JPH02154504A - Case for circular antenna - Google Patents

Abstract

PURPOSE:To prevent deterioration in the antenna performance due to adhesion of water drop even in rainy weather by providing a mechanism excluding water drop adhered on the upper face of an antenna case. CONSTITUTION:Many drainage holes 20 are provided on parts other than the upper part of the circular antenna on the upper face of a case 19 and led to a slit 22 provided on the case side face. Moreover, a part 23 (hatched part) of the side face provided with the slit 22 is eliminated. Water drops dripped on the outside of the edge of circular antennas 15,16 at the upper face of the case flows out via the slit 22 from the holes 20 and hardly remain on the antenna upper part. Thus, the deterioration in the characteristic due to water drops is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a case structure in which a plurality of circular antennas are housed side by side in a planar manner, with less deterioration of characteristics due to adhesion of rain or the like.

[Prior art]

Examples of conventional circular antennas include those described in ``Axisymmetric Mode Annular Patch Antenna and Its Power Feeding Method'' by Kaneda, Fuzono et al., Technical Research Report AP87-53, pp. 21-24 There is.

FIG. 5 is a plan view and a side view of the circular antenna described above.

In FIG. 5, a metal disk 1 and a base plate 2 are connected in parallel via a plurality of pins 1 to 3. An electric signal is supplied from the coaxial cable 5 through a power supply pin 4 provided at the center of the disc 1, and radio waves are radiated from the gap between the disc 1 and the ground plate 2.

[Problem to be solved by the invention]

In the above circular antenna, the circular plate 1 and the ground plate 2 are
Since radio waves are emitted from the gap between the disk 1 and the disk 1, the characteristics will not deteriorate even if there is a metal or dielectric material directly above the disk 1.
If there is a dielectric material, metal, etc. outside the edge of the disk 1, radio waves will be reflected, and the antenna characteristics will deteriorate.

FIG. 8 is a diagram showing the return loss characteristics of the antenna when a resin plate 7 is provided on the top of the circular antenna 6 and water droplets 8 corresponding to a precipitation amount of 100 mm/h are attached thereon.

As can be seen from FIG. 8, when water droplets adhere, the center frequency shifts and the band axis also changes compared to when no water droplets adhere.

As mentioned above, the deterioration of characteristics due to water droplets occurs when there are water droplets outside the edge of the disk 1.
It hardly occurs when there are water droplets only directly above the surface.

Therefore, in the case of a case that accommodates only one circular antenna, for example, as shown in FIG.
If the shape of is made to follow the outer shape of the circular antenna 6, and the case outer plate is present only at the center of the circular plate 1, then
Even if water droplets were to adhere thereto, it is possible to prevent almost any characteristic deterioration from occurring.

However, as shown in FIG. 7, for example, when two circular antennas 6 and 6' are housed in one case 11 made of resin or the like and used as a diversity antenna by being attached to the roof or trunk of a car, During rainy weather, if water droplets adhere to the top of the case, especially the shaded area 13, they will be diagonally above the edge of the circular antenna, causing a change in characteristics.
There is a problem that performance deteriorates.

The present invention has been made in order to solve the problems of the prior art as described in (2) above, and it is an object of the present invention to provide a case for a circular antenna that can prevent characteristic deterioration due to the adhesion of water droplets during rainy weather.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an antenna case in which a plurality of circular antennas are housed side by side in a planar manner, and is provided with a mechanism for removing water droplets adhering to the top surface of the antenna case. There is.

For example, as shown in the embodiment described below, the mechanism for removing water droplets described in "-" is as follows: ■ A large number of circular, lattice-like, or mesh-like holes are provided on the top surface of the case other than the top of the circular antenna, and A structure in which a drainage port is provided on the side that communicates with the hole to drain water droplets from the above area.

■The part of the top of the case other than the top of the circular antenna has a structure that slopes outward to drain water droplets from that part.

■The top surface of the case is slanted relative to the horizontal plane, which eliminates water droplets from the entire two sides of the case.

etc. are possible.

With the above configuration, in the present invention, it is possible to prevent water droplets from being present on the top surface of the case other than the top of the circular antenna, which would lead to deterioration of characteristics.

〔Example〕

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

In FIG. 1, reference numeral 19 is a resin case in which circular antennas 15 and 16 are housed.

In addition, a large number of holes 2o for draining water are provided in a portion other than a portion of the circular antenna on the top surface of the case 19, and are electrically connected to the drain holes 1 to 22 provided on the side surface of the case.

Note that the side surface portion 23 (shaded portion) where the slit 22 is provided can also be removed.

Further, reference numeral 21 indicates a base portion for attaching the case to a vehicle body or the like.

Next, the effect will be explained.

Water droplets dripping onto the outer edges of the l'J-shaped antennas 15 and 1.6 on the top surface of the case flow through the holes 20 to Surin 1 and 2.
It flows out via 2, and hardly any remains in the part marked ``-''. Therefore, deterioration of characteristics due to water droplets can be prevented.

Further, the shape of the holes 20 described above may be any other shape as long as water droplets can easily flow therethrough, such as a lattice-like structure or a mesh-like structure as shown in FIG. 2.

Next, FIG. 3 shows another embodiment of the present invention, in which (a) is an overall perspective view, and (b) and (C) are AA' in (a).
A cross-sectional view is shown.

In this embodiment, a resin case 30 has a constriction in the center, and the constriction is inclined outward, so that water droplets can be drained from the constriction.

In addition, in the case of this embodiment, as shown in (b), if the height of the central part other than the central part is lower than the height of the built-in circular antenna, even if water droplets adhere to that part, the characteristics will deteriorate. It is possible to prevent this from occurring. Furthermore, by attaching the base 31 with an inclination, drainage performance can be improved.

Next, FIG. 4 is a sectional view of still another embodiment of the present invention.

In this embodiment, the entire upper surface of the resin case 33 is tilted with respect to the horizontal plane, so that water droplets on the entire two surfaces are removed.

Furthermore, in this embodiment, the height H of the circular antenna 16 with the higher case surface can be increased, making it easier to widen the bandwidth of this antenna.

Therefore, it is convenient as a diversity antenna for a car phone, where one antenna is used for transmission and reception that requires a wide band, and the other antenna is used for reception that does not cause any problem even if the band is relatively narrow.

〔Effect of the invention〕

As described above, according to the present invention, an antenna case in which a plurality of circular antennas are housed side by side in a planar manner is configured to include a mechanism for removing water droplets adhering to the top surface of the antenna case. As a result, it is possible to prevent deterioration of antenna performance due to adhesion of water droplets even in rainy weather.

In addition, in the embodiment shown in Fig. 4, one antenna is used for transmission and reception that requires a wide band, and the other antenna is used as a diversity antenna for a car phone, which is used for reception without any problem even in a relatively narrow band. It is possible to provide suitable performance.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of one embodiment of the present invention, Fig. 2 is a view of another embodiment of the upper surface of the case, Fig. 3 is a perspective view and a sectional view of another embodiment of the invention, and Fig. 4 is a main A sectional view of still another embodiment of the invention, FIG. 5 is an example of a circular antenna, FIG. 6 is an example of a case housing one circular antenna, and FIG. 7 is an example of a case housing two circular antennas.
FIG. 8 is a diagram of a conventional case accommodating two circular antennas, and is a characteristic diagram showing changes in antenna characteristics due to adhesion of water droplets. <Explanation of symbols> 15, ]6.Circular antenna 19.30.33...Case 20...Circular hole 21.31...Mounting is done at base 22.Slit 23..Side plate

Claims (1)

[Claims] What is claimed is: 1. An antenna case for housing a plurality of circular antennas arranged in a plane, the antenna case comprising a mechanism for removing water droplets adhering to the top surface of the antenna case.