JP2006135764A - Antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a planar antenna which is applicable to the window glass plate of a vehicle, has high reliability in a power feeding circuit, can be made thin, has excellent designing property and can obtain sufficient performance. <P>SOLUTION: This planar antenna is provided with the window glass plate 1 that is provided with a patch conductor 2 to be a radiation conductor and installed in a vehicle, a dielectric substrate 5 provided facing a face to which the patch conductor 2 of the window glass plate 2 is provided and separated at a predetermined interval by air or other dielectric, a ground conductor 4 provided on a face facing the window glass plate 1 of the dielectric substrate 5 and having a slot 7 corresponding to the position of the patch conductor 2, and a microstripline 6 provided to a face opposite to the ground conductor 4 of the dielectric substrate 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antenna device provided on a window glass plate of a vehicle such as an automobile.

  Today, an ETC (Electric Toll Collection System) that performs unattended toll collection on toll roads such as expressways is being implemented. In this system, wireless data communication is performed between an antenna installed at a gate of a toll gate and an in-vehicle device mounted on a vehicle such as an automobile, and a fee settlement process is performed. In this system, a planar antenna is often used as an onboard device antenna for convenience of installation and storage.

  In microwave communication, communication failure due to radio wave interference is likely to occur, so it is common to use circularly polarized waves that are unlikely to be affected by radio wave interference as communication radio waves. Excellent communication characteristics. Here, the microstrip antenna is a patch substrate (strip) having a rectangular shape, a circular shape, an elliptical shape or the like provided as a radiating conductor on a dielectric substrate provided with a ground conductor. An antenna having directivity in a direction substantially perpendicular to the surface of the dielectric substrate (see Non-Patent Document 1).

  The planar antenna for onboard equipment currently used is often used by being installed in a vehicle dashboard or the like, which is integrated with the onboard equipment main body or in a separate housing. For this reason, it is not preferable in terms of design due to restrictions on installation location.

  Therefore, when the structure is such that the microstrip antenna is installed on the window glass plate of the vehicle, the configuration of the feeding circuit becomes a problem. For example, when a patch conductor serving as a radiation conductor is provided on a window glass plate and power is supplied by a pin, the pin of the conductor is in direct contact with the glass plate on which the patch conductor is printed. In addition, there is a problem that it is difficult to reduce the thickness of the antenna due to the length of the pin itself.

  As a power supply circuit for a microstrip antenna, a configuration is disclosed in which a strip line that is electromagnetically coupled to a ground conductor provided with a slot is disposed (see Patent Documents 1 and 2). In addition, there is a configuration in which an H-shaped or cross-shaped slot is provided in the ground conductor to allow a part of the radio wave to pass therethrough so that power can be supplied between the radiation conductor and the transmission line in a non-contact manner (Non-Patent Document 2). 3).

However, none of such a microstrip antenna is mounted on a window glass plate of a vehicle. That is, a planar antenna that has high reliability, can be thinned, has good design characteristics, and has sufficient performance has not been realized.
JP-A-4-122105 Japanese Patent Laid-Open No. 5-55820 Haneishi, Hirasawa, Suzuki, “Small / Plane Antenna”, edited by the Institute of Electronics, Information and Communication Engineers, 1996 HS Shin and N. Kim, "Wideband and high-gain one-patch microstrip antenna coupled with H-shaped aperture", Electron.Lett., Vol.38, No.19, pp1072-1073, Sep. 2002 Y. Murakami, S. Sekine and H. Shoki, "Analysis of cross-slot-coupled circular microstrip antenna", Electron.Lett., Vol.38, No.25, pp1619-1621, Dec. 2002

  An object of the present invention is to provide an antenna device that can be applied to a window glass plate of a vehicle, has a highly reliable power supply circuit, and can be thinned.

  Another object of the present invention is to provide an antenna device capable of realizing a planar antenna with good design and sufficient performance.

  The present invention is provided with a patch conductor serving as a radiation conductor, a window glass plate installed in a vehicle, and a dielectric substrate or a dielectric sheet provided facing a surface of the window glass plate on which the patch conductor is provided. A dielectric layer disposed at a predetermined interval from the window glass plate by air or other dielectric material, and a surface of the dielectric layer facing the window glass plate A ground conductor having a slot at a position corresponding to the position of the patch conductor, and a feed line provided on a surface of the dielectric layer opposite to the surface on which the ground conductor is provided. An antenna device is provided.

  In addition, an antenna device is provided in which a slot provided in the ground conductor is formed in an H shape or a cross shape inclined obliquely with respect to the vertical direction of the patch conductor.

Further, when the distance from the peripheral edge of the window glass plate to the center of the patch conductor is E and the wavelength in the free space of the radio wave used for communication is λ ₀ , E / λ ₀ ≦ 2.51 and the patch Provided is an antenna device in which 0.2 ≦ D / λ _0, where D is the shortest distance between a conductor and a vehicle body opening edge on which the window glass plate is installed.

  According to the present invention, it is possible to provide an antenna device that can be applied to a window glass plate of a vehicle, has high reliability of a power feeding circuit, and can be thinned. In addition, it is possible to realize a planar antenna with good design and sufficient performance.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an exploded perspective view showing an overall configuration of an antenna device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the antenna device of FIG. 1 cut along an AA plane. The antenna device of this embodiment is a planar antenna provided in a window glass plate 1 attached to a vehicle such as an automobile, and includes a window glass plate 1, a patch conductor 2, a gap 3, a ground conductor 4, a dielectric substrate 5, and a microstrip. The line 6 is laminated. In this embodiment, the case where an antenna device is arrange | positioned at the surface (vehicle inside) of the one side of the window glass plate 1 is assumed.

  This antenna device is a planar antenna particularly suitable for microwave communication and millimeter wave communication, and is connected to a communication device that performs wireless communication between the vehicle and the outside of the vehicle. The radio communication system can be applied to ETC (Electric Toll Collection System, 5.8 GHz), SDARS (Satellite Digital Audio Radio System, 2.3 to 2.7 GHz), and the like.

  A patch conductor 2 is provided on one surface of the window glass plate 1 (an inner surface when attached to the vehicle), and a dielectric substrate 5 serving as a dielectric layer is provided facing the window glass plate 1. The gap 3 between the window glass plate 1 and the dielectric substrate 5 is filled with an air layer or another dielectric layer, and is separated at a predetermined interval. A ground conductor 4 having a slot 7 for electromagnetic coupling is provided on one surface of the dielectric substrate 5 facing the patch conductor 2. On the other surface of the dielectric substrate 5 opposite to the ground conductor 4, a power supply microstrip line 6 is provided.

  FIG. 3 is a plan view showing a detailed configuration of the patch conductor 2. The patch conductor 2 is a radiation conductor having a function of radiating a transmission radio wave or receiving an incoming radio wave. The patch conductor 2 is printed on one surface of the window glass plate 1 by baking a silver paste on the glass plate. Further, the patch conductor 2 has a shape having a notch portion 2a in which a pair of corner portions at the diagonal positions among the four corners of the square shape are notched in order to transmit and receive circularly polarized waves. ing. Here, the length of one side of the patch conductor 2 is a, and the length of the cut corner is b. There are two types of circularly polarized waves, right-handed and left-handed, and either right-handed circularly polarized light or left-handed circularly-polarized light depending on which one of the two diagonal lines in the square patch conductor is cut off. Is determined.

  Although the patch conductor 2 has a shape in which square corners are cut off in the example of FIG. 3, circularly polarized waves can be transmitted and received by making the corners projecting instead of cutting off the corners. is there. Further, the patch conductor 2 is not limited to a quadrangle, and may be circular. When the patch conductor is circular, the patch conductor is cut out at two opposing points on the circumference in order to correspond to circular polarization. Further, the patch conductor 2 is not limited to the shape for right-handed circular polarization shown in the figure, and in addition to right-handed circular polarization, A notch or protrusion can be provided on the circumference for left-handed circularly polarized waves, or a linearly polarized wave can be used without providing a notch or protrusion.

Further, the axial ratio of the antenna is determined by the length b by which the corner of the patch conductor 2 is cut off. The axial ratio indicates the degree of separation between right-handed circularly polarized waves and left-handed circularly polarized waves, and the lower the axial ratio, the less the interference between right-handed circularly polarized waves and left-handed circularly polarized waves. The operating frequency of the antenna is determined by the length a of one side of the patch conductor 2. The size of a typical patch antenna is k · (λ _0/2) length of one side. Here, k is a wavelength shortening rate due to a dielectric (relative permittivity ε _r ) between the radiation conductor and the ground conductor of the antenna, and is represented by k = (ε _r ) ^−1/2 . λ ₀ is a wavelength in free space of radio waves used for communication. However, in the configuration of the present embodiment, the length a of one side is further shorter than the above due to the wavelength shortening effect due to the patch conductor being printed on the glass plate.

  4 is a plan view showing a detailed configuration of the ground conductor 4 and the slot 7, FIG. 5 is a plan view showing a detailed configuration of the microstrip line 6, and FIG. 6 is a diagram showing a configuration example of the shape of the slot 7. On one surface of the dielectric substrate 5, a ground conductor 4 having a planar conductive pattern is formed over almost the entire surface. A coupling slot 7 formed by removing a part of the conductor is provided at substantially the center of the ground conductor 4. That is, the slot 7 is an elongated region where no conductor is provided on the dielectric substrate 5 between the ground conductor 4 and the edge of the microstrip line 6. The slot 7 is usually exposed by exposing the material of the dielectric substrate 5. On the other surface of the dielectric substrate 5, a microstrip line 6 having a single linear conductive pattern is formed from the vicinity of the center to one side of the periphery. In place of the dielectric substrate, a dielectric sheet made of rubber or the like may be used as the dielectric layer.

  The dielectric substrate 5 is disposed so that the ground conductor 4 faces the patch conductor 2. The slot 7 of the ground conductor 4 has a function of adjusting the electric field. By providing the slot 7, it is possible to electromagnetically couple the patch conductor 2 and the feeding microstrip line 6 through the slot 7 even when there is no conduction. Here, the size of one side of the outer shape of the slot 7 is c, the width of the notched gap is d, and the length of one side of the ground conductor 4 (dielectric substrate 5) is e. The shape of the slot 7 is not limited to the H shape as shown in FIG. 6A, but may be a cross shape (X shape) inclined obliquely as shown in FIG. 6B. By making the slot H-shaped, the size can be further reduced.

  Due to the electromagnetic coupling between the microstrip line 6 and the patch conductor 2, radio waves are propagated between the patch conductor 2 and the microstrip line 6, so that signals can be transmitted and received. That is, the radio wave received by the patch conductor 2 is propagated to the microstrip line 6 through the slot 7 of the ground conductor 4 and input as received power to a communication device (not shown) connected to the microstrip line 6. The In addition, transmission power output from a communication device (not shown) and supplied to the microstrip line 6 is propagated to the patch conductor 2 through the slot 7 of the ground conductor 4 and is radiated from the patch conductor 2 as a transmission radio wave. Here, the width of the microstrip line 6 is W, the length from the center of the ground conductor 4 to the periphery in the longitudinal direction of the microstrip line 6 is L, and the length from the center of the ground conductor 4 to the tip of the microstrip line 6 is Let Ls be the same.

  The width W of the microstrip line 6 is determined so that the characteristic impedance becomes 50Ω at the relative dielectric constant of the dielectric substrate 5 being used and the frequency used. Regarding the length of the microstrip line 6, the length Ls from the center of the ground conductor 4 to the tip of the microstrip line 6 has an important role in determining the impedance of the planar antenna. If this length Ls is long, the inductive property of the antenna impedance is large, and if it is short, the capacitive property is large. A connector or a cable (not shown) is attached to the base end portion (one side of the peripheral edge of the substrate) of the microstrip line 6 and connected to a communication device (transmitter or receiver).

  As described above, the antenna device according to the present embodiment uses the electromagnetic coupling method by the slot 7 formed in the ground conductor 4 in the glass antenna of the microstrip antenna in which the patch conductor is printed on the window glass plate of the vehicle. 2 and the microstrip line 6 are combined.

FIG. 7 is a diagram showing an arrangement configuration of the patch conductors 2 in the window glass plate 1. The window glass plate 1 is attached to a conductive vehicle body 8 such as metal. Here, the length in the width direction of the window glass plate 1 is g, and the length in the vertical direction is h. The position of the patch conductor 2 on the window glass plate 1 is preferably closer to the peripheral edge of the window glass plate 1 in consideration of the reception direction characteristics of the antenna. That is, when the distance from the peripheral edge 9 of the window glass plate 1 to the center of the patch conductor 2 is E, it is preferable that E is smaller. Specifically, E / λ ₀ ≦ 2.51 is preferable, and E / λ ₀ ≦ 1.55 is more preferable. However, if the patch conductor 2 is too close to the vehicle body 8 in contact with the peripheral edge of the window glass plate 1, the antenna gain is attenuated. Therefore, if the shortest distance between the patch conductor 2 and the vehicle body opening edge 10 is D, D needs a certain distance. Specifically, 0.2 ≦ D / λ ₀ is preferable. In the present invention, the vehicle body opening edge is the periphery of the opening of the vehicle body into which the window glass plate is fitted, and should be the vehicle body ground, and is made of, for example, a conductive material such as metal.

  A glass plate for an automobile windshield was used as the window glass plate 1 on which the patch conductor 2 was provided, and a planar antenna as shown in FIGS. 1 to 5 was designed. This planar antenna is a circularly polarized antenna that operates at a frequency of 5.8 GHz.

  As the window glass plate 1, a laminated glass plate was used in which an intermediate film was sandwiched between two glass plates. The dimensions of the window glass plate 1 are a length g in the width direction of 200 mm, a length h in the vertical direction of 200 mm, and a thickness of 4.5 mm. Here, a laminated glass plate having a thickness of 4.5 mm is a glass plate having a thickness of 2 mm (relative dielectric constant 7), an intermediate film having a thickness of 0.7 mm (relative dielectric constant 2.7), and a thickness of 1.8 mm. A glass plate (dielectric constant 7) is overlaid. When this laminated glass plate is considered as a bulk of a single plate, the relative permittivity of the window glass plate 1 is 6.2. Table 1 shows the dimensions and relative permittivity of each part of the planar antenna, and the unit of dimension is [mm].

  The patch conductor 2 is formed by printing and baking a silver paste on the window glass plate 1. In the gap 3 between the window glass plate 1 and the dielectric substrate 5, a double-sided tape for adhering the dielectric substrate to the glass plate is attached. In this example, an acrylic foam tape manufactured by 3M was used. The relative dielectric constant of the gap between the dielectric layers formed by this double-sided tape is 2.0. The patch conductor 2 may be formed by pasting a flexible substrate having a copper foil or a conductive layer on the window glass plate 1 instead of printing and baking a silver paste. The gap 3 may be provided with another dielectric material such as an adhesive instead of the double-sided tape. The dielectric substrate 5 is a glass epoxy substrate generally used for an electronic circuit substrate, and has a relative dielectric constant of 4.7. The grounding conductor 4 of the antenna is formed on one surface of the dielectric substrate 5, and the microstrip line 6 for feeding is formed on the other surface by copper foil.

  FIG. 8 shows the calculation result by the electromagnetic field simulator of the frequency characteristic of the reflection loss at 4 GHz to 7 GHz of the planar antenna of this embodiment. Further, FIG. 9 shows the measured frequency characteristic value of the reflection loss of the planar antenna of this embodiment, and FIG. 10 shows the measured value of the radiation direction characteristic (direction vs. radiated power) of the planar antenna of this embodiment. In FIG. 10, the upper solid line represents the power in the right-handed circularly polarized wave, and the lower broken line represents the power in the left-handed circularly polarized wave. From this measurement result, it can be confirmed that in the antenna front direction (angle 0 °), the right-handed circularly polarized wave and the left-handed circularly polarized wave are separated by about 15 dB in terms of power. In the radiation pattern of FIG. 10, the level decreases at ± about 60 ° from the antenna front direction. Regarding this reason, it is considered that the radio wave is reflected at the end of the measured glass plate of the sample, and the reflected wave affects the radiation pattern. In this example, since an experiment was performed using a small sample of a 200 mm square glass plate, this tendency changed when the evaluation was performed using an actual automotive windshield.

FIG. 11 to FIG. 14 show calculation results of antenna characteristics when the superposition of the patch conductor 2 provided on the window glass plate 1 and the dielectric substrate 5 is deviated during assembly, that is, the amount of deviation of the feeding position. . 11 to 14, the shift amount (patch shift amount) of the patch conductor 2 is normalized at a wavelength λ ₀ = 51.7 mm at 5.8 GHz.

  FIG. 11 is a diagram showing a change in antenna gain using the vertical shift of the patch conductor 2 with respect to the slot 7 as a parameter. FIG. 12 is a diagram showing changes in the axial ratio using the vertical displacement of the patch conductor 2 with respect to the slot 7 as a parameter. Here, the vertical direction represents the direction corresponding to the Y-axis direction, that is, the vertical direction of the H-type slot in the patch conductor 2 of FIG. 11 and 12, when the patch shift amount is negative, it means that the patch conductor 2 is shifted to the lower side of the Y axis in FIG. 3 when it is superimposed on the dielectric substrate 5. When the patch shift amount is positive, it means that the patch conductor 2 is shifted to the upper side of the Y axis in FIG.

When the patch shift amount in the Y-axis direction is Sy, from the result shown in FIG. 11, Sy / λ ₀ ≦ 0.020, that is, Sy ≦ 1.034 mm is preferable in order to improve the antenna gain. From the results shown in FIG. 12, it is preferable that the axial ratio is small, −0.023 ≦ Sy / λ ₀ ≦ 0.027, that is, −1.189 ≦ Sy ≦ 1.396 mm, in order to improve the axial ratio characteristics.

  FIG. 13 is a diagram showing a change in antenna gain using the lateral displacement of the patch conductor 2 with respect to the slot 7 as a parameter. FIG. 14 is a diagram showing changes in the axial ratio using the lateral displacement of the patch conductor 2 with respect to the slot 7 as a parameter. Here, the lateral direction represents the direction corresponding to the X-axis direction, that is, the lateral direction of the H-type slot in the patch conductor 2 of FIG. 13 and 14, when the patch shift amount is negative, it means that the patch conductor 2 is shifted to the left side of the X axis in FIG. When the patch shift amount is positive, it means that the patch conductor 2 is shifted to the right side of the X axis in FIG.

Assuming that the amount of patch shift in the X-axis direction is Sx, from the result of FIG. 13, in order to improve the antenna gain, −0.023 ≦ Sx / λ ₀ ≦ 0.028, that is, −1.189 ≦ Sx ≦ 1.448 mm is preferred. Further, from the result of FIG. 14, in order to improve the axial ratio characteristics, the small axial ratio is Sx / λ ₀ ≦ −0.016 or Sx / λ ₀ ≧ 0.024, that is, Sx ≦ −0.827 or Sx. ≧ 1.241 is preferable.

  15 and 16 show actual measurement results of the receiving direction characteristics of the antenna with respect to the position of the patch conductor 2 on the window glass plate 1. FIG. 15 is a diagram showing a change in the position of the patch conductor 2 provided on the window glass plate 1, and FIG. 16 is a diagram showing a reception direction characteristic (direction vs. received power) of the antenna at each position of the patch conductor 2 in FIG. is there. In the planar antenna of this embodiment, a ripple occurs in the vicinity of ± 40 to 60 ° from the antenna front direction in the radio wave radiation pattern (reception pattern). The experiment by the present inventors confirmed that the position of the ripple changes depending on the area of the window glass plate, and that the ripple is farther from the antenna front direction as the area of the window glass plate is larger. In addition, it was found that the magnitude of the ripple changes depending on the position of the patch conductor on the window glass plate, and the unevenness of the radiation pattern becomes smaller as the installation position of the patch conductor is closer to the peripheral edge of the window glass plate.

Here, the dimensions of the window glass plate 1 are the width direction length g = 460 mm, the vertical direction length h = 460 mm, and the center coordinates of the window glass plate 1 are (0, 0). And as shown in FIG. 15, the position of the patch conductor 2 is P1 (0, 0), P2 (0, 100), P3 (0, 200) from the center of the window glass plate 1 toward the top in the vertical direction. And moved. From the result of FIG. 16, it was confirmed that the ripple of the radiation pattern becomes smaller as it approaches the upper peripheral edge of the window glass plate 1, and the reception direction characteristic of the antenna is more preferably P3 closest to the peripheral edge. As shown in FIG. 7, when E is the distance from the peripheral edge 9 of the window glass plate 1 to the center of the patch conductor 2, E is preferably smaller. Specifically, when E / λ ₀ ≦ 2.51, that is, 5.8 GHz (λ ₀ = 51.7 mm), E ≦ 129.767 mm is preferable, and E / λ ₀ ≦ 1.55, that is, 5. In the case of 8 GHz, E ≦ 80.135 mm is more preferable. However, if the patch conductor 2 is too close to the vehicle body 8 in contact with the peripheral edge of the window glass plate 1, the antenna gain is attenuated. Therefore, if the shortest distance between the patch conductor 2 and the vehicle body opening edge 10 is D, 0.2 ≦ In the case of D / λ ₀ , that is, 5.8 GHz, D ≧ 10.34 mm is preferable.

  As described above, according to the present embodiment, the patch conductor is provided on the window glass plate, and the patch conductor is fed using the electromagnetic coupling method, so that the pin antenna can be compared with the pin feeding patch antenna. There is no problem of ensuring contact reliability, manufacturing is easy, workability is good, and thinning is possible. In addition, by making the slot provided in the ground conductor H-shaped, the length of the slot can be reduced. For this reason, even if the size of the patch conductor is small, the possibility that the slot protrudes from the patch conductor and the amount of radio wave coupling is reduced is reduced, and it is possible to reduce the size while ensuring the antenna performance. Therefore, according to the present embodiment, it is possible to provide an antenna device that can be applied to a window glass plate of a vehicle, has a high reliability of a power feeding circuit, and can be made thinner. In addition, it is possible to realize a planar antenna with good design and sufficient performance.

  In addition, this invention is not limited to an above-described Example, Various improvement and change are also included in this invention, unless the summary of this invention is impaired. In the above-described embodiment, it is described on the assumption that it is applied to one surface (inside the vehicle) of the windshield for automobiles. However, the surface on the inside of the windshield with the intermediate film sandwiched between the opposite surface (outside) But it is equally applicable.

The disassembled perspective view which shows the whole structure of the antenna device which concerns on embodiment of this invention. Sectional drawing at the time of cut | disconnecting the antenna apparatus of FIG. 1 in an AA plane. The top view which shows the detailed structure of a patch conductor. The top view which shows the detailed structure of a grounding conductor and a slot. The top view which shows the detailed structure of a microstrip line. The figure which shows the structural example of the shape of a slot. The figure which shows the arrangement configuration of the patch conductor in a window glass board. The figure which shows the calculation result of the frequency characteristic of the reflection loss in the planar antenna of the Example of this invention. The figure which shows the frequency characteristic actual value of the reflection loss in the planar antenna of the Example of this invention. The figure which shows the radiation direction characteristic actual value in the planar antenna of the Example of this invention. The figure which shows the change of the antenna gain characteristic by the vertical shift | offset | difference of the feed position in the planar antenna of the Example of this invention. The figure which shows the change of the axial ratio characteristic by the vertical shift | offset | difference of the feed position in the planar antenna of the Example of this invention. The figure which shows the change of the antenna gain characteristic by the horizontal shift | offset | difference of the feeding position in the planar antenna of the Example of this invention. The figure which shows the change of the axial ratio characteristic by the horizontal shift | offset | difference of the feeding position in the planar antenna of the Example of this invention. The figure which shows the change of the position of the patch conductor provided in the window glass board in the Example of this invention. The figure which shows the receiving direction characteristic of the antenna in each position of the patch conductor of FIG.

Explanation of symbols

1: window glass plate 2: patch conductor 3: gap 4: ground conductor 5: dielectric substrate 6: microstrip line 7: slot 8: vehicle body 9: peripheral edge portion 10 of window glass plate: vehicle body opening edge

Claims (3)

A patch conductor serving as a radiation conductor is provided, and a window glass plate installed in the vehicle;
A dielectric layer made of a dielectric substrate or a dielectric sheet provided to face a surface of the window glass plate on which the patch conductor is provided, and is predetermined by air or another dielectric with respect to the window glass plate Dielectric layers spaced apart, and
A ground conductor provided on a surface of the dielectric layer facing the window glass plate and having a slot at a position corresponding to the position of the patch conductor;
An antenna device comprising: a feed line provided on a surface of the dielectric layer opposite to a surface on which the ground conductor is provided.   The antenna device according to claim 1, wherein the slot provided in the ground conductor is formed in an H shape or a cross shape inclined obliquely with respect to a vertical direction of the patch conductor. When the distance from the peripheral edge of the window glass plate to the center of the patch conductor is E, and the wavelength in free space of radio waves used for communication is λ ₀ ,
E / λ ₀ ≦ 2.51;
When the shortest distance between the patch conductor and the vehicle body opening edge where the window glass plate is installed is D,
The antenna device according to claim 1, wherein 0.2 ≦ D / λ ₀ .

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