Patent Grant
7667667
This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/JP2005/010176, filed on Jun. 2, 2005, the disclosures of which Application is incorporated by reference herein.
The present invention relates to a radio wave lens antenna adopting a Luneberg lens used for receiving and transmitting radio wave from and to communications satellites, antennae installed on the ground and the like.
As a radio wave lens for an antenna device, there is known one that uses a Luneberg lens. The Luneberg lens is a spherical lens made of dielectric material, wherein the relative dielectric constant varies within a range from 2 to 1 or its approximate value from the center of the sphere to the outer periphery. Further, there is another type of Luneberg lens that achieves the function equivalent to that of the spherical lens by combining a hemispherical lens with a radio wave reflector having a greater size than the hemispherical lens (see, e.g., Patent Document 1).
Since the radio wave lens antenna disclosed in Patent Document 1 uses a hemispherical lens, and therefore, the size can be reduced and the cost can be saved compared to the case of using a spherical lens. However, since it is configured such that its entire parts are covered with a radome for protection, the size becomes large. Further, and the radome of a hollow structure must have a large thickness to secure a sufficient strength, which causes problems in electric characteristics and an increase in cost.
Regarding this, in the radio wave lens antenna of the structure disclosed in Patent Document 1, a lens cover of a hemispherical shell shape may be used such that the lens is sealed by the lens cover and a reflector. Since the lens cover is in contact with the surface of the lens, the size and the thickness can be made smaller. Thus, a further reduction in size can be achieved, and desirable electric characteristics can be acquired more easily compared to the antenna that uses a radome.
However, Patent Document 1 does not mention anything about the fixing and liquid sealing of the lens. The lens is usually fixed to the reflector by using an adhesive. However, the adhesive may be deteriorated after a long period of use, and thus the lens may be detached therefrom. Also, the lens may be removed due to an impact, wind pressure, bending of the reflector by vibration, or the like. In this case, a gap in which the dielectric constant differs from that of the lens may be formed between the lens and the reflector, thereby greatly degrading the electrical performance of the antenna device. Furthermore, when the adhered portion is peeled off while the lens cover is misaligned or damaged, there is a risk of the lens falling down.
Further, if the reflector is not properly sealed to the lens cover, rainwater, moisture or the like may penetrate the inside of the lens cover. Since water has a high dielectric constant (∈r) and a high dielectric loss (tan δ), merely a slight amount of moisture that has seeped into the lens may sharply degrade the electrical performance of the antenna device. However, Patent Document 1 does not disclose any solution to these problems.
Patent Document 1: Japanese Patent Application Publication No. 2002-232230
It is an object of the present invention to provide a radio wave lens antenna configured such that the electrical performance is not degraded and the lens does not fall down even if the adhesive between the lens and the reflector peels off, and water or moisture does not easily permeate into the lens cover.
To achieve the above object, in accordance with the present invention, a flange is formed at an opening edge of a lens cover, and arranged between a reflector and a plate that encircles a lens to fix the lens cover to the reflector. Further, a sealing is performed between the reflector and the lens cover is provided on a circumference centered at a center of the lens and having a diameter greater than that of the lens, and the plate is fixed to the reflector at a position located farther from the lens than the sealing part.
More specifically, in a radio wave lens antenna including a hemispherical Luneberg lens, a lens cover that covers the surface of the lens, a reflector for radio wave combined with the lens, a ring-shaped plate arranged along an outer circumference of the lens, a primary feed arranged at a focal point of the lens, and a holding part for the primary feed, the lens cover is fixed by arranging a flange formed at an opening edge thereof between the reflector and the plate, a sealing part that seals between the reflector and the flange is provided on a circumference centered at a center of the lens and having a diameter greater than that of the lens, and the plate is fixed to the reflector at a position located farther from the lens than the sealing part.
The plate may be divided into two or more parts in a circumferential direction. Particularly in case an inner peripheral surface of the plate has a part where an inner diameter thereof is smaller than an outer diameter of the lens cover, it is preferable to install the plate by dividing it into two or more parts.
A part of the lens cover may be brought in contact (preferably, a pressed contact) with the lens to have the lens fixed. In this case, the position of the contacting part between the lens and the lens cover is not particularly limited. However, when the lens cover is broken, the probability that a part of the lens cover survives is higher at a region closer to the surface of the reflector. Therefore, it is preferable that the lens cover is in contact with the lens at a region close to the reflector.
An inner peripheral surface of the plate may be sloped in a direction that a separation gap from the lens increases as moving towards a lower surface of the plate, such that a part where an inner diameter thereof is smaller than the outer diameter of the lens cover is formed at an upper portion or a central portion of the inner peripheral surface of the plate in the thickness direction, thereby fixing the lens to the lens cover by using the plate configured as such. Further, the inner peripheral surface of the plate may have a recessed or a projected portion recessed or projected in a direction of a lens diameter, such that the inner peripheral surface of the plate is fittedly inserted to the lens cover.
In an installation part of the plate, a reflection surface for radio wave may be provided by the upper surface of the plate. In case of using the upper surface of the plate as a part of the radio wave reflection surface, it is preferable that a step height between the reflection surface of the reflector and the upper surface of the plate is made as small as possible. It is preferable that the thickness of the plate is smaller than or equal to 1/10 of the wavelength of a received radio wave.
Further, it is also preferable to provide a structure in which the upper surface of the plate is maintained to be flat by clamping the plate to the reflector by a flat head screw; a structure in which the plate is formed of synthetic resin having a low dielectric loss and the reflection surface of the reflector is placed under the plate; and a structure in which the plate is buried in the reflector to reduce the step height between the plate and the reflector. In case of burying the plate in the reflector, the height of the upper surface of the plate can be aligned in the same plane as the reflection surface of the reflector.
Further, the plate may be formed of synthetic resin (including foam resin). The synthetic resin used as the material of the plate may preferably be polyolefin resin whose dielectric loss is small, such as polyethylene, polypropylene and polystyrene; or fluorine resin such as polytetrafluoroethylene.
Further, although the sealing between the lens cover and the reflector may be performed only by forming a flange therebetween, it would be more preferable that any of an O-ring, a packing, a sealant, and an adhesive are used for the sealing separately or in combination.
It is also preferable that the opening edge of the lens cover, together with the flange formed thereat, is inserted into the reflector, and the sealing between the lens cover and the reflector is carried out within the reflector.
It is also considerable that the reflector includes a first reflector on which the lens is mounted and a second reflector covering a part of the first reflector that encircles the lens, and the second reflector is also used as the plate. In this case, the overlapping part of the first and the second reflector can be regarded as an inside of the reflector so that the sealing part between the lens cover and the reflector is formed at the overlapping part.
In accordance with the radio wave lens antenna of the present invention, a flange is disposed at an opening edge of a lens cover between a ring-shaped plate and a reflector, so that the lens cover is fixed to the reflector. Thus, a clamping pressure is applied uniformly to each part of the flange, thereby preventing the thin lens cover from being damaged by a weight load concentrated on a part thereof.
In addition, the flange of the lens cover is uniformly pressed by a plate such that a sealing pressure is applied uniformly to a sealing part between the flange and the reflector. Thus, the reliability of sealing can be enhanced by a uniform sealing. Also, by fixing the plate at a position located more outwards in the direction of the lens diameter than the sealing part, water can be prevented from penetrating through the fixing portion of the plate.
Further, by dividing the plate into two or more parts in the circumferential direction, it is possible to make the lens cover pressed by the plate in the diametrical direction, and the lens can be located between the divided parts of the plate via the lens cover. Thus, falling-down of the lens can be prevented more effectively.
Further, the inner peripheral surface of the plate is sloped such that the inner diameter of the upper portion of the inner peripheral surface or the central portion of the plate in the thickness direction is made smaller than the outer diameter of the lens cover; or one or more projections are formed on the inner peripheral surface of the plate in the direction of the lens diameter such that the projections of the inner peripheral surface are fittedly inserted into corresponding portions of the lens cover. Thus, the plate is fixedly engaged with the lens cover such that, even when the adhesive is loosened, the lens remains fixed to the plate. Therefore, a displacement or falling-down of the lens does not occur easily.
In case of performing the sealing between the lens cover and the reflector within the reflector, it is possible not to dispose a component that influences the reflection of radio wave on the reflection surface of the reflector. With this structure, the radio wave is reflected in a normal manner over the entire parts of the reflection surface, so that the electrical performance of the antenna apparatus can be maintained without being degraded.
Further, by performing the sealing within the reflector, the antenna cover is prevented from being detached from the reflector, and a non-uniformity of sealing pressure at the sealing part is eliminated. Thus, the stability of sealing can be enhanced.
In case the flange at the opening edge of the antenna cover is arranged between the first and the second reflector to be fixed thereto, the sealability can be achieved by such an arrangement.
Further, in case the flange at the opening edge of the lens cover is arranged on the reflection surface of the reflector to perform the sealing, if a projected or recessed portion is formed as a stepped portion or hole (such as a water drainage hole) at the overlapped portion of the flange on the reflector, a gap is formed between the flange and the reflector by the projected or recessed portion, thereby making it difficult to perform a satisfactory sealing. However, this problem does not occur if the sealing is performed within the reflector.
Besides, in case the sealing is performed by using an O-ring, a packing, a sealant, an adhesive or the like separately or in combination, a more stable sealing can be achieved.
Hereinafter, embodiments of a radio wave lens antenna in accordance with the present invention will be described with reference to
The reflector 2, the lens 3, the lens cover 4 and the plate 5 is shown in
The reflector 2 has a greater size than the lens 3. This reflector 2 may preferably be formed of aluminum that is lightweight and low-priced, but may also be formed as a metal plate other than aluminum or a resin plate whose surface is metal-plated. An outer region of the reflector 2 located out of an attaching region at which the lens cover 4 is attached may be formed as a porous metal plate with small-sized holes (e.g., holes with a diameter of 1 mm or less) or a metal mesh plate with small-sized holes (of, e.g., 1 mm or less). In short, a surface with a proper flatness not to disturb the reflection of radio wave would be sufficient as a radio wave reflection surface.
The lens 3 is conventionally manufactured by a method in which each part of the lens is divided into multi layers in a diametrical direction and the relative dielectric constant is made to vary slightly in each of the layers. It would be proper that the relative dielectric constant of the lens manufactured by the conventional method varies stepwise in the diametrical direction.
The lens cover 4 is formed of synthetic resin. Any kinds of synthetic resin may be used as long as it has a small dielectric loss and a sufficient weatherability. However, it would be preferable to use hydrocarbon-based thermoplastic resin such as polyethylene, polystyrene, and polypropylene, whose dielectric loss is noticeably small. Further, it would be preferred that the thickness of the lens cover 4 is less than or equal to 1 mm in terms of a reduction in dielectric loss.
The plate 5, although whose material is not particularly limited, may preferably be formed of aluminum that is lightweight and low-priced as the reflector 2. The plate 5 can be configured such that an upper surface thereof is made as a reflection surface of radio wave; or such that radio waves can transmit through the plate 5. In the former case, the plate 5 can be formed of a material same as the reflector 2. However, in the latter case, it is preferable to form the plate 5 with a material having a small dielectric loss, e.g., the same material as that of the lens cover 4. An endless ring is used as the plate 5. Alternatively, the ring is divided into two or more parts in the circumferential direction to be used as the plate 5.
The thickness of the plate 5 whose upper surface is used as a reflection surface for radio wave may preferably be smaller than or equal to 1/10 of the wavelength of a received radio wave. In case the plate 5 is arranged on the reflector 2, it is preferable that the plate 5 is made as thin as possible within a range in which a required strength is secured, thereby reducing a height (hereinafter, referred to as “step height”) between the reflection surface of the reflector 2 and the upper surface of the plate 5 to be as small as possible. In this manner, adverse effects on the performance of the apparatus can be reduced. The step height may preferably be less than or equal to 1/10 of the wavelength of radio wave. With the structure as shown in
The primary feed 6, which is one referred to as an LNB (Low Noise Block), is provided at least one, and if necessary, plural in number to be positioned at the focal point of radio wave transmitted from, e.g., a geostationary satellite to communicate with.
The holding part 7 holds the primary feed 6 at the positioned point. As the holding part 7, it is possible to use well-known types of holder such as a pole bent along the surface of the lens or an arch-shaped arm.
In all of the radio wave lens antennae exemplified above, the flange 4a of the lens cover 4 is arranged between the reflector 2 and the plate 5 to fix the lens cover 4 to the reflector 2. Further, a sealing part 8 for sealing between the reflector 2 and the flange 4a is provided on a circumference whose diameter is greater than that of the lens, and the plate 5 is fixed to the reflector 2 by a clamping part 9 such as a bolt at a position spaced apart from the lens further than the sealing part 8.
A first embodiment of a structure for fixing the lens cover 4 to the reflector 2 is shown in
The hemispherical shell-shaped lens cover 4 is covered along the outer periphery of the lens 3, and the flange 4a formed at the opening edge of the lens cover 4 is attached onto the reflector 2. Then, the ring-shaped plate 5 is overlapped upon the flange 4a to be fixed to the reflector 2 by the clamping part 9, and the flange 4a is arranged between the plate 5 and the reflector 2 to fix the lens cover 4 to the reflector 2. Since at least a part of the lens cover 4 is in contact with the lens 3, the lens 3 is pressingly attached to the plate 2 via the lens cover 4, and, at the same time, the lens is fixed by the lens cover 4.
Further, in case of using the plate 5 divided into two or more parts in the circumferential direction such that the fixing position can be adjusted in the diametrical direction, the lens cover 4 can be pressed in the diametrical direction as well. By pressing the lens cover 4 in the diametrical direction as above, the lens 3 can be disposed diametrically between the divided parts of the plate 5 via the lens cover 4. Thus, even when a fixing surface 3a of the lens is detached and, in addition to this, the lens cover 4 is broken due to a deterioration of the adhesive 10, the lens 3 can be prevented from falling down by the clamping force of the plate 5.
In case of using the upper surface of the plate 5 as the reflection surface of radio wave, a flat head screw shown in
It can be considered that the sealing part 8 is configured to use only a clamping pressure applied by the reflector 2 and the plate 5 onto two surfaces of the flange 4a. However, it is preferable that a sealing agent 8a such as a silicon coating agent, sealant, adhesive or the like, is coated on an interface between the sealing part 8 and the reflector 2 to thereby enhance the sealability. The enhancement in sealability can also be achieved by a method of bonding the flange 4a to the reflector by a double sided adhesive tape that is waterproof, or inserting an O-ring (or packing) 8b between the reflector 2 and the flange 4a as shown in
The inner peripheral surface of the plate 5 may be formed in shapes as shown in
In the sixth embodiment of
In the seventh to ninth embodiments shown in
With this structure, the first reflector 2b serves as a pressing plate to fix the flange 4a of the lens cover arranged between the first reflector 2b and the second reflector 2c. Thus, there is no need to prepare an additional plate for pressing the flange 4a. In addition, in the same manner as the sixth embodiment shown in
Further, whereas a groove is formed on the first reflector 2b to provide an accommodating space for the flange 4a in the seventh embodiment shown in
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2005/010176 | 6/2/2005 | WO | 00 | 11/30/2007 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2006/129365 | 12/7/2006 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6462717 | Wheelock et al. | Oct 2002 | B1 |
| 7253789 | Kingsley et al. | Aug 2007 | B2 |
| 20020024477 | Foncin | Feb 2002 | A1 |
| 20060262031 | Kuroda et al. | Nov 2006 | A1 |
| 20070035468 | Kuroda et al. | Feb 2007 | A1 |
| Number | Date | Country |
|---|---|---|
| 3-70409 | Jul 1991 | JP |
| 6-021714 | Jan 1994 | JP |
| 9-223910 | Aug 1997 | JP |
| 2002-232230 | Aug 2002 | JP |
| 2005-51657 | Feb 2005 | JP |
| 2005-167692 | Jun 2005 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20090207095 A1 | Aug 2009 | US |
