JPH10276028A - Antenna unit for car navigation system - Google Patents

Abstract

(57) Abstract: The present invention relates to an antenna unit of a car navigation device installed in a vehicle compartment, and it is possible to receive radio waves from a GPS satellite in a wide range when the antenna unit is placed indoors. The task is to A car navigation system includes a planar antenna element for receiving a radio wave from a GPS satellite on a radio wave receiving surface, and a case for enclosing the planar antenna element. In the antenna unit, the plane antenna element 2 is disposed on a triangular case 21 when viewed from the side so as to correspond to the direction in which the radio wave enters the vehicle interior.
2, the elevation angle θ4 of the radio wave receiving surface 26 of the planar antenna element 22 is set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna unit for a car navigation system, and more particularly to an antenna unit for a car navigation system installed in a vehicle.

[0002]

2. Description of the Related Art In recent years, car navigation systems (GP)
S: Global Positioning System) is attracting attention and is being mounted on vehicles. This GP
S is configured to receive a radio wave from a GPS satellite and detect the current position of the vehicle. For this reason, a GPS-equipped vehicle is provided with a GPS antenna unit.

FIG. 6 shows an example of a conventional antenna unit 10 for GPS. The antenna unit 10 includes an aluminum die-cast bottom cover 1,
A circuit board 3 on which electronic components are mounted, a metal shield cover 3a covering the circuit board 3, and a geostationary satellite (GPS satellite) are provided in a case constituted by a top cover 2 attached to this. The flat antenna element 4 and the like for receiving radio waves from the above are housed.

[0004] The planar antenna element 4 has a radio wave receiving surface 4a on the upper surface thereof.
As shown in FIG. The planar antenna element 4 is configured so that its receiving surface is horizontal when it is mounted in the covers 1 and 2. The signal received by the planar antenna element 4 is processed by the circuit board 3,
It is configured to be transmitted to the PS computer.

A concave portion is formed on the bottom surface of the bottom cover 1, and a ferromagnetic back yoke 7 fixed with a plurality of mounting screws 6 via a mounting piece 7a is provided in the concave portion. . A ring-shaped magnet 8 is adsorbed and held on the lower surface side of the back yoke 7.
The antenna unit 10 is configured to be sucked and held at the installation location by the magnetic force. Reference numeral 9 denotes a stable shield plate made of sheet metal for stabilizing a reception state.

Meanwhile, as a place for disposing the antenna unit 10 having the above configuration, for example, as shown in FIG. 8, a roof 13 (outdoor) of a vehicle 12 can be considered. Thus, in the configuration in which the roof 13 is disposed on the antenna unit 10, since the antenna unit 10 is disposed outside the vehicle, it is possible to receive radio waves from GPS satellites in a favorable state.

[0007]

However, in a configuration in which the antenna unit 10 is disposed outside the vehicle, there is a possibility that the antenna unit 10 is misplaced or stolen. To prevent this, as shown in FIG.
It is necessary to arrange the antenna unit 10 in the room 14 of the vehicle 12.

[0008] In addition, as an arrangement position in the interior 14 of the vehicle, it is common to select a position on the dashboard 15 which can widely receive radio waves. As described above, the antenna unit 10 is connected to the dashboard 15 (inside the vehicle 14).
, There is no danger of mischief and theft. However, when the antenna unit 10 is disposed inside the vehicle 14, there are various components around the antenna unit 10 that block radio waves from GPS satellites as compared to the configuration where the antenna unit 10 is disposed outside the vehicle. Becomes Specifically, the radio waves from the GPS satellites are weakened by the front pillar 16 and the center pillar 17 shown in FIG. 9, so that the reception sensitivity of the radio waves from the GPS satellites is reduced in the vehicle 14.

On the other hand, in the conventional antenna unit 10, the shape of the radio wave receiving surface 4a of the planar antenna element 4 is square, so that the length Lx in the X direction and the length Ly in the Y direction in FIG. (Lx = Ly).
Here, focusing on the directivity of the planar antenna element 4 having this configuration, it is known that the directivity of the planar antenna element 4 is correlated with the length of the radio wave receiving surface 4a in the X and Y directions. Therefore, the length L in the X direction of the radio wave receiving surface 4a
By changing the length Ly in the x and Y directions, the directional characteristics of the planar antenna element 4 can be changed.

However, as described above, in the conventional antenna unit 10, no consideration is given to the receivable range in the room 14, so that the length Lx in the X direction is the same as the antenna unit 10 arranged outside the vehicle. The length Ly in the Y direction is set to be equal. For this reason, in the conventional antenna unit 10, in the direction (X direction; see FIG. 9) facing the windshield 18, the windshield 18 allows radio waves to pass, so that radio waves from GPS satellites can be received well. However, the direction (Y) facing the front pillar 16, the center pillar 17 and the like described above.
direction. In FIG. 9), the front pillar 16
In addition, since the radio waves from the GPS satellites are weakened by the center pillar 17 and the like, there has been a problem that the receiving sensitivity is reduced and good reception cannot be performed. It is desirable that the reception sensitivity is uniform in all directions with respect to the planar antenna element 4.

The present invention has been made in view of the above points, and provides an antenna unit of a car navigation device capable of obtaining uniform reception sensitivity in all reception directions even when placed indoors. The purpose is to:

[0012]

Means for Solving the Problems In order to solve the above problems, the present invention is characterized by taking the following means. According to the first aspect of the present invention, there is provided an antenna unit of a car navigation device, which is configured by a planar antenna element that receives a radio wave from a satellite on a receiving surface and a case that encloses the antenna element, and is disposed in a vehicle interior. Assuming XY coordinates orthogonal to the planar antenna element, the planar antenna element is configured to have different characteristics between directivity in the X direction and directivity in the Y axis direction, and The planar antenna element is arranged so as to face a side portion of a vehicle compartment.

According to a second aspect of the present invention, in the antenna unit of the car navigation device according to the first aspect, the planar antenna element is formed in a rectangular shape in a plan view, so that the directivity in the X direction is provided. And the directivity in the Y-axis direction is different.

Each of the above means operates as follows. According to the first aspect of the present invention, assuming orthogonal XY coordinates on the planar antenna element, the planar antenna element is configured to have different characteristics in directivity in the X direction and directivity in the Y axis direction. Thereby, the reception sensitivity of radio waves in a specific direction can be improved.

[0015] A flat antenna element is disposed on a side of a vehicle compartment in which components for weakening radio waves from satellites such as a front pillar and a center pillar are disposed so as to face a high directivity direction. It is possible to obtain the same reception sensitivity as in the front-back direction even in the side direction of the room. As a result, uniform reception sensitivity can be obtained in all reception directions, and the reception probability is improved, so that good car navigation processing can be performed regardless of the direction in the vehicle compartment.

According to the second aspect of the present invention, the planar antenna element is formed in a rectangular shape in a plan view, thereby making the directivity in the X direction different from the directivity in the Y axis direction. Antenna units having different directivity characteristics can be easily realized with a simple configuration.

[0017]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows an antenna unit 20 of a car navigation device according to one embodiment of the present invention. The antenna unit 20 generally includes a planar antenna element 21, a circuit board 22, a bottom case 23, an upper case 24, and the like. The antenna unit 20 is disposed inside the vehicle 30 as described later in detail, and has a function of receiving a radio wave transmitted from a GPS satellite.

The planar antenna element 21 is different from FIG.
As shown in FIG. 3, a radio wave receiving surface 21b is formed by forming a conductive thin film made of a conductive material such as a metal on a substrate 21a made of a dielectric material such as a dielectric ceramic. The radio wave receiving surface 21b is electrically connected to the outside via pins 21c. FIG.
As shown in (B), the pin 21c is inserted into a through hole 21d formed in the substrate 21a, the upper end thereof is soldered to the radio wave receiving surface 21b, and the lower end protrudes from the substrate 21a. Have been. A circuit board 22 is provided on the back side of the planar antenna element 21. The pins 21c protruding from the back side of the board 21a
2 is electrically connected.

The present embodiment is characterized in that the radio wave receiving surface 21b formed on the planar antenna element 21 has a rectangular shape when viewed in plan. Specifically, assuming XY coordinates as shown in each figure, the planar antenna element 21 is viewed in a plan view,
It is characterized in that the X-direction length Lx and the Y-direction length Ly of the radio wave receiving surface 21b are different (Lx> Ly).

As described above, the planar antenna element 21 has a structure in which the radio wave receiving surface 21b made of a conductive thin film is formed on the substrate 21a, and the radio wave receiving surface 21b is formed by using, for example, a thick film printing technique. . Therefore, the rectangular radio wave receiving surface 21b can be easily formed only by changing the mask used in the thick film printing from the conventional square shape to the rectangular shape. Therefore, the rectangular radio wave receiving surface 21b
Can be easily formed.

For convenience of explanation, the operation and effect of the radio wave receiving surface 21b having the X-direction length Lx and the Y-direction length Ly different from each other will be described later in detail. In this embodiment, dielectric ceramics is used as the material of the substrate 21a, but a resin material such as a PPO material may be used instead of the dielectric ceramics. However, since the PPO material requires punching and cutting at the time of substrate formation and is not easy to mold, it is desirable to use dielectric ceramics having good moldability as the material of the substrate 21a as in this embodiment.

On the other hand, the circuit board 22 on which the planar antenna element 21 is provided is, for example, a printed wiring board, and a predetermined wiring pattern is formed on the upper and lower surfaces thereof. The pin 21c of the planar antenna element 21 is connected to the upper surface of the circuit board 22 by soldering or the like as described above, and the lower surface is formed with an electronic circuit such as a low noise amplifier. This electronic circuit is housed in the shield case 27 in order to prevent disturbance from entering. Reference numeral 25 denotes a cable, and the antenna unit 20
Is connected to the GPS computer by this cable 25.

The bottom cover 23 is formed by resin molding. After the flat antenna element 21 and the circuit board 22 are accommodated in the mounting recess 26 formed, the bottom cover 23 is placed in a cab-shaped upper case 24 covering the entire surface. Be combined. At this time, the cable 2 connected to the circuit board 22
5 is led out of the cases 23 and 24 through a through groove 28 formed in the bottom cover 3.

The antenna unit 20 having the above configuration
Are arranged in the vehicle for the purpose of preventing mischief and theft.
As a specific arrangement position of the antenna unit 20, for example, on the dashboard 29 in the driver's seat as shown in FIGS. This is the dashboard 29
This is because the upper part is broadly opposed to the windshield 30 that allows the radio waves from the GPS satellites to pass therethrough, and the area facing the roof that blocks the radio waves from the GPS satellites is narrow.

However, as described above, even if the antenna unit 20 is arranged on the dashboard 29, the reception sensitivity in the front-rear direction (hereinafter, this direction is referred to as X1 direction) of the vehicle facing the windshield 30 is maintained well. Despite being hit, the vehicle is in the lateral direction (this direction is hereinafter referred to as Y1 direction)
About front pillar 31 and center pillar 3
As described above, since the radio wave from the GPS satellite is weakened by 2 (see FIG. 4) and the like, the reception sensitivity is reduced and the antenna unit 10 of the conventional configuration cannot perform good reception as described above.

Here, attention is paid to the shape of the radio wave receiving surface 21b formed on the planar antenna element 21 shown in FIGS. As described above, the X-direction length Lx and the Y-direction length Ly of the radio wave receiving surface 21b are different from each other when the planar antenna element 21 is viewed in a plan view. Specifically, the length Lx in the X direction is longer than the length Ly in the Y direction (Lx> Ly).

It is known that the directional characteristics of the planar antenna element 21 are correlated with the lengths of the radio wave receiving surface 21b in the X and Y directions, and thus the lengths Lx and Y of the radio wave receiving surface 21b in the X direction are known. By changing the length Ly in the direction, the directional characteristics of the planar antenna element 21 can be changed. Specifically, as the length of the radio wave receiving surface 21b is increased, the directivity characteristics are improved, and thus the reception sensitivity can be increased.

Therefore, in the planar antenna element 21 according to the configuration of the present embodiment shown in FIGS.
Since the length Lx in the X direction of b is longer than the length Ly in the Y direction (Lx> Ly), the receiving sensitivity in the X direction is higher than that in the Y direction. The radio wave receiving surface 21b
Is set equal to the conventional length.
Therefore, even if the length Lx in the X direction of the radio wave receiving surface 21b is longer than the length Ly in the Y direction as described above, the reception sensitivity in the Y direction is the same as that of the related art, and the radio wave from the GPS satellite is transmitted. There is no inconvenience to receive.

Further, in this embodiment, when the antenna unit 20 having the radio wave receiving surface 21b having the different length Lx in the X direction and the length Ly in the Y direction is arranged on the dashboard 29 (in the vehicle), the reception sensitivity is high. The direction is matched with the lateral direction Y1 of the vehicle, and the X direction having the same level of reception sensitivity as the conventional one is arranged so as to match with the longitudinal direction X1 of the vehicle.

By arranging the antenna unit 20 on the dashboard 29 (inside the vehicle) as described above, the antenna unit 20 can be disposed in the lateral direction Y1 of the vehicle on which components such as the front pillar 31 and the center pillar 32 that weaken radio waves from satellites are provided. Since the antenna unit 20 is oriented in the Y direction with a high directivity, the radio wave from the lateral direction Y1 of the vehicle can also be transmitted in the longitudinal direction X1 of the vehicle.
It is possible to obtain the same receiving sensitivity as that of the above.

As a result, the antenna unit 20 can obtain a uniform reception sensitivity in all the reception directions, thereby improving the reception probability and providing a good car irrespective of the direction of the vehicle (ie, the direction of the passenger compartment). Navigation processing can be performed. In the above-described embodiment, as a means for changing the directional characteristics of the planar antenna element 21, the configuration in which the radio wave receiving surface 21b is rectangular and the lengths in the X direction and the Y direction are different is shown.

However, the means for changing the directional characteristics of the planar antenna element 21 is not limited to this. For example, the shape of the radio wave receiving surface is made elliptical, and the lengths of the minor axis and major axis are appropriately selected. Accordingly, a planar antenna element having desired directional characteristics can be realized. Further, in the above-described embodiment, a configuration in which one radio wave receiving surface 21b is formed on the substrate 21a has been described. However, a plurality of radio wave receiving surfaces are formed on the substrate, and a desired radio wave receiving surface can be obtained by appropriately electrically connecting the surfaces. It is also possible to realize a planar antenna element having directional characteristics.

Also, by inclining the planar antenna element 22 at a predetermined angle with respect to the dashboard 29 to have a predetermined elevation angle, it is possible to further improve the reception sensitivity in the vehicle. Further, in the above-described embodiment, the configuration in which the antenna unit 20 is arranged on the dashboard 29 is shown. However, the arrangement position of the antenna unit is not limited to the dashboard. For example, the antenna unit is arranged on a rearview mirror, a windshield, or the like. It is apparent that the present invention can be applied to this case.

[0034]

According to the present invention as described above, the following various effects can be realized. According to the first aspect of the present invention, it is possible to obtain the same level of reception sensitivity as in the front-rear direction even in the lateral direction of the vehicle compartment, thereby obtaining uniform reception sensitivity in all reception directions. Therefore, the reception probability is improved, and good car navigation processing can be performed regardless of the direction in the vehicle compartment.

According to the second aspect of the present invention, antenna units having different directivity characteristics can be easily realized with a simple configuration.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an antenna unit according to an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a planar antenna element provided in the antenna unit according to one embodiment of the present invention.

FIGS. 3A and 3B are a plan view and a cross-sectional view showing, on an enlarged scale, a planar antenna element provided in an antenna unit according to an embodiment of the present invention; FIGS.

FIG. 4 is a diagram showing an example in which an antenna unit according to an embodiment of the present invention is arranged on a dashboard (part 1).

FIG. 5 is a diagram showing an example in which an antenna unit according to an embodiment of the present invention is arranged on a dashboard (part 2).

FIG. 6 is an exploded perspective view showing an example of a conventional antenna unit.

FIG. 7 is an enlarged perspective view showing a planar antenna element provided in an example of a conventional antenna unit.

FIG. 8 is a diagram showing an example in which a conventional antenna unit is arranged outside a vehicle.

FIG. 9 is a diagram showing an example in which a conventional antenna unit is arranged in a vehicle.

[Explanation of symbols]

 Reference Signs List 20 antenna unit 21 planar antenna element 21a substrate 21B radio wave receiving surface 22 circuit board 23 bottom case 24 upper case 25 cable 29 dashboard 30 windshield 31 front pillar 32 center pillar

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01Q 21/00 H01Q 21/00

Claims (2)

[Claims] 1. An antenna unit for a car navigation system, comprising: a planar antenna element for receiving a radio wave from a satellite on a receiving surface; and a case enclosing the antenna element. Assuming XY coordinates orthogonal to the element, the planar antenna element is configured to have different characteristics in the directivity in the X direction and the directivity in the Y axis direction, and the high directivity direction of the vehicle compartment An antenna unit for a car navigation device, wherein the planar antenna element is arranged to face a side. 2. The antenna unit of the car navigation device according to claim 1, wherein the planar antenna element is formed in a rectangular shape in a plan view, so that the directivity in the X direction and the directivity in the Y axis direction are improved. An antenna unit for a car navigation device, wherein the antenna unit is different.