JP5402149B2 - Vehicle receiving antenna device - Google Patents

Description

  The present invention relates to a receiving antenna device that is mounted on a vehicle and receives a transmission radio wave of a predetermined frequency, and belongs to the field of wireless communication technology for vehicles.

  Conventionally, a so-called keyless entry system that opens and closes a door or starts and stops an engine via wireless communication is known. Such a keyless entry system includes a transmission-side device that is carried and operated by a passenger, and a reception-side device that is mounted on a vehicle and receives a transmission radio wave having a predetermined frequency from the transmission device. .

  Further, the receiving side device of such a keyless entry system is a receiving antenna device in which an antenna and a receiving circuit board are integrated for miniaturization, like the keyless entry system described in Patent Document 1. It is configured. The receiving antenna device of Patent Document 1 includes a substrate having a ground portion formed on the surface, a grounding member for grounding the ground portion to the vehicle body, a feeding point provided on a surface portion of the substrate in the vicinity of the ground portion, and antenna feeding. The distance from the ground point connected to the vehicle body by the ground member of the ground portion to the feed point is set to 1/30 or less of the wavelength of the received radio wave.

Japanese Patent No. 3777785

  However, since the receiving antenna device as described above is downsized because it needs to be mounted on a vehicle, it is often impossible to secure a sufficient antenna length for the received radio wave. For example, when a radio wave having a frequency of about 300 MHz is used, the ideal antenna length is about 24 cm, which is 1/4 of the wavelength, but is actually shorter than this length. Therefore, the effective range of the keyless entry system (operation range by the transmission device) is narrowly limited, and the received signals are also limited to several types of operation signals such as opening and closing of the door and starting and stopping of the engine.

  Therefore, the present invention provides a receiving antenna device having a structure that can secure a sufficient antenna length and obtain a high receiving capability without increasing the size in a receiving antenna device of a vehicle that receives a transmission radio wave of a predetermined frequency. The issue is to provide.

In order to solve the above-described problem, the invention according to claim 1 is a receiving antenna device for a vehicle that is mounted on a vehicle and receives a transmission radio wave of a predetermined wavelength,
A substrate having a ground portion formed on the surface;
A grounding member for electrically connecting the ground portion to a vehicle body having a ground potential;
An antenna element erected from a feeding point provided on the surface portion of the substrate in the vicinity of the ground portion;
The distance between the grounding point connected to the vehicle body by the grounding member of the ground part and the feeding point is longer than 1/30 of the predetermined wavelength.

According to a second aspect of the present invention, in the vehicle receiving antenna apparatus according to the first aspect,
The antenna element is composed of a straight vertical portion extending perpendicularly from the feeding point, and a straight horizontal portion extending parallel to the surface of the substrate from the tip of the vertical portion,
The antenna element is formed so that a straight line connecting the feeding point and the grounding point and a horizontal portion of the antenna element are non-parallel in a plan view of the substrate.

Further, the invention according to claim 3 is the vehicle receiving antenna device according to claim 1,
The antenna element is composed of a straight vertical portion extending perpendicularly from the feeding point, and a horizontal portion extending in a polygonal line on a plane parallel to the surface of the substrate from the tip of the vertical portion,
In the path from the tip of the horizontal part of the antenna element to the grounding point through the feeding point, the horizontal part has a portion that is in the same direction as the part from the feeding point to the grounding point. .

Furthermore, the invention according to claim 4 is the vehicle receiving antenna device according to claim 3,
The horizontal portion of the antenna element is developed beyond a range occupied by the ground portion in plan view.

In addition, the invention according to claim 5 is the vehicle receiving antenna device according to any one of claims 1 to 4,
A connector provided on the ground portion and connected to another electronic component;
The distance from the feeding point to the ground point is shorter than the distance from the feeding point to the connector.

In addition, the invention according to claim 6 is the vehicle receiving antenna device according to claim 1,
The ground portion is formed as a ground portion for an antenna in which other electronic components are not electrically connected.

In addition, the invention according to claim 7 is the vehicle receiving antenna device according to claim 6,
The antenna element is composed of a straight vertical portion extending perpendicularly from the feeding point, and a horizontal portion extending in a polygonal line on a plane parallel to the surface of the substrate from the tip of the vertical portion,
The ground portion is formed in a polygonal line shape having a portion overlapping a part of the horizontal portion of the antenna element in plan view,
In the path from the front end of the horizontal portion of the antenna element to the ground point of the ground portion through the feeding point, the antenna element and the ground portion are formed to have a common direction portion. .

In addition, the invention according to claim 8 is the vehicle receiving antenna device according to claim 6 or 7,
The substrate comprises a multilayer substrate;
Another ground part electrically connected to another electronic component is formed in a layer different from the ground part.

  According to the first aspect of the present invention, the substrate having the ground portion formed on the surface, the grounding member for electrically connecting the ground portion to the vehicle body having the ground potential, and the surface portion of the substrate in the vicinity of the ground portion are provided. The receiving antenna device is configured by an antenna element standing from the feeding point, and the distance between the grounding point connected to the vehicle body by the grounding member of the ground portion and the feeding point is 1/30 of the predetermined wavelength. Made longer. Thereby, the portion of the ground portion from the vicinity of the feeding point to the ground point can function as a pseudo antenna, and a sufficient antenna length can be ensured. As a result, it is possible to obtain a high receiving capability without lengthening the antenna element, that is, without increasing the size of the receiving antenna device itself.

  According to the invention of claim 2, the antenna element includes a straight vertical portion extending perpendicularly from the feeding point and a straight horizontal portion extending parallel to the surface of the substrate from the tip of the vertical portion. Composed. Further, the antenna element is formed such that the straight line connecting the feeding point and the ground point and the horizontal portion of the antenna element are non-parallel in plan view of the substrate. As a result, the receiving antenna device can obtain a higher receiving capability than when the horizontal portion of the antenna element is parallel to a straight line connecting the feeding point and the grounding point in plan view of the substrate. The reason is that when the horizontal part of the antenna element and the straight line connecting the feed point and the ground point are parallel, the direction of the current flowing in the horizontal part is opposite to the direction of the current flowing between the feed point and the ground point. As a result, the electric field formed in each serves to weaken the other current.

  Furthermore, according to the invention described in claim 3, the antenna element develops in a straight line-shaped vertical portion extending perpendicularly from the feeding point and a polygonal line from the tip of the vertical portion on a plane parallel to the surface of the substrate. It consists of a horizontal part. In the path from the tip of the horizontal part of the antenna element to the ground point through the feeding point, the horizontal part has a portion that is in the same direction as the portion from the feeding point to the ground point. This provides a horizontal portion of the antenna element in which the current flows in the same direction as the current flowing between the feed point and the ground point, whereby the electric field formed in each part intensifies the other current. Work. As a result, the receiving antenna device can obtain a higher receiving capability.

Furthermore, according to claim 4, the horizontal portion of the antenna element is expanded beyond the range occupied by the ground portion in plan view. Thereby, a portion of the horizontal portion of the antenna element that exceeds the range occupied by the ground portion in plan view is not greatly affected by the electric field formed in the ground portion, and a stable current flows. As a result, the receiving antenna device can obtain a high receiving capability.

  In addition, according to the invention described in claim 5, when the connector is provided on the ground portion and is connected to another electronic component, the distance from the feeding point to the grounding point is from the feeding point to the connector. It is shorter than the distance. Thereby, the portion of the ground portion from the vicinity of the feeding point to the ground point can be made to function stably as an antenna without being affected by the electronic components connected to the connector. Further, the current flowing from the vicinity of the feeding point to the ground point by receiving the radio wave is suppressed from flowing to the connector.

  In addition, according to the invention described in claim 6, the ground portion is formed as a ground portion for an antenna in which other electronic components are not electrically connected. Thereby, since it is not influenced by other electronic components, the receiving antenna apparatus can obtain the stable high receiving capability.

  In addition, according to the invention described in claim 7, the antenna element has a straight vertical portion extending perpendicularly from the feeding point, and a polygonal line from the tip of the vertical portion on a plane parallel to the surface of the substrate. It consists of a horizontal part that unfolds. Further, the ground portion is formed in a polygonal line shape having a portion overlapping with a part of the horizontal portion of the antenna element in plan view. And in the path | route from the front-end | tip of the horizontal part of an antenna element to a grounding point of a ground part through a feeding point, this antenna element and a ground part are formed so that it may have a part of a common direction. As a result, currents in the same direction flow in portions in the common direction of the horizontal portion and the ground portion of the antenna element, whereby the electric field formed in each of the antenna elements functions to increase the other current. As a result, the receiving antenna device can obtain a higher receiving capability.

  In addition, according to the invention described in claim 8, the substrate is formed of a multilayer substrate, and the other ground portion electrically connected to other electronic components is in a layer different from the ground portion for the antenna. It is formed. As a result, the board area is reduced as compared with the case where another ground part electrically connected to another electronic component is formed on one surface together with the antenna ground part. As a result, an increase in size of the receiving antenna device is suppressed.

It is the schematic of the receiving antenna apparatus of the vehicle which concerns on the 1st Embodiment of this invention. 1 is a schematic cross-sectional view of a receiving antenna device for a vehicle according to a first embodiment of the present invention. . It is a figure which shows the relationship between the distance L from a feeding point to a ground point, a frequency, and VSWR. It is a figure which shows the relationship between the angle (theta) which the horizontal part of the antenna element by planar view, and the straight line which connects a feeding point and a grounding point, a frequency, and VSWR. It is the schematic of the receiving antenna apparatus of the vehicle which concerns on the 2nd Embodiment of this invention. It is the schematic of the receiving antenna apparatus of the vehicle which concerns on the 3rd Embodiment of this invention. It is the schematic of the receiving antenna apparatus of the vehicle which concerns on the 4th Embodiment of this invention. It is the schematic of the receiving antenna apparatus of the vehicle which concerns on the 5th Embodiment of this invention. It is the schematic of the receiving antenna apparatus of the vehicle which concerns on the 6th Embodiment of this invention.

  Embodiments of the present invention will be described below.

(First embodiment)
FIG. 1 schematically shows a receiving antenna device for a vehicle according to a first embodiment of the present invention. Further, FIG. 2 schematically shows a cross-sectional view for explaining a method of grounding the vehicle body.

  As shown in FIG. 1, the receiving antenna device 10 includes a substrate 14 having a ground pattern 12 formed on the surface thereof, a ground screw 16 that electrically connects the ground pattern 12 to a vehicle body having a ground potential, and a portion near the ground pattern 12. And an antenna element 20 erected from a feeding point 18 provided on the surface portion of the substrate 14. The ground pattern 12 is electrically connected to a connector 22 for connecting to other electronic components.

  As shown in FIG. 2, the ground screw 16 is inserted into a through hole 26 that electrically connects the ground pattern 12 on the front surface and the ground pattern 24 formed on the back surface, and the tip thereof is made of metal of the receiving antenna device 10. The lower cover 28 is screwed. The lower cover 28 is connected to the vehicle body 32 via a metal grommet 30. As a result, the ground pattern 12 on the surface of the substrate 14 is electrically connected (grounded) to the vehicle body 32. In this case, the head of the ground screw 16 becomes the ground point 34 of the ground pattern 12. The reason why the metal grommet 30 is used as a method of electrically connecting the receiving antenna device 10 and the vehicle body 32 is to facilitate the mounting of the vehicle body 32 of the device 10.

  The feeding point 18 of the antenna element 20 is provided at a position where the distance L to the ground point 34 is longer than 1/30 of the wavelength of the received radio wave.

  Explaining this reason, as shown in FIG. 3, in the frequency band of about 280 to 340 MHz used in the keyless entry system, the distance L from the feed point 18 to the ground point 34 is 1 of the wavelength λ of the received radio wave. This is because the longer than / 30, the lower the VSWR (voltage standing wave ratio), and the higher the receiving capability of the receiving antenna device.

  This is because the distance L from the feeding point 18 to the ground point 34 is made longer than 1/30 of the wavelength λ of the received radio wave, so that the portion of the ground pattern 12 from the feeding point 18 to the ground point 34 becomes a pseudo antenna. Since it functions, this makes it possible to obtain a length equal to or greater than the length of the actual antenna element 20 as the antenna length of the receiving antenna device 10 (the apparent antenna length is longer than that of the antenna element 20). .

  Further, the distance L from the feeding point 18 to the ground point 34 is shorter than the distance from the feeding point 18 to the connector 22 (from another viewpoint, the connector 22 is smaller than the ground point 34. It is provided so as to be away from the feeding point 18). Accordingly, the portion of the ground pattern 12 from the vicinity of the feeding point 18 to the ground point 34 can be made to function stably as an antenna without being affected by the electronic components connected to the connector 22. Further, the current flowing from the vicinity of the feeding point 18 to the ground point 34 by receiving the radio wave is suppressed from flowing to the connector 22.

  As shown in FIG. 1, the antenna element 20 has an inverted L shape, a straight vertical portion 40 extending perpendicularly from the feeding point 18, and extending parallel to the surface of the substrate 14 from the tip of the vertical portion 40. It is comprised from the horizontal part 42 of a straight line shape. Further, the horizontal portion 42 of the antenna element 20 has a plan view (viewed from above the surface of the substrate 12) so that an angle θ formed with a straight line connecting the feeding point 18 and the grounding point 34 does not become 0 ° (here 90 °), that is, it extends so as not to be parallel to the straight line.

  To explain this reason, as shown in FIG. 4, in the frequency band of about 280 to 340 MHz used in the keyless entry system, the angle θ is less than 0 ° (rather than parallel). This is because VSWR (voltage standing wave ratio) is low when the angle is not 0 ° (non-parallel), and reception capability is high as a reception antenna device.

  This is because, when the angle θ is 0 ° (in parallel), the direction of the current flowing through the horizontal portion 42 of the antenna element 20 is between the feeding point 18 and the ground point 34 when receiving radio waves. This is because, as a result, the electric field formed in each of them acts to weaken the other current. Therefore, the receiving direction of the receiving antenna device 10 is weakened by setting the extending direction of the horizontal portion 42 of the antenna element 20 so that the angle θ does not become 0 °, for example, 90 ° as shown in FIG. (Receiving ability is improved.)

  According to the present embodiment, it is possible to obtain a high receiving capability without making the antenna element 20 long, that is, without increasing the size of the receiving antenna device 10 itself.

From here, the development of the first embodiment will be described.
(Second Embodiment)
This embodiment is different from the first embodiment in the shape of the antenna element. Therefore, here, the antenna element will be described.

  As shown in FIG. 5, the antenna element 120 of the present embodiment includes a straight vertical portion 140 extending vertically from the feeding point 118, and a polygonal line shape on a plane parallel to the surface of the substrate 114 from the tip of the vertical portion 140. It is comprised from the horizontal part 142 which expand | deploys.

  Specifically, the horizontal portion 142 of the antenna element 120 includes, in plan view, a portion 142a extending from the tip of the vertical portion 140, a portion 142b extending in the 90 ° right direction from the tip of the 142a, and a right from the tip of the 142b. A portion 142c extending in the 90 ° direction and a portion 142d extending in the right 90 ° direction from the tip of the harm 142c and parallel to a straight line connecting the feeding point 118 and the ground point 134 are formed.

  A portion 142d of the horizontal portion 142 of the antenna element 120 is parallel to a straight line connecting the feeding point 118 and the ground point 134, but unlike the first embodiment, a dotted arrow indicating a current flow direction during radio wave reception. As shown in FIG. 5, since the directions of the flowing currents are the same, the electric field formed in each of them does not weaken the other current and works to strengthen the other. Thereby, the receiving antenna device can obtain a higher receiving capability.

(Third embodiment)
This embodiment is an improved example of the second embodiment, and is different in the size of the substrate, strictly speaking, the size of the ground pattern.

  In the second embodiment, as shown in FIG. 5, the horizontal portion 142 of the antenna element 120 is developed on the ground pattern 112. In other words, the antenna element 120 is developed within a range occupied by the ground pattern 112 in plan view. ing.

  On the other hand, as shown in FIG. 6, the horizontal portion 242 of the antenna element 220 of the present embodiment has portions 242b and 242c completely outside the range occupied by the ground pattern 212 in plan view, and the remaining portion 242a. 242d partially exceeds the range.

  Thus, the portion of the horizontal portion 242 of the antenna element 220 that exceeds the range occupied by the ground pattern 212 in plan view is not greatly affected by the electric field formed on the ground pattern 212 (the horizontal portion 242 is within the range). Compared to the case where there is a stable current). As a result, the receiving antenna device can obtain a higher receiving capability.

(Fourth embodiment)
In the embodiments so far, a ground pattern to which other electronic components are electrically connected is also used for receiving radio waves. Therefore, the reception capability may not be stabilized due to the influence of electronic components. The present embodiment addresses this.

  As shown in FIG. 7, in this embodiment, a ground pattern 312 in which other electronic components are connected to the surface of the substrate 314 via a connector 322, and an antenna ground pattern in which no other electronic components are electrically connected. 312 'is formed. The ground pattern 312 is provided with a ground point 334, and the antenna ground pattern 312 ′ is provided with a ground point 334 ′. In addition, a feeding point 318 is provided in the vicinity of the antenna ground pattern 312 ′.

  Thus, since no other electrical component is electrically connected to the antenna ground pattern 312 ′, it is not affected by the electronic component. Thereby, the receiving antenna device can obtain a stable high receiving capability.

(Fifth embodiment)
This embodiment has an antenna ground pattern as in the fourth embodiment, and can obtain a high reception capability.

  As shown in FIG. 8, the antenna element 420 is an antenna element similar to that of the second and third embodiments (see FIGS. 5 and 6), and has a straight vertical portion 440 extending vertically from the feeding point 418. , And a horizontal portion 442 that expands in a polygonal line on a plane parallel to the surface of the substrate 414 from the tip of the vertical portion 440.

  The horizontal portion 442 of the antenna element 420 has a portion 442a extending from the tip of the vertical portion 440, a portion 442b extending in the 90 ° right direction from the tip of the 442a, and a right 90 ° direction from the tip of the 442b in plan view. A portion 442c and a portion 442d extending rightward by 90 ° from the tip of the 442c.

  The antenna ground pattern 412 ′ is also formed in a polygonal line shape on the surface of the substrate 414.

  The antenna ground pattern 412 ′ extends from the vicinity of the feeding point 418 in a plan view, and overlaps with the portion 442 d of the horizontal portion 442 of the antenna element 424, and extends to the left 90 ° from the tip of the portion 412 a ′. A portion 412b ′ that overlaps the portion 442c of the horizontal portion 442 of the antenna element 424, and a portion 442b that extends from the tip of the portion 412a ′ toward the ground point 434 ′ in the 90 ° left direction and overlaps the portion 442b of the horizontal portion 442 of the antenna element 424. The portion 412c ′ is formed.

  As indicated by the dotted arrows indicating the direction of current flow during radio wave reception, the direction of current flowing in the portion 442d of the horizontal portion 442 of the antenna element 424 and the portion 412a ′ of the ground pattern 412 ′ are the same, so One electric field works to strengthen the other current. In addition, since the direction of the current flowing through the portion 442c of the horizontal portion 442 of the antenna element 424 and the portion 412b 'of the ground pattern 412' is the same, the electric field formed in each acts to intensify the other current. Furthermore, since the direction of the current flowing in the portion 442b of the horizontal portion 442 of the antenna element 424 and the portion 412c 'of the ground pattern 412' is the same, the electric field formed in each acts to intensify the other current. As a result, the current flowing through the antenna element 424 and the ground pattern 412 'is enhanced as a whole. As a result, the receiving antenna device can obtain a higher receiving capability.

(Sixth embodiment)
This embodiment is an improved example of the fifth embodiment.

  In the case of the fifth embodiment, as shown in FIG. 8, since the antenna ground pattern 412 ′ is formed on the surface of the substrate 414 in a polygonal line shape, a large-area ground pattern for other electronic components is formed. Hard to form. If the substrate area is increased for the purpose of formation, the receiving antenna device is increased in size.

  As a countermeasure, the substrate of the receiving antenna device according to the present embodiment is composed of a multilayer substrate. In the figure, the substrate is composed of four layers, the ground pattern 512 ′ for the antenna element 520 is formed on the layer 514a on the resurface side, and the lowermost layer 514d is formed as a ground layer to which other electronic components are electrically connected. Has been.

  As a result, the board area is reduced as compared with the case where the ground pattern in which other electronic components are electrically connected and the ground pattern for the antenna are formed on one surface. As a result, an increase in size of the receiving antenna device is suppressed.

  As described above, according to the present invention, a sufficient antenna length can be secured without increasing the size of a receiving antenna device for a vehicle that receives radio waves of a predetermined frequency, and high receiving ability can be obtained. Therefore, it may be suitably used in the field of vehicle wireless communication.

12 Ground part (Ground pattern)
14 Substrate 16 Grounding member (Ground screw)
18 Feeding point 20 Antenna element 28 Grounding member (lower cover)
30 Grounding member (grommet)
32 Car body 34 Grounding point

Claims (8)

A receiving antenna device for a vehicle that is mounted on a vehicle and receives a transmission radio wave of a predetermined wavelength,
A substrate having a ground portion formed on the surface;
A grounding member for electrically connecting the ground portion to a vehicle body having a ground potential;
An antenna element erected from a feeding point provided on the surface portion of the substrate in the vicinity of the ground portion;
A receiving antenna device for a vehicle, wherein a distance between a grounding point connected to a vehicle body by the grounding member of the ground part and the feeding point is longer than 1/30 of the predetermined wavelength . The receiving antenna device for a vehicle according to claim 1,
The antenna element is composed of a straight vertical portion extending perpendicularly from the feeding point, and a straight horizontal portion extending parallel to the surface of the substrate from the tip of the vertical portion,
A vehicle in which the antenna element is formed so that a straight line connecting the feeding point and the grounding point and a horizontal portion of the antenna element are non-parallel in a plan view of the substrate. Receiving antenna device. The receiving antenna device for a vehicle according to claim 1,
The antenna element is composed of a straight vertical portion extending perpendicularly from the feeding point, and a horizontal portion extending in a polygonal line on a plane parallel to the surface of the substrate from the tip of the vertical portion,
In the path from the tip of the horizontal part of the antenna element to the grounding point through the feeding point, the horizontal part has a portion that is in the same direction as the part from the feeding point to the grounding point. A receiving antenna device for a vehicle. The receiving antenna device for a vehicle according to claim 3,
The receiving antenna device for a vehicle according to claim 1, wherein the horizontal portion of the antenna element is expanded beyond a range occupied by the ground portion in plan view. The receiving antenna device for a vehicle according to any one of claims 1 to 4,
A connector provided on the ground portion and connected to another electronic component;
A receiving antenna device for a vehicle, wherein a distance from the feeding point to the grounding point is shorter than a distance from the feeding point to the connector. The receiving antenna device for a vehicle according to claim 1,
A receiving antenna device for a vehicle, wherein the ground portion is formed as a ground portion for an antenna in which other electronic components are not electrically connected. The receiving antenna device for a vehicle according to claim 6,
The antenna element is composed of a straight vertical portion extending perpendicularly from the feeding point, and a horizontal portion extending in a polygonal line on a plane parallel to the surface of the substrate from the tip of the vertical portion,
The ground portion is formed in a polygonal line shape having a portion overlapping a part of the horizontal portion of the antenna element in plan view,
In the path from the front end of the horizontal portion of the antenna element to the ground point of the ground portion through the feeding point, the antenna element and the ground portion are formed to have a common direction portion. A receiving antenna device for a vehicle. The receiving antenna device for a vehicle according to claim 6 or 7,
The substrate comprises a multilayer substrate;
A receiving antenna device for a vehicle, wherein another ground part electrically connected to another electronic component is formed in a layer different from the ground part.

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