JP5263957B2 - Radome and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radome having high front/back performance. <P>SOLUTION: A conical radome (10) includes a conical portion including a core part (12) and skin layers (13) holding the core part therebetween and a flange (11) provided in an outer circumferential part of the conical portion. The conical radome includes a carbon cloth (14) covering at least the flange and a resin (16) covering the carbon cloth. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a radome that covers the front surface of a parabolic antenna having a circular opening surface, and a method for manufacturing the radome.

  In order to effectively use radio wave resources in recent years, antennas are required to improve radiation directivity, and more strict directivity standards are applied.

  In the case of terrestrial microwave links, in particular, discussions aimed at increasing the signal capacity of each line and reducing the interference between the lines were made for the purpose of effective utilization of radio resources accompanying the progress of line congestion and digitization. I came.

  With the digitization technique, the assigned frequency is further divided into multiple parts to realize an increase in signal capacity. On the other hand, there are various types of line interference. For example, there are interference due to unnecessary radiation behind the antenna and mutual interference between vertical and horizontal polarization signals when used in double polarization. Line interference is caused by radio waves radiated from the antenna. For this reason, it cannot be processed in the space on the line. As a result, in order to reduce line interference, it is necessary to take measures before radio waves are radiated from the antenna.

  Currently, antennas used for terrestrial microwave links are usually equipped with radomes, except in special installation environments (such as storage in buildings and chimneys).

  Many parabolic antennas are used for terrestrial micro lines. In this parabolic antenna, a radome is often attached to the reflecting mirror. Most radomes equipped with parabolic antennas have a conical shape. Such radomes are referred to in the art as conical radomes. Many of these conical radomes cover the front surface of a parabolic antenna having a circular opening surface, and the oblique side of the radome from the outer periphery of the reflector has an angle of about 30 °.

  In such an antenna with a conical radome, it is necessary to suppress the unnecessary radiation to the rear and to ensure a good radiation directivity front-to-back ratio (hereinafter referred to as “front-back ratio (FB ratio)”). For this reason, it is known that securing the FB ratio can be easily realized by winding a shielding plate around the outer peripheral portion (flange) of the antenna reflector.

  For example, Japanese Patent Laid-Open No. 2002-353723 (Patent Document 1) discloses a parabolic antenna with a radome in which a cylindrical shielding plate is provided on a flange portion of a radome. Japanese Patent Laying-Open No. 2003-218630 (Patent Document 2) discloses an antenna device in which a shielding plate is provided between a reflecting mirror or a main reflecting mirror and a radome.

  Japanese Patent Application Laid-Open No. 2003-142918 (Patent Document 3) shields a radio wave that causes unnecessary radiation from the surface of the outer periphery of the radome with a simple structure, and provides radiation directivity characteristics in a wide angle region with respect to the main beam radiation direction. An improved aperture antenna is disclosed. In the aperture antenna disclosed in Patent Document 3, a conductive member is formed over the entire circumference of the flange portion of the radome. If the radome does not require a conductive member, attach it only to the radome where the conductive member is required. Patent Document 3 describes that the conductive member is preferably carbon fiber.

JP 2002-353723 A (paragraph 0016, FIG. 1) JP 2003-218630 A (paragraph 0015, FIG. 4) JP 2003-142918 A (paragraphs 0009 to 0011, FIGS. 2 and 4)

  In the technique of winding the shielding plate around the outer periphery of the antenna reflector as disclosed in Patent Document 1 and Patent Document 2, the antenna shape is increased. As a result, wind resistance performance deteriorates and wind pressure load applied to the installation tower increases, and it is clear that it lacks superiority compared to an antenna equipped with a conical radome.

  When the aperture of the antenna is small, there are many cases where a shielding plate is provided and a resin radome is provided for ease of mass and structure, and unnecessary radiation can be easily suppressed. A radome for an antenna of several meters or more is generally shaped using FRP (Fiber Reinforced Plastic) containing glass fiber. However, the dielectric constant of the FRP material is larger than that of a resin such as Teflon (registered trademark) (approximately εr = 2), and has a thickness of approximately εr = 4. Control is required.

  In addition, the frequency band characteristics of the antenna are required to be a wide band, but a structure having a high dielectric constant and a thickness has a V-shaped reflection characteristic. For this reason, the radio wave radiated from the antenna opening surface is also affected by the difference in reflection characteristics within the frequency band due to the radome, and there is also a radio wave that propagates inside the radome. This propagation proceeds to the outer periphery of the radome, and is radiated from the outer periphery to the rear of the antenna as unnecessary radiation. As a result, a measure for satisfying the radiation directivity characteristic standard (hereinafter, referred to as high FB “front back”) provided for a large capacity antenna is required.

  In addition, from the viewpoint of electrical characteristics such as reflection characteristics, mechanical strength, and weight reduction, a radome often has a sandwich structure particularly in the case of an antenna having a large aperture. When this structure is adopted, it is essential to ensure mechanical manufacturing accuracy including electrical performance in order to suppress unwanted radiation. Therefore, selection of materials to be used and establishment of processing methods are also important issues.

  On the other hand, in the aperture antenna disclosed in Patent Document 3, the flange portion of the radome is covered with a conductive member (carbon fiber), and the conductive member (carbon fiber) is exposed to the outside. As a result, the conductive member (carbon fiber) may be peeled off.

  Therefore, the problem to be solved by the present invention is to provide a radome having a high front back performance and a method of manufacturing the same, which prevents such peeling.

  The conical radome of the present invention is a conical radome having a conical portion having a core portion and a skin layer sandwiching the core portion, and a flange provided on an outer peripheral portion of the conical portion, and at least the flange is provided. A carbon cloth for covering and a resin for covering the carbon cloth are provided.

  The flat radome of the present invention is a flat radome having a radome body having a core portion and a skin layer sandwiching the core portion, and a flange provided on an outer peripheral portion of the radome body. The flat radome includes a radome portion and a shroud provided between the flat radome portion and the flange. The flat radome includes a carbon cloth laminated on the shroud and a resin covering the carbon cloth.

  According to the present invention, since a carbon cloth is laminated on a shroud or covered with a resin and the carbon cloth is covered with a resin, a radome having high front back performance is provided while preventing the carbon cloth from peeling off. Can do.

It is a perspective view which shows the external appearance of the antenna apparatus equipped with the conical radome to which this invention is applied. It is a perspective view which shows the external appearance of the conical radome used for the antenna apparatus shown in FIG. It is a fragmentary sectional view of the conical radome shown in FIG. It is a fragmentary sectional view of the related conical radome which stuck the carbon cloth on the surface of the flange. It is a partial cross section which shows the conical radome which concerns on the 1st Embodiment of this invention. It is a fragmentary sectional view showing the conical radome concerning a 2nd embodiment of the present invention. FIG. 7 is a perspective view of the conical radome shown in FIG. 6. It is a fragmentary sectional view showing a conical radome concerning a 3rd embodiment of the present invention. It is a perspective view which shows the conventional antenna device which attached the shielding board. It is a figure which shows the radiation directivity characteristic of the antenna apparatus which attached the conical radome which is not applying this invention to the flange to the front surface of the reflective mirror of a parabolic antenna. It is a figure which shows the radiation directivity characteristic of the antenna apparatus which attached the conical radome which applied this invention to the flange to the front surface of the reflective mirror of a parabolic antenna. As shown in FIG. 9, it is a figure which shows the radiation directivity characteristic of the conventional antenna apparatus which provided the shielding board in the outer peripheral part of the reflective mirror. It is a perspective view which shows the external appearance of the flat radome to which this invention is applied. It is a fragmentary sectional view showing the flat radome concerning a 4th embodiment of the present invention. It is a fragmentary sectional view showing the flat radome concerning a 5th embodiment of the present invention. It is a fragmentary sectional view showing the flat radome concerning a 6th embodiment of the present invention.

  As described above, a radome is often attached to a reflecting mirror in a parabolic antenna used for a terrestrial microwave line or the like. In the present invention, the radome is used to improve the radiation directivity characteristics. In order to improve the characteristics, as a policy to minimize the influence of the antenna shape on the installation conditions, we examined the existing shape as much as possible and changed the radome (mainly used is the conical radome). We decided to respond without changing the shape. Since there is unnecessary radiation from the flange used for attachment to the reflecting mirror, which has an adverse effect on the radiation directivity, the present inventors have examined a countermeasure for the purpose of suppressing unwanted radiation.

  Here, in the present invention, a method of suppressing unnecessary radiation from the flange is selected by utilizing a characteristic that a carbon cloth or carbon mat in which carbon fibers are bundled has an effect equivalent to that of a metal reflector depending on the method of use. However, in order to attach and arrange these carbon materials so as to obtain improved characteristics, there is a technical problem for use as a radome, and the present invention has established the method.

  In other words, in the present invention, a method for reducing unnecessary radiation behind the antenna, which mainly affects line interference, is employed in the radome, and a method for improving its production efficiency has been invented. In addition, an antenna that can be installed without reinforcing the existing steel tower in strength has been realized by adopting a configuration equivalent to the existing antenna.

  In the present invention, a flange provided to be used for assembling the reflector on the outer periphery of the radome is covered with a woven fabric containing carbon fiber (hereinafter referred to as “carbon cloth”), thereby allowing the inside of the radome to be The electromagnetic wave propagating through the radome is suppressed from being emitted from the flange of the radome.

  Furthermore, by extending the stacking range of the carbon cloth on a part of the radome in the front direction of the reflector, radiation in the side direction of the antenna can be suppressed, and the front back performance can be further improved. is there.

  In the case of hand lay-up molding that has been conventionally used in the production of radomes, it is necessary to apply a FRP resin to cover the flange with a carbon cloth. On the other hand, the productivity is improved by realizing the formation of the radome body and the simultaneous lamination of the carbon cloth on the flange portion by a method using vacuum forming.

  In addition, in the process of manufacturing the radome flange, trimming such as shaving is performed in order to fit the manufacturing tolerance of the radome diameter. At the same time, carbon cloth is laminated in the FRP on the surface side of the flange, and at the same time, carbon fiber By using a material that is bundled in a felt shape (hereinafter referred to as carbon mat), the width of the carbon fiber can be increased in the diametrical direction near the outer periphery of the flange, making it difficult to lose carbon after trimming. This also improves workability and workability.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  An antenna device to which a conical radome according to the present invention is applied will be described with reference to FIGS.

  FIG. 1 is a perspective view showing an example of the appearance of a parabolic antenna device equipped with a conical radome. The illustrated parabolic antenna device includes a conical radome 10 and a reflecting mirror 20.

  As shown in FIG. 2, the conical radome 10 has a flange 11 and is fixed to the reflecting mirror 20 as shown in FIG.

  The conical portion of the conical radome 10 has a sandwich-shaped cross section as shown in FIG. 3 in terms of strength and mass. The conical portion of the conical radome 10 includes a core portion 12 and a skin layer 13 in which FRP resin is infiltrated into a glass cloth so as to sandwich the core portion 12. Further, the flange 11 of FIG. 3 is formed of FRP resin.

  FIG. 4 shows a cross section when the carbon cloth 14 is attached to the surface of the flange 11 in the antenna device related to the present invention. By sticking the carbon cloth 14 in this range, unnecessary radiation to the lower side of the antenna and the rear side of the antenna can be suppressed, and good directivity can be ensured.

  In the case of the flange 11 formed only by the FRP 16, in some cases, the outer diameter of the radome 10 is set within the tolerance, so that the diameter is determined by the flange portion, so that it may be necessary to trim the outer periphery. In this case, in the structure shown in FIG. 4, even the carbon cloth 14 wound around the outer periphery is scraped, and the carbon cloth 14 needs to be pasted again in a shortage range, which increases the number of work steps.

  FIG. 5 shows a cross-sectional view when the carbon mat 15 is used for forming the flange 11. In the structure of FIG. 5, by laminating using a carbon mat 15 having a width in the diameter direction, a layer containing carbon remains even if the outer peripheral portion of the flange is cut. For this reason, even if the trimming process is performed, the work of attaching the carbon cloth 14 does not occur, which is efficient.

  Here, as shown in FIG. 6, the carbon cloth 14 may be simultaneously laminated in the skin layer 13 in a partial area range of the radome 10. By this method, it is possible to further improve the wide-angle directional characteristics in the radiation directional characteristics without deteriorating the wind resistance performance due to the change in the shape of the parabolic antenna device.

  An example of a stacking range on the radome 10 at that time is indicated by a hatched portion in FIG. In FIG. 7, for example, when improving the directivity characteristics in the horizontal plane direction, there is an effect of improvement by arranging the stacking range of the shaded portion at the left and right positions of the antenna. In this case, in order to enhance the effect of suppressing unwanted radiation, the carbon cloth 14 laminated on the flange 11 and the carbon cloth 14 laminated on the radome surface must be in contact with each other without being continuous or having a gap. .

  The stacking range in FIG. 7 can also be realized by attaching a radio wave absorber to the inner surface of the radome. In that case, the radio wave absorber fixing method and the additional processing to the radome for fixing are required, and the productivity cannot be raised. However, since the carbon cloth 14 is laminated at the same time, no additional work is required, so that it can be realized only by the radome molding work.

  Next, the operation of the parabolic antenna device according to the first embodiment of the present invention will be described.

  As shown in FIG. 4, unnecessary radiated radio waves scattered to the rear of the parabolic antenna device can be suppressed by attaching or winding the carbon cloth 14 around the flange 11 of the radome 10.

  As shown in FIG. 8, by simultaneously laminating the carbon cloth 14 at the time of forming the radome 10 by the closed mold manufacturing method, the manufacturing time can be shortened, and the mechanism dimensional tolerance can be easily kept within a desired range. .

  As shown in FIG. 5, by using the carbon mat 15 to be laminated on the outer periphery of the radome 10, carbon fibers can be laminated while more efficiently filling the FRP, and at the same time, the desired dimensional tolerance can be realized. Is possible.

  As shown in FIGS. 6 and 7, in addition to the lamination to the flange portion, the carbon cloth 14 is also laminated in the radome surface, so that the conventional shielding plate 30 as shown in FIG. 9 is installed. A characteristic close to that of a parabolic antenna device can be obtained.

  When there is a radome 10 already manufactured, the carbon cloth 14 is covered so as not to generate a gap from the upper surface of the flange portion to the lower surface via the side surface. Since the carbon cloth 14 is a flexible material, it is easy to follow the curved portion or the uneven portion, and unnecessary portions can be easily formed with a blade. The carbon cloth 14 is made to conform to a desired pasting range in accordance with the shape, and FRP resin is applied thereon. At the same time as being cured by drying, the adhesive is applied to the flange 11 by utilizing the adhesiveness of the FRP, thereby realizing the suppression of unnecessary radiation covering the desired range.

  In the case of hand layup, the carbon cloth 14 and FRP resin are applied to the portion where the carbon cloth 14 is pasted to the flange using a molded radome, and the carbon cloth 14 is wound. Apply FRP resin for adhesion. However, in the case of these methods, after the carbon cloth 14 is bonded to the flange 11, it is necessary to treat the appearance.

  In the case of the hermetic molding method, when the foamed urethane of the core portion is arranged on the mold, it is spread in advance in the range where the carbon cloth 14 is laminated. At this time, by arranging the both sides of the flange 11 so as to cover both sides, the FRP resin can be soaked into the carbon cloth 14 at the same time when the FRP is filled. Molding can be performed.

  Further, assuming the effect of the shielding plate 30 (FIG. 9), unnecessary radiation can be suppressed by extending and laminating the carbon cloth 14 in a partial range on the front surface of the reflector of the conical radome 10. . The same effect can be obtained by attaching a radio wave absorber to the extended and laminated area, but it can be realized at a low cost by simultaneously laminating the carbon cloth 14.

  In actual production, when the diameter of the radome 10 is produced with higher accuracy, it is necessary to trim the outer peripheral portion of the flange 11. After forming with a mold, cut to fit the diameter within the desired tolerance. When this processing is performed, the thin carbon cloth 14 laminated on the outer peripheral portion has a portion to be scraped off, so that the effect of suppressing unnecessary radiation is lost. In order to prevent this, the outer periphery of the flange portion has a sandwich structure composed of only carbon fibers, and a carbon mat 15 having a width in the diametrical direction is provided on the outer periphery of the flange and sandwiched by a skin layer containing carbon cloth. Even when the cutting process is performed, a state in which a layer containing carbon is always present can be maintained.

  With reference to FIGS. 10 to 12, the present invention and the conventional radiation directivity characteristics will be described in order to explain the effects of the parabolic antenna device having the conical radome according to the present invention.

  FIG. 10 is a characteristic diagram showing an example of a radiation directivity characteristic in the case of a conventional parabolic antenna device having a conical radome to which the present invention is not applied at the flange portion. FIG. 11 is a diagram illustrating an example of radiation directivity characteristics in the case of the parabolic antenna device according to the first embodiment of the present invention. FIG. 12 is a characteristic diagram showing an example of radiation directivity characteristics in the case of a parabolic antenna device (FIG. 9) in which a conical radome is not used and a shielding plate 30 is provided on the outer periphery of the reflector for improving directivity characteristics. . 10 to 12, the horizontal axis indicates the angle (ANGLE) [DEG], and the vertical axis indicates the relative power (RELATIVE POWER) [dB] which is the FB ratio. 10 to 12, a dotted line 40 indicates a domestic radiation directivity characteristic standard. The reflecting mirror 20 uses a 90 ° opening (a structure in which the opening range of the reflecting mirror 20 viewed from the focal point of the reflecting mirror 20 is 90 ° with respect to the axial direction of the antenna). For this reason, when the radiation axis direction of the antenna is set to 0 °, a range up to 90 ° is a range mainly emitted from the reflecting mirror 20, and a range beyond 90 ° corresponds to the back side of the reflecting mirror 20.

  From FIG. 10, in the case of the conventional parabolic antenna device (in the case of the radome to which the present invention is not applied), the FB ratio can be secured up to a little over 60 dB with respect to the radiation level in the antenna axial direction in the range of 90 ° or more.

  From FIG. 11, in the case of the parabolic antenna device according to the present invention, the FB ratio can be secured up to about 70 dB. As a standard of the FB ratio currently applied in Japan, it is necessary to secure 65 dB or more in the range of 110 to 170 °, and by applying the present invention, a sufficient effect can be obtained. Can be confirmed.

  From FIG. 12, in the case of the parabolic antenna device shown in FIG. 9, the effect of suppressing the level of directivity can be confirmed even in the range of 90 ° due to the effect of the shielding plate 30. However, the performance of the FB ratio in the range of 90 ° or more is not significantly different from the case of the conical radome to which the present invention is applied as shown in FIG. 11, and the characteristics are secured without increasing the size of the antenna structure by applying the present invention. is made of.

  In the conical radome 10 used for a parabolic antenna or the like, a conical radome 10 having a flange 11 for attaching to a reflecting mirror 20 is generally used. In the present invention, focusing on the flange 11, a method for manufacturing the radome 10 for reducing the influence of the radio wave radiated from the flange end portion on the unnecessary rear radiation has been studied. The flange 11 of the radome 10 is usually in the form of a single FRP plate because of the need for securing strength at the time of attachment.

  The present invention is to suppress unnecessary radio waves radiated backward among the radiation directivity characteristics of an antenna. The carbon cloth 14 used here is flexible as a feature, and can be matched to the shape of the already molded part (the flange 11 of the radome 10). Therefore, the first point is that the electrical characteristics can be improved by covering the molded flange 11 with a shape that matches the shape. Affixing is possible by using FRP resin and applying the carbon cloth 14 together. In this case, it is also possible to affix to what is already molded, and remodeling work for improving characteristics is also possible.

  When forming using hand lay-up (a method in which FRP is manually applied using a lower mold), the carbon cloth 14 is attached by the same operation as described above.

  In addition, when using a hermetic molding method (a method in which an upper die and a lower die are used, and FRP is sucked between them to fill and mold), the carbon cloth 14 should be laid on the flange at the start of molding. Can be stacked simultaneously.

  Further, when molding is performed in the hermetic molding method, the outer peripheral portion of the flange 11 is trimmed in order to ensure the diameter of the radome 10 and final adjustment processing is performed. For this reason, there is a high possibility that the outermost carbon cloth 14 will be insufficient, but by applying the structure shown in FIG. 6 and laminating using a wide carbon mat 15, processing without losing the carbon portion. It becomes possible to do.

  Next, a parabolic antenna device according to another embodiment of the present invention will be described.

  A flat radome 10A used in a parabolic antenna device to which the present invention is applied will be described with reference to FIGS.

  FIGS. 13 to 16 are diagrams showing a case where a flat radome 10A having an FRP rising (hereinafter referred to as a shroud 17) from the outer periphery of the reflecting mirror is used as an application example using the carbon cloth 14. FIG. In that case, when the flat radome 10A is molded in the shroud 17, the carbon cloth 14 can be simultaneously laminated to have the same effect as the shielding plate, and the influence on the radiation directivity can be reduced. .

  FIG. 14 is a cross-sectional view when the carbon cloth 14 is laminated on the shroud 17 of the flat radome 10A. By this method, even when the molding is performed only by FRP, it is possible to have an effect equivalent to the shielding plate.

  Further, as shown in FIG. 15, a discharge measure (lead wire) 18 is provided on the carbon cloth 14 by welding or bonding 19 and is connected to a metal part such as the reflecting mirror 20 to be electrically connected. Unnecessary radiation can be further reduced by releasing the current induced by the radio wave arriving at the carbon cloth 14 portion to the metal portion.

  Further, as shown in FIG. 16, a carbon cloth 14 or a carbon mat 15 containing carbon fibers is provided on the flange 11 of the flat radome 10A in the same manner as the cross-sectional structures shown in FIGS. 6, 5, 4, and 8. By laminating, an improvement in front-back performance can be obtained.

  The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

  The present invention has been mainly aimed at improving the radiation directivity characteristics of the radome having a sandwich structure, but the shielding effect by the carbon cloth and the carbon mat can be applied even when the FRP is formed as a single layer. Is possible. The application method is not limited only to molding using a mold such as hand lay-up, and it is possible even when a single-molded material is used.

DESCRIPTION OF SYMBOLS 10 Conical radome 10A Flat radome 11 Flange 12 Core part 13 Skin layer 14 Carbon cloth
15 carbon mat
16 FRP (fiber reinforced plastic)
17 Shroud 18 Discharge cable (lead wire)
19 Welding or bonding 20 Reflector 30 Shield plate
40 National Radiation Directivity Standard

Claims (13)

In a conical radome comprising a conical portion having a core portion and a skin layer sandwiching the core portion, and a flange provided on an outer peripheral portion of the conical portion,
A carbon cloth covering at least the flange;
A resin covering the carbon cloth;
Conical radome characterized by having.   The conical radome according to claim 1, wherein the carbon cloth extends from a part of the conical portion.   The conical radome according to claim 1, wherein the resin is made of fiber reinforced plastic.   The conical radome according to any one of claims 1 to 3, wherein the flange has a carbon mat having a diametrical width. A method for manufacturing the conical radome according to claim 1, comprising:
Only the area where the carbon cloth is pasted is shaved,
Wrap the carbon cloth around the shaved part,
Covering the carbon cloth with the resin;
A method for manufacturing a conical radome.   The method for producing a conical radome according to claim 5, wherein the resin is made of fiber reinforced plastic. A method for manufacturing the conical radome according to claim 1, comprising:
When arranging the core parts, spread the carbon cloth,
Impregnating the resin with carbon cloth when filling the resin to form the skin layer and the flange;
A method for manufacturing a conical radome.   The method for producing a conical radome according to claim 7, wherein the resin is made of fiber reinforced plastic. A flat radome comprising a radome body having a core portion and a skin layer sandwiching the core portion, and a flange provided on an outer peripheral portion of the radome body, wherein the radome body includes a flat radome portion and the flat radome portion In the flat radome composed of a radome portion and a shroud provided between the flange,
A carbon cloth laminated on the shroud;
A resin covering the carbon cloth;
The flat radome characterized by having.   The flat radome according to claim 9, further comprising a discharge plan connected to the carbon cloth.   The flat radome according to claim 9 or 10, wherein the carbon cloth is also laminated on the flange.   The flat radome according to any one of claims 9 to 11, wherein the resin is made of fiber reinforced plastic. A method of manufacturing a flat radome according to claim 9,
A method for producing a flat radome, wherein the carbon cloth is laminated simultaneously when the radome body is molded.

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