EP0346591A1 - Antenna for receiving meter waves,built in a window glass together with a heating of a motor vehicle - Google Patents

Abstract

The invention relates to an antenna for receiving metric waves in motor vehicle windows, having a metallic frame (21) in the form of an essentially vertical unipole (1) in the region of the vertical centre of the window. The window contains a window heater having essentially horizontal wire-shaped heat conductors (2). The unipole consists of two superjacently arranged regions (40, 41) which are directly adjacent and are electrically connected, the first region (40) being arranged in the region of the heating field and the second region (41) being arranged in the region outside the heating field. The unipole (1) is formed in each of the two superjacently arranged regions from one or more, virtually mutually parallel, essentially vertical antenna wires (11, 12) and is arranged essentially in the region of the centre of the window. The vertical antenna wires (11) cross the heat conductor (2) in the first region (40) and are electrically connected (35) to these. In the second region (41), the vertical wires (12) are electrically connected with a low resistance at their one end in each case to the heat conductor (38) located at the edge of the heating field, and at their other end with low resistance to a common connection point (8) by means of a joining antenna wire (10). From there, one antenna wire (22) runs essentially parallel to the frame edges to the decoupling point (23) in the vicinity of the frame (21). A continuing circuit (16) is present there, to the output of which the antenna line is connected. <IMAGE>

Description

The invention relates to an antenna for receiving meter waves in motor vehicle windows with a meat-like frame in the form of an essentially vertical unipole in the region of the vertical window center.

With antenna structures in vehicle windows, it is known that it is possible to receive all wave bands (e.g. LMK and VHF radio) with good performance. It is advantageous that the antenna, due to the integration into the vehicle body, meets vehicle-specific requirements such as mechanical robustness, long service life, easy installation and avoidance of unnecessary air turbulence much better than the standard rod antenna.

The invention is based on an antenna with very good suitability for frequencies in the FM range, as is known from P 2136 759. This antenna uses a unipole in a metallic frame, e.g. is formed by the frame of a vehicle window, the Unipol in this special application being applied to the glass window located therein. Such an antenna has excellent reception properties both for horizontally polarized waves and for vertically or circularly polarized waves and, in the embodiment according to the invention, delivers average signal levels which are almost equivalent to those of a passive telescopic antenna, as is customary for vehicles.

An overlap of the unipole with other conductive structures in the disk, e.g. However, heating structures such as those usually found in the rear windows of modern vehicles are not permitted for an antenna in accordance with P 2136 759. Consequently, an antenna according to P 2136 759 cannot be used in vehicles in which a considerable part of the window surface is covered by the heating wires of the window heater.

The object of the invention is to incorporate a heating field of the usual type with horizontal heating conductors in an antenna of the generic type such that the antenna achieves a high sensitivity regardless of the polarization of the receiving field of the meter waves in the receiver.

This object is achieved in a generic antenna by the characterizing features of claim 1.

The advantages that can be achieved with the invention consist in the excellent reception powers of the antenna thus formed for horizontally and for vertically or circularly polarized waves in the meter wave range, while at the same time largely uncritical dimensioning with regard to the required ones Number of ancestors, their distance from each other and the total height of the structure. From the point of view of the technological requirements, it is particularly advantageous that the same technology is used for the realization of the antenna conductors and the heating conductors, both types of conductors being applied to the pane in the same working process in the screen printing process or with wires inserted between the layers of a laminated glass pane. can be introduced. These aspects are the prerequisite for an extremely cost-effective implementation. The galvanic connection of antenna conductors and heating conductors also has the advantage with printed conductors that no further contacting is required during the galvanizing process, as is the case with antennas without a galvanic connection.

Exemplary embodiments of the invention are illustrated and described in more detail below with reference to the drawings.

• Fig. 1: Antenne nach der Erfindung mit 5 vertikalen Antennen im 1. Bereich und 3 vertikalen Antennenleitern im 2. Bereich, unsymmetrisch zur Scheibenmitte angeordnet und mit kleinem Abstand zum Rahmen angeordnetem weiterführenden Antennenleiter
• Fig. 2: Äquipotentiallinien in der beheizten Scheibe und Kennzeichnung des Bereichs, in dem die Antennenleiter (11) und (12) anzuordnen sind
• Fig. 3: Antenne nach der Erfindung mit nur jeweils 1 Antennenleiter im 1. und 2. Bereich und dem Auskoppelpunkt auf der Symmetrielinie der Scheibe in der Nähe des Rahmens.
• Fig. 4: Exemplarische Kennzeichnung der bevorzugt wirkenden Empfangszone des Unipols nach Fig. 3
• Fig. 5: Fahrzeugscheibe mit 2 erfindungsgemäßen Antennen und einem unterteilten Heizfeld
• Fig. 6: Erfindungsgemäße Antenne mit jeweils 2 und parallel im Abstand (56) geführten Antennenleitern und mit einer separaten LMK-Empfangsstruktur (24)
• Fig. 7: Exemplarische Kennzeichnung der bevorzugt wirkenden Empfangszone des Unipols nach Fig. 6
• Fig. 8: Detail aus Fig.6 zur Kennzeichnung der Aufteilung der Heizströme für den Heizleiter (38)
• Fig. 9: Ersatzschaltbild der Fig.8
• Fig. 10: Ersatzschaltbild
• Fig. 11: Vermeidung der Aufteilung des Heizstroms durch kapazitive Verbindungen im zusammenführenden Antennenleiter
• Fig. 12: Vermeidung der Aufteilung des Heizstroms durch kapazitive Verbindungen zwischen Antennenleitern (12) und dem Heizleiter (38)
• Fig. 13: Antenne nach der Erfindung mit einem in großem Abstand vom Rahmen parallel geführtem weiterführenden Antennenleiter und separater LMK-Struktur
• Fig. 14: Antenne nach der Erfindung, für Diversitysysteme um eine zweite Antenne mit dem Auskoppelpunkt (61) erweitert.
• Fig. 15: Vorteilhafte Ausführungen der Heizfeldnetzwerke

In detail shows:

• Fig. 1: Antenna according to the invention with 5 vertical antennas in the 1st area and 3 vertical antenna conductors in the 2nd area, arranged asymmetrically to the center of the pane and with a small distance to the frame arranged further antenna conductors
• Fig. 2: Equipotential lines in the heated disc and marking the area in which the antenna conductors (11) and (12) are to be arranged
• Fig. 3: Antenna according to the invention with only 1 antenna conductor in each of the 1st and 2nd area and the coupling point on the line of symmetry of the disc near the frame.
• FIG. 4: Exemplary identification of the receiving zone of the unipole according to FIG. 3, which acts preferentially
• Fig. 5: Vehicle window with 2 antennas according to the invention and a divided heating field
• 6: Antenna according to the invention, each with 2 and parallel antenna conductors (56) and with a separate LMK reception structure (24)
• 7: Exemplary identification of the receiving zone of the unipole according to FIG. 6, which acts preferentially
• 8: Detail from FIG. 6 to identify the division of the heating currents for the heating conductor (38)
• Fig. 9: Equivalent circuit of Fig. 8
• Fig. 10: Equivalent circuit
• Fig. 11: Avoiding the division of the heating current through capacitive connections in the connecting antenna conductor
• Fig. 12: Avoiding the division of the heating current through capacitive connections between antenna conductors (12) and the heating conductor (38)
• FIG. 13: Antenna according to the invention with a further antenna conductor and a separate LMK structure, which is guided in parallel at a large distance from the frame
• Fig. 14: Antenna according to the invention, expanded for diversity systems by a second antenna with the decoupling point (61).
• Fig. 15: Advantageous versions of the heating field networks

1 shows the basic arrangement of an antenna according to the invention. The metallic frame (21), which represents the body of the vehicle, encloses a vehicle window (34) on which a structure of horizontal heating conductors (2), the heating conductor being on the border between the 1st area (40) and the 2. Area (41) is arranged, which carries the designation (38). In modern vehicles, these horizontal heating conductors are either printed on the surface of the vehicle window using the screen printing process and then galvanically reinforced in order to achieve a low-resistance value required for heating purposes or, in the case of vehicle windows made of double-pane laminated glass, between the two glass windows, e.g. in the form of tungsten wires.

In both cases, the heating conductors (2) are wire-shaped. The area of a vehicle window covered by the heating field is usually large, so that only comparatively narrow strips remain above and below the heating field, the dimensions of which do not allow the realization of antennas for the meter wave range with the good properties specified in P 2136 759.

1, in the case of an antenna according to the invention, the antenna conductors (11) overlap with the horizontal heating conductors (2) or (38) in the manner shown in the first area (40) with the horizontal dimension (4) and the vertical dimension ( 6), where (7) is the vertical dimension of the heating field. It is essential for an antenna according to the invention in the first area (40) that, among other things, there is a galvanic connection at the crossing points (35) between the horizontal heating conductors (2) and the antenna conductors (11).

In the case of heating conductors (2) printed on the pane, the galvanic connection between the antenna conductors (11) and antenna conductors (12) is automatic and is even the prerequisite for inexpensive production, since the isolated crossing of printed conductors is technologically much more difficult is to be realized.

In the case of heating conductors (2) and antenna conductors (11) and (12) as well as (10) and (22) inserted between the individual panes of a laminated glass pane, the galvanic contact between these conductors occurs when the two individual panes are glued due to the interposed plastic film at high temperature also if the two types of conductors are placed on the same side of the plastic film during preparation. It is not absolutely necessary for an antenna according to the invention that a galvanic contact is established at each of the crossover points, since the distance between the heating conductors in such panes is so small (approx. 5 mm) that there is a much larger number of crossover points and also Without a galvanic contact everywhere at the crossing points, the capacitive coupling of heating conductors and antenna conductors (11) for the frequencies of the meter wave range has the same electrical effect.

With regard to the selection of the structure of the antenna conductors, there are hardly any restrictions from an manufacturing point of view for an antenna according to the invention. Complicated conductor structures as well as changes in the cross-section and thus resistance of the conductors can be realized with a suitable sieve at no additional cost and in the same operation in which the heating conductors are also printed. However, there are restrictions especially with regard to the thinnest conductor width, which can be realized without the risk of interruption. Therefore, printed structures are clearly visible and therefore visually striking. An important secondary aspect for the selection of the arrangement of the antenna conductors is therefore also to take stylistic considerations into account, which means that the use of an unnecessarily large number of antenna conductors for an antenna according to the invention is suggested.

Very thin tungsten or copper wires, which are almost invisible, are used for heating conductors and antenna conductors inserted between the individual panes of a laminated glass pane. Consequently, stylistic aspects are of much less importance when selecting the antenna conductor arrangement than with printed conductors. In contrast, each additional conductor to be introduced increases the manufacturing costs, since essentially every conductor of the antenna structure has to be placed individually on the plastic film. Therefore, even with such vehicle windows for an antenna according to the invention, the use of the smallest possible number of antenna conductors with the clearest possible arrangement should be sought.

From the point of view of heating the pane, these vertical antenna conductors (11) represent undesirable shunts, via which equalizing currents can flow between the individual horizontal heating conductors (2), as a result of which the defrosting properties of the heating pane are undesirably changed. In an antenna according to the invention, this is avoided in that the antenna conductors (11) the horizontal heating conductors (2) in one Cross in such a way that the individual crossing points each lie on one of the antenna conductors (11) and the cut horizontal heating conductors (2) on equipotential lines (37) with respect to the DC voltages of the heated pane in accordance with FIG. 2, so that no compensating currents flow in the antenna conductor (11) .

According to Fig. 2, e.g. the line of symmetry (3) of the pane represents such an equipotential line, along which exactly half the voltage of the on-board battery (36) is present when the heating is switched on relative to the frame. Fig. 2 shows further equipotential lines (37). Obviously the equipotential lines are not exactly parallel to each other, whereby the deviation from the parallelism with respect to the equipotential line in the center of the pane is greater towards the edge of the pane, and the more pronounced the trapezoidal shape of the pane is compared to a rectangle. If the antenna conductors (11) are consequently arranged only in a sufficiently narrow area around the vertical line of symmetry of the disk (3), the parallel arrangement of the antenna conductors (11) can be used as a good approximation to the equipotential lines.

For an antenna according to the invention, one end of the antenna conductors (11) is galvanically connected to the horizontal heating conductor (38) forming the end of the heating field, so that the 1st area (40) and the 2nd area (41) are immediately adjacent. Starting from this horizontal heating conductor (38), each of the antenna conductors (11) crosses at least one further heating conductor (2). In the example in FIG. 1, 6 of a total of 9 horizontal heating conductors (2) or (38) are crossed.

The number of antenna conductors (12) in the second area (41) can fundamentally differ from the number of antenna conductors (11) in the first area (40), as shown in FIG. 1, in which there are three antenna conductors (12) . These begin at the heating conductor (38) forming the edge of the heating field, to which they are galvanically connected, and end at the merging antenna conductor (10), to which they are connected with low impedance for the frequencies of the useful frequency band within the meter wave range.

According to the characterizing part of claim 1, all antenna conductors (11) and (12) for an antenna according to the invention are arranged in an area (42) of half the central pane width (5) symmetrical to the line of symmetry (3) of the pane (Fig. 2).

The assessment of the performance of the respective antenna according to the invention with a variation in the arrangement and the number of antenna conductors (11) and (12) is carried out in practice using known, statistically evaluating, computer-aided measurement methods which determine the antenna output level with the aid of a measurement receiver, and in which test drives are carried out in typical reception fields with the respective to investigating frequency and polarization of the incident wave, the mean signal levels and the level statistics of the test antenna are determined in comparison to a reference antenna.

Such measurements show that antennas according to the invention only change their properties in a good-natured manner when the arrangement and the number of antenna conductors are changed.

The simplest arrangement of the antenna conductors for an antenna according to the invention consists in each case of a single vertical conductor (11) in the 1st area and (12) in the 2nd area, which merge directly into one another. The merging antenna conductor (10) degenerates in this special case to the connection point (8), from which the further antenna conductor (22) essentially parallel to the two narrow sides of the frame, that is along the line of symmetry (3) to near the frame to Coupling point (23) leads and represents the direct continuation of the antenna conductor (12) (Fig.3).

In the following the function of such an antenna according to the invention is described by way of example with reference to FIG. 3. As is known, the pane opening enclosed by the conductive frame (21) is to be regarded approximately as a slot radiator which is optimally excited by a wave with an electrical field strength vector oriented in the direction of the vertical line of symmetry (3) of the pane. At frequencies at which the pane width corresponds to approximately half a wavelength, as is usually the case in today's cars in the middle of the frequency range of the meter waves, there is also a resonant increase in the electrical fields in the center of the pane. In the case of vehicle panes with a heating field, this resonance is more damped compared to panes without a heating field and is correspondingly broader because the heating conductors are inevitably coupled to the high-frequency field within the frame and this results in considerable losses for the high-frequency field, since the heating conductors correspond to theirs The task already has a considerable ohmic series resistance for direct current and the electrical conductivity of both the printed heat conductor printed today and the inserted wires continues to decrease with increasing frequency.

With horizontal as well as vertical and circularly polarized reception fields, field components in the direction of the symmetry line (3) are present because of the inclined pane in the vehicle, which excite the pane opening electrically. The unipole, which consists of sections (11) and (12) in an antenna according to the invention, is therefore strongly coupled to the reception field. The coupling is at a maximum if this antenna conductor is arranged in the line of symmetry of the pane, because due to the short circuit of the electrical field through the side frame parts, a symmetrical distribution of the electrical field strength with a maximum in the center of the pane is inevitable. Because of the known and in First approximation of sinusoidal characteristics of the field strength distribution, however, the signal decoupled from the Unipol only slightly decreases at the beginning, but quickly decreases with increasing proximity to the edge of the pane if it is attached asymmetrically. As the distance between the unipole and the line of symmetry (3) of the disk increases, the reception powers consequently become poorer, so that this unipole will preferably be arranged in the central region of the disk in an antenna according to the invention.

However, it may also be necessary and sensible to arrange the unipole asymmetrically to the line of symmetry (3) in the disk. Stylistic aspects may make this necessary or the need to use several antennas according to the invention with different reception behavior, e.g. for antenna diversity systems or for different partial frequency ranges of the meter wave range in a vehicle window. In such cases, with an antenna according to the invention, the unipole can be moved to the edge of the area (42) without loss of the essential properties of the antenna, which is arranged symmetrically to the line of symmetry of the disk and the width of which is as large as possible is half the average slice width.

Due to the galvanic connection, which is also effective for the frequencies of the meter wave range, between the antenna conductor (11) and the heating conductors (38) and (2) crossed by it, the heating conductors (38) and (2) are at the decoupling of the electrical field in an antenna according to the invention. 2) involved. Compared to the environment, each of the conductors in the disk represents a line with a high impedance and high losses compared to conventional coaxial lines. With increasing distance from the decoupling point (23), the degree of decoupling increases rapidly, so that the highest contributions to the received signal from the closer surroundings of the decoupling point (23).

Fig. 4 exemplifies the particularly effective part of the entire conductor structure of Fig. 3 to illustrate this property of the decoupling. This decoupling, which increases with the distance from the decoupling point (23), makes the good-natured behavior of an antenna according to the invention understandable with regard to changes in the number of antenna conductors and the geometry if these changes are carried out at a sufficient distance from the decoupling point.

For example, there are only minor and in practice insignificant deteriorations in the reception behavior if the antenna conductor (11) no longer crosses all 9 heating conductors (2) or (38) of the heating field, as shown in FIG. 3, but, for example, how shown in Fig.5, only the 5 heating conductors of a partial heating field crosses. The good reception performance of an antenna according to the invention is essentially retained as long as at least two heating conductors are crossed. However, the number of crossed heating conductors is preferably chosen to be greater than 2, as a rule as a result of this there are no other disadvantages and the reception properties tend to improve. Stylistic aspects also suggest choosing the length (6) of the antenna conductor (11) as large as the height of the heated surface (7), if not, for example, the need for further independent antennas in the pane, as shown in FIG to realize is given.

An advantageous embodiment of an antenna according to the invention further consists in using two or more antenna conductors (11) and (12) in the 1st and 2nd area. As a result, the zone which is preferably effective for reception can be widened, as will be explained below with reference to FIGS. 6 and 7.

In Figure 6, two antenna conductors (11) and (12) in the 1st and 2nd area are almost parallel, for optical reasons, the antenna conductors (11) and (12) merge directly into each other again. The distance (56) between the two antenna conductors is advantageously chosen in the range between 1/30 and 1/10 of the mean operating wavelength.

FIG. 7 shows an example of the area that preferably contributes to reception in the unipole structure according to FIG. 6. If (56) is selected in the range between 1/30 and 1/10 of the operating wavelength, there is a particularly efficient broadening of the preferably effective reception zone. If you choose the distance (56) smaller than the above, the effect is almost identical to that of a single antenna conductor, if you choose the distance (56) larger than the above, there is no further advantage. If the structure width (4) or (9) is greater than 1/10 of the operating wavelength, the use of additional antenna conductors is recommended.

A structure according to FIG. 6 again delivers somewhat better reception powers than the structure according to FIG. 3 because of the wider, preferably acting reception zone. At the same time, it has the further advantage that if one of the two conductor lines is interrupted, the reception power drops, but only to an extent that is hardly noticeable in practice, whereas in the case of a structure according to FIG ) the reception gets significantly worse. There is a risk of a conductor interruption especially in the case of panes with printed conductors, since these conductors can be damaged comparatively quickly.

The use of more than two antenna conductors (11) and (12) for an antenna according to the invention is in no case harmful, but due to the decoupling described above, the effect of an increase in reception power becomes smaller the further the newly introduced antenna conductors from Decoupling point (23) are removed. The area (42) within which the conductors (11) and (12) are to be arranged can therefore be specified as the upper limit for a sensibly designed unipole for an antenna according to the invention.

In the simplest case, the low-impedance connection of the antenna conductors (12) by the merging antenna conductors (10) takes place by means of a galvanic connection.

Such a galvanic connection through the merging antenna conductor (10) leads to a shunt for the heating current through the antenna conductor (12) in combination with the merging antenna conductor (10). The current in the heating conductor (38) is particularly affected due to the spatial proximity. The situation for this heating conductor (38) is explained in more detail below with reference to FIG. 8, which represents a section from FIG. 1 for the area of the pane center in the vicinity of the heating conductor (38).

At the branching point (45), the heating current (46) is divided into portions (47) and (48), the ratio of which, in a known manner, from the ohmic partial resistors (53) and (54) on the two current paths between the branching point ( 45) and the merging point (50) is determined, as shown by the electrical equivalent circuit for the current branch in FIG. 9. With the same specific conductivity of the antenna conductor (12) and heating conductor (38), the respective partial resistance is proportional to the respective path length between (45) and (50). Due to the fact that an equipotential line lies in the symmetry line of the structure, the current (49) in FIG. 8 is basically zero and therefore no longer needs to be considered in the following.

In the following, the effect of the length of the current paths on the ratio of the currents (47) and (48) and on the heating power between points (45) and (50) will be considered approximately. For the sake of simplicity, the geometry of FIG. 8 is to be assumed, in which the antenna conductors (12) are exactly parallel to one another and each have exactly the same length, so that the antenna conductor (10) bringing together has the same length as the distance between (45 ) and (50). In the arrangement shown in FIG. 8, there is a path difference for the two current paths corresponding to twice the length (52) of the antenna conductors (12) under these conditions. In addition, it should be assumed that the introduction of the current path via the antenna conductor (12) and the merging antenna conductor (10) does not change the total current (46). The following considerations can be applied analogously to deviating geometrical arrangements.

For a very short length (52) of the antenna conductors (12), i.e. for directly adjacent heating conductors (38) and merging antenna conductors (10), the two ohmic resistors (53) and (54) are of the same size and the two currents (47 ) and (48). The total resistance between points (45) and (50) is therefore half the resistance that would be effective in the absence of the antenna conductor (12) and the merging antenna conductor (10) if the cross-section of the two conductors in the area under consideration is not adjusted. The heating of the disc between the Points (45) and (50) is at a small distance between antenna conductor (12) and merging antenna conductor (10) because of the proportionality of the converted active power to the total resistance (55), which results from the parallel connection of (53) and (54) , also only half as large as in the absence of the antenna conductor (12) and the merging antenna conductor (10). In such an embodiment of an antenna according to the invention, there is consequently a defrosting behavior which deviates from the rest of the heating field in the area between points (45) and (50). The conductor cross section of the conductor (38) between the points (45) and (50) and the merging antenna conductor (10) is therefore cut in half more advantageously for an antenna according to the invention, a measure that is easily possible in the case of conductors printed in the screen printing process by a corresponding design of the sieve is.

If the length (52) of the antenna conductor (12) is no longer so small that the pane in the area between the points (45) and (50) is heated as if by a single conductor, the relationships are more complicated. As a rule, one will be interested in limiting the heating of the pane to the area around the heating conductor (38) and consequently striving for a dimensioning in which the heat converted via the antenna conductor (12) and the merging antenna conductor (10) remains low . This goal can be achieved by a corresponding choice of the cross sections of the antenna conductors (12) and the merging antenna conductors (10) on the one hand and the section of the heating conductor (38) between points (45) and (50) on the other hand for an antenna according to the invention.

A general analysis leads to the result that with respect to the values of the resistors (54) = R1 and (53) = R2 each refer to the resistance value (55) = R, which is the case with standard heat conductors, i.e. without the antenna conductors (12) and the connecting antenna conductor (10) between points (45) and (50) would result in the following combinations of values for the desired behavior: Table 1 R1 / R = 4th == R2 / R = 4th R1 / R = 4.5 == R2 / R = 2.6 R1 / R = 5 == R2 / R = 2nd R1 / R = 6 == R2 / R = 1.6 R1 / R = 10th == R2 / R = 1.2

For an advantageous embodiment of an antenna according to the invention, the ratio R2 / R is therefore determined according to this table for a predetermined ratio R1 / R by choosing a suitable conductor cross section in the area of the antenna conductor (12) between points (45) and (50), that is in the area the structure width (9). For example, for conductor cross sections of antenna conductors (12) and merging antenna conductors (10) similar to those for the heating conductors, the value of R1 / R = 5 is obtained when the distance (52) of the merging antenna conductors (10) to the closest and galvanically connected HL (38) is twice as large as the structure width (9) in the second area (41). To under these conditions also in the range of structure (9) To implement the same heating power per unit length as in the rest of the heating field, the DC resistance must be doubled in accordance with the table, which is advantageously achieved by reducing the cross-section by half.

A further advantageous embodiment of an antenna according to the invention without cross-sectional adaptation is possible if the strip available between the heating conductor (38) and the frame in the special vehicle window is so large that the length (52) of the antenna conductor (12) is large compared to the width ( 9) the structure in the second area (41) is selected. In this case, the ohmic resistance (54) is so large compared to the ohmic resistance (53), so that the current (47) almost corresponds to the current (46) and the current (48) is negligibly small. In the table above, this corresponds to very high values of R1 / R, for which R2 / R asymptotically approaches the value "1".

For these reasons, it is advantageous for the antenna according to the invention to arrange the merging antenna conductor (10) as close as possible to the frame, because in this way influencing the direct current flow and thus the distribution of the heating power on the pane is the most favorable. For optical reasons, it is also advantageous to arrange the merging antenna conductor (10) parallel to the heating conductors (2) or to the corresponding frame edge, ie horizontally.

In a further advantageous embodiment of an antenna according to the invention, the problems explained above are avoided in that, like galvanic connection, the antenna conductor (12) is replaced by the merging antenna conductor (10) by a connection which has no direct current passage, but for the frequencies of the useful band within a sufficiently low-impedance connection in the frequency range of the meter waves. According to Fig. 11 this can be done by capacitors (58), e.g. can be achieved by soldered chip capacitors, corresponding capacitance value.

Electrically equivalent behavior of an antenna according to the invention without influencing the heating currents through the structure of the antenna conductors (12) in the second area can also be achieved by replacing the galvanic connection between the first area and the second area by a connection, which has no direct current passage, but causes a sufficiently low-resistance connection for the frequencies of the useful band within the frequency range of the meter waves. According to FIG. 12, this can be achieved in the same way as in FIG. 11 by capacitors (58) corresponding to the capacitance value applied to the pane.

In the following, advantageous embodiments of the continuing antenna conductor (22) for antenna according to the invention.

With an antenna according to the invention, the common connection point (8) on the merging antenna conductor (10) is always in the area (42) of the pane, i.e. in a region symmetrical about the line of symmetry (3) and that with a width corresponding to half the mean pane width ( 5). For reasons of symmetry, however, an overall symmetrical structure is recommended, with the result that the connection point (8) is generally also arranged on the line of symmetry (3). If a point on the line of symmetry (3) on or near the frame (21) can also be used as the mounting point for the continuing network (16), it may still be necessary to place between the connection point (8) and the decoupling point (23 ) in the vicinity of the frame to establish a connection through the continuing antenna conductor (22), with the continuing antenna conductor (22) then also expediently likewise being arranged along the line of symmetry. Such a situation is shown in FIG. 3. If the mounting point of the continuing network (16) is not on the line of symmetry (3) of the pane, then the connection point (8) will generally also not be arranged on the line of symmetry (3) of the pane, but will be offset parallel to the line of symmetry of the pane, so that, from an optical point of view, the further antenna conductor (22) can advantageously also be routed parallel to the two lateral frame edges or the line of symmetry.

Often, however, an assembly point for the continuing network (16) in the area of the sky of a vehicle is ruled out due to vehicle-specific aspects due to the circumstances of the production sequence or because the components are difficult to reach. In such cases, it is necessary to pass on the received signal available at the connection point (8) harmlessly with respect to the received powers achieved at the connection point (8) up to the vicinity of the continuing network (16) and in the vicinity of the frame (21).

In the case of an antenna according to the invention, this object is achieved by the continuing antenna conductor (22), which generally consists of a plurality of directly interconnecting partial conductors, which for optical reasons are advantageously routed in parallel to one of the adjacent frame edges. A typical arrangement according to the invention is shown by way of example in FIG. 1, in which the further network (16) is attached in the region of the left side of the frame and the further antenna conductor (22) starting from the connection point (8) initially along the line of symmetry of the pane up to close of the frame is guided, bends at the break point (57) and is further guided parallel to the upper frame edge to the right up to the vicinity of the upper right corner to the decoupling point (23). If necessary, further inflection points (57) may also be required if the continuing network (16) is in a suitable position.

The size of the distance (60) from FIG. 1, in which the further antenna conductor (22) is routed parallel to the respective frame edge, is to be selected depending on the objective that is sought for an antenna according to the invention.

Should e.g. If a disk antenna is implemented, the behavior of which comes as close as possible to a rod antenna when the polarization changes, this distance (60) must be small, i.e. in the range of approx. 1 cm to 5 cm. With this dimensioning, with the same values of the exciting field strength on the one hand for a horizontally polarized and on the other hand for a vertically polarized wave field, there is a considerable increase in level during the transition from horizontal polarization to vertical or circular polarization in a similar order of magnitude as that of rod antennas mounted vertically on the vehicle is known here. This property results from the fact that an antenna according to the invention, which is arranged almost symmetrically in the center of the window, has this property with regard to its connection point (8) and a further antenna conductor (22) arranged at a small distance (60) (FIG. 1) from the edge of the window approximately has the character of a Line accepts into which only negligibly small signals from the receiving field couple. Therefore, the polarization behavior present at the connection point (8) can essentially also be found at the decoupling point (23).

However, this pronounced preference for the vertical field component is not always desirable, since this places particularly high demands on the reception system with regard to the intermodulation stability, especially in the vicinity of vertically polarized stations. One is therefore often interested in an antenna that delivers the same average antenna level for an incident field strength regardless of the polarization. An antenna according to the invention approaches this desired behavior when the further antenna conductor (22) is guided at a large distance parallel to the frame edges, since in this case the further antenna conductor (22) is also strongly coupled, above all, to a horizontally polarized field. Such an antenna according to the invention is shown by way of example in FIG. 13.

If an antenna according to the invention is essentially only intended for the reception of horizontally polarized waves, the distance (60) of the further antenna conductor (22) to the frame can be freely selected.

Antenna diversity systems require several antennas with different behavior with regard to reception interference. It is known that it makes sense to implement several antennas in a single vehicle window for such systems.

Two such diversity antennas can be advantageous as Antennas according to the invention are executed when the heating field is divided in the vehicle window in question. Fig. 5 shows such an arrangement, the two continuing networks (16) being attached at almost diagonally opposite points in the vicinity of the frame. Since the areas of the two antennas that are essential for reception are each arranged in the area of the vertical line of symmetry of the disk, these two antennas do not have a very distinctly different behavior in wave fields which are only slightly disturbed by multipath propagation because of their similarity of the geometries.

It is therefore often possible to achieve a greater degree of reception improvement with a diversity system with different antenna types if an antenna according to the invention is combined with another antenna type, as is shown by way of example in FIG. 14. In this case, the second signal is coupled out in a known manner on the busbar of the other partial heating field, which results in very good diversity properties.

A distinctly asymmetrical arrangement of two antennas according to the invention in a manner that is again symmetrical with respect to the line of symmetry (3) of the disk represents a further advantageous embodiment, which has the advantage of the same continuing networks (16) and is also suitable for diversity due to sufficient decoupling by the relatively large spatial distance of the respective antenna conductors (11) and (12), the two further networks (16) also being the same, with the corresponding advantages in terms of costs and simplified storage.

If there is a sufficiently large free space above or below the heating field, further diversity antennas in the vehicle window can also be combined with the antenna according to the invention in a known manner.

In a known manner, the connection between the decoupling point (23) of an antenna according to the invention and the input terminal (15) of the continuing network (16) and the connection of the other input terminal (17) of the continuing network through the conductor (32) to the ground point (39) on the metallic frame (21) as short as possible. The antenna connection point form the output terminals (18) and (19) of the continuing network (16) to which the antenna line is connected. According to known techniques, the continuing network can be implemented exclusively passively and can perform the task of adapting the power of the impedance of the unipole at the decoupling point to the characteristic impedance of the antenna line (20) by means of suitable low-loss transformation elements.

Advantageously, this further network is actively implemented to achieve the maximum possible signal-to-noise ratio, so that together with the unipole according to the invention an active antenna results, the input transistor of which is operated on the input side in noise adaptation.

If the antenna according to the invention is also to be used as a radio reception antenna for the frequency range LMK, then in an advantageous further embodiment an LMK structure independent of the heating field can be provided, which is attached in the area of the pane not covered by the heating field and whose decoupling point (29) is advantageously in the proximity of the decoupling point (23) of the antenna according to the invention is attached (FIGS. 6 and 13). In this case, the further network is preferably expanded by a separate amplifier with capacitively high-impedance input resistance in known technology for the frequencies of the LMK range and the decoupling point (29) of the LMK structure is connected to the LMK input (27) of the further circuit. The frequency range LMK and the meter wave range are then brought together within the advanced circuit (16) and supplied to the antenna line (20) via a crossover in a known technique.

The direct current from the on-board battery (36) is fed to the busbars (62) in the area of the pane edges, with which the heating conductors (2) and (38) are electrically combined, the negative connection of which is usually connected to the vehicle body via the connection (64) connected is. This wiring of the heating field by means of the direct current feeds (63) leads, for the frequencies of the meter wave range, on the one hand to a generally undefined alternating current load on the busbars (62) and, on the other hand, to the coupling of interference signals into the heating field, because of the direct voltage of the vehicle units of the on-board battery (36) are sometimes superimposed with significant interference signals whose spectrum extends from LF frequencies to beyond the frequency range of the meter waves.

Both disturbing influences tend to be reduced by the described decoupling of the reception zone, which acts preferentially, from the edge regions of the vehicle window. Nevertheless, in the interest of optimal functioning of the antenna according to the invention, these disruptive influences will be avoided by additional measures.

This is advantageously done with the help of the heating field networks (25), which are arranged in the direct current feeds (63) to the heating field, preferably in the vicinity of the connection points on the busbars (62).

The suppression of the interference signals superimposed on the on-board accumulator (36) is carried out simply and advantageously in the heating field networks (25) by parallel capacitors (64) connected to ground (FIG. 15) of a capacitance value that is suitable for the frequencies of the meter wave range for realizing a capacitive short circuit . In this way, a defined wiring of the busbars is also achieved, with the consequence of defined impedances of the unipole at the decoupling point (23).

Such a capacitively low-resistance load on the busbars of the heating field, as measurements show, often results in unfavorable available signal levels at the decoupling point (23) of an antenna according to the invention. Therefore, in a further advantageous development of the invention, an element (65) is connected in series in the connection between the capacitor (64) and the connection on the respective busbar (62), which element has a high impedance for the frequencies of the useful band within the meter wave range with low-resistance direct current passage Has series impedance, which means that the AC load on the busbars is sufficiently low. This series element (65) can e.g. can be realized by an air coil with high inductance and a sufficient cross-section for the heating currents in the range from 10A to 30A or by connecting a smaller air coil and a capacitor in parallel if the resulting series-connected parallel resonance circuit is dimensioned such that its resonance frequency is approximately in the middle the useful frequency range is within the meter wave range.

Claims (27)

1. antenna for the reception of meter waves in motor vehicle windows with a metallic frame in the form of an essentially vertical unipole in the region of the vertical window center,
characterized in that
there is a disc heater with essentially horizontal wire-shaped heating conductors (2) and the Unipol (1) consists of two superimposed and immediately adjacent and galvanically connected areas and the 1st area (40) in the area of the heating field and the 2nd area (41 ) is arranged in the area outside the heating field and this unipole is formed in each of the two areas arranged one above the other from one or more substantially parallel and essentially vertical antenna conductors (11) and (12) and this or these antenna conductors each in an area (12 ) of a maximum of half the average pane width (5) are arranged symmetrically to the vertical pane center (3) and this or these vertical antenna conductors (11) cross in the first area (40) at least two of the heating conductors (2) and at the crossing points ( 35) are electrically connected to the heating conductors (2) and the height of this 1st area is not less than 5cm and d This or these vertical antenna conductors (12) in the second area (41) are connected at one end to the heating conductor (38) located at the edge of the heating field in an electrically low-resistance manner for frequencies of the useful frequency range and at the other end by a merging antenna conductor ( 10) are electrically connected for low frequencies for frequencies of the useful frequency band and have a common connection point (8) on the merging antenna conductor (10) and from this common connection point a further antenna conductor (22) leads substantially parallel to the frame edges to the decoupling point (23) and this Decoupling point is arranged in the vicinity of the frame (21) and a further circuit (16) is provided, which has one input terminal (15) with the decoupling point (23) and the other input terminal (17) with the metallic frame (21 ) is connected via a conductor (32) to the ground point (39) and its output terminals (18) and ( 19) form the antenna connection point (33) to which the antenna line (20) is connected. 2. Antenna according to claim 1,
characterized in that
the wire-shaped heating conductors (2) and the antenna conductors (11), (12) and (22) are printed in a known manner on the surface of the glass of the pane. 3. Antenna according to claim 1,
characterized in that
the wire-shaped heating conductors (2) and the antenna conductors (11), (12) and (22) are inserted in a known manner as wires between the two panes of a laminated glass pane. 4. Antenna according to claim 1 to 3,
characterized in that
the number of conductors (11) in area 1 (40) is equal to the number of conductors (12) in area 2 (41) and that the conductors (11) represent the direct continuation of the conductors (12). 5. Antenna according to claim 1 to 3,
characterized in that
the merging antenna conductor (10) is arranged horizontally and parallel to the frame. 6. Antenna according to claim 5,
characterized in that
the merging antenna conductor (10) is arranged in the vicinity of the frame. 7. Antenna according to claim 5,
characterized in that
the electrically low-resistance connection is made by the connecting antenna conductor (10) by means of a galvanic connection and the distance (52) of this connecting antenna conductor (10) to the closest galvanically connected heating conductor (38) is significantly greater than the structure width (9) in the second area ( 41). 8. Antenna according to claim 5,
characterized in that
the electrically low-resistance connection is made by the connecting antenna conductor (10) by means of a galvanic connection and the distance (52) of this connecting antenna conductor (10) to the closest galvanically connected heating conductor (38) is approximately twice as large as the structure width (9) in FIG. 2 .Section (41) and the cross section of the heating conductor (38) in the region of the structural width (9) is selected to be approximately half as large as compared to the other conductors on the pane. 9. Antenna according to claim 5,
characterized in that
the electrically low-resistance connection is made through the connecting antenna conductor (10) through capacitively low-resistance connections. 10. Antenna according to claim 4 to 9,
characterized in that
the Unipol (1) is formed by two parallel antenna conductors at a distance between 1/10 and 1/30 of the mean operating wavelength and these antenna conductors are arranged symmetrically to the vertical line of symmetry of the disk. 11. Antenna according to claim 4 to 6,
characterized in that
the unipole (1) is formed by an antenna conductor, which is arranged approximately in the middle of the slide and consists of an antenna conductor (11) and (12), which merge directly into one another. 12. Antenna according to claim 1 to 11,
characterized in that
the heating field is divided into partial heating fields (30) and (31) and the Unipol (1) in the 1st area (40) is limited to one of the partial heating fields (30). 13. Antenna according to claim 1 to 12,
characterized in that
the further antenna conductor (22) is guided from the connection point (8) parallel to one of the frame edges up to the vicinity of the frame and the end of this further antenna cable forms the decoupling point (23). 14. Antenna according to claim 1 to 12,
characterized in that
the further antenna conductor (22) from the connection point (8) is guided in several directly adjoining and each aligned parallel to the frame edges and the decoupling point (23) is arranged at the end of the further antenna conductor near the frame. 15. Antenna according to claim 14,
characterized in that
the spacing of the partial conductors of the continuing antenna conductor (22) from the respective frame edges, to which these are guided in parallel, is respectively small. 16. Antenna according to claim 12,
characterized in that
there are two antennas according to the invention, each of which forms a unipole with one of the two partial heating surfaces. 17. Antenna according to claim 12,
characterized in that
the antenna according to the invention represents one of at least two diversity antennas on the vehicle window and the other antenna couples the signal to the other partial heating field in a known manner. 18. Antenna according to claim 1 to 9,
characterized in that
two antennas according to the invention are present and the antenna conductors (11) of the two antennas cross the same heating conductors (2) and (38) and the distance between the two unipoles is selected so that the maximum possible efficiency results within a diversity system. 19. Antenna according to claim 1 to 18,
characterized in that
there are other diversity antennas independent of the heating field on the vehicle window. 20. Antenna according to claim 1 to 19,
characterized in that
the secondary network (16) is only passive is executed. 21. Antenna according to claim 1 to 29,
characterized in that
the continuing network (16) is actively executed. 22. Antenna according to claim 1 to 21,
characterized in that
for the reception of frequencies of the LMK range there is a further structure (24) independent of the heating conductors and the Unipol (1), which is attached in the area of the pane not covered by the heating field and its decoupling point (29) with the LMK input (27) of the advanced circuit (16) is connected and the decoupling point (29) is adjacent to the decoupling point (23). 23. Antenna according to claim 1 to 22,
characterized in that
the heating current (26) is supplied to the heating field via heating field networks (25). 24. Antenna according to claim 1 to 23,
characterized in that
the heating field networks (25) contain elements which sufficiently prevent the interference coupling of spectral components of on-board network disturbances onto the flat antenna structure. 25. Antenna according to claim 1 to 24,
characterized in that
the heating field networks (25) contain elements by means of which the AC load on the heating field due to the supply of the heating currents for the frequencies of the respective useful band is negligible. 26. Antenna according to claim 1,
characterized in that
the conductors (11) and (12) of the unipole (1) are formed by vapor deposition of a high-frequency conductive layer and the conductivity of which is chosen to be sufficiently high-impedance that the defrosting properties do not change significantly due to the heating conductors. 27. Antenna according to claim 1 to 19,
characterized in that
there is no further network (16) and the decoupling point (23) is connected directly to (18) and (39) directly to (19).

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