JP4988445B2 - Glass antenna for vehicles - Google Patents

Description

  The present invention relates to a glass antenna for a vehicle, and more particularly to a glass antenna for a vehicle composed of at least four antenna elements.

  As a glass antenna for a vehicle for digital TV (frequency: 470 to 770 MHz), there is one in which two antenna elements are provided on a windshield or rear glass by a diversity method.

  FIG. 1 shows a glass antenna according to the prior art. Two monopole antennas 12 a and 12 b extending in the lateral direction are provided near the upper part of the side of the windshield 10. The monopole antennas 12 a and 12 b are provided at a position of 130 mm from the upper side of the windshield 10. In the figure, reference numerals 14a and 14b denote feeding points of these monopole antenna elements, respectively.

  Japanese Patent Application Laid-Open No. 2000-252732 (Patent Document 1) discloses a vehicle glass antenna provided on a rear glass of an automobile, and includes an antenna element extending from left and right sides of the rear glass and one antenna extending from an upper side. An antenna including an element and one antenna element extending from a lower side is disclosed. According to this, the television broadcast band is received with diversity in multiple channels, so that the low sensitivity directions of the individual antenna elements are compensated for each other, and an antenna with good reception sensitivity can be obtained in any direction of the automobile. It is done.

  Japanese Patent Application Laid-Open No. 2002-135025 (Patent Document 2) discloses a glass antenna in which two antenna elements are provided on a windshield and two antenna elements are provided on a rear glass. In addition, by setting the antenna element around the roof or pillar of an automobile, the roof or pillar functions as a reflector to control the directional characteristics of the antenna and to form a ranger around the antenna element. Is disclosed to control the directivity of the antenna element. Furthermore, it is disclosed that the directivity in a horizontal plane is complemented by selecting these antenna elements having directivity in different directions by a diversity circuit.

  The conventional glass antenna provided on the windshield or rear glass shown in FIG. 1 is affected by the vehicle body in the side direction, rear direction, or front direction when viewed from the windshield side or rear glass side, respectively. The gain in the inward direction is reduced.

  In the antenna described in Patent Document 1, it is necessary to form an antenna element extending from the upper side and an antenna element extending from the lower side. Therefore, the area of the defogger is reduced, or the area where the antenna element is formed is distributed on the upper side or the lower side, which is an adverse effect when other antenna elements are set.

  In addition, depending on the car, a wiper is set on the rear glass, so when setting the antenna element on the lower side, the area for forming the antenna element cannot be secured or even if it is formed, it is affected by the wiper and is sufficient. There is a problem that it is not possible to ensure proper characteristics.

  Moreover, since the antenna described in Patent Document 2 cannot obtain good reception sensitivity characteristics in the vehicle interior direction for each window glass, it is necessary to form antenna elements on both the front and rear window glasses. Will increase.

  In addition, the antenna of a car may be tuned by each glass manufacturer. At that time, if the window glass ordering manufacturer differs between the windshield and the rear glass, there is a possibility that problems such as troubles in tuning may occur.

  An object of the present invention is to provide a glass antenna for a vehicle which is a TV glass antenna integrated on a single window glass and which solves the above-mentioned problems.

The present invention relates to a glass antenna for a vehicle formed or attached to the surface of a window glass of a vehicle, wherein the distance from the side of the window glass is 0.1λk to 0.4λk (λ is a wavelength, k is a shortening rate). And at least two first antenna elements extending downward from the upper side of the window glass without contacting the upper side, and 0.1λk to 0.4λk (λ is a wavelength from the upper side of the window glass) , K is a shortening rate), and includes at least two second antenna elements extending in a lateral direction from the side portion of the window glass without being in contact with the side . The antenna element and the second antenna element constitute diversity.

It is preferable that there is no conductor parallel to the first antenna element extending downward between the first antenna element and the side of the window glass . This means that no radiator is provided around the antenna element.

  According to the present invention, since at least four antenna elements are formed on one window glass, costs are suppressed, and there are no tuning problems that occur due to spanning a plurality of window glasses.

  In addition, since there is no antenna element extending from the lower side, it can be suitably arranged on a window glass provided with a rear wiper, and can also be applied to a windshield in which formation of an antenna element on the lower side is restricted. be able to.

  An embodiment of a glass antenna for a vehicle according to the present invention will be described with reference to the drawings.

  FIG. 2 shows a first embodiment of the vehicle glass antenna. This glass antenna is provided on a rear glass 8 having a defogger 6. This glass antenna includes two monopole antenna elements 16a and 16b extending downward from the vicinity of the end of the upper side 7 of the rear glass, and two monopole antennas extending laterally from the vicinity of the upper side of the rear glass side 9. Elements 18a and 18b are provided. The monopole antenna elements 18a and 18b are provided at positions (indicated by Y in the figure) below 0.1λk to 0.4λk from the upper side of the rear glass. By providing these antenna elements at such positions, an area in which no conductor parallel to the antenna element exists is secured in the vicinity of the antenna element, so that the influence of the antenna element on other conductors can be reduced. Further, the monopole antenna elements 16a and 16b are provided at positions (indicated by X in the drawing) in the lateral direction of 0.1λk to 0.4λk from the upper edge of the rear glass. By providing these antenna elements at such positions, an area where there is no conductor parallel to the antenna element is secured in the vicinity of the antenna element, so that the influence of the antenna element on other conductors can be reduced. As will be described later, high reception sensitivity can be obtained in the direction toward the vehicle interior.

  In the figure, the ◯ mark at the base of each antenna element indicates a feeding point, and no reference number is given for the sake of simplicity.

  The length of each antenna element is λk / 4. Here, λ is a wavelength, for example, 508 mm, and k is a wavelength shortening rate by glass, for example, 0.7.

  FIG. 3 shows the measurement results of the sensitivity in the front direction (front direction of the vehicle) when the position (X) from the upper edge of the antenna elements 16a and 16b is changed. It can be seen that the preferred range of sensitivity is 0.1λk to 0.4λk.

  FIG. 4 shows the directivity (diversity method using four antenna elements) when the position (X) of the antenna elements 16a and 16b is 0.2λk in the first embodiment, and the two antennas shown in FIG. The directivity of the diversity method by the antenna element is measured (at a frequency of 590 MHz), and a comparison result is shown. From this comparison result, the glass antenna of the example is provided with an antenna element extending in the vertical direction, so that the sensitivity in the vehicle interior direction (front direction in FIG. 4) and the side direction of the vehicle is improved. Although the antenna element is formed on a single window glass, it can be seen that the antenna has excellent directivity. Furthermore, since the shape of the antenna element is simple, the antenna can be adjusted relatively easily.

  The directivity of the antenna element was measured as follows. In an anechoic chamber, radio waves having a frequency in the TV band are radiated from a transmitting antenna toward a vehicle installed far in the horizontal direction of the antenna. Here, by measuring the voltage of the signal received by the glass antenna while rotating the vehicle 360 ° horizontally by the turntable, the reception voltage of the signal for each rotation angle of the vehicle and each frequency is obtained. Further, by plotting the obtained received voltage on a radar chart for each frequency, a chart of directivity for each frequency is obtained.

  Here, in this example, the signal received by the glass antenna was taken out by connecting the central conductor of the coaxial cable to the feeding point and connecting the outer conductor of the coaxial cable to the vehicle body above the feeding point.

  In the directivity chart, the upper direction represents the front direction of the vehicle, the lower direction represents the rear direction of the vehicle, and is represented as the directivity characteristic when the vehicle is viewed from above.

  FIG. 5 shows a second embodiment of the vehicle glass antenna of the present invention. This glass antenna is provided on the windshield 10. The glass antenna extends in the lateral direction from two inverted T-shaped monopole antenna elements 20a and 20b extending downward from the vicinity of the end of the glass upper side 4 and from the vicinity of the upper part of the side 2 of the windshield. Two monopole antenna elements 18a and 18b are provided. The monopole antenna elements 18a and 18b are provided at positions below 0.1λk to 0.4λk from the upper side of the rear glass. The monopole antennas 20a and 20b are provided at positions in the lateral direction of 0.1λk to 0.4λk from the upper edge of the rear glass. The inverted T-shaped antenna element is obtained by connecting elements 19a and 19b extending in the lateral direction to the lower part. In the case of such an inverted T-shaped antenna element, the length of the antenna element is the length from the feeding point to one end of the lateral element.

  The results of measuring the frequency characteristics of the gain with respect to the horizontal polarization of the single antenna element of the glass antenna are shown in FIG. The result of measuring the property is shown in FIG. FIG. 7 shows the directivity of the conventional glass antenna shown in FIG. 1 in the two-channel diversity method for comparison.

  As can be seen from FIG. 7, the structure shown in FIG. 5 improves the ripple existing in the direction toward the vehicle interior (the lower half in FIG. 7) and shows good reception characteristics. .

  As described above, by providing an antenna having an antenna element extending in the vertical direction, the characteristics in the direction toward the inside of the vehicle are improved, and even with an antenna formed on a single window glass, it has excellent directivity. Antenna is obtained.

  As mentioned above, although the Example of this invention was described, this invention is not limited to the said Example, A various deformation | transformation and change are possible within the scope of the present invention.

  For example, in the first embodiment, the number of antenna elements extending downward may be two or more, and the number of antenna elements extending laterally may be two or more.

  Further, in the second embodiment, the antenna elements 20a and 20b are not limited to the inverted T-shape, and may be L-shaped or mirror-symmetric L-shaped as shown in FIGS. 8A and 8B. .

  The glass antenna of the present invention may be provided not only on the windshield or rear glass but also on the side glass.

It is a figure which shows the conventional glass antenna. It is a figure which shows the glass antenna of 1st Example. It is a graph which shows the sensitivity of the front direction of the glass antenna of 1st Example. It is a figure which shows the directivity characteristic of the gain of the glass antenna of 1st Example compared with a conventional type. It is a figure which shows the glass antenna of 2nd Example. It is a table | surface which shows the frequency characteristic of the gain of the glass antenna of 2nd Example. It is a figure which shows the directivity characteristic of the gain of the glass antenna of 2nd Example. It is a figure which shows the modification of the glass antenna of this invention.

Explanation of symbols

5 Defogger 8 Rear glass 10 Front glass 12a, 12b Antenna extending in the horizontal direction 16a, 16b Antenna extending in the vertical direction 20a, 20b Inverted T-shaped antenna extending in the vertical direction

Claims (2)

A vehicle glass antenna formed or attached to the surface of a vehicle window glass,
It is provided at a distance of 0.1λk to 0.4λk (λ is a wavelength, k is a shortening rate) from the side of the window glass, and extends at least downward from the upper side of the window glass without contacting the upper side. Two first antenna elements;
It is provided at a distance of 0.1λk to 0.4λk (λ is a wavelength, k is a shortening rate) from the upper side of the window glass, and from the side of the window glass toward the lateral direction without contacting the side And at least two second antenna elements extending,
The glass antenna for vehicles which comprises diversity by the 1st antenna element and the 2nd antenna element. Between the first antenna element and the window glass side edge, according to claim 1, characterized in that said extending downward first antenna element parallel conductor was not present Vehicle glass antenna.

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