JPH0756490Y2 - Planar antenna device - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat antenna device, and more particularly to a dew condensation preventing structure for a flat antenna device for receiving satellite broadcasting.

[0002]

2. Description of the Related Art In a planar antenna device for receiving satellite broadcasting, a microstrip antenna is often formed on a dielectric substrate to receive SHF radio waves.

[0003] For this type of planar antenna device is intended to be used primarily installed outdoors, radiation
If the element is exposed, rain or the like will be generated on the surface of the radiating element.
Water drops on the element surface or the element surface gets wet due to condensation etc.
Loss, the antenna radiation
It changes when the reactance component of the impedance changes.
It causes a mismatch in the force impedance and reduces the gain.
It will be. To avoid this situation,
A cover made of a low-loss dielectric material with excellent weather resistance ("red
(Also referred to as "home") to cover the antenna surface.
It Such a cover improves the transmission of radio waves,
Normally the thickness is less than 0.05λ (λ: wavelength of target frequency)
Although a thin cover of
In case of potential loss, single layer red with a thickness of about λ / 2
Use expensive materials such as frames and multilayer sandwich radomes.
Sometimes However, when using a thin cover,
Attach the cover in close contact with the surface of the cross trip element
Then, the reactance component of the antenna element changes.
Or even water drops on the surface of the cover, or
Causes deterioration of electrical performance due to surface wetting, etc.
In general, the distance between the antenna element surface and the cover is λ / 4 ~
Cover with a gap of a certain distance (d) of about λ / 2
Mounting. The distance d of this constant gap is
The type of antenna element such as
Depending on the bar thickness, material, etc.,
Allowable value for deterioration of electrical performance due to bar mounting and cover surface
Determined by the allowable value of electrical performance deterioration due to raindrop adhesion
Therefore, the effect can be tolerated by experiments for each antenna.
Each time, the intervals are set to be as small as possible.
This makes the whole antenna small, lightweight and low cost
This is because. By the way, of the flat antenna for satellite broadcasting reception
In this case, the constant gap distance d is usually about λ / 2.
In general, the degree is about 10 mm.
It is widely adopted.

[0004]

However, due to the above reasons, there is a certain distance between the antenna element and the cover.
If a gap is provided by d, the gap is simply
In the structure with only an air layer, the temperature difference between outside and day
Condensation is generated inside due to, etc., and as a result, the antenna element surface
An antenna that does not use the above-mentioned cover because water drops adhere to the antenna
As in the case where the element is exposed, the reception performance is degraded.
There was a problem of twisting .

The present invention has been made in view of the above situation, and an object thereof is to reduce deterioration of reception performance due to dew condensation in addition to rain and snow when used outdoors. It is to provide a planar antenna device capable of

[0006]

That is, the present invention provides, for example, λ / between a plane antenna mounted on an antenna mounting plate and an antenna cover for covering the plane antenna.
A constant gap of about 4 to λ / 2 (λ: wavelength of target frequency)
In addition, a gap holding member made of a dielectric material such as foamed plastic having a small radio wave loss is interposed so as to be in close contact with the radiation surface of the antenna cover and the planar antenna.

With such a structure, it is not affected by rain, snow and the like, and even if dew condensation occurs between the planar antenna and the antenna cover covering it, the water content thereof directly contacts the antenna surface. Since it does not adhere, deterioration of reception performance can be greatly reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 1 (a) and 1 (b), an SH having a microstrip antenna is formed on the antenna mounting plate 11.
An F reception antenna 12 is installed. The SHF wave received by the SHF receiving antenna 12 is transmitted through the waveguide 13 attached to the back side of the antenna mounting plate 11, and the converter 14 connected to the waveguide 13 is further transmitted.
Is converted to UHF wave at.

An antenna cover 15 made of, for example, plastic is mounted on the antenna mounting plate 11 with a gap a between the surface of the SHF receiving antenna 12 and the surface, as shown in FIG. Even if rain or snow adheres to the surface, the reception performance does not deteriorate significantly.

A plate-shaped gap holding member 16 is sandwiched inside the antenna cover 15, that is, in the gap a between the antenna cover 15 and the radiation surface of the SHF receiving antenna 12. The gap holding member 16 is formed of a dielectric material such as foamed plastic having a small radio wave loss.

In the flat antenna device having such a structure, even if rain or snow adheres to the antenna cover 15, rain attached to the radiation surface of the SHF receiving antenna 12
Since an appropriate gap a is provided between snow and the like, it is possible to prevent a large deterioration of the reception performance, and since the gap holding member 16 is interposed in this gap a, the air component is not generated. It is very small, and dew condensation that deteriorates the reception performance is unlikely to occur. Therefore, the deterioration of the reception performance can be further reduced.

[0013]

[0014]

[0015]

As described above, according to the present invention, it is possible to prevent the influence of dew condensation in addition to rain and snow when it is used outdoors, and it is possible to provide a planar antenna device with improved reception performance.

[Brief description of drawings]

FIG. 1 is a partially cutaway view of a planar antenna device according to an embodiment of the present invention.

[Explanation of symbols]

11 ... Antenna mounting plate, 12 ... SHF receiving antenna, 1
3 ... Waveguide, 14 ... Converter, 15 ... Antenna cover, 16, 16 '... Gap holding member.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuzo Kobayashi 1406 Hasunuma, Omiya City, Saitama Prefecture Yagi Antenna Co., Ltd. Omiya Factory (56) Reference JP-A-59-108404 (JP, A) (JP, U) Actually open Sho 59-91016 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. An antenna mounting plate, a planar antenna installed on one surface of the antenna mounting plate, an antenna cover mounted on the antenna mounting plate and covering the planar antenna with a constant gap from a radiation surface of the planar antenna. When formed of a dielectric material, the antenna interposed the gap between the antenna cover and the radiation surface of the planar antenna
A planar antenna device comprising: a cover and a gap holding member for preventing dew condensation, which is in close contact with the radiation surface of the planar antenna.