JPH073926B2 - Dielectric lens for antenna - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dielectric lens, in particular, a dielectric lens suitable for an antenna.

[Prior Art and Problems] As a conventional dielectric lens, one made of Teflon is already known. Microwaves can be focused by forming a dielectric material such as Teflon like a convex lens of an optical system.

However, a dielectric lens using a resin such as Teflon has a small relative permittivity of the resin, and there is a problem that the lens thickness must be increased in order to obtain sufficient focusing of microwaves.

Therefore, it can be considered to use ceramics as the material of the dielectric lens to increase the relative permittivity. However, in that case, there is a problem that the dielectric lens becomes heavy because the specific gravity of the ceramic is large. In addition, when a large one is tried to be fired, there are disadvantages such that cracks are likely to occur.

Furthermore, in the conventional dielectric lens, as a method of reducing reflection on the lens surface, a method of coating a material having a dielectric constant that is the square root of the dielectric constant of the dielectric lens body with a thickness of about λ / 4 Is used. In that case, by mixing air bubbles or the like in the dielectric layer, the dielectric constant is adjusted to a desired value. However, this conventional configuration has a problem in that it is not easy to adjust the dielectric constant and accurate adjustment cannot be performed.

It is an object of the present invention to obtain a high dielectric constant, permit easy and accurate adjustment of the dielectric constant, and have a light weight, and a matching dielectric layer formed on the surface of the lens body. To provide a lens.

[Means for Solving the Problems] A dielectric lens for an antenna according to the present invention comprises: a lens main body formed of a mixture of fired powdery ceramics mixed with a resin at 10 to 90% by volume; A matching dielectric layer, which is formed on the surface and is composed of a mixture of fired powdery ceramics and resin, for reducing the reflection of radio waves on the lens surface.

[Operation] In the dielectric lens for an antenna according to the present invention, since ceramics is used in the lens body, it becomes possible to obtain a high dielectric constant, and it is possible to reduce the thickness of the lens. Further, since the lens body is made of a mixture of ceramics and resin, it is possible to obtain a lightweight dielectric lens as compared with the above-described improved example made of only ceramics. Moreover, by setting various mixing ratios of ceramics and resin, a dielectric lens having a desired dielectric constant can be easily obtained.

Moreover, since the matching dielectric layer is made of a mixture of ceramics and resin, the permittivity of the dielectric layer can be easily and accurately set by arbitrarily setting the mixing ratio.

[Example] FIG. 1 is a longitudinal sectional view of an example of a dielectric lens for an antenna according to the present invention. In FIG. 1, the dielectric lens main body 1 is formed in a shape similar to the convex lens of the optical system. A matching dielectric layer 2 is formed on the surface of the dielectric lens body 1 to reduce the reflection of radio waves on the lens surface.

The lens body 1 and the matching dielectric layer 2 are made of a mixture of fired powdery ceramics and resin. The permittivity of the matching dielectric layer 2 is set so as to substantially match the square root of the permittivity of the lens body 1. Further, since the lens body 1 and the matching dielectric layer 2 contain resin, it is possible to form a complicated shape or a large size by using a method such as injection molding.

As the material to be used, the following mixture of ceramics and resin can be considered. As ceramics, for example, SrTiO ₃ , CaTiO ₃ or BaO—Nd ₂ O ₃ —TiO ₂ system can be used. As the resin, Teflon, polystyrene, polyethylene, methylene pentene polymer, polyacetone, polypropylene, polycarbonate, polyphenylene sulfide, polybutylene, epoxy resin or the like can be used. The relative permittivity εr of CaTiO ₃ is about 18
0, the relative permittivity εr of SrTiO ₃ is about 260, BaO-Nd ₂ O ₃ -TiO ₂
The relative permittivity εr of the system is about 90. The relative permittivity εr of Teflon is about 2.2, the relative permittivity εr of polystyrene is about 2.6, and the relative permittivity εr of epoxy resin is about 4.5. FIG. 2 shows the relative permittivity εr obtained by combining these ceramics and resins at various mixing ratios. In FIG. 2, is a mixture of SrTiO ₃ and Teflon, is a mixture of SrTiO ₃ and an epoxy resin, is SrTiO ₃
And a mixture of polystyrene, a mixture of CaTiO ₃ and Teflon, a mixture of CaTiO ₃ and an epoxy resin, a Ca
TiO ₃ and a mixture of polystyrene, the BaO-Nd ₂ O ₃ -TiO ₂
With a mixture of Teflon, the mixture of BaO-Nd ₂ O ₃ -TiO ₂ and the epoxy resin, the volume ratio of the BaO-Nd ₂ O ₃ -TiO ₂ and a mixture of polystyrene - shows a relative dielectric constant relationship There is.

As is clear from FIG. 2, it is understood that the dielectric constant can be arbitrarily set over a wide range by changing the mixing ratio of ceramics and resin. Therefore,
It can be seen that the mixture of these ceramics and resins is useful not only for the dielectric lens body 1 but also for the matching dielectric layer 2.

Next, the change in relative permittivity of the dielectric lens using the mixture obtained by mixing CaTiO ₃ (specific gravity = 3.9 g / cm ³ ) and epoxy resin (specific gravity = 1.2 g / cm ³ ) 3 and the changes in the above are shown in FIG. As is clear from FIG. 3, the dielectric lens made of the mixture according to the present invention can be made lighter than the dielectric lens using 100% ceramics. For example, when a lens of 150.0 mm was formed using a mixture mixed so that the relative dielectric constant was 39, the lens weight was 208 g. On the other hand, the weight of the lens was 388 g when the same shape was formed by using 100% ceramics having a relative dielectric constant of 39.

Next, when the matching dielectric layer 2 having a dielectric constant suitable for the dielectric lens 1 is formed, for example, it is performed as follows. As a material for the dielectric lens 1, CaTiO ₃ and an epoxy resin were mixed at a volume ratio of 67:33, and the resulting mixture was used to form the dielectric lens 1. Then, as a material for the matching dielectric layer 2, CaTiO ₃ and epoxy resin are mixed at a volume ratio of 23:77, and the obtained mixture is used. In this case, as is clear from FIG. 3, the relative permittivity εr of the matching layer 2 substantially matches the square root value of the relative permittivity εr of the dielectric lens 1. Thereby, the matching dielectric layer 2 suitable for the dielectric lens 1 can be easily obtained.

When the relative permittivity of the dielectric lens 1 is 20 and the relative permittivity of air is 1, the relationship between the change in the permittivity of the matching dielectric layer 2 and the reflection loss in the case of vertical incidence is as follows. It became like Figure 4. FIG. 4 shows the relationship between the ratio of the permittivity of the matching dielectric layer 2 to the square root of the permittivity of the dielectric lens 1 and the reflection loss in the case of vertical incidence. The horizontal axis is the relative permittivity of the matching dielectric layer, which is standardized by the square root of the relative permittivity of the dielectric surface. As is clear from FIG. 4, if the error of the permittivity of the matching dielectric layer 2 is suppressed within ± 10% from the ideal value, the reflection loss can be suppressed to 0.5 dB or less.

Next, the characteristics of the antenna gain of the dielectric lens for an antenna according to the present invention will be described.

First, a mixture of CaTiO ₃ and an epoxy resin was used to form a dielectric lens having a relative permittivity εr of about 20.0. Then, the antenna gain of the dielectric lens was measured using the experimental apparatus as shown in FIG. In FIG. 5, 3 is an antenna using a dielectric lens according to an embodiment of the present invention, 4 is a standard gain horn for comparison, 5 is a spectrum analyzer for measuring received power, and 6 is a transmitting antenna. , 7 are oscillators. Using the apparatus shown in FIG. 5, the absolute value of the gain of the dielectric lens antenna 3 having the patch antenna as the primary radiator was obtained by comparing with the standard gain horn 4.

The results obtained are shown in Table 1.

Further, FIG. 6 shows frequency-gain characteristics of the antenna using the dielectric lens according to the example of the present invention. In FIG. 6, A is the characteristic of the antenna using the dielectric lens having the matching dielectric layer. B is the characteristic of the antenna using the dielectric lens having no matching dielectric layer. In addition,
C shows the characteristics of the conventional patch antenna alone. As is apparent from FIG. 6, the conventional patch antenna (C)
In addition, compared with the antenna (B) using the dielectric lens having no matching dielectric layer, the antenna (A) according to the present invention can obtain a larger gain.

Next, FIG. 7 shows an example in which the dielectric lens according to the present invention is applied to a satellite broadcast receiving antenna. Figure 7 shows
The outline of the satellite broadcast receiving system is shown. In FIG. 7, the high frequency signals of broadcast radio waves collected by the dielectric lens 10 are the primary radiator 11 and the LNA circuit 1 of the BS converter 12.
3 and 3 to the first mixing circuit 14. This first
In the mixing circuit 14, the local oscillation signal from the local oscillation circuit 15 is applied in the 10 GHz band. The first mixing circuit 14 converts the frequency of the high frequency signal based on the local oscillation signal and outputs the intermediate frequency signal IF ₁ in the 1 GHz band. Signal IF ₁ is a BS tuner
After being amplified by 16 IF amplifying circuits 17, it is given to the second mixing circuit 18. The second mixing circuit 18 is supplied with another local oscillation signal from the second local oscillation circuit 19. In the second mixing circuit 18, frequency conversion is performed again based on the local oscillation signal to generate a second intermediate frequency signal, and the IF filter 20
To enter. The intermediate frequency signal passed through the IF filter is
It is input to the FM detection circuit 21.

The dielectric lens according to the present invention can be effectively used as an antenna for receiving satellite broadcasting as shown in FIG. 7, for example.

[Effects of the Invention] According to the present invention, since the lens body is made of ceramics, the dielectric constant is increased, and the lens thickness can be reduced. Further, since the ceramic and the resin are mixed, the weight can be reduced and the moldability into the lens is improved as compared with the case where 100% ceramic is used. Further, since the ceramic and the resin are mixed, the dielectric constant can be easily and accurately adjusted. Therefore, the permittivity can be adjusted easily and accurately, and a lightweight and small antenna lens can be obtained.

Furthermore, according to the present invention, since the mixture of ceramics and resin is used as the matching layer, the permittivity of the matching layer can be easily and accurately adapted to the permittivity of the lens body. Therefore, it becomes possible to obtain a dielectric lens capable of exhibiting more excellent antenna gain characteristics.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a dielectric lens according to the present invention. FIG. 2 is a graph showing the relationship between the volume ratio and the relative dielectric constant. FIG. 3 is a graph showing the relationship between the volume ratio and the relative permittivity and specific gravity. FIG. 4 is a graph showing the characteristic of reflection loss when the matching dielectric layer is formed on the dielectric surface with a thickness of about λ / 4. FIG. 5 is a schematic diagram of a measuring device used for measuring the antenna gain characteristic. FIG. 6 is a graph showing the relationship between frequency and antenna gain. 7th
The figure is a schematic circuit diagram when the dielectric lens according to the present invention is used as a satellite broadcast receiving antenna. Reference numeral 1 is a dielectric lens body, and 2 is a matching dielectric layer.

Claims (1)

[Claims] 1. A sintered powdery ceramic is provided in an amount of 10 to 90.
A lens body made of a mixture mixed with resin at a volume%,
For an antenna, including a matching dielectric layer formed on the surface of the lens body, which is made of a mixture of fired powdery ceramics and resin to reduce the reflection of radio waves on the lens surface. Dielectric lens.