EP0679318B1 - Uhf-waveband radio-antenna assembly for vehicles - Google Patents

Description

The invention relates to a radio antenna arrangement for vehicles for radio connections with terrestrial radio stations in the frequency range of the decimeter wave range after The preamble of claim 1 and claim 10. Such a radio antenna arrangement can be used advantageously e.g. for the radio systems of mobile communication (Car phone in the D or E network or for trunked radio systems).

Such antennas are described in the unpublished publication WO-A1-9429926, which goes back to the applicant of the present invention and prior art Technology in the sense of Art. 54 (3) EPC. For a better understanding of the present

The invention is first to briefly explain this radio antenna arrangement according to this document with the problems on which it is based.
Such antennas are known from everyday radio practice and are usually rod-shaped antennas with the character of an electrical monopole or dipole and are either on the vehicle roof, on one of the fenders or, if no mounting hole is to be made in the vehicle body, in the upper area the vehicle rear window applied, the antenna element is then attached to the outside of the glass pane and is often fed capacitively through the glass pane. Such an antenna is known from the document USA-A-4 764 773 ......

Disadvantages of these known antenna forms result from the requirement of radio practice that, with given transmission power, the radiation density in vertical polarization does not drop below a minimum required value in any horizontal direction due to dips in the horizontal diagram. At the same time, the dimensions of the antenna elements should be as small as possible. The shapes of length λ / 4 or less are particularly desirable because of their small dimensions.

The characteristic of the horizontal diagrams sought for motor vehicle radio antennas with the most uniform possible radiation in all azimuthal spatial directions is in the Practice therefore only with electrically short antenna elements according to the prior art approximately achieved by rotationally symmetrical elements in the middle of the vehicle roof. Here, the vehicle roof forms an essentially flat partial surface of the body with horizontal alignment with central attachment of the antenna element, an environment, where due to their size, the rotational symmetry of the radiation largely can train undisturbed. With off-center on the roof, or with the antennas glued to the vehicle window or attached to the fender due to the radiation coupling with that in relation to the antenna in the vicinity rotationally asymmetrical vehicle body in combination with the inhomogeneities the body shape (edges) or the material (transition from sheet metal to window) undesirable and sometimes no longer tolerable deformations of the horizontal diagram, in particular radiation compensations, which have strong indentations in the horizontal diagram cause.

When attaching the antenna element in the area of the rear of the vehicle is often special the radiation in the solid angle area to the front is reduced inadmissibly. It also joins frequency becomes more pronounced. this leads to especially in the minima of horizontal radiation at a given radiation power often in transmission mode to undesirably low radiation densities at the receiving location, i.e. to undesirably large radio field attenuation. The limitation imposed by this coupling with regard to the possible mounting points is a crucial one in practice Disadvantage. From the vehicle manufacturer's point of view, however, are electrically advantageous mounting points, such as. the roof center, undesirable for various vehicle technical reasons, e.g. because of the required installation space for sunroofs.

A reduction in the coupling to the vehicle body can be achieved through special Antenna elements can be reached, the center of radiation of which is significantly distant from the Body is lying, which usually leads to very large body heights. This technique aims depends on generating small currents on the body surface to make the rotationally asymmetrical To keep the radiation proportion as small as possible. Very good levels of decoupling Of the body are often achieved in that antennas of length λ / 2 over a Feed line at a distance of several decimeters (often more than 50 cm) above the vehicle body be attached, resulting in a disadvantageously large overall height of the entire antenna arrangement results. When λ / 2 long antenna elements are attached to the vehicle body - be it on the conductive body panel or on the rear window is the rotationally asymmetrical Influence of the vehicle body mitigated that on the antenna element in the Near the body, i.e. at the feed point, only comparatively small currents flow. Such an antenna is known from published patent application OS 4007824.8.

Such antennas therefore necessarily have a length that is significantly greater than λ / 4, namely λ / 2 or longer, which in addition to the often insufficient Rotational symmetry of the radiation is also a serious disadvantage in practice, e.g. due to increased wind noise.

In particular, shorter, essentially vertically polarized monopole antenna elements A length of λ / 4 or less carry strong currents at the feed point and are in consideration on their radiation diagram with regard to their structure on an electrically conductive Body part area instructed, which in all azimuthal directions over a distance of at least two wavelengths is largely flat and oriented horizontally. Is this Condition not met because the antenna element e.g. near a crease line of the Body, so near the edge of a partial area is attached where this partial area the vehicle body with a different partial surface with different inclination collides, then there is the undesirable rotational asymmetry described Radiation. Similar relationships arise, for example, when the antenna element in the Proximity of the boundary line of two partial surfaces made of different materials, such as Body panel and window glass - is attached.

Even a uniformly curved conductive body surface e.g. in the rear area as Mounting surface leads to rotationally asymmetrical radiation properties because that Partial area surrounding the antenna element only in a too small area as a flat partial area with regard to the radiation and this sub-area usually acts in relation to the horizontal is inclined. In all of these cases the azimuthal omnidirectional characteristic of the antenna element significantly disturbed by the surrounding vehicle body.

A preferred mounting point for antenna elements in terms of vehicle technology is exemplary in the middle of the vehicle on the roof of the vehicle near the rear roof edge or at the top of the rear window pane. In both cases that is Antenna element mounted on a partial surface of the body in such a way that the rotational symmetry the radiation from the vehicle body is disturbed.

In the radio antenna arrangement according to the above-mentioned older invention by the applicant these difficulties are avoided by replacing a single antenna with a a first antenna element and one or more further antenna elements existing group antenna is used. This group antenna is with their each Character of an electrical monopoly having antenna elements on one and the same Vehicle window pane attached. The disturbances caused by the surrounding Parts of the vehicle body are eliminated by designing the group antenna in such a way that such amount and phase relationships between the currents on the individual antenna elements adjust that by the material and the shape of the Group antenna surrounding vehicle body parts caused interference of the azimuthal Omnidirectional characteristics are largely balanced, with the clear distance between two adjacent antenna elements is chosen smaller than a free space wavelength.

The aforementioned older invention is limited to antenna elements that are mounted on a motor vehicle window, e.g. B. a motor vehicle rear window are attached. This represents one

Limitation on the location of the radio antenna arrangement, the frequent is felt to be constricting.

It is known per se, a single antenna element on the body of a vehicle to attach, as already mentioned above with regard to the attachment in the middle of the vehicle roof or has been carried out in the area of the rear of the vehicle. Furthermore, it is also from the Publication "Diversity Antennas for Space and Mobile Stations in Land Mobile Communication Systems ", IEICE Transactions E74 (1991) October, No.10, Tokyo, JP, in particular Fig. 7 and the associated description are known, several antennas on the roof of a vehicle to attach, but it is not a group antenna from several antenna elements but is a group of antennas designed for space diversity application is trained.

The object of the invention is therefore to provide a radio antenna arrangement in which, despite the existing radiation coupling to the vehicle body, the lowest flat radiation density occurring in the horizontal diagram is as large as possible.

This object is solved by the features of claim 1 with a generic radio antenna arrangement.

The invention is therefore based on the idea of a given vehicle body and at a given installation location, the disruptive influence of the vehicle body on the Radiation with the aid of a group antenna arrangement designed for this vehicle body to reduce or avoid. By solving the problem according to the invention a radiation characteristic is designed in such a way that the roundness of the azimuth diagram is also in the best possible way. In the present invention, the Group antenna adapted to the vehicle body designed in such a way that by superimposition which is generated by the usually strongly structured vehicle body and the electromagnetic radiation generated by the antenna elements of the group desired radiation properties of the arrangement of vehicle and antenna elements results.

In the technique according to the invention it is also necessary to generate the appropriate amplitudes and Phase relationships of the antenna currents possible, in addition to one fed Antenna element to use further fed and / or radiation-excited antenna elements. The clear distance between adjacent antenna elements should not increase be chosen large. In many cases you get at intervals of about a quarter wavelength favorable conditions. Distances greater than one wavelength are due to the jitter of the directional diagrams unfavorable.

The feeding of antenna elements can either be done in a simple manner common network with defined phase and amplitude relationships of the Antenna currents occur or the excitation of the antenna elements can be done with tuning the radiator geometry, through reactive resistance loading and through the choice of distance by radiation, so that a group antenna with only one fed Antenna element can be realized if all other antenna elements are excited by radiation are. It is essential here that the adjustment of the phase and amplitude relationships forces the inclusion of the shape of the vehicle body.

The operation of the invention can be exemplified by three antenna elements, the azimuthal individual diagrams shown in FIGS. 14a to 14c can be illustrated. Due to the influence of the vehicle body, the individual diagrams are in contrast to the diagram of the group antenna in Fig. 14d strongly dependent on the direction.

The advantages that can be achieved with the invention can be realized for motor vehicles, in particular at frequencies above about 600 MHz, and above all consist in the possibility of enabling short and optically inconspicuous antennas at vehicle mounting points that are particularly favorable in terms of vehicle technology, that is to say optically with a high performance of the antenna system and to be able to implement an extremely attractive solution from a vehicle-specific point of view.

In the meter wave range, in which the vehicle dimensions of the cars are of the order of magnitude fewer wavelengths, the less the fine structure of the vehicle shape is closer Surrounding the mounting point of the antenna, rather the overall shape of the vehicle of essential influence on the radiation characteristics of a radio antenna. in the In contrast to this, the near range determining the radiation properties is an im Decimeter wave range of much smaller radio antenna element by an order of magnitude smaller, so that the fine structure of the vehicle body and its nature the radiation properties in the immediate vicinity of the antenna element significantly determined. This effect is more pronounced the higher the frequency.

Due to the smallness of the wavelength in the decimeter wave range, the invention is Attaching several interconnected antenna elements to solve the Object of the invention in a relatively narrowly limited, compared to the vehicle dimensions small area possible.

• im Mittel eine erhöhte Bündelung der Strahlung in vertikaler Richtung zu gunsten kleiner Elevationswinkel entsteht und
• dabei möglichst geringe Einzüge des horizontalen Strahlungsdiagramms auftreten, wodurch bewirkt wird, daß die geringste, im gesamten Horizontalbereich auftretende Flachstrahlungsdichte so groß wie möglich ist.

The use of a plurality of antenna elements, given the positioning of the group antenna on the vehicle, which is suitable from a vehicle-specific point of view, allows a specific generation of current distributions on the antenna elements of the group antenna according to amount and phase in such a way that, taking into account the radiation coupling with this vehicle body

• on average there is an increased concentration of radiation in the vertical direction in favor of small elevation angles and
• the smallest possible indentation of the horizontal radiation diagram occurs, which has the effect that the lowest flat radiation density occurring in the entire horizontal region is as large as possible.

The measures taken according to the invention make the radiation, which is undesirable per se the vehicle body excited by radiation coupling is not prevented. By means of suitable current distributions on the antenna elements of the group antenna Rather, the amount and phase are superimposed on a wave field by the large number of radiators, which in total gives radiation properties according to the object of the invention.

Embodiments of the invention are illustrated in the drawings 1 to 6 and 10 to 14 and will be described in more detail below.

Fig. 1:

Erfindungsgemäße Gruppenantenne an der hinteren Dachkante mit einem weiteren Antennenelement 8 und einem Netzwerk 4 unterhalb des Daches mit konzentrierten Blindelementen.

Fig.2:

Erfindungsgemäße Gruppenantenne an der hinteren Dachkante mit einem weiteren Antennenelement 8 und einem Netzwerk 4 auf dem Dach, das mit Streifenleitungsschaltungen realisiert ist.

Fig.3a:

Erfindungsgemäße Gruppenantenne an der hinteren Dachkante mit einem weiteren Antennenelement 8, das mit dem ersten Antennenelement 3 nur strahlungserregt und mit einem Blindelement geeignet beschaltet ist.

Fig.3b:

Erfindungsgemäße Gruppenantenne an der hinteren Dachkante mit einem weiteren Antennenelement 8, das mit dem ersten Antennenelement nur strahlungserregt und dessen Länge geeignet gewählt ist.

Fig.4:

Erfindungsgemäße Gruppenantenne an der hinteren Dachkante mit einem weiteren Antennenelement 8 und Antennenelementen jeweils mit Dachkapazitäten und Verlängerungsspulen unter einem Radom und mit einer Verlegung des Verbindungskabel entlang des Dachs und im Bereich der Scheibenklebung nach innen.

Fig.5:

Erfindungsgemäße Gruppenantenne im Bereich der hinteren Dachkante mit einem ersten Antennenelement 3 knapp oberhalb der Scheibe und einem weiteren strahlungserregten Antennenelement 8 auf dem Dach.

Fig.6:

Erfindungsgemäße Gruppenantenne im Bereich der hinteren Dachkante und dem oberen Bereich der Heckscheibe mit einem ersten Antennenelement 3 auf der Scheibe und zwei weiteren nur strahlungserregten Antennenelement 8 auf der Metallfläche oberhalb der Scheibe und auf dem Dach.

Fig.7:

Bekannte Gruppenantenne auf der Fahrzeugscheibe 1 mit einem weiteren Antennenelement 8 und einem Netzwerk 4 mit Streifenleitungsschaltungen.

Fig.8:

Bekannte Gruppenantenne auf der Fahrzeugscheibe ähnlich Fig.7, jedoch mit einem aufgedruckten Schirm 29 auf der Scheibe zur Bildung eines Gegengewichts und zur Reduktion der HF-Strahlung im Fahrgastraum.

Fig.9:

Bekannte Gruppenantenne auf der Fahrzeugscheibe u.a. mit radial und ringförmig angebrachten drahtförmigen Leitern auf der Scheibe zur Ausbildung einer transparenten größeren Massefläche

Fig.10a:

Erfindungsgemäße Gruppenantenne auf der Fahrzeugscheibe mit einem von der Scheibe näherungsweise normal wegstehenden ersten Antennenelement 3 und drei in der Scheibenebene angeordneten weiteren Antennenelementen 8: Schnittansicht.

Fig.10b:

Erfindungsgemäße Gruppenantenne wie Fig.10a, aber in einer perspektivischen Darstellung.

Fig. 11a:

Schnittdarstellung einer erfindungsgemäße Gruppenantenne auf der Fahrzeugscheibe mit einem in der Scheibenebene liegenden ersten Antennenelement 3 und zwei in der Scheibenebene angeordneten weiteren Antennenelementen 8.

Fig. 11b:

Erfindungsgemäße Gruppenantenne wie Fig. 11a, aber in einer perspektivischen Darstellung.

Fig.12:

Erfindungsgemäße Gruppenantenne, vollständig im Inneren des Fahrzeugs angebracht, und mit drahtförmigem ersten Antennenelement 3 und einem weiteren Antennenelement 8, jeweils mit Dachkapazität, und einer metallischen zur Scheibe hin offenen Kavität 31.

Fig.13:

Erfindungsgemäße Gruppenantenne, vollständig im Inneren des Fahrzeugs angebracht, und mit einem erstem Antennenelement 3 und einem weiteren Antennenelement 8, beide in der Scheibenebene angebracht, und mit einer metallischen Kavität 31.

Fig.14:

Gemessene Richtdiagramme mit den drei Antennenelementen und gemessenes Richtdiagramm der optimierten Gruppenantenne.

Show it:

Fig. 1:

Group antenna according to the invention on the rear roof edge with a further antenna element 8 and a network 4 below the roof with concentrated blind elements.

Fig. 2:

Group antenna according to the invention on the rear roof edge with a further antenna element 8 and a network 4 on the roof, which is implemented with stripline circuits.

Fig.3a:

Group antenna according to the invention on the rear roof edge with a further antenna element 8, which is only radiation-excited with the first antenna element 3 and suitably connected with a blind element.

Fig.3b:

Group antenna according to the invention on the rear roof edge with a further antenna element 8, which only excites radiation with the first antenna element and whose length is suitably selected.

Fig. 4:

Group antenna according to the invention on the rear roof edge with a further antenna element 8 and antenna elements each with roof capacities and extension coils under a radome and with a laying of the connecting cable along the roof and in the area of the pane adhesive inwards.

Fig. 5:

Group antenna according to the invention in the area of the rear roof edge with a first antenna element 3 just above the pane and a further radiation-excited antenna element 8 on the roof.

Fig. 6:

Group antenna according to the invention in the area of the rear roof edge and the upper area of the rear window with a first antenna element 3 on the window and two further only radiation-excited antenna element 8 on the metal surface above the window and on the roof.

Fig. 7:

Known group antenna on the vehicle window 1 with a further antenna element 8 and a network 4 with stripline circuits.

Fig. 8:

Known group antenna on the vehicle window similar to Figure 7, but with a screen 29 printed on the window to form a counterweight and to reduce the RF radiation in the passenger compartment.

Fig. 9:

Known group antenna on the vehicle window, inter alia, with radially and annularly attached wire-shaped conductors on the window to form a transparent, larger ground plane

Fig.10a:

Group antenna according to the invention on the vehicle window with a first antenna element 3, which projects approximately normally away from the window, and three further antenna elements 8 arranged in the window plane: sectional view.

Fig.10b:

Group antenna according to the invention as in FIG. 10a, but in a perspective view.

11a:

Sectional view of a group antenna according to the invention on the vehicle window with a first antenna element 3 lying in the window plane and two further antenna elements 8 arranged in the window plane.

11b:

Group antenna according to the invention as in FIG. 11a, but in a perspective view.

Fig. 12:

Group antenna according to the invention, fitted completely inside the vehicle, and having a wire-shaped first antenna element 3 and a further antenna element 8, each with roof capacitance, and a metallic cavity 31 that is open toward the pane.

Fig. 13:

Group antenna according to the invention, mounted completely inside the vehicle, and with a first antenna element 3 and a further antenna element 8, both mounted in the pane plane, and with a metallic cavity 31.

Fig. 14:

Measured directional diagrams with the three antenna elements and measured directional diagram of the optimized group antenna.

1 shows the basic structure of a group antenna according to the invention with a first antenna element 3, which is on the roof of the vehicle near the rear Roof edge 10 is mounted in the center of the vehicle and fed through an opening in the roof. A further antenna element 8 is attached at a distance 9 in the direction of the rear roof edge, which is also fed through an opening in the roof. Both Antenna elements are because of their small relative distance from each other and with the Body coupled to radiation. The antenna connection point 6 is in the example of FIG Inside the vehicle, a network 4 conducts the high-frequency signal from the antenna connection point 6 to the two antenna elements. Network 4 divides the Power over a low-loss feed network, which in the example of Fig. 1 concentrated low-loss dummy elements is constructed, the network 4 in addition to the radiation coupling through the field another high-frequency coupling path between forms the two antenna elements.

Each of the two antenna elements 3 and 8, used alone as a radio antenna, in the absence of the respective other antenna element, an inadequate one Distribution of high-frequency power in the horizontal plane, because of the Near the rear roof edge 10, there is a strong inhomogeneity of the environment. In the homogeneous, first partial area with regard to the material and the position in the room 11 extends from the rear roof edge 10 to the front and to the side, each up to the other edges of the roof area.

However, the homogeneity of this partial area is not over for antennas according to the invention such large areas required. What is important for the electrical function is essentially the immediate vicinity around the antenna elements in which the radio field is formed. In practice, this range is shown to be approximately two wavelengths in size.

Therefore, in FIG. 1 the distance between the first antenna element 3 is less than approximately two Wavelengths to the rear roof edge, so is the homogeneity of the partial surface 11 for the invention Antennas not sufficient and the radiation characteristics accordingly unsatisfactory. The sheet metal surface which bends downwards at an angle 26 represents an adjacent one represents further partial area 12. Both partial areas have in common the boundary line 13 which is shown in this example is also the rear roof edge 10. In this example the inhomogeneity this area is further reinforced by the fact that the sloping downward Body part is short and merges into the rear window, which is made of non-high-frequency conductive Material exists.

The circuit arrangement in the network 4 and the resulting impedance coupling of the first antenna element 3 with the further or the further antenna elements 8 can also be from a stripline circuit (Fig.2) or from a combination of stripline circuits and concentrated dummy elements. At a Realization of the network 4 with strip lines are then state of the art accordingly printed lines of appropriate wave resistances are used. Such Circuits enable the targeted setting in a particularly advantageous and cost-effective manner the required currents on the antenna elements 3 and 8 according to amount and phase and the adaptation to the characteristic impedance of the feed cable. Another and special great advantage of the stripline circuit is the precisely reproducible Arrangement specifically for large-scale production of such inventive Antenna arrangements is suitable.

In each of the cases discussed, the antenna connection point 6 results in the resulting radiation characteristic including the radiation coupling of the Antenna elements and their supply and the radiation coupling with the body of the vehicle. The network 4 is accordingly designed so that a defined and Fixed phase and amplitude relationship of the base feed currents of the antenna elements 3 or 8 is present. About this defined phase and amplitude relationship the horizontal diagram of the antenna arrangement according to the invention in the desired advantageous type and compared to the radiation characteristics of each Single antennas improved.

The example in FIG. 2 shows a similar arrangement with regard to the antenna elements. in the In contrast to Fig. List here the network 4 attached to the top of the roof with the advantage that only a single breakthrough through the roof skin is required. This arrangement lends itself particularly well to networks 4 that use stripline circuits because due to their construction, they are very flat and therefore flat on the outside of the body can be attached. Fig.2 shows a vertical only for ease of illustration standing stripline circuit.

In the arrangement according to FIG. 1, there are accordingly so many openings through the sheet metal Bodywork required, such as antenna elements 3 and 8 fed via the network are, which is certainly a disadvantage from a vehicle-specific point of view. On on the other hand, the installation in the interior is cheaper than the functionality of the network is only ensured under the climatic conditions of the interior must become.

In a particularly simple embodiment of a group antenna according to the invention The network 4 can also be designed in accordance with FIG. 3a so that the coupling of the first antenna element 3 and of the further antenna element (s) 8 exclusively via the field coupling between the emitters, that is, by the Radiation coupling of the antenna elements 3 and 8. In this case there is only the first antenna element 3 with the antenna connection point 6 on the network 4 via a high-frequency line connected. The radiation characteristic of the overall arrangement, however, will essentially through the entirety of the radiation-coupled antenna elements 3 and 8 including the effect of the vehicle body.

To in each of the further antenna elements 8 with a pure radiation coupling to achieve the optimal horizontal diagram of the required current according to amount and phase, e.g. the length of the further antenna element 8 is chosen appropriately. For a good Radiation coupling requires resonance lengths. An antenna element 8 advantageously chosen to be about 1/4 wavelength long if it is at its lower end high-frequency conductive is connected to the body. With the exact length around the λ / 4 resonance then the phase position is adjusted appropriately. Shorter or longer others Antenna elements 8 can also be used when the base of the element is connected with a corresponding dummy element (Fig.3a). With antenna elements, which are shorter than λ / 4, as is known an inductance at the base is required, With longer antenna elements a capacitance is necessary.

In this way, with antennas according to the invention, by at least one further Antenna element 8, which is coupled to the first antenna element 3, a considerable Improvement of the radiation characteristics can be effected in the horizontal. The horizontal Directional characteristic of each of the antenna elements 3 and 8 therefore also has in inventive Group antennas undesirable deviations from the ideal radiation pattern on. In addition, the individual diagrams of the individual antenna elements not the same with each other, because of the different mounting points the shading due to the body and the coupling with it are not the same. The Radiation coupling between the antenna elements depends essentially on their length and their distance from each other.

The desired improvement in the radiation characteristic can be achieved according to the invention Antennas therefore also through exclusive radiation coupling between the first antenna element 3 and other antenna elements 8 can be achieved. The necessary A high degree of coupling, however, requires a distance 9 that is not too large the individual spotlights. A value of approximately can be used as the upper limit for this distance 9 λ / 4 are applied, with a suitable choice of the length of the antenna element 8 or the antenna elements 8 and / or by wiring with a blind element at the base the current on the antenna element 8 or on the antenna elements 8 according to the state the technology can be adjusted. Figure 3a shows an example of this. The network 4 serves in such cases then only for feeding the first antenna element 3, e.g. for adaptation to the characteristic impedance of the connecting cable 28 to the radio, which is at the antenna connection point 6 is connected.

Here, as is generally the case with radio systems, at the antenna connection point 6 Group antenna for the respective frequency band a sufficiently low standing wave ratio required, as is known from RF interfaces of other radio systems.

Basically it turns out that when the antenna elements are supplied via the network and if the distances between the emitters are too large, the radiation directional diagram shows the tendency possess strong indents. In preferred antenna arrangements, therefore also in the interest of a simple design of the network 4, the maximum distance between two antenna elements chosen not larger than about a free space wavelength.

The phase and amplitude states required to achieve the object of the invention The electrical quantities on the antenna elements are therefore essentially of their shape and position to each other and the radiation coupling with the conductive Vehicle body dependent. There are a multitude of favorable arrangements for every vehicle of antenna groups according to the invention, each by specific for this Optimization of the network 4 result in advantageous radiation properties. The one for this The radiator shapes used can be freely selected within certain limits.

Instead of simple rod-shaped antenna elements, antenna elements can also be used a capacitive roof load and in the interest of further shortening e.g. can be connected with dummy elements, usually in the form of an extension coil are carried out (Fig. 4). Even with longer antenna elements with a Length between λ / 4 and λ / 2, the current assignments on the antenna elements can be suitable to be influenced. In the example in FIG. 4, a radio antenna arrangement according to the invention are the use of a roof capacity and an extension coil antenna elements minimized in length under a plastic radome 32 housed. FIG. 4 also shows a particularly advantageous supply for the antenna connection point 6 via the feed line, without a breakthrough through the roof membrane gets along. This is done using a very thin coaxial cable or a flexible triplate stripline circuit through the area of the adhesive bead of the rear window through to the outside and so sealed with the window adhesive.

Because of the increased losses of thin cables, one is in the sense of high efficiency corresponding section of the antenna arrangement according to the invention with a small cross section to run as short as possible. In the example in FIG. 4, this section is relative long because the radio antenna arrangement is arranged on the vehicle roof and therefore to bridge a comparatively long distance along the bent sheet metal part is. 5 shows an antenna arrangement according to the invention which is more advantageous in this respect, in which the first antenna element 3 on this inclined surface, which is consequently the first Partial surface 11 forms, and is attached approximately normal to it. The other radiator 8 is only coupled by the radiation field and sits on the further partial surface 12, which by the approximately horizontal surface of the roof is formed.

The first is in the example in FIG. 6 of a radio antenna arrangement according to the invention Antenna element 3 attached in the upper area of the rear window and capacitively in known Feeded through the disc through the network 4. The first face 11 forms the disc here, the inhomogeneity results at the transition to the sheet metal Body on the upper edge of the window. The sheet metal strip above is up to the disc to the roof edge, which is usually approximately flat but spatially in the extension of the Disk is arranged wide, so is a further partial surface 12b corresponding to this sheet metal strip available. The roof area then forms a further partial area 12a.

This arrangement and wide sheet metal strip would result between the further antenna element 8a on the roof then too great a distance, so that the radiation coupling may be too low. In such cases, it is recommended for the invention Radio antenna arrangements, a further antenna element 8b on the further partial area 12b, e.g. essentially normal to her to attach. This way approximately a halving of the distance between two antenna elements 8 with the advantage of a significantly increased coupling. The shading to the front, which at the presence of the first radiator 3 alone can be achieved by this chain of two further antenna elements 8 can be significantly reduced according to the invention.

Further embodiments of radio antenna arrangements according to the invention result, if all antenna elements are mounted on or in the vehicle window, such as this is shown in FIGS. 9 to 13.

The disc 1 is inclined at an angle 26 to the horizontal. This angle is at today's vehicles between about 10 degrees (sports cars) and about 80 degrees (station wagons).

At not too large angles 26, despite the inclination of the disc and also at normal to Disk surface-mounted antenna elements (examples of Figures 7 and 8), preferably radiated polarization vertically, since the essentially horizontally oriented Sheet metal surfaces of the vehicle, namely the roof and the trunk lid, the shaft result in essentially a vertical electrical field component towards the far field running. The alignment of the E vector is therefore not necessarily identical to that Location of the antenna elements in the room, but is due to the surface of the body co-determined.

However, the shadowing increases and the radiation distribution is impaired horizontally when the disc is steeper. This can be the case with the invention Antenna arrangements counteracted by a larger number of radiators become, because then the possibilities of chart formation become greater.

Particularly good radiation properties with one or two further antenna elements 8 In the sense of achieving the object of the invention, such vehicles achieve where the angle of inclination 26 of the window pane is not greater than the horizontal is about 60 degrees.

Basically, measurements show that it is all the more advantageous to use the radiators in the To be arranged near the upper edge of the window pane, the greater the angle of inclination 26 of the window pane 1.

7 shows a known antenna arrangement in which the first antenna element 3 and one or more further antenna elements 8 are attached to the vehicle window 1 are. The antenna elements are all essentially normal to the surface of the pane arranged and fed through the disc from below. The network 4 is inside attached to the disc. The inhomogeneity of the first partial surface 11, the disc surface is through its upper edge and the transition to the metallic body given. In the example shown, the connection between the antenna elements is made 3 or 8 and the network 4 via a hole through the glass. To avoid a Such an unfavorable hole is also a capacitive coupling the disc is possible, as in another antenna arrangement according to the invention Fig. 8 is shown.

8 shows a similar known antenna arrangement, in which the Network 4 is mounted on the outside of the disc. The coupling of the high frequency In this example, signals through the disk occur only at a single point and therefore particularly simple and advantageous capacitive, the antenna connection point 6 is through the inner Coupling surface and given by the surrounding mass. In this case, too capacitive connection can be included in the network 4 in a technologically cost-effective manner, if it is constructed as a stripline circuit.

Antenna arrangements as shown in Fig.7 have the disadvantage that part of the Field lines that begin on the antenna elements run through the interior of the vehicle and lead to undesirable high field strengths there. At the same time it is one increased inhomogeneity for the first partial surface 11 and increased asymmetry, which results in an increased shadowing of the radiation to the front.

For the design of the known group antenna is for each antenna element a time-invariant antenna counterweight is also advantageous. This can be as high-frequency conductive surface 29 formed on the window pane, as shown in Fig.8 become. In the interest of the transparency of this area, it is advantageous to use it as a radiation Structure, which consists of radially extending from the network 4, wire-shaped There is a ladder (Fig. 9). The network 4 itself is advantageous with a conductive Equipped outer surface, which is part of the antenna counterweight in the center of the group antenna forms for the antenna elements. The radiating conductors 20 are high-frequency connected to this conductive outer surface. These rays can pass through conductor 20 attached in a ring around the group antenna to a high-frequency conductor Mesh network can be supplemented (Fig. 9).

With radio antennas on the rear window of vehicles naturally occur in the immediate vicinity Proximity of the transmitting antenna to large field strengths which endanger people in the passenger compartment could. The formation of the antenna counterweight 29 as a high-frequency conductive Surface has a very advantageous shielding effect against electromagnetic fields, which otherwise push into the passenger compartment. The call for a defined Antenna counterweight can thus advantageously be combined with the requirement for a Field weakening of hazardous electromagnetic radiation.

There are often horizontally attached heating conductors on the rear window. Points equal DC potentials can be galvanically connected to each other without to influence the heating current flow. By introducing connecting landings The heating field can also be designed as a largely shielding surface for high frequencies and act as an expanded antenna counterweight. To high-frequency currents between the ground plane at the group antenna via the heating field without Influencing the heating currents is a DC-impermeable, frequency-selective Connection in the wire-shaped conductors advantageous.

Such frequency selective connections are also necessary if parts of the antenna counterweight as antenna parts for other radio services, which are also on the window pane are attached, are used. An example of this is given for antennas which e.g. act as an AM-FM antenna. As frequency-selective connecting elements mainly capacitive structures are used. It is also very advantageous a coplanar line structure of approximately λ / 4 length for the radio frequency.

10a and b show an antenna arrangement according to the invention, in which the first antenna element 3 is oriented essentially normal to the surface of the pane. The others Antenna elements 8 are arranged in the plane of the disk and e.g. printed on the inside. FIG. 10 a shows this arrangement as a section, FIG. 10 b shows a perspective view.

11a and b show an antenna arrangement according to the invention (Fig.11a as a section, 11b as a perspective view), in which all antenna elements in the plane of Disc surface are arranged. This arrangement then leads to satisfactory radiation characteristics, if the disc is steep and the antenna elements 3 and 8 are therefore oriented essentially vertically in space.

Further and particularly advantageous embodiments of antenna arrangements according to the invention Figures 12 and 13 show. The advantage of these arrangements results from the fact that no components of the radio antenna arrangement on the outside of the vehicle body are arranged. For this purpose, a metallic cavity 31 is used, which leads to the disk is open towards and for the antenna elements 3 and 8 as a ground plane and as the rear Shielding. The antenna elements 3 and 8 are in the example of Figure 12 in oriented essentially normal to the surface of the pane and normal to the rear of the cavity 31 and are fed by the network 4, which advantageously on the disk facing Back of the cavity 31 is attached. The distance from the back of the cavity In the interest of a low installation height, the pane should be chosen as low as possible.

Therefore, in such an antenna arrangement according to the invention, antenna elements are advantageous used with roof capacity and extension coil, with which the length the antenna elements can be made as small as possible. As the lower limit for the height of the cavity is a value of about 1/20 of the free space wavelength, since otherwise the transmission efficiency is known to be too low.

Fig. 13 shows a similar arrangement in which all antenna elements 3 and 8 in the Plane of the disc are arranged.

The effect achieved with the invention is shown impressively in Figures 14a to 14d forth. In the illustrated horizontal diagrams of the pictures 14a to 14c are the Radiation properties of three antenna elements on the rear window of a sedan in a triangular arrangement near the upper edge of the pane.

Each of the diagrams has strong intolerable indentations or shading areas. Although the antenna elements used are each rotationally symmetrical slim and normal elements mounted to the pane surface result from the coupling of radiation the non-roundness of the diagrams shown with the conductive vehicle body. By connecting to a suitable network 4, which the antenna elements feeds in the correct phase and amplitude and its characteristics through application mathematical optimization process specifically for those on the particular vehicle measured antenna elements have been calculated, this is shown in FIG. 14d Directional diagram reached, which has much smaller indents.

If a group antenna according to the invention is intended for several radio systems, e.g. the D network and the E network are designed equally, so the antenna elements be designed so that they are functional in both frequency ranges. Here the network 4 designed so that it is in the two frequency ranges, each for this ensures the required phase and amplitude conditions for the individual radiators, so the group antenna can be used in both frequency ranges. One more way consists of at least partially separate antenna elements for both frequency ranges to use.

To ensure the best possible connection of the signals in the network 4, there is a certain Metrological effort necessary to determine the antenna properties of the radiators Determine vehicle. This happens because each antenna element at a defined Interface a port 27 is assigned. With the help of modern network analyzers can determine the wave parameters of this antenna element network become. In addition, the excitations can occur when a wave comes in from a certain direction measured at the connection gates 27 according to amount and phase. With knowledge the properties of the radiator network and its excitation by the incident wave at the various connection gates 27 can be used with the help of modern computing systems suitable optimization strategies, an optimal network 4 can be designed for this.

For the transmission case, the radio antenna should always work according to the object of the invention. In the case of reception, however, due to the Rayleigh scattering of the waves received in the generally prefer antenna diversity operation. The network 4 can be designed in this way be that with the help of switching diodes different signal combinations of the Beam received individual signals are formed at the antenna connection point 6. With With the aid of an antenna diversity device, the switching diodes can be controlled in such a way that that the signal combination appears at the antenna connection point at any moment, which results in the best possible reception. The execution of the radio antenna as Group antenna thus offers the advantage of being usable simultaneously as a diversity antenna.

Claims (26)

1. A radio antenna arrangement for vehicles for radio connection to terrestrial radio stations in the microwave frequency range, especially above 600 MHz, with a first antenna element with the character of an electrical monopole or dipole with substantially vertical polarisation portion, which is disposed on a first partial surface of a vehicle body of in each case, substantially homogenous material, the azimuthal polydirectional characteristic of which is substantially disturbed by the surrounding vehicle body, wherein in addition to the first antenna element (3), at least one further antenna element (8) with monopolar or dipolar character is available and each further antenna element is disposed either on the first (11) or a further partial surface (12) and with regard to the antenna connection point (6) the antenna elements together form a group antenna, of which at least one is fed and the other, or others, is/are either fed or radiation-coupled and the group antenna is configured in such a way that suitable relationships are set between the currents on the individual antenna elements according to amount and phase and the internal clearance (9) between two adjacent antenna elements is selected to be smaller than a free space wavelength , wherein in the case of antenna elements orientated normal to a vehicle window pane, not all antenna elements are disposed on this window pane.
2. A radio antenna arrangement according to claim 1,
   characterised in that the dimensions of all antenna elements are such that they do not project above the vehicle bodywork by more than a vertical distance which is considerably smaller than half a free space wavelength.
3. A radio antenna arrangement according to claim 2,
   characterised in that the antenna element (3) and the further antenna element or elements (8) are disposed close to the border line or lines (13) of two or more adjoining first (11) and adjacent partial surfaces (12) of the vehicle bodywork (5).
4. A radio antenna arrangement according to claim 3,
   characterised in that the border line (13) is formed by one of the roof edges.
5. A radio antenna arrangement according to claim 4,
   characterised in that the first partial surface (11) is formed by the roof surface of the vehicle.
6. A radio antenna arrangement according to claim 5,
   characterised in that the first antenna element (3) and the other antenna element or elements (8) are all disposed on the same first partial surface (11) (Fig. 1, 2, 3a, 3b, 4).
7. A radio antenna arrangement according to claim 5,
   characterised in that the first antenna element (3) is disposed on the first partial surface (11) and the further antenna element (8) or at least one of the further antenna elements (8) is disposed on an adjacent partial surface (12) (Fig. 5).
8. A radio antenna arrangement according to one of claims 1 to 3, characterised in that a network (4) is available and the first (3) and at least one further antenna element (8) are fed by the network (4) and are connected at high-frequency to the antenna connection point (6) and that the network is configured so that the necessary currents are set according to amount and phase at the first antenna element (3) and on the further antenna elements (8) fed by the network (4) (Fig. 1, 2, 4).
9. A radio antenna arrangement according to one of claims 1 to 3, characterised in that only the first antenna element (3) is connected to the antenna connection point (6) via the network (4) and the further antenna elements (8) are radiation-coupled in such a way that the necessary currents are set according to amount and phase on the further antenna element or elements (8) by radiation coupling and by suitable selection of the length of the further antenna elements (8) and/or by suitable wiring in the base (Fig. 3a, 3b, 5, 6).
10. A radio antenna arrangement according to one of claims 8 or 9, characterised in that the first partial surface (11) is formed by the vehicle's rear pane (1) and that the first antenna element (3) and all further antenna elements (8) are disposed on this vehicle rear pane (1) (Fig, 7, 8, 9, 10a, 10b, 11a, 11b).
11. A radio antenna arrangement according to claim 10,
    characterised in that the network (4) is disposed on the inside of the vehicle pane (1) (Fig. 7).
12. A radio antenna arrangement according to claim 10,
    characterised in that the network (4) is disposed on the outside of the vehicle pane (1) (Fig. 8).
13. A radio antenna arrangement according to one of claims 10, 11 or 12, characterised in that an optically-transparent laminar screen (29), which is largely impermeable to the frequencies of the radio service, is coated or printed onto the surface of the pane, inside or outside, to reduce the electromagnetic fields in the vehicle interior (Fig. 8).
14. A radio antenna arrangement according to one of claims 10, 11 or 12, characterised in that the laminar screen (29), which is largely impermeable to the frequencies of the radio service, comprises radially and concentrically-printed conductors (20) (Fig. 9).
15. A radio antenna arrangement according to one of claims 13 or 14, characterised in that in addition to the structure of the laminar screen (29), other antenna structures (30) are disposed on the pane e.g. for disc antennae for other radio services and the laminar screen (29), which is largely impermeable to the frequencies of the radio service in the microwave range, also partially comprises these antenna structures (30) and these antenna structures (30) for the frequencies of the radio service in the microwave range of the radio antenna arrangement are selectively coupled, at high frequency and low impedance, with the structures of the laminar screen (29).
16. A radio antenna arrangement according to claim 10,
    characterised in that the first antenna element (3) is disposed on the pane substantially normally to the pane surface (1) and that the further antenna element or elements (8) is/are disposed along the pane surface or between the two layers of a laminated glass pane (Fig. 10a, 10b).
17. A radio antenna arrangement according to claim 10,
    characterised in that both the first antenna element (3) and the further antenna element or elements (8) are disposed along the pane surface or between the two layers of a laminated glass pane (Fig. 13).
18. A radio antenna arrangement according to claim 17,
    characterised in that a cavity (31) with an electrically-conductive edge is disposed in the inside of the pane in the area of the structures for the first antenna element (3) and for the other antenna element or elements (8), the opening of this cavity facing the glass pane, and the edge is conductively connected at high-frequency with the metallic bodywork (5) and optionally also with the laminar screen (29) on the pane (1) (Fig. 12, 13).
19. A radio antenna arrangement according to claim 18,
    characterised in that antenna elements, configured as monopoles, are disposed between the conductive rear wall of the cavity (31) and the glass pane, wherein the rear wall of the cavity, and the strip line network (4) which is optionally disposed thereon, serves as an electrical counterweight (Fig. 12).
20. A radio antenna arrangement according to claim 19,
    characterised in that the monopoles are configured as capacitatively-loaded antenna elements, optionally provided with lengthening coils, in order to shorten their structural shape (Fig. 12).
21. A radio antenna arrangement according to claim 18, 19 or 20, characterised in that the cavity (31) has an internal height of at least 1/20 of the free space wavelength.
22. A radio antenna arrangement according to one of claims 1 to 3, characterised in that the antenna elements are disposed on the horizontal line of a wing and the border line (13) is formed by one of the edges of the wing.
23. A radio antenna arrangement according to one of claims 1 to 22, characterised in that the radio antenna arrangement is configured for a plurality of radio systems in the microwave range with relatively narrow-band frequency ranges of different frequencies and the antenna elements (3) or (8) and optionally the network (4) and the remaining frequency-dependent parts of the radio antenna arrangement are multifrequency-configured.
24. A radio antenna arrangement according to claim 23,
    characterised in that separate antenna elements (3) or (8) are also used - or only used - to cover the various frequency ranges.
25. A radio antenna arrangement according to one of claims 1 to 24, characterised in that connection gates are formed in the antenna elements (3) or (8), the complex total matrix of which is determined according to amount and phase in order to describe the connections between the electrical magnitudes at these connection gates (27) of the network (4), the excitation of which, e.g. in the event of reception, being detected by a horizontally-incident vertical polarised reception wave for all azimuthal angles according to amount and phase to one another, so that the parameters for description of the electrical magnitudes at the connection gates (27), based on the incident reception wave for all azimuthal angles, are known and by variation calculation in the sense of solving the object of the invention, favourable amplitude and phase values for control of the matrix are detected and these values are set by wiring to the network (4) and/or optionally by wiring the gates to reactances (14) in the group antenna.
26. A radio antenna arrangement according to one of claims 1 to 25, characterised in that the network (4) is configured so that, with the help of electronic switches which are controlled by an antenna diversity apparatus, on reception the signals of the antenna elements (3) or (8) are used in various combinations to form antenna diversity signals for forwarding to the receiver.

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