JPH0722834A - Dielectric lens for antenna and its production - Google Patents

Abstract

PURPOSE:To reduce the weight and to prevent the occurrence of defects such as shrinks, whirl marks, and voids by constituting a dielectric lens for antenna of a radome formed to a shell body having a prescribed dome shape and an expanded body which is stored in this radome and has a prescribed dielectric constant. CONSTITUTION:A radome 1 is formed to the shell body having the prescribed dome shape, and an expanded body 10 has the same outside form as the inside form of the radome and has such shape that it is fitted into the radome without spaces. With respect to the expanded body 10, polymer particles of a polystyrene are impregnated with an aliphatic hydrocarbon like a pentane and are subjected to pre-expansion in the water dispersion system of an autoclave. They are thrown into a mold and are subjected to expansion molding. The inside face of the mold has the same shape as the outside form of the radome 1, and the expanded body 10 formed by expansion molding is finished into such shape that it is fitted to the radome 1 without spaces. Meanwhile, the radome 1 and a cover member 5 are formed thin by a polystyrene. The expanded body 10 is stored in the radome and the cover member 5 is attached to the aperture part to complete the dielectric lens for antenna.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a dielectric lens, especially
The present invention relates to a dielectric lens used as a microwave receiving antenna element for communication and broadcasting.

[0002]

2. Description of the Related Art Conventionally, a dielectric lens used as an antenna element for receiving microwaves of 5 GHz or higher is obtained by mixing a resin material such as polypropylene, polyethylene or polystyrene with a foaming agent and a ceramic powder as a dielectric constant adjusting agent. A dome-shaped product is provided. In this case, the surface portion of the lens is solidified to form a radome layer. This radome layer functions as a protective layer for reinforcing the weather resistance and strength of the foam.

However, since the conventional dielectric lens is molded thickly, there is a problem that the weight is inevitably increased. For example, using polypropylene, the diameter is about 1
When formed into a dome shape of 80 mm and height of about 76 mm,
It weighs about 1 kg. In addition, the amount of resin used increases and the cost increases. On the other hand, since the molding is performed to be thick, defects such as sink marks and swirl marks are generated on the surface of the molded body (radome layer), and voids are generated inside. By using the injection compression molding method, defects of this kind can be prevented considerably. However, in injection compression molding, the mold structure is complicated and the equipment cost is high, and it is difficult to reliably prevent sink marks, swirl marks, and voids. Furthermore, residual stress is unavoidably left on the molded product, which causes deformation.

[0004]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an inexpensive dielectric lens which is lightweight and does not cause defects such as sink marks, swirl marks and voids. Further, it is an object of the present invention to provide a method for manufacturing a dielectric lens which has simple steps and does not require expensive equipment.

In order to achieve the above object, a dielectric lens according to the present invention comprises a radome molded into a shell having a predetermined dome shape, and a foam body housed in the radome and having a predetermined dielectric constant. Consists of. The foam is once pre-foamed into a bead state. When such pre-expanded beads are used as they are, the pre-expanded beads are filled in a predetermined amount in the radome, and the radome is closed. Alternatively, the pre-expanded beads are put into a mold and fusion-molded into a foam having an outer shape substantially equal to the inner shape of the radome. Then, the fusion-molded body is housed in a radome and closed with a lid member.

In the present invention, since the radome and the foam are separately molded, sink marks, swirl marks, and voids do not occur as compared with the conventional integrally molded product. Further, since the foamed body is pre-foamed into a bead state, the amount of the resin material is small and the weight is light.
Further, the radome is an ordinary thin-walled injection molding and the foam is an ordinary foamed molding, so that the equipment and the like are less expensive than the injection compression molding using a special mold.

[0007]

EXAMPLES Examples of a dielectric lens and a method of manufacturing the same according to the present invention will be described below with reference to the accompanying drawings. 1 and 2, 1 is a radome, 5 is a lid member,
10 is a foam. The radome 1 is formed into a shell having a predetermined dome shape. The foam 10 has the same outer shape as the inner shape of the radome 1 and is shaped to fit into the radome 1 without a gap.

The foam 10 is manufactured by the following steps. First, polystyrene is impregnated into polymer particles in a water dispersion system of an autoclave with an aliphatic hydrocarbon such as hexane, butane, pentane, etc., and a dielectric constant-adjusting agent is mixed in to pre-foam. In this pre-expansion, polystyrene is molded into beads. Next, the pre-expanded beads are put into a mold and fusion molding is performed. The inner surface of the mold has the same shape as the outer shape of the radome 1, and the fusion-molded foam 10 is finished into a shape that fits into the radome 1 without a gap. on the other hand,
The radome 1 and the lid member 5 are thinly molded from the same polystyrene as the foam 10 by a conventionally known method such as injection molding.

The foam 10 is housed in the radome 1,
The lid member 5 is attached to the opening of the radome 1 to complete the dielectric lens. It is preferable that the radome 1 and the lid member 5 are bonded to each other by using an adhesive agent or by ultrasonic welding. Further, it is preferable that the radome 1 is thin from the viewpoint of lens efficiency, and the thickness thereof is 2 mm or less, preferably 1 mm or less. Further, in terms of lens efficiency, it is preferable that the gap between the radome 1 and the foam 10 is 0.5 mm or less. In addition, the radome 1 is prepared by mixing pigments such as titanium oxide.
If you mold the foam, it can absorb ultraviolet rays and
It is advantageous in maintaining the characteristics of 0 and extending the life.

An example of the components of the foam 10 is as follows. Resin: polystyrene, 100 parts by weight Dielectric constant adjusting agent: calcium titanate, 60 parts by weight Foaming agent: butane Pre-foaming was performed using the above materials at a foaming ratio of 15 times, and further fusion molding was performed to obtain a relative dielectric constant of 1 .5, weight 250g
It was possible to obtain Foam 10.

On the other hand, without manufacturing the foam 10 by fusion-molding the pre-expanded beads, the pre-expanded beads are filled in the radome 1 in the form of particles and closed by the lid member 5 to form a dielectric lens. You can also

The dielectric lens and the method of manufacturing the same according to the present invention are not limited to the above-mentioned embodiments, but can be variously modified within the scope of the gist thereof. In particular, the radome 1, the lid member 5 and the foam 10 may be made of any material, such as polystyrene, polypropylene or polyethylene as the resin material, butane or pentane as the foaming agent, and titanic acid as the dielectric constant adjusting agent. Calcium, barium titanate, etc. can be used.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a dielectric lens according to the present invention.

FIG. 2 is a cross-sectional view of the assembled state of FIG.

[Explanation of symbols]

 1 ... radome 5 ... lid member 10 ... foam

Claims (4)

[Claims] 1. A dielectric lens for an antenna, comprising: a radome formed into a shell having a predetermined dome shape; and a foam body having a predetermined dielectric constant and housed in the radome. 2. The dielectric lens for an antenna according to claim 1, wherein an ultraviolet absorber is mixed in the radome. 3. A step of forming a radome into a shell having a predetermined dome shape, a step of forming a large number of foam particles so as to have a predetermined dielectric constant, and the step of forming the foam particles inside the radome. A fusion-molding step so as to have a dome shape substantially equal to the shape; and a step of accommodating the fusion-formed foam in the radome and attaching a lid member to the opening of the radome. A method of manufacturing a dielectric lens for a characteristic antenna. 4. A step of forming a radome into a shell having a predetermined dome shape, a step of forming a large number of foam particles so as to have a predetermined dielectric constant, and a predetermined amount of the foam particles in the radome. A method of manufacturing a dielectric lens for an antenna, comprising: filling and attaching a lid member to the opening of the radome.