JP2008160282A - On-vehicle glass antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple on-vehicle glass antenna whose sensitivity is high in a horizontal direction when attached to a vehicle. <P>SOLUTION: The on-vehicle glass antenna 3 is formed on the surface of window glass for the vehicle. The on-vehicle glass antenna 3 comprises: a patch part 8 composed of a conductor; a grounding conductor 7 composed of a conductor formed on the same surface as the patch part 8 so as to surround the patch part 8; short-circuit lines 5a and 5b composed of a conductor connecting the grounding conductor 7 and the patch part 8; and slots 10a and 10b formed by being surrounded by the patch part 8, the grounding conductor 7 and the short-circuit lines 5a and 5b. When the maximum length in the horizontal direction of the patch part 8 is defined as A and the maximum length in a direction orthogonal to the horizontal direction along the window glass for the vehicle is defined as B, an aspect ratio A/B is 0.5 to 2.0. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antenna formed on the surface of a vehicle window glass, and more particularly to an antenna formed on a vehicle compartment side surface of a vehicle window glass that is attached to the vehicle at a predetermined angle.

  Conventionally, as a rear window glass for automobiles, an antifogging device for removing dew condensation on the window glass by heating a heater wire, and an antenna for receiving radio waves of AM, FM, TV, etc. provided in the margin A rear window glass in which is formed is known.

  For example, an antifogging device (defogger) formed on the surface of a rear window glass for a vehicle and a glass antenna in which an antenna for receiving a TV broadcast wave is formed on the antifogging device are disclosed (for example, Patent Document 1). reference). This glass antenna is a type of antenna that receives broadcast waves by forming a linear conductor on the surface of a window glass.

  As a type in which a non-linear antenna is formed on a rear window glass for an automobile, a type in which a slot antenna is formed is disclosed (for example, see Patent Document 2). In this glass antenna, a reflector is mounted on the vehicle interior side so that the vehicle window glass on which the glass antenna is formed has a directional characteristic in the horizontal direction with respect to the antenna even when it has a predetermined inclination.

  Further, there is disclosed a slot antenna in which a slot is formed by a conductive film affixed on a window glass of a vehicle body, a vehicle body, and a conductive portion that conducts the conductive film and the vehicle body (for example, Patent Document 3). reference).

JP 2006-197184 A JP 2005-026783 A JP2002-290145

  The glass antenna disclosed in Patent Document 1 is an antenna for receiving a high frequency typified by a TV broadcast wave by forming a glass antenna made of a linear conductor on the surface of a vehicle window glass. . In this case, if it is formed in the vicinity of other conductors such as an automobile body, an antifogging device, and an AM antenna, the antenna directivity changes from the horizontal plane, so that the antenna formation position is extremely limited. There is. That is, it is not suitable for use in a vehicle window glass that is inclined in a plane closer to the horizontal direction.

  In addition, the slot antenna disclosed in Patent Document 2 is formed on the surface of a vehicle window glass together with a reflector in order to direct the strong sensitivity existing in the direction perpendicular to the surface of the slot antenna in the horizontal direction of the vehicle. An antenna for receiving a high frequency typified by a TV broadcast wave is configured. In this case, there is a problem that providing a reflector or the like causes a cost increase due to an increase in the number of parts.

  The slot antenna disclosed in Patent Document 3 is an antenna that forms a slot with the conductive film and the vehicle body as a receiving surface, and the shape of the slot antenna depends on the shape of the opening of the vehicle body. There is a problem that the degree of freedom of design is limited.

  Therefore, an object of the present invention is to provide a simple glass antenna for a vehicle having high sensitivity in the horizontal direction when attached to the vehicle.

  A glass antenna for a vehicle according to the present invention is a glass antenna for a vehicle formed on a surface of a window glass for a vehicle, and includes a patch portion made of a conductor and the same surface as the patch portion and surrounds the patch portion. Formed by surrounding the ground conductor made of a conductor, a short-circuit wire made of a conductor connecting the ground conductor and the patch portion, and the patch portion, the ground conductor and the short-circuit wire. Slot, and A is the maximum horizontal length of the patch portion, and B is the maximum length in the direction perpendicular to the horizontal direction along the vehicle window glass. B is 0.5 to 2.0.

  Further, the patch section is a rectangular conductor having a side of the length A and a side of the length B.

  Further, A + B is 0.5 to 0.55λg, where λ is a wavelength of a radio wave received by the antenna and g is a wavelength shortening rate depending on the vehicle window glass.

  Further, the short-circuit line is characterized in that it is formed at two places on the line extending in the orthogonal direction passing through the approximate center of the patch portion.

  Further, the slot is formed in a U-shape including a non-conductive portion extending in the horizontal direction and a non-conductive portion extending in the orthogonal direction, and the width of the non-conductive portion extending in the horizontal direction. Is defined as C = 0.02λg to 0.03λg, and when the width of the non-conductive portion extending in the orthogonal direction is defined as D, the width D is defined as D = 0. It is defined by 04λg to 0.05λg, and when the width of the ground conductor is E, the width E is defined by E = 0.05λg to 0.06λg.

  According to the glass antenna for a vehicle of the present invention, a slot antenna having high sensitivity in a direction at a low angle with respect to the surface of the glass antenna for a vehicle can be obtained. That is, when the glass antenna according to the present invention is attached to a vehicle, the vehicle can have a favorable sensitivity in the horizontal direction.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same components will be described with the same reference numerals.

  First, a glass antenna for a vehicle according to an embodiment of the present invention will be described.

(Example)
FIG. 1 shows an example in which a vehicle glass antenna according to an embodiment of the present invention is formed on the inner surface of a vehicle window glass 2. As shown in FIG. 1, the vehicle glass antenna 3 according to the embodiment is disposed on the vehicle interior side surface 2 </ b> A located at the peripheral edge 2 a of the vehicle window glass 2 in the window glass of the vehicle 1. And this glass antenna 3 for vehicles is formed as an antenna which receives the horizontal polarized wave which arrives from the horizontal direction, such as the radio wave transmitted from the base station etc. which concern on TV radio wave broadcasting, especially a digital TV broadcast wave, for example. Yes. The vehicle window glass 2 shown in FIG. 1 is inclined at a predetermined angle in a spatial region composed of the horizontal X-axis and Y-axis and the vertical Z-axis. Note that the vehicle glass antenna 3 is formed on a vehicle window glass having various angles because there are various types of vehicles other than the vehicle shown in the figure.

  In FIG. 2, the structure of the glass antenna for vehicles of one Example by this invention is shown. The vehicle glass antenna 3 includes a ground conductor 7 provided on the outside, a patch portion 8 provided in the center, short-circuit lines 5 a and 5 b that short-circuit the ground conductor 7 and the patch portion 8, and a ground conductor 7 and the patch portion 8. And a power supply unit 4 for supplying power. The ground conductor 7, the patch portion 8, and the short-circuit wires 5 a and 5 b are printed with a paste containing a conductive metal such as a silver paste on the vehicle interior side surface 2 </ b> A located at the peripheral portion 2 a of the vehicle window glass 2. And baked to form. In addition, the glass antenna 3 for vehicles can also be formed by another method. For example, a thin film made of a conductive material such as copper can be formed on the vehicle interior side surface or outside, and therefore the material and the formation method of the vehicle glass antenna 3 are not limited to the above.

  The short-circuit lines 5a and 5b pass on the line SS ′ extending in the direction perpendicular to the horizontal direction (Y-axis direction in the present embodiment) along the vehicle window glass 2 passing through the approximate center of the patch portion 8. Are formed in two places. The vehicle glass antenna 3 functions as a slot antenna by forming the ground conductor 7, the patch portion 8, and the short-circuit wires 5a and 5b and forming the U-shaped slot portions 10a and 10b therebetween. Let Accordingly, the slot portions 10 a and 10 b are configured by a non-conductor portion extending in the horizontal direction and a non-conductor portion extending in a direction perpendicular to the horizontal direction along the vehicle window glass 2. The glass antenna 3 for vehicles is prescribed | regulated so that it may become a specific slot shape with the horizontal dimension A and the vertical dimension B of a patch part based on the reason mentioned later. The dimension A is the length of the horizontal end of the patch part, and the dimension B is the length of the vertical end along the vehicle window glass 2.

Specifically, the glass antenna 3 for vehicles is prescribed | regulated as follows.
A / B (aspect ratio) = 0.5-2.0;
A + B = 0.5λg to 0.55λg;
Here, λg can be determined in a frequency band of 400 to 700 MHz that resonates with the shortening rate g of the vehicle window glass. For example, a shortening rate of 0.7 due to the vehicle window glass and a resonance frequency of 470 MHz (wavelength λ = 638 mm), λg = 447 mm. The shortening rate is determined by a value obtained by dividing the electrical wavelength considering the dielectric effect by the wavelength in free space.

Other dimensions include the widths C and D of the slots, the width E of the ground conductor 7, the distance F from the short-circuit line 5a to the feeding point 4, and the distance G from the end of the patch 8 to the line SS ′. Is defined as follows.
Slot width C = 0.02λg to 0.03λg;
Slot width D = 0.04λg to 0.05λg;
The width E of the ground conductor 7 = 0.05λg to 0.06λg;
Distance F from short circuit 5a to feed point 4 = 0.1λg;
Distance G = 0.4 × A to 0.6 × A from the vertical end of the patch portion 8 to the line SS ′;
Here, the distance G can be a distance from one of the vertical side end portions on both sides of the patch portion 8 substantially parallel to the line SS ′.

  It should be noted that, by predetermining dimensions C to E serving as a reference for defining the aspect ratio A / B, it is suitable for an arbitrary frequency band or an arbitrary angle. A glass antenna can be configured. The dimension of F can be varied for impedance matching. However, in order to facilitate the antenna pattern design, it is preferably only defined as F = 0.1λg. Further, as will be described later, the distance G is preferably defined as G = 0.4 × A to 0.6 × A in order to obtain a strong sensitivity characteristic in a direction horizontal to the surface of the antenna. .

  The glass antenna according to the present invention can provide a glass antenna for a vehicle having suitable sensitivity in a desired frequency band with respect to radio waves arriving from the horizontal direction required for the vehicle by defining the aspect ratio A / B. It becomes like this.

  As an example of realization, the dimension example of each dimension AG is shown in Table 1 (unit: mm). According to the present invention, A / B (aspect ratio) is defined as 0.5 to 2.0 for reasons described later, and other values of A / B (aspect ratio) are used for comparison. Note that it is shown.

  Next, the reason why the vehicle glass antenna 3 shown in FIG. 2 is highly sensitive to radio waves coming from the horizontal direction when applied to the vehicle 1 as shown in FIG. 1 will be described.

  FIG. 3 shows a state in which the vehicle glass antenna 3 is formed on the vehicle interior side surface 2A of the vehicle window glass 2 that is spatially inclined at a predetermined angle. In FIG. 3, the glass antenna 3 for a vehicle has a plane (S−S ′ (FIG. 2)) on which the value on the Y axis is constant so that the power feeding part 4 is on the upper side with respect to the vehicle 1. It is formed on a plane parallel to the plane consisting of the X axis and the Z axis. Moreover, the window glass 2 for vehicles has angle (theta) with respect to the horizontal surface H (surface parallel to the surface which consists of a X-axis and a Y-axis). The glass antenna for vehicles is desired to have a suitable sensitivity to radio waves coming from the horizontal direction. That is, in FIG. 3, sensitivity to radio waves coming from the direction of the horizontal plane H is desired. In other words, it is desirable that the angle φ with respect to the surface of the vehicle glass antenna has a good sensitivity in the range of 0 ° to θ.

  FIG. 4 shows a state in which the angle φ between the surface of the vehicle glass antenna 3 and the incoming radio wave, and the U axis, the V axis, and the W axis indicating the spatial direction of the vehicle glass antenna 3 are defined. FIG. The U axis and the V axis represent the surface of the vehicle glass antenna 3 (that is, the surface of the vehicle window glass 2), and the W axis represents a direction perpendicular to the surface of the vehicle glass antenna 3. Therefore, as shown in FIG. 4, the angle φ is expressed as, for example, an angle φ = 0 degrees, 30 degrees, 60 degrees, and 90 degrees with reference to the U axis, the V axis, and the W axis.

  5 to 8 show sensitivity characteristics at frequencies of 400 MHz, 500 MHz, 600 MHz, and 700 MHz, respectively, and show average sensitivity characteristics of the vehicle glass antenna 3 with respect to the angle φ according to the aspect ratio (A / B), respectively. Yes. Here, the average sensitivity shown in FIG. 5 to FIG. 8 is an average value of sensitivity in all directions in each angle.

  As can be seen from the characteristic results of FIGS. 5 to 8, when attention is paid to the vicinity of the angle φ = 0 to 30 degrees, at a frequency of 400 MHz (FIG. 5) and a frequency of 500 MHz (FIG. 6), the aspect ratio (A / B) is 0. It can be seen that it is preferably 5 or more. It can also be seen that at frequencies of 600 MHz and 700 MHz (FIGS. 7 and 8), the aspect ratio (A / B) is 2.0 or less and the influence of the aspect ratio (A / B) is small.

  Therefore, by defining the aspect ratio (A / B) to be 0.5 to 2.0, it is possible to achieve a good sensitivity at an angle φ = 0 to 30 degrees. For example, as shown in FIG. It can be seen that when the vehicle glass antenna 3 is provided on the upper portion of the rear window glass of a simple sedan vehicle (window glass attachment angle θ is about 20 to 30 degrees), it is understood that suitable sensitivity can be obtained. More preferably, A + B = 0.5λg to 0.55λg is defined so as to be defined by the aspect ratio (A / B).

  FIG. 9 shows an average sensitivity characteristic obtained by averaging values measured at intervals of 50 MHz with respect to a frequency band from 400 to 800 MHz, and shows an average sensitivity characteristic of the glass antenna 3 for a vehicle with respect to an angle φ according to an aspect ratio. . Table 2 shows numerical data of FIG.

  From FIG. 9 and Table 2, it can be seen that if the aspect ratio is 0.5 or more and 2.0 or less, a suitable sensitivity can be obtained at an angle φ = 0 to 90 degrees. Thus, the aspect ratio is defined as A / B = 0.5 to 2.0. Other A / B (aspect ratio) values (eg, A / B = 0, 0.17, 0.31, 2.4, etc.) are shown for comparison.

  Next, in order to clarify the effect of the above-described embodiment, a comparative example of a glass antenna for a vehicle that is particularly equivalent to an aspect ratio = 0 will be described. In addition, the same reference number is attached | subjected and demonstrated to the same component.

(Comparative example)
FIG. 10A is a diagram showing an outer shape of a typical conventional slot antenna as a comparative example. Here, the conventional typical slot antenna shown in FIG. 10A is equivalent to a glass antenna having an aspect ratio of 0 (A / B = 0). FIG. 10B is a diagram illustrating measurement conditions of a conventional typical slot antenna as a comparative example. In the slot antenna of the comparative example, the conductive member 17 forms a linear slot 20, and the feeding portion 14 is provided in a part of the conductive material 17. As shown in FIG. 10A, as a general dimension, the length and width of the slot are given as 0.5λg and 0.042λg, respectively. The length of the conductive member 17 is given as 0.605λg and 0.152λg, respectively. The conductive member 17 can be formed on the vehicle window glass by the same material and method as in the above-described embodiment of the present invention.

  FIG. 11 is a diagram comparing the comparative example (aspect ratio = 0) and the example (aspect ratio = 1.58) with respect to the sensitivity in the entire circumferential direction at an angle φ = 0 degree at 450 MHz. It can be seen that the glass antenna 3 for the vehicle according to the example of the present invention has an improved antenna performance at an angle φ = 0 degrees compared to the slot antenna as shown in the conventional comparative example.

  FIG. 12 shows the frequency-average sensitivity characteristic in the direction of angle φ = 0 degrees between the comparative example and the glass antenna 3 for vehicle according to the example of the present invention (aspect ratio 1.58). It can be seen that the vehicle glass antenna 3 of the example according to the present invention has a flat antenna performance with no significant decrease in sensitivity over a frequency range of 400 to 800 MHz with respect to the slot antenna 13 of the comparative example.

  Providing a glass antenna for a vehicle having flat antenna performance in this way requires only attention to the aspect ratio, and has the effect of greatly facilitating antenna design.

  As is clear from the above-described embodiment, the glass antenna 3 for vehicles has two slots having almost the same length. In each slot, a magnetic current having substantially the same frequency band is excited. The magnetic current excited in the two slots has a strong sensitivity in the direction perpendicular to the plane of the antenna when the slots are close to each other (that is, when the aspect ratio is small). This is also clear from the fact that when the aspect ratio is 0, that is, when there is only one slot, a strong sensitivity characteristic is exhibited in the direction perpendicular to the plane of the antenna.

  When the two slots are separated (that is, when the aspect ratio is large to some extent), the magnetic current is excited also in the non-powered slot due to mutual interference. The magnetic current of the slot on the non-powered side is out of phase with the magnetic current of the slot on which power is supplied. Therefore, the two magnetic currents are combined to generate circularly polarized waves in the vertical direction. Will generate horizontal polarization.

  Therefore, in the case of one slot, the direction perpendicular to the antenna surface is a direction having strong sensitivity. However, in the case of two slots, it is strong to some extent not only in the vertical direction but also in the horizontal direction. Has sensitivity. Further, when the interval between the two slots is increased, the interference itself becomes weak, so that each acts as one independent slot, and it is expected that the sensitivity characteristic becomes stronger in the vertical direction.

  Such a phenomenon, that is, interference occurs when the frequency bands of the magnetic currents excited in the two slots are almost the same. That is, this occurs when the lengths of the two slots are substantially the same. In order to obtain such an effect, the range of the distance G is preferably 0.4 × A to 0.6 × A, more preferably 0.45 × A to 0.55 × A, 0.5A That is, it is most preferable that the slots have the same length.

  In the above-described embodiment, the description has been made so that the single glass feeder 3 is configured in the glass antenna 3 for a vehicle. However, if necessary, a plurality of power feeders may be provided so as to achieve impedance matching.

  In the above-described embodiment, the vehicle rear window glass 2 is described as having one vehicle glass antenna 3. However, not only the vehicle rear window glass but also a plurality of vehicle front window glasses or side window glasses are provided. The vehicle glass antenna 3 can be provided, and the received signals from the respective antennas can be used for diversity combining.

In the above-described embodiment, the vehicle glass antenna 3 has been described as having a rectangular shape.
As long as the effect of defining the above-described aspect ratio or other dimensions is exhibited, the shape may be a rhombus, or the shape of the antenna end may be rounded.

  Although the present invention has been described as a representative example in the embodiments described above, it will be apparent to those skilled in the art that many changes and substitutions can be made within the spirit and scope of the present invention. For example, in the above-described embodiments, the aspect ratio may be set so as to be adapted to a specific frequency band or a specific vehicle. In this case, there is an effect that the antenna design is further facilitated. Moreover, although the glass antenna for vehicles was demonstrated as a structure provided in the upper part of the window glass for vehicles, the arrangement structure can be suitably changed including arrangement | positioning of an electric power feeding part. Accordingly, the invention should not be construed as limited by the embodiments described above, but only by the claims.

  ADVANTAGE OF THE INVENTION According to this invention, the vehicle glass antenna of a very favorable sensitivity can be comprised also with respect to the vehicle window glass of all vehicle forms, and it is useful in a vehicle provided with such a glass antenna for vehicles.

It is a figure which shows an example which formed the glass antenna for vehicles of the Example by this invention in the inner surface of the window glass 2 for vehicles. It is a block diagram of the glass antenna for vehicles of one Example by this invention. It is the schematic which shows a mode that the glass antenna for vehicles is formed in the vehicle interior side surface of the window glass for vehicles inclined in the predetermined angle spatially. It is a figure which shows the mode which prescribed | regulated the U axis | shaft which shows the angle (phi) in which the glass antenna for vehicles receives an electromagnetic wave, and the spatial direction of the glass antenna for vehicles, and the W axis. It is a figure which shows the average sensitivity characteristic of the glass antenna for vehicles with respect to angle (phi) according to aspect ratio (A / B) in frequency 400MHz. It is a figure which shows the average sensitivity characteristic of the glass antenna for vehicles with respect to angle (phi) according to the aspect-ratio (A / B) in frequency 500MHz. It is a figure which shows the average sensitivity characteristic of the glass antenna for vehicles with respect to angle (phi) according to the aspect-ratio (A / B) in the frequency of 600 MHz. It is a figure which shows the average sensitivity characteristic of the glass antenna for vehicles with respect to angle (phi) according to aspect ratio (A / B) in frequency 700MHz. It is an average sensitivity characteristic obtained by averaging values measured at intervals of 50 MHz with respect to a frequency band from 400 to 800 MHz. It is a figure which shows the external shape of the conventional typical slot antenna as a comparative example. As a comparative example, it is a figure which shows the measurement conditions of the conventional typical slot antenna. It is the figure which compared the comparative example (aspect ratio = 0) and the Example (aspect ratio = 1.58) about the sensitivity of all the circumference directions of the angle (phi) = 0 degree direction in 450 MHz. It is a figure which shows the frequency-average sensitivity characteristic of an angle (phi) = 0 degree direction between the comparative example (aspect ratio = 0) and the glass antenna 3 for vehicles of the Example by this invention (aspect ratio 1.58).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Rear window glass for vehicles 3 Glass antenna for vehicles 4 Feed part 5a, 5b Short-circuit wire 7 Patch part 8 Grounding conductor 10a, 10b Slot

Claims (5)

A vehicle glass antenna formed on the surface of a vehicle window glass,
A patch portion made of a conductor;
A ground conductor made of a conductor formed on the same surface as the patch portion and surrounding the patch portion;
A short-circuit wire made of a conductor connecting the ground conductor and the patch portion;
A slot formed by surrounding the patch portion, the ground conductor and the short-circuit wire,
When the maximum horizontal length of the patch portion is A and the maximum length in the direction perpendicular to the horizontal direction along the vehicle window glass is B, the aspect ratio A / B is 0.5. A glass antenna for a vehicle, which is -2.0.   The glass antenna for a vehicle according to claim 1, wherein the patch portion is a rectangular conductor having a side of the length A and a side of the length B.   The A + B is 0.5 to 0.55λg, where λ is a wavelength of the radio wave received by the antenna and g is a wavelength shortening rate depending on the vehicle window glass. 2. The glass antenna for vehicles according to 2.   The said short circuit line is formed in two places on the line extended in the said orthogonal direction which passes through the approximate center of a patch part, The glass antenna for vehicles in any one of Claims 1-3 characterized by the above-mentioned. The slot is configured in a U-shape including a non-conductive portion extending in the horizontal direction and a non-conductive portion extending in the orthogonal direction,
When the width of the non-conductor portion extending in the horizontal direction is C, the width C is defined by C = 0.02λg to 0.03λg,
When the width of the non-conductor portion extending in the orthogonal direction is D, the width D is defined by D = 0.04λg to 0.05λg,
5. The glass antenna for a vehicle according to claim 1, wherein when the width of the ground conductor is E, the width E is defined by E = 0.05λg to 0.06λg. .

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