JP2010057007A - Antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small and high-performance antenna, wherein a waveguide device and a reflector are formed of a conductor plate. <P>SOLUTION: The antenna 1 includes a radiator 2, a waveguide device 3, and a reflector 4. The radiator 2 includes: a radiation element 11, which contains a radiating portion 14 and a power feeding line 15 connected to the radiating portion 14; and sleeve conductors 12, 13. The radiating portion 14 and the power feeding line 15 are integrally formed of a plane conductor. When a direction (direction of Y) which intersects perpendicularly the extending direction (direction of X) of the power feeding line 14 is defined as a width direction, the width-directional length of the radiation portion 14 is larger than the width-directional length of the power feeding line 15. The sleeve conductor 12 is formed of a first conductive plate with a width-directional length larger than the width-directional length of the power feeding line 15. The sleeve conductor 13 is formed of a second conductive plate with a width-directional length larger than the width-directional length of the power feeding line 15 and is so provided on the side opposite to the sleeve conductor 12 with respect to the plane conductor to sandwich the power feeding line 15 together with the sleeve conductor 12. In addition, the reflector 4 is formed of a conductive plate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an antenna, and more particularly to an antenna including a radiator, a director, and a reflector.

Yagi antennas (also called Yagi / Uda antennas) are widely used for receiving television broadcasts. The Yagi antenna is defined as a linear end-fire antenna composed of one radiator, one or more reflectors and one or more directors. Therefore, the minimum configuration of the Yagi antenna is a configuration including one radiator, one reflector, and one director. Since the number of elements of the Yagi antenna is the total number of radiators, reflectors, and directors, the number of elements of the Yagi antenna having the minimum configuration is 3 elements (see Non-Patent Document 1).
The Institute of Electronics, Information and Communication Engineers, “Antenna Engineering Handbook”, 1st Edition, Ohmsha, October 30, 1980, P.116-119

  A half-wave dipole antenna or a folded dipole antenna is usually used as a radiator of a three-element Yagi antenna. A conventional three-element Yagi antenna has a total length of λ / 2. (Λ represents the resonance wavelength of the antenna). This length is determined from the viewpoint of improving performance such as gain. Therefore, according to the configuration of the conventional three-element Yagi antenna, it is difficult to obtain good performance while making the total length of the antenna shorter than λ / 2.

  The half-wave dipole antenna or the folded dipole antenna described above is a balanced feed type radiator. On the other hand, a coaxial cable generally used as a feed line is an unbalanced feed type feed line. Therefore, when a coaxial cable is connected to a balanced feed type radiator, a matching unit is required to convert between balanced feed and unbalanced feed. However, inserting a matching device between the radiator and the coaxial cable causes an insertion loss of the matching device.

  The present invention is to solve the above-described problems, and an object thereof is to provide a small and high-performance antenna.

  In summary, the present invention is an antenna, and includes a radiating element including a radiating portion and a feed line connected to the radiating portion. The radiating portion and the feed line are integrally formed by a planar conductor. If the direction orthogonal to the extending direction of the feed line is defined as the width direction, the length of the radiating portion in the width direction is larger than the length of the feed line in the width direction. The antenna further includes a first sleeve conductor, a second sleeve conductor, a director, and a reflector. The first sleeve conductor is formed by a first conductor plate whose length in the width direction is larger than the length in the width direction of the feed line, and faces the region where the feed line is formed on the main surface of the planar conductor. The second sleeve conductor is formed by a second conductor plate having a length in the width direction that is greater than the length in the width direction of the feed line, and the second sleeve conductor has a second length with respect to the planar conductor so as to sandwich the feed line with the first sleeve conductor. 1 is provided on the opposite side of the sleeve conductor. The director is provided on the same side as the first sleeve conductor with respect to the planar conductor and outside the first sleeve conductor with respect to the planar conductor. The reflector is provided on the same side as the second sleeve conductor with respect to the planar conductor and outside the second sleeve conductor with respect to the planar conductor.

  Preferably, the distance between the planar conductor and the director is shorter than the distance between the planar conductor and the reflector.

  Preferably, one of the first and second sleeve conductors includes first and second plate-like portions and a connection portion. Each of the first and second plate-like portions is arranged in parallel to the main surface of the planar conductor, and the first end located on the side closer to the radiating portion in the extending direction of the feed line and the feed line And a second end located on the side far from the radiating portion in the extending direction. The connecting portion connects the first ends of the first and second plate-like portions. The other of the first and second sleeve conductors is a conductor whose main surface is arranged parallel to the planar conductor and is formed in a flat plate shape.

  Preferably, each of the first and second sleeve conductors connects the first and second plate-like portions disposed in parallel to the main surface of the planar conductor and the first and second plate-like portions. Including a connecting portion. Each of the first and second plate-like portions is located on the side closer to the radiating portion in the extending direction of the feed line, and on the side far from the radiating portion in the extending direction of the feed line. And a second end. The connecting portion connects the first ends of the first and second plate-like portions.

  Preferably, each of the first and second sleeve conductors is a conductor having a main surface arranged parallel to the planar conductor and formed in a flat plate shape.

  Preferably, at least a part of the waveguide faces the radiating portion, and the length in the width direction is smaller than the length in the width direction of the radiating portion.

  Preferably, the director is formed of a conductor plate and has a polygonal surface.

  According to the present invention, a small and high-performance antenna can be realized.

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

  FIG. 1 is a perspective view of an antenna 1 according to an embodiment of the present invention. FIG. 2 is a side view of the antenna 1 shown in FIG. FIG. 3 is a plan view showing elements constituting the antenna 1 shown in FIG. The antenna according to this embodiment will be described in detail below with reference to FIGS.

  As shown in FIGS. 1 and 2, the antenna 1 includes a radiator 2, a director 3, and a reflector 4. The antenna 1 can be used as a receiving antenna that receives the radio wave 5 that is directed toward itself, and can also be used as a transmitting antenna that radiates the radio wave 6.

  The radiator 2 includes a radiating element 11 and sleeve conductors 12 and 13. The radiating element 11 includes a radiating unit 14 that radiates (or receives) a radio wave, and a feed line 15. The feed line 15 is connected to the radiation unit 14. The radiating portion 14 and the feed line 15 are integrally formed by a planar conductor. A “planar conductor” is specifically a conductive thin film on a conductor plate or a dielectric substrate, and has a length (thickness) in a direction perpendicular to the two-dimensional direction compared to the length in the two-dimensional direction. It is a sufficiently small conductor. In the present embodiment, the radiating element 11 (that is, the radiating portion 14 and the feed line 15) is formed of a conductor plate.

  Further, in the present embodiment, the sleeve conductors 12 and 13 are also formed of a conductor plate. Specifically, the sleeve conductor 12 is formed by folding one conductor plate (bending one conductor plate twice in a right angle direction). The sleeve conductor 12 is disposed on the main surface of the planar conductor forming the radiating element 11 so as to face the region where the feed line 15 is formed. The sleeve conductor 13 is provided on the side opposite to the sleeve conductor 12 with respect to the radiating element 11 (planar conductor) so as to sandwich the feeder line 15 together with the sleeve conductor 12. That is, the sleeve conductor 13 is provided on the side opposite to the sleeve conductor 12 with respect to the feed line 15 and faces the feed line 15. The sleeve conductors 12 and 13 may be formed of a conductive thin film on a dielectric substrate.

In addition, the X direction shown in FIG. The Y direction indicates a direction parallel to the planar conductor (radiating element 11) and orthogonal to the X direction. The Y direction corresponds to the width direction of the feeder line 15. Accordingly, in the following description, the Y direction may be referred to as the “width direction”.
The Z direction is a direction orthogonal to both the X direction and the Y direction, and corresponds to the arrangement direction of the radiator 2, the waveguide 3, and the reflector 4.

  As shown in FIG. 2, the radiating element 11 is connected to the coaxial line 7. Specifically, the feed line 15 is connected to the inner conductor 8 of the coaxial line 7, and the sleeve conductors 12 and 13 are both connected to the outer conductor 9 of the coaxial line 7.

  The director 3 is formed by a conductor plate. When the antenna 1 is used as a receiving antenna, the director 3 realizes a function of guiding the radio wave 5 arriving at the antenna 1 to the radiating element 11. On the other hand, when the antenna 1 is used as a transmission antenna, the director 3 realizes a function of guiding the radio wave 6 radiated from the radiating element 11 to the front of the antenna 1.

  The reflector 4 is formed by a conductor plate. When the antenna 1 is used as a receiving antenna, the reflector 4 realizes a function of reflecting a radio wave arriving at the antenna 1 and guiding it to the radiating element 11. On the other hand, when the antenna 1 is used as a transmission antenna, the reflector 4 realizes a function of reflecting the radio wave radiated from the radiating element 11 and guiding it in the direction of the waveguide 3.

  FIG. 2 shows a state where the antenna 1 is viewed from the Y direction shown in FIG. As shown in FIG. 2, the distance between the director 3 and the reflector 4 is d, the distance between the director 3 and the radiating element 11 is d1, and the distance between the radiating element 11 and the reflector 4 is set. Is d2. In the present embodiment, the distance d is set to about 1 / 4λ. Further, the distance d1 is set smaller than the distance d2. Note that λ represents the resonance wavelength of the antenna 1.

  The configuration of the sleeve conductor 12 will be described in detail. The sleeve conductor 12 includes plate-like portions 16 and 17 arranged in parallel to the main surface of the planar conductor (radiating element 11), and a connecting portion for connecting the plate-like portions 16 and 17. 18 and so on. The shortest distance between the plate-like portion 16 and the feed line 15 is d3.

  The plate-like portion 16 includes an end portion 16a located on the side closer to the radiating portion 14 in the X direction and an end portion 16b located on the side farther from the radiating portion 14 in the X direction. The plate-like portion 17 includes an end portion 17a located on the side closer to the radiating portion 14 in the X direction and an end portion 17b located on the side farther from the radiating portion 14 in the X direction.

  The connection part 18 connects the edge part near the radiation | emission part 14 which each of plate-shaped part 16 and 17 has, ie, edge part 16a, 17a. On the other hand, the end portions of the plate-like portions 16 and 17 on the side far from the radiating portion 14, that is, the end portions 16 b and 17 b are not connected to each other. Note that the end 16 b is connected to the outer conductor 9 of the coaxial line 7.

  The sleeve conductor 13 is formed in a flat plate shape, and includes an end portion 13a positioned on the side closer to the radiating portion 14 in the X direction and an end portion 13b positioned on the side farther from the radiating portion 14 in the X direction. The end portion 13 a is electrically opened, and the end portion 13 b is connected to the outer conductor 9 of the coaxial line 7. The shortest distance between the sleeve conductor 13 and the feed line 15 is d4. The shortest distance d5 between the sleeve conductor 13 and the reflector 4 is a predetermined length set so that the performance of the antenna 1 is good.

  The X direction and Y direction shown in FIG. 3 correspond to the X direction and Y direction shown in FIG. 1, respectively. With reference to FIG. 1 and FIG. 3, the director 3 includes a central portion 31 and projecting portions 32 and 33 provided so as to project from the central portion 31. That is, the main surface of the conductor plate which is the waveguide 3 has a cross shape.

  If the length in the Y direction of the central portion 31 is Wa and the length in the Y direction of the protrusions 32 and 33 is Wb, Wb is smaller than Wa. That is, the length (Wb) of the protrusions 32 and 33 in the width direction is smaller than the length (Wa) of the center portion 31 in the width direction.

  The length of the sleeve conductor 12 in the X direction is L1, and the length of the sleeve conductor 12 in the Y direction is Wc. The length L1 is set to a predetermined length (for example, about λ / 4). Wc is determined to be larger than the length of the feed line 15 in the Y direction (width W2). Furthermore, if the length of the radiating portion 14 in the Y direction (width direction) is W1, W1 is larger than the length of the feed line 15 in the Y direction (W2). The width W2 and the distances d3 and d4 shown in FIG. 2 are determined so that the impedance of the feed line 15 substantially matches the impedance of the coaxial line 7. The impedance value is, for example, 75Ω or 50Ω.

  Further, the length L2 in the X direction of the radiating portion 14 is set to a predetermined length (for example, about λ / 4). Further, the length L3 of the feed line 15 in the X direction is not particularly limited, but is set to a length suitable for connection between the coaxial line 7 and the feed line 15, for example.

  The length of the sleeve conductor 13 in the X direction is L4, and the length of the sleeve conductor 13 in the Y direction is Wd. Wd is determined to be larger than the width W2 of the feed line 15. In the present embodiment, Wd is determined to be equal to the length (Wc) of the sleeve conductor 12 in the Y direction, and L4 is determined to be the same length as L1 (for example, approximately λ / 4).

  As shown in FIGS. 1 to 3, the radiator 2 includes a radiating element 11 and sleeve conductors 12 and 13 each of which is constituted by a conductor plate. The radiating element 11 and the sleeve conductors 12 and 13 are arranged along the thickness direction of the conductor plate, that is, the Z direction in FIG. Thus, according to the present embodiment, a miniaturized and high performance antenna can be realized. This point will be described in detail below.

  First, the configuration of radiator 2 shown in FIG. 1 will be described in more detail. The radiator 2 has a configuration equivalent to a so-called sleeve antenna.

  FIG. 4 is a diagram showing one form of a sleeve antenna which is a comparative example of the antenna 1 according to the present embodiment. Referring to FIG. 4, the sleeve antenna 2 </ b> A includes a coaxial line 40 including an inner conductor 41 and an outer conductor 42, and a sleeve conductor 43. The inner conductor 41 is a straight conductor. The outer conductor 42 is formed in a cylindrical shape extending in the same direction as the inner conductor 41, and is arranged so that its central axis coincides with the central axis of the inner conductor 41. In order to electrically insulate the inner conductor 41 and the outer conductor 42, for example, a gap may be provided between them, or an insulator may be filled therein.

  The inner conductor 41 has two end portions 44 and 45. The outer conductor 42 includes an inner surface 46 that faces a part of the inner conductor 41, an end 47 that is positioned between the ends 44, 45 of the inner conductor 41, and an opposite side to the end 47, that is, the inner conductor. 41 and an end portion 48 located on the end portion 45 side. Assuming that the resonance wavelength of the sleeve antenna 2A is λ, a portion of the inner conductor 41 having a length of about λ / 4 from the end 44 is exposed without being covered with the outer conductor 42, and the remaining portion is exposed to the outer conductor 42. It faces the inner surface 46. That is, the end portion 47 of the outer conductor 42 is located at a position away from the end portion 44 of the inner conductor 41 by about λ / 4.

  The sleeve conductor 43 is disposed outside the coaxial line 40 and is electrically connected to the outer conductor 42 at the end 47 of the outer conductor 42. The sleeve conductor 43 extends in a direction from the end 47 to the end 48 of the outer conductor 42 and has a length of about λ / 4. The end of the sleeve conductor 43 at a position separated from the end 47 of the outer conductor 42 by about λ / 4 is electrically opened.

  The outer conductor 42 and the sleeve conductor 43 constitute a super top. When the portion of the inner conductor 41 exposed without being covered by the outer conductor 42, that is, the portion of the inner conductor 41 from the position of the end portion 47 of the outer conductor 42 to the end portion 44 is caused to function as a quarter-wavelength nanopole antenna. In addition, the super top formed by the outer conductor 42 and the sleeve conductor 43 prevents a standing wave current (leakage current) from flowing on the surface of the outer conductor 42.

  FIG. 5 is a diagram showing another form of a sleeve antenna which is a comparative example of the antenna 1 according to the present embodiment. Referring to FIG. 5, the sleeve antenna 2 </ b> B is different from the sleeve antenna 2 </ b> A in that a branch conductor 49 is provided instead of the sleeve conductor 43. The length of the branch conductor 49 is about λ / 4. The branch conductor 49 is electrically connected to the outer conductor 42 at the position of the end 47 of the outer conductor 42, and the opposite end of the branch conductor 49 is electrically opened.

  The sleeve antenna shown in FIGS. 4 and 5 is formed by processing a coaxial line (for example, a coaxial cable). In this case, the inner conductor of the coaxial cable and the braided wire (thin knitted thin copper wire) correspond to the inner conductor 41 and the outer conductor 42, respectively. However, manufacturing the sleeve antenna shown in FIG. 4 or FIG. 5 by processing the coaxial cable increases the labor required for processing, and thus the manufacturing cost is considered to increase. On the other hand, the antenna 1 according to the present embodiment includes a radiating element 11 and sleeve conductors 12 and 13 formed of a conductor plate. According to the present embodiment, each element constituting the radiator 2 can be easily formed by processing the metal plate using a known processing method such as pressing. Furthermore, since the waveguide 3 and the reflector 4 are also formed of a conductor plate, these elements can be easily formed. Therefore, according to the present embodiment, the cost required for manufacturing the antenna can be reduced.

  In the sleeve antenna shown in FIGS. 4 and 5, the thickness of the inner conductor 41 is the same between the portion covered by the outer conductor 42 and the portion exposed from the outer conductor 42. On the other hand, in the present embodiment, the length (W1) of the radiating portion 14 in the width direction is made larger than the length (W2) of the feed line 15 in the width direction. While the frequency band of the sleeve antenna shown in FIGS. 4 and 5 is relatively narrow, the frequency band can be expanded more than the sleeve antenna shown in FIGS. 4 and 5 by configuring the radiating element 11 as described above. Can do. This point will be described in detail later. In the present specification, a frequency band is defined as a frequency range in which a value indicating a standing wave ratio (generally referred to as SWR (Standing Wave Ratio) or VSWR (Voltage Standing Wave Ratio)) is a predetermined value or less. .

  FIG. 6 is a diagram showing a three-element Yagi antenna, which is another comparative example of the antenna 1 according to the present embodiment. With reference to FIG. 6, the three-element Yagi antenna 2 </ b> C includes a radiator 52, a director 53, and a reflector 54. In the form shown in FIG. 6, a half-wave dipole antenna is used as the radiator 52. However, in the Yagi antenna, a folded dipole antenna is often used as the radiator. As shown in FIG. 6, in the three-element Yagi antenna, the distance between the radiator and the director and the distance between the radiator and the reflector are both set to λ / 4. Therefore, the total length of the three-element Yagi antenna 2C, that is, the distance between the director 53 and the reflector 54 is about λ / 2.

  On the other hand, according to the present embodiment, the distance d between the director 3 and the reflector 4 is about λ / 4. That is, according to the present embodiment, if the used frequency band is the same, the total length of the antenna can be reduced to about half of the total length of the three-element Yagi antenna.

  A general Yagi antenna uses a half-wave dipole antenna or a folded dipole antenna as a radiator. These antennas are balanced feed type antennas. On the other hand, a coaxial cable generally used as a feed line is an unbalanced feed type feed line. Therefore, in order to connect the half-wave dipole antenna (or the folded dipole antenna) and the coaxial cable, it is necessary to insert a matching unit between them. However, a loss (insertion loss) occurs in the matching unit. In contrast, in the present embodiment, the width W2 of the feed line 15 and the distance between the feed line 15 and the sleeve conductor (distances d3 and d4) are set so that the impedance of the feed line 15 is substantially the same as the impedance of the coaxial line 7. Determined. As a result, the coaxial line can be directly connected to the feed line 15 and the sleeve conductors 12 and 13, so that a matching unit can be dispensed with. That is, there is no insertion loss due to the matching device. Therefore, according to the present embodiment, better performance than the three-element Yagi antenna can be obtained.

  Next, the performance of the antenna 1 according to the present embodiment will be specifically described. The performance of the antenna 1 described below is obtained by configuring the antenna 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 length, width, and distance parameters shown in FIGS. 2 and 3 are designed so that the antenna 1 is an antenna suitable for transmitting and receiving the UHF band radio wave. This frequency band includes the terrestrial digital broadcasting frequency band (470 to 710 MHz) in Japan.

  In the following description, gain, VSWR, front-to-back ratio, and half-value width are shown as the performance of the antenna 1. The higher the numerical value indicating the gain, the better the performance of the antenna. Moreover, it shows that the characteristic of an antenna is excellent, so that the numerical value which shows VSWR is low.

  The front-to-back ratio is defined as the ratio of the radiated electric field in the specified direction (the direction at an angle of 0 degrees) and the maximum radiated electric field in the direction in the range of 180 degrees ± 60 degrees with respect to that direction. A high front-to-back ratio indicates that the gain in the 0 degree direction of the antenna increases, and therefore the directivity of the antenna increases in that direction. The half-value width is an angle width at which the radiation intensity (radiation power) is ½ of the maximum value.

  FIG. 7 is a diagram illustrating measurement results of the gain and VSWR characteristics of the antenna 1. Referring to FIG. 7, solid line A indicates the frequency characteristic of gain, and broken line B indicates the frequency characteristic of VSWR. In the frequency range of 470 to 770 MHz, the gain is about 4.0 (dB) or more. In this frequency range, VSWR is about 2.0.

  FIG. 8 is a diagram illustrating measurement results of the front-rear ratio and the half-value width of the antenna 1. Referring to FIG. 8, solid line C indicates the front-to-back ratio, and broken line D indicates the half width. In the frequency range of 470 to 770 MHz, the front-to-back ratio is about 9.0 (dB) or more, and the half width is smaller than about 70 degrees.

  FIG. 9 is a diagram showing a result of comparing gains of the antenna 1 according to the present embodiment and the three-element Yagi antenna shown in FIG. Referring to FIG. 9, curve E represents the gain of antenna 1, and curve F represents the gain of 3-element Yagi antenna 2C. In the frequency range of 470 to 770 MHz, the antenna 1 according to the present embodiment can obtain a higher gain than the three-element Yagi antenna. This indicates that the antenna 1 according to this embodiment has higher performance than a general three-element Yagi antenna. Furthermore, the total length (about λ / 4) of the antenna 1 according to the present embodiment is shorter than the total length (about λ / 2) of a general three-element Yagi antenna. Therefore, it can be seen from FIG. 9 that according to the present embodiment, a small and high-performance antenna can be realized as compared with a general three-element Yagi antenna.

  The gain of the three-element Yagi antenna shown in FIG. 9 is obtained in a state where a matching unit is inserted between the radiator and the coaxial cable. The insertion loss of the matching device is generally about 0.5 (dB). Therefore, if there is no insertion loss of the matching unit, the gain of the three-element Yagi antenna is considered to be 0.5 (dB) higher than the value shown in FIG. However, the gain measurement result shown in FIG. 9 shows that even if it is assumed that there is no insertion loss of the matching unit, the antenna 1 according to the present embodiment can obtain a higher gain than the normal three-element Yagi antenna. It is shown that.

  Further, according to the present embodiment, the frequency band of the antenna can be expanded as compared with the sleeve antenna shown in FIGS. The characteristics of the λ / 4 sleeve antenna shown in FIGS. 4 and 5 are theoretically equivalent to the characteristics of the λ / 4 monopole antenna or the half-wave dipole antenna. Therefore, the result of verifying the characteristics of the half-wave dipole antenna will be described below.

  FIG. 10 is a schematic diagram of a half-wave dipole antenna. Referring to FIG. 10, half-wave dipole antenna 2D includes linear radiating elements DA and DB arranged on the same straight line. The distance from the tip of the radiating element DA to the tip of the radiating element DB is the total length Ld of the half-wave dipole antenna 2D. Ld is about half the resonance wavelength of the half-wave dipole antenna.

  FIG. 11 is a diagram showing the VSWR characteristics of the half-wave dipole antenna 2D shown in FIG. FIG. 11A is a diagram showing the VSWR characteristics of the half-wave dipole antenna 2D when Ld shown in FIG. 10 is set to about 280 mm. FIG. 11B is a diagram showing the VSWR characteristics of the half-wavelength dipole antenna 2D when Ld is set to about 230 mm. FIG. 11C is a diagram showing the VSWR characteristics of the half-wave dipole antenna 2D when Ld shown in FIG. 10 is set to about 200 mm.

  Since the frequency range where the value of VSWR is 3.0 or less is a practical frequency range of the antenna, this frequency range is defined as the frequency band of the antenna. As shown in FIGS. 11 (A) to 11 (C), in order to make the value of VSWR 3.0 or less in the UHF television broadcast frequency band (470-770 MHz) in Japan, the lengths are different from each other. Three types of half-wave dipole antennas are required.

  On the other hand, as shown in FIG. 7, according to the present embodiment, VSWR can be reduced to 3.0 or less over the UHF band (470 to 770 MHz) using one type of antenna. That is, according to the antenna of the present embodiment, the frequency band can be expanded compared to the conventional λ / 4 sleeve antenna (same for half-wave dipole antenna or λ / 4 monopole antenna).

(Modification of antenna of this embodiment)
FIG. 12 is a diagram illustrating a first modification of the antenna of the present embodiment. FIG. 12A is a perspective view of an antenna 1A according to the first modification. FIG. 12B is a side view of the antenna 1A.

  Referring to FIG. 12, antenna 1 </ b> A is different from antenna 1 in that a radiator 21 is provided instead of radiator 2. Radiator 21 differs from radiator 2 in that it includes sleeve conductor 63 instead of sleeve conductor 13. Since the configuration of the other part of antenna 1A is similar to the configuration of the corresponding part of antenna 1, the following description will not be repeated.

  The sleeve conductor 63 is formed in the same shape as the sleeve conductor 12 by folding back one conductor plate. The configuration of the sleeve conductor 63 will be described in detail. The sleeve conductor 63 includes plate-like portions 66 and 67 arranged in parallel to the main surface of the planar conductor (the surface opposite to the surface facing the plate-like portion 16). And a connecting portion 68 for connecting the plate-like portions 66 and 67.

  The plate-like portion 66 includes an end portion 66a located on the side closer to the radiating portion 14 in the X direction and an end portion 66b located on the side farther from the radiating portion 14 in the X direction. The plate-like portion 67 includes an end portion 67a located on the side closer to the radiating portion 14 in the X direction and an end portion 67b located on the side farther from the radiating portion 14 in the X direction. The connecting portion 68 connects the end portions of the plate-like portions 66 and 67 closer to the radiating portion 14, that is, the end portions 66a and 67a. On the other hand, the end portions 66b and 67b are not connected to each other. Although not shown in FIG. 12B, when the outer conductor of the coaxial line is connected to the sleeve conductors 12 and 63, the outer conductors are the end portion 16b of the sleeve conductor 12 and the end portion 66b of the sleeve conductor 63. Connected to.

  According to the configuration shown in FIG. 12, in order to obtain the same characteristics as the antenna 1, the shortest distance (d6) between the plate-like portion 67 and the reflector 4 is set to the distance d5 (sleeve conductor) shown in FIG. It is conceivable that the distance is set to the same level as the shortest distance between 13 and the reflector 4. In this case, since the shortest distance d2 between the radiating element 11 and the reflector 4 is slightly larger than d2 determined by the configuration shown in FIG. 2, the total length of the antenna 1A (the distance between the waveguide 3 and the reflector 4). d) is slightly larger than the total length of the antenna 1, but the total length of the antenna 1A is about λ / 4. The distance d1 is set smaller than the distance d2. As described above, the antenna 1A according to this modification can obtain the same performance as the antenna 1. Therefore, a small and high-performance antenna can be obtained also by the first modification.

  FIG. 13 is a diagram illustrating a second modification of the antenna of the present embodiment. FIG. 13A is a perspective view of an antenna 1B according to a second modification. FIG. 13B is a side view of the antenna 1B.

  Referring to FIG. 13, antenna 1 </ b> B is different from antenna 1 in that a radiator 22 is provided instead of radiator 2. The radiator 22 is different from the radiator 2 in that the arrangement of the sleeve conductors 12 and 13 is replaced with the arrangement of the sleeve conductors 12 and 13 in the radiator 2. The sleeve conductors 12 and 13 are arranged in parallel and are formed in a flat plate shape. Since the configuration of the other part of antenna 1B is the same as the configuration of the corresponding part of antenna 1, the following description will not be repeated. Similar to the antenna 1A shown in FIG. 12, even in such a configuration, the total length (distance d) of the antenna 1B is slightly larger than the total length (distance d) of the antenna 1, but the length is about λ / 4. Degree. The distance d1 is set smaller than the distance d2. Therefore, a small and high-performance antenna can be realized also by the second modification.

  FIG. 14 is a diagram illustrating a third modification of the antenna of the present embodiment. FIG. 14A is a perspective view of an antenna 1C according to a third modification. FIG. 14B is a side view of the antenna 1C.

  Referring to FIG. 14, antenna 1 </ b> C is different from antenna 1 in that a radiator 23 is provided instead of radiator 2. Radiator 23 differs from radiator 2 in that it includes sleeve conductor 62 instead of sleeve conductor 12. Since the configuration of the other part of antenna 1C is similar to the configuration of the corresponding part of antenna 1, the following description will not be repeated.

  The sleeve conductor 62 is formed in a flat plate shape like the sleeve conductor 13 and is arranged in parallel. The sleeve conductor 62 has an end portion 62a positioned on the side closer to the radiating portion 14 in the X direction and an end portion 62b positioned on the side farther from the radiating portion 14 in the X direction. The end 62a is electrically opened. Further, the end portion 13a of the sleeve conductor 13 is also electrically opened. Although not shown, the ends 62b and 13b are connected to the outer conductor of the coaxial line. The distance d1 is set smaller than the distance d2. Even with such a configuration, a small and high-performance antenna can be realized in the same manner as the antennas 1, 1A and 1B.

  FIG. 15 is a diagram illustrating a fourth modification of the antenna of the present embodiment. Referring to FIG. 15, antenna 1 </ b> D is different from antenna 1 in that it includes a director 3 </ b> A instead of director 3. Since the configuration of the other part of antenna 1D is the same as the configuration of the corresponding part of antenna 1, the following description will not be repeated.

  3 A of directors are comprised with the conductor board similarly to the director 3, and have rectangular shape. When the length in the width direction (Y direction) of the director 3A is defined as the width We, the width We is preferably equal to or less than the length in the width direction of the radiating portion 14 (Wf shown in FIG. 15). As a result, it is possible to ensure the same performance as the antenna 1. According to this modification, a small and high-performance antenna can be realized in the same manner as the antennas 1 and 1A to 1C.

  In the above description, the shape of the main surface of the conductor plate forming the waveguide is a cross or a rectangle. However, the shape of the waveguide is not limited to this, but is a polygon. I just need it. However, the shape of the director (the shape of the main surface of the conductor plate) is a polygon including a portion where the length in the width direction of the portion facing the radiating portion 14 is smaller than the length in the width direction of the radiating portion 14. Preferably there is. Thereby, the performance of the antenna 1 can be improved.

  Based on the above description, the configuration of the antenna according to the present embodiment will be described generally. The antenna includes a radiator, a director, and a reflector. The radiator includes a radiating element including a radiating portion and a feed line connected to the radiating portion, and first and second sleeve conductors. The radiating portion and the feed line are integrally formed by a planar conductor. Moreover, if the direction orthogonal to the extending direction of the feed line is defined as the width direction, the length in the width direction of the radiating portion is larger than the length in the width direction of the feed line. The first sleeve conductor is formed by a first conductor plate whose length in the width direction is larger than the length in the width direction of the feed line, and faces the region where the feed line is formed on the main surface of the planar conductor. The second sleeve conductor is formed by a second conductor plate having a length in the width direction that is greater than the length in the width direction of the feed line, and the second sleeve conductor has a second length with respect to the planar conductor so as to sandwich the feed line with the first sleeve conductor. 1 is provided on the opposite side of the sleeve conductor. The antenna according to this embodiment has the above structure, and thus is small and has high performance.

  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.

1 is a perspective view of an antenna 1 according to an embodiment of the present invention. It is a side view of the antenna 1 shown in FIG. It is the top view which showed the element which comprises the antenna 1 shown in FIG. It is the figure which showed one form of the sleeve antenna which is a comparative example of the antenna 1 which concerns on this Embodiment. It is the figure which showed another form of the sleeve antenna which is a comparative example of the antenna 1 which concerns on this Embodiment. It is the figure which showed the 3 element Yagi antenna which is the other comparative example of the antenna 1 which concerns on this Embodiment. It is a figure which shows the measurement result of the gain and VSWR characteristic of the antenna. It is a figure which shows the measurement result of the front-back ratio and the half value width of the antenna. It is a figure which shows the result of having compared the gain with the antenna 1 which concerns on this Embodiment, and the 3 element Yagi antenna shown in FIG. It is the schematic of a half-wave dipole antenna. It is the figure which showed the VSWR characteristic of the half-wavelength dipole antenna 2D shown in FIG. It is a figure which shows the 1st modification of the antenna of this embodiment. It is a figure which shows the 2nd modification of the antenna of this embodiment. It is a figure which shows the 3rd modification of the antenna of this embodiment. It is a figure which shows the 4th modification of the antenna of this embodiment.

Explanation of symbols

  1, 1A to 1D antenna, 2, 21 to 23, 52 radiator, 2A, 2B sleeve antenna, 2C three-element Yagi antenna, 2D half-wave dipole antenna, 3, 3A, 53 waveguide, 4, 54 reflector, 5, 6 Radio wave, 7, 40 Coaxial line, 8, 41 Inner conductor, 9, 42 Outer conductor, 11 Radiating element, 12, 13, 43, 62, 63 Sleeve conductor, 13a, 13b, 16a, 16b, 17a, 17b , 44, 45, 47, 48, 62a, 62b end, 14 radiating section, 15 feed line, 16, 17, 66, 67 plate-shaped section, 18, 68 connecting section, 31 center section, 32, 33 protruding section, 46 Inner surface, 49 Branch conductor, 66a, 66b, 67a, 67b End, DA, DB Radiating element.

Claims (7)

An antenna,
A radiating element including a radiating portion and a feed line connected to the radiating portion,
The radiating portion and the feed line are integrally formed by a planar conductor,
When the direction perpendicular to the extending direction of the feed line is defined as the width direction, the length in the width direction of the radiating portion is larger than the length in the width direction of the feed line,
The antenna is
A first sleeve that is formed by a first conductor plate having a length in the width direction that is larger than a length in the width direction of the feed line, and that is opposed to a region where the feed line is formed on the main surface of the planar conductor. Conductors,
The second conductor plate is formed by a second conductor plate having a length in the width direction that is larger than a length in the width direction of the feed line, and is first with respect to the planar conductor so as to sandwich the feed line together with the first sleeve conductor. A second sleeve conductor provided on the opposite side of the sleeve conductor;
A director provided on the same side as the first sleeve conductor with respect to the planar conductor and on the outer side of the first sleeve conductor with respect to the planar conductor;
The antenna further comprising a reflector provided on the same side as the second sleeve conductor with respect to the planar conductor and on the outer side of the second sleeve conductor with respect to the planar conductor.   The antenna according to claim 1, wherein a distance between the planar conductor and the director is shorter than a distance between the planar conductor and the reflector. One of the first and second sleeve conductors is
Each is arranged in parallel to the main surface of the planar conductor, and in the extending direction of the feeder line, the first end located on the side closer to the radiating portion in the extending direction of the feeder line and the extending direction of the feeder line First and second plate-like parts having a second end located on the side far from the radiation part;
A connecting portion that connects the first end portions of the first and second plate-shaped portions;
The other of the first and second sleeve conductors is
The antenna according to claim 1 or 2, wherein the main surface is a conductor arranged parallel to the planar conductor and formed in a flat plate shape. Each of the first and second sleeve conductors includes:
First and second plate-like portions respectively disposed parallel to the main surface of the planar conductor;
A connecting portion for connecting the first and second plate-like portions;
Each of the first and second plate-like portions is
A first end located on the side closer to the radiating portion in the extending direction of the feeder line;
A second end located on the side farther from the radiating portion in the extending direction of the feeder line;
The antenna according to claim 1 or 2, wherein the connection portion connects the first end portions of the first and second plate-like portions.   The antenna according to claim 1 or 2, wherein each of the first and second sleeve conductors is a conductor having a main surface disposed in parallel with the planar conductor and formed in a flat plate shape.   The at least part of the said waveguide opposes the said radiation | emission part, and the length of the said width direction is smaller than the length of the said width direction of the said radiation | emission part in any one of Claim 1 to 5 The described antenna.   The antenna according to claim 6, wherein the director is formed of a conductor plate and has a polygonal surface.

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