JPH0270101A - Glass antenna equipment for automobile - Google Patents

Abstract

PURPOSE:To receive FM broadcasting with satisfactory directivity by providing an antenna conductor and a feeding point on the window glass of an automobile and connecting the feeding point to a receiver through a two terminal network showing an almost prescribed inductive impedance over the whole range of an FM frequency. CONSTITUTION:A defogger 4 is provided at the lower part of the glass for the rear window of the automobile and it is connected to the DC power source 25 of 12V through bus bars 3 and 3' and a reactance circuit 18. The antenna conductor 6 is provided at the upper part of a glass plate 1 and is connected to the FM/AM receiver 8 through the feeding point 7 and reactance two terminal network 9 as illustrated. The two terminal network 9 is capacitive and the impedance is set to 90-130OMEGA. Thus, the two terminal network 9 and the FM receiver 8 are electrically matched and they secure sufficient FM reception sensitivity. The module of the reactance circuit 18 interrupts the current of an AM radio wave which is induced by the defogger 4 and improves the sensitivity of AM reception.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a glass antenna device for an automobile in which noise is reduced.

[Prior Art] As an antenna for an automobile radio, as an alternative to a rod antenna or a whip antenna, an antenna for AM or FM is installed on the indoor surface of a glass plate for the rear window of an automobile.
Glass antennas equipped with an antenna conductor for both AM and FM are widely used.

Conventionally, as shown in FIG. 11, as shown in FIG. 11, an antenna conductor 33 in a predetermined linear pattern is provided above a defogger 32 of an energization heating type for a transparent glass plate 31 for the rear window of an automobile. Heating type defogger-3
A choke coil 35 is inserted into the power supply line 34 of No. 2, and the current from the battery 36 passes through, but the high frequency current generated by radio waves in the high frequency band such as radio broadcast waves induced in the defogger's conductive wire flows to the ground. The 11th
As shown in the figure, a preamplifier 4 is installed at a suitable location on a feed line 39 between a feed terminal 37 of an antenna conductor 33 and a radio receiver 38.
It was known that 0 was inserted. However, due to the insertion of a preamplifier, cross modulation occurs in a strong electric field.
There was the problem of high noise. Also, in the case of this method, it was necessary to install a preamplifier separately from the radio receiver, so there was a problem that it was quite expensive.
Installing a preamplifier near the glass antenna is
This had the problem of imposing constraints on the design of the automobile, such as securing space for the preamplifier.

Therefore, it has been desired to develop a glass antenna for automobiles that does not require such a preamplifier and has high gain and low noise.

[Problems to be Solved by the Invention] The present invention solves the problems of the prior art, and provides a glass antenna device for automobiles that does not require an expensive preamplifier, has high gain, and has low noise. In particular, it is an object of the present invention to provide a glass antenna device for an automobile for FM radio broadcasting.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and its structural feature is that an antenna conductor and a feeding point for the antenna conductor are provided on a window glass plate of an automobile. A reactance two-terminal network circuit is connected to the feed point for the antenna conductor, which leads to a radio receiver mounted on the vehicle, and the impedance of the reactance two-terminal network circuit is set to the FM radio. A glass antenna device for an automobile is characterized in that its dielectric property is approximately constant over the entire carrier frequency range.

Further, the structural feature of the present invention is that the absolute value of the impedance of the reactance two-terminal network circuit is 70Ω to 130Ω over the entire FM radio carrier frequency range, and the phase angle is +65 degrees to +85 degrees. This is a characteristic feature of a glass antenna device for automobiles.

Further, a structural feature of the present invention resides in a glass antenna device for an automobile, characterized in that the horizontal length of the automobile window glass plate is 1.7 times or more the length in the height direction. .

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

In FIG. 1, l is a transparent glass plate for the rear window of a passenger car, and a large number of heater wires 2 are provided in the heated area on the inner surface of the glass plate 1, and both ends of the group of heater wires 2 are provided. An electrically heated defogger 4 having opposing bus bars 3.3' connected to the defogger lead wire 5 is provided to the bus bar 3.3' of the defogger 4.
．． 5' is connected.

The defogger 4 shown in FIG. 2 divides one of the buspars on both sides of the defogger 4, for example, one busper, into two vertically from a desired location, a lower buspar 3'a and an upper buspar 3'. b, and this lower bus spar 3'a
The power supply side defogger lead wire 5 is connected to the upper side bus spar 3'b, and the ground side defogger word line 5' is connected to the lower side bus spar 3'a.
In this example, the water flows from the bus bar 3 to the bus bar upper part 3'b in a U-shape. The example of the defogger shown in the figure has a line width of 0.
An electrically heated defogger is formed by printing a conductive silver paste on the inside surface of a glass plate by printing and baking a large number of thin electrically heated heater wires 2 of 5 to 2 mm in parallel at intervals of 2 to 4 cm. − is.

6 is the defogger of the glass plate 1 for a rear window of an automobile.
This is an AM-FM dual purpose antenna conductor provided on the top of the antenna. In the illustrated example, the antenna conductor 68 and the defogger 4a, which are adjacent parts of the antenna conductor 6 and a part of the defogger 4, are capacitively coupled, and no direct current is transmitted or received between them. However, they are placed close to each other at a predetermined interval so that high frequency current can be transmitted and received. This antenna conductor 6a and defogger 4a
The parts are spaced apart from each other by, for example, about 1 mm to 10 mm.

The antenna conductor 6 appears to function as a part of the defogger due to capacitive coupling with the defogger 4. Especially for the AM band of radio broadcasting, Defogger-4
It also functions as part of the AM antenna, increasing the length of the AM band antenna, allowing it to receive more radio waves, and increasing sensitivity. Note that the antenna conductor 6 functions for FM broadcast carrier waves.

In the above example, the antenna conductor 6 and the defogger 4 are placed close to each other in some parts so that high frequency current can be transmitted and received. Alternatively, the defogger may be provided so that the high frequency current is not transmitted or received.Of course, the rear window glass plate does not need to be provided with a defogger.

As mentioned above, the defogger 4 and the antenna conductor 6 are
The defogger 4 and the antenna conductor 6 are normally placed on the same surface as the rear window glass plate in order to capacitively couple a portion thereof and to facilitate linear printing and printing. It is best to form it on the side of the room. The pattern of the antenna conductor 6 may be suitable for FM band radio broadcasting, both AM band and FM band radio broadcasting, or FM band radio broadcasting, depending on the shape of the car, the shape and dimensions of the glass plate, and the configuration.
A pattern is appropriately selected and designed so that the optimum performance can be obtained as an antenna for television and other broadcasting, etc., while also serving as an antenna for band radio broadcasting.

In the illustrated example, the antenna conductor 6 is provided above the defogger 4 of the rear window glass plate 1 of an automobile, but the antenna conductor 6 is not limited to this, and may be provided at the bottom of the defogger 4. - may be provided at the top and bottom, respectively, or may be provided at other margins.

In addition, the most common antenna conductor is a linear printed type, which is made by printing and baking a predetermined pattern of conductive silver paste on the surface of a glass plate, similar to the defogger heater wire mentioned above. The antenna conductor is not limited to this, and may be an antenna conductor made of a transparent conductive film in a predetermined pattern or an ultrafine conductive wire.

In the present invention, a reactance two-terminal network circuit 9 is connected at a desired position on the path between the feed point 7 for the antenna conductor 6 and the radio receiver 8 mounted on the vehicle.

This reactance two-terminal network circuit basically consists of each element of a first coil 10, a first capacitor 11, and a second coil 12, as shown in FIG. 8 and the reactance two-terminal network circuit 9 are matched, and the impedance of the reactance circuit viewed from the feed point 7 maintains dielectricity over the entire FM radio carrier frequency, for example, a band of 70 to 100 MHz, and is almost constant. The value of each element is selected so that the value is the same.

Preferably, the impedance of this reactance two-terminal network circuit has an absolute value in the range of 70Ω to 130Ω over the entire FM radio carrier frequency range, and a phase angle in the range of +65 degrees to +85 degrees.

Also, if you want to receive AM radio broadcasts with sufficient performance and low noise, the impedance of the reactance two-terminal network circuit described above can be changed to the impedance of the antenna conductor viewed from the input end of the radio receiver over the entire AM radio carrier frequency range. It is preferable to make it slightly inductive.

Further, the antenna conductor 6 and the defogger 4 are usually formed by printing conductive silver paste on the surface of a glass plate and baking it. In this case, the adjacent antenna conductor 6a and defogger part 4a There is a risk that migration of the printed silver may occur between the two parts, resulting in a short circuit between the two. In this case, a large current will flow through the radio receiver 8, so to prevent this, a DC blocking capacitor 17 may be inserted between the feed point 7 of the antenna conductor 6 and the reactance two-terminal network circuit 9. good.

In the present invention, a current is passed from the DC power supply 7 to the defogger 4 between the defogger lead wires 5 and 5' of the defogger 4, but current in a high frequency band such as a radio broadcasting frequency band is cut off. It is preferable to insert a reactance circuit module 18 in order to be able to receive AM radio broadcasts.This reactance circuit module 18 connects the heater wire 2 of the defogger 4 and the busper 3.3' at high frequency. It can be floated, and it is possible to prevent the current caused by radio waves in the high frequency band such as radio broadcasting induced in the heater wire 2 and the busper 3.3' from flowing to the ground, and to send the induced current to the radio receiver without leakage. Reference numeral 19 in the reactance circuit module 18 is a high frequency choke coil, which has high impedance in a high frequency band such as a radio broadcast band, and has characteristics that prevent magnetic residual, for example, a magnetic core wound with a pie filer. A high-frequency choke coil, a high-frequency choke coil wound in a direction that mutually cancels out the magnetic flux of the coil generated by a current from a closed magnetic circuit, or a high-frequency choke coil using a core with a high degree of magnetic saturation is used.

In particular, this choke coil has a self-resonant frequency of approximately 0.5 to 2.0 MHz, particularly preferably 1.0 to 1.0 MHz.
5M) Iz range is optimal.

The glass plate in the automotive glass antenna device of the present invention is generally rectangular, approximately trapezoidal, or fan-shaped due to the design of the rear window of the vehicle.
As in (b) and (c), the lateral lengths AI, A2
By making the average length Aav at least 1.7 times, preferably about 1.7 to 4 times, the average height Bav of the vertical heights B, , B, the reception sensitivity and It has been experimentally confirmed that omnidirectionality, especially omnidirectionality, is improved.

A reactance two-terminal network of the type shown in FIG. 4 of an embodiment of the automotive glass antenna device of the present invention, particularly the automotive glass antenna device for the rear window of a passenger car for receiving FM radio broadcasts or for receiving FM-AM combined radio broadcasts. In the circuit, the coil lO is 160 to 500 μH. The added value of the stray capacitance of the coil 10 and the capacitor 11 is 5 to 15 pF.
, the coil 13 is 120 to 260μH, and the added value of the stray capacitance of the coil 13 and the capacitor 15 is 64 to 100p.
F, resistance 14 is 800-1200Ω, particularly preferably 900-1100Ω, coil 12 is 0.3-1.2μH
1 Particularly preferably 0.5 to 1.0 μH 1 This coil 12
The stray capacitance of is 0.59F or less, and the capacitor 1
7 preferably has a value of 1000 to 10000 pF. Of course, these values are examples of typical ranges, and can be changed to obtain optimal performance depending on the target automotive glass antenna device.

[Function] The function of the FM radio carrier frequency band of the automotive glass antenna device of the present invention is considered to be as follows.

Since the impedance of the choke coil 19 having a self-resonant frequency of 1.0 to 1.5 MHz is extremely small in the FM radio carrier frequency band, the defogger 4 has the same potential as the body of the car in which this glass antenna device is installed. ,
When the reactance two-terminal network circuit 9 has a configuration as shown in Figs. 3 to 5, it is expressed as an equivalent circuit as shown in Fig. 6, where the capacitive impedance of the capacitor 20 and the inductive impedance of the coil 21 are added, and It has a phase of +85 degrees, and the pure resistance of resistor 22 is added to it, making it 70 to 130Ω.
It will have an impedance of

The characteristic impedance of the coaxial cable 23 connecting the reactance two-terminal network circuit 9 and the radio receiver 8 is usually capacitive 50Ω, while the input impedance of the radio reception tj18 is usually around 100Ω. Electrical matching between the receiver 8 and the radio receiver 8, especially the FM radio receiver, is improved, and sufficient reception sensitivity can be ensured.

In addition, since the antenna conductor 6 becomes capacitive between the automobile body 24 and the defogger 4, the inductivity of the reactance two-terminal network circuit 9 cancels each other out, resulting in efficient FM.
You can receive radio waves.

A reception current of the external FM radio wave flows through the car body and the defogger 4 relative to the ground, and is induced into the antenna conductor 6.

Therefore, the directionality of the received electric field strength depends on the shape of the vehicle body, the shape of the glass plate, the wiring pattern of the defogger heater wire,
Governed by shape, antenna conductor pattern, and shape. The impedance when looking at the antenna from feed point 7 is 70-13
The above-mentioned directivity becomes even better when the resistance is set to 0Ω, particularly preferably from 90 to 110Ω, and the length of the glass plate in the horizontal direction is 1.7 times or more the length in the height direction.

In the automotive glass antenna device of the present invention, AM radio broadcasting can be received with good sensitivity and low noise, and the effect of the AM radio carrier frequency band in this case is considered to be as follows.

Because the choke coil 19 is inserted into the power supply line of the defogger 4, which has a high self-resonant frequency, the impedance between the defogger 4 and the ground becomes high.
is separated from the earth. Noise from the power supply 25 is absorbed by the capacitor 26 in addition to the choke coil 19. When the defogger 4 is provided in parallel with the antenna conductor 6, with part of its pattern adjoining, the defogger 4 can be regarded as part of the antenna due to capacitive coupling. When the reactance two-terminal network circuit 9 is shown in FIG. 4, it becomes the equivalent circuit shown in FIG. 7 at the AM radio carrier frequency.

The reactance two-terminal network circuit of FIG. 7 can conveniently (electrically match) the antenna impedance seen from the feed point 7 and the radio receiver 8 over the entire range of the AM radio carrier frequency.

[Example] Hereinafter, explanation will be given according to examples.

In FIG. 2, a defogger 4 is provided at the bottom of a glass plate 1 for a rear window of an automobile, and the defogger 4 is connected to a bus bar 3.
A current of 12 A is supplied from a 12 volt DC power supply 25 via a. The capacitor 26 is provided to prevent noise generated from the power supply 25 from propagating to the antenna conductor, and the self-resonance frequency of the choke coil 19 of the reactance circuit module 18 is 1. It is OMHz.

An antenna conductor 6 is provided on the top of the glass plate 1, connected to a reactance two-terminal network circuit through a feed point 7, and then connected to a radio receiver 8. This radio receiver 8 is capable of receiving FM radio broadcasts or FM-AM radio broadcasts.

Receivable carrier frequencies are 400KHz to 1.7MHz and 70 to loOMHz. As the reactance two-terminal network circuit, one having a configuration as shown in FIG. 4 is used. In Figure 4, capacitor 17 is 10000p
F, the coil IO is 330μH, the total value of the stray capacitance of the coil IO and the capacitor 11 is lOp
Coil 13 of F is 18QμH, and the total value of the stray capacitance of coil I3 and the capacitor of capacitor 15 is 829F.
, the resistor 14 is IKΩ, and the coil 12 is 1.0μH to reduce stray capacitance (in order to minimize stray capacitance, it is made by winding 0.47φ copper wire with an air core and 7 turns of 7mmφ, and the stray capacitance is 0.z
pF was used.

Figure 5 is a modified version of Figure 4, which allows FM radio frequencies to be received with high sensitivity and low noise, and is designed to have a constant impedance regardless of the frequency at AM radio frequencies. be. In FIG. 5, the coil 13 is 150μH, and the coil 16 is 150μH.
0μH, capacitor 15 is 33pF, resistor 14 is 68
It is 0Ω.

The equivalent circuit at AM radio frequency is shown as 7th
As shown in the diagram.

FIG. 3 is a modification of FIG. 4, and is a simplified version. Third
In the figure, the coil IO is 270 μH, and the equivalent circuit at AM radio frequency is shown in FIG. 9.

[Effects of the Invention] According to the glass antenna device for automobiles of the present invention, it is possible to receive FM radio broadcasts in a directional manner due to the above-described effects. The circuit is a matching circuit consisting of a simple circuit, and compared to the conventional case where a preamplifier is used, there are fewer reflections and backflows at various places, and the waveform of the electrical signal entering the radio receiver is It is possible to improve the fidelity, that is, the reproducibility, of the transmitted signal and radio signal when they enter the radio receiver, and to obtain good and stable reception performance. The reactance two-terminal network circuit of the present invention can be used not only as an FM antenna, but also as an AM/FM dual-purpose antenna for automobiles. Compared to this, a higher noise reduction effect can be obtained,
Also, the matching effect is sufficient.

Moreover, it does not require a preamplifier, which is required in the conventional method, and can be realized with a simple reactance two-terminal network circuit, reducing costs and making installation in automobiles, maintenance, etc. It is easy to use and can be made compact, which has the advantage of expanding the degree of freedom in car design.Furthermore, since it is composed only of reactance elements, it is not necessary to supply DC power as in the case of a preamplifier. This is not necessary, and further significant cost reductions can be achieved.

[Brief explanation of the drawing]

FIG. 1.2 is a schematic explanatory diagram showing an overall view of an embodiment of the device of the present invention, and FIGS. 3 to 5 are specific configuration diagrams of a reactance two-terminal network circuit applied to the device of the present invention, FIG. 6 is an equivalent circuit diagram of the FM radio carrier frequency band of FIGS. 3 to 5, and FIG. 7 is an equivalent circuit diagram of the A and M radio carrier frequency bands of the reactance two-terminal network circuit of FIG. 4. 8th
The figure is an equivalent circuit diagram of the AM radio carrier frequency band of the reactance two-terminal network circuit of FIG. 5, and FIG. 9 is an equivalent circuit diagram of the radio carrier frequency band of the reactance two-terminal network circuit of FIG. Figure 1O (a), (b), (C
) is a plan view of a glass plate applied to the device of the present invention,
FIG. 11 is a schematic explanatory diagram showing the entire conventional glass antenna device for an automobile. FIG. 5 is an overall view showing a conventional example. In the figure, 1 is a glass plate, 2 is a heater wire, 3.3'
4 is the defogger, 5 is the lead wire of the defogger, 6 is the antenna conductor, 7 is the feed point, 8 is the radio receiver, 9 is the reactance two-terminal network circuit, IO is the first coil, 11 is the 1st capacitor, 12 is second coil, 13 is coil, 14 is resistor, 15 is capacitor 1
6 is a coil, 17 is a capacitor, 25 is a power supply, 27 is a choke coil, and 28 is a capacitor. Figure 3 w-A2 (Aa Li-1 (a)

Claims (3)

[Claims] (1) An automobile window glass plate is equipped with an antenna glass provided with an antenna conductor and a feeding point for the antenna conductor, and the feeding point for the antenna conductor is equipped with a reactance double wire connected to a radio receiver mounted on the automobile. A glass antenna device for an automobile, characterized in that a terminal network circuit is connected thereto, and the impedance of the reactance two-terminal network circuit is a substantially constant dielectric value over the entire FM radio carrier frequency range. (2) The absolute value of the impedance of the reactance two-terminal network circuit above is 70Ω or more over the entire FM radio carrier frequency range.
2. The glass antenna device for an automobile according to claim 1, wherein the antenna resistance is 130Ω and the phase angle is from +65 degrees to +85 degrees. (3) The automobile glass antenna device according to claim 1, wherein the length of the automobile window glass plate in the horizontal direction is at least 1.7 times the length in the height direction.