JP2010278695A - Antenna system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an miniaturized antenna system which prepares an antenna body for a lightning stroke. <P>SOLUTION: The antenna system 1 is provided with: the antenna body; a lightning rod 7; and support members (a supporter 8 and a lower metallic fixture 4 to be attached to a radome) for supporting the antenna body 100. The support members are formed of a conductive body. The antenna body 100 is mechanically and electrically connected to the lightning rod 7 and the support members. Through the configuration, both the lightning rod 7 and the antenna body 100 are supported by the support members. When the support members are electrically connected to the earth, not only lightning which strikes the lightning rod 7 but also lightning which strikes the antenna body 100 are escaped to the earth. The lightning rod 7 is integrated with the antenna body 100, and therefore, the antenna system having a lightning protection structure is downsized. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an antenna device, and more particularly to an antenna device including a lightning rod.

  Conventionally, an antenna device having a lightning protection structure for protecting the antenna body from lightning damage has been proposed. For example, Japanese Patent Laying-Open No. 2005-175637 (Patent Document 1) discloses a lightning protection structure in which an antenna body is arranged in a protection range of a lightning rod. In this antenna device, the antenna body is configured separately from the lightning rod.

  JP-A-10-98328 (Patent Document 2) discloses a cylindrical radiating element, a ring-shaped insulating spacer inserted into the radiating element, and a hole in the ring-shaped insulating spacer. An omnidirectional antenna is disclosed that includes a supported post and a lightning rod attached to the tip of the post.

JP 2005-175637 A Japanese Patent Laid-Open No. 10-98328

  According to the configuration disclosed in Patent Document 1, since the antenna body is separated from the lightning rod by a predetermined distance, the size of the antenna device is increased. Moreover, since the components for holding each of the antenna body and the lightning rod are required, the number of components increases.

  According to the configuration disclosed in Patent Document 2, the antenna is electrically insulated from the lightning rod by an insulator. For this reason, there is a possibility that the protection measures for the antenna when lightning falls on the antenna are not sufficient.

  An object of the present invention is to provide a miniaturized antenna device in which measures against lightning strikes of the antenna body are taken.

  In summary, the present invention is an antenna device, which includes an antenna body, a lightning rod, and a support member. The antenna body includes first and second connection portions that are conductive and are disposed along the first direction. The lightning rod is electrically and mechanically connected to the first connection portion. The support member has electrical conductivity and is electrically and mechanically connected to the second connection portion in order to support the antenna such that the first direction is the vertical direction.

  Preferably, the antenna body includes at least one antenna unit electrically and mechanically connected to the lightning rod and the support member. At least one antenna unit includes a first loop antenna element and a second loop antenna element. The first loop antenna element extends along the first direction and is arranged so as to face each other, and one end of the first long side conductor facing each other And a second short side conductor connecting the other end of the first long side conductor and the other end of the second long side conductor facing each other. And a short side conductor. The second loop antenna element extends along the first direction and is disposed so as to face each other, and one end of the third long side conductor facing each other And a third short-side conductor connecting one end of the fourth long-side conductor, a fourth short-side conductor connecting the other end of the third long-side conductor and the other end of the fourth long-side conductor facing each other. And a short side conductor. When the resonance wavelength of at least one antenna unit is defined as λ, the length in the first direction of each of the first to fourth long-side conductors is approximately λ / 2. The length of each of the first to fourth short-side conductors in the extending direction is approximately λ / 6. The first and second short-side conductors extend along a second direction orthogonal to the first direction. The third short-side conductor extends along a third direction orthogonal to the first and second directions, and is arranged so as to three-dimensionally intersect with the first short-side conductor. The fourth short-side conductor extends along the third direction and is arranged so as to three-dimensionally intersect with the second short-side conductor. The first connecting portion is disposed at substantially the center of either the first short side conductor or the third short side conductor. The second connecting portion is disposed at substantially the center of either the second short side conductor or the fourth short side conductor.

  Preferably, the at least one antenna unit further includes first to fourth feed lines. The first feeder line includes a first end connected to the first long-side conductor at a predetermined position in the first direction of the first long-side conductor, an opposite side of the first end, and a first length. And a second end located between the side conductor and the second long side conductor. The second feed line includes a first end connected to the second long-side conductor at a predetermined position in the first direction of the second long-side conductor, an opposite side of the first end, and a first length And a second end located between the side conductor and the second long side conductor. The third feed line includes a first end connected to the third long-side conductor at a predetermined position in the first direction of the third long-side conductor, a third end opposite to the first end, and a third length And a second end located between the side conductor and the fourth long side conductor. The fourth feed line includes a first end connected to the fourth long-side conductor at a predetermined position in the first direction of the fourth long-side conductor, a third end opposite to the first end, and a third length And a second end located between the side conductor and the fourth long side conductor. The width of each of the first to fourth feed lines is defined as the length in the direction orthogonal to the direction from the first end to the second end of the feed line, and the width of each of the first to fourth short-side conductors. Is defined as the length in the direction orthogonal to the extending direction of the short-side conductor, the width of the first and second feed lines is smaller than the width of any of the first and second short-side conductors, and the third The width of the fourth feeder line is smaller than the width of any of the third and fourth short-side conductors.

  ADVANTAGE OF THE INVENTION According to this invention, the countermeasure against the lightning strike of an antenna main body is taken, and the antenna apparatus reduced in size is realizable.

1 is an external view of an antenna device 1 according to an embodiment of the present invention. It is an internal structure figure of the antenna apparatus 1 shown in FIG. FIG. 3 is a perspective view of the antenna unit 101 shown in FIG. 2. It is the figure which looked at the antenna unit 101 shown in FIG. 3 from the A3 direction of FIG. It is the figure which looked at the antenna unit 101 shown in FIG. 3 from the A1 direction of FIG. It is the figure which looked at the antenna unit 101 shown in FIG. 3 from the A2 direction of FIG. It is a figure for comparing the width | variety of a feed line and the short side conductor of a loop antenna element. It is a figure which shows the structure of the combiner | synthesizer 51 shown in FIG. It is a figure which shows the gain characteristic of the antenna device which concerns on this Embodiment. It is a figure which shows the VSWR characteristic of the antenna device which concerns on this Embodiment. It is a figure which shows the horizontal surface directivity of the antenna device which concerns on this Embodiment. It is a figure which shows the vertical surface directivity of the antenna device which concerns on this Embodiment. It is a figure which shows the horizontal surface directivity pattern of the antenna main body 100 in case there is no lightning rod. It is a figure which shows the horizontal surface directivity pattern of the antenna main body 100 at the time of connecting a lightning rod to the antenna main body 100. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is an external view of an antenna device 1 according to an embodiment of the present invention. FIG. 2 is an internal structure diagram of the antenna device 1 shown in FIG. 1 and 2, an antenna device 1 includes a cylindrical radome 2 that houses an antenna main body 100, a tip cap 3 and a lower bracket attached to one and the other of two open ends of the radome 2, respectively. 4, mounting brackets 5 and 6 for mounting the antenna device 1 at a predetermined place, and a lightning rod 7.

  The antenna device 1 is attached to, for example, the tip of a utility pole, the tip of a steel tower, the rooftop of a high-rise building, and the like. For this purpose, the antenna device 1 includes mounting brackets 5 and 6. The tip cap 3 and the lower metal fitting 4 are formed of a conductor.

  The antenna device 1 further includes a support column 8 formed of a conductor and a fixing bracket 9 formed of the conductor. The support column 8 is attached to the fixing bracket 9. Further, the fixture 9 is attached to the lower bracket 4. Thereby, the support | pillar 8 is electrically and mechanically connected to the lower metal fitting 4. FIG. Although not shown in FIGS. 1 and 2, a lightning conductor for protecting the antenna device 1 from lightning damage is connected to the lower metal fitting 4. This lightning conductor is electrically connected to the ground (earth).

  In this specification, “electrically and mechanically connected” means a state in which two conductors are conductive and mechanically fixed. The connection method for this purpose is a method in which two conductors are mechanically brought into contact with each other, for example, by a metal screw, and the two conductors are fixed.

  The antenna body 100 is electrically and mechanically connected to the lightning rod 7 and the support column 8. The column 8, the fixing bracket 9, and the lower bracket 4 constitute a support member for supporting the antenna body 100 so that the lightning rod 7 connected to the antenna body 100 extends in the direction along the vertical direction.

  When the antenna body is provided at a certain distance from the lightning rod, it is necessary to individually support the antenna body and the lightning rod. In this case, since a support member for supporting each of the antenna main body and the lightning rod is required, the number of parts of the antenna device increases. Furthermore, since the antenna body and the lightning rod are separated from each other, the overall size of the antenna device is increased. Furthermore, since the antenna and the lightning rod are separate, there is a possibility that the protection in the event of lightning falling on the antenna will be insufficient.

  On the other hand, according to the present embodiment, since antenna body 100 is electrically and mechanically connected to lightning rod 7 and the support member, antenna body 100, lightning rod 7 and the support member are integrated. Therefore, it is not necessary to individually support the antenna body and the lightning rod, so that an increase in the number of parts of the antenna device can be suppressed. Furthermore, according to the present embodiment, since the antenna body 100 and the lightning rod 7 are integrated, it is possible to reduce the size of the antenna device having a lightning protection structure. Furthermore, according to the present embodiment, by electrically connecting the support member to the ground, not only the lightning that has fallen on the lightning rod 7, but also the lightning that has fallen on the antenna body 100 can be released to the ground. Therefore, according to the present embodiment, it is possible to realize a miniaturized antenna device in which protection measures against lightning strikes of the antenna body are taken.

  The antenna body 100 includes antenna units 101 and 102 and a connecting member 103. As will be described later in detail, each of the antenna units 101 and 102 is an omnidirectional antenna configured by two loop antenna elements. The connecting member 103 is formed of a conductor. The antenna units 101 and 102 are electrically and mechanically connected to the connecting member 103. In the present embodiment, antenna main body 100 is applied as a transmission antenna, but may be applied as a reception antenna.

  The antenna device 1 further includes coaxial cables CBL1 to CBL7, combiners 51, 52, and 53, mounting members 61, 62, and 63, and a connector CNC.

  The coaxial cables CBL1 and CBL2 are connected to the two loop antenna elements of the antenna unit 101, respectively. The synthesizer 51 synthesizes electrical signals transmitted through the coaxial cables CBL1 and CBL2. The coaxial cables CBL4 and CBL5 are connected to two antenna elements of the antenna unit 102, respectively. The synthesizer 52 synthesizes the electric signals transmitted through the coaxial cables CBL4 and CBL5, respectively.

  The coaxial cable CBL3 transmits the output of the combiner 51 to the combiner 53. The coaxial cable CBL6 transmits the output of the synthesizer 52 to the synthesizer 53. The electrical lengths of the coaxial cables CBL3 and CBL6 are adjusted to be substantially the same. The synthesizer 53 synthesizes the electrical signals transmitted through the coaxial cables CBL3 and CBL6, respectively. The coaxial cable CBL7 transmits the output of the combiner 53 to the connector CNC provided in the lower metal fitting 4.

  The synthesizers 51, 52, and 53 are attached to the attachment members 61, 62, and 63. The attachment member 61 is formed with a through-hole for allowing the connecting member 103 to pass therethrough. The attachment member 61 is fixed to the connection member 103 by passing the connection member 103 through the through hole. Similarly, a through hole is formed in each of the mounting members 62 and 63, and the mounting members 62 and 63 are fixed to the column 8 by passing the column 8 through the through hole.

  Next, the configuration of the antenna unit 101 will be described in detail. Since the configuration of antenna unit 102 is the same as the configuration described below, detailed description regarding the configuration of antenna unit 102 will not be repeated.

  FIG. 3 is a perspective view of the antenna unit 101 shown in FIG. Referring to FIG. 3, antenna unit 101 includes loop antenna elements 11 and 12, feed lines LN31, LN32, LN41 and LN42, and fixing brackets 21 and 22.

  The loop antenna element 11 has a long-side conductor LP31, a long-side conductor LP32, a short-side conductor SP31 and a short-side conductor SP32, and circulates in a substantially rectangular shape.

  The loop antenna element 12 includes a long-side conductor LP41, a long-side conductor LP42, a short-side conductor SP41 that intersects with the short-side conductor SP31, and a short-side conductor SP42 that intersects with the short-side conductor SP32. ing.

  Each conductor of loop antenna element 11, each conductor of loop antenna element 12, and feed lines LN31, LN32, LN41, and LN42 are, for example, conductor plates, that is, flat-plate conductors.

  The fixture 21 is made of a conductor and is electrically and mechanically connected to the short-side conductor SP41. Similarly, the fixing bracket 22 is formed of a conductor and is electrically and mechanically connected to the short-side conductor SP42. The fixture 21 is for electrically and mechanically connecting the lightning rod 7 to the antenna unit 101. The fixing bracket 22 is for electrically and mechanically connecting the connecting member 103 to the antenna unit 101.

  In the antenna unit 102, the fixing bracket 21 is used for electrically and mechanically connecting the connecting member 103 to the antenna unit 102, and the fixing bracket 22 is used for electrically connecting the support column 8 to the antenna unit 102. For mechanical connection.

  As can be seen from FIGS. 2 and 3, the antenna units (101, 102) are configured to be connectable. That is, in the present embodiment, the antenna body 100 is configured by multi-stage (specifically, two-stage) antenna units. However, the number of antenna units may be three or more, or one. When the number of stages of the antenna unit is 1, the lightning rod 7 is electrically and mechanically connected to the antenna unit fixing bracket 21 and the support column 8 is electrically and mechanically connected to the antenna unit fixing bracket 22. Is done.

  The axis Z is the central axis of the antenna unit 101. The antenna unit 101 is installed by support members (the support column 8, the fixing bracket 9, and the lower bracket 4) such that the axis Z extends along the vertical direction. In this state, the short-side conductors SP31 and SP41 are located above the antenna unit 101, and the short-side conductors SP32 and SP42 are located below the antenna unit 101. As a result, the plane of polarization of each of the antenna units 101 and 102 becomes a horizontal plane.

  The A1 direction and the A2 direction shown in FIG. 3 are directions along the axis Z and opposite to each other. Specifically, the A1 direction is a direction from the top to the bottom of the antenna unit 101, and the A2 direction is a direction from the bottom to the top of the antenna unit 101. Further, the A3 direction is a direction orthogonal to the axis Z. The A4 direction in FIG. 3 is a direction orthogonal to the axis Z and orthogonal to the direction A3.

  4 is a view of the antenna unit 101 shown in FIG. 3 as viewed from the direction A3 in FIG. FIG. 5 is a diagram of the antenna unit 101 shown in FIG. 3 as viewed from the direction A1 in FIG. 6 is a view of the antenna unit 101 shown in FIG. 3 as viewed from the direction A2 in FIG.

  3 to 6, the short-side conductor SP31 and the short-side conductor SP41 intersect at a substantially right angle, and the short-side conductor SP32 and the short-side conductor SP42 intersect at a substantially right angle.

  Hereinafter, the extending direction of the long-side conductor LP31, the long-side conductor LP32, the long-side conductor LP41, and the long-side conductor LP42, that is, the direction parallel to the Z-axis is also referred to as “vertical direction of the antenna unit 101”. A direction perpendicular to the Z axis (for example, the A3 direction and its reverse direction, and the A4 direction and its reverse direction) is also referred to as “the horizontal direction of the antenna unit 101”. In addition, the A1 direction in the installed state of the antenna unit 101 shown in FIG. 3 is also referred to as “vertical downward direction”, and the opposite direction, that is, the A2 direction is also referred to as “vertical upward direction”.

  Feed line LN31 has a first end connected to long-side conductor LP31, and a second end located on the opposite side of the first end and between long-side conductor LP31 and long-side conductor LP32. The first end of the feeder line LN31 is connected to the long-side conductor LP31 at a predetermined position away from the center in the extending direction of the long-side conductor LP31 (vertical direction of the antenna unit 101) in the extending direction, for example, vertically downward. .

  The feed line LN32 has a first end connected to the long-side conductor LP32 and a second end located on the opposite side of the first end and between the long-side conductor LP31 and the long-side conductor LP32. The first end of the feeder line LN32 is connected to the long-side conductor LP32 at a predetermined position away from the center in the extending direction of the long-side conductor LP32 (vertical direction of the antenna unit 101) in the extending direction, for example, vertically downward. .

  Feed line LN41 has a first end connected to long-side conductor LP41 and a second end located on the opposite side of the first end and between long-side conductor LP41 and long-side conductor LP42. The first end of the feeder line LN41 is connected to the long-side conductor LP41 at a predetermined position away from the center in the extending direction of the long-side conductor LP41 (vertical direction of the antenna unit 101) in the extending direction, for example, vertically downward. .

  Feed line LN42 has a first end connected to long-side conductor LP42, and a second end located on the opposite side of the first end and between long-side conductor LP41 and long-side conductor LP42. The first end of the feeder line LN42 is connected to the long-side conductor LP42 at a position away from the center in the extending direction of the long-side conductor LP42 (vertical direction of the antenna unit 101) in the extending direction, for example, vertically downward.

  The long-side conductor LP31 and the long-side conductor LP32 extend along the axis Z and are arranged to face each other so as to be substantially parallel. The long-side conductor LP41 and the long-side conductor LP42 extend along the axis Z and are arranged to face each other so as to be substantially parallel. The lengths in the Z-axis direction of the long side conductors LP31, LP32, LP41, LP42 are substantially the same.

  The short-side conductor SP31 connects one end of the long-side conductor LP31 and one end of the long-side conductor LP32 facing the one end. The short-side conductor SP32 connects the other end of the long-side conductor LP31 and the other end of the long-side conductor LP32 facing the other end. The short-side conductor SP41 connects one end of the long-side conductor LP41 and one end of the long-side conductor LP42 facing the one end. The short-side conductor SP42 connects the other end of the long-side conductor LP41 and the other end of the long-side conductor LP42 facing the other end.

  The short-side conductors SP31 and SP32 are arranged so as to extend in the A4 direction. On the other hand, the short-side conductors SP41 and SP42 are arranged to extend in the A3 direction. The length in the A4 direction of each of the short side conductors SP31 and SP32 and the length in the A3 direction of each of the short side conductors SP41 and SP42 are substantially the same.

  The short-side conductor SP31 and the short-side conductor SP32 are bent in a direction that reduces the volume of the space surrounded by the loop antenna element 11. The short-side conductor SP41 and the short-side conductor SP42 are bent in a direction that reduces the volume of the space surrounded by the loop antenna element 12. In other words, each of the short-side conductor SP31 and the short-side conductor SP32 has a recessed portion that is recessed in the direction of the space surrounded by the loop antenna element 11. Each of the short-side conductor SP41 and the short-side conductor SP42 has a recessed portion that is recessed in the direction of the space surrounded by the loop antenna element 12.

  The short-side conductors SP31 and SP41 are fixed by screws 41 at positions corresponding to the cross points of the short-side conductors SP31 and SP41. The fixture 21 is installed at the center of the short-side conductor SP41, that is, at a position corresponding to the cross point of the short-side conductors SP31 and SP41.

  As shown in FIG. 6, the short-side conductors SP32 and SP42 are fixed by screws 42 at positions corresponding to both cross points, that is, at substantially the center of the short-side conductors SP32 and SP42. The fixing bracket 22 is installed at the center of the short-side conductor SP42, that is, at a position corresponding to the cross point of the short-side conductors SP32 and SP42.

  The feed lines LN31 and LN32 are connected to the long-side conductor LP31 and the long-side conductor LP32, respectively, at the same height from the lower end of the short-side conductor SP32, for example. The feed lines LN41 and LN42 are connected to the long-side conductor LP41 and the long-side conductor LP42, for example, at substantially the same height from the lower end of the short-side conductor SP32 and at a position lower than the feed-lines LN31 and LN32.

  The feed lines LN31, LN32, LN41, and LN42 extend in the horizontal direction of the antenna unit 101, that is, in a direction substantially perpendicular to the long side conductors LP31, LP32, LP41, and LP42. The feed line LN31 extends in the direction from the long side conductor LP31 to the long side conductor LP32, the feed line LN32 extends in the direction from the long side conductor LP32 to the long side conductor LP31, and the feed line LN41 extends from the long side conductor LP41. The feed line LN42 extends in the direction from the long-side conductor LP42 to the long-side conductor LP41.

  Further, the second ends of the feed lines LN31, LN32, LN41, and LN42 are near the center between the long-side conductor LP31 and the long-side conductor LP32 and the long-side conductor LP41 so that the second ends of the other feed-lines are not in contact with each other. And near the center between the long side conductors LP42.

  FIG. 7 is a diagram for comparing the widths of the feed line and the short-side conductor of the loop antenna element. The “width of the short side conductor” means a length in a direction orthogonal to the extending direction of the short side conductor. The “feed line width” is the length in a direction perpendicular to the extending direction of the feed line, that is, perpendicular to the direction from the first end (end connected to the long-side conductor) to the second end of the feed line. It means the length of the direction to do.

  Referring to FIG. 7, the short-side conductors SP31, SP32, SP41, and SP42 all have a width W1, and the feed lines LN31, LN32, LN41, and LN42 all have a width W2. The width (W1) of the short-side conductor SP31 is larger than the width (W2) of the feed lines LN31 and LN32 (FIG. 7 (a)). The width (W1) of the short-side conductor SP41 is larger than the width (W2) of the feed lines LN41 and LN42 (FIG. 7A).

  Thus, by making the width of the short side conductor larger than the width of the feed line, the resistance of the short side conductor becomes smaller than the resistance of the feed line. For this reason, when a lightning strikes the antenna body, there is a high possibility that the lightning will be transmitted to the support column 8 via a path with low electrical resistance, that is, the short-side conductor, the long-side conductor, and the fixing bracket 22. In other words, it is possible to reduce the possibility that lightning will travel along the feeder line. Therefore, it is possible to reduce damage caused by lightning such as a feeder line and a combiner.

  Returning to FIG. 3, the loop antenna elements 11 and 12 are loop antennas called “hentena”. That is, the long-side conductor LP31, the long-side conductor LP32, the long-side conductor LP41, and the long-side conductor LP42 are approximately the resonance wavelength λ of the antenna unit 101 (that is, the wavelength that the antenna unit 101 should transmit or receive) in the Z-axis direction. It has a length of 1/2. The short-side conductor SP31 and the short-side conductor SP32 have a length of about 1/6 of the wavelength λ in the A4 direction. The short-side conductor SP41 and the short-side conductor SP42 have a length of about 1/6 of the wavelength λ in the A3 direction.

  The coaxial cable CBL1 has an internal conductor CI1 connected to the feed point FD1 at the second end of the feed line LN31, and an external conductor CO1 connected to the feed point FD2 at the second end of the feed line LN32.

  The coaxial cable CBL2 has an internal conductor CI2 connected to the feed point FD3 at the second end of the feed line LN41, and an external conductor CO2 connected to the feed point FD4 at the second end of the feed line LN42. The electrical lengths of the coaxial cables CBL1 and CBL2 are adjusted to be different from each other by λ / 4.

  Although not shown, for example, a balun is connected to the feeding points FD1 and FD2 for impedance matching. Furthermore, for example, a balun is connected to the feeding points FD3 and FD4 for impedance matching. These baluns are, for example, U baluns. However, in order to avoid complication of the figure, the balun is not shown in FIG.

  The combiners 51 to 53 shown in FIG. 2 are formed of, for example, a printed board. Since the configurations of the combiners 51 to 53 are the same as each other, the configuration of the combiner 51 will be typically described below.

  FIG. 8 is a schematic diagram showing the configuration of the combiner 51 shown in FIG. Referring to FIG. 8, lines 71 to 74 connected to each other by a metal thin film (for example, copper foil) are formed on one main surface of the printed board. The other main surface (hereinafter referred to as “back surface”) of the printed circuit board is almost entirely an earth pattern.

  The synthesizer 51 is a Wilkinson synthesizer to avoid interference between the two inputs. More specifically, the line 71 is connected to the inner conductor CI1 of the coaxial cable CBL1. The line 71 is provided with a stub ST1 for improving the VSWR (Voltage Standing Wave Ratio) characteristic. Furthermore, one end of a coil CL1 is connected to the line 71. The other end of the coil CL1 is connected to the ground pattern on the back surface of the printed circuit board through the through hole 81. The distance between one end of the coil CL1 and the other end of the coil CL1 is approximately λ / 4.

  An internal conductor CI2 of the coaxial cable CBL2 is connected to the line 72. The line 72 is provided with a stub ST2 for improving the VSWR characteristic. Furthermore, one end of a coil CL2 is connected to the line 72. The other end of the coil CL2 is connected to the ground pattern on the back surface of the printed circuit board through the through hole 82. The distance between one end of the coil CL2 and the other end of the coil CL2 is approximately λ / 4.

  Resistance element R is connected to lines 71 and 72. Lines 71 and 72 are connected to line 74. The line 74 is provided with stubs ST3 and ST4 in order to improve the VSWR characteristics.

  The line 74 is connected to the line 73. An internal conductor CI3 of the coaxial cable CBL3 is connected to the line 73. The line 73 is provided with a stub ST5 in order to improve the VSWR characteristic. Furthermore, one end of a coil CL3 is connected to the line 73. The other end of the coil CL3 is connected to the ground pattern on the back surface of the printed circuit board through the through hole 83. The distance between one end of the coil CL3 and the other end of the coil CL3 is approximately λ / 4.

  By setting the distance between one end and the other end of each of the coils CL <b> 1 to CL <b> 3 to a length of approximately λ / 4, reflected waves can be reduced and matching can be improved.

  Next, the performance of the antenna device configured as described above will be specifically described. The performance of the antenna device described below is obtained by configuring the antenna device 1 so that radio waves in the frequency band (470 to 770 MHz) of UHF television broadcasting in Japan can be transmitted and received. Specifically, the antenna device 1 is a suitable antenna device for transmitting and receiving radio waves in the UHF band, particularly the L band (470 MHz to 584 MHz) of the terrestrial digital broadcasting frequency band (470 to 710 MHz) in Japan. The length, width, and distance parameters of each part in the antenna device 1 (antenna units 101 and 102) were designed.

  In the following, gain, VSWR, and directivity pattern are shown as the performance of the antenna device 1. The higher the numerical value indicating the gain, the better the antenna performance. Further, the lower the numerical value indicating VSWR, the better the characteristics of the antenna. Furthermore, since the antenna device according to the present embodiment is a horizontally polarized omnidirectional antenna, the directivity pattern is preferably as close to a circle as possible.

  FIG. 9 is a diagram illustrating gain characteristics of the antenna device according to the present embodiment. Referring to FIG. 9, in the frequency band of 470 to 584 MHz described above, the gain of the antenna device is about 0 dB to about +2.0 dB, and good characteristics are realized.

  FIG. 10 is a diagram illustrating the VSWR characteristics of the antenna device according to the present embodiment. Referring to FIG. 10, in the frequency band of 470 to 584 MHz described above, the VSWR of the antenna device is in the range of 1.0 to 1.5. Generally, from a practical point of view, VSWR is preferably 1.5 or less. Therefore, according to the present embodiment, good VSWR characteristics are realized in the frequency band of 470 to 584 MHz.

  FIG. 11 is a diagram illustrating horizontal plane directivity of the antenna device according to the present embodiment. FIG. 11 typically shows horizontal plane directivity patterns of 470 MHz, 530 MHz, 570 MHz, and 590 MHz in order to cover the frequency band at 470 to 584 MHz. Good omnidirectionality, that is, substantially elliptical or substantially circular omnidirectionality is realized at each frequency. From this, it can be seen that stable horizontal omnidirectionality is realized in the frequency band of 470 MHz to 584 MHz.

  FIG. 12 is a diagram illustrating the directivity of the vertical plane of the antenna device according to the present embodiment. FIG. 12 typically shows vertical plane directivity patterns of 530 MHz and 570 MHz in the frequency band of 470 to 584 MHz.

  Here, by connecting the lightning rod 7 and the support column 8 to the antenna, there is a possibility that the characteristics of the antenna become worse than originally specified. However, according to the present embodiment, the deterioration of characteristics can be suppressed by connecting the lightning rod to one of the two cross points of the two loop antenna elements and connecting the column to the other. This point will be described by taking the horizontal plane directivity as an example.

  FIG. 13 is a diagram illustrating a horizontal plane directivity pattern of the antenna body 100 when there is no lightning rod. FIG. 14 is a diagram illustrating a horizontal plane directivity pattern of the antenna main body 100 when a lightning rod is connected to the antenna main body 100.

  Referring to FIGS. 13 and 14, horizontal plane directivity patterns of 530 MHz, 540 MHz, 550 MHz, 560 MHz, 570 MHz, and 580 MHz are typically shown in the above-described frequency band of 470 to 584 MHz. As can be seen by comparing FIG. 13 and FIG. 14, there is almost no change in the horizontal plane directivity pattern due to the presence or absence of the lightning rod.

  As shown in FIG. 1, the antenna body 100 is housed in the radome 2. The radome 2 is cylindrical. From the viewpoint of miniaturization of the antenna device 1, it is preferable that the diameter of the radome 2, that is, the length of the antenna body in the horizontal direction is as short as possible.

  As an antenna having a structure capable of reducing the diameter of the radome 2, for example, a slot antenna in which a slot is formed in a part of a cylinder, a two-turn open loop antenna, and the like are conceivable. However, in the case of these antennas, the horizontal plane directivity is less likely to be favorable. On the other hand, as an antenna for obtaining good omnidirectionality (horizontal plane omnidirectionality), for example, an alhode antenna, a clover leaf antenna, a cross dipole antenna, and the like are known. However, in the case of these antennas, there arises a problem that the length in the horizontal direction becomes large.

  In the antenna device according to the embodiment of the present invention, since each of the two loop antenna elements is a henna, the long-side conductor LP31, the long-side conductor LP32, the long-side conductor LP41, and the long-side conductor LP42 are included in the antenna unit 101. The short-side conductor SP31, the short-side conductor SP32, the short-side conductor SP41, and the short-side conductor SP42 have a length that is approximately ½ of the resonance wavelength, and have a length that is approximately 1/6 of the resonance wavelength of the antenna unit 101. Have. That is, the short-side conductor is shorter than the long-side conductor.

  The antenna unit is supported so that the extending direction of the short-side conductor is substantially horizontal (so that the extending direction of the long-side conductor is substantially vertical). Thus, the length of the horizontal direction can be reduced by arranging the loop antenna elements 11 and 12 as the henna and arranging the henna so that the extending direction of the short side of the henna is substantially horizontal. . Further, the two hennas are arranged so that the respective short-side conductors are orthogonal to each other. Thereby, the antenna unit has horizontal polarization omnidirectionality as a characteristic.

  In the present embodiment, the fixtures 21 and 22 correspond to the first and second connection portions arranged along the Z-axis direction (first direction), respectively. However, the lightning rod 7 is directly connected to one of the two cross points of the loop antenna elements 11 and 12 without providing the fixing brackets 21 and 22, and the column 8 (or the connecting member 103) is connected to the other cross point. May be. The two cross points in this case correspond to the first and second connection portions, respectively.

  In the present embodiment, the short-side conductor included in the loop antenna element is bent. However, it is not essential to bend the short-side conductor, and a straight conductive plate may be used as the short-side conductor.

  In the present invention, the antenna body is not limited to the one having horizontal polarization non-directionality, and any antenna body that can be electrically and mechanically connected to the lightning rod and the support member may be used. Even with such an antenna, the overall size of the antenna can be reduced as compared with a configuration in which the lightning rod and the antenna are separately installed.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Antenna device, 2 radome, 3 tip cap, 4 lower bracket, 5,6 mounting bracket, 7 lightning rod, 8 strut, 9 fixing bracket, 11, 12 loop antenna element, 21,22 fixing bracket, 41, 42 screw, 51 ~ 53 combiner, 61, 62, 63 mounting member, 71-74 line, 81-83 through hole, 100 antenna body, 101, 102 antenna unit, 103 connecting member, CBL1-CBL7 coaxial cable, CI1-CI3 inner conductor, CL1-CL3 coil, CNC connector, CO1, CO2 outer conductor, FD1-FD4 feed point, LN31, LN32, LN41, LN42 feed line, LP31, LP32, LP41, LP42 long side conductor, R resistance element, SP31, SP32, SP41 , SP42 Short side conductor, ST1 to ST Stub.

Claims (3)

An antenna body including first and second connecting portions having electrical conductivity and disposed along a first direction;
A lightning rod electrically and mechanically connected to the first connection;
An antenna device comprising: a conductive member and a support member electrically and mechanically connected to the second connection portion to support the antenna so that the first direction is a vertical direction. . The antenna body is
Including at least one antenna unit electrically and mechanically connected to the lightning rod and the support member;
The at least one antenna unit comprises:
First and second long-side conductors extending along the first direction and arranged to face each other, one end of the first long-side conductors facing each other, and the second length A first short-side conductor connecting one end of the side conductor, and a second short-side connecting the other end of the first long-side conductor and the other end of the second long-side conductor facing each other A first loop antenna element having a conductor;
Third and fourth long side conductors extending along the first direction and arranged to face each other, one end of the third long side conductors facing each other, and the fourth length A third short-side conductor connecting one end of the side conductor, and a fourth short side connecting the other end of the third long-side conductor and the other end of the fourth long-side conductor facing each other A second loop antenna element having a conductor;
When the resonance wavelength of the at least one antenna unit is defined as λ, the length in the first direction of each of the first to fourth long-side conductors is approximately λ / 2, and the first to fourth The length of each of the four short-side conductors in the extending direction is approximately λ / 6.
The first and second short-side conductors extend along a second direction orthogonal to the first direction;
The third short-side conductor extends along a third direction orthogonal to the first and second directions, and is arranged so as to three-dimensionally intersect the first short-side conductor,
The fourth short-side conductor extends along the third direction and is arranged so as to three-dimensionally intersect with the second short-side conductor,
The first connection portion is disposed at substantially the center of either the first short-side conductor or the third short-side conductor,
2. The antenna device according to claim 1, wherein the second connection portion is disposed at substantially the center of one of the second short-side conductor and the fourth short-side conductor. The at least one antenna unit comprises:
A first end connected to the first long-side conductor at a predetermined position in the first direction of the first long-side conductor; an opposite side of the first end; and the first long-side conductor; A first feed line having a second end located between the second long-side conductors;
A first end connected to the second long-side conductor at a predetermined position in the first direction of the second long-side conductor; an opposite side of the first end; and the first long-side conductor; A second feed line having a second end located between the second long-side conductors;
A first end connected to the third long-side conductor at a predetermined position in the first direction of the third long-side conductor; an opposite side of the first end; and the third long-side conductor; A third feed line having a second end located between the fourth long-side conductors;
A first end connected to the fourth long-side conductor at a predetermined position in the first direction of the fourth long-side conductor; an opposite side of the first end; and the third long-side conductor; A fourth feed line having a second end located between the fourth long-side conductors,
The width of each of the first to fourth feed lines is defined as the length in a direction orthogonal to the direction from the first end to the second end of the feed line, and each of the first to fourth short-side conductors is defined. Is defined as the length in the direction perpendicular to the extending direction of the short-side conductor,
The width of the first and second feeder lines is smaller than the width of either of the first and second short-side conductors,
3. The antenna device according to claim 2, wherein a width of each of the third and fourth feed lines is smaller than a width of each of the third and fourth short-side conductors.

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