EP0662255B1 - Radio antenna arrangement on the window pane of a motor vehicle - Google Patents

Description

The invention relates to a radio antenna arrangement according to the The preamble of claim 1. Such a radio antenna arrangement can be used advantageously e.g. for the radio systems of mobile communication (car phone in the C, D or E network or for trunked radio systems).

A radio antenna arrangement of this type is known from US, E, RE 33743 (BLAESE) dated November 12, 1991.

It is also from the publication PATENT ABSTRACTS OF JAPAN, vol. 9, no.178 (E-330) of July 23, 1985 and JP, A, 60 047 523 (NIPPON DENSHIN DENWA KOSHA) March 14 1985 known to install two dipoles in the interior of a motor vehicle, one in close to the windshield and the others near the rear window of the vehicle. Transmit and receive signals of the two dipoles are fed to a hybrid circuit, which is connected to a transmitter and two receivers. The outputs of the Receivers are each connected to a switch, through which either one or the other receivers can be connected to a diversity output.

If there is no mounting hole in the vehicle body is often a rod-shaped antenna in the upper area the vehicle rear window applied, the antenna element then attached to the outside of the glass pane and that Antenna counterweight also e.g. attached to the window pane is, or e.g. formed by the coaxial feed cable is that can be completely installed inside the vehicle and the capacitive coupling of the antenna signals through the disk can be done through.

A disadvantage of such an antenna according to the prior art is that due to the inclination of the rear window the base point of the antenna element clearly below the roof edge of the vehicle is arranged. As a result, the antenna element at least in the lower area, forcibly through the body is shadowed towards the front. Also results due to the proximity of the conductive body parts strong radiation coupling with the body, which on this causes strong currents, which in turn cause radiation, so that the directional diagram is strongly influenced.

The desired characteristic for automotive radio antennas Horizontal diagrams with the most uniform possible radiation in all directions in space is therefore only in practice rotationally symmetrical antenna elements in the middle of the roof approximately reached. With off-center antennas or with the antennas glued onto the vehicle window through the radiation coupling with the vehicle body undesirable and sometimes intolerable deformations of the horizontal diagram, that is in particular radiation compensation, which strong indentations cause in the horizontal diagram. As a rule, the radiation in the solid angle range is special reduced inadmissibly to the front. It also joins frequency becomes a pronounced segmentation of the diagram on. This leads in particular to the minima of the horizontal radiation with a given radiation power in transmission mode often to undesirably low radiation densities at the receiving location, i.e. to undesirably large radio field attenuation.

In practice, it is important for radio antennas that for a given one Transmitter power in no horizontal direction the radiation density falls below a minimum required value.

The object of the invention is therefore to provide a radio antenna arrangement according to the preamble of claim 1, 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 achieved in a generic radio antenna arrangement by the characterizing features of claim 1 .

The advantages that can be achieved with the invention are, in particular, the possibility of enabling short and optically inconspicuous antennas without loss of function, that is to say, with a high performance of the antenna system, being able to implement an optically very attractive solution in terms of vehicle-specific aspects.

• 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 a suitable positioning on the window pane of a specific motor vehicle, allows a specific generation of current distributions on the antenna elements of the radiator group according to the 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 the radiation in the vertical direction in favor of small elevation angles and
• the smallest possible indentation of the horizontal radiation diagram occurs,

which causes the lowest flat radiation density occurring in the entire horizontal region to be as large as possible.

Due to the measures taken according to the invention unwanted radiation of the excited by radiation coupling Vehicle body not prevented. By suitable Current distributions on the antenna elements of the radiator group according to amount and phase is rather due to the multitude of Radiator superimposed on a wave field, which in total has radiation properties according to the object of the invention. Embodiments of the invention are in the drawings 1 to 10 and are described in more detail below.

Show it:

Fig.1:

Group antenna according to the invention with two arranged one above the other rod-shaped antenna elements and with a Network with antenna connection point.

Fig.2a:

Group antenna according to the invention with two one above the other arranged rod-shaped antenna elements and with a Stripline network.

Fig.2b:

Example of a stripline network with one retarded and reduced in amplitude feeding the upper antenna element. The stripline network serves at the same time as an antenna counterweight.

Fig. 3:

Group antenna according to the invention with two arranged one above the other and through an extension spool and a Roof capacity of electrically extended antenna elements.

Fig. 4:

Group antenna according to the invention with three antenna elements and with radially and annularly attached wire-shaped conductors to enlarge the ground area.

Fig.5a:

Group antenna according to the invention for the radio frequency low impedance coupling of another antenna and for the Radio frequency low-resistance coupling of the heating conductors in turn galvanically with each other via further vertical conductors are connected.

Fig.5b:

Detail drawing of a low impedance for the radio frequency Coupling of another antenna and a heating conductor after Fig.5a.

Fig.6a:

Group antenna according to the invention with two one above the other arranged antenna elements.

Fig.6b:

Group antenna according to the invention with antenna elements, that are horizontally offset from each other.

Fig.7a:

Group antenna according to the invention with three antenna elements, those in a triangle based on it are arranged.

Fig.7b:

Group antenna according to the invention with three antenna elements, those in a triangle on top are arranged.

Fig. 8:

Group antenna according to the invention with more than three antenna elements.

Fig. 9:

Antenna element according to the invention with two connection gates.

Fig.10a to c:

Horizontal directional diagrams of the individual emitters according to Fig. 7b. (Antennel top left; Antenna2 top right; Antenna3 bottom center)

Fig.10d:

Horizontal directional diagram of the array antenna according to the invention according to Fig. 7b

Fig.1 shows the basic structure of an inventive Group antenna with two antenna elements 3 on a window pane 1 of a motor vehicle, usually this is a rear window. The two rod-shaped antenna elements 3 are on the outside attached, e.g. glued in conventional technology. Especially good radiation properties in the sense of solving the task of Invention are achieved in such vehicles when the angle of inclination 13 of the window pane opposite the horizontal is not greater than 60 degrees.

In the example in FIG. 1, the antenna elements 3 are one above the other arranged. Especially with symmetrical vehicle shapes often the location on the vehicle's axis of symmetry advantageous in the longitudinal direction. As antenna counterweight 4 are conductive surfaces around the antenna elements on the window surface upset. The metal body of the vehicle is 8 featured.

The frequency range in the antenna arrangements according to the invention used is the wavelength range of the decimeter waves (Free space wavelengths between 1m and 10 cm) or even shorter Waves (less than 10 cm free space wavelength). In these frequency ranges modern radio systems such as the C, D and E Network mobile phone or other services such as Trunked radio services, operated.

It is in the interest of the most reliable radio operation possible It is important that there is no angular range when radiating the radio waves with significantly reduced radiation intensity. The minimal radiation intensity resulting in an angular range is therefore a decisive factor for each emitted transmission power Criterion for the performance of a radio antenna arrangement.

In the case of one on or in a vehicle window according to the status the radio antenna attached to the technology, it is inevitable that in certain spatial directions comparatively little radiation intensity is emitted. On the one hand, this results from the sloping to the rear of the vehicle, causing one on the Disk-mounted radio antenna in a shaded area of the Body lies when the radiation is viewed forward. On the other hand, there is always strong radiation coupling with the given conductive vehicle body, which is reflected in the Frequency range of the decimeter waves or above because of the compared to the operating wavelength large size of the vehicles with the accompanying resonance currents in the body results in an undesirable split-up of the horizontal diagram.

The horizontal directional characteristic of each of the two individual antenna elements 3 therefore also points to group antennas according to the invention undesirable deviations from the ideal radiation pattern on. In addition, the individual diagrams are the Individual antennas are not the same as each other because of the different Mounting points the shadowing through the body and the coupling with it is not the same.

The greater the angle of inclination 13 of the window pane 1, the greater It is more advantageous to place the radiators near the upper edge to arrange the window pane. If the angle of inclination is not too steep can also the antenna elements 3 accordingly run briefly. This results in a lower limit of about 1/10 of the wavelength (lambda / 10). With strong angles of inclination the disc are longer antenna elements 3, e.g. Lambda / 2 elements preferable.

In the case of group antennas according to the invention, the Antennas in the case of transmission via a low-loss network 7, which in Example of Fig. 2a representative of a stripline network is shown.

The network 7 is designed such that a defined one and a fixed phase and amplitude relationship of the base feed currents of the two antenna elements 3 is present. over this defined phase and amplitude relationship becomes the horizontal diagram the antenna arrangement according to the invention in the desired advantageous type influenced and compared to the radiation characteristic each of the individual antennas improved.

At the antenna connection point 6 of the group antenna is in the As a rule, a standing wave ratio for the respective useful frequency band required as it is from other RF interfaces Radio systems is known. At this antenna connection point 6 is then usually a coaxial line 11 connected to the Radio leads.

In Fig. 1, the connection point 2 of the antenna element 3 is over a galvanic connection to the network 7, which on the Is attached to the inside of the window pane 1. in the Network 7 itself the signals of the antenna elements are linked and connected to the antenna connection point 6. In the drawn For example, the connection between antenna element 3 and the network 7 via a hole through the glass. For Avoiding such an unfavorable bore 2a, the antenna element 3 is capacitively designed high-frequency connection 16 connected to the network 7. The latter is necessary to create the necessary phase and amplitude relationships very advantageous as a stripline circuit realizable. This configuration enables Series production an inexpensive reproduction of the necessary Phase and amplitude relationships between the electrical Sizes on the antenna elements. In this case, the capacitive connection 16 technologically inexpensive in the Stripline circuitry may be included, as shown in Fig. 2b is shown. The connection point 2 of the antenna element 3 is executed as a circular area

The antenna elements 3 are radiation-coupled to one another and are also electrically connected to each other via the network 7 linked so that with respect to the antenna connection point 6 including the resulting radiation characteristics the radiation coupling with the body of the vehicle. In a simplest embodiment of this network 7 a group antenna can also be designed, in which the Coupling between the rays only through the Radiation coupling of the antenna elements 3 takes place. In this The case is only one of the existing radiators with the antenna connection point 6 connected to the network 7 via a radio frequency line. The radiation pattern of the overall arrangement is however, essentially due to the totality of the radiation-coupled Antenna elements 3 including the effect the vehicle body.

The radiation coupling between the antenna elements becomes essential determined by their length and their distance from each other. Hiebei shows that if the distances between the Emitters that have a tendency to to form strong indents. In preferred antenna arrangements are therefore also in the interest of a simple design of the Network 7 the distances between the farthest from each other removed antenna elements no larger than about 2 times Wavelength selected. To solve the problem of the invention demanding phase and amplitude states of the electrical Sizes on the antenna elements are therefore significantly different from theirs Shape and position to each other and the radiation coupling with the conductive vehicle body. So there is for each vehicle has a variety of favorable arrangements of antenna groups according to the invention, each by specific for this Optimization of the network 7 advantageous radiation properties surrender. The radiator shapes used for this can can be freely chosen within certain limits. Instead of easier Rod-shaped antenna elements can, for example, as in Fig. 3, Antenna elements with a capacitive load 15 can be used and in the interest of further shortening e.g. with blind elements 14 can be connected. Even with longer antenna elements with a length of lambda / 2, the current assignments be suitably influenced on the antenna elements.

A particularly simple design of a group antenna results when using two emitters according to FIG. 6a. Especially when mounted on inclined window panes e.g. in the stern the radiation of a vehicle is shadowed to the front. In In this case, it is advisable to connect a first radiator directly to the to attach the upper edge of the window and to fill in the shading the second radiator a short distance below the first Attach spotlights and control them in the correct phase. A particularly advantageous arrangement on inclined Window panes are the triangular arrangement in Fig. 7b. There will be to maximize the total radiation, two emitters on the top Edge of the window preferably attached symmetrically to the center and another to fill in the shading to the front Spotlights preferably in the vertical line of symmetry 24 in one favorable distance 28 placed below. By control with a network 7 optimized for this configuration very good circular diagrams with correspondingly small indents cause.

The effect achieved with the invention is impressive 10a to 10d. In the horizontal diagrams shown images 10a to 10c are the radiation properties the single radiator shown in Fig. 7b. Each of the charts has strong intolerable indentations or shading areas. Although the antenna elements used rotationally symmetrical structures of that shown in Fig. 3 Form, result from the radiation coupling with the non-roundness shown of the conductive vehicle body of the diagrams. By connecting to a suitable network 7, which the antenna elements in phase and amplitude correct feeds and its characteristics by using mathematical Optimization procedures specifically for those on the particular vehicle measured antenna elements are calculated in Fig. 10d achieved directional diagram, which is essential has fewer indents.

For the inventive design of the group antenna is for each antenna element has a time-invariant antenna counterweight necessary. This is advantageous as a high-frequency conductive Surface on the window pane, as shown in Fig. 4, educated. In the interest of the transparency of this area this is designed as a radial structure, which consists of radial from the network 7 outgoing wire-shaped conductors 20. The network 7 itself is advantageous with a conductive Outside area, which is in the center of the group antenna part of the antenna counterweight for the antenna elements forms. The radiation-like conductors become high-frequency with it conductive outer surface connected. These rays can pass through conductors attached in a ring around the group antenna into one high-frequency conductive mesh network can be supplemented. With radio antennas naturally occur on the rear window of vehicles large field strengths in the immediate vicinity of the transmitting antenna, which people in the passenger compartment could endanger. Training of the antenna counterweight as a high-frequency conductive surface has a very advantageous shielding effect against electromagnetic fields, which would otherwise push into the passenger compartment. The requirement according to a defined antenna counterweight advantageously combine with the demand for a field weakening the dangerous electromagnetic radiation.

There are often horizontally mounted heating conductors on the rear window 23 available (Fig.5a). Points of equal DC potential can be galvanically connected to each other without the Influence heating current flow. By introducing connecting Line bridges, as in Fig. 5a, can also be the heating field 23 high-frequency largely shielding surface can be designed and act as an expanded antenna counterweight. Around high-frequency currents between the ground surface at the group antenna to enable via the heating field 23 without the heating currents to influence is a DC-impermeable, frequency-selective Connection 21 in the wire-shaped conductors 20 advantageous. Such frequency selective connections are also necessary if parts of the antenna counterweight as antenna parts for others Radio services, which are also attached to the window pane are, are used. An example of this is in Fig. 5a given for the antenna 22, which e.g. act as an AM-FM antenna could. As frequency-selective connecting elements 21 come in the main thing is to use capacitive structures. Very advantageous is also a coplanar line structure of about Lambda / 4 length for the radio frequency, as detailed in Fig. 5b using the example of the AM-FM antenna and the heating conductor connection is shown.

If the group antenna is to be used for several radio systems, e.g. the D network and the E network can be designed equally, so the antenna elements are designed so that they are in both frequency ranges are functional. This will be the network 7 designed so that it is in the two frequency ranges the phase and amplitude conditions required for this ensures for the individual radiators, so is the group antenna applicable in both frequency ranges. One more way consists of at least for both frequency ranges partially use separate antenna elements.

To ensure the best possible connection of the signals in the network 7 a certain amount of measurement is necessary to ensure to determine the antenna properties of the emitters on the vehicle. This happens because, as shown in Fig. 9, the connection points 2 as connection gates 27 of a radiator network to be viewed as. With the help of modern network analyzers can determine the wave parameters of this radiator network become. In addition, when a wave comes in from a certain Direction of the excitations at the connection gates 27 Amount and phase are measured. With knowledge of the properties of the radiator network and its excitation by the incident Shaft at the various connection gates 27 can be modern with the help Computer systems using suitable optimization strategies an optimal network 7 can be designed for this.

For the transmission case, the radio antenna according to the object of the invention work. In the case of receipt, however, is due to the Rayleigh scattering of the received waves is generally an antenna diversity operation preferable. The network can be designed this way be that with the help of switching diodes different signal combinations the individual signals received by the beams are formed at the antenna connection point 6. With the help of a Antenna diversity device can control the switching diodes in this way be that at any moment the signal combination at the antenna connection point, which appears the best possible Reception causes. The design of the radio antenna as a group antenna thus offers the advantage of simultaneous usability as a diversity antenna.

Claims (22)

1. A radio antenna arrangement for the establishment of radio contact with terrestrial radio stations for microwaves or centimetre waves with an antenna mounted on the inclined window pane in a substantially electrically-conductive vehicle body, comprising an antenna element disposed on the outside of the window pane and orientated normally to this and an antenna counterweight disposed on the window pane, characterised in that at least one further antenna (10) is present, comprising in each case an antenna element (3) disposed on the outside of the same window pane (1) and orientated normally to this and an antenna counterweight disposed on the window pane (4) and the antennae (10) together form a group antenna with an antenna connection point (6).
2. A radio antenna arrangement according to claim 1, characterised in that a network (7) is present which contains the antenna connection point (6) and that at least one antenna (10) is connected to the network (7) and that the antenna connection point (6) is a part of the network (7) and that each subsequent antenna (10) is either merely coupled to the other antennae (10) via a high frequency via radiation coupling or contains a connection point (2) which is connected to the network (7) (Fig. 1).
3. A radio antenna arrangement according to claim 1 to 2, characterised in that the distance (9) between the furthest-spaced antenna elements (3) is not greater than double the wavelength.
4. A radio antenna arrangement according to claim 1 to 3, characterised in that dummy elements (14) are introduced into the antenna elements (3) in order to set suitable current allocations according to value and phase.
5. A radio antenna arrangement according to claim 1 to 4, characterised in that the antennae (10) have monopolar character and the antenna elements (3) are rod-shaped, with or without top-loading capacity, and each have a high-frequency conductive surface (5) as an electrical antenna counterweight (4) which is substantially disposed in the plane of the pane (1).
6. A radio antenna arrangement according to claim 2 to 5, characterised in that the network (7) is disposed in the vehicle interior and the high-frequency connection (17) is made, in each case capacitively through the pane, between the network (7) and the antennae (10) connected via their connecting points (2) (Fig. 2a).
7. A radio antenna arrangement according to claim 2 to 6, characterised in that the network (7) is partially disposed on the window pane (1) outside the vehicle and the high-frequency connection (17) to the antenna connecting point (6) takes place within the network (7) capacitively through the window pane (1) (Fig. 3).
8. A radio antenna arrangement according to one of claims 2 to 7, characterised in that the network (7) is substantially realised as a microstrip circuit (19) and the required amplitude and phase states of the currents and voltages on the antenna elements (3) are substantially generated by conducting elements (18) (Fig. 2b).
9. A radio antenna arrangement according to claim 1 to 8, characterised in that the antenna elements (3) each have an earth surface (5) disposed substantially on one of the window surfaces of the window pane (1) as an antenna counterweight (4), in each case forming an antenna (10) therewith.
10. A radio antenna arrangement according to claim 9, characterised in that the earth surface is formed by a conducting surface (5) on the surface of the network (7) (Fig. 2a).
11. A radio antenna arrangement according to claim 9 and 10, characterised in that in order to improve the high frequency effect of the earth surface (5), wire-shaped conductors (20) are laid out substantially radially from the network (7), or additionally, such conductors are disposed in a substantially ring-shaped formation about the network (7) (Fig. 4) .
12. A radio antenna arrangement according to claim 11, characterised in that the wire-shaped conductors (20) contain frequency-selective filter elements (22) which are shaped so that they represent low impedance connections at radio frequencies (Fig. 5b).
13. A radio antenna arrangement according to claim 11, characterised in that heating conductors (23), running parallel to one another, are provided on the rear windscreen and points of the same DC voltage are conductively connected to one another via substantially perpendicularly-orientated vertical conductive webs, whereby the heating field forms a high-frequency conductive surface, and in order to permit high-frequency currents between this surface and the earth surface (5) emanating from the network (7), frequency-selective filter members are included in the wire-shaped conductors (20) which are impermeable to direct current (Fig. 5a).
14. A radio antenna arrangement according to claim 11 and 13, characterised in that parts of the wire-shaped conductor (20) are used by parts of other antennae (22) which are disposed on the window pane for other radio services (Fig. 5a).
15. A radio antenna arrangement according to claim 1 to 14, characterised in that two antennae (10) are arranged horizontally adjacent on the window pane (1) or on a vertical line one above the other on the window pane (1) (Fig. 6a, Fig. 6b).
16. A radio antenna arrangement according to claim 1 to 14, characterised in that three antennae (10) are arranged on the window pane (1) in a triangular fashion (Fig. 7a, Fig. 7b).
17. A radio antenna arrangement according to claim 16, characterised in that the antenna elements (3) are designed to be rod-shaped and are approximately one to three tenths of a wavelength long, and two of the antenna elements (3) are disposed in a horizontal line (25) near the upper edge, symmetrical to the vertical line of symmetry (24) of the vehicle, and that the third antenna element (3) is disposed on this symmetry line but below the horizontal line (25) so that the side lengths of the triangle are approximately one to three tenths of a wavelength (Fig. 7b).
18. A radio antenna arrangement according to one of claims 1 to 14, characterised in that more than three antennae (10)have antenna elements (3) disposed on cross points of the horizontal lines with the vertical columns of a grid structure with screen line distances of approximately one to three tenths of a wavelength, the antenna elements (3) being disposed in the upper area of the window pane (Fig. 8).
19. A radio antenna arrangement according to claim 1 to 18, characterised in that the group antenna is set up for a plurality of radio systems with relatively narrow-band frequency ranges and in that the antennae (10) or the antenna elements (3), and also possibly the network (7) and the remaining frequency-dependent parts of the group antenna are designed to have a multi-frequency nature.
20. A radio antenna arrangement according to claim 19, characterised in that in order to cover the various frequency ranges, additional isolated - or only isolated - antennae (10) are used.
21. An antenna according to claim 1 to 20, characterised in that connection gates (27) are formed in the antenna elements (3), the complex overall matrix of these connection gates being determined, in terms of its amplitude and phase, in order to describe the correlations between the electrical amplitudes at these connection gates (27) of the antenna network, and their excitations, e.g. in the event of receipt via a horizontally-incident reception wave for all azimuthal angles, are determined in terms of their amplitude and phase relative to one another, so that the parameters are known for all azimuthal angles in order to describe the electrical amplitudes at the connection gates (27), with regard to the incident reception wave and favourable amplitude and phase values are detected by variation calculation, in the sense of the solution of the objective of the invention, for control of the entire matrix, and these values are set in the group antenna by wiring with the network (7) and/or possibly by wiring the connection gates (27) with resistances (14) (Fig. 9).
22. A radio antenna arrangement according to one of claims 1 to 21, characterised in that the network (7) is designed so that with the help of electronic switches located in its interior, which are controlled by an antenna diversity apparatus, the signals from the antennae (10) are used in different combinations for the formation of antenna diversity signals for forwarding to the receiver.

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