EP1698019B1 - Vehicle windshield-integrated antenna - Google Patents

Description

The invention is based on a vehicle windshield antenna with a heating field, which is provided for both the FM reception and for the LMK reception.

State of the art

In vehicle antennas, the heating field of the disc is often used as an antenna structure. In the US 6,498, 588 B 1 or the WO99 / 66587 the heating field is intended for VHF and TV reception. For LMK reception in addition a conductor loop at the upper edge of the disc, which is not connected to the heating field, is provided.

A major disadvantage of such an arrangement is the need for a surface, z. B. in the upper region of the window, which is not heated due to lack of heating element and thus can not be defrosted. Especially in cars with small windows of the resulting heatable area is impermissibly small.

The heating conductors are substantially horizontal and substantially parallel to the metallic boundaries of the disc. The on-board network disturbances transmitted by the heating current to the heating conductors serving as antennas must, as is known, be suppressed by assemblies having high-frequency, high-impedance behavior if the antenna connection point is galvanically connected to the heating field. For FM / TV reception these are z. B. rod core chokes, which are integrated in the Heizstromzuführenden line parts and are usually located near the Heizstromanschlüsse the heating field.

For the LMK reception, this is a current-compensated toroidal core choke (AM blocking circuit), which is likewise arranged in the heating current supply. This AM blocking circuit is a very cost-intensive module whose own weight, approx. 200 g, leads to high mechanical loads on both the printed circuit board and the screw connection points and is thus to be regarded as extremely critical within the framework of quality assurance. The vibrations occurring under normal driving conditions cause solder joints to be heavily stressed. In compact vehicles, this AM-blocking circuit is often mounted in the rear tailgate, so that when slamming the flap accelerations of about 50 g can occur and the entire component tears off the screwing points.

In other vehicle antenna receiving arrangements, the reception of LMK and diversified VHF signals with line structures is realized in one or more but mostly in the immediate vicinity but spatially separated windows. A major disadvantage of such an arrangement is the need for at least two, usually fixed window panes, which results in an increased effort in the manufacture of the discs, in the electronic design of connected, mostly active circuit components and in the assembly of corresponding circuit carrier.

Antenna arrangements are also known which form antennas for the LMK and FM reception from the galvanically contacted heating field. Again, on-board decoupling filter elements for antenna connection point and heating conductor are necessary ( EP 0269723 B1 . EP 0382895 B1 ).

From the US Pat. No. 6,239,758 B1 is also a glass antenna within a Heizleiterfeldes as known to remove. Between a left and a right busbar parallel to each other run a plurality of heating conductors, wherein in the Heizleiterfeld in the longitudinal distance of the individual heating two antenna conductors are arranged, which are galvanically connected to the heating elements. At the upper end of the busbars also extend two heating conductors, which are arranged at a greater distance from the underlying heating conductors, whereby a large recording field is formed, in which a plurality of mutually parallel Auskoppelleiter are arranged. This can be used to decouple a radio signal for AM reception.

The signals for the FM reception are decoupled separately from a busbar and fed to a corresponding amplifier.

The from the EP 0 560 677 B1 Known pane antenna arrangement also describes that the AM radio signal and the FM radio signal are coupled separately, the Heizleiterfeld is constructed so that the individual heating conductors in parallel to each other each have a comparatively large distance, so that in the middle position to each one with the Heizleiterfeld can not be connected electrically connected antenna conductor. One of these antenna conductors is used for coupling the AM signal, whereas the other plurality of antenna conductors are galvanically coupled to one another and serve to decouple the FM radio signal.

Finally, a corresponding genus-forming glass antenna from the EP 0 639 868 A1 to be known as known. Here, a separate Heizleiterfeld is provided above which the disc has a larger space in which no heating conductors are arranged. There are a plurality of antenna wires predominantly provided in parallel to each other, running straight or as a loop to decouple here together an AM and FM radio signal.

For the capacitive coupling with the Heizleiterfeld a coupling wire is provided on the one hand, which runs parallel to an uppermost arranged heating conductor of the Heizleiterfeldes and is thus electrically coupled centrally. Due to this, no heating current flows through this coupling-out wire.

In parallel, a further antenna coupling wire is provided, which is connected centrally with other antenna wires, which lead to a decoupling member.

In particular, in such an arrangement similar to the aforementioned US Pat. No. 6,239,758 B1 is not ensured that a complete heating of the entire disc in the not covered by the black print area of the Heizleiterfeldes achievable, since correspondingly large-sized exception areas must be provided, in which Auskoppeleinrichtungen and in particular Auskoppeldrähte are arranged (which incidentally also for the EP 0 560 677 B1 applies, since instead of a respective second heating wire in Heizleiterfeld an antenna wire is used, which does not serve the heating, but only the coupling of either an AM or FM radio signal).

The object of the present invention is therefore based on the generic EP 0 639 868 A1 to provide an improved glass antenna using a Heizleiterfeldes. In this case, as in the generic state of the art, at least the FM but also the LMK radio signal should be capacitively coupled via a common decoupling element.

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

Advantages of the invention

With the measures according to claim 1, d. H. with a Heizleiterfeld, which is provided for both the FM and possibly TV reception and for the LMK reception with a single disc, wherein at least one decoupling element is provided for at least the LMK reception, which high frequency but not galvanic to the heating field is connected and wherein the decoupling element is arranged in Heizleiterfeld, in particular between two adjacent heating conductors, the reception of LMK and in particular diversified VHF / TV signals with a single window pane is possible without a complete heating of the entire disc just not through The area covered by the black printing must be dispensed with, that is to say above all a complete heating of the entire pane in that area of the heating conductor field has to be dispensed with, in which the outcoupling device is accommodated.

This results in a further advantage that in contrast to the generic state of the art, a separate connected to a heating conductor Auskoppeldraht must be provided, so what is needed space that does not serve to heat the disc, so that a principle arbitrary heating of the Heizleiterfeldes can be used to produce a capacitive coupling.

Here, in particular, the per se known advantage can be maintained that both the LMK signal and the VHF signal is coupled out via this common capacitive decoupling element, whereby a non-negligible overall simplification of the antenna arrangement can continue to be realized.

The principle according to the invention can be improved in a particularly favorable and effective manner by further using so-called "crossing lines" known from the prior art, ie antenna conductors which are provided running perpendicular to the heating conductors and are galvanically connected to the heating conductors. These additionally provided antenna conductors extending at the equipotential points ensure that a resonant structure arises at the antenna connection point, in particular for the VHF frequencies.

At the same time can be dispensed with the necessary filter elements for the LMK broadcasting or the filter elements can be constructed with significantly less effort than in previous systems. This makes it possible to dispense with a separate investigation of the occurring mechanical stress of this assembly and the quality of the system over the vehicle life are ensured with unobtrusive filter assemblies. The noise floor of the antenna for the LMK radio reception can be significantly reduced while maintaining filter elements for the LMK range.

The line structure is applied by conventional methods on a window pane, wherein it is irrelevant in the context of the invention, whether it is a window glass or laminated safety glass. Said window is surrounded by a metallic frame and usually designed as a rear window of a motor vehicle. However, the described arrangement can also be transferred to any other disc z. B. in ships.

The particular advantage of the invention is that either no special filter elements for decoupling the LMK antenna function of the electrical system disturbances in the form of a current-compensated ring choke (high-frequency technically high-resistance component) are necessary or the noise floor with LMK reception can be significantly reduced if filter elements for the LMK reception are maintained.

It is in addition to serving for defrosting heaters only a decoupling preferably an additional conductor or an additional conductor loop so in particular between two parallel heating conductors, usually between the top two, because the technical performance of the receiving system is optimal, inserted that no galvanic Connection between this conductor and the heating field exists.

Due to the non-galvanic connection, vehicle electrical system interference has a small influence on the noise floor of the antenna. The capacitive coupling between the heating field and the additional conductor is so low for LMK frequencies that vehicle electrical system disturbances in the heating current do not crosstalk or only to a small extent. However, the capacitive coupling for VHF and TV frequencies is sufficiently high that the antenna signals are received with the entire heat conductor structure. Here filter elements are necessary. Due to the high capacitive coupling, the antenna function is comparable to an arrangement in which the antenna connection point is galvanically connected to the heating field. In addition, the entire pane is heated, since no structures outside the Heizleiterfeldes are necessary.

Another advantage of the embodiment of the invention is the cost-effective production. Over other Embodiments, only a single disc needs to be formed. Another advantage is the integrated and thus simple construction of passive or active circuit parts, which, although separate signal paths for the different frequency bands, but can be arranged in a single housing. This results in a minimum of mechanical components as well as minimal wiring.

drawings

Figur 1:

ein integriertes Antennensystem für LMK-, UKW- und gegebenenfalls TV-Empfang nach der Erfindung,

Figur 2:

ein weiteres Ausführungsbeispiel mit einer weiteren UKW-/ TV-Antennensignalauskopplung,

Figur 3:

einen Vergleich des Empfangspegels im LMK-Frequenzbereich.

With reference to the drawings, embodiments of the invention will be explained. Show it

FIG. 1:

an integrated antenna system for LMK, FM and possibly TV reception according to the invention,

FIG. 2:

a further embodiment with a further FM / TV antenna signal extraction,

FIG. 3:

a comparison of the reception level in the LMK frequency range.

Description of exemplary embodiments

FIG. 1 shows a glass antenna consisting of mutually parallel heating conductors 3, each open at their left and right ends in a busbar 4. The Heizleiterfeld thus formed is each supplied via a FM / TV throttle 5 in the supply lines with heating (Ub heater). Depending on the acceptance of the noise floor is provided in the leads for the heating current, an AM blocking circuit 13 with more or less complex filter effort or not. The antenna connection point 1 for FM / TV and LMK signals is galvanically connected to a decoupling element 6 in Heizleiterfeld but not with the Heizleiterfeld. The decoupling element 6 can be used as a rectilinear conductor, as an open conductor loop as in FIG. 1 represented, or be designed as a closed conductor loop or combinations of the latter elements. The longest possible structure is advantageous. The decoupling element 6 is arranged in particular between two adjacent heating conductors 3 and extends parallel (legs of the open conductor loop) to the entire length of two heating 3. The distance of the decoupling element 6 and its conductor pieces parallel to the heating conductors 3 should be as low as possible, so that capacitive coupling for FM / TV frequencies is ensured. The ground point 9 for the connection of the active antenna assembly 7 is advantageously located in the immediate vicinity of the antenna connection point 1 in the upper right corner of the Heizleiterfeldes on the surrounding the window pane metallic frame 8 (shown in phantom).

The heat conductor structure of the disc is formed, for. B. by additional vertical crossing lines 10, which are connected at each intersection with the galvanic parallel heating conductors 3 and are on the forming by the voltage distribution equipotential points, that at the antenna connection point 1 for VHF frequencies, a resonant structure is formed.

In the electronic module 7, the decoupled antenna signals are amplified separately (AM, FM, TV 1) and optionally filtered and supplied to the TV tuner 11 and radio 12.

FIG. 2 shows a further embodiment in which a further FM / TV antenna signal decoupling from the galvanically connected to the heating field on the opposite side antenna connection point 2 and a closely adjacent ground terminal is formed. This is then a two-antenna system is formed. It can be formed in the same place from the heating field at other locations even more antennas, z. For example, there are two more to generate a four-antenna system. It can be covered with another FM or TV area, a second VHF receiver to be operated or a diversity effect can be exploited by different received signals at the two antenna connection points 1 and 2, as he z. B. under unfavorable reception conditions in mobile use can come about.

Another advantage of the invention is clear at this point: When LMK reception is crucial to the capacity of the antenna conductor relative to the vehicle mass. In the prior art system, in the two-antenna system, by connecting a second electronic subassembly having a certain input capacitance, the overall capacitance of the device relative to the antenna port 1 is increased. In other words, a portion of the received LMK signal is grounded through the second assembly, degrading overall reception. This circumstance is prevented in the antenna arrangement according to the invention.

Measurements show that the reception of LMK signals with the inventive arrangement according to FIG. 1 is comparable to a system in which the antenna connection point is galvanically connected to the heating field at the upper outer corner. It also turns out that an open conductor loop as in FIG. 1 presented the best results achieved. Although the reception level is slightly lower, but a lower background noise is generated by the heating current.

The reception performance for FM / TV reception is comparable to known arrangements.

Claims (6)

1. Vehicle window antenna comprising the following features:

   - a heat conductor field which is intended at least for VHF reception and LF, MF and HF reception,

   - the heat conductor field comprises a plurality of heat conductors (3), by means of which the entire window in the region not covered by the black print can be completely heated,

   - at least one decoupling element (6) which is intended at least for LF, MF and HF reception and VHF reception,

   - the decoupling element (6) has a high-frequency yet non-galvanic connection to the heat conductor field,

   - the decoupling element (6) is designed as a linear conductor and/or as an open conductor loop and/or as a closed conductor loop,

   - the decoupling element (6) is arranged next to the heat conductor field so as to produce a capacitive coupling, for very high frequencies, to the heat conductor,

   characterised by the following additional features:

   - the decoupling element (6) is arranged next to a heat conductor (3) such that a capacitive coupling is produced at least for the very high frequency,

   - the decoupling element (6) is furthermore arranged, in this case, in the heat conductor field between two adjacent heat conductors (3), and

   - antenna conductors (10) are arranged in the heat conductor field so as to extend perpendicularly to the heat conductors (3) and are galvanically connected to the heat conductors (3).
2. Vehicle window antenna according to claim 1, characterised in that the decoupling element (6) is also intended for VHF reception and optionally for TV reception.
3. Vehicle window antenna according to claim 2, characterised in that an FM choke/TV choke (5) is provided in the heating circuit.
4. Window antenna according to claims 1 to 3, characterised in that the length and/or position of the antenna conductors (10) is designed such that resonance-like behaviour of the antenna occurs at the connection end (1) of the decoupling element (6) in the VHF range.
5. Vehicle window antenna according to any of claims 1 to 4, characterised in that the ground point (9) for decoupling the LF, MF and HF or VHF/TV antenna signals is arranged near to the connection end (1) of the decoupling element (6).
6. Vehicle window antenna according to any of claims 1 to 5, characterised in that at least one additional VHF/TV antenna signal decoupling means is provided, which is in particular galvanically connected to the heat conductor field, preferably to the busbar (4) which is remote from the connection end (1) of the decoupling element (6).

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