JPH0637524A - Satellite communication reception equipment for automobile - Google Patents

Abstract

PURPOSE:To receive satellite communication with a directional pattern of satisfactory low-elevation angle reception characteristic. CONSTITUTION:An antenna 3 is attached to a ceiling 2 in the room of an automobile 1. At this time, the antenna 3 having the inverse circular polarization characteristic to the plane of circular polarization to be used is so attached that the reception direction is downward. Not only the radio wave which is reflected by the floor face of the automobile body and the ground to become an inverse circularly polarized wave signal is received by the antenna 3 but also reception from the zenith direction is suppressed by the screening action of the roof of the automobile body of the automobile, and the directional pattern in the zenith direction of the antenna 3 is suppressed to increase the gain in the low-elevation angle direction, and the directional pattern of satisfactory low-elevation angle reception characteristic where the gain in the zenith direction is low and the gain in the low-elevation angle direction is high is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite communication receiver mounted on an automobile.

[0002]

2. Description of the Related Art In satellite communication, circularly polarized waves are often used as radio waves to be received, and a helical antenna or the like is used as a receiving antenna. The helical antenna is suitable as an antenna for receiving satellite communication because of its excellent low elevation angle gain characteristic. However, since the helical antenna has a three-dimensional shape, when mounted on a vehicle such as a passenger car, the helical antenna is prominently prominent and conspicuous, which impairs the appearance of the vehicle.

On the other hand, a planar printed antenna as shown in FIG. 4 is provided by the present applicant. This printed antenna is a microstrip type antenna, and for example, a printed wiring board 8 constituting a dielectric layer is formed by printing each copper foil using a double-sided copper-clad laminate.
Antenna conductor layer 9 with copper foil patch on one side facing each other
And the ground conductor layer 10 on the other surface. In FIG. 4, reference numeral 13 denotes an antenna feeding portion formed by a through hole, a feeding pin or the like for connecting the feeding point 12 of the antenna conductor layer 9 and the antenna output terminal portion 11. The printed antenna formed by using the double-sided copper-clad laminate in this way is widely used because it has uniform characteristics and is suitable for mass production. Moreover, the printed antenna is made thin and compact. Therefore, it is suitable as an antenna to be mounted on an automobile. In particular, the on-vehicle communication satellite antenna A is often mounted and mounted on the central portion of the roof 14 of the automobile 1 as shown in FIG. Printed antennas are suitable and are being used widely.

Incidentally, as satellites for mobile communication such as automobiles, there are geostationary satellites and mobile (orbiting) satellites. And since the former geostationary satellite is on the equator, it has an elevation angle of 3 in Japan.
A directional characteristic having a peak near 0 ° is desirable. For example, as shown in FIG. 6, a flat directional characteristic in which the gain in the zenith direction is low and the gain in the low elevation angle direction is high is desirable. Also GPS
(Global Positioning System
m) In the latter mobile satellites such as GPS satellites of the receiving system, orbiting the earth in a low altitude circular orbit, when the satellite is located in the zenith direction, the distance from the satellite becomes short and the radio wave from the satellite Is strongly received, and when the satellite is located at a low elevation angle, the distance between the satellite and the satellite increases and the radio wave of the satellite weakens. Therefore, in this case as well, the antenna characteristic is preferably a flat directional characteristic in which the gain in the zenith direction is low and the gain in the low elevation angle direction is high as in the case of FIG.

[0005]

However, as shown in FIG. 5B, the antenna characteristics of the planar type print antenna have a low low elevation angle gain characteristic, and it is difficult to control the directivity characteristic with a single element print antenna. , There was a problem in the efficiency of satellite communication reception. The present invention has been made in view of the above points, and an object of the present invention is to enable reception of satellite communication with good directional characteristics of low elevation angle reception characteristics.

[0006]

A satellite communication receiving apparatus for an automobile according to the present invention includes an antenna 3 having a reverse circular polarization characteristic with respect to a circular polarization plane to be used, on a ceiling 2 in a vehicle interior of the automobile 1. It is characterized in that it is mounted with the receiving direction facing downward. In the present invention, a flat printed antenna is used as the antenna 3.

Further, according to the present invention, the antenna 3 can be arranged in the storage cover 5 of the interior light 4 attached to the ceiling 2 in the vehicle compartment of the automobile 1. Further, in the present invention, the antenna 3 can be attached to each of the front part and the rear part of the ceiling 2 in the vehicle interior of the automobile 1 to be used as a diversity type antenna.

[0008]

The antenna 3 having a reverse circular polarization characteristic with respect to the circular polarization plane to be used is attached to the ceiling 2 in the vehicle interior of the automobile 1 with the reception direction facing downward, so that direct wave reception is not performed but the floor of the vehicle body is received. The antenna 3 can receive the radio wave reflected on the surface or the ground, and the directional characteristic of the antenna 3 in the zenith direction is suppressed by the shielding effect of the roof of the car body of the automobile 1.
It is possible to obtain good directional characteristics with low elevation angle reception characteristics.

[0009]

EXAMPLES The present invention will be described in detail below with reference to examples. As the antenna 3, a plane type print antenna is used, and the one shown in FIG. 4 or the like can be used. Further, the antenna 3 is used so as to have a reverse circular polarization characteristic with respect to the circular polarization of the radio wave used, that is, the radio wave oscillated from the satellite. As shown in FIG. 1, the antenna 3 is attached to the lower surface of the ceiling 2 in the passenger compartment of the automobile 1 such as a passenger car. The antenna 3 has its receiving direction facing downward, that is, the antenna conductor layer 9 faces downward,
It is attached to the lower surface of the central portion of the ceiling 2.

However, in FIG. 1, the arrow lines indicate the arrival paths of radio waves, and the automobile 1 is viewed from four windows such as the front window, rear window and side windows.
The antenna 3 can receive a radio wave that reaches the vehicle interior. In FIG. 1, the arrow line a is the arrival path of the radio wave reflected on the floor surface of the automobile 1, and the arrow line b is the vehicle body 1 of the automobile.
The arrival path of the radio wave reflected by 5 and the arrow C indicate the arrival path of the radio wave reflected on the ground (the reflection point is not shown), and the reflected waves of the circularly polarized signals of these radio waves are On the reflecting surface, the electric field component parallel to the reflecting surface is reflected in the opposite phase, and the electric field component perpendicular to the reflecting surface is reflected in the same phase. However, since the antenna 3 has a reverse circular polarization characteristic with respect to the circular polarization of the radio wave used, it is possible to receive the radio wave reaching the receiving surface of the antenna 3 at these low elevation angles. Is. On the other hand, radio waves from the zenith direction are prevented from reaching the antenna 3 due to the shielding effect of the roof 14 formed of a steel plate or the like of the automobile 1, so that the directional characteristics of the antenna 3 in the zenith direction are suppressed. The radio waves of the above-mentioned arrow lines a, b, and c can be efficiently received in the passenger compartment. Therefore, even if the antenna 3 itself has the directional characteristics as shown in FIG. 5B, the gain reduction amount in the zenith direction is a gain increase amount in the low elevation angle direction unless the antenna gain is reduced, as shown in FIG. Since the gain in the zenith direction is low, the gain in the low elevation angle direction is high, and the directional characteristic with the low elevation angle reception characteristic is good, the satellite communication can be favorably received.

FIG. 2 shows an example in which the above-mentioned antenna 3 is arranged in the interior light 4 of the automobile 1. The conductor chassis of a steel plate or the like constituting the ceiling 2 (roof 14) of the automobile 1 is shown in FIG. The interior light bulb 16 is formed by attaching the annular interior light bulb 16 to the lower surface and covering the interior light bulb 16 with the storage cover 5. And Figure 2
As shown in (b), the ceiling 2 in the interior light bulb 16
The low noise amplifier circuit section 17 and the antenna 3 are attached to the lower surface of the antenna 3, and the antenna 3 is covered with the storage cover 5. In this way, the storage cover 5 of the interior light 4 can also be used as an antenna cover to hide the antenna 3, so that the antenna 3 does not spoil the appearance of the vehicle interior.

In the embodiment shown in FIG. 3, the antenna 3 is attached to the lower surface of the front ceiling 2 and the lower surface of the rear ceiling 2 in the interior of the automobile 1. Each antenna 3 is connected to the receiver 19 via the antenna switching circuit unit 18. With this antenna, it is possible to perform diversity reception with two antennas 3.
This is a highly sensitive receiving system.
Of course, the number of antennas 3 is not limited to two, and more antennas may be installed in the vehicle compartment of the automobile 1.

When mounting the antenna 3 on the automobile 1 as described above, the antenna 3 is arranged on the lower surface of the ceiling 2. Therefore, the waterproofness and weather resistance as in the case where the antenna 3 is arranged outside the vehicle body 15 are taken into consideration. It is not necessary to do so, and it can be installed at low cost. Further, compared with the case where the antenna 3 is arranged on the dashboard part or the like, the antenna 3 is less likely to be shielded by an object, and high-sensitivity reception in a low elevation angle direction is possible.

[0014]

As described above, according to the present invention, an antenna having a reverse circular polarization characteristic with respect to a circular polarization plane to be used is mounted on the ceiling of the interior of an automobile with the receiving direction facing downward. , The antenna can receive the radio waves that have become circularly polarized signals of reverse rotation by being reflected on the floor surface or the ground of the vehicle body, and the reception from the zenith direction can be suppressed by the shielding effect of the roof of the vehicle body. It is possible to suppress the directional characteristics of the antenna in the zenith direction and increase the gain in the low elevation angle direction.The gain in the zenith direction is low, the gain in the low elevation angle direction is high, and the low elevation angle reception characteristic is good. The directional characteristic can be obtained, and the satellite communication can be favorably received.

Further, since the planar printed antenna is used as the antenna, the thin and compact printed antenna can form the receiving device without forming a large protrusion, which spoils the aesthetics of the vehicle interior and impairs safety. It will not get drunk. Furthermore, since the antenna is arranged inside the interior light storage cover that is attached to the ceiling of the interior of the automobile, the antenna can be hidden using the interior light storage cover. The aesthetics of will not be spoiled by the antenna.

Further, since the antennas are attached to the front and rear portions of the ceiling of the interior of the automobile to be used as a diversity type antenna, a highly sensitive receiving system can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the present invention.

2A and 2B are views showing an interior light of the above, wherein FIG. 2A is a sectional view and FIG. 2B is a perspective view with a storage cover removed.

FIG. 3 is a schematic view of another embodiment of the present invention.

FIG. 4 is a perspective view showing a printed antenna.

5A and 5B show a conventional example, in which FIG. 5A is a schematic diagram thereof, and FIG. 5B is an antenna directivity characteristic diagram.

FIG. 6 is an antenna directivity characteristic diagram showing a flat directivity characteristic.

[Explanation of symbols] 1 Car 2 Ceiling 3 Antenna 4 Interior light 5 Storage cover

Claims (4)

[Claims] 1. A satellite communication receiver for an automobile, characterized in that an antenna having a reverse circular polarization characteristic with respect to a circular polarization plane to be used is attached to a ceiling in the interior of the automobile with the receiving direction facing downward. apparatus. 2. The satellite communication receiving apparatus for an automobile according to claim 1, wherein a planar printed antenna is used as the antenna. 3. The satellite communication receiving device for an automobile according to claim 1, wherein the antenna is arranged in a storage cover for an interior light attached to a ceiling of a vehicle interior of the automobile. 4. The satellite communication receiving apparatus for an automobile according to claim 1, wherein antennas are attached to front and rear portions of a ceiling in a passenger compartment of the automobile to be used as diversity antennas.