EP1344277B1 - Antenna, in particular mobile radio antenna - Google Patents

Abstract

An improved antenna includes a dielectric body arranged entirely or mostly (e.g., with more than 40% such as more than 50% or 60% of its volume and/or of its weight) underneath antenna radiating elements provided for lower frequency operation; and entirely, or mostly (e.g., 40%, 50% or 60% of its volume and/or of its weight) above antenna radiating elements provided for upper frequency operation.

Description

The invention relates to an antenna, in particular mobile radio antenna, according to claims 1-4.

Mobile radio antennas for mobile radio base stations are usually constructed so that a plurality of radiator arrangements are provided in front of a reflector plane in the vertical direction one above the other. Thus, these radiator arrangements can consist of a multiplicity of dipole radiators, for example also in the form of crossed dipoles, in the form of a dipole square, etc., that is to say in the form of radiator types having a dipole structure. Likewise, antennas are known as so-called patch radiators.

As is known, different mobile radio frequency ranges are provided, for example for the so-called GSM 900 network of the 900 MHz frequency range, for the so-called GSM 1,800 network of the 1,800 MHz range or for example also the 1,900 MHz frequency range, as is customary in the USA and used in a large number of other states. For the next mobile generation, namely The UMTS network has a frequency range around 2,000 MHz.

It is therefore customary to design such mobile radio antennas at least as dual-band antennas, whereby triple-band antennas (for example for the 900 for the 1,800 and the 1,900 or for example the 2,000 MHz band) are also suitable.

In addition, the antennas are preferably designed as dual-polarized antennas for operation with a polarization of + 45 ° and -45 °. It is also customary to protect such antennas by a plastic hood against the weather. However, this so-called radome has mainly to perform mechanical tasks and envelops all the radiant antenna parts equally. Such an antenna for operation in at least two mutually offset frequency bands has become known for example from DE 198 23 749 A1.

In such dual-band antennas or in general multi-band antennas, however, the problem often arises that the half-widths of the radiation pattern in the azimuth for the different frequency ranges, ie for the different frequency bands have different widths. In addition, in the case of dual-band or, in general, multi-band antennas, there is also the problem that cross-polar components can result, which lead to a deterioration in the radiation characteristic. Finally, however, the VSWR ratio and / or the decoupling can be adversely affected.

Basically, from the prior art a variety known antennas, but which are designed for only a single frequency band range, so can only receive and send in a frequency range. These may be linearly polarized or even dual polarized antennas for transmitting only in this mentioned a frequency band. Such operating only in a frequency band antennas are known for example from the publications DE 199 01 179 A1, DE 198 21 223 A1, DE 196 27 015 C2, DE US 6,069,590 A and US 6,069,586 A. However, all of these prior publications address different problems, typically the question of decoupling two polarizations in the same frequency band. For this purpose, usually electrically conductive parts are used to generate parasitic radiation decoupling elements.

Finally, a dual-band antenna array is known from WO 99/59233 A. This antenna array comprises patch antenna elements, above which dipole radiators are arranged in the form of cross dipoles. The cross dipoles are arranged above a conductive plate, which serves as a parasitic element for the patch antenna and as a reflector for the cross dipoles.

In contrast, it is an object of the present invention, starting from the generic antenna according to DE 198 23 749 A1 at least for operation in two frequency ranges or bands (regardless of whether the antenna is operated only in one polarization or in multiple polarizations) a significant improvement with respect to the half-width and / or the suppression of the cross-polar component and / or the VSWR ratio and / or with respect to the decoupling or a bandwidth increase realize.

The object is achieved according to the features indicated in claim 1, 2, 3 and / or 4 according to the invention. Advantageous embodiments of the invention are specified in the subclaims.

It must be described as extremely surprising that the above-mentioned advantages can be realized with comparatively simple means. In this case, the mentioned dielectric body in plan view be designed n-polygonal. It may, for example, extend above a dipole radiator arrangement, for example in the form of a crossed dipole, for example using crossed dipoles, dipole squares or using patch radiators.

In addition, the dielectric body according to the invention, which is also referred to below as a dielectric tuning plate in plan view, be designed symmetrically in plan view, in particular at least have sections which are formed and arranged symmetrically with respect to a single radiator arrangement.

In addition, it proves to be advantageous, complementary or alternatively corresponding dielectric body to be arranged between two usually vertically above each other in front of a vertical reflector plane arranged radiator arrangements at a distance in front of the reflector sheet.

The dielectric bodies according to the invention can be made of suitable plastic material, for example Polystyrene, fiberglass (GRP) etc. exist.

Preferably, a material is used for the dielectric body whose dielectric does not have a high dissipation factor.

The invention has a particularly favorable effect, for example, in the frequency range from 800 to 1000 MHz and from 1700 to 2200 MHz.

Preferably, the dielectric body is designed plate-shaped and extends in a parallel plane in front of the reflector. However, it may be provided with existing of the same material fasteners or feet (generally spacers, etc.) to arrange it in a predetermined, considered favorable for distance in front of the reflector sheet. Preferably, the extension height is lower than λ / 2.

With the antenna according to the invention can be realized a significant reduction in the frequency dependence of the half-width. Frequently, the mobile radio antennas are set to have a half width of 65 °. However, this 65 ° half-width can usually not be set completely identically for the at least two frequency bands, especially if they are very broadband. Therefore, a deviation with respect to the at least two provided frequency bands of, for example, 65 ° ± 10 ° (or at least ± 7 °) is common in the prior art. According to the invention, this deviation can now be improved to 65 ° ± 5 ° (or even only ± 4 ° and less).

As is known, the antennas are often adjusted so that they radiate each in a horizontal 120 'sector angle. This is also called sector. As a result, three sectors are formed per antenna mast. In the sector boundaries, therefore, a corresponding mobile radio antenna radiates at an angle of + 60 ° or -60 °, the suppression of the cross-polar component, in particular at the sector boundaries according to the prior art, especially in broadband antennas having poor values. With the antenna according to the invention using the dielectric tuning body, a ratio of 10 dB or even better with respect to the suppression of the cross-polar component can be realized here even in the sector boundaries at ± 60 °.

If, in accordance with the invention, it is not absolutely necessary to use cross-polarized emitters in a multiband antenna arrangement (ie at least in a dual-band antenna arrangement), the decoupling can likewise be significantly improved in this case. The required decoupling has a magnitude of more than 30 dB. This is a very big problem, especially with broadband antennas or antennas with electrically adjustable lowering. In the case of the antenna according to the invention, this value is significantly exceeded, especially when the antennas are broadband and additionally electrically adjustable.

Finally, there is also a positive bandwidth expansion, especially for the higher frequencies.

In summary, it can be stated that the advantages mentioned above are consistent with the invention have positive effect on dielectric body especially for the higher frequency range or the intended multiple frequency ranges, the inventive measures have almost no effect on the lower or respectively lowest frequency ranges provided.

Figur 1 :

eine schematische Draufsicht auf ein erstes Ausführungsbeispiel einer erfindungsgemäßen Antenne für den Mobilfunkbereich mit mehreren Strahlern und einem erfindungsgemäß vorgesehenen dielektrischen Körper;

Figur 2 :

eine schematische Querseitenansicht senkrecht zur vertikalen Längserstreckung der Antenne in Figur 1;

Figur 3 :

eine vertikale Stirnseitenansicht der in Figur 1 und 2 wiedergegebenen Antenne;

Figur 4 :

ein zu Figur 1 abgewandeltes Ausführungsbeispiel in Draufsicht;

Figur 5 :

eine entsprechende Querseitenansicht der in Figur 4 wiedergegebenen Antenne;

Figur 6 :

eine Stirnseitenansicht (der in den Figuren 4 und 5 wiedergegebenen Antenne);

Figur 7 :

eine schematische Draufsicht auf einen aus meh- reren Teilen bestehenden dielektrischen Körper; und

Figur 8 :

eine schematische Querschnittdarstellung eines mit Distanzhaltern oder Füßen versehenen dielektrischen Körpers.

The invention will be explained in more detail with reference to two embodiments. In detail:

FIG. 1:

a schematic plan view of a first embodiment of an antenna according to the invention for the mobile radio sector with a plurality of radiators and a dielectric body provided according to the invention;

FIG. 2:

a schematic transverse side view perpendicular to the vertical longitudinal extent of the antenna in Figure 1;

FIG. 3:

a vertical end view of the reproduced in Figure 1 and 2 antenna;

FIG. 4:

an embodiment of Figure 1 modified in plan view;

FIG. 5:

a corresponding transverse side view of the reproduced in Figure 4 antenna;

FIG. 6:

an end view (of the antenna shown in Figures 4 and 5);

FIG. 7:

a schematic plan view of a reren parts existing dielectric body; and

FIG. 8:

a schematic cross-sectional view of a provided with spacers or feet dielectric body.

In a first exemplary embodiment according to FIGS. 1 to 3, the antenna 1 comprises five individual radiators, namely two first radiators 4a offset in the vertical direction for a first lower frequency range and three vertically offset second radiators 4b for a higher frequency range.

The first radiators 4a are dipole radiators 7, which are arranged in the manner of a dipole square 13 and held by so-called symmetries 7 ', which run at least partially to their common center, and are fastened to an electrically conductive reflector 11.

In the exemplary embodiment shown, the second radiators 4b arranged within these first radiators 4a are formed in the manner of a crossed dipole 15 with two dipoles perpendicular to one another.

The middle radiator device 4b, which is also provided for the group of the second radiators 4b and is provided between the first radiators 4a, again consists in this embodiment of a dipole square 17 formed of four dipoles 16, which in principle is comparable and similar to the large dipole squares of the first radiators 4a ,

The mentioned radiators are arranged in front of the vertically oriented reflector 11, wherein the reflector 11 may be formed, for example, from a reflector plate 11 ', with two edge sections 12' set up at its vertical sides 12 from the reflector plane in the emission direction.

As is apparent from the illustrations according to FIGS. 1 to 3, in order to improve various antenna properties, a dielectric body 21 is furthermore provided which, in the exemplary embodiment shown, is plate-shaped and extends at least substantially parallel to the reflector plane. It is preferably located at a distance in front of the reflector plane that is smaller than λ / 2 of the highest transmitted frequency range or smaller than λ / 2 of the associated center frequency of the highest frequency range. The thickness of the dielectric body can be chosen differently within wide ranges. Good values are between 2% to 30%, in particular 5% to 10%, of the distance of the radiator elements of the first radiators 4a from the associated reflector 11.

As can be seen in particular from the top view according to FIG. 1 in relation to the two side views according to FIGS. 2 and 3, the dielectric body 21 has at least one extension component 22 which runs parallel to the plane of the reflector 11 that is greater than its thickness and / or is greater than the distance between its center plane to the reflector 11 level and / or greater than the distance between the radiator elements 4b, 15 of the radiator elements provided for the upper frequency range to the associated plane of the reflector 11th

• aus dem Abstand zwischen der Ebene des Reflektors 11 und dem dielektrischen Körper 21, oder
• aus dem Abstand zwischen der Ebene des Reflektors 11 und einer durch den dielektrischen Körper 21 hindurch verlaufenden Mittelebene, oder
• aus dem Abstand zwischen der Ebene des Reflektors 11 und der zur Reflektorebene abweisend liegenden äußeren Begrenzungsfläche des dielektrischen Körpers 21.

The dielectric body 21 in question, or at least the size of the surface of the dielectric body 21, as it results in perpendicular projection onto the plane of the reflector 11, can also be greater than the square of the distance measure which results

• from the distance between the plane of the reflector 11 and the dielectric body 21, or
• from the distance between the plane of the reflector 11 and a center plane passing through the dielectric body 21, or
• from the distance between the plane of the reflector 11 and the reflector plane facing away from the outer boundary surface of the dielectric body 21st

As can also be seen from the drawings, the non-protective dielectric body is provided so as to extend in parallel at least partially above parts of the radiator assembly at a distance in front of the reflector 11.

In this case, the dielectric body 21 extending parallel to the reflector 11 can have an areal dimension which is greater than the planar extension dimension of possible spacers, feet or other elements belonging to the dielectric body 21 that is parallel to the plane of the reflector 11 or with this connected or the reflector 11 extending fasteners.

Finally, it also proves to be advantageous if the dielectric body is arranged completely or at least with a section at a distance in front of the reflector 11, and above the radiator arrangement provided for the upper frequency range. It also proves to be advantageous if the dielectric body is located entirely or at least with a section below the radiator arrangement provided for the lower frequency range. Both of the aforementioned conditions should preferably be fulfilled simultaneously, the effect being particularly favorable when the dielectric body 21 is thus located entirely or with at least one section above the radiator arrangement provided for the upper frequency range and at the same time below the radiator arrangement provided for the lower frequency range and extends completely or substantially parallel to the reflector. If the dielectric body is not located entirely above the radiator provided for the upper frequency range and not quite below the radiator provided for the lower frequency range, the effect is particularly advantageous when the dielectric body 21 is related to its total volume and / or Total weight is at least sufficiently in this position, ie, for example, with more than at least 30%, 40%, 50% or especially more than 60%, 70%, 80% or 90% of its total weight and / or volume specified area is located.

In the exemplary embodiments shown, it can also be seen that the at least one dielectric body 21 in the projection perpendicular to the reflector 11 located therebelow is smaller than the reflector sheet. However, the dielectric body may also have a size that ultimately corresponds to the size of the reflector 11.

In the embodiment shown, the dielectric body 21 is arranged with a first portion symmetrically within the first radiator 4a and thus above the second radiator 4b therein, in the embodiment shown - since the first radiator 4a are formed from a dipole square - in a square shape.

The dielectric body 21 formed in this way, that is to say the dielectric tuning plate 21, is provided in the exemplary embodiment shown with a central vertical section 21b which connects the sections 21a in the region of the dipole squares 13 of the two first radiator arrangements 4a offset in the illustrated embodiment. In the exemplary embodiment shown, therefore, the dielectric tuning plate 21 thus formed is designed in one piece. However, it could also consist of several parts which correspond at least approximately to the reproduced in Figure 1 form, so for example, comprise two sections 21a, which are square and arranged according to the dipole square 13 each concentric with this parallel to the reflector plane. Between these two sections 21a, the longer connecting section 21b could then be provided running.

In particular, for the higher frequencies, for example, from 1,700 to 2,200 MHz (for example, up to 2,170 MHz), the half-width, the value for the suppression of the cross-polar component, the decoupling, as well as the bandwidth increase can be improved in an advantageous manner. Adverse influences for the lower frequency range or the low frequency bands are virtually undetectable.

As can be seen only indirectly from the drawings, the dielectric body is preferably mechanically attached to the radiators, for example at their symmetries.

The embodiment according to FIGS. 4 to 6 differs from that according to FIGS. 1 to 3 in that patch emitters 27 are used for the second emitters 4b (instead of the cross emitters 15), ie surface emitters, for example in the form of a square emitter element, which have a suitable spacing height in front of the reflector 11 are aligned centrally and symmetrically with the same polarization orientation to the first radiators 4a. Between the two patch radiators 27, each provided in the first radiator 4a, another patch radiator 27 is provided in the middle, which may lie at a different height, as is apparent in particular from the longitudinal side view according to FIG. 5 and the frontal view according to FIG. But also the remaining first, formed in the manner of a dipole square dipole radiator 4a could also be replaced by patch radiators, so that the antenna is constructed as a whole patch antenna.

Also in this antenna, a corresponding dielectric body 21 is provided as a dielectric tuning element or as a dielectric tuning plate 21, as can be seen from the illustrations.

The dielectric body 21 can be anchored and held by suitable means, for example, to the symmetries 7 'of the individual radiator elements. He may also be provided with feet, for example, also made of dielectric or metal, so also be conductive.

The dielectric body 21 does not have to be formed integrally. It may also consist of several separate separate sections, which are then joined together to a desired shape quasi, it is harmless if the individual elements from which the dielectric body 21 may be formed in the mounting direction not together over the entire surface, but for example in one schematic top view of Figure 7 between the individual elements gap gaps 31 remain.

With reference to Figure 8, it is shown only schematically with respect to a cross-section through the element 21 that the dielectric tuning element or body may also be provided with spacers for attachment to the reflector 21, wherein the spacers 41 may be separate spacers or of the same material can exist, as the dielectric body 21 itself. Where and in what size the spacers or spacers are formed, can be varied in wide ranges arbitrarily.

Also, the shape may differ widely. The shape can be changed so that the desired advantageous antenna properties can be set and realized.

Claims (17)

1. Antenna for operation in at least two frequency bands, having the following features:

   - the antenna is provided with a protective shroud composed of non-conductive material,

   - the radiating elements of the antenna are arranged underneath the protective shroud and in front of the reflector (11),

   - the radiating elements (4a, 13) for a lower frequency band are arranged at a first distance, or in a first distance range, in front of the reflector (11),

   - the radiating elements (4b, 15) for the higher frequency band are, in contrast, arranged at a second distance, or in a second distance range, in front of the reflector (11), but closer to it,

   characterized by the following further features:

   - at least one dielectric body (21) which does not form the protective shroud is provided,

   - more than 30% of the volume, and/or more than 30% of the weight, of the at least one dielectric body (21) is arranged in the region between the reflector (11) and the first distance or the first distance range of the radiating elements (4a, 13) for the lower frequency band, and

   - more than 30% of the volume and/or more than 30% of the weight of the at least one dielectric body (21) is arranged, as seen from the reflector (11), at more than the second distance or the second distance range for the radiating elements (4b, 15) which are provided for the upper frequency band.
2. Antenna according to the precharacterizing clause of Claim 1
   characterized by the following further features:

   - at least one dielectric body (21) which does not form the protective shroud is provided, and

   - at least part of the dielectric body (21) is arranged in the distance area which extends parallel to the reflector (11) and is provided by the radiating elements (4a, 13) for the lower frequency band and by the radiating elements (4b, 15) for the upper frequency band, and

   - the dielectric body (21) also has an extent component (22) which runs parallel to the plane of the reflector (11), is greater than its thickness running at right angles to the plane of the reflector (11), and/or is greater than the distance between the centre plane of the dielectric body (21) and the plane of the reflector (11), and/or is greater than the distance between the antenna element (4b, 15) of those antenna elements (4b, 15) which are provided for the upper frequency range and the associated plane of the reflector (11).
3. Antenna according to the precharacterizing clause of Claim 1
   characterized by the following further features:

   a) at least one dielectric body (21) which does not form the protective shroud is provided, and

   b) in a vertical plan view of the reflector (11), the dielectric body (21) is arranged such

   - that the dielectric body (21) is located at the same level as a dipole square (13, 17) or as a radiating element arrangement which is similar to a dipole square and, in this case, is arranged within the dipole square (13, 17) or within the radiating element arrangement which is similar to a dipole square, and/or

   - that the dielectric body (21) is arranged above a dipole radiating element and/or above a cruciform radiating element (15) or patch radiating element (17), and is thus arranged further away from the reflector (11) than these radiating elements,

   c) the entire surface area of the dielectric body (21) or at least the size of the surface area of the dielectric body (21) which is produced by a right-angle projection onto the plane of the reflector (11), is larger than the square of the linear distance which is obtained from the distance between the plane of the reflector (11) and

   - the dielectric body (21), or

   - from the distance between the plane of the reflector (11) and a centre plane which runs through the dielectric body (21) or

   - from the distance between the plane of the reflector (11) and the outer boundary surface, facing away from the reflector plane (11) of the dielectric body (21).
4. Antenna according to the precharacterizing clause of Claim 1
   characterized by the following further features:

   - at least one dielectric body (21) which does not form the protective shroud is provided, and

   - at least part of the dielectric body (21) extends above parts of the radiating element arrangements (4a, 13; 4b, 15) at a distance in front of the reflector (11),

   - the dielectric body (21) extends parallel to the reflector (11), and

   - when viewed in a vertical plan view of the reflector, the dielectric body (21) has a flat extent which is greater than the flat extent, which results parallel to the plane of the reflector (11), of possible spacers, feet or other attachment elements which are part of the dielectric body (21) or are connected to it and run toward the reflector (11).
5. Antenna according to at least one of Claims 1 to 4, characterized in that, when viewed in a projection at right angles to the reflector (11), the at least one dielectric body (21) is smaller than the reflector (11) which is located underneath it.
6. Antenna according to at least one of Claims 1 to 4, characterized in that, when viewed in a projection at right angles to the reflector (11), the at least one dielectric body (21) is is of precisely the same size as the reflector (11) which is located underneath it.
7. Antenna according to one of Claims 1 to 6, characterized in that the dielectric body (21) is mechanically attached to the radiating elements (4a, 13; 4b, 15).
8. Antenna according to one of Claims 1 to 7, characterized in that, in a plan view, the at least one dielectric body (21) is in the form of an n-sided polygon.
9. Antenna according to one of Claims 1 to 8, characterized in that the at least one dielectric body (21) is at least essentially in the form of a plate.
10. Antenna according to one of Claims 1 to 9, characterized in that the dielectric body (21), or at least parts of it, is or are symmetrical with respect to a predetermined radiating element (4a, 4b).
11. Antenna according to one of Claims 1 to 10, characterized in that the dielectric body (21) is arranged such that more than 50% of it is at a distance of less than λ/2 from the plane of the reflector (11) with respect to the higher frequency band or the mid-frequency band.
12. Antenna according to one of Claims 1 to 11, characterized in that at least the major parts of the dielectric body (21) extend in a region which is located above the radiating element arrangement for the highest frequency band.
13. Antenna according to at least one of Claims 1 to 12, characterized in that the dielectric body (21) is composed of plastic, of polystyrene, of ABS or of glass fibre reinforced plastic.
14. Antenna according to one of Claims 1 to 13, characterized in that the material for the dielectric body (21) is chosen such that it has a low dielectric loss factor, preferably in the order of magnitude of 10³ or less, and in particular less than 10^-4 and especially 10^-5.
15. Antenna according to one of Claims 1 to 10, characterized in that the dielectric body (21) is used in particular for mobile radio antennas for the 900 MHz, the 1800 MHz and/or the 2000 MHz band.
16. Antenna according to one of Claims 1 to 15, characterized by the following further features:

    - more than 50% of the volume, and/or more than 50% of the weight, of the at least one dielectric body (21) is arranged in the region between the reflector (11) and the first distance or the first distance range of the radiating elements (4a, 13) for the lower frequency band, and

    - more than 50% of the volume and/or more than 50% of the weight of the at least one dielectric body (21) is arranged, as seen from the reflector (11), at more than the second distance or the second distance range for the radiating elements (4b, 15) which are provided for the upper frequency band.
17. Antenna according to one of Claims 1 to 16, characterized by the following further features:

    - more than 70% of the volume, and/or more than 70% of the weight, of the at least one dielectric body (21) is arranged in the region between the reflector (11) and the first distance or the first distance range of the radiating elements (4a, 13) for the lower frequency band, and

    - more than 70% of the volume and/or more than 70% of the weight of the at least one dielectric body (21) is arranged, as seen from the reflector (11), at more than the second distance or the second distance range for the radiating elements (4b, 15) which are provided for the upper frequency band.

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