JPH07106821A - Circularly polarized wave microstrip antenna - Google Patents

Abstract

PURPOSE:To obtain the circularly polarized wave microstrip antenna in which, when the circularly polarized wave microstrip antenna is fitted to the roof end of an automobile, the gain is increased only at a roof end at which the circularly polarized wave microstrip antenna is fitted at a low elevation angle of nearly 10 deg. and the gain is hardly fluctuated in other directions. CONSTITUTION:The circularly polarized wave microstrip antenna fitted to a roof end of an automobile is provided with a spacer 9 fitted between a font side of an end of a roof 12 of the automobile 11 and the circularly polarized wave microstrip antenna and tilting the circularly polarized wave microstrip antenna 5 by a predetermined angle in a direction of the outside of the end of the roof 12 of the automobile 11. As a result, the gain is increased only at the roof end.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
GPS (Global P) that performs positioning using radio waves from artificial satellites using 542 GHz or 1.2276 GHz
ositioning System) and other circularly polarized microstrip antennas.

[0002]

2. Description of the Related Art In a car navigation system using GPS, since the GPS satellite is an orbiting satellite and the car is also a moving body, it is a circularly polarized wave as an antenna to be mounted on the car, and within a hemisphere on the ground. It is required that the directional characteristics be as uniform as possible. Further, since it is mounted on a vehicle, a low profile antenna is required.

For this reason, a circularly polarized single element microstrip antenna as shown in FIG. 5 has been used so far. 5 (a) and 5 (b) show an example of a one-point feed type, and FIGS. 5 (c) and 5 (d) show an example of a two-point feed type. In FIG. 5, 1 is a dielectric, 2A and 2B. Two
C and 2D are patches, 3A and 3B are feeding points,
Reference numeral 4 is a ground plate, 5 and 6 are single-point feeding type circularly polarized microstrip antennas, and 7 and 8 are two-point feeding type circularly polarized microstrip antennas.

In order to reduce the blocking caused by the vehicle body as much as possible and to facilitate mounting, the antenna is often mounted at the roof end of the automobile.
However, when mounted on the end of the roof, these circularly polarized microstrip antennas have a wide beam width, so they are easily affected by the vehicle body and the ground, and antennas that take these effects into consideration are required.

However, in the conventional circularly polarized microstrip antenna, the influence of the vehicle body or the ground is hardly taken into consideration, and as shown in FIG. 6, for example, the circularly polarized microstrip antenna 5 is installed at the center of the large ground plate 10. To measure the directivity, or the circular polarization microstrip antenna 5 alone is used to measure the directivity, and the circular polarization microstrip antenna 5 has a directional characteristic that is as uniform as possible on the ground hemisphere. Has been designed to be. Figure 6
, Φ is the azimuth angle in the observation direction, θ is the angle between the elevation angle in the observation direction and the Z axis (the axis orthogonal to the surface of the ground plate 10), that is, the difference from 90 ° [θ = (90 ° − Elevation angle]].

[0006]

A conventional on-vehicle circularly polarized microstrip antenna has a directional characteristic in the azimuth (φ) direction when the circularly polarized microstrip antenna is placed at the center of a large ground plate. Has been designed to look like.

However, when such a circularly polarized microstrip antenna is attached to the end of the roof of an actual automobile, for example, as shown in FIG.
If it is mounted on the end of a square-polarized microstrip antenna 5 assuming that it is 5 m square, the gain in the vicinity of the direction where the elevation angle is about 10 ° on the roof end side (the end side of the ground plate 10) where the circularly polarized microstrip antenna 5 is mounted However, there arises a problem that the circular polarization microstrip antenna 5 is reduced compared to the vicinity of the elevation angle of 10 ° on the side opposite to the side where the circular polarization microstrip antenna 5 is attached. Normally, the circularly polarized microstrip antenna 5 is defined by the minimum gain in the covered area. However, in the case of the microstrip antenna, the gain tends to decrease as the elevation angle becomes lower. The gain in the lowest elevation direction (typically 5-10 °) is most important.

Further, according to the result of calculation including the influence of the ground performed by the inventors, when the circularly polarized microstrip antenna is attached to the roof end of the automobile, the radiation pattern near the roof end side in the low elevation angle direction. It was found that a large ripple was generated.

Therefore, rather, the gain must be higher in the low elevation angle direction on the roof end side than in the low elevation angle direction on the opposite side. Therefore, a decrease in gain on the roof end side where the circularly polarized microstrip antenna is attached at an elevation angle of about 10 ° is a very important problem.

FIG. 8 shows an example of gain asymmetry in the low elevation angle direction when a circularly polarized microstrip antenna is attached to the end of the roof.

FIG. 8 shows a ground plate 10 having a square shape of 1.55 m on a side as shown in FIG. 7 as a roof of an automobile, and a circular polarization microstrip antenna 5 is provided at the end thereof.
3 shows the measurement value of the circularly polarized radiation pattern in the XZ plane in the case where is placed. The frequency is 1.57542 GHz. It can be seen from FIG. 8 that the gain on the roof end side where the circularly polarized microstrip antenna 5 is attached is lower than the gain on the opposite side by 2 to 3 dB in the vicinity of the elevation angle of 10 °.

The present invention solves the above problem, and when mounted on the roof end of an automobile, at a low elevation angle of about 10 °, the gain increases only on the roof end side where the circularly polarized microstrip antenna is mounted. However, it is an object of the present invention to provide a circularly polarized microstrip antenna whose gain hardly changes in other directions.

[0013]

A circularly polarized microstrip antenna according to the present invention is a circularly polarized microstrip antenna attached to a roof end portion of an automobile, in which a surface of the roof end portion of the automobile and a circularly polarized microstrip antenna are provided. And a spacer for mounting the circularly polarized wave microstrip antenna at a predetermined angle toward the outside of the roof end of the automobile.

The circularly polarized microstrip antenna of the present invention is characterized in that the predetermined angle is approximately 10 °.

The circularly polarized microstrip antenna of the present invention is characterized in that the spacer is hollow.

[0016]

The circularly polarized microstrip antenna of the present invention is mounted on the roof end of an automobile through a spacer and inclined at a predetermined angle toward the outside of the roof end. The gain decreases in the high elevation angle direction on the side opposite to the roof end portion where the strip antenna is mounted, and correspondingly, the gain increases at the low elevation angle on the roof end portion side where the circular polarization microstrip antenna is mounted. As a result, at low elevation angles, the gain increases only on the roof end side where the circularly polarized microstrip antenna is mounted, and in other directions, the gain hardly changes, so the performance as a circularly polarized antenna improves. .

Since the spacer of the circularly polarized microstrip antenna of the present invention is hollow, a connector, a receiving amplifier, etc. can be inserted in the spacer.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the embodiments shown in FIG.
2 is a perspective view showing the configuration of an embodiment of the present invention, and FIG. 2 is a perspective view showing the roof of the automobile as a square.

As shown in FIGS. 1 and 2, the bottom surface 91 of the spacer 9 having a triangular cross section whose angle α between the bottom surface 91 and the inclined surface 92 is 10 ° is provided by an appropriate means, for example, a magnet, to the roof 12 of the automobile 11. The circularly polarized microstrip antenna 5 of the one-point feeding type is fixedly attached to the slope 92 of the spacer 9 so as to be detachably fixed to the end portion, and the circularly polarized microstrip antenna 5 is arranged at an angle of 10 ° outside the roof 12. Attach it at an angle.

As described above, the roof 1 is provided via the spacer 9.
In the case where the circularly polarized microstrip antenna 5 is attached to the end portion of 2, the operation will be described assuming that the roof 12 is the ground plate 10 which is a square plate of 1.55 m square.

When the circular polarization microstrip antenna 5 is attached to the end of the ground plate 10 via the spacer 9, the angle α formed by the bottom surface 91 of the spacer 9 and the slope 92 is 0 °, 5 °, 10 °. The circularly polarized radiation pattern in the XZ plane was measured for each case of ° and 15 °. The measurement results are as shown in FIG. 3, and in the circularly polarized radiation pattern of FIG. 3, the solid line indicates the case where the angle α is 0 °, the broken line indicates the case where the angle α is 5 °, and the dashed-dotted line indicates the angle α. The case of 10 ° and the chain double-dashed line indicate the case where the angle α is 15 °.

The above-mentioned case is different only in that the circularly polarized microstrip antenna 5 in FIG. 7 is attached to the ground plate 10 via the spacer 9, and other conditions are the same. In the case of this embodiment, Bottom surface 91 and slope 9 of spacer 9
As the angle formed with 2 increases, the gain increases at a low elevation angle on the end side where the circular polarization microstrip antenna 5 is attached, but the end where the circular polarization microstrip antenna 5 is attached increases. It can be seen that the gain hardly changes at the low elevation angle on the side opposite to the section side.

The main wave which contributes to the radiation pattern explained in the two-dimensional model as shown in FIG. 4 is the wave when the circularly polarized microstrip antenna 5 is attached to the roof end using the spacer 9. The direct wave A from the original (antenna) S, the edge diffracted wave B from the edge on the roof end side, and the edge diffracted wave C from the edge on the opposite side to the roof end.

By tilting the circularly polarized microstrip antenna 5 toward the outside of the roof end, the amplitude of the direct wave A and the amplitude of the edge diffracted wave B increase in the low elevation angle direction on the roof end side, and Increases in amplitude. Although the amplitude of the edge diffracted wave C decreases, the amplitude of the edge diffracted wave C is much smaller in the low elevation angle direction on the roof end side than the amplitude of the direct wave A and the edge diffracted wave B. Can be ignored.

On the other hand, the gain in the low elevation direction on the side opposite to the roof end side where the circularly polarized wave microstrip antenna 5 is attached is the amplitude and edge of the direct wave A due to the tilting of the circularly polarized wave microstrip antenna 5. Although the amplitude of the diffracted wave B is reduced, the amplitude of the edge diffracted wave C is increased, so that they cancel each other and hardly change. However, even on the opposite side of the roof end where the circularly polarized microstrip antenna 5 is attached, the amplitude of the edge diffracted wave C with respect to the amplitude of the direct wave A becomes smaller when the elevation angle becomes higher.
As the circularly polarized microstrip antenna 5 is tilted,
The gain is reduced.

That is, the circularly polarized microstrip antenna 5 is moved outward from the end portion of the roof 12 of the automobile 11.
By mounting the circularly polarized microstrip antenna 5 at an angle of 0 °, the gain decreases in the high elevation direction opposite to the end of the roof 12 on which the circularly polarized microstrip antenna 5 is mounted. The gain increases at a low elevation angle on the end side of the roof 12 on which is mounted. As a result, at low elevation angles, circularly polarized microstrip antenna 5
Gain increases only on the end side of the roof 12 where
In other directions, the gain hardly fluctuates, which improves the performance as a circularly polarized microstrip antenna mounted on the end of the roof of a vehicle.

Since the spacer 9 is hollow, the spacer 9
It is also possible to insert a connector, a receiving amplifier or the like therein.

In the embodiment described above, the case of the circularly polarized microstrip antenna 5 mounted via the spacer is illustrated, but instead of the circularly polarized microstrip antenna 5, the circularly polarized microstrip antenna 6 is used. , 7 and 8 are the same.

[0029]

As described above, according to the present invention, the circularly polarized microstrip antenna is mounted between the roof end surface of the automobile and the circularly polarized microstrip antenna so that the circularly polarized microstrip antenna is provided outside the roof end of the automobile. Since a spacer that tilts at a predetermined angle to the direction is provided, the circularly polarized microstrip antenna is tilted at a predetermined angle toward the outside of the roof end of the vehicle, and at low elevation angles, the end side of the roof where the circularly polarized microstrip antenna is mounted is attached. Since the gain increases only in and the gain hardly changes in other directions, it has an effect of improving the performance as a circularly polarized microstrip antenna attached to the end of the roof of an automobile.

Further, since the spacer is hollow, there is an effect that a connector, a receiving amplifier, etc. can be inserted into the spacer.

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of an embodiment of the present invention.

FIG. 2 is a perspective view showing the configuration of an embodiment of the present invention, showing an example where the roof is assumed to be a ground plate.

FIG. 3 is a diagram showing an XZ in-plane circularly polarized radiation pattern according to an embodiment of the present invention.

FIG. 4 is a diagram showing a two-dimensional model for explaining the operation of one embodiment of the present invention.

FIG. 5 is a perspective view of a vehicle-mounted circularly polarized microstrip antenna.

FIG. 6 is a perspective view when a conventional circularly polarized microstrip antenna is provided in the center of a ground plate.

FIG. 7 is a perspective view when a conventional circularly polarized microstrip antenna is provided at an end of a ground plate.

FIG. 8 is a diagram showing an XZ in-plane circularly polarized radiation pattern in the case of FIG. 7;

[Explanation of symbols]

1 ... Dielectric 2A, 2B, 2
C, 2D ... Patch 3A, 3B ... Feeding point 4, 10 ... Ground plate 5, 6 ... 1-point feeding type circularly polarized microstrip antenna 7, 8 ... 2-point feeding type circularly polarized microstrip antenna 9 ... Spacer 11 ... Automobile 12 ... Roof 91 ... Bottom 92 ... Slope

Claims (3)

[Claims] 1. A circularly polarized microstrip antenna attached to a roof end of a vehicle, wherein the circularly polarized microstrip antenna is mounted between the roof end surface of the vehicle and the circularly polarized microstrip antenna. A circularly polarized microstrip antenna comprising a spacer tilted at a predetermined angle toward the outside of the roof end. 2. The circularly polarized microstrip antenna according to claim 1, wherein the predetermined angle is approximately 10 °. 3. The circularly polarized microstrip antenna according to claim 1, wherein the spacer is hollow.