JPH04249404A - Automobile glass antenna - Google Patents

Abstract

PURPOSE:To remove noise from a power supply by grounding a heater by means of high frequency. CONSTITUTION:Between a connecting terminal of heater line H1 for protecting a window glass 10 from being clouded and a car body, a capacitor C is installed to ground the heater terminal by means of high frequency. The heater line resonates at an FM frequency, whereas it does not resonate at an AM frequency. Further, wire W1 installed on the surface of window glass 10 also resonates at an FM, whereas it does not resonate at an AM frequency. So, wire W1 and heater line H1 are laid out appropriately to carry out static electromagnetic coupling to realize a double resonant state, thereby eliminating the necessity of using an FM frequency compensating amplifier, realizing low cost, and being able to protect the occurrence of both noise and intermodulation distortion.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention uses a fog prevention heater wire provided on the rear window glass of an automobile as part of an antenna, and combines it with an antenna provided separately from the heater wire. The present invention relates to a glass antenna for automobiles that receives FM broadcasts, AM broadcasts, etc.

0002

2. Description of the Related Art As a conventional glass antenna for automobiles, one shown in FIG. 6 is known.

The conventional glass antenna shown in FIG. 6 has a dedicated antenna A having an antenna output terminal formed on the surface of a window glass 10 in addition to a heater wire H. Dedicated antenna A is generally set to F for optimal FM reception.
In order to resonate at M frequency and improve FM directivity,
It has an asymmetric shape. However, even with this method, since the area that can be used as an antenna is small, it is not possible to achieve matching over the entire FM reception frequency band.
Receiving sensitivity is low, and FM directivity is not sufficiently improved. Also, AM reception sensitivity is low. Therefore, in order to increase the FM reception sensitivity and the AM reception sensitivity, an FM compensation amplifier 31 is installed between the antenna output terminal and the feeder F.
and an AM compensation amplifier 32.

0004

In the conventional example described above, it is not possible to achieve matching over the entire FM reception frequency band and the FM reception sensitivity is reduced, so it is necessary to use the FM compensation amplifier 31. When using this FM compensation amplifier 31, a wideband amplifier that covers the entire FM reception frequency band is required, which causes problems such as generation of noise, cross-modulation in a strong electric field, and intermodulation.

The present invention combines a heater wire and a conductor,
It is an object of the present invention to provide a glass antenna for an automobile that has a simple configuration and can perform FM reception well.

[0006]

[Means for solving the problem] A capacitor is provided between the terminal and the vehicle body to ground the terminal of the heater wire for preventing window glass fogging at high frequency, and the heater resonates at the FM frequency but does not resonate at the AM frequency. The heater wire and the conductor are arranged in a positional relationship that creates a state of multiple resonance by electrostatically coupling the wire and a conductor provided on the window glass surface that resonates at FM frequencies but does not resonate at AM frequencies. It is something.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of the present invention.

This embodiment is a glass antenna for an automobile that receives an FM reception frequency and an AM reception frequency, and is composed of a heater wire H1, a wire W1, and a capacitor C.

The heater wire H1 is a heater wire for preventing fogging of a window glass, and is a heater wire that resonates at the FM reception frequency but does not resonate at the AM reception frequency. The wire W1 is F
The wire W1 resonates at the M reception frequency but does not resonate at the AM reception frequency, and is provided on the window glass 10 and has an output terminal, and the feeder F is connected to the output terminal of the wire W1. Note that a portion of the wire W1 forms a coupling capacitance Cc with the heater wire H1.

[0010] Capacitor C is a capacitor that grounds the terminal part of heater wire H1 at high frequency, and its capacitance is:
It only needs to be 500 pF or more, preferably 1000 to 5
000 pF. The heater wire H1 has a folded shape, and one end of its terminal portion is directly grounded to the vehicle body 20, and the other end of the terminal portion is grounded via a capacitor C at a high frequency. Therefore, heater wire H
1 forms an antenna whose one side (right side in the figure) is grounded and the other side (left side in the figure) is open.

At the FM reception frequency, the heater wire H1 and the wire W1 are electrostatically coupled (the coupling capacitance is indicated by Cc), and the heater wire H1 is placed in a positional relationship such that the degree of coupling becomes almost critical coupling. and wire W1 are arranged to form a multiple resonance state. The degree of coupling changes depending on the size of the coupling capacitance Cc formed by the heater wire H1 and a part of the wire W1 and the coupling positional relationship. When the degree of coupling exceeds the critical coupling, the frequency band characteristics (reflection loss characteristics) change from unimodal characteristics to bimodal characteristics. For optimal coupling, use a network analyzer to
While changing the coupling capacitance Cc and the positional relationship between the wire W1 and the wire W1, the conditions for the dimensions and positional relationship are determined so that the necessary frequency bandwidth can be obtained and the reflection loss can be reduced.

[0012] At the AM receiving frequency, only the wire W1 operates as an antenna, so the shape and arrangement of the wire W1 are determined so that the stray capacitance of the wire W1 is reduced. Specifically, the car body 20 and the heater wire H
If the wire W1 is formed at a distance of about 3 centimeters or more from the wire W1, an antenna with small stray capacitance can be obtained.

Next, the operation of the above embodiment will be explained.

First, FM reception will be explained.

FIG. 2 is a diagram showing the principle and equivalent circuit at the FM reception frequency in the above embodiment. At the FM reception frequency, both the wire W1 and the heater wire H1 operate as an antenna, as shown in FIG. 2(1). The wire W1 and the heater wire H1 each resonate with the FM reception frequency,
In addition, the electrostatic coupling forms a multiple resonance state, and the degree of coupling is almost critical, so the frequency band characteristics (reflection loss characteristics) seen from the antenna output terminal (terminal of wire W1) are bimodal. This makes it possible to obtain wide band characteristics. For this reason, it is possible to match the antenna and the feeder F over the entire FM reception frequency band, and good FM reception can be performed without using the FM compensation amplifier 31 that is conventionally required. Furthermore, since the terminal of the heater wire H1 is grounded at high frequency by the capacitor C, it is possible to prevent noise from the power source B from flowing into the heater wire H1.

In the equivalent circuit shown in FIG. 2(2), the equivalent capacitance C1 and the equivalent inductance L of the heater wire H1 are
1. The radiation resistance Ra of the antenna exists conceptually, and the equivalent capacitance C2 and equivalent inductance L2 of the wire W1 also exist conceptually.

Next, AM reception in the above embodiment will be explained.

FIG. 3 is a diagram showing the principle and equivalent circuit at the AM receiving frequency in the above embodiment. At AM reception frequencies, only wire W1 operates as an antenna. This is because the lengths of wire W1 and heater wire H1 are both extremely short compared to the wavelength of the AM reception frequency, and one end of heater wire H1 is grounded, so heater wire H1 is almost equivalent to a ground conductor. , Therefore, there is no electrical connection between the wire W1 and the heater wire H1, and only the wire W1 is connected to A.
Operates as an antenna for M. Therefore, even in AM reception, there is no noise flowing from the power supply B to the wire W1.

Furthermore, in the above embodiment, the wire W1
Since there is a sufficient distance between the antenna and the body 20 (that is, the vehicle body ground plate), the antenna has a small stray capacitance. Therefore, in the above embodiment, since the capacitance division loss due to the antenna capacitance Ca that operates effectively as an antenna and the stray capacitance Cs that operates ineffectively is reduced, an efficient AM
Perform reception.

FIG. 4 is a circuit diagram showing another embodiment of the present invention.

In this embodiment, a compensation circuit consisting of an AM impedance conversion circuit 40 and an FM matching/bypass circuit 50 is inserted between the output terminal of the wire W1 and the feeder F. The AM impedance conversion circuit 40 is
This AM impedance conversion circuit 4 is a converter that converts high impedance for AM reception frequency into a low value.
A specific example of 0 is shown in FIG.

In this way, the AM impedance conversion circuit 4
If 0 is provided, the capacity division loss at the feeder F can be significantly reduced compared to the embodiment shown in FIG.

In the embodiment shown in FIG. 4, the wire W2 resonates at the FM reception frequency in a state including a resonant frequency adjustment capacitor Cf1 and a resonant frequency adjustment inductor Lf1, but the resonant frequency adjustment capacitor Cf1, Either of the resonant frequency adjusting inductors Lf1 may be deleted, or the shape of the wire W2 may be set so that the wire W2 alone resonates at the FM reception frequency. Furthermore, in the embodiment shown in FIG. 4, the heater wire H2 resonates with the FM reception frequency while including the resonance frequency adjustment capacitor Cf2.
A resonant frequency adjustment inductor may be used instead of f2, and the shape of the heater wire H2 may be set so that the heater wire H2 alone resonates with the FM reception frequency. Note that the same applies to the embodiment shown in FIG. 1 in that a capacitor for adjusting the resonance frequency and an inductor for adjusting the resonance frequency may be included to cause resonance at the FM reception frequency.

Further, other conductors may be provided in place of the wire W1. For example, a transparent conductor made of a conductor such as silver or tin thinned to a thickness of about several μm may be used instead of the wire W1. Furthermore, in the above explanation, the case where the FM reception frequency and the AM reception frequency are received was explained as an example, but the FM reception frequency and the AM reception frequency are received.
The same applies to the case where a first reception frequency other than the reception frequency and a second reception frequency other than the AM frequency are received.

[0025]

[Effects of the Invention] According to the present invention, it is possible to achieve matching over the entire FM reception frequency band with a simple configuration, and since the heater is grounded at high frequency, noise from the power supply is removed and the performance is improved. This has the effect that it is possible to perform FM reception. This eliminates the need for the conventionally used FM compensation amplifier, which makes it possible to reduce costs and prevent the generation of noise, cross-modulation distortion, and the like.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention.

[Fig. 2] Principle at FM reception frequency in the above embodiment,
FIG. 3 is a diagram showing an equivalent circuit.

[Fig. 3] Principle at AM reception frequency in the above embodiment,
FIG. 3 is a diagram showing an equivalent circuit.

FIG. 4 is a circuit diagram showing another embodiment of the present invention.

5 is a circuit diagram showing a specific example of the AM impedance conversion circuit 40 in the embodiment shown in FIG. 4. FIG.

FIG. 6 is an explanatory diagram of a conventional example.

[Explanation of symbols]

W1, W2...Wire, H1, H2...heater wire, C...Capacitor B...Power supply, F...feeder, 10...Glass, 20...Body, 40...AM impedance conversion circuit, 50...FM matching/bypass circuit.

Claims (6)

[Claims] Claim 1: A glass antenna for an automobile that receives a first reception frequency and a second reception frequency, wherein the heater wire resonates at the first reception frequency but does not resonate at the second reception frequency. a heater wire for preventing fogging of a window glass, the terminal portion of which is grounded at high frequency by a capacitor; and a conductor provided on the window glass and having an output terminal, which resonates at the first receiving frequency; a conductor that is non-resonant at the second receiving frequency, and the heater wire and the conductor are arranged in a positional relationship such that they are electrostatically coupled to form a multi-resonant state at the first receiving frequency. The heater wire and the conductor are capable of receiving signals at the first reception frequency, and the heater wire and the conductor are not electrically coupled to each other at the second reception frequency, and the heater wire and the conductor are not electrically coupled to each other at the second reception frequency. A glass antenna for an automobile, characterized in that at reception frequency No. 2, reception is performed only through the conductor. 2. The glass antenna for an automobile according to claim 1, wherein the first reception frequency is a frequency of an FM broadcast signal, and the second reception frequency is a frequency of an AM broadcast signal. 3. In claim 1, the heater wire comprises:
The conductor alone has a dimension that resonates at the first reception frequency, or includes a resonant frequency adjustment inductor or a resonant frequency adjustment capacitor and resonates at the first reception frequency, and the conductor shall have dimensions that resonate at the first reception frequency alone, or include a resonant frequency adjustment inductor or a resonant frequency adjustment capacitor and resonate at the first reception frequency. An automotive glass antenna featuring: 4. The glass antenna for an automobile according to claim 1, wherein the heater wire and the conductor are substantially critically coupled at the first reception frequency. 5. In claim 1, the output terminal of the conductor is directly connected to a feeder, or has a matching circuit for the first receiving frequency and a high antenna impedance for the second receiving frequency. A glass antenna for an automobile, characterized in that the antenna is connected to the feeder via a compensation circuit having an active impedance converter that converts the impedance to a lower value. 6. The glass antenna for an automobile according to claim 1, wherein the conductor is a thin film conductor.