EP0155647B1 - Antenna arrangement in the rear window of a car - Google Patents

Antenna arrangement in the rear window of a car Download PDF

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Publication number
EP0155647B1
EP0155647B1 EP85102985A EP85102985A EP0155647B1 EP 0155647 B1 EP0155647 B1 EP 0155647B1 EP 85102985 A EP85102985 A EP 85102985A EP 85102985 A EP85102985 A EP 85102985A EP 0155647 B1 EP0155647 B1 EP 0155647B1
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EP
European Patent Office
Prior art keywords
aerial
vhf
short
heating
aerial array
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EP85102985A
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German (de)
French (fr)
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EP0155647A3 (en
EP0155647A2 (en
Inventor
Heinz Lindenmeier
Gerhard Flachenecker
Jochen Hopf
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CAMBIO RAGIONE SOCIALE;FUBA HANS KOLBE & CO.
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HANS KOLBE AND Co
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Priority to DE19843410415 priority patent/DE3410415A1/en
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q23/00Antennas with active circuits or circuit elements integrated within them or attached to them
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00Details of, or arrangements associated with, antennas
    • H01Q1/12Supports; Mounting means
    • H01Q1/1271Supports; Mounting means for mounting on windscreens
    • H01Q1/1278Supports; Mounting means for mounting on windscreens in association with heating wires or layers

Description

  • The invention relates to an antenna arrangement according to the preamble of claim 1.
  • With such antennas, it is necessary to design both the LMK reception and the FM reception as well as possible and the coupling of high-frequency interference e.g. prevent from the vehicle electrical system.
  • In EP-A-65263 an antenna arrangement according to the preamble of claim 1 is known. There is shown in Fig. 2 an antenna arrangement in the rear window of a motor vehicle with a heating field therein with the busbars and direct current supply. In the upper area of the rear window, which is not covered by the heating field, there is a rectangular, that is to say area-shaped Antenna conductor attached, which is also intended for the reception of the LMK signals and is referred to as the main antenna. This antenna conductor is not galvanically connected to the heating field.
  • Another antenna arrangement of this type is known, for example, from DE-PS 26 50 044. In this antenna, the heating field serves as an antenna for receiving the LMK and VHF signals. A particular problem here is the direct current supply for the heating field. Particularly in the LMK area, in which the heating field forms a high-resistance antenna element due to the low frequency, the supply of the large direct currents necessary for heating the field is always with a considerable damping of the Receive signals connected. According to the invention specified there, the heating currents are supplied via a bifilar throttle, this throttle being connected in parallel with the antenna element with respect to the high-frequency signals. Especially at low frequencies, it is not possible to make the reactance of this choke wide enough for the LMK range so that the parallel connection of this element to the antenna does not noticeably impair the received signal. In the VHF range, in which the heating field forms a significantly lower-resistance antenna element, the throttling of the direct current supply can be carried out much more easily and without great technical effort.
  • In contrast to the LMK range, reception for VHF signals with an antenna described in DE-PS 26 50 044 is sufficient.
  • Another disadvantage of this antenna according to the prior art is the large interference coupling into the receiver input, especially at low frequencies. These high-frequency disturbances are caused by the electrical units in the vehicle, such as ignition and injection pulses. Since in an antenna according to DE-PS 26 50 044 the antenna element is connected both to the receiver input and, when the rear window heating is switched on, to the high-frequency disturbed DC voltage supply, screening measures in the DC voltage supply are highly effective, especially for the low-frequency LMK, to avoid reception interference - Area required. The technical effort for this screening is considerable due to the high heating currents (up to approx. 30 A).
  • A similar antenna is known from DE-OS 23 60 672 . This has similar disadvantages.
  • The object of the invention is therefore to provide good reception properties in an antenna according to the preamble of claim 1 both in the VHF range and in the LMK range and thereby the effort required to screen the low-frequency interference in the heating circuit is as low as to keep possible.
  • This object is achieved by the features specified in the characterizing part of claim 1.
  • Further features, advantages and details of the invention result from the claims and the following description. The invention is illustrated and described in more detail below with reference to drawings of exemplary embodiments. Show it:
    • Fig. 1 shows schematically as a circuit diagram the basic principle of an antenna according to the invention with the decoupling of the FM signals on the heating field;
    • 2 shows schematically as a circuit diagram an active antenna according to the invention with an LMK antenna conductor arranged centrally in the free area between the heating field and the edge of the pane;
    • Fig. 3 is a plan view of the approximation of the planar design of the LMK antenna conductor
      • a) by a lattice structure or
      • b) by several parallel conductors;
    • Fig. 4 shows schematically as a circuit diagram the basic principle of an antenna according to the invention with the decoupling of the FM signals on the LMK antenna conductor
      • a) with capacitive coupling or
      • b) with transformer coupling;
    • Fig. 5 shows schematically as a circuit diagram the supply of the direct current to the heating field used as an FM antenna conductor via reactance circuits with direct current passage
      • a) to the busbar to which the VHF signal path 13 is connected via the connection point 19, or
      • b) also on the other busbar;
    • Fig. 6 Generation of the high impedance series impedance for the FM range in the direct current supply
      • a) by inductors or
      • b) by parallel resonance circuits, these in
      • c) with additional capacitor;
    • 7 shows schematically as a circuit diagram the inclusion of the reactance circuit for supplying the direct current to the heating field in the transformation circuit in the VHF signal path 13;
    • 8 schematically shows as a circuit diagram the high-frequency separation of the heating field from the direct current supply for the LMK frequency range by means of a bifilar wound coil 30;
    • 9 shows an LMK equivalent circuit diagram;
    • 10 shows a diagram of the dependence of the antenna capacitance Ca on the relative width b / h of the planar antenna structure (measurement curves) for different heights h of the free field between the heating structure and the edge of the pane;
    • 11 shows a diagram of the dependence of the effective height heff of the LMK antenna on the relative width b / h (measurement curves);
    • 12 shows a diagram of the signal voltage Ue at the input of the LMK amplifier as a function of the relative width b / h with a heating field grounded for the LMK area.
  • The advantages achieved by the invention are, in particular, better LMK reception and a reduction in the interference which are coupled into the receiving system via the direct current supply. Due to the galvanic separation of the LMK antenna conductor 3 from the heating field 2, a high-frequency separation of the heating field from the vehicle body is generally not necessary, as a result of which the effort associated with the introduction of a bifilar throttle can be avoided.
  • In an active antenna according to the invention, it is necessary to optimally use the remaining area not covered by the heating field, which usually has the shape of a rectangle with a long and a narrow side, for the optimization of the LMK reception such that for a given input capacitance of the LMK amplifier, the signal voltage becomes maximum. This optimization is based on the following dimensioning principle:
  • In the LMK range, the antenna can be described as a source with a capacitive internal resistance 1 / Ca in series with a frequency-independent source voltage E * heff. If the capacitance of the connection between the antenna conductor and the LMK amplifier input is neglected, this antenna capacitance is loaded with the total input capacitance Cv of the antenna amplifier at input 5, as shown in FIG. 9. For a given internal noise voltage Ur of the amplifier, the minimum field strength Eg required for a signal-to-noise ratio of 1 must be shown as follows:

    Eg = (1 + Cv / Ca) * Ur / heff (1)
    Figure imgb0001


  • For other field strengths E, the resulting signal-to-noise ratio is E / Eg and can be represented as follows:

    E / Eg = E * heff / (Ur * (1 + Cv / Ca)) = Ue / Ur (2)
    Figure imgb0002


  • Ue designates, according to FIG. 9, the input voltage of the LMK amplifier for a given signal field strength E. In the interest of the greatest possible sensitivity, the limit field strength Eg should be as low or the control voltage Ue should be as large as possible for a given field strength E. This is brought about by the largest possible effective height heff and the largest possible capacitance Ca with the lowest possible input capacitance Cv.
  • In the following, the optimization of the sensitivity for the case of a heating field that is earthed by the LMK is considered. The heating field is therefore directly connected to the direct current supply without any further measures. The edges of the free area on the rear window that is not covered by the heating field are therefore all at ground potential.
  • For reasons of symmetry, maximum effective height is achieved if an elongated antenna conductor is attached halfway between the edge of the heating field and the edge of the pane, that is to say in the middle, if the distances ak and ah are chosen to be the same size and the same as a in FIG. 2. The distance as on the narrow side of the antenna structure is also expediently to be chosen equal to a. In the interest of the largest possible antenna capacity, the LMK antenna conductor 3 is to be made flat with the largest possible width and length dimension. This dependency of the antenna capacitance Ca on the relative width of the antenna structure b / h is shown in FIG. 10 (measurement curves), the parameter "h" in FIG. 2 denoting the width of the field for the disk boundary not covered by the heating structure and the width b being the same b = (h-2a)
    Figure imgb0003
    results. Measurement curves for three typical cases are shown, namely for h = 20cm, h = 12cm and h = 6cm.
  • In contrast to the increase in antenna capacity Ca increases the effective height of the antenna structure with increasing values of b / h from (Fig. 11, measurement curves). The normalization height href in FIG. 11 is chosen arbitrarily.
  • For the control voltage Ue at the input of the LMK antenna amplifier 6, there are curves as shown in FIG. 12 using equation (2). The maximum achievable control voltage increases with increasing width h of the rear window field which is not covered by the heating field. Regardless of the absolute width h, however, a maximum Uemax of the control voltage Ue results for the same value of b / h = (b / h) opt. (b / h) opt, however, depends on the input capacitance Cv of the LMK antenna amplifier 6. The approximately parabolic characteristic of the curves Ue / Uref as a function of b / h can be with good accuracy in the range by the following equation 5pF <Cv <100pF
    Figure imgb0004
    and 0.05 <b / h <0.95
    Figure imgb0005
    to be discribed:

    Ue / Uemax in dB≈- 17 * [b / h - 0.3 - 0.1 * ld (Cv / 10pF)] ² (3)
    Figure imgb0006


  • ld:
    Base logarithm 2.
  • Uemax is the maximum value of the respective curve. To achieve this maximum, b / h should be dimensioned as follows:

    (b / h) opt≈0.3 + 0.1 * ld (Cv / 10pF) (4)
    Figure imgb0007


    (4)
    Since b = h - 2a holds
    Figure imgb0008
    , (4) can also be used to determine the optimal distance between the flat antenna structure and the conductive boundary:

    aopt≈h / 2 * [0.7 - 0.1 * ld (Cv / 10pF)] (5)
    Figure imgb0009


    (5)
    can be specified.
  • The dimensions of the heating field and the position in the rear window of vehicles are determined from a vehicle-specific point of view. As a rule, there is only a narrow free area available for housing the LMK antenna structure, so that it is absolutely necessary to use every possible dB value for signal-to-noise ratio improvement. In addition to the optimization of the width b or the distance a according to the invention, this also requires the use of an LMK antenna amplifier with a small total input capacitance Cv and the avoidance of additional capacitive loads. The connecting line between the connection point 4 on the LMK antenna structure 3 and the input 5 of the LMK antenna amplifier 6 should therefore be as short as possible.
  • As can be seen in FIG. 12, with increasing width h of the strip available between the heating field 2 and the pane edge 1 for the introduction of the LMK antenna structure 3, the signal voltage Ue becomes larger and therefore the limiting field strength Eg becomes lower, with an optimal design according to the invention higher signal-to-noise ratio in the current reception case. In the interest of a high limit sensitivity, it is therefore preferable for vehicle rear windows which have a free strip both above and below the horizontally oriented heating field, the free area with the larger width h with similar length dimensions for the installation of the LMK antenna structure 3.
  • In practice, the flat LMK antenna conductor 3 can be realized, for example, by vapor deposition of a thin metal layer that hardly impairs the view. In the case of rear windows, the heating field 2 of which consists of thin wires between the two glass layers of a laminated glass pane, the LMK antenna structure 3 between the two glass layers is also preferred embed and simulate the areal behavior, for example by means of a lattice structure (FIG. 3a) or by arranging several parallel wires (FIG. 3b), in order to approximate the maximum achievable capacity of the antenna.
  • The majority of heated vehicle rear windows are realized using the screen printing process with subsequent galvanic reinforcement of the conductors on single-pane safety glass. In the manufacturing steps required here, it is possible with almost no additional effort to print the LMK antenna structure 3 required for an active antenna according to the invention simultaneously with the heating field 2 on the pane. In terms of electrical behavior, the printed structure of a wire structure of the same geometry is equivalent.
  • The horizontal dimension of conventional car rear windows is approx. 1/2 wavelength for frequencies in the FM range. Accordingly, in the case of an LMK structure according to FIG. 3a or, if the conductors on the side opposite the connection point 4 are short-circuited by the connection 29 (reactance circuit), there is also the danger for FMW resonance currents in the LMK for structures according to FIG. 3b Structure due to the associated losses would have a negative impact on the performance of the active LMK FM antenna in the FM range. It is therefore expedient to design the structure 3 as in FIG. 3b and not to conductively connect the individual conductors to one another on the side opposite the connection point.
  • Compared to an antenna according to DE-PS 26 50 044, electrical isolation of the LMK antenna structure 3 and heating field 2 leads to a considerably lower interference coupling to the antenna, which in the case of an antenna according to the invention only has the small capacitance between heating field 2 and antenna structure 3 is done. Accordingly, the Sieving effect of LMK frequencies effective sieving circuits in the direct current feeds to the heating disc have significantly lower requirements than with an antenna according to the prior art. This is accompanied by the advantage of a significantly lower technical outlay.
  • In an antenna according to the invention, the input of the separate VHF signal path 13 is either connected to the connection point 19 on one of the busbars 24 of the heating field 2 (FIG. 1) or the VHF signal is also tapped at the LMK antenna conductor (FIG. 4a , b). The ground connection 22 of the antenna amplifier 23 is to be connected in the vicinity of the connection point 19 or 4 to the conductive border 1 of the rear window, as a result of which defined VHF properties and impedances are achieved.
  • An advantage of coupling the VHF signal path 13 to the heating field 2 is the fact that the heating field is "strongly" coupled to the VHF wave field due to its large area and also has a broadband, comparatively low-impedance that can be transformed with little loss. These properties generally enable very good reception properties to be achieved.
  • On the busbar 24, in addition to the VHF connection point 19, there is also the direct current supply for the window heating which, because of its low-impedance VHF impedance, which is parallel to the impedance of the heating field, represents a considerable damping of the heating field. This is accompanied by a noticeable loss in signal-to-noise ratio. In the interest of good reception properties, it is therefore advantageous, in the case of such an embodiment of an antenna according to the invention, to insert a circuit 28 composed of reactances in the direct current feed 26 to the busbar 24, which circuit for the frequencies of the VHF range in comparison to the impedance of the heating structure 2 is high impedance (Fig.5a).
  • Such a high impedance FM impedance can e.g. can be realized by a series inductance (Fig. 6a). However, due to the inductance required, a significant number of turns are required for this coil, and because of the high heating power for vehicle rear windows, usually 150-200 watts and in special cases up to 350 watts, a large wire cross-section must be used to avoid unacceptable losses Avoid heating power. This often leads to unacceptable dimensions of this coil.
  • The required high-impedance VHF impedance can advantageously be achieved by giving the reactance circuit 28 a resonance character, in that a coil 16, which is significantly smaller in terms of the inductance value and thus also geometrically smaller, is supplemented by a capacitor 17 connected in parallel to form a parallel resonance circuit (FIG. 6b). Expediently, a frequency of the VHF band, preferably in the middle of the band, is selected as the resonance frequency, as a result of which the best possible decoupling of the antenna heating structure 2 from the direct current supply is achieved with a given inductance, or the required resonance reactive resistance can be made as small as possible, on the one hand, by none to receive significant attenuation of the VHF signals and, on the other hand, to have to accept the lowest possible loss of heating power.
  • In order to prevent reception interference in the VHF band caused by high-frequency interference signals superimposed on the heating direct current, screening measures for VHF frequencies in the direct current supply may still be necessary. In the simplest case, the reactance circuit 28 must be supplemented by a capacitor 18, which is connected to the series inductance terminal facing away from the busbar 24 (Fig. 6a) or the series parallel circuit (Fig. 6b) is to be switched to ground and short-circuits the interference signals of the FM band (Fig. 6c).
  • Frequently, the reception results in the VHF band are not yet sufficient if such a reactance circuit 28 is only installed in the direct current supply to the busbar 24 and the other busbar has a low-impedance AC voltage to ground potential. In an advantageous embodiment of the invention, therefore, the heating direct current is also supplied to the other busbar 25 of the heating field 2 via a reactance circuit 29 (FIG. 5a) (direct current supply 27), which generally leads to an improvement in the mean signal-to-noise ratio.
  • It is advantageous to construct this reactance circuit 29 in the same way as the corresponding circuit 28. Because of a comparatively high-impedance VHF impedance, which is then switched on in both direct current feeds (26, 27), the entire heating field 2 is thus separated from the direct current feed in terms of alternating current.
  • In many cases, in the interest of a good VHF signal-to-noise ratio, it is also advantageous not to either connect the busbar 25 to ground potential with a low impedance or to isolate it with VHF frequency, but to switch it to ground with a reactance such that Impedance of the heating disc with a capacitive component of this reactance inductively and with an inductive component of the FM impedance of the heating disc this reactance has capacitive behavior for FM frequencies in such a way that the circuit in the vicinity of the FM frequency range has a resonance character.
  • The technical effort associated with the need for one or both DC power supplies for that Heating field reactance circuits can be avoided if the input of the VHF signal path 13 is not connected to one of the busbars 24, 25 of the heating field, but is coupled to the LMK antenna conductor 3, which is also excited by the VHF field. This coupling can take place, for example, capacitively (FIG. 4a), the capacitance Ck = 20 connected in parallel with the LMK amplifier 6 inevitably contributing to an increase in the total input capacitance Cv. It should therefore be chosen as small as possible so that the LMK reception is not noticeably impaired.
  • This additional capacitive load on the LMK amplifier 6 can advantageously be avoided by a transformer coupling 21 to the VHF antenna conductor (FIG. 4b). Considerations for the implementation of such a transformer 21 are e.g. shown in DE-OS 23 10 616.
  • The use of the flat antenna conductor structure 3 also for VHF reception also leads to good reception results if VHF signals which are radiated horizontally polarized are to be received. For applications in which the antenna is to receive FM or FM signals radiated on the transmitter side (USA), an antenna according to the invention provides significantly better reception results by coupling the FM signal path 13 to the heating structure 2 than when coupling it to the the structure used the LMK frequencies, whose transverse dimensions are generally significantly smaller than that of the heating structure. It can be seen in principle that antenna structures with pronounced dimensions in the vertical direction are advantageous for the reception of vertical field components in the VHF range.
  • The VHF signal path 13 in an antenna according to the invention can either contain only low-loss passive components or can additionally contain an amplifier circuit.
  • It is advantageous to design the VHF signal path 13 in the antenna amplifier 23 as an active antenna, since a significantly better signal-to-noise ratio is then achieved in the overall system compared to an exclusively passive version of 13. For this purpose, it is necessary to adapt the amplifier stage to the source impedance of the VHF antenna structure with respect to optimizing the signal-to-noise ratio by means of a low-loss transformation circuit and to arrange the amplifier in the immediate vicinity of the antenna connection point on the antenna conductor. This possibility of increasing the average signal-to-noise ratio is always advantageous if the performance of the passive antenna structure compared to a reference antenna, e.g. the standard rod antenna, is not sufficient. Another low-loss transformation circuit at the output of the active element in the VHF signal path 13 enables power adjustment for the VHF band to the characteristic impedance of the connecting cable to the receiver.
  • If the passive VHF structure has sufficient performance, it is advantageous in the interest of an economical solution if the signal path 13 contains only low-loss passive transformation elements for matching the impedance of the VHF antenna structure to the cable impedance.
  • In the case of an antenna according to the invention, in the case of a planar antenna structure 3 used jointly for the LMK and VHF frequency range, the connection point 4 can be attached at any point on the structure, for example on the vertical line of symmetry 30 as close as possible to the conductive edge of the pane. However, it is generally more advantageous if the connection point 4 is attached to the right or left narrow side of the planar structure 3, as a result of which a shorter connecting cable to the receiver can be used, and also in the vicinity of the narrow sides of the structure 3 there are usually good possibilities for accommodating the antenna amplifier 23 in the spar of the vehicle (FIG. 2).
  • If the heating structure 2 is used for VHF reception, it is advantageous to arrange the connection points 4 and 19 at adjacent points of the planar antenna structure 3 and the heating structure 2 in each case in the vicinity of the window edge 1, that is to say on the right or left narrow side of the rear window (Fig. 1). As a result, short connections between 4 and 6 or 19 and 13 are possible. The LMK antenna amplifier 6, the VHF signal path 13 and the crossover 11 can be accommodated in a single housing of the antenna amplifier 23, and the common ground point 22 of the antenna amplifier 23 can also be attached in the vicinity of the connection points 4 and 19 on the conductive window edge .
  • In some cases, the distance between the heating field 2 and the pane edge 1 is too small to cause a sufficiently small minimum field strength (FIG. 12). A reduction in the width h of the free stripe from 20 cm to 6 cm with optimal dimensioning according to the invention leads to a signal-to-noise ratio in the LMK range which is about 10.5 dB worse. In such cases, an improvement in the limit sensitivity can be achieved if the heating field 2 is also insulated from the direct current supply 26, 27 with high frequency in the LMK range, as can be done, for example, with the aid of a bifilar throttle 30 according to FIG. 8. In this case, the heating field 2 carries an LMK-frequency signal voltage with respect to the body surrounding it. The equivalent circuit diagram of the antenna with amplifier in FIG. 9 remains unchanged. The minimum limit field strength Eg is now not achieved for the same distances ak and ah (FIG. 2). Due to the reception contribution of the heating field 2 and its capacitive coupling to the LMK antenna conductor 3, Eg minimizes the minimum field strength or maximizes the voltage Ue a significantly smaller distance ah to the heating field 2 than to the conductive pane edge 1 (ak) optimal.

Claims (20)

  1. Aerial array for long-, medium- and short-wave and VHF radio reception in the rear windscreen of a motor vehicle with a heated area located therein provided with a bus bar on each of its sides, a direct current feed and a rectangular two-dimensionally formed aerial conductor not connected electrically to the heated area for the reception of long-, medium- and short-wave signals, which is arranged in the part of the rear windscreen not covered by the heated area,

    characterised in that the connection (4) of the aerial conductor (3) is connected to the input terminal (5) of a low-noise linear long-, medium- and short-wave amplifier (6) contained in an aerial amplifier (23) with a capacitively high-resistance input resistance via so short a supply lead and the earth connection (22) of the aerial amplifier (23) is likewise connected to the conductive edge of the rear windscreen via so short a lead that an active long-, medium- and short-wave aerial with an integral amplifier is formed, that moreover the distances of this aerial conductor (3) with the transverse dimensions (b) from the edge of the windscreen and from the heated area are so calculated that the amplifier input signal is at a maximum, and that the output signal of the long-, medium- and short-wave amplifier (6) is supplied to the first input (10) of a separating filter (11) in the aerial amplifier (23) and the aerial connecting point (12) is formed by the output of this separating filter, that in the aerial amplifier (23) a separate signal path (13) for VHF signals is present, this signal path on the input side
    a) either being connected to the point of connection (19) on a bus bar (24) of the heated area (2) and a reactance circuit (28) being inserted in the direct current feed of this bus bar (24) or a reactance circuit (28, 29) being inserted into each of the direct current feeds of both bus bars (24, 25) with direct current throughput, or
    b) the VHF signal path (13) on the input side being coupled to the long-, medium- and short-wave aerial conductor,
    and that the output signal of the VHF signal path (13) is supplied to the second connection (14) of the separating filter (11).
  2. Aerial array according to claim 1, characterised in that, in the case of horizontally formed heating conductors (2), the two-dimensionally formed aerial conductor (3) with the transverse dimensions b in the trapezoidal free area with the height h above or below the heated area (2) is mounted central to the vertical bisecting line of the rear windscreen (1) and the three distances ak between the bounds of the two-dimensionally formed aerial conductor (3) and the edge of the windscreen, ah between the said bounds and the heated area (2) and as between the said bounds and the lateral edge of the windscreen are respectively commensurate and at a preset input capacitance Cv of the aerial amplifier (23) in the range 5 pF ≦ Cv ≦ 100 pF
    Figure imgb0013
    Figure imgb0014
    and if the reactance circuit or reactance circuits (28 and/or 29) does not or do not effect any alternating current isolation from the vehicle body for frequencies of the long-, medium- and short-wave range, (Fig. 2) are dimensioned virtually as per the following equation:

    ak = ah = as = a≈h/2 * [0.7 - 0.1 * ld (Cv/10pF)]
    Figure imgb0015
  3. Aerial array according to claim 1, characterized in that the direct current feed (26, 27) is effected via a choke (30) of bifilar design with high resistance for signals of the long-, medium- and short-wave frequency range and the distance ah between the heated area (2) and the edge of the two-dimensionally formed long-, medium- and short-wave aerial structure (3) are2) chosen so as to be markedly smaller than the distance ak between the metallic edge (1) of the heated windscreen and the long-, medium- and short-wave aerial structure (3) and due to this the long-, medium- and short-wave amplifier signal is maximized (Fig. 8).
  4. Aerial array according to claim 2, characterised in that, where there are free surfaces above and below the heating structure (2), the long-, medium- and short-wave aerial conductor (3) is accommodated in the area in which the available height h is greater.
  5. Aerial array according to claims 1 to 4, characterised in that the two-dimensionally formed aerial conductor (3) is realized by means of a wire structure with a lattice character (Fig. 3a).
  6. Aerial array according to claims 1 to 4, characterised in that the two-dimensionally formed aerial conductor (3) is realized by means of a wire structure with several conductors parallel to one another, the point of connection (4) lies on a short side of this structure and the conductors on the side opposite the point of connection (4) are not connected to one another so as to be electrically conductive (Fig. 3b).
  7. Aerial array according to claims 5 and 6, characterised in that the wire structure is formed by conductors printed onto the windscreen.
  8. Aerial array according to claims 1 to 7, characterised in that in case a of claim 1 the input of the signal path (13) for VHF signals is connected to the point of connection (19) on the bus bar (24) of the heated area (2) via as short a connection as possible (Fig. 1) and that the heating direct current is supplied to this bus bar via a reactance circuit (28) with high-resistance impedance in the VHF range.
  9. Aerial array according to claim 8, characterised in that the high-resistance impedance in the reactance circuit (28) is produced by a series inductor (Fig. 6a).
  10. Aerial array according to claim 8, characterised in that the high-resistance impedance in the reactance circuit (28) for the VHF range is formed by a parallel resonant circuit connected in series to the direct current supply (26) to the bus bar (24), this circuit consisting of an inductor (16) and a capacitor (17) connected in parallel and its resonant frequency lying in the VHF range and its resonance reactance being sufficiently great, so that the damping of the received signal for all VHF frequencies is not of any consequence (Fig. 6b).
  11. Aerial array according to claim 9 or 10, characterised in that an additional filter capacitor (18) is used, which is connected between the connection of the parallel resonant circuit consisting of (16) and (17) turned away from the bus bar (24) and earth and the value of which is selected such that it is low-resistance in the VHF range in terms of alternating current (Fig. 6b).
  12. Aerial array according to claims 8 to 11, characterised in that the direct current feed (27) to the other bus bar (25) for VHF is connected directly to earth.
  13. Aerial array according to claims 8 to 11, characterised in that the heating direct current is supplied also to the other bus bar via a reactance circuit (29) with high-resistance impedance in the VHF range and the heating structure is high-frequency isolated by this from the direct current feed (Fig. 5a).
  14. Aerial array according to claims 8 to 11, characterised in that the heating direct current is supplied via a reactance circuit (29) to the other bus bar (25) also and in the case of a capacitive component of the VHF impedance of the heating structure (2) this reactance circuit exhibits inductive behaviour, and in the case of an inductive component of the VHF impedance of the heating structure (2) this reactance circuit exhibits capacitive behaviour in the VHF range, such that in the VHF range the overall circuit has a resonant character.
  15. Aerial array according to claims 1 to 7, characterised in that in case b of claim 1 the input of the signal path (13) for VHF signals is connected capacitively to the two-dimensionally formed aerial conductor (3) and thereby the coupling capacitance (20) is chosen so as to be so small that long-, medium- and short-wave reception is not adversely affected by the increase in the total input capacitance Cv due to the capacitive loading (Fig. 4a).
  16. Aerial array according to claims 1 to 7, characterised in that in case b of claim 1 the input of the signal path for VHF signals is connected with the aid of a transformer (21) to the two-dimensionally formed aerial conductor (3) (Fig. 4b).
  17. Aerial array according to claims 8 to 16, characterised in that the signal path (13) for VHF signals contains exclusively low-loss passive transformer circuits, which are constructed such that impedance matching to the aerial lead in the VHF range exists in a known manner at the output of the separating filter.
  18. Aerial array according to claims 8 to 16, characterised in that the signal path (13) for VHF signals contains an amplifier circuit and before its input a low-loss passive transformer circuit, which effects noise matching for the VHF range and a further low-loss matching circuit is present at the output of the amplifier, so that at the output of the separating filter (11) impedance matching to the aerial connection lead exists.
  19. Aerial array according to claims 8 and 10 to 17, characterised in that in case a of claim 1 the connections for long-, medium- and short-wave signals (4) and for VHF signals (19) lie close to one another at the lateral edge of the rear windscreen.
  20. Aerial array according to claim 1, characterised in that in case a of claim 1 with only one reactance circuit (28) this is a component of the input transformer circuit in the VHF signal path (13) (Fig. 7).
EP85102985A 1984-03-21 1985-03-15 Antenna arrangement in the rear window of a car Expired - Lifetime EP0155647B1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE3410415 1984-03-21
DE19843410415 DE3410415A1 (en) 1984-03-21 1984-03-21 Active aerial in the rear window of a motor vehicle

Publications (3)

Publication Number Publication Date
EP0155647A2 EP0155647A2 (en) 1985-09-25
EP0155647A3 EP0155647A3 (en) 1987-02-04
EP0155647B1 true EP0155647B1 (en) 1992-01-15

Family

ID=6231206

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85102985A Expired - Lifetime EP0155647B1 (en) 1984-03-21 1985-03-15 Antenna arrangement in the rear window of a car

Country Status (3)

Country Link
US (1) US4791426A (en)
EP (1) EP0155647B1 (en)
DE (1) DE3410415A1 (en)

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Also Published As

Publication number Publication date
EP0155647A3 (en) 1987-02-04
EP0155647A2 (en) 1985-09-25
US4791426A (en) 1988-12-13
DE3410415A1 (en) 1985-09-26

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