JP2013138294A - Vehicular glass antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicular glass antenna that allows placement of, e.g., a DAB antenna having satisfactory reception characteristics without sacrificing the reception sensitivity of an AM antenna.SOLUTION: The glass antenna comprises: a first antenna 31 having a plurality of horizontal elements 31a to 31l and vertical elements; and a second antenna 32 capacitatively coupled with a topmost one 31a of the horizontal elements of the first antenna and arranged in an upper part of a region in which the first antenna is mounted. The first antenna includes the horizontal element located on the top among the plurality of horizontal elements, a first vertical element 33a in contact with the horizontal element, and a second vertical element 33b. The first vertical element and the second vertical element are placed substantially in parallel across a gap d with which the reception sensitivity of each of the first antenna and the second antenna is set in a satisfactory range, and a slit 33 having a predetermined height is formed by the gap d. An electrical connection is established between the bottommost ends of the first vertical element and the second vertical element.

Description

  The present invention relates to a glass antenna for a vehicle mounted with a DAB (Digital Audio Broadcasting) antenna having good reception characteristics.

  For example, Patent Documents 1, 2, and 3 disclose a glass antenna for a vehicle in which a DAB antenna is mounted. Specifically, in Patent Document 1, as shown in FIG. 12 of the same document, an L-shaped DAB antenna is located beside the AM antenna and is arranged adjacent to the AM antenna on the left and right. . Further, in Patent Document 2, as shown in FIG. 9 of the same document and in FIG. 9 of Patent Document 3, the DAB antenna is configured to be incorporated in the AM antenna.

  However, according to the techniques disclosed in Patent Documents 1, 2, and 3, the arrangement area of the AM antenna is limited by the presence of the DAB antenna, and as a result, the reception sensitivity of the AM antenna is lowered. That is, the reception sensitivity of the AM antenna increases as the antenna arrangement area increases. On the other hand, the arrangement of the DAB antenna reduces the AM antenna arrangement area and the reception sensitivity decreases accordingly.

JP 2010-81567 A JP 2010-154504 A JP 2010-124444 A

  The present invention has been made to solve the above-described problems, and provides a glass antenna for a vehicle in which a DAB antenna or the like having good reception characteristics can be disposed without reducing the reception sensitivity of an AM antenna. The purpose is to do.

  A glass antenna for a vehicle according to claim 1 is disposed on a first antenna composed of a plurality of horizontal elements and vertical elements, and on an area where the first antenna is mounted. A second antenna capacitively coupled to an upper horizontal element, wherein the first antenna is a first of the plurality of horizontal elements that is in contact with the horizontal element and the upper horizontal element. The first vertical element and the second vertical element are substantially parallel to each other, and both the first antenna and the second antenna have good reception sensitivity. A slit having a predetermined height is formed in the gap, and the lowermost ends of the first vertical element and the second vertical element are electrically connected. It is characterized by that.

  According to a second aspect of the present invention, in the glass antenna for a vehicle according to the first aspect, the gap is selected in a range of 2 to 20 mm.

  According to a third aspect of the present invention, in the glass antenna for a vehicle according to the first aspect, the fixed height is a size adjusted to be approximately ¼λ or less.

  According to a fourth aspect of the present invention, in the glass antenna for a vehicle according to any one of the first to third aspects, the first vertical element forming the slit is perpendicular to a feeding terminal of the second antenna. It is characterized by being arranged with an interval of 0 to 100 mm on the basis of the extending virtual straight line.

  The invention according to claim 5 is the glass antenna for a vehicle according to any one of claims 1 to 4, wherein the first vertical filament element that forms the slit is from a feeding terminal of the second antenna. It is characterized by being arranged with an interval of 0 to 60 mm on the basis of a virtual straight line extending vertically.

  According to the first aspect of the present invention, the slit formed in the first antenna is capacitively coupled to the second antenna, whereby a part of the first antenna can be operated as the second antenna. For this reason, the presence of the second antenna does not limit the arrangement area of the first antenna. Therefore, the second antenna can be arranged without reducing the sensitivity of the first antenna.

  In the invention according to claim 2, the predetermined interval is defined in a range in which the reception sensitivity of the first antenna and the second antenna is good. In the evaluation by the inventors, it was found that good reception sensitivity was obtained in the range of 2 to 20 (mm) for both the first antenna and the second antenna, and adjustment was possible within this range.

  In the invention according to claim 3, the fixed height is a size adjusted to be ¼λ or less. In the evaluation by the inventors, it was set to 254 (mm).

  In the invention according to claim 4, the first vertical elements forming the slits are arranged with an interval of 0 to 100 (mm) on the basis of a virtual straight line extending vertically from the feeding terminal of the second antenna. . In the evaluation by the inventor, by arranging the first vertical element with an interval of 0 to 100 (mm), the reception sensitivity of the second antenna is equivalent to the state without the first antenna. It was found that sensitivity was obtained.

  In the invention according to claim 5, the first vertical elements forming the slits are arranged at an interval of 0 to 60 (mm) with reference to an imaginary straight line extending vertically from the feeding terminal of the second antenna. . According to the evaluation by the inventor, by arranging the first vertical elements with an interval of 0 to 60 (mm), the reception sensitivity of the second antenna is equal to or higher than the state without the first antenna. It was found that the sensitivity of

It is a top view of the vehicle with which the glass antenna for vehicles which concerns on a present Example was attached. It is a figure which shows the structure of the glass antenna for vehicles which concerns on a present Example. It is the figure quoted in order to demonstrate the conditions of the simulation of the glass antenna for vehicles concerning a present Example. It is a figure which shows the antenna pattern of the comparative example used for the performance evaluation by simulation of the glass antenna for vehicles which concerns on a present Example. It is the graph which showed the result of the performance evaluation by simulation of the glass antenna for vehicles concerning a present example in contrast with comparative example 1. It is the graph which showed the sensitivity characteristic of the glass antenna for vehicles concerning a present Example in contrast with comparative examples 1 and 2. It is a figure which shows the result of the performance evaluation by simulation of the glass antenna for vehicles concerning a present Example. It is a figure which shows an example of the dimension of each element which comprises the glass-mounted antenna for vehicles which concerns on a present Example.

  Embodiments of the present invention (hereinafter referred to as “examples”) will be described below with reference to the accompanying drawings.

  As shown in FIG. 1, the vehicle glass antenna 30 according to the present embodiment is attached to the rear glass 15 and includes an AM antenna 31 (first antenna) and a DAB antenna 32 (second antenna). Reference numeral 34 denotes a defogger. The vehicle 10 is fitted between a front windshield 13 fitted between the left and right front pillars 12L and 12R (L is a suffix indicating R and R is right; the same applies hereinafter) and a rear pillar 14L and 14R. Rear glass 15, front door glasses 17L and 17R attached to the front doors 16L and 16R so as to be movable up and down, and rear door glasses 19L and 19R attached to the rear doors 18L and 18R so as to be raised and lowered. It has a window glass. Reference numeral 20 denotes a roof.

  The vehicle glass antenna 30 shown here is for receiving radio waves in AM band from two different frequency bands of DAB 174 to 240 [MHz] band III and 1452 to 1492 [MHz] L band. It is an antenna designed.

  FIG. 2 shows the structure of the vehicle glass antenna 30 according to the present embodiment. The glass antenna 30 for a vehicle according to the present embodiment includes an AM antenna 31 (first antenna) and a DAB antenna 32 (second antenna).

  The DAB antenna 32 includes a feeding terminal 32a (hot terminal) disposed above the area where the AM antenna 31 is mounted, and one vertical element 32c extending toward the AM antenna 31 with the feeding terminal 32a as a starting point. And 12 horizontal elements 31a to 31l constituting the AM antenna 31 from the other end of the vertical element 32c and one horizontal element 32d extending substantially in parallel. As will be described later, the DAB antenna 32 is configured to be capacitively coupled to a horizontal element 311 located at the uppermost portion of the AM antenna 31.

  The AM antenna 31 includes a horizontal element 311 located at an upper portion of the plurality of horizontal elements 31 a to 31 l constituting the AM antenna 31, and a vertical element 33 a and a vertical element 33 b in contact with the horizontal element 311. The vertical element 33a and the vertical element 33b are arranged substantially parallel to each other with a gap d in which the reception sensitivity of the AM antenna 31 and the DAB antenna 32 is defined in a good range. 33 is formed. At this time, the lowermost ends of the vertical elements 33a and 33b are electrically connected. The roof 20 is connected to a power supply terminal 32 b (ground terminal) of the DAB antenna 32.

  According to the above configuration, the slit 33 formed in the AM antenna 31 is capacitively coupled to the DAB antenna 32, and can be operated as the DAB antenna 32 including the slit 33. Thus, since it is not necessary to reduce the mounting area of the AM antenna 31 for the DAB antenna 32, the DAB antenna 32 can be designed without reducing the sensitivity of the AM antenna 31.

  The basis for this will be described below. The inventors performed a simulation at a frequency of 174 to 240 MHz, which is the reception band of the DAB antenna 32. The simulation conditions were such that the inclination angle of the rear glass 15 was 30 degrees, as shown in the right side view of the vehicle in FIG. Further, the ground terminal of the antenna is connected to the roof 20, and the y direction of the roof 20 is infinite.

  Also, as shown in FIG. 4A, a glass antenna without an AM antenna and only a DAB antenna 32 mounted thereon, and as shown in FIG. 4B, a DAB antenna 32 including the AM antenna 31 was mounted. A glass antenna is installed on the glass surface of the vehicle 10 as Comparative Example 1 and Comparative Example 2, respectively, and the directivity and sensitivity of vertical polarization in the xy plane are obtained for each frequency of 3 MHZ intervals, and the average sensitivity at all frequencies. Was calculated. Although the roof 20 is infinite (∞), in FIGS. 4A and 4B, it is drawn as a finite one to show the antenna structure.

  The simulation results under the above conditions are summarized in the following table.

  According to said table | surface, the average sensitivity in the case of the comparative example 1 without the AM antenna 31 is -13.7 (dBd), and the average sensitivity in the case of the comparative example 2 with the AM antenna 31 is -21.1 (dBd). It has become. In Comparative Example 1, the antenna length was adjusted so that the average sensitivity of the DAB antenna 32 was maximized in the absence of the AM antenna, and ideal sensitivity was obtained because there was no AM antenna. In Comparative Example 2, the DAB antenna 32 is bent in an L shape in order to avoid intrusion of the AM antenna 31 into the mounting area, and the average sensitivity is lower than that of Comparative Example 1. This is because an antenna element in the vertical direction that is ideal for vertically polarized waves cannot be formed.

  Next, in the vehicle glass antenna 30 of the embodiment shown in FIG. 1, the relationship between the position of the slit 33 and the average sensitivity is simulated, the position l of the slit is plotted on the horizontal axis, and the dipole ratio (average sensitivity) is plotted on the vertical axis. The sensitivity characteristic graphs with the scales are summarized in FIG. 5 and the following table. Here, the slit position refers to the distance from the feeding point (hot terminal 32a) of the DAB antenna 32 to the vertical element 33a of the AM antenna 31 with reference to a virtual straight line x extending vertically.

  According to the sensitivity characteristics of FIG. 5 or the above table, in this example, the range that can be taken as the slit position l equal to or higher than the sensitivity of Comparative Example 1 is 0 to 130 (mm), but a more preferable range is It was 0-100 (mm), and it was 0-60 (mm) most suitably. For example, when the slit position l is 40 (mm), the average sensitivity was -13.7 (dBd) in the comparative example, whereas it was -11.6 (dBd) in the example. Thus, by providing the slit 33 at an appropriate position, even if the AM antenna 31 is provided, the sensitivity equal to or higher than that of the comparative example 1 shown in FIG. This is because the slit 33 is capacitively coupled to the DAB antenna 32, so that the slit 33 as a whole operates equivalent to an element in the vertical direction ideal for the DAB antenna 32.

  It is to be noted that the same effect can be obtained by providing a vertical element that cuts from the horizontal element 31a located at the top of the AM antenna 31 to the horizontal element 31l located at the bottom instead of the slit 33. However, in the case of such a vertical element, for example, when the AM antenna 31 is used in common with the FM antenna, or even if it is a separate element, if both are capacitively coupled, the FM sensitivity may be reduced. This is empirically known and is undesirable because it makes FM and DAB antenna 32 difficult to design.

  Next, the glass antennas 30 of Comparative Examples 1 and 2 and the example described above are attached to the rear glass 15 of the vehicle, and the results of actual measurement in the anechoic chamber are shown in FIG.

  FIG. 6A is a graph showing a simulation result, and FIG. 6B is a graph showing a sensitivity characteristic based on an actual measurement result. As is apparent from FIGS. 6A and 6B or the above table, the actual measurement result is also substantially similar to the simulation result. Therefore, even if the AM antenna 31 is provided, there is no AM antenna. It was confirmed that the sensitivity equal to or higher than that of Comparative Example 1 shown in FIG.

  Next, the simulation result of the relationship between the slit width d and the average sensitivity for the vehicle glass antenna 30 of the example is shown in FIG. 7 and the following table.

  FIG. 7 is a sensitivity characteristic diagram in which the horizontal axis indicates the slit width d (mm), and the vertical axis indicates the respective sensitivity (dBd, dBuV) of the DAB antenna 32 and the AM antenna 31. The slit width here refers to the distance d between the vertical element 33a and the vertical element 33b of the AM antenna 31 constituting the slit 33 shown in FIG. As a result of the simulation, the slit width d at which suitable sensitivity was obtained for both the DAB antenna 32 and the AM antenna 31 was in the range of 2 to 20 mm.

  Here, the height of the slit 33 will be supplemented. The height (antenna length) of the slit 33 here refers to the distance from the feeding terminal 32 a (hot terminal) of the DAB antenna 32 to the horizontal element 31 l located at the bottom of the AM antenna 31. The antenna length used in the above simulation is 260 (mm) as shown in FIG. Assuming that the theoretically required antenna length is λ / 4, assuming that the center frequency 297 (MHz) of the DAB frequency band and the shortening rate 0.7 are λ / 4 = 300/207/4 × 0. 7 = 254 (mm). Therefore, it is necessary to adjust the height of the slit 33 so that the antenna length becomes λ / 4.

  Note that the antenna length described above can be adjusted by selecting a horizontal element on the bottom side (located at the lowest level) among the twelve horizontal elements 31a to 31l constituting the AM antenna 31. A sufficient antenna length cannot be taken in designing the AM antenna 31, and in this case, it may be λ / 4 or less.

  As described above, according to the glass antenna 30 for a vehicle according to the present embodiment, the AM antenna 31 including the plurality of horizontal elements 31a to 31l and the vertical elements 32a and 32b, and the region where the AM antenna 31 is mounted. And a DAB antenna 32 capacitively coupled to a horizontal element 31a located on the top of the AM antenna 31. The AM antenna 31 includes a horizontal element 31a positioned at the upper part of the plurality of horizontal elements 31a to 31l, a first vertical element 32a and a second vertical element 32b in contact with the horizontal element 31a, The first vertical element 32a and the second vertical element 32b are disposed substantially parallel to each other with a gap d in which the reception sensitivity of the AM antenna 31 and the DAB antenna 32 is defined in a favorable range. A slit 33 having a constant height is formed, and the lowermost ends of the first vertical element 32a and the second vertical element 32b are electrically connected. The slit 33 formed in the AM antenna 31 is capacitively coupled to the DAB antenna 32 so that the slit 33 can be operated as the DAB antenna 32. For this reason, the presence of the DAB antenna 32 does not limit the arrangement area of the AM antenna 31, and therefore the DAB antenna 32 can be designed without reducing the sensitivity of the AM antenna 31.

  Moreover, according to the glass antenna 30 for a vehicle which concerns on a present Example, the slit width (space | interval d of the vertical element 33a of the AM antenna 31 and the vertical element 33b) has good reception sensitivity of both the AM antenna 31 and the DAB antenna 32. According to the evaluation by the inventors, it was found that good reception sensitivity was obtained in the range of 2 to 20 mm, and adjustment was possible within this range. The position of the slit 33 indicated by the distance to the vertical element 33a of the AM antenna 31 with reference to a virtual straight line x extending vertically from the feeding terminal (hot terminal 32a) of the DAB antenna 32 is 0 in the evaluation by the inventors. It was found that in the range of ˜100 mm (more preferably, 0 to 60 mm), the sensitivity equivalent to the state without the AM antenna 31 can be obtained. As a result, according to the present invention, it is possible to provide the glass antenna 30 for a vehicle in which a DAB antenna or the like having good reception characteristics can be disposed without reducing the reception sensitivity of the AM antenna.

  DESCRIPTION OF SYMBOLS 10 ... Vehicle, 20 ... Roof, 30 ... Glass antenna for vehicles, 31 ... AM antenna (1st antenna), 31a-31l ... Horizontal element, 32 ... DAB antenna (2nd antenna), 32a ... Feeding terminal (hot) Terminal), 32b ... feed terminal (ground terminal), 32c ... vertical element, 32d ... horizontal element, 33 ... slit, 33a, 33b ... vertical element

Claims (5)

A first antenna comprising a plurality of horizontal elements and vertical elements;
A second antenna that is disposed above the region where the first antenna is mounted and capacitively couples with a horizontal element located at the top of the first antenna;
The first antenna is
Among the plurality of horizontal elements, a horizontal element located above, a first vertical element in contact with the horizontal element, and a second vertical element, wherein the first vertical element and the second vertical element are The first antenna and the second antenna are arranged substantially in parallel with a gap in which the receiving sensitivity is defined in a good range, and a slit having a certain height is formed in the gap, A glass antenna for a vehicle, wherein lowermost ends of the first vertical element and the second vertical element are electrically connected. The gap is
The glass antenna for a vehicle according to claim 1, wherein the glass antenna is selected within a range of 2 to 20 mm. The certain height is
2. The glass antenna for a vehicle according to claim 1, wherein the glass antenna has a size adjusted to be approximately ¼λ or less. The first vertical element forming the slit is
The first antenna is disposed at an interval of 0 to 100 mm with reference to an imaginary straight line extending vertically from a feeding terminal of the second antenna disposed above the area where the first antenna is mounted. The glass antenna for vehicles according to any one of claims 1 to 3. The first vertical element forming the slit is
5. The glass antenna for a vehicle according to claim 1, wherein the glass antenna is disposed at an interval of 0 to 60 mm with reference to an imaginary straight line extending vertically from the power supply terminal of the second antenna. .

Images