JP3508217B2 - Automotive glass antenna device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass antenna device for an automobile, which has a high receiving sensitivity and a high receiving sensitivity in a desired broadcast frequency band.

[0002]

2. Description of the Related Art Conventionally, in a glass antenna for receiving AM broadcast frequency band (hereinafter referred to as AM band) and FM broadcast frequency band (hereinafter referred to as FM band), in order to compensate for the lack of receiving sensitivity of the antenna, the antenna conductor It has been practiced to insert a preamplifier at a suitable part of the power supply line between the power supply terminal and the receiver. However, due to the insertion of the preamplifier, there is a problem that waveform distortion, intermodulation, etc. occur in a strong electric field and the noise is amplified as it is.

Further, in this conventional example, since it is necessary to install the preamplifier separately from the receiver, there is a problem that productivity is considerably deteriorated, and it is difficult to install the preamplifier near the glass antenna. there was a problem that Ru given the constraints on the design of the automobile in the space reserved or the like for the preamplifier. Therefore, it has been desired to develop a glass antenna device for an automobile, which does not require a preamplifier, has high reception sensitivity, has low noise, and is nondirectional.

To solve this, Japanese Patent Laid-Open No. 23970/1990
According to Japanese Unexamined Patent Publication No. 1-1989, a DC current is not transmitted and received between a defogger of an electrically heated type having a heater wire and a bus bar for feeding the heater wire to a glass plate of a rear window of an automobile, but a medium-high frequency current is not transmitted. As the transmission and reception of the antenna conductor is performed by providing a predetermined pattern which is closely coupled at a predetermined interval so as to be capacitively coupled, a reactance circuit is inserted between the bus bar and the DC power source for the defogger, and the antenna conductor, the defogger, and the vehicle body. Between the impedance of the capacitance formed by each of them and the impedance of the reactance circuit, the anti-resonance point exists within the desired broadcast frequency band, and the point between the feeding point of the antenna conductor and the receiver is set. The impedance of a given circuit inserted in the antenna, the input impedance of the receiver, and the antenna conductor from the given circuit By the impedance seen,
There has been proposed a glass antenna device for an automobile in which a resonance point is present in a desired broadcast frequency band.

However, those of this proposal, since both the resonance point and antiresonance point was Tei is present <br/> within a desired broadcast frequency band, in the broadcast frequency band throughout to flatten the reception sensitivity it is difficult to appropriately reduce the value of Q (quality factor) by the circuit configuration, the reception sensitivity and to try receiving sensitivity flat had poor of that drawback.

Further, although the reason is not always clear, noise is likely to occur in the vicinity of the anti-resonance point. Therefore, if the anti-resonance point exists in the desired broadcast frequency band, it will be reflected outside the band such as the desired broadcast frequency band. compared to the resonance point exists, there is a drawback S / N ratio may turn poor several dB.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned drawbacks of the prior art, does not require a preamplifier, and has high reception gain, low noise, no distortion, no mixed modulation, and no directivity. In addition, a glass antenna device for an automobile, which is excellent in flatness of frequency characteristics of reception sensitivity, is newly provided.

[0008]

DISCLOSURE OF THE INVENTION The present invention relates to an electrically heated defogger having a heater wire and a bus bar for supplying power to the heater wire on a glass plate of a rear window of an automobile, and transmitting and receiving a direct current between the defogger. provided an antenna conductor having a predetermined pattern is brought close at a defogger and predetermined distance by capacitive coupling as is done sending and receiving performed not but the medium to high frequency currents, the DC power supply bus bar and defogger <br / > Insert a reactance circuit between the antenna conductor feeding point
In a glass antenna device for an automobile in which a predetermined circuit is inserted between a receiver and a receiver , the impedance of the antenna conductor, the defogger, and the vehicle body, which are mainly formed by mutual capacitance, and the impedance of the reactance circuit The anti-resonance point exists outside the desired reception frequency band or outside the desired broadcast frequency band, and the maximum frequency of the desired reception frequency band or the desired broadcast frequency band is f
_H, if the desired reception frequency band or the lowest frequency of a desired broadcast frequency band and a f _L, the impedance of the circuit of Jo Tokoro, the input impedance of the receiver, by the impedance viewed antenna conductor side from a prescribed circuit , A frequency of 1.5 times f _H and a resonance point between f _L and a glass antenna device for an automobile are provided.

Further, the present invention provides a desired reception frequency band, or a desired broadcast frequency band, the low range than these bands, the main antenna conductor, defogger, each of the vehicle body is formed with one another providing the impedance consisting of capacitance, the glass antenna equipment for a motor vehicle, characterized in that so as to anti-resonance by the impedance of the reactance circuit.

Further, according to the present invention, a direct current is not transmitted / received between the defogger of the electrically heating type having the heater wire and the bus bar for feeding the heater wire to the glass plate of the rear window of the automobile, and the defogger. However, to transmit and receive medium- and high-frequency currents, a defogger and an antenna conductor of a predetermined pattern that is capacitively coupled in close proximity to each other at a predetermined interval are provided, and a reactance circuit is inserted between the bus bar and the DC power supply for the defogger. , Antenna conductor feed point and receiver
In automotive glass antenna device with inserted a predetermined circuit between the antenna conductor, defogger, each of the vehicle body and the impedance composed mainly of capacitance forming mutually, by the impedance of the reactance circuit, the desired Outside the reception frequency band or outside the desired broadcast frequency band, the maximum frequency of the desired reception frequency band or the desired broadcast frequency band is f _H , and the minimum frequency of the desired reception frequency band or the desired broadcast frequency band is f _L If, then (2 /
3) - (as anti-resonance point between f _L ² / f _H) and f _L is present, the impedance of the circuit of Jo Tokoro, the input impedance of the receiver, the antenna conductor side from a prescribed circuit F _L + (f _H −f
There is provided a glass antenna device for an automobile, characterized in that a resonance point is present between _L ). (0.3) and (1.2) .f _H.

Further, according to the present invention, a direct current is not transmitted / received between the defogger of the electrically heated type having the heater wire and the bus bar for feeding the heater wire to the glass plate of the rear window of the automobile, and the defogger. However, to transmit and receive medium- and high-frequency currents, a defogger and an antenna conductor of a predetermined pattern that is capacitively coupled in close proximity to each other at a predetermined interval are provided, and a reactance circuit is inserted between the bus bar and the DC power supply for the defogger. , Antenna conductor feed point and receiver
In automotive glass antenna device with inserted a predetermined circuit between the antenna conductor, defogger, each of the vehicle body and the impedance composed mainly of capacitance forming mutually, by the impedance of the reactance circuit, the desired Outside the reception frequency band or outside the desired broadcast frequency band, the maximum frequency of the desired reception frequency band or the desired broadcast frequency band is f _H , and the minimum frequency of the desired reception frequency band or the desired broadcast frequency band is f _L And (2/3) ・
If (f _L ² / f _H ) = f _arL , then f _arL + (f _L
-F arL) · (0.25) and (0.9) · f _L as anti-resonance point exists between the impedance of the circuit of Jo Tokoro, the input impedance of the receiver, a predetermined circuit From the impedance seen from the antenna conductor side,
There is provided a glass antenna device for an automobile, characterized in that a resonance point exists between _L + (f _H -f _L ) · (0.6) and f _H.

Further, according to the present invention , the Q value is such that the difference between the maximum reception sensitivity and the minimum reception sensitivity is in the range of about 1 dB to about 16 dB within the desired reception frequency band or within the desired broadcast frequency band. to provide the glass antenna equipment for a motor vehicle, characterized in that setting the circuit constant of the predetermined circuit and the reactance circuit.

Further, the present invention, the glass antenna equipment for a motor vehicle, characterized in that consists of circuit reactance circuit is connected between the high-frequency coil and the choke coil in series
To provide.

Further, the present invention is connected in parallel to the resistor to the choke coil of the reactance circuit, the glass antenna equipment for the automobile, characterized in that to adjust the Q
To provide.

[0015]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration diagram of a typical example of a glass antenna device for an automobile of the present invention. In FIG. 1, 1 is a glass plate of a rear window of an automobile, 2 is a heater wire, 2a is the highest heater wire,
3 is a defogger, 3a is a defogger branch line, 4 is a feeding point of an antenna conductor, 5a, 5b and 5c are bus bars,
6 is an antenna conductor, 6a is an adjacent portion of the antenna conductor 6 to the defogger 3, 7 is a matching circuit which is a " predetermined circuit " in the present invention , 8 is a reactance circuit, 9 is a heater transformer, 10 is a DC power source, 11 is Condenser, 12
a and 12b are high frequency coils, 14 is a coil, 15 is a resistor, 16 is a capacitor, 18 is a coil for FM band, 1
9 is a condenser, 20 is a receiver, 25 is a cable, 3
0 and 31 are resistors.

[0017] The glass plate 1 of the rear window, usually 3~5mm
Tempered glass of thickness about or laminated glass or the like is used. An electrically heated defogger having a large number of heater wires 2 and opposing bus bars 5a, 5b and bus bars 5c connected to both ends of the heater wire 2 group in a heated area on the inner surface of the glass plate 1 of the rear window. 3 are provided, and lead wires are connected to the bus bars 5a and 5b of the defogger 3.

In the defogger 3 shown in FIG. 1, the bus bars on the right side of the bus bars on both sides of the defogger 3 are vertically divided into two parts from a desired position, and a lower side bus bar 5a and an upper side bus bar 5b are provided. A vehicle body side ground lead wire is connected to the lower bus bar 5a, and the upper bus bar 5a
The lead wire on the power source side is connected to b. The supplied current flows from the upper side bus bar 5b through the bus bar 5c to the lower side bus bar 5a in a U-shape.

Referring to the defogger 3 shown in FIG. 1, the defogger is composed of the heater wire 2 and the bus bars 5a, 5b and 5c. The heater wire usually has a line width of 0.
It consists of forming a large number of thin heater wires 2 of 5 to 2 mm for electric heating at a distance of 2 to 4 cm substantially parallel to the lateral direction on the glass plate. Further, bus bars 5 a, 5 b, 5 c for supplying current to the heater wire 2 are formed on both sides of the heater wire 2. Heater wire 2 and bus bars 5a, 5b, 5c
Is usually manufactured by printing a conductive metal-containing paste such as a conductive silver paste on the inside surface of a glass plate and baking it.

With respect to the antenna conductor 6, in the case of FIG. 1, the antenna conductor 6 is provided in the margin above the defogger 3 of the glass plate 1. The branch line 3 a adjacent portion 6a and the defogger of the antenna conductor 6, which is close at predetermined intervals, and the antenna conductor 6 and the defogger 3 This proximity is not performed transmission and reception of the direct current therebetween However, they are capacitively coupled so that medium and high frequency currents can be transmitted and received.

[0021] The branch line 3 a adjacent portion 6a and the defogger of the antenna conductor 6 is spaced for example at intervals of about 0.2～30Mm. The defogger 3 apparently functions as a part of the antenna due to this capacitive coupling. Especially for AM band, Defogger 3
Also functions as a part of the antenna for AM broadcasting, and the effective length of the antenna for AM broadcasting becomes long, so that a large amount of received radio waves can be received and the receiving sensitivity is improved.

In the FM band, the opening of the vehicle body for attaching the glass plate 1 of the rear window and the defogger 3 have a role of a projector or a reflector with respect to the antenna conductor 6. On the other hand, since a leakage current flows from the antenna conductor 6 to the opening of the vehicle body and the defogger 3, the defogger 3
The loss of the reception signal from is blocked by the high-frequency coils 12a and 12b, which improves the reception sensitivity.

In the defogger 3 shown in FIG. 1,
A branch line 3a is provided on the highest heater wire 2a of the defogger 3. Branch line 3a of the defogger 3 extends from the vicinity of the center of the highest heating wire 2a as shown in FIG. 1 in the vertical direction, substantially T-shape so as to branch horizontally in the vicinity of the adjacent portion 6a of the antenna conductor 6 Has become. Less because noise that does not flow Heater current in the branch line 3a,
Furthermore, the reception sensitivity is improved by the capacitive coupling between the antenna conductor 6 and the defogger 3 described above.

However, the branch line 3a of the Defogger may have any shape as long as it has the above-mentioned function, and is not limited to the shape shown in FIG. For example, the shape may be such that it extends vertically from the left or right side of the highest heater wire 2a and extends horizontally to the opposite side near the adjacent portion 6a. The branch line 3a of the defogger can be replaced with a part of the heater wire 2 or a part of the bus bars 5a, 5b, 5c, and the branch line 3a may be omitted. However, in view of the above noise, it is preferable to provide the branch line 3a.

19 and 20 are front views of a defogger having a pattern different from that of FIG. The defogger that can be used in the present invention is not limited to the defogger shown in FIG. 1, and even the defogger shown in FIGS. 19 and 20 can be used in the present invention.

As described above, in order to partially capacitively couple the defogger 3 and the antenna conductor 6, the surface on which the defogger 3 is provided and the surface on which the antenna conductor 6 is provided are usually rear portions. is flush with the glass plate 1 of the window, it is best to form the interior side of the glass plate 1. The pattern of the antenna conductor 6, the shape of the automobile, the shape of the glass plate, the dimensions, AM broadcast due arrangement, FM broadcasting, both radio broadcast shared AM broadcasting and FM broadcasting, or as an antenna for television and other broadcasting The pattern that provides the optimum performance is appropriately selected and designed.

Regarding the position of the glass plate 1 on which the antenna conductor 6 is provided, FIG. 1 shows an example in which the antenna conductor 6 is provided in the margin above the defogger 3 of the glass plate 1. The position is not limited to the position shown in, and may be a blank part below the defogger 3 of the glass plate 1.
Ku, rather it may also be respectively provided on the upper and lower portions of the defogger, it may be provided to other margin.

In the present invention, the reactance circuit 8 is provided between the bus bars 5a and 5b and the DC power source 10 for the defogger.
Is inserted, and the impedance of the reactance circuit 8 is increased in the middle and high frequency bands so that the direct current from the direct current power supply 10 to the defogger 3 flows but the current in the middle and high frequency bands such as the broadcast frequency band is cut off. . In this way, the reactance circuit 8 can insulate the heater wire 2 of the defogger 3 and the bus bars 5a, 5b, 5c from the ground of the vehicle body in a high-frequency manner, and the radio broadcast induced in the heater wire 2 and the bus bars 5a, 5b, 5c. It is possible to prevent the reception current in the middle and high frequency bands such as the frequency band from flowing to the vehicle body ground, and to send this reception current to the receiver 20 without leakage.

In FIG. 1, the reactance circuit 8 is composed of a heater transformer 9, high frequency coils 12a and 12b, and a capacitor 11 provided as needed. Also,
Resistors 30 and 31 are added as needed to form the reactance circuit 8.

The structure of the reactance circuit 8 is not limited to the structure shown in FIG. 1, and any circuit may be used as long as it has a function of preventing the reception current in the medium and high frequency bands such as the radio broadcasting frequency band from flowing to the vehicle body ground. It can be used in various circuits.
For example, when only the AM band is received, the reactance circuit 8 may be configured only by the heater transformer 9, and when only the FM band is received, the reactance circuit 8 may be formed by only the high frequency coils 12a and 12b. You may comprise. Further, even when receiving both the AM band and the FM band, the heater transformer 9, the high frequency coil 12a,
If there is a coil that fulfills both functions of 12b, the reactance circuit 8 may be configured by only this coil.

Heater transformer 9 in reactance circuit 8
It is preferable that the choke coil has a characteristic that it has a relatively high impedance in a medium and high frequency band such as a radio broadcast frequency band and prevents magnetic residual. For example, a high frequency choke coil in which a toroidal magnetic core (Mn-Zn ferrite or the like) is bifilar wound , a high frequency choke coil wound in a direction in which magnetic fluxes of coils generated by a current from a closed magnetic circuit are mutually canceled , or a magnetic A high frequency choke coil using a core with a high degree of saturation and the like are exemplified.

Regarding the adjustment of the choke coil of the heater transformer 9, in order to obtain the required inductance, self-resonant frequency and Q value, for example, the core is divided into two, the interval between the cores is adjusted, or the cores are predetermined in parallel. The adjustment is performed by connecting the capacitor of, or changing the coil pitch.

Since the resistors 30 and 31 are damping resistors for adjusting the Q value of anti-resonance, they can be omitted if the Q values are proper without the resistors 30 and 31. . The resistors 30 and 31 may be fixed resistance elements normally used in electronic circuits, or semiconductors such as transistors and FETs may be used.

The capacitor 11 in the reactance circuit 8 is electrically short-circuited with respect to a noisy current having a high frequency component (for example, one that is mixed through a lead wire) in the medium and high frequency bands such as the radio broadcasting frequency band. To do. Instead of providing the capacitor 11, a filter may be provided between the reactance circuit 8 and the DC power supply 10.

High frequency coil 12 in reactance circuit 8
a and 12b have high impedance in the FM band, and normally use solenoids or magnetic cores that do not use magnetic cores. These have inductive reactance in the FM band and in the vicinity of the FM band. Further, as the high frequency coils 12a and 12b, there may be a case where a lead wire having an appropriate length can be used, and further, the same effect may be obtained depending on the arrangement of the reactance circuit 8 in the vehicle body.
Since the choke coil of the heater transformer 9 has a low self-resonant frequency in the FM band and loses inductance,
The high frequency coils 12a and 12b substitute for this.

Further, in the present invention, the antenna conductor 6
This feeding point 4 and the desired position of the path between the receiver 20
The matching circuit 7 which is the " predetermined circuit " in the invention is inserted, and the medium and high frequency currents induced in the antenna conductor 6 are seen from the impedance of the matching circuit 7, the input impedance of the receiver 20, and the antenna conductor side from the matching circuit. The receiver 20 resonates with the impedance.
Sent to.

The matching circuit 7 shown in FIG.
The circuit is composed of the elements 4, 18, the capacitor 16 and the resistor 15, but is not limited to this, and any circuit configuration can be used as long as it is a circuit that causes a predetermined resonance. In the matching circuit 7 shown in FIG.
In the M band, the impedance characteristic is determined by the coil 14, the capacitor 16, and the resistor 15. The resistor 15 is a so-called damping resistor, which is used to adjust the Q of resonance, and when adjustment of Q is not necessary, the resistor 15 is used.
Can be omitted.

Further, since the self-resonant frequency of the coil 14 is low in the FM band, the coil 14 is regarded as a capacitive reactance, so the coil 14 can be omitted. In the FM band, the coil 18 contributes to cause a predetermined resonance. Therefore, the coil 18 is not necessary when the FM band is not received.

The matching circuit 7 also has a function of performing impedance matching between the input of the receiver 20 and the feeding point 4 of the antenna conductor. Further, the predetermined circuit also means a circuit that does not have a function of performing such impedance matching.

As described above, in the FM band, the coil 18
Impedance characteristics are defined by Ni-Z
n-ferrite core coil, solenoid coil,
As the coil 18, a spiral coil or a coil utilizing the inductance of a lead wire connected to the matching circuit 7 can be used.

Further, as described above, the antenna conductor 6 and the defogger 3 are usually formed by print-printing a conductive silver paste on the surface of a glass plate and baking it. In this case, migration of printed silver or the like may occur between the adjacent portion 6a and the branch line 3a that are close to each other, causing a short circuit between them and causing a large current to flow to the receiver 20. . In order to prevent this, a DC blocking capacitor 19 may be inserted between the feeding point 4 of the antenna conductor 6 and the matching circuit 7.

The capacitor 19 and the matching circuit 7 shown in FIG.
The wiring can be changed as shown in FIGS. 21 and 22, your same members as in FIG. 1 by the same reference numerals
Ri, 21, 1 and part of the same sign of Figure 22 is the same in FIG. 1
Flip is a sign of the part and the same function. Therefore, in FIGS. 21 and 22, the capacitor 19 is a DC blocking capacitor and may be omitted in some cases.

Further, in the FM band, as in the case of FIG. 1, the coil 18 contributes to causing a predetermined resonance, so that the coil 18 is not necessary when the FM band is not received.

In the AM band, the impedance characteristic is determined by the coil 14, the capacitor 16 and the resistor 15. The resistor 15 is a so-called damping resistor, which is used to adjust the Q of resonance, and the resistor 15 can be omitted when the adjustment of Q is not necessary.

In addition to the above, the matching circuit 7
In the present invention, the antenna conductor,
Outside the desired reception frequency band or outside the desired broadcasting frequency band such as the FM band and the AM band , depending on the impedance of the defogger and the vehicle body, which mainly consists of the electrostatic capacitance, and the impedance of the reactance circuit. Anti-resonance point exists, the maximum frequency of the desired reception frequency band or the desired broadcast frequency band is f _H , and the minimum frequency of the desired reception frequency band or the desired broadcast frequency band is f _{H.
When L} is set, f _H is determined by the impedance of a predetermined circuit inserted between the feeding point of the antenna conductor and the receiver, the input impedance of the receiver, and the impedance of the antenna conductor side viewed from the predetermined circuit. It is necessary to have a resonance point between the frequency of 1.5 times and f _L.

The reason for doing this is that if it is outside this range, it becomes difficult not only to flatten the receiving sensitivity in the desired receiving frequency band, but also within the desired receiving frequency band or the desired broadcast frequency. If there is an anti-resonance point in the band, the reason is not always clear, but noise tends to occur in the vicinity of the anti-resonance point, so compare with the existence of an anti-resonance point outside the desired reception frequency band, etc. This is because the S / N ratio deteriorates by several dB.

Further, in order to further improve the receiving sensitivity by several dB, a low band outside the desired receiving frequency band or the desired broadcasting frequency band (a frequency lower than the broadcasting frequency band, etc.)
It is desirable to anti-resonate.

[0048] Further, the resonance that put the present invention, the scope of anti-resonance is desired highest frequency f _H of the receiving frequency band or a desired broadcast frequency band, the lowest desired reception frequency band or a desired broadcast frequency band If the frequency is f _L , (2 /
3) ・ An antiresonance point is allowed to exist between (f _L ² / f _H ) and f _L, and f _L + (f _H −f _L ) · (0.3) and (1.2) · The existence of a resonance point between f _H and
The flatness of the reception sensitivity can be improved by about 1 to 2 dB or more, which is more desirable.

Further, (2/3) · (f _L ² / f _H ) =
If you have a _{f arL, f arL + (f} L -f arL) · (0.
25) and (0.9) · f _{L so} that an anti-resonance point exists, and f _L + (f _H −f _L ) · (0.6) and f _H
It is possible to improve the flatness of the reception sensitivity by about 1 to 2 dB or more by allowing a resonance point to exist between
Especially desirable. Here, the flatness of the reception sensitivity means that the difference between the highest reception sensitivity and the lowest reception sensitivity is small and flat within a band such as a desired broadcast frequency band.

Based on the above-mentioned calculation formulas, for example, A
For the M band and the FM band, the usable ranges of the resonance point and the anti-resonance point, etc., are obtained as shown in Table 1. In addition,
Although only the AM band and the FM band of the medium wave are shown in Table 1 below, the required range of the resonance point and the antiresonance point can be determined by the same method for the short wave and the long wave.

In order to satisfy the above conditions, since the impedances of the antenna conductor 6 and the defogger 3 are fixed, the circuit constants of the matching circuit 7 and the reactance circuit 8 are usually changed to change the anti-resonance point and the resonance. Adjust the position of the dots.

[0052] In the matching circuit 7 that put to the present invention, in the AM band, capacitor 19 560pF~1μF,
The capacitor 16 is 5 to 220 pF, and the coil 14 is 82 to
The resistance is preferably set to 700 μH, the resistance 15 to 0.2 to 10 kΩ, and the coil 18 to 0.1 to 10 μH in the FM band. On the other hand, the choke coil of the heater transformer 8 connected to the defogger 3 is 0.1 to 5 mH in the AM band,
Is preferably set to be respectively coils 12a, 12b are 1~5μH the FM band, the capacitive coupling portion between the branch line 3a to the adjacent section 6a, 10 in the FM band and AM band
It is preferably 1000 pF. Also, the cable 25
A coaxial cable, a feeder line or the like is usually used for.

Of course, these values are only typical ones, and can be changed so that optimum performance can be obtained according to the target glass antenna device for an automobile. In addition, it is desirable for noise that the vehicle body ground, which is the negative electrode of the cable 25, and the vehicle body ground, which is the negative electrode of the DC power supply 10, be separated by 30 cm or more, preferably 60 cm or more.

The matching circuit 7 resonates with the whole antenna to be an antenna and the input impedance of the receiver 20 .
By making the reactance a little capacitive and giving the matching circuit 7 a role of a low-pass filter, the matching circuit 7 can absorb noise such as white noise, and a low noise antenna can be obtained.

Matching circuit 7 or reactance circuit 8
Regarding the Q that sets the circuit constant of, the difference between the maximum receiving sensitivity and the minimum receiving sensitivity is about 1 dB within the band of the desired receiving frequency band so that the receiving sensitivity becomes as flat as possible in the desired receiving frequency band. It is preferable to set it in the range of about 16 dB.

The difference between the maximum receiving sensitivity and the minimum receiving sensitivity is about 1
If it is less than dB, the effects of anti-resonance and resonance are almost eliminated, and the average receiving sensitivity is lowered by several dB to tens of dB, which is not preferable. If the difference between the maximum receiving sensitivity and the minimum receiving sensitivity exceeds about 16 dB, not only the receiving sensitivity greatly varies, but also the frequency characteristics of the receiving sensitivity of individual products become large, which is not preferable.

A more desirable range of the difference between the maximum receiving sensitivity and the minimum receiving sensitivity is in the range of about 2 dB to about 13 dB,
A particularly desirable range is from about 4 dB to about 10 dB. By setting the difference between the highest receiving sensitivity and the lowest receiving sensitivity within the above range, the power efficiency from the antenna including the antenna conductor 6 to the receiver 20 can be improved, and the received signal generated in the antenna by the incoming radio wave can be improved. High-frequency current can be sent to the receiver 20 side without leakage, and high-reception sensitivity can be received.

[0058]

In the present invention, outside the band such as the desired broadcast frequency band,
The anti-resonance reduces the leakage current of the defogger 3 to a frequency of 1.5 times f _H of the desired broadcast frequency band and f _L.
By using a matching circuit to cause resonance, the reception sensitivity is maintained over the entire broadcast frequency band and the like. The reason for this is that the reactance circuit 8 and the matching circuit 7 cannot cover the entire desired broadcast frequency band or the like by themselves.

Further, when the reactance circuit 8 is used to cause anti-resonance, the reception sensitivity is rapidly attenuated in a region lower than the anti-resonance point. Therefore, anti-resonance is low outside the desired reception frequency band or the like. Anti-resonance in the region is preferable. In order to simplify the explanation, a case where both AM and FM radio broadcast reception is assumed and anti-resonance is performed in this low range will be described as an example.

The present invention is based on the following technical idea, in which the impedance of the reactance circuit 8 causes an object to be an antenna to anti-resonate in the above low range and the like, and the received current induced in the degger 3 is applied to the vehicle body. It is intended to prevent the electric current from flowing to the ground and to improve the receiving sensitivity by making the antenna and the matching circuit resonate in the predetermined frequency range.

In the glass antenna device for an automobile of the present invention, the impedance of the antenna conductor 6, the defogger 3, the opening of the rear window, that is, the three elements of the vehicle body, which are mainly formed by the mutual capacitance, and the impedance of the reactance circuit 8 are used. An anti-resonance phenomenon is generated outside a band such as a desired reception frequency band.

For example, regarding the reactance circuit 8,
In the AM band, the inductance of each of the coils 12a and 12b is sufficiently smaller than the inductance of the heater transformer 9 and can be ignored. Further, in the FM band, the heater transformer 9 has a low self-resonance frequency, so that it has a capacitive reactance, and the coils 12a and 12b perform a high-frequency current cutoff function.

In the above case, it is better to appropriately reduce the Q value in both the FM band and the AM band.
Band, high-frequency current in the received signal reception sensitivity induced in the planarized by a defogger in AM band each broadcast band leakage current is on average less composed leaks to the vehicle body.

The defogger 3 and the antenna conductor 6 are connected to each other in the medium and high frequencies in the FM band and the AM band by capacitive coupling between the adjacent portion 6a and the branch line 3a of the defogger. Since the defogger 3 is in the state and is insulated from the vehicle body ground in the FM band and the AM band , the defogger 3 also functions as an antenna like the antenna conductor 6.

Further, the resonance in the AM band and the FM band will be described in detail by taking the matching circuit 7 shown in FIG. 1 as an example.

In the AM band, the capacitor 16 has a relatively high impedance and is in a state almost the same as the case where it is not provided. Therefore, the impedance of the matching circuit 7 is determined by the coil 14 and the resistor 15.
The resonance frequency, which is the resonance point, is determined by the impedance of the matching circuit 7, the impedance of the whole thing to be an antenna (impedance when the antenna conductor side is viewed from a predetermined circuit) and the input impedance of the receiver 20, and is a damping resistance. Q by a resistor 15
Is set to the optimum value, the reception sensitivity with excellent flatness can be obtained in the AM band.

In the FM band, the coil 14 and the resistor 15
Becomes a little capacitive reactance due to the stray capacitance of each component, resulting in an unstable impedance. On the other hand, the capacitor 16 is short-circuited in the FM band, so that the impedances of the coil 14 and the resistor 15 can be ignored. In the FM band, since only the coil 18 is effective in the matching circuit 7, the coil 18 resonates with the whole thing to be the antenna and the input impedance of the receiver 20, and the received signal received by the antenna is resonated. Optimally transmitted to the receiver 20. With the above, high receiving sensitivity can be obtained.

[0068]

EXAMPLE In the glass antenna device for an automobile of the present invention shown in FIG. 1, Table 2, Table 3 and Table 4 show the conditions of each sample. In addition, in Tables 2 and 3, the choke coil of the heater transformer 9 is simply referred to as a choke coil.

Samples 1 to 7 are applicable to the glass antenna device for automobiles for the AM band , and regarding the values of each element constituting the circuit, the capacitor 19 is 1000 p
F, capacitor 16 is 10 pF, adjacent portion 6a and branch line 3
a is 90 pF, and the capacitor 11 is 2.
It was set to 2 μF. Values of the coil 14 and the resistor 15, the inductance of the choke coil of the heater transformer 9, the resistor 30,
The values of 31 are shown in the corresponding tables of Table 2, Table 3 and Table 4.

The capacitance of the antenna cable portion between the feeding point 4 of the antenna conductor 6 and the input end of the receiver 20 was 30 pF / m in the AM band. FIGS. 2 to 8 show frequency characteristic diagrams of the reception sensitivity of the glass antenna device with respect to the AM band, and FIG. 17 shows the result of measuring the characteristic of the S / N ratio.

In samples 1 to 4, since the antiresonance point is far from the AM band, the influence of noise generated near the antiresonance point has almost no influence on the reception in the AM band. Furthermore, samples 3 and 4 had high flatness and could be received very well.

FIGS. 2 to 8 show the frequency characteristics of the reception sensitivity for the AM band obtained for each frequency when the electric field strength is set to 60 dBμV / m near the glass antenna.
As compared with the frequency characteristics of the conventional glass antenna with a preamplifier (simply referred to as a glass antenna with an amplifier in each figure) shown in FIG. 4, it can be seen that the receiving sensitivity is large as a whole.

FIG. 17 shows the characteristics of the S / N ratio at the time of non-modulation and at the time of modulation for each electric field strength when the carrier frequency of sample 5 is 400 Hz. It should be noted that the non-modulation condition is a modulation factor = 0, and the modulation condition is a modulation factor = 30%. Regarding the S / N ratio, there is almost no difference in the strong electric field from the conventional glass antenna with preamplifier, but in the weak electric field, the glass antenna device of the present invention obtains better results.

Sample 7 is a comparative example and has frequency characteristics as shown in FIG.
Since z) exists in the band of the AM band, the influence of noise generated near the anti-resonance point affects reception of the AM band, which is not preferable.

The S / N ratio of the anti-resonance point (600 kHz) of the sample 7 (FIG. 8) which is a comparative example is compared with the S / N ratio of 600 kHz of the sample 3 (FIG. 4) which is an example. It was about 2 dB worse.

As described above, in the glass antenna device of the present invention, as compared with the conventional glass antenna with a preamplifier in which the preamplifier is used to improve the reception sensitivity in the AM band, the same or higher high reception sensitivity is obtained. In addition, a received signal with low noise can be obtained in a normal weak electric field.

In the AM band reception, the antiresonance point was set at 1700 kHz and the resonance point was set at 800 kHz, each circuit constant was determined, and the frequency characteristic of the receiving sensitivity was measured (not shown). The difference between the minimum receiving sensitivity was about 16 dB, and good reception was possible.

Explaining the FM band, 76 to 90M
Samples 8 to 12 correspond to the frequency band of Hz,
Sample 13 for the 88 to 108 MHz frequency band
~ 15 are applicable. Regarding the value of each component that is effective in the FM band, the capacitor 19 is 1000p in the FM band.
F, the capacitor 16 was 10 pF, and the antenna cable portion between the feeding point 4 of the antenna conductor 6 and the input end of the receiver 20 was 30 pF / m. The values of the coil 18 and the coils 12a and 12b are shown in Table 4.

The frequency characteristics of the receiving sensitivity of the antenna for the FM band of samples 8 to 15 are shown in FIGS. The anti-resonance points of Samples 8 to 10 and Samples 13 and 14 are F.
Since it is far from the M band, the influence of noise generated in the vicinity of the anti-resonance point hardly affects the reception in the FM band. Furthermore, the samples 10 and 14 had high flatness and could be received very well. The directivity characteristic of the sample 10 is shown in FIG.
Thus, it was proved that the glass antenna device of the present invention has high reception sensitivity and omnidirectionality.

Sample 12 as a comparative example (see FIG.
The S / N ratio of the anti-resonance point (80 MHz) of 3) was about 1 dB worse than the S / N ratio of 80 MHz of the sample 10 (FIG. 11) which is an example.

[0081]

[Table 1]

[0082]

[Table 2]

[0083]

[Table 3]

[0084]

[Table 4]

[0085]

According to the present invention, in a desired reception frequency band or a desired broadcasting frequency band, there is provided a glass antenna device for an automobile, which has a high gain, low noise and omnidirectionality and a high reception performance without a preamplifier. Can be provided. In particular, AM broadcasting can be received with high reception sensitivity and low noise.

Further, FM broadcasting can be received with high reception sensitivity and omnidirectionality, and the frequency characteristic of reception sensitivity is highly flat. Similarly, it can be applied to other broadcast waves. Therefore,
The preamplifier, which has been indispensable to use in the past, can be removed, which can contribute to productivity.

Further, when the preamplifier is installed in the vicinity of the glass antenna as in the conventional case, there is a constraint condition in the design of the automobile, but according to the present invention, it is sufficient to provide a simple predetermined circuit. Therefore, this constraint condition can be eliminated.

Further, it is possible to obtain the frequency characteristic of the receiving sensitivity with high flatness without lowering the receiving sensitivity in the entire band such as the desired broadcast frequency band. Further, since the antiresonance point is not included in the band such as the desired broadcast frequency band, the effect of noise generated in the vicinity of the antiresonance point is small, and the effect that the desired broadcast or the like can be received with low noise is also recognized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a typical example of a glass antenna device for an automobile of the present invention.

FIG. 2 is a frequency characteristic diagram of reception sensitivity of sample 1.

FIG. 3 is a frequency characteristic diagram of reception sensitivity of sample 2.

FIG. 4 is a frequency characteristic diagram of reception sensitivity of sample 3.

FIG. 5 is a frequency characteristic diagram of reception sensitivity of sample 4.

FIG. 6 is a frequency characteristic diagram of reception sensitivity of sample 5.

FIG. 7 is a frequency characteristic diagram of reception sensitivity of sample 6.

FIG. 8 is a frequency characteristic diagram of reception sensitivity of sample 7.

9 is a frequency characteristic diagram of reception sensitivity of sample 8. FIG.

FIG. 10 is a frequency characteristic diagram of reception sensitivity of sample 9.

FIG. 11 is a frequency characteristic diagram of reception sensitivity of sample 10.

FIG. 12 is a frequency characteristic diagram of reception sensitivity of sample 11.

FIG. 13 is a frequency characteristic diagram of reception sensitivity of sample 12.

FIG. 14 is a frequency characteristic diagram of reception sensitivity of sample 13.

FIG. 15 is a frequency characteristic diagram of reception sensitivity of sample 14.

16 is a frequency characteristic diagram of reception sensitivity of sample 15. FIG.

FIG. 17 is a characteristic diagram of the S / N ratio of sample 5.

FIG. 18 is a characteristic diagram of directivity of Sample 10.

FIG. 19 is a front view of a defogger having a shape pattern different from that of FIG. 1.

20 is a front view of a defogger having a shape pattern different from that of FIG. 1. FIG.

FIG. 21 is a circuit diagram of a matching circuit having a different configuration from that of FIG. 1 and peripheral circuits.

FIG. 22 is a circuit diagram of a matching circuit having a different configuration from that of FIG. 1 and peripheral circuits.

[Explanation of symbols]

1: Glass plate 2: Heater wire 3: Defogger 4: Feeding point of antenna conductor 6 5a, 5b, 5c: Bus bar 6: Antenna conductor 7: Matching circuit 8: Reactance circuit 9: Heater transformer

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-326917 (JP, A) JP-A-4-365204 (JP, A) JP-A-2-239701 (JP, A) Actual development Sho-61- 189612 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01Q 1/32

Claims (7)

(57) [Claims] 1. A medium- and high-frequency current is transmitted and received between a defogger of an electrically heated type having a heater wire and a bus bar for feeding the heater wire to a glass plate of a rear window of an automobile, and a direct current is not transmitted between the defogger. The transmission and reception of the differential
An antenna conductor of a predetermined pattern that is capacitively coupled in close proximity to the ogger at a predetermined distance is provided, and a reactance circuit is inserted between the bus bar and the DC power source for the Defogger, and the feeding point of the antenna conductor and the receiver are connected. Predetermined circuit in between
In the glass antenna device for automobiles, in which the antenna conductor, the defogger, and the vehicle body are mutually formed, the impedance mainly composed of the capacitance and the impedance of the reactance circuit are outside the desired reception frequency band or desired. The anti-resonance point exists outside the broadcast frequency band, the desired reception frequency band or the highest frequency of the desired broadcast frequency band is f _H , and the lowest frequency of the desired reception frequency band or the desired broadcast frequency band is f _L. If we, the impedance of the circuit of Jo Tokoro, the input impedance of the receiver, by the impedance viewed antenna conductor side from a predetermined circuit, a resonance point between the frequency 1.5 times and f _L of f _H is A glass antenna device for an automobile, characterized in that it is present. 2. Outside the desired reception frequency band or outside the desired broadcast frequency band, and in a range lower than these frequency bands,
The glass antenna device for an automobile according to claim 1, wherein the antenna conductor, the defogger, and the vehicle body are made to resonate with each other by impedance formed mainly of capacitance and impedance of the reactance circuit. 3. A medium- and high-frequency current is 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 on a glass plate of a rear window of an automobile, and a direct current is not transmitted between the defogger. The transmission and reception of the differential
An antenna conductor of a predetermined pattern that is capacitively coupled in close proximity to the ogger at a predetermined distance is provided, and a reactance circuit is inserted between the bus bar and the DC power source for the Defogger, and the feeding point of the antenna conductor and the receiver are connected. Predetermined circuit in between
In automotive glass antenna device with inserts, the antenna conductor, defogger, each of the vehicle body and the impedance composed mainly of capacitance forming mutually, by the impedance of the reactance circuit, desired reception frequency band or desired Outside the broadcast frequency band, if the desired reception frequency band or the highest frequency of the desired broadcast frequency band is f _H , and the lowest frequency of the desired reception frequency band or the desired broadcast frequency band is f _L , then (2 / 3) - (as anti-resonance point between f _L ² / f _H) and f _L is present, the impedance of the circuit of Jo Tokoro, the input impedance of the receiver, the antenna conductor side from a prescribed circuit F _L + (f _H −f _L ) · (0.3) and (1.2) · f _H
A glass antenna device for an automobile, characterized in that a resonance point exists between and. 4. An electric heating type defogger having a heater wire and a bus bar for feeding the heater wire to a glass plate of a rear window of an automobile, and a direct current is not transmitted and received between the defogger, but a medium and high frequency current. The transmission and reception of the differential
An antenna conductor of a predetermined pattern that is capacitively coupled in close proximity to the ogger at a predetermined distance is provided, and a reactance circuit is inserted between the bus bar and the DC power source for the Defogger, and the feeding point of the antenna conductor and the receiver are connected. Predetermined circuit in between
In automotive glass antenna device with inserts, the antenna conductor, defogger, each of the vehicle body and the impedance composed mainly of capacitance forming mutually, by the impedance of the reactance circuit, desired reception frequency band or desired Outside the broadcast frequency band, the highest frequency of the desired reception frequency band or the desired broadcast frequency band is f _H , and the lowest frequency of the desired reception frequency band or the desired broadcast frequency band is f _L , (2/3)・ If (f _L ² / f _H ) = _{far arL} , then _{far ar} + (f _{L −far ar} ) · (0.25) and (0.9)
· F as anti-resonance point exists between the _{L, the} impedance of the circuit of Jo Tokoro, the input impedance of the receiver, by the impedance viewed antenna conductor side from a prescribed circuit, f _L + (f _H A glass antenna device for an automobile, characterized in that a resonance point exists between −f _L ) · (0.6) and f _H. 5. The difference between the maximum reception sensitivity and the minimum reception sensitivity is about 1 within a desired reception frequency band or within a desired broadcast frequency band.
2. The circuit constants of the predetermined circuit and the reactance circuit are set so that the Q (quality factor) value is in the range of dB to about 16 dB.
2, 3 or 4 automotive glass antenna device. 6. The glass antenna device for an automobile according to claim 1, wherein the reactance circuit comprises a circuit in which a high frequency coil and a choke coil are connected in series. 7. A choke coil of a reactance circuit is connected in parallel with a resistor to adjust Q (quality factor).
Alternatively, the vehicle glass antenna device of item 6 .