JPH1188215A - Glass antenna system for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute reception with low noise and high reception even in a low or high receiving frequency bands by providing first and second coils resonating with a floating capacity and providing a third coil serially connected with the first coil with impedance improving impedance matching. SOLUTION: In a low receiving frequency band, serial resonance is generated by a floating capacity C. and the inductance of the first coil L1 . In addition, parallel resonance is generated by a floating capacity C2 and the inductance of the second coil L2 . In a high receiving frequency band, as are low in their self resonance frequencies, the first and second coils L1 and L2 lose inductance. Then the third coil L3 losing no inductance is serially connected with the first coil L1 and the third coil L3 is provided with impedance improving the impedance matching of the input impedance of a receiver 6 and impedance at the time of looking at the side of an antenna conductor 1 from the input side of the receiver 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to radio, television,
The present invention relates to a glass antenna device for an automobile used for receiving telephone and satellite communications.

[0002]

2. Description of the Related Art Conventionally, in a glass antenna of an automobile, 530 to 1605 kHz, that is, a medium wave broadcasting band (MW) is used.
In order to improve the sensitivity of the band, a circuit as shown in FIG. 9 is adopted, and the stray capacitance C ₁ to the ground of the antenna conductor 1 of the window glass plate (hereinafter, the stray capacitance to the ground may be simply referred to as stray capacitance). In series with the first coil L ₁ and in parallel with the stray capacitance C ₂ of the cable and the second coil L ₂ . In FIG. 9, the dotted lines are lines not connected by conductor lines.

[0003]

In this conventional example, FM
In the broadcast band (FM band), the television VHF band, and the television UHF band, the impedance matching between the input impedance of the receiver and the impedance when the antenna conductor side is viewed from the input side of the receiver is not matched. Reception of VHF band and television UHF band was difficult.

An object of the present invention is to solve the above-mentioned disadvantages of the prior art, and to provide a MW band, a long wave band (LW band) or a short wave band (SW).
The present invention provides a glass antenna device for an automobile that can receive a low reception frequency band such as a band with low noise and high sensitivity and can also receive the FM band, the television VHF band and the television UHF band with low noise and high sensitivity.

[0005]

According to the present invention, an antenna conductor is provided on a window glass plate of an automobile, and a first coil which causes series resonance with a stray capacitance to ground of the antenna conductor in a low reception frequency band is provided. A second coil that causes parallel resonance with a stray capacitance to ground of a cable that transmits a reception signal of an antenna conductor to a receiver in a low reception frequency band, and a second coil that is connected in series with the first coil. 3 coil is provided, and in a high reception frequency band, the third coil has an impedance that improves impedance matching between the input impedance of the receiver and the impedance when the antenna conductor side is viewed from the input side of the receiver. A glass antenna device for an automobile is provided.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram of a typical example of a glass antenna device for a vehicle according to the present invention. In FIG. 1, 1 is an antenna conductor provided on a window glass plate of an automobile, L ₁ is a first coil, L ₂ is a second coil, L ₃ is a third coil, L
Fourth coil provided if necessary _4, C ₁ is the stray capacitance of the antenna conductor 1, C ₂ is the stray capacitance of the cable, C
_{Numeral 3} denotes a coupling capacitor for blocking direct current provided as required, and numeral 6 denotes a receiver. In FIG. 1, dotted lines are lines not connected by conductor lines.

[0007] The antenna conductor 1 functions as an antenna for both low reception frequency band reception and high reception frequency band reception. Here, the cable refers to a cable for connecting the ends of the receiver side of the coupling capacitor C ₃ and the receiver 6. This cable transmits the signal received on the antenna conductor 1 to the receiver. The reception signal of the antenna conductor 1 is transmitted to the first coil L ₁ , the third coil L ₃ , and the coupling capacitor C ₃ in this order.
The received signal is sent to the receiver 6. In the low receiving frequency band, parallel resonance occurs between the antenna conductor 1 of the stray capacitance C ₂ and the second coil L ₂ watches receiver from side inductance. This is the parallel resonance also affect the coil L ₁ of the stray capacitance C ₁ and the first. When the parallel resonance is caused, the sensitivity in the entire low reception frequency band is usually improved by about 5 dB or more as compared with the case where the parallel resonance is not caused.

In the present invention, series resonance mainly occurs with the stray capacitance C ₁ and the inductance of the first coil L ₁ . The stray capacitance C ₂ and the second coil L ₂ also affect the series resonance. When the series resonance is caused, the sensitivity in the entire low receiving frequency band is usually improved by about 5 dB or more as compared with the case where the series resonance is not caused. The stray capacitance of the wiring around the antenna conductor 1 slightly affects the series resonance. For example, the first
Of a stray capacitance of the coil L ₁ and the second coil L ₂ and the like of the wiring.

In the high receiving frequency band, the first coil L
_{Since the first} and second coils L ₂ have low self-resonant frequencies,
It loses inductance and exhibits capacitive impedance. For this reason, the input impedance (Z
_Ri ) and the impedance (Z _AO ) when the antenna conductor 1 is viewed from the input side of the receiver 6 is usually in a poor state of impedance matching.

Therefore, in the high receiving frequency band, the third coil L ₃ which does not lose inductance is replaced with the first coil L ₃ .
₁ , and the third coil L ₃ is connected to Z _Ri and Z
By having an impedance that improves impedance matching with _AO , Z
The impedance matching between _Ri and Z _AO is improved so that not only reception in a low reception frequency band but also reception in a high reception frequency band can be performed.

Here, improving the impedance matching means reducing the absolute value of the reflection coefficient G. The reflection coefficient G is expressed by the following equation (1).

[0012]

G = (Z _Ri −Z _AO ) / (Z _Ri −Z _AO ) (1)

When improving the impedance matching, when the third coil L ₃ is connected in series with the first coil L ₁ , the third coil L ₃ is connected in series with the first coil L _1. It is preferable to make the absolute value of the reflection coefficient G smaller by 0.1 or more than in the case where it is not performed. Number d
This is because the sensitivity in the B high reception frequency band is usually improved.

[0014] In the high receiving frequency band is also a fourth coil L _4, using the coil not to lose the inductance. When the impedance matching between Z _Ri and Z _AO cannot be adjusted with only the third coil L ₃ , the impedance matching is adjusted with the fourth coil L ₄ .

The third coil L ₃ and the fourth coil L ₄ are preferably air-core wound coils having good high-frequency characteristics. However, if a satisfactory specification is obtained, a ferrite core winding type, a ferrite monolithic coil, or a coil formed by winding a wiring pattern or a lead wire on a printed wiring board showing inductance can be used.

FIG. 2 shows an equivalent circuit of FIG. 1 in a high reception frequency band. 2, the capacitance C _L1 is the capacitance possessed by the first coil L _1, capacitor C _L2 is capacitance of the second coil L _2, capacitor C _L3 is capacitance of the third coil L _3, the capacitance C _L4 is capacitance of the fourth coil L _4, the inductance H _L3 is inductance of the third coil L _3, the inductance H _L4 is inductance of the fourth coil L _4. Incidentally, the stray capacitance C ₁ and the floating capacitance C ₂ is omitted.

The glass antenna device of the present invention is not limited to the MW band and the FM band, but can be applied to the LW band, the SW band, the TV VHF band, the TV UHF band, the telephone, and the like. The number of antenna conductors provided on the plate is not limited.

The window glass plate provided with the glass antenna device of the present invention is not limited to the rear window glass plate, but may be a side window glass plate, a front window glass plate, a roof window glass plate, or the like.

The antenna conductor is usually manufactured by printing and baking a conductive metal-containing paste such as a conductive silver paste on the inner surface of the window glass plate, but is not limited to this forming method. Instead, a conductive linear body or foil-like body such as a copper wire may be formed on the inside or outside surface of the windowpane, or may be provided inside the windowpane. Further, the antenna conductor may be made of a transparent conductive material.

[0020]

【Example】

"Example 1 (Example)" A glass antenna device having a circuit as shown in FIG. 1 was manufactured on the premise of reception in the MW band and the FM band. However, it was short-circuited without the fourth coil L ₄ are provided.

The values of the respective circuit constants in the MW band are shown below. The inductance of the first coil L ₁ = 150 μH, the inductance of the second coil L ₂ = 470 μH, the stray capacitance C ₁ of the antenna conductor ₁ = 65 pF, and the stray capacitance C _{2 of the} cable = 140 pF.

The values of each circuit constant in the FM band are shown below. Capacitance C _L1 = 10.0 pF, capacitance C _L2 = 2.5 pF, capacitance C _L3 = 1.0 pF, inductance H _L3 = 330 nH.

FIG. 3 shows the frequency characteristic (solid line) of impedance when the antenna side is viewed from the cable by using the Smith chart. FIG. 4 shows the frequency characteristic of the absolute value of the reflection coefficient when the antenna is viewed from the cable (solid line). As shown in FIG. 4, the reflection coefficient is improved over the entire region. FIG. 5 shows the frequency characteristics of the sensitivity in the FM band (solid line).

[0024] Except that a short circuit is not provided "Example 2 (Comparative Example)" third coil L ₃ were fabricated glass antenna device having a circuit similar to Example 1. FIGS. 3 and 6 show frequency characteristics (dotted lines) of impedance when the antenna side is viewed from the cable by using the Smith chart. 4 and 7 show the frequency characteristics of the absolute value of the reflection coefficient when the antenna is viewed from the cable (dotted line). 5 and 8 show the frequency characteristics of the sensitivity in the FM band (dotted lines).

[0025] except that "Example 3 (Example)" fourth coil L ₄ are add was fabricated glass antenna device having a circuit similar to Example 1. The values of the circuit constants in the FM band are shown below. Capacitance C _L4 = 1.0 pF, inductance H _L4 = 470 nH.

FIG. 6 shows the frequency characteristic of the impedance (solid line) when the antenna side is viewed from the cable by using the Smith chart. FIG. 7 shows the frequency characteristic of the absolute value of the reflection coefficient when the antenna side is viewed from the cable. FIG. 8 shows the frequency characteristics of the sensitivity in the FM band (solid line).

[0027]

According to the present invention, in the low receiving frequency band, the first coil causes series resonance with the stray capacitance of the antenna conductor with respect to ground, and the second coil causes parallel resonance with the stray capacitance of the cable with respect to ground. The sensitivity of the low reception frequency band is improved, and the impedance matching between Z _Ri and Z _AO is improved by the action of the third coil connected in series with the first coil. Sensitivity is also improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a typical example of a glass antenna device for a vehicle according to the present invention.

FIG. 2 is an equivalent circuit diagram of FIG.

FIG. 3 is a frequency characteristic diagram of impedance when the antenna side is viewed from the cables of Examples 1 and 2.

FIG. 4 is a frequency characteristic diagram of an absolute value of a reflection coefficient when the antenna side is viewed from the cables of Examples 1 and 2.

FIG. 5 is a diagram showing frequency characteristics of sensitivity in an FM band in Examples 1 and 2.

FIG. 6 is a frequency characteristic diagram of impedance when the antenna side is viewed from the cables of Examples 2 and 3.

FIG. 7 is a frequency characteristic diagram of the absolute value of the reflection coefficient when the antenna side is viewed from the cables of Examples 2 and 3.

FIG. 8 is a frequency characteristic diagram of sensitivity in an FM band in Examples 2 and 3.

FIG. 9 is a circuit diagram of a conventional glass antenna device for an automobile.

[Explanation of symbols]

1: Antenna conductor L _1: the first coil L _2: the second coil L _3: the third coil L _4: Fourth coil L ₄ C _1: the stray capacitance of the antenna conductor 1 C _2: the stray capacitance of the cable C ₃ : coupling capacitor 6: receiver

Claims (1)

[Claims] An antenna conductor is provided on a window glass plate of an automobile, and a first coil which causes series resonance with a stray capacitance with respect to a ground of the antenna conductor is provided in a low reception frequency band. A second coil that causes parallel resonance with a stray capacitance to ground of a cable that transmits a reception signal of the antenna conductor to the receiver, a third coil connected in series with the first coil,
In a high reception frequency band, the third coil has an impedance for improving impedance matching between an input impedance of the receiver and an impedance when the antenna conductor side is viewed from the input side of the receiver. Antenna device.