JPH08222930A - Glass antenna - Google Patents

Abstract

PURPOSE: To provide a glass antenna ensuring a high reception sensitivity over a broad frequency band on a glass plate provided with a defogger where only a limited space is provided. CONSTITUTION: The glass antenna is provided with defoggers 130, 140 and antenna elements 100, 120, 170, 180 on a glass plate in an extended way, and the antenna elements are parted such a way that the antenna elements 100, 120 are in capacitive coupling with each other but the antenna elements 170, 180 are not in capacitive coupling with the antenna element 100.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass antenna installed on a window glass of a vehicle or the like, and more particularly to a glass antenna provided in a defogger and having two antenna conductor elements capacitively coupled to each other.

[0002]

2. Description of the Related Art Generally, as a vehicle antenna, a pole antenna in which a body is provided with a pole (rod) protruding in an insulated state so as to supply power to the pole is widely known. The glass antenna has been put into practical use as an alternative antenna because it is prone to bending and damage, and has a problem that wind noise is generated during traveling.

This glass antenna is used, for example, in Shokai Sho 63.
As disclosed in Japanese Patent Laid-Open No. 92409/1992, an antenna wire is arranged in the vicinity of a side portion of a defogger provided on a windshield of a vehicle, and power is supplied to the antenna wire. However, in this conventional glass antenna, the antenna wire is placed close to the defogger to tune the reception performance of the antenna, and the method for improving the performance of the antenna is not qualitative and the tuning is unclear. There is a problem in that it is difficult to predict and the configuration of the antenna itself becomes complicated.

On the other hand, in addition to this, JP-A-62-131
As disclosed in Japanese Patent No. 606, a transparent conductive film is provided on a glass surface, an antenna body having a feeding point is arranged on the glass surface above the conductive film, and the antenna body and the transparent conductive film are capacitively coupled. There is proposed an antenna that can be used as an antenna. Also, US Pat. No. 5,029,
In No. 308, a first antenna conductor extending in the up-and-down direction is provided in the substantially center of the defogger area in the area where the defogger heat wire is stretched, and the heat wire intersecting with the first antenna conductor is electrically connected. Further, a second antenna conductor is provided on the upper part (or lower part) of the defogger so as to be connected to the uppermost (or lowermost) heat wire of the defogger. That is, the first antenna conductor and the second antenna conductor
The antenna conductor and the antenna conductor are used as one antenna. However, when the first and second antenna conductors are connected, the direct current flowing through the defogger is shunted to the first antenna conductor, and the effect of removing fog is reduced in the vicinity of the connection point. Therefore, in this US patent, a capacitor is provided between the first antenna conductor and the second antenna conductor so that the current flowing through the defogger is not shunted to the first antenna conductor.
The capacitance of this capacitor is selected to have a low impedance in the reception frequency band so that the first antenna conductor and the second antenna conductor function as one antenna.

Further, in Japanese Patent Laid-Open No. 55-60304, a first antenna conductor is provided vertically in the defogger region and a second antenna conductor is provided outside the defogger region.
Then, a first conductor wire connected to the first conductor and provided so as to be orthogonal to the first conductor (that is, parallel to the defogger heating wire) and the first conductor wire in parallel with the first conductor wire. The second conductor connected to the second antenna conductor is provided on the glass surface, and these first and second conductors are brought close to each other to capacitively couple.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Conventional examples of the above proposals (Japanese Utility Model Publication No. 63-92409 and Japanese Patent Application Laid-Open No. 62-131606)
No.), although the antenna body is capacitively coupled with the transparent conductive film, if a thin film is used in order to secure the transparency of the conductive film in order to ensure the transparency of the glass, the electric resistance value is extremely high. Inevitably, it becomes difficult for the received current to flow, and there is a possibility that good antenna performance cannot be expected in practice.

Further, in US Pat. No. 5,029,308, the defogger heat ray functions as an antenna because the provided capacitor is selected to have a low impedance in the frequency band of the received radio wave.
There is a drawback that the antenna performance is deteriorated.

Also, in Japanese Patent Laid-Open No. 55-60304, as in the above-mentioned US Pat. No. 5,029,308, since the shape of the antenna provided outside the defogger area is not taken into consideration, in other words, The antenna performance was deteriorated because no consideration was given to preventing the defogger heat rays from functioning as an antenna. As described above, the conventional glass antenna described above is not usually designed based on the concept of eliminating the influence of the defogger.

Therefore, in order to secure the receiving sensitivity, Japanese Patent Laid-Open No. 55-60304 has extended the length of the antenna wire in the vehicle width direction. However, even if it is said that the length of the antenna is increased in the vehicle width direction, since this antenna is arranged in the area where the defogger is not provided,
It will occupy that area. Further, since the antenna is arranged in the limited area, only one type of antenna can be set, and therefore, high receiving sensitivity cannot be ensured over a wide frequency band.

Further, in the conventional glass antenna, it is often impossible to provide the feeding point of the glass antenna at the end of the antenna pattern due to the requirement of the vehicle body structure. Therefore, for example, as disclosed in JP-A-2-42802. By providing a feeder line on the glass surface from the end of the antenna to the feeding position, the feeding point is secured and the receiving sensitivity is increased by adjusting the width of the feeder line. For this reason, the width of the feeder line needs to be widened depending on the case, and the backward visibility and the aesthetics are hindered by the feeder line.

The present invention has been made in view of the above circumstances, and an object thereof is to ensure high reception sensitivity over a wide frequency band in a glass provided with a defogger and capable of securing only a limited space. We propose a glass antenna that can be used. Another object of the present invention is to propose a glass antenna that can receive radio waves with little loss regardless of the position of the feeding point, regardless of the position.

[0012]

In order to achieve the above object, the defogger region of the present invention according to claim 1 in which a plurality of heat wires are extended as defoggers in the vehicle width direction and the heat wires are not extended. A glass antenna having a first antenna element that is provided on a glass having a blank area and is vertically connected on the glass while electrically directly connected to a heat wire of the defogger in the defogger area. A second antenna extending in the blank area and capacitively coupled with the first antenna element, and a third antenna extending in the blank area and having a negligible capacitive coupling with the first antenna element. And an antenna element.

By using the capacitively-coupled antenna element for receiving high frequency radio waves and the non-capacitively coupling antenna element for receiving low frequency radio waves, high receiving sensitivity can be secured in a wide frequency range. . According to a preferred aspect of the present invention, the third antenna element is provided at a position separated from the first antenna element by a negligible coupling capacitance. The effect of capacitive coupling can be eliminated simply by separating the positions, and the configuration is simplified.

According to a preferred aspect of the present invention, the blank area is set above the glass antenna. According to a preferred aspect of the present invention, the second antenna element and the third antenna element are provided above a glass antenna. The blank area can be effectively used. According to a preferred aspect of the present invention, the third antenna element has a substantially L shape or an inverted L shape. The effective length can be secured with a simple structure.

According to a preferred aspect of the present invention, the third
The distance between the antenna element and the latest heat wire of the defogger is 30 mm or more. According to a preferred aspect of the present invention, the second antenna element has two antenna conductors, one of the antenna conductors is set to receive FM radio waves, and the third antenna element is TV radio waves. It is set for reception.

According to a preferred aspect of the present invention, the second
The antenna element of 1 has two antenna conductors that are capacitively coupled to the first antenna element, and these two antenna conductors and the third antenna element constitute a space diversity antenna system. According to a preferred aspect of the present invention, of the two antenna conductors and the third antenna element, a separation distance between two antennas set to a relatively high frequency is set to a relatively low frequency. It is set to be shorter than the separated distance between the two antennas.

According to a preferred aspect of the present invention, the third
The antenna element of has two antenna conductors,
One antenna conductor and the second antenna element constitute a space diversity antenna system. According to a preferred aspect of the present invention, the two antenna conductors and the third antenna conductor are provided.
The antenna elements are distributed in the vehicle width direction of this glass antenna.

According to a preferred aspect of the present invention, of the two antenna conductors and the second antenna element, the distance between the two antennas set to a relatively high frequency is relatively low. It is set shorter than the distance between the two antennas set to the frequency. Another object of the present invention is, in a glass antenna in which an antenna pattern is arranged on a wind panel, a feeder line connecting an end of the antenna pattern and a feeding position is extended on this panel, and the feeder line is The length 1 can be achieved by a glass antenna set to 1≈α · λ / 2, where α is the glass shortening rate and λ is the wavelength of the reception frequency.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. <Antenna System of Embodiment> FIG. 1 illustrates a glass antenna for an automobile to which the present invention is applied, as viewed from the inside of the automobile. This glass antenna includes a plurality of defogger heating wires 131t, 1 extending in the region 130 on the glass 300 and extending substantially parallel to each other in the vehicle width direction.
, 131b are provided, and a plurality of defogger heating wires 141t, 141, ..., 141m, 141 extending substantially parallel to each other in the vehicle width direction are provided in a region 140 below the region 130.
b is provided.

In the region 130, the defogger heating wire 1
The antenna conductor element 100 that intersects with and is electrically connected to the heat wires 31t, 131, ..., 131b at approximately the center in the vehicle width direction is provided, and in the area 140, the defogger heat wires 141t, 141, ..., 141m ( An antenna conductor element 150 that intersects with these heating wires and is electrically connected is provided at approximately the center in the vehicle width direction (which does not intersect with 141b for the reason described later). Glass window 30
There is a region where the defogger heat ray is not provided in the upper part of 0, and four antennas (110, 170, 180, 120 in order from the left in FIG. 1) are arranged in this region. The antennas 110 and 120 are eye-shaped,
The antenna 170 has an L shape, and the antenna 180 has an inverted L shape.

The signal received by the L-shaped antenna 170 is transmitted to the feeding point 173 via the feeder line 171, and input to a tuner (not shown) or the like. Inverted L-shaped antenna 1
The signal received by 80 is transmitted to the feeding point 184 via the feeder line 183 and input to a tuner (not shown) or the like.
The monopole antenna conductor element 100 has a heating wire 131b.
The antenna conductor element 150 of the monopole type is electrically connected to the heating wire 141t. Therefore, the antenna conductor element 100 and the antenna conductor element 150 are capacitively coupled via the heat wires 131b and 141t. Thus, the antenna conductor element 100 and the antenna conductor element 150 form a “first antenna”. Eye-shaped antenna 110 and uppermost defogger heat wire 131
The distance to t is a short d ₁ and therefore the antenna 110
Is the antenna conductor element 1 through the defogger heat wire 131t.
00 and capacitive coupling. The distance between the eye-shaped antenna 120 and the uppermost defogger heating wire 131t is a short d ₂ .
Therefore, the antenna 120 is also capacitively coupled to the antenna conductor element 100 via the defogger heat wire 131t. Therefore,
Each of the antennas 110 and 120 constitutes a "second antenna".

The distance between the L-shaped antenna 170 and the uppermost defogger heating wire 131t is long d ₃ , and therefore the antenna 170 does not capacitively couple with the antenna conductor element 100 via the defogger heating wire 131t. Similarly,
The inverted L-shaped antenna 180 and the uppermost defogger heat wire 13
The distance from 1t is long d ₄ , and therefore the antenna 18
0 does not capacitively couple with the antenna conductor element 100 via the defogger heat wire 131t. Thus, antennas 170 and 180 both function as "third antennas", respectively.

The features of the antenna system shown in FIG. 1 are: a first antenna (antenna conductor element 100 and antenna conductor element 150) and a second antenna (antenna 12).
0) and the third antenna (antenna 170
Alternatively, the antenna 180) is arranged at such a distance that the capacitive coupling with the first antenna can be ignored, so that high receiving sensitivity can be secured in a wide frequency band, and the lengths of the feeder lines 172 and 183 are appropriately set. By doing so, the loss due to the feeder line can be reduced without being restricted by the position of the feeding point and the line width of the feeder line.

<Capacitive Coupling Setting> In the antenna system of FIG. 1, the first antenna (100, 150) is the second antenna.
Of the first antenna (1) by capacitively coupling with the antennas (110, 120) of
The reason why 00, 150) and the second antenna (110, 120) function as a highly sensitive monopole antenna will be described with reference to FIGS. 2 to 9.

The method of determining the capacity is disclosed by the applicant of the present invention in Japanese Patent Application No. 6-271005. 2 to 11 are provided to simplify the explanation of the principle of capacitive coupling. FIG. 2 shows a rear part of a vehicle to which a glass antenna is applied in the present specification, and 1 is a vehicle body, and a rear window 2 is opened in the rear part of the body 1, and the rear window 2 is formed in the rear window 2. Rear window glass 3
(Hereinafter, simply referred to as window glass) is fitted in a substantially airtight manner.

As shown in FIG. 3, on the rear window glass 3 of the automobile, the heat rays of the defogger 5 are generated.
Is separated from the upper end portion (the body 1 on the upper side of the window 2) by a predetermined size, and further, the central portion in the left-right direction is arranged and attached so as to substantially coincide with the left-right central portion of the window glass 3. ing. The defogger 5 has a U-shape having upper and lower step portions 5a and 5b, and divides a plurality of heater wires 6, 6 ... .. and the lower heater wires 6, 6, ... Connect the ends of each one side (right side) with independent bus bars 7, 8, and the other side of the entire heater wires 6, 6 ,. The ends on the left side are connected by a common bus bar 9.

Although not shown, the upper independent bus bar 7 is grounded to the body 1 to be the ground side of the defogger 5. Further, the lower independent bus bar 8 is connected to the + power source of the on-vehicle battery via a switch (not shown), and when the switch is turned on, power is supplied from the battery to each heater wire 6 of the defogger 5 to generate heat. The heat generated removes the fog on the surface of the window glass 3.

The defogger has a great influence on the performance of the glass antenna. In particular, the DC current flowing through the defogger has many noise components, and it is preferable that this noise does not enter the antenna. Furthermore, the defogger heat rays function as an antenna conductor element, making it difficult to design a glass antenna with the desired performance. Capacitively coupled antennas, in order to dramatically improve the performance than conventional glass antennas, the inventors of the present invention cut the noise component from the defogger, and further prevent the defogger heat rays from functioning as an antenna element. It has been proposed as Japanese Patent Application No. 6-205767. By describing the design method of the glass antenna proposed in this Japanese Patent Application No. 6-205767 and the structure of the glass antenna constructed by the design method, it is possible to prevent the heat rays of the defogger from affecting the operation of the antenna. Explain why you can.

FIG. 4 shows that the conductor 41 is arranged so as to intersect the heat wire 6 in the region where the heat wire of the defogger is arranged. A conductor 42 is arranged in parallel with the uppermost heating wire 6, and a conductor 40 is arranged orthogonal to the conductor 42.
It is assumed that the length of the conductor 40 from the feeding point is L and the length of the defogger heating wire (the uppermost heating wire 6a) is 2Y. To see the relationship between the conductor 40 and the heating wire 6, consider an equivalent circuit diagram as shown in FIG. In FIG. 5, the capacitor 43 is a conductor 42 and a heating wire 6a.
Is the coupling capacity due to. The antenna shortening rate on the glass surface by the capacitor 43 is represented by α. Now, the coupling capacitance C =
When 11 pF (84 MHz), L = 12 cm, and Y = 28 cm, the antenna shown in FIG. 5 is equivalent to the antenna shown in FIG. 6 due to the shortening effect of the capacitor 43. In this example, the length of the antenna conductor after the capacitor 43 is 28 cm.
To 22 cm, the capacitor shortening rate α is α = 22/28. When the relationship between the shortening rate α and the coupling capacity is experimentally obtained, the results are as shown in FIGS. 7 and 8. According to the graphs of FIGS. 7 and 8, the shortening rate α increases as the coupling capacitance C increases. However, the shortening rate α is as follows when the coupling capacitance C exceeds 40 pF.
Even if C increases, it does not exceed 1. This gives a coupling capacity of 4
It shows that increasing beyond 0 pF is meaningless.

In order that the heating wire 6 having a length of 2Y does not greatly affect the antenna, the impedance of the heating wire may be extremely large. As a result of experiments conducted by the inventors, in order for the impedance of the heat wire 6 to become extremely large, the length of the conductor (a part of the antenna) should be set so as to satisfy the relationship of β · λ / 4 = L + α · Y (1). It was found that the relationship between the length L, the length Y of the heating wire (the highest heating wire), and the shortening rate α due to capacitive coupling should be set. Where λ is the wavelength of the radio wave to be received,
β is the antenna shortening rate due to glass, and is generally known to be approximately 0.6 for glass for automobiles.

When the equation (1) is modified, α = (βλ / 4-L) 1 / Y (2) Consider the case where the vehicle is different by using the equation (2). If L becomes longer depending on the vehicle, (2)
Since it can be seen from the equation that α becomes small, the coupling capacitance C is lowered according to the graph of FIG. 7 in order to reduce the influence of the defogger. On the other hand, in a vehicle in which the length of Y is short, it can be seen from Equation (2) that α becomes large, so the capacity C is set large.

The setting determined by such a method so that the defogger has almost no influence on the antenna characteristics is 70 cm ≦ λ / 4 ≦ 100 cm for the wavelength in the FM frequency range, and the glass shortening is performed in the vehicle. Multiplying by the ratio (β = 0.6), 42 cm ≦ β · λ / 4 ≦ 60 cm, that is, 42 cm ≦ L + α · Y ≦ 60 cm.

The above equation (1) holds true on the assumption that the bus bar end of the defogger is short-circuited to the body of the vehicle. In an actual vehicle,
Since it can be considered that the bus bar and the body are connected by a certain amount of capacitive coupling, the preferable range of L + α · Y for FM radio is 20 cm ≦ L + α · Y ≦ 70 cm. It was experimentally obtained that (3). Also, for an antenna particularly suitable for use in North America where the frequency band of the FM radio is 88MHz to 108MHz, 40cm≤L + α ・ Y≤50cm, while the frequency band of the FM radio wave in Japan is 76cm.
For MHz to 90 MHz, a glass antenna set to 50 cm ≦ L + α · Y ≦ 60 cm exhibits particularly preferable performance.

Further, in practice, since radio waves in a frequency band having a spread such as radio waves for FM radio are received, in order to secure the receiving performance over the entire area, L + α · Y is an abbreviation of the frequency band to be received. Of course, it is preferable to set the length according to the frequency of the central portion. In the antenna of FIG. 3, the antenna in which the first conductor 40 portion is changed to the loop 45 is shown in FIGS. 9 and 10. A characteristic of the loop conductor is that it has a width W in the vehicle width direction, and by using such a loop conductor, the coupling capacitance can be easily set by changing W. FIG. 11 shows how the coupling capacitance changes when the width W of the loop conductor 45 is changed and when the distance d between the loop conductor 45 and the defogger heating wire 6 is changed.

The glass antenna having the shape as shown in FIG. 9 is one which can obtain a sufficient antenna performance, and is more maintainable and has a better wind noise than the conventional rear pole antenna (90 cm rod antenna). Since it is overwhelmingly superior, its practical value is particularly great.

Next, as shown in FIG. 10, the loop conductor 45
(W = 20 cm) is placed at the bottom of the defogger, and the antenna 45 is fed at the center of the defogger.
High performance can be obtained. According to the findings of the inventors (for example, Japanese Patent Application No. 6-205767), when the monopole antenna is mounted on a vehicle as a glass antenna, the length of the monopole antenna is L _x , 20 cm ≦ A high-performance antenna can be obtained within the range of L _x ≦ 70 cm (4). Further, the above-mentioned antenna system can be applied to the VHF band of the TV if it is set so as to satisfy the expression (1) as described above.

Wavelength in the VHF band of TV (92 MHz to 22
At 2MHz), the setting that the defogger has almost no effect on the antenna characteristics is 34cm ≦ λ / 4 ≦ 82cm, and in the vehicle-mounted state, it is multiplied by the glass shortening rate (β = 0.6), and 20cm ≦ β ・λ / 4 ≦ 50 cm, that is, 20 cm ≦ L + α · Y ≦ 50 cm (5).

As described above, the equation (1) holds when the ideal state in which the end of the defogger bus bar is short-circuited to the body of the vehicle is considered. Can be regarded as being connected by a certain amount of capacitive coupling, so the VH of the above TV
As a preferable range of L + α · Y for the F band, it has a slightly wider range than the ideal state similarly to the antenna for the FM frequency, and is 10 cm or more and 60 cm or less. Furthermore, in order to practically secure the reception performance over the entire VHF band, it is needless to say that L + α · Y should have a length that matches the frequency in the substantially central portion of the VHF band.

<Broadband Reception Frequency> The above is the principle of operation of the capacitively coupled antenna which the inventors of the present invention have clarified in the prior application. The antenna system of the embodiment shown in FIG. 1 is a further development of the principle of this capacitively coupled antenna, and is a combination of two capacitively coupled antenna systems (antenna conductor element 100, antenna 110 and antenna 120). Furthermore, by combining two antenna systems (L-shaped antenna 170 and inverted L-shaped antenna 180) that are not capacitively coupled,
This is aimed at the effect of the above. The antenna system in the above-mentioned prior application by the applicant of the present invention aims at forming a monopole antenna, and such a monopole antenna antenna is unlikely to cause a problem of space in the vehicle width direction. In other words, the object of the present invention to realize a broadband antenna system on a window glass having a limited space is completed only after the theoretical analysis in the above-mentioned prior application.

Now, returning to the description of the antenna system of FIG. 1, this antenna system will be described in detail. The current to the defogger flows from the terminal 134, passes through the heating wires 131t, 131, ...
1, ..., 141 m, 141 b, and returns to the terminal 145 via the line 146.

The antenna 110 functions as a main antenna for FM, and the antenna 120 functions as an antenna covering a low frequency band for TV. That is, the antenna 1
The FM radio wave signal received by 10 is output from the coaxial cable 114 to a tuner or the like (not shown) via the line 113. Further, the AM radio wave signal received by the antenna 110 is output from a terminal 134 to a tuner (not shown) or the like via the line 112. The low-frequency band radio signal for TV received by the antenna 120 is output to a tuner (not shown) or the like via the coaxial cable 123.

The antenna conductor element 150 is provided in the region 140 in which the defogger current flows. As described above, the antenna conductor element 100 includes the antenna conductor element 150.
Since it is capacitively coupled to the defogger based on the relationship of the above formula (1), the wavelength (center) λ of the radio wave to be received and the length Y of the defogger arranged on the glass are optimal and are not easily affected by the defogger Antenna 110 (or antenna 120)
The combination of the height L and the coupling capacity C (related to the shortening rate α) is determined. The width W of the antenna and the distance d from the heating wire 131t are determined based on the value of the coupling capacitance C. The height of the antenna 110 is L ₁ , the height of the antenna 120 is L ₂ , the distance between the antenna 110 and the heat ray is d ₁ , and the antenna 1 is
When the distance between the heat wire and 20 is d ₂ , the length of the conductor 100 is X 1, the length of the conductor 150 is X _2, and the distance between the defogger 130 and the defogger 140 is d ₅ , the antenna 11
For 0, 20 cm ≦ L ₁ + α ₁ · (X ₁ + α ₂ · X ₂ ) ≦ 70 cm (6) For the antenna 120, if 20 cm ≦ L ₂ + α ₁ ′ · (X ₁ + α ₂ · X ₂ ) ≦ 70 cm holds (7), a glass antenna with good performance is provided as a preferable antenna length. It However, α ₁ is antenna 1
10 is the shortening rate of the defogger 130, α ₁ ′ is the shortening rate of the antenna 120 by the defogger 130, and α ₂ is the defogger 130 and 140 of the conductor 150.
This is the shortening rate due to capacitive coupling with.

The conductor 172 extending in the vehicle width direction of the L-shaped antenna 170 is set to have a distance d3 with respect to the uppermost heating wire 131t. The length of the conductor 171 extending in the vertical direction of the antenna 170 is L _1Y, and the conductor 17 extending in the vehicle width direction.
When the length of 2 is L _1X , the L _1X and L _1Y are such that the antenna 170 functions as a whole (as an antenna of length L _1X + L _1Y ), that is, the wavelength of the received radio wave of the antenna 170 is λ. When _{1, L 1X + L 1Y =} α · λ 1/4: is appropriately set so as to satisfy (alpha glass shortening coefficient) ... (8). Similarly, reverse L
The conductor 182 of the character-shaped antenna 180 extending in the vehicle width direction is set to have a distance d4 with respect to the uppermost heating wire 131t. The length of the conductor 181 extending in the vertical direction of the antenna 180 is L _2Y, and the length of the conductor 182 extending in the vehicle width direction is L _2X.
Then, the L _2X and L _2Y are such that the antenna 180 functions as a whole (as an antenna of length L _2X + L _2Y ), that is, the wavelength of the radio wave received by the antenna 180 is λ _{2
When, L 2X + L 2Y = α} · λ 2/4: is appropriately set so as to satisfy (alpha glass shortening coefficient) ... (9). Here, L _1X + L _1Y > L _2X + L _2Y (10), that is, the element length of the antenna 170 is the antenna 18
Longer than zero. This is because the antenna 180 receives the TV in the intermediate frequency band of the TV wavelength band, and the antenna 180 receives the TV
This is because it is set to receive the high frequency band of the wavelength band. Thus, the antennas 120, 170, 180 are T
A high reception performance is ensured over a wide frequency band of V radio waves (L channel radio waves, M channel radio waves, and H channel radio waves), and a frequency diversity system can be formed as shown in FIG.

Here, the distance d ₃ between the conductors 172 and 182 of the antennas 170 and 180 in the vehicle width direction and the heating wire 131t,
Reference is made to d ₄ . The conductor 182 extending in the vehicle width direction is set with a distance d4 with respect to the uppermost heating wire 131t. As described above, the antenna 170 has L _1X and L _1Y
Is set so that the antenna 170 as a whole receives TV radio waves in the low frequency band, and the antenna 180 uses L _2X and L _2Y.
Is set so that the antenna 180 as a whole receives TV radio waves in a high frequency band. Therefore, when the antenna 170 or the antenna 180 is capacitively coupled to the antenna conductor element 100 via the heat wire 131t, the antenna effective length becomes rather long and it becomes impossible to receive a high frequency band.
Therefore, it is desirable to set the distances d ₃ and d _{4 to} such a distance that the capacitive coupling with the antenna conductor element 180 can be ignored. In the example of FIG. 1, L _1X = 150 mm, L _2Y = 102 m
m, the distance between the conductors 172 and 182 in the vehicle width direction is 50 m
If the line width of the antennas 170 and 180 is 1 mm, and d ₃ = d ₄ = 40 mm (11), capacitive coupling can be ignored. Of course,
The lengths of the distances d ₃ and d ₄ can be 40 mm or more or less (for example, 30 mm) depending on the allowance in the height direction of the window.

<Space Diversity> The antenna 120 and the antennas 170 and 180 form a frequency diversity system as described above. However, if the positions of these antennas in the vehicle width direction are appropriately set, they also function as a space diversity system. . In the embodiment shown in FIG.
Two frequency bands are set. Then, the intermediate frequency band of TV radio waves is received by the antenna 170. Therefore, in order to achieve good spatial diversity, the antenna 1 that receives TV _M radio waves that is in the middle of the three frequency bands is used.
Other antennas (antenna 12
0 and the position of the antenna 180) are set. In order to achieve good spatial diversity with two antennas, the distance between the two antennas should be set short for radio waves of higher frequency, and set to be long for radio waves of lower frequency. Is preferred.
Therefore, when the diversity system is to be constructed in three frequency bands of low, middle and high as in the embodiment of FIG. 1, the antenna 120 and the antenna which compose the diversity system in the relatively low frequency band The separation distance of 180 shortens the separation distance between the antenna 170 and the antenna 180 forming the diversity system for relatively high frequencies. That is, if antenna 120 (low) → antenna 170 (middle) → antenna 180 (high), (distance between antenna 120 and antenna 170)> (distance between antenna 170 and antenna 180) (12) Set to.

If the five antennas A, B, C, D, E
Therefore, if the reception frequency band is low, A <B <C <D <E (13), the positions of the antennas are ACEDB in order. In order to form the space diversity between the antennas A and B which receive the charged wave of the lowest frequency, it is necessary to make the distance between A and B the longest. Therefore, these two antennas are the outermost in the vehicle width direction of the windshield. This is because it must be placed in Regarding the antennas B and C that receive the next low-frequency charged wave, it is necessary to shorten the distance between B and C and the distance between A and B, that is, it is necessary to place the antenna C between the antennas A and B. , B-C distance, it is necessary to position the antenna C on the A side instead of the antenna B side. Similarly, for the antennas C and D that receive the next lower frequency charged wave, the antenna D needs to be placed between the antennas B and C, but the position of the antenna D must be changed in order to increase the distance between C and D. B, not antenna C
Need to take to the side. Further, the antenna E is the antenna C-
Place between D.

Such a space diversity system can be realized by, as shown in the embodiment of FIG. 1, a frequency diversity antenna system in a limited empty space of a glass surface where the defogger is not extended. This is because the antennas that are capacitively coupled and the plurality of antennas that are not capacitively coupled are scattered on the glass surface according to the reception frequency band so as to be configured. That is, spatial diversity can be achieved by appropriately setting the spatial arrangement of the plurality of antennas.

<Opening from the restriction on the position of the feeding point> The intermediate frequency band of TV radio waves is received by the antenna 170, and the high frequency band is received by the antenna 180. The received signals are fed to terminals 17 via feeder lines 172 and 183, respectively.
Appears in 3,184. That is, the feeding points of the antenna 170 and the antenna 180 are set to 173 and 184, respectively. When a high frequency signal flows through the feeder line, the signal loss of the signal due to the feeder line changes depending on the line width of the feeder line, and it is necessary to change the line width according to the frequency. As a matter of course, in the glass antenna, since the line width of the feeder line is limited, when the adjustment cannot be performed by changing the line width, conventionally, the position of the feeding point is moved.

In the embodiment shown in FIG. 1, a feeder line 172, 183 having a width of 3 mm is used as a feeder line having a thickness that can secure a sufficient amount of current for practical use and has no problem even if it is arranged on glass. Adopted in. On top of that, the inventors
It has been found that the transmission loss can be minimized regardless of the line width of the feeder line by setting the total length l of the L-shaped antenna to l≈2L with respect to the total length L of the feeder line. In the system of FIG. 1, the length of the feeder line 172 is l ₁ , the feeder line 18 is
If the length of 3 is l ₂ , then l ₁ = 2 × (L _1X + L _1Y ) ... (15) l ₂ = 2 × (L _2X + L _2Y ) ... (16) As is clear from the equations (8) and (9), 2l ₁ = α × λ ₁ (17) 2l ₂ = α × λ ₂ (18) holds. By doing so, the antenna position can be determined without being restricted by the line width of the feeder line and the position of the feeding point.

<Effects of Embodiment> According to the embodiment of FIG. 1 described above: The capacitive coupling between the antenna conductor element 100 and the antenna 120 minimizes the influence of the defogger, and The presence of the antenna conductor element 100 exerts the effect of lowering the optimum reception frequency band of the antenna 120. Further, since the antenna 170 and the antenna 180 are set at a distance such that capacitive coupling with the antenna conductor element 100 can be ignored, the antenna conductor element 100 has an effect of lowering the optimum reception frequency band of the antenna 170 and the antenna 180. Since the antenna 170 and the antenna 180 have a high reception frequency band originally set, the optimum reception frequency band of the antenna 170 and the antenna 180 becomes the optimum reception frequency band. That is, a frequency diversity antenna system is achieved in which the antenna system of the antenna conductor element 100 and the antenna 120, which are capacitively coupled, is responsible for the low band, and the antenna 170 or the antenna 180 is responsible for the high band.

Furthermore, two antennas 17 which are not capacitively coupled
By changing the respective lengths of 0 and 180 as shown in equations (8) and (9), the former can be set for the intermediate frequency band and the latter for the high frequency band. The antenna system of 100 and the antenna 120, the antenna 170, and the antenna 180 can realize a frequency diversity system in three regions of a low frequency band, an intermediate frequency band, and a high frequency band, respectively. : The length of the feeder lines 172 and 183 is calculated by the formula (1
5), (16) or equations (17), (18), it is possible to reduce the loss due to the feeder line without being restricted by the position of the feeding point and the line width of the feeder line, and thus the receiving sensitivity. Can be improved. : Antennas set to realize frequency diversity (antenna 120, antenna 170, antenna 1
When determining the position of (80), the closer the antenna group (antenna 170 and antenna 120) that covers a relatively lower frequency band, the greater the distance between the antenna groups and the antenna group (Antenna group that covers a relatively higher frequency band). An ideal space diversity antenna system can be realized by making the distance larger than the distance between the antennas of the group of antennas 170 and 180).

<Further Modifications> The present invention can be further modified without departing from the spirit thereof. The glass antennas of the various embodiments described above are supposed to be applied to the VHF band of FM radios and TVs as an assumed usage state, but other communication devices using these frequency bands (for example, a keyless entry system). Of course, it is also applicable to.

Further, in the above-mentioned various embodiments, the capacitive coupling between the antenna conductor elements is obtained by arranging them on the glass surface so as to be separated from each other. However, a chip capacitor is provided between the antenna conductor elements. It may be configured to obtain capacitive coupling. Furthermore, if this chip capacitor is a variable capacitor whose capacitance can be changed, the coupling capacitance between the antenna conductor elements can be adjusted even after the glass is attached to the vehicle body, which is necessary due to matching with the reception frequency and individual differences in the vehicle body. Fine adjustment of the optimum antenna length is possible even after the car body is off line from the production line, and the effect is great.

Further, the setting area of the defogger is not limited to the upper portion, and the same effect can be obtained even if it is set to the lower portion.
Further, the number of antenna elements is not limited to four. Furthermore,
The shape of the L-shaped antenna is not limited to the shape shown in FIG. For example, it may be as shown in FIG. 13 or FIG. In short, it is sufficient that the antenna conductor element 100 has an effective length capable of receiving the reception frequency without being capacitively coupled with the antenna conductor element 100.

[0055]

As described above, according to the glass antenna of the present invention, it is possible to secure a high receiving sensitivity over a wide frequency band in a glass in which a defogger is provided and a limited space can be secured. Further, it is possible to provide a glass antenna that can transmit a received radio wave with little loss regardless of where the position of the feeding point is provided, without being affected by the position.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a glass antenna according to a preferred embodiment of the present invention.

FIG. 2 is a plan view of a rear window of a vehicle to which the embodiment is applied, viewed from a direction orthogonal to a windshield surface.

FIG. 3 is a diagram showing in principle the configuration of an antenna for explaining the principle by which the influence of defogger is minimized.

FIG. 4 is a diagram modeling an antenna configuration for explaining the principle that the influence of defogger is minimized.

FIG. 5 is a diagram modeling an antenna configuration for explaining the principle of minimizing the influence of defogger.

FIG. 6 is a diagram modeling an antenna configuration for explaining the principle that the influence of defogger is minimized.

FIG. 7 is a diagram showing a relationship between a shortening rate α and a coupling capacity C.

FIG. 8 is a diagram exemplifying a relationship between a shortening rate α and a coupling capacity C.

FIG. 9 is a diagram showing a glass antenna configured according to the principle shown in FIGS.

FIG. 10 is a diagram showing the configuration of another example of the glass antenna configured according to the principle shown in FIGS.

FIG. 11 is a diagram for explaining the relationship between the coupling capacitance C and the distance d in the example.

12 is a diagram showing frequency sharing of the antenna system of FIG. .

FIG. 13 is a diagram showing a configuration of a modified example of the present invention.

FIG. 14 is a diagram showing a configuration of a modified example of the present invention.

Claims (16)

[Claims] 1. A defogger region having a plurality of heat rays extending in the vehicle width direction as a defogger and a blank region having no heat ray extending, the heat ray of the defogger being electrically connected to the defogger region in the defogger region. A glass antenna having a first antenna element extending vertically on the glass while being directly connected to the second antenna, the second antenna extending in the blank area and capacitively coupled to the first antenna element. And a third antenna element extending in the blank area and having a negligible capacitive coupling with the first antenna element. 2. The third antenna element is provided at a position separated from the first antenna element so that the coupling capacitance with the first antenna element is negligible.
The glass antenna described in. 3. The glass antenna according to claim 1, wherein the blank area is set above the glass antenna. 4. The glass antenna according to claim 3, wherein the second antenna element and the third antenna element are provided above a glass antenna. 5. The first antenna element according to claim 1, wherein the third antenna element is substantially L-shaped or inverted L-shaped.
5. The glass antenna according to any one of 4 to 4. 6. The glass antenna according to claim 1, wherein a distance between the third antenna element and a recent heat ray of the defogger is 30 mm or more. 7. The second antenna element has two antenna conductors, and one of the antenna conductors is FM.
The glass antenna according to any one of claims 1 to 6, wherein the glass antenna is set to receive radio waves and the third antenna element is set to receive TV radio waves. 8. The second antenna element has two antenna conductors that are capacitively coupled to the first antenna element,
9. The glass antenna according to claim 1, wherein the two antenna conductors and the third antenna element constitute a space diversity antenna system. 9. The glass antenna according to claim 8, wherein the two antenna conductors and the third antenna element are dispersed in the vehicle width direction of the glass antenna. 10. The separation distance between the two antenna conductors and the third antenna element, which are set to a relatively high frequency, of the two antenna conductors and the third antenna element, The glass antenna according to claim 9, wherein the glass antenna is set shorter than the distance. 11. The third antenna element has two antenna conductors, the two antenna conductors and the second antenna conductor.
The glass antenna according to any one of claims 1 to 9, wherein a spatial diversity antenna system is configured with the antenna element of (1). 12. The glass antenna according to claim 8, wherein the two antenna conductors and the third antenna element are dispersed in the vehicle width direction of the glass antenna. 13. The distance between the two antenna conductors and the second antenna element, which are set to a relatively high frequency, of the two antenna conductors and the second antenna element, The glass antenna according to claim 9, wherein the glass antenna is set shorter than the distance. 14. The total length L of the third antenna element is
The glass antenna according to claim 5, wherein the glass shortening rate is α and the wavelength of the reception frequency is λ, and L≈α · λ / 4 is set. 15. A feeder line connecting the end of the third antenna element and a feeding position is extended on the glass antenna, and the length of the feeder line is 1, the glass shortening rate is α, and the reception frequency is 15. The glass antenna according to any one of claims 1 to 14, wherein l≈α · λ / 2 is set, where λ is the wavelength of. 16. A glass antenna having an antenna pattern arranged on a wind panel, wherein a feeder line connecting an end of the antenna pattern and a feeding position is extended on the panel, and a length l of the feeder line is set. , And the glass shortening rate is α and the wavelength of the reception frequency is λ, the glass antenna is set to 1 ≈ α · λ / 2.