JP2009212624A - Antenna apparatus for vehicle window - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna apparatus for vehicle window which can perform fine adjustment of the antenna characteristics while using an existing antenna pattern, as it is, and which does not have risk of disturbing visibility. <P>SOLUTION: An antenna apparatus for vehicle window comprises an antenna element 10, an amplifier circuit 20, a ground pattern 30 and an impedance adjusting section 40. The amplifier circuit 20 has hot terminals 21 and 22, connected to the antenna element 10. The ground pattern 30 is connected with the ground terminal 23 of the amplifier circuit 20. The impedance adjusting section 40 adjusts the impedance on the antenna element side viewed from the receiver side and consists of a pattern which extends from the ground pattern 30 and does not a current pass therethrough. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle window antenna device, and more particularly to a vehicle window antenna device capable of adjusting the impedance of an antenna device provided in a vehicle window.

  An antenna device provided in a vehicle window, more specifically, a glass antenna device for an AM radio or FM radio is often provided in a rear window of the vehicle. In general, the antenna device and the receiver in the vehicle are connected by a coaxial cable, and a body ground is provided in the middle of the coaxial cable. In most areas of the rear window of the vehicle, a defogger heating wire is often provided, and the antenna device is provided in a blank portion where no heating wire is provided so as to avoid the influence of the heating wire. Therefore, there are many restrictions on the arrangement position.

  In addition, in a glass antenna device, there is a glass antenna device in which a matching circuit is provided between a coaxial cable and an antenna element with respect to impedance adjustment for efficiently transferring power and preventing problems of reflection of radio waves (patent) Reference 1).

  In addition, there is one in which impedance adjustment is performed by making a part of the heating wire near the antenna element into a meander shape (Patent Document 2).

JP-A-10-261912 JP 2007-189739 A

  However, the glass antenna device is premised on body earthing and is limited to metal vehicles, and thus can be directly applied to vehicles made of carbon fiber or resin bodies. It was not a thing. In particular, a vehicle with a carbon fiber body generates heat when an electric current is passed through the carbon fiber, so that there is a risk of fire in some cases, so it was not possible to take a body ground.

  Further, the technique disclosed in Patent Document 1 requires a matching circuit, which increases the number of parts and increases the cost. In addition, there are cases where heating wires for defogger and antenna elements for AM / FM radio are present in most areas of the window, and various parts such as cables are arranged inside the vehicle and there is no space for a matching circuit. there were.

  Further, when the heating wire is processed into a meander shape, it is obstructive in appearance and sometimes hinders the driver's view.

  Furthermore, since impedance adjustment is also affected by the antenna pattern and the vehicle body, when designing a glass antenna device, the development of the antenna pattern and the impedance adjustment cannot be considered separately. When the device was installed, it was necessary to adjust the antenna pattern and impedance again.

  In view of such circumstances, the present invention provides a vehicle window antenna device that does not require a matching circuit, allows fine adjustment of antenna characteristics while using an existing antenna pattern as it is, and reduces the possibility of obstructing the field of view. It is something to try. It is another object of the present invention to provide a vehicle window antenna device that can be realized even when body grounding cannot be achieved.

  In order to achieve the above-described object of the present invention, a vehicle window antenna device according to the present invention includes an antenna element provided on a window and an amplifier circuit provided on the window, the hot terminal of the amplifier circuit being an antenna element. Connected to the amplifier circuit, provided in the window, connected to the ground terminal of the amplifier circuit, ground pattern, provided in the window, adjusted the impedance of the antenna element side as seen from the receiver side, ground pattern And an impedance adjustment unit comprising a pattern that does not flow current.

  Here, the impedance adjustment unit may be provided by a pattern branched from the vicinity of the connection position where the ground pattern is connected to the ground terminal of the amplifier circuit.

  The ground pattern may be connected to the ground of a defogger bus bar provided in the window.

  Further, the impedance adjustment unit may be further provided by a pattern branched from the vicinity of the connection position where the ground pattern is connected to the ground of the bus bar.

  The length of the impedance adjustment unit may be variable by changing the connection position where the ground pattern is connected to the ground of the bus bar.

  Furthermore, the second antenna element may be provided, and the impedance adjustment unit may adjust the impedance on the antenna element side as viewed from the receiver side using the pattern of the second antenna element.

  The vehicle window antenna device of the present invention does not require a matching circuit, and has the advantage that the antenna design and the cost of the device can be reduced because the impedance can be adjusted using the existing antenna pattern as it is. Further, it can be realized even when the body earth cannot be taken, and there is an advantage that there is little possibility of obstructing the field of view.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram for explaining a vehicle window antenna device according to a first embodiment of the present invention. As shown in the figure, the vehicle window antenna device of the present invention is mainly composed of an antenna element 10, an amplifier circuit 20, a ground pattern 30, and an impedance adjustment unit 40. A coaxial cable 2 connected to a radio receiver or the like (not shown) is connected to the connector incorporating the amplifier circuit 20.

  In the example of illustration, the antenna apparatus is shown in the rear window 1 of the vehicle. The rear window 1 is provided with a plurality of defogger heating wires 3, and bus bars 4, 4 ′ are connected to both ends thereof. The heating wire 3 generates heat by passing an electric current between the bus bars 4 and 4 ', and removes fogging of the window. For example, a positive voltage is supplied to the bus bar 4, and the bus bar 4 'is connected to the ground. In the figure, the area inside the broken line on the window 1 is an area that can be visually recognized by the driver, and the outside is an area hidden from the driver by a pillar, a vehicle body, or the like. The broken line region is not particularly limited to the illustrated example, and can be changed variously.

  In the vehicle window antenna apparatus of the illustrated example, the antenna element 10 includes an AM antenna element 11 and an FM antenna element 12. The antenna element 10 is made of a conductive wire. In the case of a glass antenna device, the antenna element 10 is embedded in glass. The vehicle window antenna device of the present invention is not limited to the antenna element embedded in the glass, and can be applied to a film antenna or the like attached on the glass. In the present invention, the element pattern and the frequency band of the antenna element are not limited to the illustrated example or the AM / FM band, and can be variously changed in consideration of the application and the arrangement position. As the antenna element, an existing element pattern can be used as it is. Of course, a new element pattern may be developed.

  An amplifier circuit 20 is provided on the window 1. The amplifier circuit 20 amplifies a signal received by the antenna element, and its hot terminal is connected to the antenna element 10. More specifically, since there are two antenna elements, the AM antenna element 11 and the FM antenna element 12 in the illustrated example, the AM antenna hot terminal 21 and the FM antenna hot terminal 22 are respectively connected to the AM antenna element 11. And FM antenna element 12.

  The window 1 is provided with a ground pattern 30 made of conductive lines. One end of the ground pattern 30 is connected to the ground terminal 23 of the amplifier circuit 20. In the vehicle window antenna apparatus according to the first embodiment of the illustrated example, the other end of the ground pattern 30 is connected to the body ground 38. The body ground 38 may be grounded by direct coupling to the metal body, or may be grounded by capacitive coupling. As with the antenna element, the ground pattern may be either embedded in the glass or affixed on the glass.

  In the vehicle window antenna device of the present invention, the window 1 is further provided with an impedance adjustment unit 40 extending from the ground pattern 30. The impedance adjusting unit 40 is made of a conductive wire, and adjusts the impedance on the antenna element side viewed from the receiver side. More specifically, the impedance adjusting unit 40 adjusts the impedance of the FM antenna element 12 in the illustrated example. The impedance adjustment unit 40 is a pattern extending from the ground pattern 30, but is a pattern in which no current flows because it is an open circuit. The impedance adjustment unit 40 is provided integrally with the ground pattern so as to be a ground pattern / impedance adjustment unit. In the vehicle window antenna device of the present invention, the impedance can be finely adjusted by adjusting the length of the impedance adjusting unit 40.

  In the vehicle window antenna device of the illustrated example, the impedance adjustment unit 40 is provided in a pattern that branches from the vicinity of the connection position where the ground pattern 30 is connected to the ground terminal 23 of the amplifier circuit 20. However, as long as the impedance adjustment unit extends from the ground pattern and does not flow current, the arrangement position and direction of the impedance adjustment unit are not limited to those illustrated.

  In the vehicle window antenna device of the present invention, it is possible to change the reception sensitivity characteristic of, for example, the FM antenna element by adjusting the length of the impedance adjustment unit having such a configuration. As a result, for example, it is possible to adjust the antenna device so that the average reception sensitivity in the FM band is improved, or to adjust the antenna device so that the minimum reception sensitivity has the highest characteristic. .

  The vehicle window antenna device of the first embodiment described above can be applied to a vehicle capable of taking a body ground, and the window on which the antenna device is installed is not limited to the rear window, but a front window or a side window. It may be installed in.

  Next, a vehicle window antenna device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic diagram for explaining a vehicle window antenna device according to a second embodiment of the present invention. In the figure, the portions denoted by the same reference numerals as those in FIG. Further, the coaxial cable shown in FIG. 1 has the same configuration and is not shown.

  Although the vehicle window antenna device of the first embodiment is applied to a vehicle that can be body grounded, the vehicle window antenna device of the second embodiment is a carbon that cannot be body grounded. This is an example applicable to a vehicle made of a fiber or resin body. The second embodiment is different from the first embodiment in that the ground pattern is body-grounded in the vehicle window antenna device of the first embodiment. However, in the vehicle window antenna device of the second embodiment, the ground pattern is Is connected to the ground of the bus bar for defogger provided in the window.

  As shown in FIG. 2, the ground pattern 31 of the vehicle window antenna device of the second embodiment is a ground of bus bars 4 and 4 ′ connected to both ends of the defogger heating wire 3, in the illustrated example, the bus bar 4 ′. Connected to the side. That is, since the bus bar 4 'is grounded, the antenna device is configured to be grounded using the bus bar 4'. Therefore, even if the vehicle cannot be grounded, if the bus bar for defogger is provided in the window, the vehicle window antenna device similar to the first embodiment is realized by connecting the ground pattern to the window. It becomes possible.

  Here, the structure around the amplifier circuit of the vehicle window antenna device of the present invention will be described more specifically. FIG. 3 is a schematic perspective view for explaining the structure around the amplifier circuit of the vehicle window antenna device of the present invention. In the figure, the portions denoted by the same reference numerals as those in FIG.

  As shown, the amplifier circuit 20 is built in the connector 25, and the coaxial cable 2 is connected to the amplifier circuit 20 through a hole provided in the connector 25. On the AM antenna hot terminal 21, the FM antenna hot terminal 22, and the ground terminal 23 on the window 1, a catcher 26 having holes at positions corresponding to these is provided. The catcher 26 is configured to fit with the connector 25. When the catcher 26 and the connector 25 are fitted, the antenna element 10 and the ground pattern 30 are electrically connected to the coaxial cable 2. The catcher 26 should just be comprised from the insulating material, for example, should just be fixed on the window 1 with an adhesive agent or a double-sided tape. This eliminates the need for soldering on the window 1. Accordingly, the vehicle window antenna device of the present invention can be installed even with a window material made of a material having a low heat resistance such as polycarbonate as well as glass.

Next, the reception sensitivity characteristic when the length of the impedance adjustment unit is changed in the vehicle window antenna device of the present invention thus configured will be described. FIG. 4 is a graph showing frequency vs. reception sensitivity characteristics when the length of the impedance adjustment unit is changed. The illustrated graph shows changes in frequency vs. FM reception sensitivity characteristics when the length L of the impedance adjustment unit is 580 mm, 480 mm, 430 mm, and 380 mm, respectively. The frequency band was the domestic FM radio band (76-90 MHz). The measured data of the illustrated graph is shown in Table 1 below.

  As can be seen from the illustrated graph and Table 1, when the length L of the impedance adjustment unit is shortened, the reception sensitivity increases at a low frequency, and the reception sensitivity decreases at a high frequency. Further, as the length L of the impedance adjustment unit is shortened, the average reception sensitivity in the band decreases, but conversely, the minimum reception sensitivity in the band increases.

  In the vehicle window antenna device of the present invention, the antenna characteristics are adjusted so as to have characteristics in accordance with the application and specifications by adjusting the length L of the impedance adjusting unit by utilizing such a change in characteristics. It is possible.

  For impedance adjustment, another impedance adjustment means may be provided in the vehicle window antenna device of the present invention. FIG. 5 is a schematic view for explaining an example in which another impedance adjusting means is provided in the vehicle window antenna device of the second embodiment of the present invention shown in FIG. In the figure, the portions denoted by the same reference numerals as those in FIG. Further, the coaxial cable shown in FIG. 1 has the same configuration and is not shown.

  In the vehicle window antenna device of the illustrated example, an impedance adjustment pattern 41 is provided from above the bus bar 4. On the heating wire 3, an inverted T-type impedance adjusting element 42 is provided.

  Further, the AM antenna element 11 ′ has a portion 43 in which the impedance is adjusted by shortening the length of a part of the pattern. That is, the impedance adjustment unit is configured to adjust the impedance using the pattern of the AM antenna element.

  Each of these impedance adjusting means has a pattern in which no current flows. The overall impedance on the antenna element side as viewed from the receiver side may be adjusted by variously applying such additional impedance adjusting means to the vehicle window antenna device of the present invention.

  Next, a vehicle window antenna device according to a third embodiment of the present invention will be described with reference to FIG. FIG. 6 is a schematic view for explaining a vehicle window antenna device according to a third embodiment of the present invention. In the figure, portions denoted by the same reference numerals as those in FIG. 1 and FIG. Further, the coaxial cable shown in FIG. 1 has the same configuration and is not shown.

  As shown in FIG. 6, the vehicle window antenna device according to the third embodiment is first from the vicinity of the connection position where one end of the ground pattern 31 is connected to the ground terminal 23 of the amplifier circuit 20 as in the second embodiment. It has the impedance adjustment part 40 which branches. The other end of the ground pattern 31 is connected to the ground 4 ′ of the bus bar, and another impedance adjusting unit 40 ′ is provided by a pattern branched from the vicinity of the connection position. That is, in the third embodiment of the present invention, the impedance adjusting unit 40 and the impedance adjusting unit 40 ′ are used as elements for adjusting the impedance.

  In the vehicle window antenna device according to the third embodiment of the present invention, when the reception sensitivity characteristic of the FM antenna element is changed, adjustment is made by the sum of the two lengths of the impedance adjustment unit 40 and the impedance adjustment unit 40 ′. Is possible. Here, when changing the length of the impedance adjustment unit, it is of course possible to increase or decrease the length of the end of the impedance adjustment unit on the side opposite to the ground pattern side. There may be a case where the length of the end opposite to the ground pattern side cannot be changed due to the arrangement restriction of the impedance adjusting unit. However, in the vehicle window antenna device according to the third embodiment of the present invention, by changing the length of the other impedance adjustment unit 40 ′ branched from the vicinity of the connection position where the ground pattern is connected to the ground of the bus bar, the impedance is changed. It is possible to vary the length of the entire adjustment unit.

  FIG. 7 is a graph showing frequency versus reception sensitivity characteristics when the length L2 of the impedance adjustment unit 40 ′ shown in FIG. 6 is changed. The illustrated graph shows a change in frequency vs. FM reception sensitivity characteristics when the length L2 of the impedance adjustment unit 40 ′ is 200 mm, 300 mm, 400 mm, and 450 mm, respectively. It is measured data when the length from the connection position where the ground pattern 31 is connected to the bus bar 4 ′ to the branch point is 10 mm, and the length from the branch point to the impedance adjustment unit 40 ′ is 10 mm. The length of the bus bar 4 ′ is about 400 mm.

  As can be seen from the graph in the figure, it can be seen that the sensitivity generally improves as the length L2 of the impedance adjustment section is increased. In particular, when L2 is longer than 400 mm, the sensitivity is remarkably improved.

  In the vehicle window antenna device of the present invention, the antenna characteristics are adjusted so as to have characteristics in accordance with the application and specifications by adjusting the length L2 of the other impedance adjusting unit by utilizing such a change in characteristics. Can be adjusted.

  Next, a vehicle window antenna device according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 8 is a schematic view for explaining a vehicle window antenna device according to a fourth embodiment of the present invention. In the figure, portions denoted by the same reference numerals as those in FIG. 1 and FIG. Further, the coaxial cable shown in FIG. 1 has the same configuration and is not shown.

  In the vehicle window antenna device according to the second embodiment of the present invention, an example in which the impedance adjustment unit is provided by a pattern branched from the vicinity of the connection position where the ground pattern is connected to the ground terminal of the amplifier circuit is shown. The vehicle window antenna device according to the fourth embodiment is an example in which the impedance adjustment unit further includes a pattern branched from the vicinity of the connection position where the ground pattern is connected to the ground of the bus bar.

  As shown in FIG. 8, the vehicle window antenna device of the fourth embodiment is first from the vicinity of the connection position where one end of the ground pattern 32 is connected to the ground terminal 23 of the amplifier circuit 20 as in the second embodiment. It has the impedance adjustment part 40 which branches. The other end of the ground pattern 32 is connected to the ground 4 ′ of the bus bar, and another impedance adjustment unit 40 ″ is provided by a pattern branched from the vicinity of the connection position. In the fourth embodiment, two elements, an impedance adjustment unit 40 and an impedance adjustment unit 40 ", are used as elements for adjusting the impedance. The impedance adjusting unit may be refracted as in the illustrated example, but the present invention is not limited to the pattern as in the illustrated example, and may be provided in a straight line as shown in FIG. good.

  In the second embodiment shown in FIG. 2, the example in which the amplifier circuit 20 is arranged in the upper part of the window 1 with the longitudinal direction being horizontal is shown. However, in the fourth embodiment shown in FIG. An example in which the longitudinal direction of the window 1 is arranged on the side of the window 1 is shown. However, the vehicle window antenna device according to the third embodiment of the present invention is not limited to such an arrangement, and has a pattern that branches from the vicinity of the connection position where the ground pattern is connected to the ground of the bus bar. The amplifier circuit 20 may be arranged in the same manner as in the second embodiment.

  In the vehicle window antenna device according to the fourth embodiment of the present invention, when the reception sensitivity characteristic of the FM antenna element is changed, adjustment is made by the sum of the two lengths of the impedance adjustment unit 40 and the impedance adjustment unit 40 ". Here, when changing the length of the impedance adjustment section, it is of course possible to lengthen or shorten the end of the impedance adjustment section opposite to the ground pattern side, There may be a case where the length of the end opposite to the ground pattern side cannot be changed due to the arrangement restriction of the impedance adjusting portion in the window region, etc. However, the vehicle window antenna according to the fourth embodiment of the present invention. In the device, the impedance is changed by changing the connection position where the ground pattern is connected to the ground of the bus bar. 8, for example, in the example shown in Fig. 8, the connection position 34 where the ground pattern 32 is connected to the ground 4 'of the bus bar is the position of the ground 4' of the bus bar. Although it is connected to the lower end, when this connection position is moved to a connection position 34 'above the lower end, for example, the length of the impedance adjustment unit 40 "becomes longer. For this reason, the total of the two lengths of the impedance adjustment unit 40 and the impedance adjustment unit 40 "becomes longer.

  Therefore, by changing the connection position where the ground pattern is connected from the lower end to the upper end of the ground of the bus bar without changing the length of the end opposite to the ground pattern side of the impedance adjustment unit, the impedance is adjusted. It is possible to adjust the length of the adjustment unit. In other words, the length of the impedance adjustment unit can be adjusted by the length of the bus bar without changing the length of the end of the impedance adjustment unit opposite to the ground pattern side. As a result, impedance adjustment is possible by variously selecting the connection position where the ground pattern is connected to the ground of the bus bar, such as the lower end, upper end, and center of the bus bar, depending on the application, specifications, or layout space. Is possible.

  As described above, in the vehicle window antenna device of the present invention, the existing antenna pattern can be used as it is, and the impedance adjustment can be performed by using the impedance adjustment unit extending from the ground pattern. There is an advantage that can be achieved. In addition, even when body grounding cannot be achieved, grounding is possible by using a bus bar, and there is also an advantage that there is little possibility of obstructing the field of view by the impedance adjustment unit.

  Note that the vehicle window antenna device of the present invention is not limited to the illustrated example described above, and various modifications can be made without departing from the scope of the present invention. For example, the other impedance adjusting means shown in FIG. 5 can be used in combination with the vehicle window antenna device shown in FIG. 1, FIG. 6, FIG. Also, the dimensions and frequency characteristics used in the illustrated examples and description are merely examples, and the present invention is not limited to these specific dimensions and frequency characteristics.

FIG. 1 is a schematic diagram for explaining a vehicle window antenna device according to a first embodiment of the present invention. FIG. 2 is a schematic diagram for explaining a vehicle window antenna device according to a second embodiment of the present invention. FIG. 3 is a schematic perspective view for explaining the structure around the amplifier circuit of the vehicle window antenna device of the present invention. FIG. 4 is a graph showing frequency vs. reception sensitivity characteristics when the length of the impedance adjustment unit is changed. FIG. 5 is a schematic view for explaining an example in which another impedance adjusting means is provided in the vehicle window antenna device of the second embodiment of the present invention shown in FIG. FIG. 6 is a schematic view for explaining a vehicle window antenna device according to a third embodiment of the present invention. FIG. 7 is a graph showing frequency vs. reception sensitivity characteristics when the length of the impedance adjustment unit is changed. FIG. 8 is a schematic view for explaining a vehicle window antenna device according to a fourth embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Window 2 Coaxial cable 3 Heating wire 4, 4 'Bus bar 10 Antenna element 11 AM antenna element 12 FM antenna element 20 Amplifier circuit 21 AM antenna hot terminal 22 FM antenna hot terminal 23 Ground terminal 25 Connector 26 Catcher 30, 31, 32 Ground Pattern 40, 40 ', 40 "impedance adjuster

Claims (6)

A vehicle window antenna device comprising:
An antenna element provided in the window;
An amplifier circuit provided on a window, the amplifier circuit having a hot terminal of the amplifier circuit connected to the antenna element;
A ground pattern provided in a window and connected to a ground terminal of the amplifier circuit;
An impedance adjustment unit that is provided in a window, adjusts the impedance of the antenna element side as viewed from the receiver side, and includes a pattern that does not flow current extending from the ground pattern;
An antenna device for a vehicle window, comprising:   2. The vehicle window antenna device according to claim 1, wherein the impedance adjustment unit is provided by a pattern branched from a vicinity of a connection position where the ground pattern is connected to a ground terminal of the amplifier circuit. 3. Window antenna device.   3. The vehicle window antenna device according to claim 1, wherein the ground pattern is connected to a ground of a defogger bus bar provided in the window.   4. The vehicle window antenna device according to claim 3, wherein the impedance adjustment unit is further provided by a pattern branched from the vicinity of a connection position where the ground pattern is connected to the ground of a bus bar. Antenna device.   5. The vehicle window antenna device according to claim 4, wherein the impedance adjustment unit is variable in length by changing a connection position where the ground pattern is connected to a ground of a bus bar. Window antenna device.   6. The vehicle window antenna device according to claim 1, further comprising a second antenna element, wherein the impedance adjustment unit also uses a pattern of the second antenna element. An antenna device for a vehicle window, wherein the impedance on the antenna element side as viewed from the side is adjusted.