JP2007159032A - Antenna system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna system capable of enhancing a radiation gain at a low elevation angle in a cable lead-out direction and to provide an antenna system for taking into account that radiation of a rear side is not a noise source with respect to neighboring electronic apparatuses. <P>SOLUTION: Each of the antenna system 1, (20) includes: an antenna body 2 provided with a patch antenna element; a feeding cable 6 connected to the antenna body 2 and led out externally; and a sheet metal made bracket 7 for mounting and supporting the antenna body 2 and fitted to an installation mother member such as a dashboard, and the outward form of the bracket 7 is to be, e.g. rectangle. In the case of improving the radiation gain at a low elevating angle in the cable lead-out direction, the short side direction of the bracket 7 is almost matched with the cable lead-out direction. Further, in the case of suppressing the radiation to the rear side in a particular direction, the long side direction of the bracket 7 is almost matched with the cable lead-out direction and arranged in the particular direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a small antenna device that is suitable as a GPS (Global Positioning System) antenna or the like and is mounted using a bracket made of sheet metal.

In recent years, an increasing number of vehicles have a small antenna device such as a GPS antenna on a dashboard. In this type of antenna device, a feed cable such as a coaxial cable is connected to an antenna body provided with a patch antenna element, a feed circuit, and the like, and the antenna body is connected to a receiver via the feed cable. Etc. (see, for example, Patent Document 1). In many cases, the power feeding cable connected to the antenna body is led downward after being led out to the windshield side. Also, the antenna body is usually held on a sheet metal bracket fixed on a base metal such as a dashboard using the magnetic force of the magnet, but this bracket also functions as a ground plate. This contributes to the improvement of radiation gain. Since the antenna body is mounted at the center of the bracket, the bracket has a square outer shape so as not to affect the directivity of the radiation pattern.
Japanese Patent Laying-Open No. 2004-228802 (page 4-8, FIG. 6)

  As described above, the bracket for mounting and holding the antenna main body has a square outer shape. However, when the inventors examined the radiation pattern of this type of antenna device in detail, the antenna main body was examined. It has been found that the power supply cable connected to the cable and led out of the bracket acts as if the ground plate is extended to affect the radiation pattern. For this reason, for example, in the GPS antenna, there has been a problem that a radiation gain at a low elevation angle cannot be sufficiently secured in the vehicle traveling direction, which is the direction in which the feed cable is led out.

  Further, when an antenna device is installed on a dashboard in which various electronic devices are stored in a lower space, radiation to the back side of the antenna device may become a noise source for nearby electronic devices. However, this point has not been considered in the past.

  The present invention has been made in view of the actual situation of the prior art, and a first object of the invention is to provide an antenna device capable of increasing the radiation gain at a low elevation angle in the cable derivation direction. . A second object of the present invention is to provide an antenna device that takes into consideration that radiation to the back side does not become a noise source for nearby electronic devices.

  In order to achieve the first object, in the antenna device of the present invention, an antenna body provided with a patch antenna element, a feed cable connected to the antenna body and led out to the outside, and the antenna A bracket made of sheet metal that is mounted on and held on a base material such as a dashboard by mounting and holding the main body, one of the two directions orthogonal to the outer shape of the bracket passing through its center is a long axis and the other is a short axis In such a configuration (for example, a rectangular shape), the short axis direction of the bracket is substantially matched with the lead-out direction of the power feeding cable.

  The antenna device configured as described above takes into account that a feeding cable connected to the antenna body and led out in one direction affects the radiation pattern, and the length of the bracket along the cable leading-out direction. Since the length is shorter than the length of the bracket along the direction orthogonal to the cable derivation direction, the effect of the ground on the radiating conductor of the patch antenna element is weakened in the cable derivation direction, and the direction is low. The radiation gain of the elevation angle can be increased.

  In order to achieve the second object described above, in the antenna device of the present invention, an antenna main body provided with a patch antenna element, a feed cable connected to the antenna main body and led out to the outside, A metal plate bracket mounted and held on the antenna base body and mounted on the antenna main body, one of the two directions orthogonal to the bracket passing through its center is a long axis and the other is a short axis The long axis direction of the bracket is substantially coincident with the lead-out direction of the power feeding cable.

  In the antenna device configured in this way, the lead-out direction of the feed cable connected to the antenna body and the major axis direction of the bracket are substantially matched. The action is strengthened and the radiation to the back side is reduced. Therefore, when an electronic device that is easily affected by antenna noise is arranged in the vicinity, if the major axis direction of the bracket is aligned with the direction in which the electronic device exists when viewed from the antenna device, The possibility that radiation becomes a noise source for the electronic device is very low.

  In any of the above-described configurations, if a cut-and-raised piece for positioning the antenna body is provided on the bracket, the lead-out direction of the power supply cable connected to the antenna body is set to the minor axis direction or the major axis of the bracket. This is preferable because the setting of aligning in the direction can be performed easily and reliably, and there is no possibility that the antenna body is displaced after being mounted on the bracket.

  In the antenna device according to the present invention, the outer shape of the bracket for mounting and holding the antenna body is not square, and the minor axis direction of the bracket is substantially matched with the direction in which the feed cable connected to the antenna body is derived. The action of the ground on the radiation conductor is weakened in the cable lead-out direction, and the radiation gain at a low elevation angle can be increased in that direction.

  Further, in the antenna device of the present invention, the outer shape of the bracket for mounting and holding the antenna body is not square, and the major axis direction of the bracket is substantially matched with the lead-out direction of the feed cable connected to the antenna body. Therefore, the action of the ground on the radiation conductor is strengthened in this specific direction, and the radiation toward the back side is reduced. Therefore, when an electronic device that is easily affected by antenna noise is arranged in the vicinity, if the major axis direction of the bracket is aligned with the direction in which the electronic device exists when viewed from the antenna device, The possibility that radiation becomes a noise source for the electronic device is very low.

  FIG. 1 is a perspective view of an antenna device according to a first embodiment of the present invention, and FIG. 2 is a characteristic diagram showing a radiation gain at a low elevation angle of the antenna device. FIG. 3 is a schematic diagram showing a radiation pattern on a vertical plane along the short side direction of the bracket of the antenna device.

  An antenna device 1 shown in FIG. 1 is a GPS antenna installed on a dashboard (installation base material) in a vehicle interior, and is a sheet metal radiation conductor on a circuit board 4 in a radome (only the bottom plate portion is shown). The antenna main body 2 holding the plate 5, the feed cable 6 connected to the circuit board 4 of the antenna main body 2 and led out to the outside, and the antenna main body 2 mounted on a dashboard (not shown) And a bracket 7 made of a sheet metal that holds and holds the main body.

  The circuit board 4 of the antenna body 2 is provided with a ground conductor layer 8 on almost the entire top surface. An electronic component (not shown) is mounted on the bottom surface of the circuit board 4 to form an electronic circuit section such as a power feeding circuit. The electronic circuit section is covered with a sheet metal shield cover 9 and electromagnetically shielded. Has been. The outer shape of the radiation conductor plate 5 is a shape in which four corners of a square are cut out, and mounting leg pieces 10 are bent at the four corners, and these mounting leg pieces 10 are formed on the bottom side of the circuit board 4. By soldering to the land, the radiation conductor plate 5 is stably held at a position facing the ground conductor layer 8 with a predetermined distance. Further, the power supply leg pieces 11 are bent at two places on the radiating conductor plate 5, and these power supply leg pieces 11 are connected to the power supply circuit on the bottom surface side of the circuit board 4 to thereby form a two-point power supply type circle. It operates as a polarization antenna. That is, a circularly polarized wave patch is formed by the radiation conductor plate 5, the mounting leg piece 10 and the power feeding leg piece 11 formed by processing a single metal plate, and the ground conductor layer 8 provided on the circuit board 4. An antenna element is configured.

  The feeding cable 6 is a known coaxial cable, and its inner conductor is electrically connected to a pair of feeding legs 11 through a feeding circuit, and its outer conductor is electrically connected to the ground conductor layer 8 and the shield cover 9. It is connected. The feed cable 6 is led out from the antenna body 2 to a windshield side (vehicle traveling direction) (not shown) in a straight line, and is then led downward to be connected to a receiver or the like.

  The outer shape of the bracket 7 is rectangular (rectangular), and the antenna body 2 is mounted at the center thereof, so that both end portions in the longitudinal direction (long axis direction) of the bracket 7 protrude greatly from the antenna body 2. A cut-and-raised piece 7a for positioning and locking the antenna body 2 is formed at these protruding portions. Since the short direction (short axis direction) of the bracket 7 is substantially matched with the lead-out direction of the feed cable 6 connected to the antenna body 2, the feed cable 6 is outward from the antenna body 2. As soon as it is led out, it extends in a state of protruding from the bracket 7.

  In the antenna device 1 configured in this way, the short side direction of the rectangular bracket 7 is substantially matched with the lead-out direction (vehicle traveling direction) of the feeding cable 6 connected to the antenna body 2. The action of the ground on the radiating conductor plate 5 of the patch antenna element can be weakened in the cable lead-out direction. That is, since the power supply cable 6 that protrudes from the bracket 7 acts as if the ground plate is extended, if the bracket 7 has a square shape, the ground in the lead-out direction of the power supply cable 6 is assumed. As a result, the radiation gain at a low elevation angle is undesirably reduced in front of the vehicle. However, if the bracket 7 is rectangular and its short direction is aligned with the lead-out direction of the power feeding cable 6 as in the present embodiment, the action of the ground is weakened in the short direction and radiation at a low elevation angle is achieved. Since the gain is increased (see FIG. 3), as shown in FIG. 2, a radiation gain at a low elevation angle (elevation angle of 10 degrees) can be sufficiently ensured in front of the vehicle (azimuth angle near 0 degrees). Therefore, the antenna device 1 can improve the effective sensitivity of the GPS signal.

  Further, since the antenna device 1 is provided with the cut-and-raised piece 7a for positioning and locking the antenna main body 2 to the bracket 7, the direction in which the feeding cable 6 connected to the antenna main body 2 is led out is determined by the bracket 7. The setting of aligning in the short direction can be performed easily and reliably, and there is no possibility that the antenna body 2 is displaced after being mounted on the bracket 7.

  FIG. 4 is a perspective view of an antenna device according to a second embodiment of the present invention, and FIG. 5 is a schematic diagram showing a radiation pattern in a vertical plane along the longitudinal direction of the bracket of the antenna device, corresponding to FIG. The description which overlaps by attaching | subjecting the same code | symbol to is abbreviate | omitted.

  The antenna device 20 shown in FIG. 4 is the same as the first embodiment described above in that it is installed on the dashboard in the passenger compartment, but the longitudinal direction of the rectangular bracket 7 is not the short direction but the long direction. The point substantially matched with the bull derivation direction is greatly different from the first embodiment. That is, in this antenna device 20, an unillustrated electron that is easily affected by antenna noise on the back side (the space below the dashboard) in the direction opposite to the direction in which the feeding cable 6 connected to the antenna body 2 is led out. Considering that the devices are arranged at a close distance, the radiation to the back side of the antenna device 20 is configured not to be a noise source for the electronic device. Specifically, since the longitudinal direction (major axis direction) of the bracket 7 is substantially matched with the lead-out direction of the feed cable 6 connected to the antenna body 2, the longitudinal direction of the bracket 7 as shown in FIG. Thus, radiation to the back side of the antenna device 20 is reduced, and the adverse effect of antenna noise on the electronic device can be avoided.

  Note that the outer shape of the bracket 7 is not rectangular, but may be a polygon or an ellipse having a major axis and a minor axis. In each of the above embodiments, the case where the circularly polarized antenna element is employed in the sheet metal patch antenna structure is described, but the antenna element may be a dielectric patch antenna structure or a linearly polarized wave antenna. Needless to say, the present invention is applicable.

1 is a perspective view of an antenna device according to a first embodiment of the present invention. It is a characteristic view which shows the radiation gain of the low elevation angle of this antenna apparatus. It is a schematic diagram which shows the radiation pattern in the vertical surface along the bracket transversal direction of this antenna apparatus. It is a perspective view of the antenna apparatus which concerns on the 2nd Example of this invention. It is a schematic diagram which shows the radiation pattern in the vertical surface along the bracket longitudinal direction of this antenna apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,20 Antenna apparatus 2 Antenna main body 4 Circuit board 5 Radiation conductor plate 6 Feeding cable 7 Bracket 7a Cut and raised piece 8 Grounding conductor layer 11 Feeding leg piece

Claims (4)

An antenna body provided with a patch antenna element, a feed cable connected to the antenna body and led out to the outside, and a metal plate bracket mounted and held on the installation base material by mounting and holding the antenna body; With
The outer shape of the bracket is shaped so that one of two directions orthogonal to each other through its center is a major axis and the other is a minor axis, and the minor axis direction of the bracket is substantially matched with the lead-out direction of the power feeding cable. An antenna device characterized by that. An antenna main body provided with a patch antenna element, a feed cable connected to the antenna main body and led out outward, and a metal plate bracket mounted and held on the base metal by mounting and holding the antenna main body Prepared,
The outer shape of the bracket is shaped so that one of two directions perpendicular to the center is a major axis and the other is a minor axis, and the major axis direction of the bracket is substantially matched with the lead-out direction of the feeding cable. An antenna device characterized by that.   3. The antenna device according to claim 1, wherein a cut-and-raised piece for positioning the antenna body is provided on the bracket.   The antenna device according to claim 1, wherein an outer shape of the bracket is rectangular.

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