles and a different length of the dipoles, can be made possible only by changing the desired data in the computer-controlled laser or by changing the punching tool.

For the sake of simplicity, the opening 13 in the reflector 5 itself, which is created by the cutting or punching out, has not been shown in the plan view according to FIG. Reference is made here to the partial representation according to FIG. 1d.

As can be seen from Figure 1d, the symmetry loop 7, i.e. specifically the two parallel band-shaped or strip-shaped halves of the symmetry loop 7 can be designed with a lower wall section 7a connecting these two halves. This opens the possibility, after punching out or cutting out the dipoles 3 with the symmetry loop 7, to bend them out about the common bending line 11 relative to the plane of the reflector 5. Deviating from this - as shown in the other figures shown only schematically - the two halves of the symmetry loop 7 can be punched out individually and each bent out and set up over a separate bending line 11 at the base point relative to the plane of the reflector 5 (in FIG dotted). The bending line 11 is then aligned with the transverse cutting or punching line lying between the two halves of the symmetry loop 7, which lies in the plane of the reflector, if this is introduced and provided at all.

In FIG. 2, in deviation from FIG. 1c, the orientation of the symmetry loop at a bending angle α of 90 °, that is to say perpendicular to the plane of the reflector wall, is shown with a transverse or end view of the dipole antenna.

FIG. 3 shows that the dipole antenna according to the invention is in principle also arranged in a closed radome 15 as a protective housing.

The exemplary embodiment according to FIGS. 4a and 4b and according to FIG. 5 essentially corresponds to the exemplary embodiment according to FIGS. 1a to 1d or FIG. 2. In FIG. 4a, 4b and FIG. 5, a possible feeding of the dipole using a strip line 17 is shown in principle. One half 7a of the symmetry loop 7 and the reflector 5 are used as outer conductors.

For example, in parallel to the dipoles 3, the connecting conductor 17 'is laid in the middle at a short distance above the reflector plate 5 which represents the outer conductor. The strip line 17 'then branches at a branching point 23 between the two halves 7a of the respective symmetry 7 facing each other. The line runs at a small uniform distance d above the associated half 7a of the symmetry 7, that is to say preferably at the same angle α with respect to the plane of the reflector. At the transition from the one half 7a of the balancing 7 to the respectively associated part of the dipole 3, an angled line piece 17 "then connects, which at the adjacent transition from the other half of the balancing 7 to the associated part of the dipole into an angled line to be run on this connection point Line section 17 "passes over. This defines the actual feed point 23.

In the case of the exemplary embodiment according to FIG. 5 at a bending angle α = 90 °, the branching point 23 lies approximately at the level of the opposite dipoles 3 of the two radiators 2. From the connecting side 17 ′ which is laid at a small distance in parallel above the reflector 5, there is a vertical intermediate line 18 in a parallel alignment between the two halves of the symmetry 7 to the high branch point 23.

The angular laying of the strip conductors 17 ″ and 17 ″ ″ also takes place in the exemplary embodiment according to FIG. 5 in a manner similar to that explained with reference to FIGS. 4a and 4b.

In the exemplary embodiment shown below with reference to FIGS. 6a and 6b and 7, the dipoles 3 are also fed using stripline technology, using a carrier substrate 25.

The carrier substrate 25 is anchored in a mechanically overlying manner, in particular at a bending angle α of less than 90 ° between the two opposite symmetries 7 of the two dipoles 3 shown in the figures (for example via an insulating fixing 27 made of plastic). On this carrier substrate 25, the strip line 17 is formed with the connecting conductor 17 ', from the branching point 23 of which the connecting lines 17' then lead to the respective feed point of the two dipoles 3.

With a bending angle α of 90 ° (FIG. 7) or less, the carrier substrate 25 can also be attached at a greater distance from the reflector wall 5, for example at least approximately at the height of the dipoles 3 or slightly below, by means of the fixation 27.

Based on the exemplary embodiments according to FIGS. 8a, 8b and 9, the case is shown in which the dipoles 3 are fed with coaxial cables. In this respect, the line course corresponds essentially to the exemplary embodiment formed in stripline technology according to FIGS. 4a, 4b and 5, the outer conductors 17a of the two coaxial connecting conductors 17 'ending approximately at the level of the dipoles and the outer conductors 17a here separately on the respective half 7a of the balancing 7 are connected in a conductive manner, while the inner conductor 17b leads via the subsequent conductor pieces 17 ″ and 17 ″ ″ to the respective feed point 23 at the transition of the other half of the symmetry 7 to the associated part of the dipole 3 originating therefrom.

Claims (16)

1. Directional antenna, in particular dipole antenna, with at least one radiator (2) in the form of a dipole (3), inclusive of an associated symmetrical arrangement (7) which supports the dipole (3), over which the at least one dipole (3) is held on a reflector (5), the respective dipole half (3) being formed integrally with the associated part of the symmetrical arrangement (7), characterized in that the dipole (3), inclusive of its symmetrical arrangement (7), is made from the material of the reflector (5), which is designed as a conductive wall, by separating the dipole (3) and the symmetrical arrangement (7) from the reflector wall (5) by corresponding cutting and/or punching out as far as a junction (11) with the remaining material of the reflector wall (5), and in that the symmetrical arrangement (7) is bent out at an angle with respect to the reflector wall (5).
2. Directional antenna according to Claim 1, characterized in that, in the region of the junction (11), the symmetrical arrangement (7) is bent out with respect to the plane of the remaining material -of the reflector wall (5).
3. Directional antenna according to Claim 1 or 2, characterized in that the bend angle α is 90°.
4. Directional antenna according to Claim 1 or 2, characterized in that the bend angle α is 65° or less.
5. Directional antenna , according to Claim 4, characterized in that the bend angle α is less than 45°.
6. Directional antenna according to one of Claims 1 to 5, characterized in that the opening (13) in the material of the reflector (5), produced in the region of the detached radiator (2), is closed off by means of an electrically conductive layer.
7. Directional antenna according to Claim 6, characterized in that the electrically conductive layer consists of a metal foil.
8. Directional antenna according to Claim 7, characterized in that, on its surface remote from the material of the reflector, the metal foil is provided with the electrically conductive metal layer.
9. Directional antenna according to one of Claims 1 to 8, characterized in that the directional characteristic of the dipole antenna can be changed by altering the bend angle (α).
10. Directional antenna according to one of Claims 1 to 9, characterized in that it consists of a plurality of dipoles (3) and is designed overall in a single piece.
11. Directional antenna according to one of Claims 1 to 10, characterized in that the dipoles (3) are fed by means of a stripline (17), the one half (7a) of the balancing loop (7) of a dipole (3) and the reflector wall (5) being used as outer conductors.
12. Directional antenna according to Claim 11, characterized in that stripline (17; 17', 17'', 17''') extends at a small distance (d) above the reflector (5) and the respective one half (7a) of the balancing loop (7).
13. Directional antenna according to Claim 11 or 12, characterized in that the dipoles (3) are fed by means of a stripline extending on a support substrate (25).
14. Directional antenna according to Claim 13, characterized in that the support substrate (25) for the stripline (17) is arranged laterally offset transversely with respect to the plane of the reflector (5), by means of an insulating fixture (27) on the dipoles (3).
15. Directional antenna according to one of Claims 1 to 10, characterized in that the dipoles are fed using coaxial cables (24).
16. Directional antenna according to one of Claims 1 to 15, characterized in that the distance between the dipoles (3) and the reflector wall (5) is at least 10%, preferably less than 30%, 40% or about 50% of the electrical wavelength.

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