WO2005060048A1 - Broadband antenna, in particular omnidirectional antenna - Google Patents

Abstract

The invention relates to a broadband antenna, in particular an omnidirectional antenna with the following characteristics: the emitter (15) projects upwards from a base plate or counterweight surface (1); said emitter (15) has a jacket surface extending away from the base plate (1); the base plate (1) is equipped with a cavity (3), in the vicinity of which the foot point (19) of the monopole emitter (15) is electro-galvanically separated from the base plate or the counterweight surface (1); and the emitter (15) is supplied with energy by means of a serial or capacitive inner conductor line coupling.

Description

Broadband antenna, especially omnidirectional antenna

The invention relates to an antenna, in particular an omnidirectional antenna according to the preamble of claim 1.

Omnidirectional antennas are known, for example, as so-called indoor antennas, which are multi-band capable and preferably radiate in vertical polarization. They comprise a base plate on which crosswise, i.e. an onopole-shaped spotlight rises perpendicular to the base plate. The entire arrangement is usually covered by a protective housing (radome).

On the metallic or at least conductive base plate, which is generally circular in plan view, a recess is incorporated in the center or in the vicinity of the center, in which a plug element for a plug connection is anchored, usually a plug-shaped contact element. From the bottom, a coaxial cable can be connected as a second plug-in element, usually as a socket-shaped plug-in element. The outer conductor is contacted with the base plate. The inner conductor of the feed cable is electrically connected to the monopole-shaped radiator via the plug contact provided on the base plate connected, which rises above the base plate. In other words, the inner conductor is electrically galvanically separated from the base plate and thus from the outer conductor of a coaxial cable to be connected.

Omnidirectional antennas of this type can be designed such that they can radiate simultaneously in several frequency ranges, that is to say simultaneously in several frequency bands.

For example, the applicant has already produced and offered indoor omnidirectional antennas of this type which can, for example, radiate simultaneously in the following frequency ranges:

824 - 960 MHz 1425 - 1710 MHz 1710 - 1880 MHz 1850 - 1990 MHz 1920 - 2170 MHz

Also known are multiband capable antennas manufactured and sold by the applicant, which can be operated simultaneously in the following frequencies, for example:

876 - 890 MHz 890 - 960 MHz 1710 - 2170 MHz 2170 - 2500 MHz

A generic antenna is known for example from DE 37 09 163 C2 or also from US 4 972 196 become.

The antenna mentioned in the first place shows a rod-shaped antenna which is fed via an inner conductor with the interposition of a capacitor.

In the previous publication mentioned in the second place, a Planara antenna is described with a disk-shaped radiator element, which is fed capacitively in the middle.

The object of the present invention is to provide a comparatively very low-build Ultiband capable, i.e. to create a very broadband antenna, which can also be used as an omnidirectional antenna and which is simple in construction. The antenna should be able to be operated simultaneously in even larger fire widths.

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

It must be regarded as extremely surprising that a greatly increased bandwidth for simultaneous operation in different frequency ranges is possible by a very low-profile antenna only by feeding the antenna by means of a serial or capacitive line coupling at the base of the radiator.

This alone makes very wide bandwidths possible. The The antenna according to the invention can, for example, be operated simultaneously without problems in the 800 to 1000 MHz band, in the 1400 to 3500 MHz band but also, for example, in the 5000 to 6000 MHz band. Because of the serial (capacitive) line coupling, resonances may be present in the upper band.

The antenna according to the invention has a generic-specific serial or capacitive coupling. This is because, according to the invention, a first coupling element is provided for the inner conductor coupling, which extends away from the base or counterweight surface in an electrically-galvanically separated manner. This works together with a second line coupling element, which is electrically galvanically connected to the radiator or is part of the radiator. The first and the second line coupling element are electrically galvanically separated from one another, that is to say they are not electrically galvanically connected to one another, by means of which the serial or capacitive line coupling is effected. The two interacting coupling elements are on the one hand rod-shaped and on the other hand tubular, so that the two coupling elements can be plugged into one another.

This offers the essential advantage that the length design allows an optimal capacitive or serial coupling to be achieved. In addition, a corresponding holding and carrying function for the radiator can also be brought about by this design, in particular if an insulating dielectric is provided between the two interacting coupling elements, as a result of which the two coupling elements are held mechanically firmly against one another when the two coupling elements are electrically isolated are. The monopole-like antenna according to the invention preferably has a rotational symmetry or is preferably designed to be rotationally symmetrical at least in certain angular ranges, wherein it comprises at least one section which widens conically or conically in the longitudinal direction of the monopole-shaped antenna. The overall shape of the antenna can also be conical or conical.

For this reason, the antenna can in principle also be radially symmetrical or radiation-symmetrical, that is to say have a cross-sectional shape, so that the antenna can be made to coincide with a plane rotation by a certain angle about a central axis. This can apply, for example, to the radiator alone, or to the base plate, for example, or both.

Alternatively, the monopole-shaped or. monopole-like emitters can be cylindrical.

However, the monopole-shaped radiator of the antenna preferably has a shape which is divided into a first section which is flared conically away from the base plate and a subsequent cylindrical second section. In other words, the radiator according to the present invention is preferably formed from a combination of a cone-shaped or conical and a cylindrical radiator section. The conical part of the emitter mainly acts as a monopoly for the upper frequency bands. The cylindrical part of the radiator, on the other hand, works with the associated counterweight surface (base plate) rather for the lower frequencies. It is positive to note that this does not affect the cylinder the shaped part on the upper frequency bands.

The serial and / or capacitive line coupling, which therefore consists of a serial and / or capacitive inner conductor coupling, is preferably carried out via a first rod-shaped coupling part which is connected to the feed line (inner conductor of a coaxial conductor) and rises above the base plate in an isolated manner from the base plate. The second coupling part coupling therewith is connected to the radiator or is formed as part of the radiator. The second coupling part is preferably tubular. The coupling part can also be designed in the manner of a polygon or the like, that is to say, for example, with an n-polygonal cross section, in order to achieve an anti-rotation lock. Generally speaking, the cross-sectional shape can be designed such that it has at least one shape that deviates from the circular shape. As a result, the monopole-like radiator, formed from a combination of a conical surface and an adjoining cylinder section, with the inner tube section (which rises from the base of the radiator) can be placed directly on the first rod-shaped coupling part which connects to the power cable. Since the first and second coupling parts, that is to say the feed line and the monopole-shaped radiator, are electrically isolated in order to implement the serial line coupling, an insulating sleeve of the first coupling part is preferably placed on which the monopole-shaped radiator with its second coupling part is then placed can.

This also results in extremely simple installation, since the spotlight can be simply pushed on without any soldering can be mounted on the first coupling part connected to the feed line with the interposition of an insulating insulator above the base plate.

However, the insulator must not necessarily consist of, for example, a plastic material with a preselectable dielectric constant. Air can also be used as an insulator. It is only necessary to use a suitable centering device and / or spacer, which ensure that the mounted radiator cannot come into electrical-galvanic contact with the rod-shaped coupling part in question protruding from the base plate and / or the base or base plate itself.

Due to the serial supply, the spotlight height can also be minimized compared to the conventional solution. This also makes it possible to reduce the counterweight area (base plate), which is why a comparatively small size can be achieved.

The invention is explained in more detail below on the basis of exemplary embodiments. The following show in detail:

Figure la: a schematic plan view of the antenna according to the invention;

Figure 1b: a bottom view of the antenna according to the invention;

FIG. 2: a schematic vertical cross section through the axial center of the antenna according to the invention; FIG. 3: a schematic perspective illustration of a rod-shaped coupling part rising from the base plate 1 and which is electrically connected to the feed line;

Figure 4 is a schematic perspective view of a first embodiment of a radiator;

Figure 5: an axial cross-sectional view through a further modified radiator shape;

Figure 6: a modified conical or truncated cone-shaped radiator shape in axial cross section;

FIG. 7: an axial cross section through the antenna according to the invention in a first attached inner hood; and

Figure 8 is a corresponding cross-sectional view of Figure 7, in which an all-covering outer hood is placed on the inner hood.

A first exemplary embodiment of an antenna according to the invention with a radiator 15 is shown in FIG. 1 a in a schematic plan view, in FIG. 1 b in a schematic bottom view and in FIG. 2 in a vertical cross-sectional illustration running through the central axis. The antenna comprises a base, base or ground plate 1, which is circular or disk-shaped in the exemplary embodiment shown. This base, base or ground plate 1 can also have a completely different shape. For example, it can have a square, rectangular, oval, etc. shape, and thus generally also have n-polygonal or any other basic shapes and boundary lines. The plate 1 is essentially referred to below as the base plate 1. The base plate 1 also has the function of a counterweight surface.

In the middle of the base plate 1, a recess 3 is machined. In and below the recess 3, a plug element 5 is positioned and fastened, which in the exemplary embodiment shown is designed as a coaxial plug element 5 '. The outer conductor 7a of the plug element 5 is electrically galvanically connected to the base plate 1. The inner conductor 7a of the plug-in element 5 is passed through the recess 3 separately from the outer conductor 7b and is electrically galvanically connected to a first or feed-side coupling element 11 which extends above the base plate 1. This coupling element 11 is transverse to the base plate, i.e. vertical in the embodiment shown. It is rod-shaped and can preferably have a circular cross section.

A tubular insulator element 13 is placed on this coupling element 11. In the exemplary embodiment shown, this insulator element 13 has a length which corresponds to the axial length of the coupling element 11. In the lower end, the insulator element 13 is provided with a laterally projecting flange 13a which, in the embodiment shown exemplary embodiment is also circular or disc-shaped and stands in the region of the recess 3 on the base plate 1.

This insulator element 13 is also attached to the monopole-shaped radiator 15 shown in FIGS. 1 and 2.

The monopole-like radiator 15 has a first antenna section 15a and a second antenna section 15b. Starting from the base point 19, the first antenna section 15a is aligned in a conically or conically widening manner, ie with its widening cone section pointing away from the base plate 1. This conical or conical first radiator section 15a is followed by a second cylindrical radiator section 15b, the diameter of the conical radiator section corresponding to the diameter of the cylindrical radiator section at the transition from the first to the second radiator section. The radiator therefore has a lateral surface which extends around the longitudinal axis running transversely to the base plate. The radiator 15 is preferably designed to be rotationally symmetrical or partially rotationally symmetrical, or at least approximately or essentially radially symmetrical or radially symmetrical.

As can also be seen from the cross-sectional illustration according to FIG. 2, part of the radiator is an internally formed tubular coupling element 15c which has a free inside diameter which is the same or slightly larger than the outside diameter of the tubular insulator element 13. Thus, with this coupling section 15c the monopole-shaped radiator can be pushed onto the insulator element 13 until the lowest Contact surface 15 'of the radiator 15, that is to say the base point 19 of the radiator, rests on the insulator flange 13a of the insulator element 13 and is thereby electrically galvanically separated from the base plate 1.

The axial length of the coupling element 15c is generally longer than the axial length of the insulator element 13 and / or the length of the first feeder cable-side coupling element 11. The length of the hollow cylindrical insulator 13 is comparatively uncritical and can also be made significantly shorter. The insulator essentially serves only for the mechanical mounting of the radiator 15 and also contributes to the fact that no section of the radiator 15 and in particular not the coupling section 15c can electrically galvanically contact the coupling element 11 which is in electrical contact with the inner conductor.

The two electrically and galvanically separated first and second coupling elements 11 and 15c, which are arranged in parallel and in the illustrated exemplary embodiment even coaxially to one another, form a serial (capacitive) line coupling at the base point of the radiator 15, ie a serial or capacitive inner conductor coupling. Therefore, the length of the first and second coupling elements 11 and 15c should preferably be selected so that the desired optimal coupling can be realized for the different frequency ranges. For this reason, the coupling element 15c forming part of the radiator arrangement is generally selected to be longer than the length of the coupling element 11 on the feed cable side. The length of the coupling element 11 on the feeding side is preferably selected as a function of the upper frequency bands so that this length is lambda / 4 or nx lambda / 4 is, where n represents the odd integer numbers, namely nx = 1, 3, 5 .... The open end of the line coupling is thus (for the center frequency of the respective band) at the feed point 15 'via short circuit, ie as if galvanically connected. For the edge frequencies, the feed cable-side coupling element 11 is thus both capacitive and inductive. For the sequences in which the length of the coupling element 11 on the feed side is lambda / 2, there is a resonance, that is to say that the open end at the base point 15 'of the radiator 15 acts like an idling (high-resistance). For the lowest frequency band (in the exemplary embodiment shown and explained, the band from about 800 to 1000 MHz), the length of the coupling element 11 on the feed cable side is very small compared to Lambda / 4 (that is, 11 “Lambda / 4) and thus forms a series capacitance which is broadband Resistance adjustment at this frequency enables and is also decisive for the low design.

3 shows a schematic perspective illustration of the first rod-shaped electrically conductive coupling element 11 with the radiator 15 removed, the coupling element in the region of the recess 3 with the coaxial plug element located on the underside of the base plate 1, i.e. is connected in an electrically conductive manner in the inner conductor plug there.

As can be seen from the schematic perspective illustration according to FIG. 3, the tubular insulator element 13, which preferably consists of plastic and has a favorable value for the dielectric constant, is merely plugged onto this first coupling element 11. Then, as stated, the radiator can then 15 with its second inner tubular element 15c.

The radiator 15 alone is shown in perspective view with the aid of FIG. 4, which is divided into a conical or conical radiator section 15a and a cylindrical radiator section 15b.

5 shows a modified cross-sectional view of a modified exemplary embodiment for a radiator which only consists of a conical or conical radiator 15. This can be a frustoconical shape.

According to the cross-sectional representation according to FIG. 6, it is shown that here only a cylindrical or pot-shaped monopole-like radiator is used as the radiator 15, which does not comprise a conical section. In this case, the coupling element 15c is connected to the outer jacket of the cylindrical radiator (15) by means of a radial connection or base section (15d).

Both in the exemplary embodiment according to FIG. 5 and also in FIG. 6, the section of the coupling section 15c, which forms part of the radiator arrangement and is centrally located, is shown in hollow cylindrical form, which is then plugged onto the first coupling element 11, preferably with the interposition of a hollow cylindrical insulator.

A small omnidirectional antenna can be realized with a radiator according to FIG can be operated in low frequency ranges. With a radiator according to FIG. 6, that is to say a radiator which is only in the shape of a truncated cone or truncated cone, a small-scale antenna is realized which can be operated above all in high frequency bands. However, an antenna type with a radiator according to FIGS. 1 and 2 is preferably implemented, the bandwidth of which includes both lower and high and very high frequency ranges and bands.

Not only can a very broadband antenna be realized with the antenna type described, but above all the serial feed can also minimize the radiator height and in turn also make the counterweight area (base plate) smaller. Thus, the antennas described have the advantage that they are wider than conventional antennas in a smaller size and can be manufactured and assembled even more easily, since in principle only the respective radiator with its integrated coupling element 15c onto the first one electrically connected to the feed line Coupling element 11 must be pushed on.

Basically, an isolator element 13 can be dispensed with, provided that only the monopole-shaped radiator with its coupling element 15c can be arranged electrically isolated from the first coupling element 11. For this purpose, it may be sufficient if the radiator is held and fixed only in the region of its base point on a disk-shaped or plate-shaped insulator element, so that the two coupling elements 11 and 15c do not make electrical contact.

Deviating from the exemplary embodiments shown the plug element 5 does not necessarily consist of a socket (for example an N socket). It is also possible to use a permanently connected cable, ie in particular to position the inner conductor of a coaxial cable accordingly in such a way that it serves as a feed-side coupling element 11 in accordance with the drawings. Therefore, the chosen term "" feed-side coupling element 11 "can also be understood to mean an embodiment in which the coupling element 11 represents the end of a corresponding feed conductor (preferably the end of the inner conductor of a corresponding coaxial feed line cable).

Finally, in a further modification it can also be provided that the feeder-side coupling element 11, the insulation 13 surrounding the coupling element 11 and preferably also the plug element 5 including the inner conductor 7a are made available and used as a prefabricated, jointly manageable unit a corresponding hole is inserted in the base plate 1 and mechanically anchored, in order then only to place the radiator 15 with its radiator-side coupling element 15c.

As can be seen from the cross-sectional view according to FIGS. 7 and 8, the reflector has recessed impressions or so-called mounting points 31 at some points offset from the center, in each of which a bore 33 is made in order to correspondingly fasten the reflector on a support by screwing in screws to be able to attach.

The entire antenna arrangement is ultimately a Inner hood 35 held and fixed. The inner hood 35 has latching or clip elements 37 which are offset in the circumferential direction on the reflector side and can be inserted into corresponding punched-out areas or openings in the reflector 1. In the snapped-in state, the latching elements 37 then snap in the punched-outs in the reflector, so that the antenna and the inner hood 37 are securely held in place without further assembly measures.

The inner hood 35 is designed in such a way that it has a central holding section 37a which engages downward into the cup-shaped radiator element and which secures the radiator in the plugged-in position with its reflector-side end face 37b. The end face 37b of the inner hood can touch the upper end face of the radiator-side coupling element 15c which faces it. By means of this inner hood, the radiator 15 is thus secured and fixed against axial slipping out and against radial tilting.

Finally, a so-called outer hood 41 can cover everything, the outer hood also having internal locking or clip elements 37, e.g. at a step on the inner hood can snap into openings made there and / or into openings in the reflector, namely by inserting corresponding latching or clip elements through the opening and snapping behind the corresponding material sections of the inner hood and / or the reflector. The outer hood is designed so that everything including, the reflector is covered and thereby covered.

The inner and outer hoods 35, 41 are made of one Made of material that is permeable to electromagnetic radiation especially in the frequency range to be transmitted.

Finally, it is noted that the different embodiments of the radiator 15 do not necessarily have to be made of conductive metal at home, but that it can also be formed from other non-conductive material, for example plastic. In this case, the radiator 15 should comprise or be provided with a suitable electrically conductive layer on its inner and / or outer surface or in some other way.

Claims

Broadband antenna, especially omnidirectional antenna 1.Wideband antenna, in particular omnidirectional antenna with the following features: - With a monopole-shaped radiator (15), the radiator (15) rises above a base plate or counterweight surface (1), - The radiator (15) has a lateral surface that is extends from the base plate (1), in the base plate (1) there is a recess (3), in the area of which the base point (19) of the monopole-shaped radiator (15) is arranged electrically isolated from the base plate or the counterweight surface (1) the radiator (15) is fed by means of a serial or capacitive inner conductor line coupling, characterized by the following further features - the inner conductor coupling comprises a first coupling element (11) and a second coupling element (15c), a coupling element (11) is rod-shaped and the further coupling element (15c) is tubular, the rod-shaped coupling element (15c) in the tubular coupling element nt (11) is inserted or pushed in, the one coupling element (11) extends transversely and preferably perpendicular to the base plate or counterweight surface (1) and is electrically connected in an arrangement that is electrically-galvanically separated from the base plate or counterweight surface (1) to a feed line or contactable, the other coupling element (15c) is electrically-galvanically connected to the radiator (15) or is part of the radiator (15), and the two coupling elements (11, 15c), which are not galvanically interconnected, form a serial or capacitive line coupling. 2. Broadband antenna according to claim 1, characterized in that the one coupling element (11) is electrically connected to a feed line and that the other coupling element (15c) is connected to the radiator (15) or is part of the radiator (15). 3. Antenna according to claim 1 or 2, characterized in that a tubular insulator element (13) is arranged between the first coupling element (11) and the second coupling element (15c). 4. Antenna according to one of claims 1 to 3, characterized in that the isolator element (13) has a radially projecting stop, flange or flange section (13a) to the area of the base point of the radiator (15), via which the isolator element (13) is supported or held relative to the base plate (1). 5. Antenna according to claim 4, characterized in that the radiator (15) rests with its base (19) on the flange (13a). 6. Antenna according to one of claims 1 to 5, characterized in that the first coupling element (11) is part of a feed line, in particular is formed from the inner conductor of a coaxial feed line. 7. Antenna according to claim 6, characterized in that the first coupling element (11) is formed from the inner conductor of a coaxial feed line. 8. Antenna according to one of claims 1 to 7, characterized in that the antenna has or consists of at least one cylindrical radiator section (15b). 9. Antenna according to one of claims 1 to 8, characterized in that the radiator (15) at least in two Is divided into sections and has a first radiator section (15a) which widens conically away from the base plate and merges into a cylindrical radiator section (15b) on its side remote from the base plate or counterweight surface (1). 10. Antenna according to one of claims 1 to 9, characterized in that the coupling element (15c) belonging to the radiator (15) on its side facing the base plate (1) facing the cone-shaped or truncated cone-shaped radiator or radiator section (15 , 15a) or by interposing a connecting section which preferably runs parallel to the base plate (1) (15d) is connected to the remaining jacket section of the radiator (15). 11. Antenna according to one of claims 1 to 10, characterized in that the first coupling element (11) and the isolator element (13) is a unit which can be handled in a uniform manner, in particular in that the isolator (13) is made on the first coupling element (11) a sprayed-on plastic or in the sprayed-on dielectric. 12. Antenna according to claim 11, characterized in that the first coupling element (11) with the insulator element (13) thereon and a plug element (5, 5 ') which can be anchored to the base plate as a unit which can be handled uniformly on a base plate (1). is attached. 13. Antenna according to one of claims 1 to 12, characterized in that the axial length of the first coupling element (11) Lambda / 4 ± <40% and preferably ± <20% thereof, where lambda is the mean wavelength of the frequency band to be transmitted. 14. Antenna according to one of claims 1 to 13, characterized in that the axial length of the first coupling element (11) is nx lambda / 4 + <40% and preferably + <20% thereof, where n = 1, 3, 5. .. is. 15. Antenna according to one of claims 1 to 14, characterized in that for the lowest frequency of one of the plurality of frequency bands, the axial length of the first Coupling element (11) is dimensioned such that it is small compared to lambda / 4, lambda representing the center frequency of the frequency band in question. 16. Antenna according to one of claims 1 to 15, characterized in that the radiator (15) consists of electrically conductive material. 17. Antenna according to one of claims 1 to 16, characterized in that the radiator (15) consists of plastic, in particular a molded plastic part, which is provided with a conductive coating. 18. Antenna according to one of claims 1 to 17, characterized in that the radiator (15) is covered with a hood, via which the radiator (15) is secured against axial slipping and preferably against radial tilting. 19. Antenna according to claim 18, characterized in that the covering device comprises an inner hood (35) which can be fastened to the reflector (1), preferably by means of a clip and / or latching device. 20. Antenna according to claim 18 or 19, characterized in that the inner hood (35) comprises a central fixing section (37a) which projects into the interior of the cup-shaped radiator (15) and presses on the adjacent end face of the second coupling element (15c) and thereby secures the radiator (15) against axial displacement and / or radial tilting. 21. Antenna according to one of claims 18 to 20, characterized in that on the inner hood (35) an all-covering outer hood (41) can be placed, preferably via a clip and / or locking device on the inner hood and / or, on the reflector (1) can be anchored.