Patent Publication Number: US-2022223992-A1

Title: Antenna apparatus

Description:
TECHNICAL FIELD 
     The present disclosure relates to an antenna apparatus having a heat dissipation structure. 
     BACKGROUND ART 
     In order to reduce air resistance, an antenna apparatus mounted on a mobile object such as an aircraft has a relatively small cross-sectional area as viewed from the heading direction of the aircraft (for example, see PTL 1). In the antenna apparatus in PTL 1, a phased-array method is used as a technique for reducing the height of the antenna apparatus in order to reduce the cross-sectional area as viewed from the heading direction. Further, in some phased array-type antenna apparatuses employ a heat radiation fin provided in a heat pipe as a heat dissipation structure for discharging heat from an antenna apparatus by air cooling (for example, see PTL 2). 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Patent Laying-Open No. 2003-298270 
     PTL 2: Japanese Patent Laying-Open No. 2016-539606 
     SUMMARY OF INVENTION 
     Technical Problem 
     A phased array-type antenna apparatus requires high heat dissipation performance due to increased heat generation density in its antenna unit. According to the antenna apparatus disclosed in PTL 1, however, since the antenna apparatus is mounted on a mobile object, the antenna unit is covered with a radome and not directly exposed to the outside air. Thus, for cooling the antenna unit, a cooling device such as a fan needs to be provided inside the radome, which causes a problem that it is difficult to reduce the height of the antenna apparatus. Also in the antenna apparatus disclosed in PTL 2, for cooling the antenna unit, a space accommodating a heat pipe needs to be provided inside the radome, which also causes a problem that it is difficult to reduce the height of the antenna apparatus. 
     The present disclosure has been made to solve the above-described problems, and an object of the present disclosure is to obtain an antenna apparatus that allows cooling with a high heat dissipation effect even when the antenna apparatus is reduced in height. 
     Solution to Problem 
     An antenna apparatus according to the present disclosure includes: an antenna element; a mount on which the antenna element is provided; a radome to accommodate the antenna element; and a skirt provided on the mount. The mount has a side surface including a surface attached to an inner circumferential surface of the radome. The skirt has an outer circumferential surface on which a heat dissipation fin to dissipate heat to outside is formed, the heat being transmitted from the antenna element through the mount to the skirt. 
     Advantageous Effects of Invention 
     The present disclosure can provide an antenna apparatus that allows cooling with a high heat dissipation effect even when the antenna apparatus is reduced in height. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of an aircraft equipped with an antenna apparatus according to a first embodiment. 
         FIG. 2  is a cross-sectional view of the antenna apparatus according to the first embodiment. 
         FIG. 3  is a top view of the antenna apparatus according to the first embodiment, from which a radome is removed. 
         FIG. 4  is an enlarged view of a portion where an antenna unit and a mount in the antenna apparatus according to the first embodiment are joined to each other. 
         FIG. 5  is a cross-sectional view of the mount of the antenna apparatus according to the first embodiment, in which a heat pipe is provided in the mount. 
         FIG. 6  is a cross-sectional view showing another configuration of the antenna apparatus according to the first embodiment. 
         FIG. 7  is a cross-sectional view showing another configuration of the antenna apparatus according to the first embodiment. 
         FIG. 8  is an enlarged cross-sectional view of a connection portion between a skirt and the mount in the antenna apparatus according to the first embodiment. 
         FIG. 9  is an enlarged cross-sectional view of the connection portion between the skirt and the mount in the antenna apparatus according to the first embodiment. 
         FIG. 10  is a top view showing another configuration of the antenna apparatus according to the first embodiment. 
         FIG. 11  is a diagram showing a flow of heat dissipation in the antenna apparatus according to the first embodiment. 
         FIG. 12  is a cross-sectional view of an antenna apparatus according to a second embodiment. 
         FIG. 13  is an enlarged cross-sectional view of a connection portion between a skirt and a mount in the antenna apparatus according to the second embodiment. 
         FIG. 14  is a diagram showing a flow of heat dissipation in the antenna apparatus according to the second embodiment. 
         FIG. 15  is a cross-sectional view of an antenna apparatus according to a third embodiment. 
         FIG. 16  is an enlarged cross-sectional view of a connection portion between a skirt and a mount in the antenna apparatus according to the third embodiment. 
         FIG. 17  is a diagram showing a flow of heat dissipation in the antenna apparatus according to the third embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The following describes embodiments in detail with reference to the accompanying drawings, in which the same or equivalent portions are denoted by the same reference characters. 
     First Embodiment 
       FIG. 1  is a side view of an aircraft  1  on which an antenna apparatus  100  according to a first embodiment is mounted. Antenna apparatus  100  is mounted on a mobile object. For example, when antenna apparatus  100  is mounted on aircraft  1  for satellite communication, antenna apparatus  100  is attached to a top surface portion of aircraft  1 . Although the figure shows an example of antenna apparatus  100  that is mounted on aircraft  1  in this case, antenna apparatus  100  may be mounted on another type of mobile object. When antenna apparatus  100  is mounted on another type of mobile object, antenna apparatus  100  is attached to a portion of the mobile object such as a top surface portion or a side surface portion, through which radio waves can be transmitted and received. 
       FIG. 2  is a cross-sectional view of antenna apparatus  100  according to the first embodiment. This cross section is perpendicular to a mounting surface of aircraft  1  on which antenna apparatus  100  is mounted.  FIG. 3  is a top view of antenna apparatus  100  from which a radome is removed. Antenna apparatus  100  includes an antenna unit  2  including an antenna element, a mount  3  on which antenna unit  2  is provided, a radome  4  to accommodate antenna unit  2 , and a skirt  5  provided on mount  3 . 
     Antenna unit  2  includes an antenna element that transmits or receives radio waves. The antenna element is formed of a receiving antenna  21  and a transmitting antenna  22 . In the present embodiment, the antenna element is formed of receiving antenna  21  and transmitting antenna  22 , but may be formed of one of receiving antenna  21  and transmitting antenna  22 . Further, the antenna element may have a configuration in which receiving antenna  21  and transmitting antenna  22  are integrated. 
     Receiving antenna  21  and transmitting antenna  22  of antenna unit  2  are provided on mount  3 . Each of receiving antenna  21  and transmitting antenna  22  includes a radio frequency integrated circuit (RFIC)  23 , a radio frequency (RF) substrate  24 , and an antenna base  25 . 
     RFIC  23  is provided on a surface of RF substrate  24 . RFIC  23  is a module for satellite communication for driving an active electronic scanning array. RF substrate  24  is a substrate on which RFIC  23  is mounted. RF substrate  24  functions to cause RFIC  23  mounted thereon to emit radio waves. Such an active electronic scanning array can direct radio waves in any direction through electronic scanning. Thus, antenna apparatus  100  includes RFIC  23  to thereby eliminate the need to operate antenna unit  2  by mechanical driving when antenna apparatus  100  directs radio waves in any direction in order to track a satellite and communicate with the satellite. 
     An antenna base  25  is provided between the antenna element and mount  3 . More specifically, antenna base  25  is provided between RFIC  23  of receiving antenna  21  and mount  3 . Similarly, antenna base  25  is provided between RFIC  23  of transmitting antenna  22  and mount  3 . Antenna base  25  is a member through which the heat generated from RFIC  23  and RF substrate  24  of antenna unit  2  is efficiently transmitted to mount  3 . Antenna base  25  is made of a metal material having high thermal conductivity, such as aluminum or copper. The heat transmitted from RFIC  23  and RF substrate  24  to antenna base  25  is diffused to the entire antenna base  25 . Since antenna base  25  is made of a metal material, mount  3  can be firmly supported even when antenna apparatus  100  receives a load from outside due to vibrations or the like. Thus, antenna base  25  also functions to prevent warping of RFIC  23  and RF substrate  24 . 
       FIG. 4  is an enlarged view of a portion where antenna unit  2  and mount  3  in antenna apparatus  100  according to the first embodiment are joined to each other. It is preferable that antenna base  25  and mount  3  are fastened in close contact with each other. Thus, heat loss can be reduced when the heat generated from RFIC  23  and RF substrate  24  is transmitted to mount  3 . It is preferable that the connection surface between antenna base  25  and mount  3  is processed so as to eliminate unevenness on the surface. Thereby, heat loss can be further reduced when the heat generated from RFIC  23  and RF substrate  24  is transmitted to mount  3 . Further, it is preferable to provide a thermal interface material (TIM) member  6  between antenna base  25  and mount  3 , as shown in  FIG. 4 . TIM member  6  serves as a member with which a small gap between antenna base  25  and mount  3  is filled. This can reduce the thermal resistance on the connection surface between antenna base  25  and mount  3 . 
     Mount  3  is a member serving as a plate for installing antenna unit  2  in aircraft  1 . Mount  3  is attached to aircraft  1  with an attachment bracket  7 . Mount  3  is made of a highly rigid metal material in order to prevent transmission of the influence of disturbances caused by a vibration load, a wind load or the like to antenna unit  2 . Further, since mount  3  made of a metal material has high thermal conductivity, the heat transmitted from antenna unit  2  can be diffused to the entire mount  3 . 
       FIG. 5  is a cross-sectional view of mount  3  of antenna apparatus  100  according to the first embodiment, in which a heat pipe  9  is provided in mount  3 . As shown in  FIG. 5 , mount  3  may have a configuration in which heat pipe  9  extends throughout mount  3 . As heat pipe  9  is provided in mount  3 , the heat transmitted from RFIC  23  and RF substrate  24  to antenna base  25  can be efficiently diffused to the entire mount  3 . Further, since heat pipe  9  provided in mount  3  is made of a metal material, mount  3  can be firmly supported even when antenna apparatus  100  receives an external load due to vibrations or the like. Therefore, warping of RFIC  23  and RF substrate  24  can also be prevented. 
     As shown in  FIG. 2 , mount  3  is a component having a first surface  31  and a side surface  32  that is connected to first surface  31 . Antenna unit  2  is provided on first surface  31  of mount  3 . More specifically, antenna base  25  of antenna unit  2  is provided on first surface  31  of mount  3 , and receiving antenna  21  and transmitting antenna  22  are provided on antenna base  25 . First surface  31  is an elliptical plate. Side surface  32  is a cylindrical portion having an inclined shape and is connected to the outer circumferential surface of first surface  31  to be inclined at an obtuse angle relative to first surface  31 . Side surface  32  of mount  3  has a diameter that decreases from an end portion opposite to an end portion connected to first surface  31  toward the end portion connected to first surface  31 . Accordingly, mount  3  has an elliptical shape when viewed from the top surface and has a trapezoidal shape when viewed from the side surface. 
     Mount  3  may have any shape. In this case, first surface  31  of mount  3  has a suitable elliptical shape but may have any shape such as a polygonal shape or a circular shape. For example, mount  3  may be a truncated conical member.  FIG. 6  shows mount  3  having a truncated conical shape. Mount  3  shown in  FIG. 6  has the same shape as mount  3  shown in  FIG. 2  except that no cavity exists. In this case, mount  3  is configured to have: a first surface  31 ; a second surface  33  opposite to first surface  31 ; and a side surface  32  connecting first surface  31  and the second surface. 
     Radome  4  is a component for protecting antenna unit  2  of antenna apparatus  100  from external environments such as hot air, cold air, rain, and wind from outside radome  4 . Radome  4  has a cylindrical shape having one closed end portion and the other open end portion. Further, radome  4  is formed to have an inclined side surface and to have a diameter that decreases from the open end portion toward the closed end portion. Radome  4  has a shape inclined along the shape of side surface  32  of mount  3 . As compared with a cylindrical shape without being inclined, mount  3  and radome  4  each having an inclined shape can reduce the external resistance and also can suppress transmission of the influence of disturbances caused by a vibration load and a wind load to antenna unit  2 . 
     Radome  4  is fixed to mount  3  with a fastening component  8 . A part of mount  3  is fitted into radome  4 . The inner circumferential surface of the open end portion of radome  4  is fixed to side surface  32  of mount  3 . Fastening component  8  is attached toward mount  3  from the outer circumferential surface side of radome  4 . Fastening component  8  is a member such as a bolt, a rivet or the like for fastening radome  4  and mount  3 . Countermeasures are taken against loosening of fastening component  8  that results from loads and vibrations occurring during flight of aircraft  1 . Radome  4  and mount  3  fixed in this manner prevents radome  4  from becoming detached from mount  3  even when aircraft  1  receives a load caused by disturbances while it is traveling. 
     In this case, the first surface of mount  3  is located inside radome  4 . An end portion of side surface  32  of mount  3  that is connected to first surface  31  is located inside radome  4 . An end portion of side surface  32  of mount  3  that is opposite to the end portion connected to first surface  31  is located outside radome  4 . In other words, a part of mount  3  is fitted into radome  4  while a part of mount  3  protrudes from radome  4 . Thereby, side surface  32  of mount  3  includes a surface to which the inner circumferential surface of radome  4  is attached and a surface located outside radome  4 . Further, when mount  3  shown in  FIG. 6  has a truncated conical shape, the end portion of side surface  32  of mount  3  that is connected to first surface  31  is located inside radome  4 . Also, the end portion of side surface  32  of mount  3  that is opposite to the end portion connected to first surface  31  is located outside radome  4 . Further, first surface  31  is located inside radome  4  while second surface  33  is located outside radome  4 . 
     In this case, a part of mount  3  is fitted into radome  4  and a part of mount  3  protrudes from radome  4 , but mount  3  may have another configuration.  FIG. 7  is a cross-sectional view of another configuration of mount  3 . For example, mount  3  may be entirely fitted into radome  4  as shown in  FIG. 7 . In  FIG. 7 , the first surface of mount  3  is located inside radome  4 . Side surface  32  of mount  3  is also located inside radome  4 . 
     Radome  4  is made of a material having a high dielectric constant and a large dielectric loss tangent and formed to have a predetermined thickness such that radio waves emitted from RF substrate  24  can pass through radome  4 . Further, radome  4  is made of a highly strong material such that it can protect antenna unit  2  from external environments such as a wind load and collision with foreign substances. 
       FIG. 8  is an enlarged cross-sectional view of a connection portion between skirt  5  and mount  3  in antenna apparatus  100  according to the first embodiment. Skirt  5  is a component with which the space between aircraft  1  and mount  3  is filled. Skirt  5  has a shape conforming to the shape of a portion of mount  3  to which skirt  5  is attached, and has a cylindrical shape conforming to the shape of side surface  32  of mount  3  in this case. Skirt  5  is provided to cover a surface of side surface  32  of mount  3  that is located outside radome  4 . More specifically, the inner circumferential surface of skirt  5  is attached in contact with the surface of side surface  32  of mount  3  that is located outside radome  4 . Skirt  5  and mount  3  are fixed with fastening component  8 . Fastening component  8  is attached from the outer circumferential surface side of skirt  5  toward mount  3 . Fastening component  8  is a bolt, rivet, or the like. 
     When mount  3  is entirely fitted into radome  4  as shown in  FIG. 7 , skirt  5  is provided on a surface of mount  3  that is located outside radome  4 . Other configurations of skirt  5  are the same as those in  FIG. 8 . In this case, skirt  5  is provided on a surface of mount  3  that is located outside radome  4 . However, skirt  5  may be preferably at least partially connected to mount  3  or may be provided on a surface of mount  3  that is located inside radome  4 , for example, between mount  3  and radome  4 . 
     The inner circumferential surface of skirt  5  is fastened to mount  3  with TIM member  6  interposed therebetween. This allows filling of the gap between skirt  5  and mount  3 , so that skirt  5  can be brought into close contact with mount  3 . The end portion of skirt  5  on the radome  4  side is connected to radome  4  so as to extend along the open end portion of radome  4 . The end portion of skirt  5  opposite to radome  4  is connected to aircraft  1  so as to extend along the curved surface of aircraft  1 . 
     Skirt  5  is attached to aircraft  1  with an elastic member  10  interposed therebetween. Elastic member  10  serves as a member with which a small gap between skirt  5  and aircraft  1  is filled. Elastic member  10  allows close contact between skirt  5  and aircraft  1 , so that the wind received by antenna apparatus  100  during flight of aircraft  1  can be prevented from entering the inside of antenna apparatus  100  through the gap between skirt  5  and aircraft  1  and thereby producing lift force. Further, elastic member  10  filling the space between aircraft  1  and skirt  5  can also prevent water from entering the inside of antenna apparatus  100  through the gap between skirt  5  and aircraft  1 . 
     As shown in  FIG. 8 , the connection portion between skirt  5  and radome  4  is configured to be a stepless continuous surface such that the outer circumferential surface of skirt  5  and the outer circumferential surface of radome  4  are continuous. This configuration can reduce the air resistance of antenna apparatus  100 . As shown in  FIG. 9 , the outer circumferential surface of skirt  5  may be located on an inner side than the outer circumferential surface of radome  4 . 
     Skirt  5  is made of a metal material having high thermal conductivity, like antenna base  25  and mount  3 . In order to increase the area that is in contact with cold air outside aircraft  1 , a heat dissipation fin  51  shaped to have slits is formed along the entire outer circumferential surface of skirt  5 . Heat dissipation fin  51  allows heat to dissipate from antenna unit  2  to the outside of antenna apparatus  100 . This structure allows skirt  5  itself to function as a heat sink. Thereby, the heat transmitted from mount  3  to skirt  5  can be released from skirt  5  to the outside of aircraft  1 . 
     Heat dissipation fin  51  formed in skirt  5  is provided with a plurality of slits in the circumferential direction of skirt  5 . The slits provided in the circumferential direction of skirt  5  extend in the direction corresponding to the traveling direction of aircraft  1 , thereby allowing more effective cooling. As described above, heat dissipation fin  51  formed in skirt  5  is suitably provided with slits in the circumferential direction of skirt  5 , but may be provided with slits extending in other directions or having other shapes, as required. The directions in which the slits extend and the shapes of the slits may be different depending on the position where heat dissipation fin  51  is provided. Further, heat dissipation fin  51  is formed along the entire outer circumferential surface of skirt  5  in this case, but may be provided only at a position as required. Heat dissipation fin  51  may be provided only on a part of the outer circumferential surface of skirt  5 , for example, as in a configuration in which heat dissipation fins  51  are provided only on both sides in the traveling direction of aircraft  1 , on which the heat dissipation efficiency is relatively high. 
       FIG. 10  shows another configuration of antenna apparatus  100  according to the first embodiment.  FIG. 10  is a top view of another configuration of antenna apparatus  100  from which radome  4  is removed. An arrow  11  in the figure indicates a traveling direction of aircraft  1 . In the figure, a diagonally shaded portion  53  in skirt  5  shows a portion made of a metal material. When the weight of antenna apparatus  100  needs to be taken into consideration, skirt  5  may be configured such that only diagonally shaded portions  53  on both sides with respect to the traveling direction of aircraft  1  as shown in  FIG. 10  are made of a metal material having high thermal conductivity and the portions other than diagonally shaded portions  53  are made of a lightweight material such as an elastic material. In this case, heat dissipation fin  51  is formed in diagonally shaded portion  53  of skirt  5 . Thereby, heat can be dissipated only from highly efficiently heat-dissipating portions on both sides in the traveling direction of aircraft  1 , and other portions can be made of a lightweight material, with the result that antenna apparatus  100  can be reduced in weight. 
       FIG. 11  is a diagram showing a flow of heat dissipation in antenna apparatus  100 . Arrows in the figure indicate the direction in which heat dissipates. The heat generated in transmitting antenna  22  and receiving antenna  21  is transmitted to antenna base  25 . The heat transmitted to antenna base  25  is diffused to the entire antenna base  25 , and then transmitted to mount  3  through TIM member  6 . The heat transmitted to mount  3  is diffused to the entire mount  3  and transmitted to skirt  5  through TIM member  6 . The heat transmitted to skirt  5  is finally released to the outside of radome  4  from heat dissipation fin  51  provided on the outer circumference of skirt  5 . 
     In this way, antenna apparatus  100  according to the present embodiment can efficiently transmit the heat generated in receiving antenna  21  and transmitting antenna  22  from mount  3  to skirt  5 . Further, skirt  5  itself can be used as a heat sink for heat dissipation. Thereby, the heat generated from the antenna unit can be efficiently dissipated to the outside of radome  4  without having to provide a cooling device such as a fan inside radome  4 . In particular, when antenna apparatus  100  is mounted on a mobile object such as aircraft  1 , antenna unit  2  is hermetically sealed by radome  4 , and therefore, not directly exposed to the outside air. Further, due to equipment constraints, it is difficult to release heat from antenna unit  2  to the body of aircraft  1 . Since the heat inside radome  4  can be dissipated from skirt  5  even in such a case, antenna apparatus  100  is not increased in size. Further, the wind flowing around aircraft  1  during flight or the cold air above aircraft  1  can be used for cooling antenna apparatus  100 . 
     Second Embodiment 
       FIG. 12  is a cross-sectional view of an antenna apparatus  200  according to a second embodiment.  FIG. 13  is an enlarged cross-sectional view of a connection portion between skirt  5  and mount  3  in antenna apparatus  200  according to the second embodiment. Antenna apparatus  200  is different from antenna apparatus  100  according to the first embodiment in configuration of mount  3  and skirt  5 . Other configurations are substantially the same. In the following, the same or corresponding configurations as those described in the above embodiment will be denoted by the same reference characters, and the description thereof will not be repeated. 
     In antenna apparatus  200  according to the second embodiment, mount  3  and skirt  5  are integrally formed. Mount  3  and skirt  5  are made of the same material. Skirt  5  and mount  3  are made of a metal material having high thermal conductivity. As in antenna apparatus  100 , heat dissipation fin  51  shaped to have slits is formed along the entire outer circumferential surface of skirt  5  in order to increase the area of contact with the cold air outside aircraft  1 . This structure allows skirt  5  itself to function as a heat sink. Thereby, the heat transmitted from mount  3  to skirt  5  can be released from skirt  5  to the outside of aircraft  1 . 
     Heat dissipation fin  51  formed in skirt  5  is provided with a plurality of slits in the circumferential direction of skirt  5 . Since the slits are provided in the circumferential direction of skirt  5 , these slits in heat dissipation fin  51  provided on each of both sides with respect to the traveling direction of aircraft  1  extend in the direction corresponding to the traveling direction of aircraft  1 , thereby allowing more effective cooling. As described above, heat dissipation fin  51  formed in skirt  5  is suitably provided with slits in the circumferential direction of skirt  5 , but may be provided with slits extending in other directions or having other shapes, as required. The directions in which the slits extend and the shapes of the slits may be different depending on the position where heat dissipation fin  51  is provided. In this case, heat dissipation fin  51  is formed along the entire outer circumferential surface of skirt  5 , but may be provided only at a position as required. Heat dissipation fin  51  may be provided only on a part of the outer circumferential surface of skirt  5 , for example, as in a configuration in which heat dissipation fins  51  are provided only on both sides in the traveling direction of aircraft  1 , on which the heat dissipation efficiency is relatively high. Further, mount  3  and skirt  5  may be integrally formed only in a portion of skirt  5  that is provided with heat dissipation fin  51 . 
     Further, as in antenna apparatus  100 , when the weight of antenna apparatus  200  needs to be taken into consideration, skirt  5  may be configured such that only portions on both sides with respect to the traveling direction of aircraft  1  are made of a metal material having high thermal conductivity, and other portions are made of a lightweight material such as an elastic material. In this case, heat dissipation fin  51  is formed in a portion of skirt  5  that is made of a metal material. In antenna apparatus  200 , mount  3  and skirt  5  are integrally formed only in a portion of skirt  5  that is made of a metal material. Thereby, heat can be dissipated only from highly efficiently heat-dissipating portions on both sides in the traveling direction of aircraft  1 , and other portions can be made of a lightweight material, with the result that antenna apparatus  200  can be reduced in weight. 
       FIG. 14  is a diagram showing a flow of heat dissipation in antenna apparatus  200 . Arrows in the figure indicate the direction in which heat dissipates. The heat generated in transmitting antenna  22  and receiving antenna  21  is transmitted to antenna base  25 . The heat transmitted to antenna base  25  is diffused to the entire antenna base  25 , and then transmitted to mount  3  through TIM member  6 . Then, the heat transmitted to mount  3  is diffused to the entire mount  3  and transmitted to skirt  5  through TIM member  6 . The heat transmitted to skirt  5  is finally released to the outside of radome  4  from heat dissipation fin  51  provided on the outer circumference of skirt  5 . 
     Even in antenna apparatus  200  configured as described above, the heat generated from receiving antenna  21  and transmitting antenna  22  can be efficiently transmitted from mount  3  to skirt  5 . Further, skirt  5  itself can be used as a heat sink for heat dissipation. Thus, the heat generated from the antenna unit can be efficiently dissipated to the outside of radome  4  without having to provide a cooling device such as a fan inside radome  4 . In particular, when antenna apparatus  100  is mounted on a mobile object such as aircraft  1 , antenna unit  2  is hermetically sealed by radome  4 , and therefore, not directly exposed to the outside air. Further, due to equipment constraints, it is difficult to release heat from antenna unit  2  to the body of aircraft  1 . Since the heat inside radome  4  can be dissipated from skirt  5  even in such a case, antenna apparatus  100  is not increased in size. Further, the wind flowing around aircraft  1  during flight or the cold air above aircraft  1  can be used for cooling antenna apparatus  100 . 
     Further, since mount  3  and skirt  5  are integrally formed, the performance for heat dissipation in transmitting heat from mount  3  to skirt  5  can be improved as compared with antenna apparatus  100 . Further, mount  3  and skirt  5  do not have to be fixed with fastening component  8 , and thereby can be easily assembled. Also, since fastening component  8  and TIM member  6  are not required, the number of components can be reduced. 
     Third Embodiment 
       FIG. 15  is a cross-sectional view of an antenna apparatus  300  according to the second embodiment.  FIG. 16  is an enlarged cross-sectional view of a connection portion between skirt  5  and mount  3  in antenna apparatus  300  according to the second embodiment. Antenna apparatus  300  is different from antenna apparatus  100  according to the first embodiment in configuration of radome  4  and skirt  5 . Other configurations are substantially the same. In the following, the same or corresponding configurations as those described in the above embodiments will be denoted by the same reference characters, and the description thereof will not be repeated. 
     In antenna apparatus  300  according to the third embodiment, a part of skirt  5  is formed integrally with radome  4 . A part of skirt  5  that is formed integrally with radome  4  is a metal block  52  made of a metal material. Metal block  52  is integrally molded with radome  4  at the stage of manufacturing radome  4 . As in antenna apparatus  100 , heat dissipation fin  51  shaped to have slits is formed along the entire outer circumferential surface of skirt  5  in order to increase the area of contact with the cold air outside aircraft  1 . Heat dissipation fin  51  shaped to have slits may be formed also in the portion of metal block  52 . This structure allows skirt  5  itself to function as a heat sink. Thereby, the heat transmitted from mount  3  to skirt  5  can be released from skirt  5  to the outside of aircraft  1 . 
     Heat dissipation fin  51  formed in skirt  5  is provided with a plurality of slits in the circumferential direction of skirt  5 . Since the slits are provided in the circumferential direction of skirt  5 , these slits in heat dissipation fin  51  provided on each of both sides with respect to the traveling direction of aircraft  1  extend in the direction corresponding to the traveling direction of aircraft  1 , thereby allowing more effective cooling. As described above, heat dissipation fin  51  formed in skirt  5  is suitably provided with slits in the circumferential direction of skirt  5 , but may be provided with slits extending in other directions or having other shapes, as required. The directions in which the slits extend and the shapes of the slits may be different depending on the position where heat dissipation fin  51  is provided. In this case, heat dissipation fin  51  is formed along the entire outer circumferential surface of skirt  5 , but may be provided only at a position as required. Heat dissipation fin  51  may be provided only on a part of the outer circumferential surface of skirt  5 , for example, as in a configuration in which heat dissipation fins  51  are provided only on both sides in the traveling direction of aircraft  1 , on which the heat dissipation efficiency is relatively high. 
     Further, as in antenna apparatus  100 , when the weight of antenna apparatus  200  needs to be taken into consideration, skirt  5  may be configured such that only portions on both sides with respect to the traveling direction of aircraft  1  are made of a metal material having high thermal conductivity, and other portions are made of a lightweight material such as an elastic material. In this case, heat dissipation fin  51  is formed in a portion of skirt  5  that is made of a metal material. Thereby, heat can be dissipated only from highly efficiently heat-dissipating portions on both sides in the traveling direction of aircraft  1 , and other portions can be made of a lightweight material, with the result that antenna apparatus  300  can be reduced in weight. 
       FIG. 17  is a diagram showing a flow of heat dissipation in antenna apparatus  300 . Arrows in the figure indicate the direction in which heat dissipates. The heat generated in transmitting antenna  22  and receiving antenna  21  is transmitted to antenna base  25 . The heat transmitted to antenna base  25  is diffused to the entire antenna base  25 , and then transmitted to mount  3  through TIM member  6 . Then, the heat transmitted to mount  3  is diffused to the entire mount  3  and transmitted to skirt  5  through TIM member  6 . The heat transmitted to skirt  5  is finally released to the outside of radome  4  from heat dissipation fin  51  provided on the outer circumference of skirt  5 . 
     Even in antenna apparatus  300  configured as described above, the heat generated from receiving antenna  21  and transmitting antenna  22  can be efficiently transmitted from mount  3  to skirt  5 . Further, skirt  5  itself can be used as a heat sink for heat dissipation. Thus, the heat generated from the antenna unit can be efficiently dissipated to the outside of radome  4  without having to provide a cooling device such as a fan inside radome  4 . In particular, when antenna apparatus  100  is mounted on a mobile object such as aircraft  1 , antenna unit  2  is hermetically sealed by radome  4 , and therefore, not directly exposed to the outside air. Further, due to equipment constraints, it is difficult to release heat from antenna unit  2  to the body of aircraft  1 . Since the heat inside radome  4  can be dissipated from skirt  5  even in such a case, antenna apparatus  100  is not increased in size. Further, the wind flowing around aircraft  1  during flight or the cold air above aircraft  1  can be used for cooling antenna apparatus  100 . 
     Further, metal block  52  as a part of skirt  5  is produced through integral molding with radome  4  at the stage of manufacturing radome  4 , thereby allowing the portion of radome  4  to also have a heat dissipation effect. According to this configuration, the performance for heat dissipation in transmitting heat from mount  3  to skirt  5  can be improved as compared with antenna apparatus  100 . 
     REFERENCE SIGNS LIST 
       1  aircraft,  2  antenna unit,  21  receiving antenna,  22  transmitting antenna,  23  RFIC,  24  RF substrate,  3  mount,  31  first surface,  32  side surface,  33  second surface,  4  radome,  5  skirt,  51  heat radiation fin,  52  metal block,  6  TIM member,  7  attachment bracket,  8  fastening component,  9  heat pipe,  10  elastic member,  11  traveling direction of aircraft,  100 ,  200 ,  300  antenna apparatus.