JPH10256817A - On-vehicle antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle antenna system in which high sensitivity is obtained regardless of using small sized antenna conductors. SOLUTION: In this antenna system, two antenna conductors 61, 62 are provided to a window glass plate 1, a 1st coil 31 is connected between the 1st antenna conductor 61 and a receiver 20, a 2nd coil 32 is connected between a 2nd antenna conductor 62 and the receiver 20, and three ways of resonance are caused by stray capacitance of the antenna conductors 61, 62 and both the coils.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention has a high receiving sensitivity,
In addition, the present invention relates to a vehicle antenna device having high flatness of reception sensitivity in a band such as a desired broadcast frequency band.

[0002]

2. Description of the Related Art Conventionally, in a glass antenna for receiving an AM broadcast band and an FM broadcast band, in order to compensate for a shortage of the receiving sensitivity of the antenna, a suitable feed line between a feed point of an antenna conductor and a receiver is used. Inserting and connecting a preamplifier to the site has been performed. However, since a preamplifier is inserted, waveform distortion and cross modulation occur in a strong electric field, and there is a problem that noise is amplified as it is. Further, since it is necessary to provide a preamplifier separately from the receiver, productivity is low (conventional example 1).

[0003] In addition, a DC current is not transmitted and received between a defogger of an electric heating type having a heater wire and a bus bar for supplying power to the heater wire, and a predetermined interval is set so that transmission and reception of a medium-high frequency current is performed. In a vehicle glass antenna device (Japanese Patent Laid-Open No. 2-239701, Conventional Example 2) in which a predetermined pattern of antenna conductors which are capacitively coupled in close proximity to each other are provided on the rear window glass plate of the vehicle, the reception sensitivity is as follows. Has been improved.

By connecting a choke coil between the bus bar and the DC power supply for the defogger and increasing the impedance of the choke coil, a DC current flows from the DC power supply to the defogger, but a current in a high frequency band such as a broadcast frequency band does not. I try to shut it off. This capacitive coupling makes the defogger seem to function as part of the antenna. In addition, the impedance of the choke coil and the impedance of the antenna conductor, the defogger, and the vehicle body, each of which is mainly formed by capacitance, are formed so that an anti-resonance resonance frequency exists in a desired broadcast frequency band. I have. In addition, a desired broadcast frequency band is determined by the impedance of a predetermined circuit connected between the feeding point of the antenna conductor and the receiver, the input impedance of the receiver, and the impedance of the antenna conductor as viewed from the predetermined circuit. At a resonance point.

However, in the conventional example 2, the impedance of the choke coil affects the resonance frequency of the anti-resonance, and it is difficult to uniformly manufacture the impedance of the choke coil through which a large current flows. Therefore, the variation of the anti-resonance resonance frequency is large. Further, in the conventional example 2, since the impedance of the choke coil has a strong temperature dependency, the resonance frequency of the anti-resonance greatly changes when the ambient temperature change is large.
As a result, when the anti-resonance frequency exists in the desired broadcast frequency band, the receiving sensitivity is not uniform, and the productivity is poor.

[0006]

SUMMARY OF THE INVENTION The present invention relates to the above-mentioned disadvantages of the prior art (a disadvantage caused by the necessity of providing a preamplifier in the prior art 1, and a choke coil between the bus bar and the DC power supply in the prior art 2). Provided is an antenna device for a vehicle which is excellent in reception sensitivity and productivity for the purpose of eliminating the disadvantage caused by the connection.

[0007]

SUMMARY OF THE INVENTION The present invention provides a vehicular antenna apparatus for receiving a desired broadcast frequency band and transmitting a received signal to a receiver, which satisfies all of the following conditions. . 1) the first antenna conductor and the second antenna conductor are provided on the vehicle; 2) the first coil is connected between the first antenna conductor and the receiver; 3) 4) the second coil is connected between the second antenna conductor and the receiver; 4) the first coil utilizing the inductance of the first coil and the stray ground capacitance of the first antenna conductor. 5) causing the second resonance using the inductance of the second coil and the stray capacitance to the ground of the second antenna conductor; 6) the first resonance The third resonance is generated by utilizing the inductance of the sum of the coil and the second coil, and the capacitance obtained by connecting the stray capacitance of the first antenna conductor to the ground and the stray capacitance of the second antenna conductor to the ground in series. To make it happen.

Further, the present invention provides the above-described vehicle antenna device, wherein the first antenna conductor and the second antenna conductor are provided on a window glass plate of the vehicle. Also, in the present invention, the first coil and the capacitor connected in parallel are connected between the antenna conductor and the receiver, and the capacitor receives a signal in a reception frequency band higher than a desired reception frequency band. The present invention provides the above-described vehicular antenna device having a capacitance value that allows a signal to pass.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a basic configuration diagram of a vehicle antenna device according to the present invention. In FIG. 1, 1 is a rear window glass plate of an automobile, 2 is a heater wire, 3 is a defogger, 41
Is a feeding point of the first antenna conductor, 42 is a feeding point of the second antenna conductor, 5a and 5b are bus bars, 61 is a first antenna conductor, 62 is a second antenna conductor, 7 is a resonance circuit,
10 is a DC power supply, 11 is a capacitor, 19 is a capacitor, 20 is a receiver, 31 is a first coil, and 32 is a second coil.

FIG. 2 is for explaining the principle of FIG. 1 and is an equivalent circuit diagram of the device of FIG. In FIG. 2, i ₁ is a signal current source of the first antenna conductor 61, i ₂
Is a signal current source of the second antenna conductor 62, and C ₁ is a stray capacitance to ground (hereinafter simply referred to as a stray capacitance) of the first antenna conductor 61.
It is the capacity when measuring between the vehicle body ground. C ₂
Is the stray capacitance of the second antenna conductor 62, which is the capacitance measured when the feed point 42 is open and the distance between the feed point 42 and the vehicle body ground is measured. In FIG. 2, other elements such as the stray capacitance of the wiring have little effect on normal reception, and the electrical phenomenon is considered, ignoring them.

In the present invention, three resonances are caused to improve the receiving sensitivity. The first resonance is caused by the inductance of the first coil 31 and the impedance when the first antenna conductor 61 is viewed from the feeding point 41. Impedance when the power supply point 41 viewed first antenna conductor 61 side, mainly composed of the stray capacitance C _1. A first resonant connected artificially capacitor or capacitive component in parallel to the floating capacitance C ₁ may be adjusted. The first coil 31 is usually 1 μm.
About H to 1 mH is used.

The second resonance is caused by the inductance of the second coil 32 and the impedance when the second antenna conductor 62 is viewed from the feeding point 42. Impedance when the feed point 42 viewed second antenna conductor 62 side, mainly composed of the stray capacitance C _2. The second resonance by connecting artificially capacitor or capacitive component in parallel to the floating capacitance C ₂ may be adjusted. The second coil 32 is typically 1 μm
About H to 1 mH is used.

The inductance of the first coil 31 and the second
The third resonance is caused by the inductance of the sum of the inductance of the coil 32 and the capacitance C _{1 + 2} obtained by connecting the ground stray capacitance C ₁ and the ground stray capacitance C ₂ in series. The third resonance may be adjusted by artificially connecting a capacitor or a capacitive component in parallel with at least one of the stray capacitances C ₁ and C ₂ . 1 / C _{1 + 2} = 1 / C ₁ for capacity C _{1 + 2}
+ 1 / C ₂ , that is, C _{1 + 2} = C ₁ · C ₂ / (C ₁ +
C ₂ ).

The first resonance, the second resonance, and the third resonance include a first antenna conductor 61 and a second antenna conductor 62, respectively.
The stray capacitance of the wiring also has a slight effect. For example, the stray capacitance of the wiring such as the first coil 31 and the second coil 32, the stray capacitance of the cable connecting the first antenna conductor 61 and the receiver, and the second antenna conductor 62 and the receiver Is the stray capacitance of the cable connecting

FIGS. 3 and 4 are circuit diagrams for explaining the equivalent circuit of FIG. In FIG. 2, the signal current source i ₂ = 0
Assuming (zero), the equivalent circuit of FIG. 2 is represented as shown in FIG. When it is assumed that the signal current source i ₁ = 0 (zero), the equivalent circuit of FIG. 2 is represented as shown in FIG. Therefore, in the circuit of FIG. 2, each phenomenon that can occur in the circuit of FIG. 3 and the circuit of FIG. 4 can occur. This is because the internal resistance of the signal current source is infinite, and the principle of superposition is applied.

As described above, the equivalent circuit shown in FIG. 2 is obtained by superposing the equivalent circuit shown in FIG. 3 and the equivalent circuit shown in FIG. 3 and 4, the first coil 31, the second coil 32
It is explained that the third resonance is caused by the capacitance C _{1 + 2} .

In the present invention, three resonances are caused by
This is because a wide reception frequency band cannot be covered by only two resonances. It is desirable to divide the reception frequency band into three, and to share each of them with three resonances to achieve flat reception sensitivity. Here, the flattening of the receiving sensitivity refers to reducing the difference between the highest receiving sensitivity and the lowest receiving sensitivity within a band such as a receiving frequency band.

Further, the highest frequency of the reception frequency band is f _H ,
The center frequency of the reception frequency band f _M, the lowest frequency of the reception frequency band f _L, the first f _r1 resonance frequency of the resonance, the second f _r2 the resonance frequency of the resonance, the resonant frequency of the third resonance f
_{When r3} is satisfied, it is preferable to satisfy all of the following conditions a) to c) in terms of flattening the receiving sensitivity.

[0019] a) 2f _H /3~1.5f _{H (H} band) to be present either the f _r1 or f _r2, b) a f _L ~2f _H / 3 (M bands) to f _r3 be _{present, c) 0.5f L ~f M (} L -band) to be present other remaining of f _r1 or f _r2.

If any of the above conditions a) to c) is not satisfied, it is usually difficult to make the difference between the highest and lowest reception sensitivities within the reception frequency band less than about 8 dB. In addition, the flattening of the receiving sensitivity in the receiving frequency band is inferior.

FIG. 5 is a typical circuit diagram of an application example of the resonance circuit 7. In FIG. 5, 35 is a bypass capacitor, and 36 and 37 are damping resistors. Resistance 3
6, 37 are provided as needed. The resonance circuit 7 is not limited to the one shown in FIG. 3, and may additionally include a damping resistor, a resonance adjustment capacitor, and the like. The capacitor 35 is provided as needed, and is provided when receiving a desired reception frequency band and a reception frequency band (high frequency band) higher in frequency than the desired reception frequency band.

Between the first antenna conductor 61 and the receiver 20, the one in which the first coil 31 and the capacitor 35 are connected in parallel is connected. As in the case of FIG. 1, the inductance value of the first coil 31 is set to a low impedance at least in a desired reception frequency band.

The term "low impedance" refers to an impedance within a range in which a signal received by the first antenna conductor 61 easily flows to the receiver side, and is usually five times or less the input impedance of the receiver side. The input impedance on the receiver side usually means the input impedance of the receiver.
However, when an impedance converter is connected between the input of the receiver and the antenna, it refers to the input impedance of the impedance converter.

The high impedance refers to an impedance within a range in which a signal received by the first antenna conductor 61 hardly flows to the receiver side, and usually means more than five times the input impedance of the receiver side.

When the desired reception frequency band is AM broadcasting, the input impedance of the receiver at the time of receiving AM broadcasting is usually 1 to 10 kΩ. Therefore, for example, when the input impedance on the receiver side is 5 kΩ,
25 kΩ or less has low impedance, and 25 kΩ or more has high impedance.

When the high frequency band is FM broadcast, the input impedance of the receiver at the time of receiving FM broadcast is usually 50 or 75Ω. So, for example,
If the input impedance on the receiver side is 50Ω, 250Ω or less becomes low impedance and 250Ω
Super becomes high impedance.

The capacitor 35 has a capacitance value such that the impedance becomes low in a high frequency band and becomes high in a desired reception frequency band. In other words, the capacitor 35 has a capacitance value that allows the reception signal in the high frequency band to pass.

Therefore, the received signal in the high frequency band excited by the first antenna conductor 61 is sent to the receiver via the capacitor 35. Usually, the capacitance value of the capacitor 35 is about 1 to 1000 pF. For example, when the desired reception frequency band is the AM broadcast band and the high frequency band is the FM broadcast band, the capacitance value of the capacitor 35 is 5.0 to 3
A range of 3 pF is preferred. The damping resistor 36 is
For adjusting the Q (quality factor) of the first resonance,
The damping resistor 37 is for adjusting the Q of the second resonance.

The patterns of the first antenna conductor 61 and the second antenna conductor 62 may be selected from AM broadcast, FM broadcast, and A broadcast depending on the shape of the automobile, the shape, size, and configuration of the glass plate.
A pattern that can obtain the optimum performance as an antenna for both M broadcast and FM broadcast radio broadcasting or television and other broadcasting is designed as appropriate.

Further, the first antenna conductor 6 shown in FIG.
The first and second antenna conductors 62 are not provided with auxiliary antenna conductors. However, the present invention is not limited to this. For the purpose of phase adjustment and directivity adjustment, a substantially T-shaped, substantially L-shaped, loop, or the like may be provided on the conductor pattern or the feeding point of the antenna conductor with or without a connection conductor. May be additionally provided.

With respect to the positions of the first antenna conductor 61 and the second antenna conductor 62, taking the example of FIG. 1 as an example, the antenna conductor may be provided anywhere in the margins at the top, bottom, left, and right of the defogger of the window glass plate 1. Well, it is not limited to the position shown in FIG. Further, the number of antenna conductors provided on window glass plate 1 is not limited. The antenna conductor provided on the window glass plate 1 is not limited to the AM and FM radio broadcasting bands, but can be applied to television VHF bands, television UHF bands, telephones, and the like.

Further, in the present invention, the number of antenna conductors provided on a vehicle other than the first antenna conductor and the second antenna conductor is not limited, and the glass antenna device of the present invention, the pole antenna device and the like are not limited. Diversity reception may be performed with another antenna device and / or another glass antenna device.

As an example of the diversity reception, the first antenna conductor and the second antenna conductor are provided on the rear window glass plate, and the antenna conductor of another glass antenna device is provided on the rear side window glass plate (side glass antenna device). And diversity reception between the vehicle antenna device of the present invention and the side glass antenna device.

As another example of the diversity reception, a first antenna conductor and a second antenna conductor are provided on a rear window glass plate, and another first antenna conductor and a second antenna conductor are provided.
Is provided on the rear side window glass plate, and diversity reception is performed between the two devices.

In FIG. 1, the first antenna conductor 61 and the second
Are provided on the same window glass plate for convenience in mounting. However, in order to improve reception sensitivity and directivity, it is preferable that the first antenna conductor 61 and the second antenna conductor 62 be provided on different window glass plates. When provided on different window glass plates, the difference in reception characteristics between the first antenna conductor 61 and the second antenna conductor 62 is greater than when provided on the same window glass plate. This is because the shortfall can be compensated. An example is given in which the first antenna conductor 61 is provided on one of the rear side window glass plates and the second antenna conductor 62 is provided on the rear side window glass plate on the remaining side.

When the first antenna conductor 61 and the second antenna conductor 62 are provided on the same window glass plate, it is preferable that the two are not brought close to each other and are hardly capacitively coupled. In the case where both are brought close to each other and capacitively coupled, FIG.
This is because the circuit of FIG. 3 cannot be considered separately from the circuit of FIG. 3 and the circuit of FIG. 4, and the third resonance hardly occurs. Usually, if the distance between the two is more than 30 mm, the capacitive coupling becomes difficult.

In FIG. 1, the power supply point is arranged on the right peripheral portion of the rear window glass plate 1. However, the present invention is not limited to this, and may be provided at any position of the rear window glass plate 1, for example, may be provided at the upper and lower peripheral edges of the left and right center of the rear window glass plate 1.

The first antenna conductor 61, the second antenna conductor 62, the heater wire 2, and the bus bars 5a, 5b
Usually, a conductive metal-containing paste such as a conductive silver paste is printed on the interior surface of a window glass plate and manufactured by baking and the like, but is not limited to such a forming method.
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.

In the present invention, when the antenna conductor is provided on the window glass plate, the window glass plate 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 defogger may not be provided on the window glass plate on which the antenna conductor is provided.

[0040]

EXAMPLE A vehicle antenna device as shown in FIG. 1 was manufactured. The resonance circuit 7 shown in FIG. 5 was used, and each circuit constant was as follows. First coil 31 = 180 μH,
Second coil 32 = 800 μH, bypass capacitor 35 = 10 pF, capacitor 19 = 2400 pF, damping resistor 36 = 15 kΩ, damping resistor 37 = 6.8 kΩ, stray capacitance C _{1 of first} antenna conductor 61 = 50 pF, stray capacitance C of the second antenna conductor 62
₂ = 40 pF.

The shortest distance between the first antenna conductor 61 and the second antenna conductor 62 was 50 mm, and was not capacitively coupled. FIG. 6 shows the measurement results of the reception sensitivity for the AM broadcast frequency band. In FIG. 6, 870 m
A pole antenna of length m is approximately 0 dB. The FM broadcast frequency band was almost equivalent to a pole antenna having a length of 500 mm (within ± 2 dB). Also, f _r1
Almost 1400kHz, f _r2 is almost is 700kHz, f _r3
Was approximately 880 kHz.

[0042]

According to the present invention, it is not necessary to insert and connect a preamplifier between the feeding point of the antenna conductor and the receiver. Does not occur and the noise is amplified as it is, and the productivity is good.

Further, according to the present invention, the first resonance, the second resonance, and the third resonance are caused, so that the reception sensitivity in a desired reception frequency band can be improved and the reception can be performed with excellent flatness. .

Further, when the present invention is applied to a rear window glass plate provided with a defogger, the reception sensitivity in a desired reception frequency band can be improved without using the defogger as an antenna. That is, high sensitivity can be obtained even when the antenna conductor is small and small. Therefore, the size of the glass antenna device can be reduced, the receiving sensitivity becomes uniform for each vehicle, and the productivity is excellent.

Furthermore, since it is not necessary to supply a large current to the first coil and the second coil, the windings of the first coil and the second coil can be made thinner, and the windings of the first coil and the second coil can be reduced. The impedance can be made uniform and the temperature dependency can be extremely reduced. As a result, the receiving sensitivity hardly varies from vehicle to vehicle, and the receiving sensitivity is relatively stable even when the ambient temperature of the vehicle greatly changes.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a vehicle antenna device of the present invention.

FIG. 2 is an equivalent circuit diagram of FIG.

FIG. 3 is a circuit diagram for explaining the equivalent circuit of FIG. 2;

FIG. 4 is a circuit diagram for explaining the equivalent circuit of FIG. 2;

FIG. 5 is a typical circuit diagram of an application example of the resonance circuit 7;

FIG. 6 is a frequency characteristic diagram of the receiving sensitivity of the embodiment.

[Explanation of symbols]

1: Rear window glass plate of automobile 2: Heater wire 3: Defogger 41: Feeding point of antenna conductor 42: Feeding point of antenna conductor 5a, 5b: Bus bar 61: First antenna conductor 62: Second antenna conductor 7: resonant circuit 9: choke coil 10: DC power supply 11: capacitor 20: receiver 31: first coil 32: second coil 35: bypass capacitors 36 and 37: resistor for damping C _1: first antenna Stray capacitance of conductor 61 C ₂ : Stray capacitance of second antenna conductor 62

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tetsuro Hashimoto 426-1 Ozawa Uehara, Kakuda, Aikawa-cho, Aiko-gun, Kanagawa Pref.

Claims (3)

[Claims] 1. A vehicular antenna apparatus for receiving a desired broadcast frequency band and transmitting a reception signal to a receiver, wherein the vehicular antenna apparatus satisfies all of the following conditions. 1) the first antenna conductor and the second antenna conductor are provided on the vehicle; 2) the first coil is connected between the first antenna conductor and the receiver; 3) 4) the second coil is connected between the second antenna conductor and the receiver; 4) the first coil utilizing the inductance of the first coil and the stray ground capacitance of the first antenna conductor. 5) causing the second resonance using the inductance of the second coil and the stray capacitance to the ground of the second antenna conductor; 6) the first resonance The third resonance is generated by utilizing the inductance of the sum of the coil and the second coil, and the capacitance obtained by connecting the stray capacitance of the first antenna conductor to the ground and the stray capacitance of the second antenna conductor to the ground in series. To make it happen. 2. The vehicle antenna device according to claim 1, wherein the first antenna conductor and the second antenna conductor are provided on a window glass plate of the vehicle. 3. A reception signal in a reception frequency band having a frequency higher than a desired reception frequency band, wherein a first coil and a capacitor connected in parallel are connected between the antenna conductor and the receiver. The antenna device for a vehicle according to claim 1, wherein the antenna device has a capacitance value that allows passage of the antenna.