JP3648910B2 - Vehicle antenna - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is AM broadcasting, FM broadcasting, suitable for receiving the TV broadcasting, and more particularly to a vehicle antenna which is suitable for providing the antenna conductor on the rear side window glass plate of an automobile.
[0002]
[Prior art]
AM broadcasting, FM broadcasting, TV in broadcasting conventional vehicle glass antenna for receiving, the antenna conductor AT provided an automotive rear left side window glass plate 1a as shown in FIG. 2, the feed point 4a and the circuit 9 Are connected via the first connection line 6, and the circuit 9 and the receiver 20 are connected via the coaxial cable 10, and the feeding point 4 a and the receiver 20 are connected. The circuit 9 is usually a preamplifier, an impedance matching circuit or a resonance circuit.
[0003]
[Problems to be solved by the invention]
However, although the conventional glass antenna for a vehicle in FIG. 2 is compact, there is a problem that the AM broadcast cannot be satisfactorily received in an area where the radio wave is weak due to insufficient sensitivity when receiving the AM broadcast band. The reason for the lack of sensitivity is that the wavelength of radio waves in the AM broadcast band is as long as about 185 m to 575 m, and the conductor length of the antenna conductor AT provided on the window glass plate having a small area is shorter than this wavelength. Therefore, it is desirable to develop an antenna that can be provided on a window glass plate having a small area, can achieve a compact size, can obtain sufficient AM broadcast band sensitivity, and can simultaneously receive FM broadcast bands. It was rare.
[0004]
[Means for Solving the Problems]
The present invention has been made to solve the above-described problems, and in a vehicle antenna that receives a first frequency band and a second frequency band having a frequency higher than the first frequency band,
A first antenna conductor, a second antenna conductor and a first coil are provided in the vehicle;
Connecting the feeding point of the first antenna conductor and one end of the first coil, connecting the feeding point of the second antenna conductor and the other end of the first coil;
The first coil has an inductance value that is high impedance in the second frequency band,
The length of the connection line connecting the feeding point of the first antenna conductor and one end of the first coil is 40 cm or less ,
The second frequency band is FM broadcast band or TV VHF band,
A vehicular antenna is provided, wherein a reception signal at a feeding point of a first antenna conductor is input to a receiver.
[0005]
In the vehicle antenna that receives the first frequency band and the second frequency band having a frequency higher than the first frequency band,
A first antenna conductor, a second antenna conductor and a first coil are provided in the vehicle;
The feeding point of the first antenna conductor and one end of the first coil are connected, the other end of the first coil and one end of the second coil are connected, and the other end of the second coil and the second coil Connect the feeding point of the antenna conductor,
Both the first coil and the second coil have an inductance value that is high impedance in the second frequency band,
The length of the connection line connecting the feeding point of the first antenna conductor and one end of the first coil is 40 cm or less ,
The second frequency band is FM broadcast band or TV VHF band,
Provided is a vehicle antenna in which a stronger one of a reception signal at a feeding point of a first antenna conductor and a reception signal at a feeding point of a second antenna conductor is selected and input to a receiver.
[0006]
Also provided is the above vehicle antenna, wherein the length of the connecting line connecting the feeding point of the first antenna conductor and one end of the first coil is 20 cm or less. Further, the vehicle antenna is provided in which a first antenna conductor is provided on the rear left side window glass plate and a second antenna conductor is provided on the rear right side window glass plate.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention aims to receive two or more frequency bands. The frequency of the second frequency band in the present invention is higher than the frequency of the first frequency band in the present invention. As a representative example, for example, the first frequency band is an AM broadcast band and the second frequency band is an FM broadcast band.
[0008]
Further, it is necessary that the vehicle is provided with two or more antenna conductors. This is because, in the first frequency band, two or more antenna conductors are connected in high frequency, and the effective length of the first antenna conductor is substantially increased to improve the sensitivity of the first frequency band. Therefore, at the time of reception of the first frequency band, reception is performed by increasing the effective length of the first antenna conductor by the sum of the conductor length of the first antenna conductor and the conductor length of the second antenna conductor. Become.
[0009]
Further, when receiving in the second frequency band, reception is performed only by the conductor length of the first antenna conductor. Therefore, it is preferable to make specifications such as the conductor length and shape of the first antenna conductor suitable for reception in the second frequency band.
[0010]
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a typical example of a vehicle antenna according to the present invention. In FIG. 1, 1b is a rear right side window glass plate, AT ₁ is a first antenna conductor, AT ₂ is a second antenna conductor, 4b is a second feeding point, L ₁ is a first coil, and L ₂ is The second coil, 6 is a first connection line, 8 is a second connection line, 11 is a lead wire, and 13 is a second coaxial cable. The second coil L ₂ , the circuit 9, the lead wire 11, and the coaxial cable 13 are provided as necessary, and these are provided as necessary in other drawings.
[0011]
The reception signal received by the first antenna conductor AT ₁ is sent to the circuit 9 through the first connection line 6 and input to the receiver 20 through the coaxial cable 10.
The first coil L ₁ is connected between the first antenna conductor AT ₁ and the second antenna conductor AT ₂ , and has an inductance value that provides a high impedance that attenuates a received signal in the second frequency band. Have. This is to prevent the sensitivity of the second frequency band from being lowered by insulating the first antenna conductor AT ₁ from the second antenna conductor AT ₂ during reception of the second frequency band.
[0012]
The second coil L ₂ is preferably provided. This is to prevent the sensitivity of the second frequency band from being lowered by perfecting the insulation between the _first antenna conductor AT ₁ and the second antenna conductor AT ₂ as much as possible when receiving the second frequency band. Hereinafter, the first coil L ₁ and the second coil L ₂ connecting the plurality of antenna conductors are referred to as connection coils. Third to eighth coils to be described later are also connection coils.
[0013]
The high impedance in the inductance of the first coil L _{1 and} the inductance of the second coil L ₂ usually means more than about 5 times the input impedance on the receiver side. When the second frequency band is, for example, an FM broadcast band, the input impedance on the receiver side at the time of FM broadcast reception is usually 50 or 75Ω. Therefore, for example, when the input impedance on the receiver side is 50Ω, 250Ω or more is high impedance.
[0014]
It is preferable to shorten the connection length between the feeding point of the first antenna conductor and one end of the first coil so as not to attenuate the received signal in the second frequency band. Specifically, the length of the first connecting line 6 for connecting the first feeding point 4a of the antenna conductor AT ₁ and a first one end of the coil L ₁ or less 40 cm. This is because the sensitivity of the second frequency band is lowered.
[0015]
When it is 40 cm or less, the sensitivity of the entire second frequency band is usually improved by 2 to 3 dB or more compared to the case where it is more than 40 cm . Good preferable range is 20cm or less, if it is 20cm or less the sensitivity of the second frequency band throughout as compared to the case of the 20cm than is typically improved over 1 to 2 dB.
[0016]
The end portion of the first coil L ₁ refers to a winding start or end portion, and the first connecting wire 6 and the second connecting wire 8 and the winding of the connecting coil are integrated. Even in this case, the end of the connecting coil refers to a portion at the beginning or end of winding. The same applies to other connecting coils.
[0017]
In FIG. 1, when performing diversity reception, a lead wire 11 and a coaxial cable 13 are provided. At the time of diversity reception, the stronger _one of the reception signal of the _first antenna conductor AT _{1 and} the reception signal of the second antenna conductor AT ₂ is selected by the selection circuit and input to the receiver 20. In the case of performing diversity reception, the receiver 20 of FIG. 1 includes a selection circuit. However, the present invention is not limited to this, and the receiver 20 may not include the selection circuit, and the receiver 20 and the selection circuit may be separated from each other.
[0018]
Preferably the length of the second feed point of the antenna conductor AT ₂ 4b and a second connecting line that connects the one end of the coil L ₂ is less than 40 cm, more preferably at most 20 cm. For the same reason as described above with respect to the length of the first connection line 6.
[0019]
FIG. 3 is a configuration diagram of an example of the vehicle antenna of the present invention of a type different from FIG. In FIG. 3, 3 is a glass plate of the rear window of the vehicle, 22 is a heater wire, 25a and 25b are bus bars, 29 is a choke coil, 30 is a DC power source, 21 is a noise-cutting capacitor, and 12a and 12b are high-frequency choke coils. , 41 are DC blocking capacitors.
[0020]
In the vehicle antenna of the present invention shown in FIG. 3, the defogger composed of the heater wire 22 and the bus bars 25a and 25b is made to function as an antenna, and corresponds to the _second antenna conductor AT2 in FIG. Diversity reception is performed between the first antenna conductor AT ₁ and the defogger.
[0021]
In FIG. 3, the choke coil 29 and the high frequency choke coils 12a and 12b are inserted between the bus bars 25a and 25b and the DC power supply 30 for the defogger, and the impedance of the choke coil 29 and the high frequency choke coils 12a and 12b in the high frequency band. By increasing the DC current, a direct current from the direct current power source 30 to the defogger flows, but a current in a high frequency band such as a broadcast band is cut off.
[0022]
In this manner, the choke coil 29 and the high frequency choke coils 12a and 12b can insulate the defogger heater wire 22 and the bus bars 25a and 25b from the ground of the vehicle body in a high frequency, and the radio induced in the heater wire 22 and the bus bars 25a and 25b. A reception current in a high frequency band such as a broadcast band can be prevented from flowing to the vehicle body ground, and the reception current can be sent to the receiver 20 without leakage.
[0023]
Further, when the first frequency band is a medium wave band, for example, an AM broadcast band, and the second frequency band is an FM broadcast band, if only the AM broadcast band is received using a defogger, a high frequency is used. The choke coils 12a and 12b are usually unnecessary and may be only the choke coil 29. If only the FM broadcast band is received, only the high-frequency choke coils 12a and 12b may be used.
[0024]
Even when both the medium wave band and the FM broadcast band are received, if there is a coil that satisfies the functions of both the choke coil 29 and the high frequency choke coils 12a and 12b, only such a coil is sufficient.
[0025]
FIG. 4 is a configuration diagram of an example of the vehicle antenna of the present invention of a type different from those shown in FIGS. When receiving the first frequency band, the effective length of the first antenna conductor is increased by connecting the _first antenna conductor AT ₁ to the defogger, so that the first antenna conductor AT ₁ and the second antenna performing diversity reception with the conductor aT _2.
[0026]
In the vehicle antenna of FIG. 4, an antenna conductor such as the first antenna conductor may be used instead of the defogger. Alternatively, the bus bar 25a and the receiver 20 may be connected, and diversity reception may be performed between the first antenna conductor AT ₁ , the second antenna conductor AT _2, and the bus bar 25a.
[0027]
In FIG. 4, the first antenna conductor AT ₁ and the second antenna conductor AT ₂ are provided on different window glass plates. However, the first antenna conductor AT ₁ and the second antenna conductor AT ₂ may be provided on the same window glass plate.
[0028]
FIG. 5 is a configuration diagram of an example of the vehicle antenna of the present invention of a type different from those of FIGS. In FIG. 5, AT ₃ is a third antenna conductor, AT ₄ is a fourth antenna conductor, L ₃ is a third coil, L ₄ is a fourth coil, L ₅ is a fifth coil, and L ₆ is a third coil. 6, L ₇ is the seventh coil, L ₈ is the eighth coil, 4 c is the feeding point of the third antenna conductor AT ₃ , 4 d is the feeding point of the fourth antenna conductor AT ₄ , and 40 is the front part It is a glass plate of a window. In the vehicle antenna shown in FIG. 5, diversity reception is performed among four members of the first antenna conductor AT ₁ , the second antenna conductor AT ₂ , the third antenna conductor AT _3, and the fourth antenna conductor AT ₄ . The glass plate of the window on which the first to fourth antenna conductors are provided is not limited to FIG.
[0029]
In the vehicle antenna shown in FIG. 5, the fifth coil L ₅ , the sixth coil L ₆ and its connection line, or the seventh coil L ₇ , the eighth coil L ₈ and its connection line are provided as necessary. Provided.
[0030]
In FIGS. 1, 3, 4, and 5, the antenna conductor is provided on the window glass plate of the vehicle. However, the location of the vehicle where the antenna conductor is provided is not particularly limited. However, for convenience of mounting, each antenna conductor is preferably provided on a window glass plate of a vehicle for compactness. Further, some of the plurality of antenna conductors may be provided on the window glass plate of the vehicle, and the remaining antenna conductor may be provided on a portion other than the window glass plate of the vehicle. The antenna conductor may be a pole antenna other than a glass antenna.
[0031]
In the present invention, when the antenna conductor is provided on the window glass plate of the vehicle, the glass plate of such a window is not particularly limited, and the glass plate of the rear window, the glass plate of the side window, the glass plate of the front window The glass plate of the roof window may be used, and the defogger may not be provided on the glass plate of the window on which the antenna conductor is provided.
[0032]
When the antenna conductor is provided on the window glass plate of the vehicle, the first antenna conductor may be provided on the rear left side window glass plate, and the second antenna conductor may be provided on the rear right side window glass plate. preferable. This is because the directivity is excellent.
[0033]
Further, the antenna conductor in the present invention is not limited to the AM broadcast band (medium wave) and the FM broadcast band, and can be applied to a short wave broadcast band, a long wave broadcast band, and a television VHF band .
[0034]
【Example】
(Examples 1-5)
A vehicle antenna as shown in FIG. 1 was produced. Circuit 9 was a preamplifier. The second coil L ₂ , the lead wire 11 and the coaxial cable 13 were not provided. The dimensions of the rear side window glass plate 1a were approximately 400 mm in the vertical direction and approximately 550 mm in the horizontal direction. The length of the substantially vertical antenna line of the first antenna conductor AT ₁ is 300 mm, and the substantially horizontal antenna line is set so that the AT ₁ conductor length of the first antenna conductor is suitable for FM broadcast band reception. Was 450 mm, the inductance value of the first coil L ₁ was 2.7 μH, and the input impedance of the receiver at the time of FM broadcast reception was 50Ω.
[0035]
First 5cm length of the connecting line 6 for connecting the first feeding point 4a of the antenna conductor AT ₁ and a first end of the coil _{L 1, 15cm, 30cm, 50cm} , the sensitivity of the FM broadcast band as 80 cm - The result of measuring the reception frequency characteristic is shown in FIG. In FIG. 6, B: 5 cm (Example 1), C: 15 cm (Example 2), D: 30 cm (Example 3), E: 50 cm (Example 4), and F: 80 cm (Example 5) (Examples 1 to 3). Are Examples, Examples 4 and 5 are comparative examples).
In addition, Examples 1 to 3 were able to receive AM broadcasts well, and compared to Example 6 below, the average sensitivity of the entire AM broadcast band was improved by approximately 3 dB.
[0036]
(Example 6)
As a comparative example, a vehicle antenna as shown in FIG. 2 was manufactured. The rear side window glass plate 1a and the first antenna conductor AT ₁ were the same as those used in Example 1. FIG. 6A shows the sensitivity-reception frequency characteristic of the FM broadcast band, and FIG. 8 shows the sensitivity-reception frequency characteristic of the AM broadcast band.
[0037]
(Example 7)
A vehicle antenna as shown in FIG. 3 was produced. The rear side window glass plate 1a was the same as that of Example 1 on the left side of the vehicle. The dimensions of the rear window glass plate 3 were approximately 450 mm in the vertical direction and 1200 mm in the horizontal direction. The length of the second connection line 8 was 400 mm, and the length of the first connection line 6 was 15 cm. FIG. 7 shows the sensitivity-reception frequency characteristics of the AM broadcast band of Example 7.
[0038]
The circuit constants of Example 7 are as follows: first coil L ₁ = 2.7 μH, second coil L ₂ = 2.7 μH, capacitor 41 = 20 pF, choke coil 29 = 1 mH, high frequency choke coil 12 a = 1 μH, high frequency Choke coil 12b = 1 μH.
[0039]
【The invention's effect】
In the present invention, since the first antenna conductor and the second antenna conductor are connected in the first frequency band, the effective length of the first antenna conductor is increased, so that the sensitivity in the first frequency band is improved.
[0040]
The first coil has an inductance value such as to attenuate the received signal in the second frequency band, the length of the connecting line between one end of the feeding point of the first antenna conductor and the first coil the The effective length of the first antenna conductor is not increased in the second frequency band so that the received signal in the second frequency band is 40 cm or less so as not to attenuate, and the sensitivity of the second frequency band is difficult to attenuate.
[0041]
In addition, when the received signal of the first antenna conductor is used in the first frequency band, the conductor length of the second antenna conductor can be used, so the area occupied by the first antenna conductor can be reduced, contributing to compactness. it can.
[Brief description of the drawings]
1 is a configuration diagram of a representative example of a vehicle antenna according to the present invention. FIG. 2 is a configuration diagram of a conventional example. FIG. 3 is a configuration diagram of an example of a vehicle antenna according to the present invention of a type different from FIG. 4 is a block diagram of an example of a vehicle antenna of the present invention of a type different from those shown in FIGS. 1 and 3. FIG. 5 is an example of a vehicle antenna of the present invention of a type different from those shown in FIGS. FIG. 6 is a sensitivity-reception frequency characteristic diagram of the FM broadcast band of Examples 1 to 6. FIG. 7 is a sensitivity-reception frequency characteristic diagram of the AM broadcast band of Example 7. FIG. 8 is an AM broadcast band of Example 6. Sensitivity vs. reception frequency characteristics [Explanation of symbols]
AT ₁ : first antenna conductor AT ₂ : second antenna conductor L ₁ : first coil L ₂ : second coil 1 b: rear right side window glass plate 4 a: first feeding point 4 b: second Feeding point 6: first connection line 8: second connection line 9: circuit 10: coaxial cable 20: receiver 22: heater wire 25a, 25b: bus bar 29: choke coil 30: DC power supply 21: for noise cut Capacitors 12a, 12b: high frequency choke coil 41: DC blocking capacitor

Claims (4)

In the vehicle antenna that receives the first frequency band and the second frequency band having a higher frequency than the first frequency band,
A first antenna conductor, a second antenna conductor and a first coil are provided in the vehicle;
Connecting the feeding point of the first antenna conductor and one end of the first coil, connecting the feeding point of the second antenna conductor and the other end of the first coil;
The first coil has an inductance value that is high impedance in the second frequency band,
The length of the connection line connecting the feeding point of the first antenna conductor and one end of the first coil is 40 cm or less ,
The second frequency band is FM broadcast band or TV VHF band,
A vehicle antenna, wherein a reception signal at a feeding point of a first antenna conductor is input to a receiver. In the vehicle antenna that receives the first frequency band and the second frequency band having a higher frequency than the first frequency band,
A first antenna conductor, a second antenna conductor and a first coil are provided in the vehicle;
The feeding point of the first antenna conductor and one end of the first coil are connected, the other end of the first coil and one end of the second coil are connected, the other end of the second coil and the second coil Connect the feeding point of the antenna conductor,
Both the first coil and the second coil have an inductance value that is high impedance in the second frequency band,
The length of the connection line connecting the feeding point of the first antenna conductor and one end of the first coil is 40 cm or less ,
The second frequency band is FM broadcast band or TV VHF band,
A vehicle antenna that selects a stronger one of a received signal at a feeding point of a first antenna conductor and a received signal at a feeding point of a second antenna conductor and inputs the signal to a receiver. The vehicle antenna according to claim 1 or 2, wherein a length of a connection line connecting the feeding point of the first antenna conductor and one end of the first coil is 20 cm or less.   The vehicle antenna according to claim 1, 2 or 3, wherein the first antenna conductor is provided on the rear left side window glass plate and the second antenna conductor is provided on the rear right side window glass plate.

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