JP3588896B2 - Automotive glass antenna - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a glass antenna for an automobile suitable for receiving AM broadcast, FM broadcast, television broadcast, and the like.
[0002]
[Prior art]
Conventionally, the antenna shown in FIG. 4 has been proposed as a glass antenna for an automobile for AM broadcasting and FM broadcasting. As shown in FIG. 4, this conventional glass antenna for a vehicle includes an electrically heated defogger having a heater wire 2 and bus bars 3a, 3b, 3c for supplying power to the heater wire 2 on a glass plate 1 of a rear window of the vehicle. The choke coil 7 is inserted between the bus bars 3a, 3b and the DC power supply 9 for the defogger, the antenna conductor 4 is provided on the glass plate 1 of the rear window, and the proximity line 15 drawn from substantially the center in the lateral direction of the defogger. Is capacitively coupled to the antenna conductor 4.
[0003]
In FIG. 4, 6 is a coaxial cable, 8 is a capacitor, and 10a and 10b are high frequency choke coils.
[0004]
[Problems to be solved by the invention]
FIG. 5 shows the directional characteristics of horizontal polarization when FM broadcasting is received with the conventional automobile glass antenna shown in FIG. In FIG. 5, the reception sensitivity in the vehicle front-rear direction is reduced. That is, when there is a transmission tower in the front-rear direction of the vehicle, there is a problem that the broadcast cannot be properly received. In FIG. 5, 0 ° is the front direction of the vehicle, and 90 ° is the left direction of the vehicle. This condition is the same in FIG. 3 described later.
[0005]
The present invention solves the above-mentioned problems found in the conventional glass antenna for automobiles, and newly provides a glass antenna for automobiles that can receive signals satisfactorily even when a transmission tower for FM broadcasting or the like is located in front and behind the vehicle.
[0006]
[Means for Solving the Problems]
The present invention provides an electrically heated defogger having a heater wire and left and right bus bars for supplying power to the heater wire on a glass plate of a rear window of an automobile, and a choke coil is provided between the bus bar and a DC power supply for the defogger. Insert and provide an antenna conductor on the glass plate of the rear window, where the defogger is not provided, and bring the capacitive coupling conductor extended from the bus bar or the heater wire near the bus bar close to the antenna conductor at a predetermined interval Te automotive glass antenna odor made by capacitive coupling, the defogger has a bus bar to the left and right sides, first and second capacitive coupling respectively to be extended from the heater wire of the bus bar or the left and right sides of the bus bar near the left and right sides use conductor is provided, the coupling capacitance between the first capacitive coupling conductor and the antenna conductor C _a, between the second capacitive coupling conductor and the antenna conductor When the coupling capacitance and _{C b, | C a -C b} | / MAX (C a, C b) to provide a glass antenna for an automobile, which comprises a ≦ 0.5. Where | C _a −C _b | indicates the difference between _Ca and C _b, and MAX (C _a , C _b ) indicates the maximum value between _Ca and C _b .
[0007]
The present invention also provides the above-mentioned glass antenna for automobiles, wherein the pattern of the antenna conductor is a pattern including a loop-shaped conductor.
[0008 ]
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows a basic configuration of a typical example of the glass antenna for an automobile of the present invention.
[0010]
In FIG. 1, 5a is a first capacitive coupling conductor, 5b is a second capacitive coupling conductor, and 11 is a feeding point. Reference numerals 20 and 21 denote short-circuit lines that short-circuit portions of the plurality of heater wires 2 other than the bus bar, reference numeral 20 denotes a first short-circuit line, and reference numeral 21 denotes a second short-circuit line. In FIG. 1, the same components or members as those in FIG. 4 are denoted by the same reference numerals or symbols, and description thereof will be omitted.
[0011]
The shape of the antenna conductor 4 is not particularly limited, and may be one or more linear or curved patterns, or may be a pattern including a loop-shaped conductor. However, in order to improve reception sensitivity, a pattern including a loop-shaped conductor is preferable. When the shape of the antenna conductor 4 is a pattern including a loop-shaped conductor, the reception sensitivity is about 0.5 to 2 dB as compared with the case where the shape of the antenna conductor 4 is a pattern not including the loop-shaped conductor. Good.
[0012]
The loop shape of the antenna conductor 4 means a loop in an electrical sense. “Electrical meaning” refers to a loop that passes DC or AC current. Therefore, the shape of the antenna conductor 4 does not have to be a complete loop. When a part of the loop is interrupted and the interrupted portion is named an opening, it is necessary that the opening be capacitively coupled. For medium and higher frequencies, this opening is shorted. The width of the opening is usually about 0.1 to 30 mm for capacitive coupling.
[0013]
The loop shape of the antenna conductor 4 may be directly connected to the feeding point, or may be connected to the feeding point via a connecting line.
[0014]
The antenna conductor 4 shown in FIG. 1 is not provided with an auxiliary antenna conductor. However, the present invention is not limited to this. For the purpose of phase adjustment and directivity adjustment, a connection conductor is provided on the conductor pattern or feed point of the antenna conductor 4. An auxiliary antenna conductor having a substantially T-shape, a substantially L-shape, a loop shape, or the like may be provided with or without the intermediary.
[0015]
In FIG. 1, the shape of the antenna conductor 4 is a substantially rectangular loop-shaped pattern. At this time, the dimension of the loop pattern in the substantially vertical direction is as follows: when the wavelength of the desired reception frequency is λ, and the shortening rate of the glass antenna is K,
(Λ / 100) × K to (λ × 1/10) × K
Is preferable. The glass shortening rate K is usually 0.64.
[0016]
Further, the dimension of the loop pattern in the substantially horizontal direction is preferably in the range of (λ / 4) × K to λ × K. If it is out of this range, the reception sensitivity by several dB will be deteriorated. Note that λ is usually set to the center frequency of the broadcast band.
[0017]
Regarding the pattern of the antenna conductor 4, it is most suitable as an antenna for AM broadcasting, FM broadcasting, both AM broadcasting and FM broadcasting, or for broadcasting and other broadcasting, depending on the shape of the automobile, the shape, dimensions, configuration, etc. of the glass plate. A pattern that achieves high performance is appropriately selected and designed.
[0018]
In the present invention, it is assumed that the antenna conductor 4 and the defogger are capacitively coupled so that DC current is not transmitted and received between them, but medium wave and high frequency current are transmitted and received.
[0019]
In the case of FIG. 1, the antenna conductor 4 is provided in a margin above the defogger of the glass plate 1. The lower part of the loop of the antenna conductor 4 and the capacitive coupling conductors 5a and 5b are close to each other with a predetermined distance therebetween. Due to this proximity, the direct current is not transmitted and received between the antenna conductor 4 and the defogger. , Medium-wave, and high-frequency currents are capacitively coupled to each other.
[0020]
The lower portion of the loop of the antenna conductor 4 and the capacitive coupling conductors 5a and 5b are usually separated from each other by a predetermined distance of about 0.1 to 30 mm, which is a range of capacitive coupling. The defogger apparently functions as a part of the antenna by this capacitive coupling. In particular, for the AM broadcasting band (hereinafter, AM band), the defogger also functions as a part of the AM broadcasting antenna, and the effective length of the AM broadcasting antenna becomes longer. improves.
[0021]
In the case of FIG. 1, the number of the capacitive coupling conductors is two, that is, the capacitive coupling conductors 5a and 5b. However, the present invention is not limited to this, and may be one or three or more. However, it is preferable to use a plurality of lines rather than one line, and it is preferable to provide capacitive coupling conductors on the left and right bus bars from the viewpoint of improving reception sensitivity. Providing the capacitive coupling conductors on the left and right busbars improves the reception sensitivity by several dB, as compared with the case where one capacitive coupling conductor is provided on one busbar. Further, the shape of the capacitive coupling conductor is not limited to the shape shown in FIG. 1 and may be one or a plurality of linear or curved patterns.
[0022]
Also, in the case of FIG. 1, the capacitive coupling conductor extends from the bus bar, but is not limited to this, and may extend from the heater wire 2 near the bus bar.
[0023]
Also, as shown in FIG. 1, the capacitive coupling conductors 5 a and 5 b are provided on the left and right bus bars, where the coupling capacitance between the capacitive coupling conductor 5 a and the antenna conductor 4 is C _a , and the capacitive coupling conductor the coupling capacitance between the 5b and the antenna conductor 4 when the C _b,
| C _a −C _b | / MAX (C _a , C _b ) ≦ 0.5
It is preferable that Within this range, the flatness of the receiving sensitivity over the entire FM band is improved, and the difference between the highest receiving sensitivity and the lowest receiving sensitivity is usually about 10 dB or less. Here, | shows the difference between C _a and _{C b, MAX (C a,} C b) a maximum value of the C _a and C _b | C _a -C _b.
[0024]
More preferably,
| C _a −C _b | / MAX (C _a , C _b ) ≦ 0.2
And Within this range, the difference between the highest reception sensitivity and the lowest reception sensitivity over the entire FM band is usually about 7 dB or less.
[0025]
The capacitive coupling conductor itself functions not only as a capacitive coupling but also as an antenna. The dimension in the substantially horizontal direction of the capacitive coupling conductor is preferably in the range of (λ / 100) × K to λ × K, and more preferably in the range of (λ / 50) × K to (λ / 2) × K. If the dimension in the substantially horizontal direction is out of the range of (λ / 100) × K to λ × K, the receiving sensitivity is deteriorated by about 0.5 to 1.0 dB as compared with the range, and (λ / 50) If the value is out of the range of × K to (λ / 2) × K, the receiving sensitivity is deteriorated by about 0.5 to 1.0 dB as compared with the range within this range.
[0026]
In the present invention shown in FIG. 1, the position of the glass plate 1 on which the antenna conductor 4 is provided is shown in FIG. 1 in an example in which the antenna conductor 4 is provided in a margin above the defogger of the glass plate 1. The position is not limited to the position shown in FIG. 1 and may be a margin below the defogger of the glass plate 1. Further, the antenna conductors 4 may be provided in the upper and lower portions of the defogger, respectively, or may be provided in other margins.
[0027]
In other words, in the present invention shown in FIG. 1, the antenna conductor may be provided anywhere in the upper, lower, left and right margins of the defogger of the glass plate 1, and the number of antenna conductors provided on the glass plate 1 is not limited.
[0028]
Further, the antenna conductor 4 provided on the glass plate 1 is not limited to AM and FM radios, but can be applied to a television VHF band, a television UHF band, a telephone, and the like.
[0029]
Further, in the present invention, the number of antenna conductors provided on the vehicle is not limited, and diversity reception may be performed between the pole antenna and the antenna conductor provided on the glass plate of the rear window.
[0030]
In FIG. 1, the power supply point 11 is provided on the left peripheral portion of the rear window glass plate 1, but is not limited to this, and may be provided at any position on the rear window glass plate 1. Alternatively, they may be arranged on the upper and lower peripheral edges of the left and right center of the glass plate 1 of the rear window.
[0031]
Further, in the defogger shown in FIG. 1, the right side bus bar of the bus bars on both sides of the defogger is vertically divided into two from a desired position, and a lower bus bar 3b and an upper bus bar 3a are provided. An upper bus bar 3a is connected to a lead wire of the vehicle body ground, and a lower bus bar 3b is connected to a power supply side lead wire. The supplied current flows in a U-shape from the lower bus bar 3b to the upper bus bar 3a through the bus bar 3c.
[0032]
The defogger shown in FIG. 1 has a so-called U-shape, but the defogger according to the present invention is not limited to this, and even if it is a so-called C-shaped defogger as shown in FIG. Available to
[0033]
FIG. 2 shows a basic configuration of a comparative example . In FIG. 2, 3a is a left bus bar, 3b is a right bus bar, 5 is a capacitive coupling conductor, 22 is a first short-circuit line, and 23 is a second short-circuit line. In FIG. 2, the same components or members as those in FIG. 1 or FIG. 4 are denoted by the same reference numerals or symbols, and description thereof is omitted.
[0034]
2, the choke coil 7, the capacitor 8, the DC power supply 9, and the high-frequency choke coils 10a and 10b shown in FIG. 1 are omitted. The bus bar 3a is connected to a lead wire for grounding the vehicle body, and the bus bar 3b is connected to a lead wire on the power supply side.
[0035 ]
[0036 ]
[0037 ]
[0038 ]
[0039 ]
[0040]
In the representative example of the present invention shown in FIG. 1, a choke coil 7 and a high-frequency choke coil 10a, 10b are inserted between a bus bar 3a, 3b and a DC power supply 9 for defogger, and the choke coil 7 and the high-frequency By increasing the impedance of the choke coils 10a and 10b, a DC current from the DC power supply 9 to the defogger flows, but a current in a high frequency band such as a broadcast frequency band is cut off.
[0041]
In this manner, the choke coil 7 and the high-frequency choke coils 10a and 10b can insulate the heater wire 2 of the defogger and the bus bar from the vehicle body ground at a high frequency, and the high frequency such as a radio broadcast frequency band induced on the heater wire 2 and the bus bar can be obtained. The reception current in the band can be prevented from flowing to the vehicle body ground, and the reception current can be sent to the receiver without leakage.
[0042]
In the case of receiving only the medium-wave band, for example, only the AM band, the high-frequency choke coils 10a and 10b are usually unnecessary, and only the choke coil 7 may be used, and only the FM broadcast frequency band is received. If so, only the high-frequency choke coils 10a and 10b may be used. Even in the case of receiving both the medium wave band and the FM broadcast band (hereinafter, FM band), if there is a coil that satisfies both functions of the choke coil 7 and the high frequency choke coils 10a and 10b, only such a coil is used. Good.
[0043]
The high-frequency choke coils 10a and 10b have a high impedance in the FM band, and usually use a solenoid or a magnetic core that does not use a magnetic core. These have an inductive inductance in the FM band and in the vicinity of the FM band. In some cases, lead wires of an appropriate length can be used as the high-frequency choke coils 10a and 10b.
[0044]
Since the choke coil 7 has a low self-resonant frequency in the FM band and loses inductance, the high-frequency choke coils 10a and 10b substitute for this. When the choke coil 7 does not lose inductance in the FM band, the high-frequency choke coils 10a and 10b are unnecessary.
[0045]
The antenna conductor 4, the heater wire 2, and the bus bars 3b, 5b, 5c are usually formed by printing a conductive metal-containing paste such as a conductive silver paste on the inside surface of the window glass plate 1 and baking it. Although it is manufactured, the present invention is not limited to such a forming method, and a conductive linear body or foil-like body such as a copper wire may be formed on the inside or outside surface of the window glass plate 1. 1 may be provided.
[0046]
Note that diversity reception may be performed by combining the glass antenna of the present invention with another antenna such as a pole antenna.
[0047]
【Example】
(Example 1 "Example" )
An automobile glass antenna as shown in FIG. 1 was produced. The substantially vertical dimension of the loop portion of the antenna conductor 4 was 100 mm, and the substantially horizontal dimension was 600 mm.
[0048]
The substantially horizontal dimension of the capacitive coupling conductor 5a was 400 mm, and the substantially horizontal dimension of the capacitive coupling conductor 5b was 500 mm.
[0049]
The lower part of the loop of the antenna conductor 4 and the capacitive coupling conductors 5a and 5b are close to each other with an interval of approximately 10 mm, and the direct current is transmitted and received between the antenna conductor 4 and the defogger due to this proximity. However, they are capacitively coupled to transmit and receive medium and high frequency currents. When the coupling capacitance C _a and the coupling capacitance C _b were measured and compared, they were almost the same.
[0050]
The impedance of the series connection of the choke coil 7 and the high-frequency choke coils 10a and 10b is set to a high impedance of 10 kΩ or more in the AM band and the FM band.
[0051]
The reception sensitivity in the FM band was adjusted optimally in the FM band by adjusting the lengths of the antenna conductor 4 and the capacitive coupling conductors 5a and 5b, and the reception sensitivity was increased. As for the directional characteristics of the horizontally polarized waves, substantially elliptical characteristics (FIG. 3) with no decrease in the reception sensitivity in the vehicle front-rear direction were obtained. As a result, both the AM broadcast and the FM broadcast were successfully received. In addition, the difference between the highest reception sensitivity and the lowest reception sensitivity in the entire FM band was about 5 dB or less.
[0052]
(Example 2 "Comparative example" )
Except that the dimension of the capacitive coupling conductor 5b in the substantially horizontal direction was set to 260 mm, the same thing as Example 1 was manufactured in other specifications. In this case, C _a > C _b and (C _a −C _b ) / C _a = 0.6, and the difference between the highest reception sensitivity and the lowest reception sensitivity in the entire FM band was about 12 dB.
[0053]
(Example 3 "Comparative example" )
An automobile glass antenna as shown in FIG. 2 was produced. The heater wires 2 were equally spaced at 35 mm, for a total of 14 wires. The first short-circuit line 22 and the second short-circuit line 23 were not provided. The substantially vertical dimension of the loop portion of the antenna conductor 4 was 100 mm, and the substantially horizontal dimension was 600 mm.
[0054]
The dimension of the capacitive coupling conductor 5 in the substantially horizontal direction was 600 mm. The upper portion of the loop of the antenna conductor 4 and the capacitive coupling conductor 5 are close to each other with an interval of about 10 mm. Due to this proximity, the antenna conductor 4 and the defogger do not transmit and receive DC current between them. , Medium-wave, and high-frequency currents are capacitively coupled to each other.
[0055]
The directional characteristic of the horizontal polarization when the FM antenna of the glass antenna of Example 3 is received is substantially elliptical similarly to the directional characteristic of Example 1 shown in FIG. 3, and there is no decrease in reception sensitivity before and after the vehicle. Was. However, the difference between the highest receiving sensitivity and the lowest receiving sensitivity in the entire FM band was about 12 dB.
[0056]
(Example 4 “Comparative example” )
A glass antenna similar to that of Example 3 was manufactured except that a first short-circuit line 22 and a second short-circuit line 23 were further provided on the glass antenna of Example 3. The lengths of the first short-circuit line 22 and the second short-circuit line 23 were 350 mm and 70 mm, respectively, and the distance between the first short-circuit line 22 and the second short-circuit line 23 was 35 mm.
[0057]
The average receiving sensitivity of Example 3 and Example 4 in the frequency band of 76 to 108 MHz was compared. In both the vertical and horizontal polarization planes, Example 4 showed an improvement of about 1.3 dB over Example 3.
[0058]
【The invention's effect】
According to the present invention, since the capacitive coupling conductor extended from the bus bar or the heater wire near the bus bar is capacitively coupled to the antenna conductor, the reception sensitivity does not decrease in the vehicle front-rear direction in the FM band. Omnidirectional directional characteristics can be obtained.
[0059]
In addition, since the defogger also functions as a part of the antenna due to the capacitive coupling between the capacitive coupling conductor and the antenna conductor, the reception sensitivity in the AM band is increased, and excellent broadcast wave reception can be performed.
[Brief description of the drawings]
FIG. 1 is a basic configuration diagram of a representative example of the present invention. FIG. 2 is a basic configuration diagram of a comparative example . FIG. 3 is a directional characteristic diagram of horizontal polarization in the FM band of Example 1. FIG. Basic configuration diagram [Fig. 5] Directional characteristic diagram of horizontal polarization in FM band of conventional example [Description of symbols]
1: glass plate of rear window 2: heater wires 3a, 3b, 3c: bus bar 4: antenna conductors 5, 5a, 5b: capacitive coupling conductor 6: coaxial cable 7: choke coil 8: capacitor 9: DC power supply 10a, 10b : High-frequency choke coils 20, 22: first short-circuit line 21, 23: second short-circuit line

Claims (3)

An electric heating type defogger having a heater wire and left and right bus bars for supplying power to the heater wire is provided on a glass plate of a rear window of the automobile, and a choke coil is inserted between the bus bar and a DC power supply for the defogger, An antenna conductor is provided in a portion of the window glass plate where the defogger is not provided, and a capacitive coupling conductor extended from a bus bar or a heater wire near the bus bar is brought close to the antenna conductor at a predetermined interval and capacitively coupled. Te automotive glass antenna smell made,
The defogger has bus bars on both left and right sides, and first and second capacitive coupling conductors are provided so as to extend from the bus bars on both left and right sides or heater wires near the bus bars on both right and left sides, respectively. When the coupling capacitance between the coupling conductor and the antenna conductor is C _a and the coupling capacitance between the second capacitance coupling conductor and the antenna conductor is C _b , | C _a −C _b | / MAX (C _a , C _b ) ≦ 0.5. A glass antenna for an automobile, wherein:
However, | shows the difference between C _a and _{C b, MAX (C a,} C b) a maximum value of the C _a and C _b | C _a -C _b. The glass antenna for an automobile according to claim 1 , wherein the pattern of the antenna conductor is a pattern including a loop-shaped conductor. 3. The glass antenna for a vehicle according to claim 1, wherein the antenna conductor has a function of receiving an FM broadcast band or a TV broadcast band .

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