JPH11239014A - Windshield antenna unit for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively use a windshield antenna provided on a small-space windshield plate by specifying the inductance value of a series resonance coil. SOLUTION: As for series resonance, the impedance of a 1st antenna conductor 2a and a coil 31 for series resonance are included as resonance elements. As for parallel resonance, the impedance of a 2nd antenna conductor 2b and the inductance of a coil for parallel resonance are included as resonance elements, and the impedance of the 2nd antenna conductor 2b consists principally of stray capacitance. The stray capacitance of the 2nd antenna conductor 2b is 30 to 60 pF. This is for the purpose of the use of the windshield antenna provided for the small-space windshield plate 1. The inductance value of the coil 32 for parallel resonance is 1.8 to 5.2 mH. In this case, the 1st antenna conductor 2a and 2nd antenna conductor 2b are electrically connected to send a receive signal of an AM broadcast excited at the 2nd antenna conductor 2b to a receiver.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an AM broadcast band (53
0-1630kHz), FM broadcast band (76-90MHz)
(Japan)), and a glass antenna device for an automobile suitable for receiving FM broadcast band (88 to 108 MHz (USA)).

[0002]

2. Description of the Related Art Conventionally, a glass antenna device for a vehicle shown in FIG. 2 has been proposed as a glass antenna device for a vehicle for improving the sensitivity by utilizing resonance (Japanese Utility Model Publication No. 4-5307).
0). In this conventional example, a heater wire 22 and a defogger 90 composed of bus bars 15a, 15b, 15c are provided on a rear window glass plate 21 of an automobile, and a choke coil 9 is provided between the bus bars 15a, 15b and a DC power supply 10 for the defogger 90. By connecting and increasing the impedance of the choke coil 9 in the high frequency band, a DC current flows from the DC power supply 10 to the defogger 90 but cuts off a high frequency band current such as a broadcast frequency band. We use as.

In the AM broadcasting band, a defogger 90 is used.
Stray capacitance to ground (hereinafter simply referred to as stray capacitance) (65
pF) and a parallel resonance with the coil 71 (150 μH),
Further, the coil 72, the capacitor 73, and the resistor 74 allow the reception signal of the AM broadcast band to pass. Reference numeral 11 denotes a noise cut capacitor. In the conventional example shown in FIG. 2, by adopting such a configuration, sensitivity is improved and noise is reduced.

However, in this conventional example, since a large-area defogger 90 is used as an antenna, for example,
There was a problem that it could not be used as it is for a window glass plate of a small space such as a side window glass plate.

[0005]

SUMMARY OF THE INVENTION The present invention aims at solving the above-mentioned disadvantages of the prior art and newly provides a highly sensitive automotive glass antenna device.

[0006]

SUMMARY OF THE INVENTION The present invention provides a series resonance coil, a parallel resonance coil, a first antenna conductor provided on a window glass plate of an automobile, and a second antenna provided on the window glass plate. The second antenna conductor has an impedance of 30 to 60 pF with respect to a ground stray capacitance, and causes a series resonance including the impedance of the first antenna conductor and the inductance of the series resonance coil as resonance elements. This causes parallel resonance including the impedance of the second antenna conductor and the inductance of the parallel resonance coil as resonance elements, and the resonance frequency of the series resonance and the resonance frequency of the parallel resonance are respectively the sensitivity of the AM broadcast band. Is improved so that the first antenna conductor and the second antenna conductor are electrically connected to each other. Inductance value of yl 1.8
Provided is a glass antenna device for a vehicle, which is in a range of 5.2 mH.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a structural view of an embodiment of an automotive glass antenna device of the present invention using a side window glass plate 1 of an automobile. In FIG. 1, 1 is a side window glass plate, 2a is a first antenna conductor, 2b is a second antenna conductor, 4a and 4b are feed points, 5 is a DC blocking capacitor, 6 is a bypass capacitor, and 8 is a high frequency choke. A coil, 31 is a series resonance coil, 32 is a parallel resonance coil, and 33, 34, and 35 are damping resistors.

[0008] DC blocking capacitor 5, bypass capacitor 6, high-frequency choke coil 8, damping resistor 3
3, 34 and 35 are provided as needed. The high-frequency choke coil 8 is not provided.
When the part is open, the first
It is preferable that the antenna conductor 2a and the second antenna conductor 2b are capacitively coupled to each other close to each other. When capacitively coupled, the sensitivity of the AM broadcast band is usually improved by 0.5 dB or more as compared with the case where capacitive coupling is not performed.

First antenna conductor 2a and antenna conductor 2
b is capacitively coupled, the distance between the two is usually 0.1 mm.
It is about 1 to 50 mm. DC current is not transmitted and received between the capacitively coupled first antenna conductor 2a and second antenna conductor 2b, but transmission and reception of the received signal current are performed.

In the present invention, two resonances are caused to improve the sensitivity. Regarding series resonance, the impedance of the first antenna conductor and the inductance of the series resonance coil are included as resonance elements.

The impedance of the first antenna conductor 2a is mainly composed of a stray capacitance, and the impedance of the first antenna conductor 2a is different from the feed point 4a.
It refers to the impedance when looking at the a side.

Further, the resonance frequency of the series resonance may be adjusted by connecting a capacitance component in parallel between the stray capacitance of the first antenna conductor 2a and the vehicle body ground. This capacitance component can also be a resonance element of series resonance.

The series resonance includes a series resonance coil 3.
(1) The stray capacitance of the peripheral wiring, the stray capacitance of the cable connected between the glass antenna and the receiver, and the close capacitance of the capacitive coupling also influence, and these can also be resonance elements of series resonance. Usually 10 μH to 1
Those having a pressure of about mH are used.

With regard to the parallel resonance, the impedance of the second antenna conductor and the inductance of the parallel resonance coil 32 are included as resonance elements.
The impedance of b mainly consists of stray capacitance. The stray capacitance of the second antenna conductor 2b is in the range of 30 to 60 pF. This is because the purpose is to use a glass antenna provided on a window glass plate in a small space.

The impedance of the second antenna conductor 2b refers to the impedance when the second antenna conductor 2b is viewed from the feeding point 4b. Also, a capacitance component may be connected in parallel between the stray capacitance and the vehicle body ground to adjust the resonance frequency of the parallel resonance. This capacitance component can also be a resonance element of parallel resonance.

The range of the inductance value of the parallel resonance coil 32 is in the range of 1.8 to 5.2 mH. When the inductance value of the parallel resonance coil 32 is 1.8 mH or more, the sensitivity near the lowest frequency of the AM broadcast band is lower than that when the inductance value is less than 1.8 mH, which is not preferable.

When the inductance value of the parallel resonance coil 32 is 5.2 mH or less, the sensitivity near the center frequency of the AM broadcasting band is lowered as compared with the case where the inductance value exceeds 5.2 mH, which is not preferable.

The parallel resonance includes a parallel resonance coil 3.
The stray capacitance of the peripheral wiring and the proximity capacitance can also be the resonance elements of the parallel resonance. The parallel resonance coil 32
However, if the inductance is lost at the FM broadcast frequency (that is, it has a capacitive property), the received signal leaks to the vehicle body ground, and the sensitivity of the FM broadcast band decreases. To prevent this, a high-frequency choke coil (not shown) may be connected in series to the parallel resonance coil 32. Usually, about 0.1 to 100 μH is used for this high frequency choke coil.

In the present invention, two resonances occur because only one resonance cannot cover a wide AM broadcast band. Therefore, in the present invention, it is desirable to divide the AM broadcast band into two substantially at the center frequency and to share each of the two by two resonances so as to flatten the sensitivity. Here, sensitivity flattening refers to reducing the difference between the highest sensitivity and the lowest sensitivity in a band such as an AM broadcast band.

Instead of capacitively coupling the first antenna conductor 2a and the second antenna conductor 2b, a high-frequency choke coil 8 is connected between the first antenna conductor 3a and the second antenna conductor 2b. Good. The impedance of the high-frequency choke coil 8 is usually several kΩ or less in the AM broadcast band, electrically connects the first antenna conductor 2a and the second antenna conductor 2b, and excites the AM broadcast to the second antenna conductor 2b. Send the received signal to the receiver.

On the other hand, in the FM broadcasting band, the impedance of the high-frequency choke coil 8 usually exceeds several kΩ, and the impedance between the first antenna conductor 2a and the second antenna conductor 2b is set to high impedance. This prevents the reception signal of the FM broadcast excited in the antenna conductor 2a from leaking to the vehicle body ground via the series resonance coil 32. As the high-frequency choke coil 8, a coil of 0.5 to 100 μH is usually used.

The bypass capacitor 6 has a function of passing a reception signal in the FM broadcast band and sending it to the receiver. Usually, 1 to 1000 pF is used for the bypass capacitor 6. The DC blocking capacitor 5 is usually 100 pF to 50 pF.
μF is used.

As described above, in FIG. 1, the capacitors 5, 6 and the resistors 33, 34, 35 are provided as necessary and can be omitted. Here, the capacitor 6, the resistors 34, 35
Omission means open, and omission of capacitor 5 and resistor 33 means short circuit.

FIG. 4 is a configuration diagram of an embodiment of a glass antenna device for a vehicle according to the present invention of a different type from that of FIG. 1 and shows a configuration in which the high-frequency choke coil 8 and the resistor 33 are omitted.

[0025]

EXAMPLE 1 (Example) A glass antenna device as shown in FIG. 4 was manufactured using a side window lath plate of an automobile. The size of the side window lath plate is 500 (length) x 600
(Horizontal, maximum length) mm. Each circuit constant is as follows.

The series resonance coil 31 = 180 μH, the parallel resonance coil 32 = 2.0 mH, the capacitor 5 = 1000 pF, the bypass capacitor 6 = 10 pF, the resistance 34 = 4.7 kΩ, and the resistance 35 = 4.7 kΩ.

The shortest distance between the first antenna conductor 3a and the second antenna conductor 3b was set to 10 mm, and both were capacitively coupled. FIG. 3 is a frequency characteristic diagram of AM broadcast band sensitivity. For FM broadcasting, the sensitivity was lower than that of a pole antenna having a length of 910 mm, but within 2 dB.

"Example 2 (Example)" The parallel resonance coil 32
Example 1 except that the value of the inductance of
A glass antenna device as shown in FIG. FIG. 3 shows the frequency characteristics of the sensitivity of the AM broadcast band. For FM broadcasting, the length is 910 mm
Although the sensitivity was lower than that of the pole antenna of No. 2, it was within 2 dB.

Example 3 (Example) The parallel resonance coil 32
A glass antenna device as shown in FIG. 4 was manufactured with exactly the same specifications as in Example 1 except that the inductance value was set to 5.0 mmH. FIG. 3 shows the frequency characteristics of the sensitivity of the AM broadcast band. For FM broadcasting, the length is 910 m
The sensitivity was lower than that of the m pole antenna, but was within 2 dB.

Example 4 (Comparative Example) Parallel Resonant Coil 32
Example 1 except that the value of the inductance of
A glass antenna device as shown in FIG. FIG. 3 shows the frequency characteristics of the sensitivity of the AM broadcast band.

Example 5 (Comparative Example) Parallel Resonant Coil 32
Example 1 except that the inductance value was 6.0 mH.
A glass antenna device as shown in FIG. FIG. 3 shows the frequency characteristics of the sensitivity of the AM broadcast band.

[0032]

According to the present invention, AM broadcasts can be received with high sensitivity, and FM broadcasts can be received with almost the same sensitivity as a pole antenna, and a glass antenna provided on a window glass plate in a small space can be effectively used. it can.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of a glass antenna device for a vehicle of the present invention.

FIG. 2 is a configuration diagram of a conventional example.

FIG. 3 is a frequency characteristic diagram of sensitivity of an AM broadcast band in Examples 1 and 2;

FIG. 4 is a configuration diagram of another example of an embodiment.

[Explanation of symbols]

 1: Side window glass plate 2a: First antenna conductor 2b: Second antenna conductor 4a, 4b: Feed point 5: DC blocking capacitor 6: Bypass capacitor 8: High frequency choke coil 31: Series resonance coil 32: Parallel Resonant coils 33, 34, 35: damping resistance

Claims (1)

[Claims] 1. A second antenna comprising a series resonance coil, a parallel resonance coil, a first antenna conductor provided on a window glass plate of an automobile, and a second antenna conductor provided on the window glass plate. The impedance of the conductor is mainly 30-60
It has a stray capacitance of pF with respect to ground, and generates series resonance including the impedance of the first antenna conductor and the inductance of the series resonance coil as resonance elements. The impedance of the second antenna conductor and the parallel resonance coil And a parallel resonance including an inductance as a resonance element. The resonance frequency of the series resonance and the resonance frequency of the parallel resonance are frequencies that improve the sensitivity of the AM broadcast band. 2 are electrically connected to each other, and the inductance value of the series resonance coil is 1.8 to 5.2.
A glass antenna device for an automobile, which is within the range of mH.