(19)
(11)EP 4 002 584 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
05.10.2022 Bulletin 2022/40

(21)Application number: 21206904.1

(22)Date of filing:  08.11.2021
(51)International Patent Classification (IPC): 
H01Q 1/32(2006.01)
H01Q 19/185(2006.01)
H01Q 9/28(2006.01)
(52)Cooperative Patent Classification (CPC):
H01Q 1/32; H01Q 9/28; H01Q 19/185

(54)

THIN ANTENNA

DÜNNE ANTENNE

ANTENNE MINCE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 11.11.2020 JP 2020187827

(43)Date of publication of application:
25.05.2022 Bulletin 2022/21

(73)Proprietor: Yazaki Corporation
Minato-ku Tokyo 108-8333 (JP)

(72)Inventor:
  • Tsuchiya, Kazuhiko
    Shizuoka, 410-1194 (JP)

(74)Representative: Grünecker Patent- und Rechtsanwälte PartG mbB 
Leopoldstraße 4
80802 München
80802 München (DE)


(56)References cited: : 
JP-A- 2015 103 912
US-A1- 2009 289 852
US-A- 5 438 338
US-A1- 2013 178 170
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    TECHNICAL FIELD



    [0001] The present invention relates to a thin antenna that can transmit and receive a vertical polarization.

    BACKGROUND



    [0002] As a conventional thin antenna, there has been known an antenna device disclosed in Patent Document 1 (JP 2009-17250). The antenna device is an inverted L-shaped antenna whose the height is reduced. The antenna device includes a base material, an antenna element, and a matching circuit. The base material is provided with a feeding point. The antenna element stands on the base material. The matching circuit is disposed between the feeding point and the antenna element and performs impedance matching. The antenna device has a round directional radiation pattern with little concavity in a vertical polarization (V polarization) relative to a horizontal plane (X-Y plane).
    Further prior art is known from documents US 5 438 338 A, US 2009/289852 A1, JP 2015 103 912 A and US 2013/178 170 A1.

    SUMMARY



    [0003] However, an average gain of the antenna device is -13.39 dBi in the vertical polarization, which has significantly degraded the radiation characteristics.

    [0004] The present invention has been made in view of such a conventional problem, and it is an object of the present invention to provide a thin antenna whose the height is reduced, suitable for use as an on-vehicle antenna having good radiation characteristics in a vertical polarization relative to a horizontal plane.

    [0005] According to the invention, there is provided a thin antenna including the features of claim 1.

    [0006] According to the invention, it is possible to provide a thin antenna whose height is reduced, suitable for use as an on-vehicle antenna having good radiation characteristics in a vertical polarization relative to a horizontal plane.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0007] 

    FIG. 1 is a perspective view of a thin antenna according to the present embodiment.

    FIG. 2 is a cross-sectional view of the thin antenna along the line II-II of FIG. 1.

    FIG. 3 is an exploded view of the thin antenna.

    FIG. 4 is a diagram showing an average gain in a vertical polarization relative to a horizontal plane in the thin antenna.

    FIG. 5 is a diagram showing a radiation pattern of the thin antenna when a lower ground plane is the same size as an upper ground plane.

    FIG. 6 is a diagram showing a radiation pattern of the thin antenna when the lower ground plane is larger than the upper ground plane.

    FIG. 7 is a diagram showing a radiation pattern of the thin antenna when the upper ground plane is larger than the lower ground plane.


    DETAILED DESCRIPTION



    [0008] A thin antenna according to an embodiment will be described below with reference to the accompanying drawings. Note that the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

    [0009] As illustrated in FIGS. 1 to 3, a thin antenna 10 includes an antenna element 11, a pair of insulating spacers (first and second spacers) 12, 13, and a pair of ground planes (first and second ground planes) 14, 15. The ground planes 14, 15 are formed larger than a top surface 11a and a bottom surface 11b of the antenna element 11, respectively. It is noted that the ground planes 14, 15 are also referred to as upper and lower ground planes, respectively.

    [0010] As illustrated in FIG. 3, the antenna element 11 is formed in a solid circular column shape and is made of a conductive material such as metal (e.g., copper or iron).

    [0011] An X-direction shown in FIGS. 1 to 3 is parallel to a first radial direction RD1 of the antenna element 11 (see FIG. 3). The X-direction is also parallel to first sides 141, 141 of the ground plane 14 and first sides 151, 151 of the ground plane 15 in the thin antenna 10. A Y-direction shown in FIGS. 1 to 3 is perpendicular to the X-direction and is parallel to a second radial direction RD2 of the antenna element 11 (see FIG. 3). The Y-direction is also parallel to second sides 142, 142 of the ground plane 14 and second sides 152, 152 of the ground plane 15 in the thin antenna 10. A Z-direction shown in FIGS. 1 to 3 is perpendicular to the X-direction and the Y-direction and is parallel to an axial direction AD1 of the antenna element 11 (see FIG. 3). The Z-direction is also perpendicular to an X-Y plane of each of the ground planes 14, 15 in the thin antenna 10. It is noted that II-II line in FIG 1 is parallel to the second sides 142, 142 of the ground plane 14 and connects the midpoints of the first sides 141, 141 of the ground plane 14 to a center of the ground plane 14.

    [0012] The antenna element 11 has the top surface 11a formed in a circular shape and located on a + side of the Z-direction, and the bottom surface 11b formed in a circular shape and located on a - side of the Z-direction. The top surface 11a faces the bottom surface 11b. In the thin antenna 10, the antenna element 11 is arranged such that the top surface 11a and the bottom surface 11b of the antenna element 11 face the ground planes 14, 15 via the spacers 12, 13, respectively. In other words, the antenna element 11 is sandwiched between the ground planes 14, 15 via the spacers 12, 13 in the Z-direction.

    [0013] As illustrated in FIG. 2, a feeding point 16 to be connected to a feeding cable 17, which will be described later, is provided on the bottom surface 11b of the antenna element 11. A power is fed at the bottom surface 11b (bottom portion) of the antenna element 11. In this embodiment, the feeding point 16 is located at a center of the bottom surface 11b.

    [0014] As illustrated in FIG. 2, the feeding cable 17 is a coaxial cable and includes a core wire 17a, an insulating coating 17b with which the core wire 17a is covered, a braid 18 with which the insulating coating 17b is covered. When the feeding cable 17 is connected to the thin antenna 10, the core wire 17a is connected to the feeding point 16 on the bottom surface 11b of the antenna element 11 and the braid 18 is connected to a bottom surface 15b of the ground plane 15. In this state, a distal end of the core wire 17a of the feeding cable 17 is inserted into an insertion hole 13c of the spacer 13 which will be described later, and a distal end of the insulating coating 17b of the feeding cable 17 is inserted into an insertion hole 15c of the ground plane 15 which will be described later.

    [0015] As illustrated in FIG. 2, each of the spacers 12, 13 is formed in an annular thin plate shape and is made of an insulating material such as resin (e.g., synthetic resin). In this embodiment, an outer diameter and an inner diameter of the spacer 12 are 20 mm and 10 mm, respectively. Similarly, an outer diameter and an inner diameter of the spacer 13 are 20 mm and 10 mm, respectively. It is noted that the outer diameter and the inner diameter of each of the spacers 12 and 13 are not limited to 20 mm and 10 mm, respectively.

    [0016] As illustrated in FIG. 3, the spacer 12 has a top surface 12a formed in an annular shape and located on the + side of the Z-direction, a bottom surface 12b formed in an annular shape and located on the - side of the Z-direction, and the insertion hole 12c penetrating through the spacer 12 along the Z-direction. The spacer 12 is attached on a bottom surface 14b of the ground plane 14, which will be described later, using a predetermined means. In the thin antenna 10, the top surface 12a of the spacer 12 contacts the bottom surface 14b of the ground plane 14 and the bottom surface 12b of the spacer 12 contacts the top surface 11a of the antenna element 11. When viewed from the X-Y plane, a center of the insertion hole 12c overlaps a center of the bottom surface 14b of the ground plane 14 and a center of the top surface 11a of the antenna element 11.

    [0017] Similarly, the spacer 13 has a top surface 13a formed in an annular shape and located on the + side of the Z-direction, a bottom surface 13b formed in an annular shape and located on the - side of the Z-direction, and the insertion hole 13c penetrating through the spacer 13 along the Z-direction. The spacer 13 is attached on a top surface 15a of the ground plane 15, which will be described later, using a predetermined means. In the thin antenna 10, the top surface 13a of the spacer 13 contacts the bottom surface 11b of the antenna element 11 and the bottom surface 13b of the spacer 13 contacts the top surface 15a of the ground plane 15. When viewed from the X-Y plane, a center of the insertion hole 13c overlaps a center of the insertion hole 15c of the ground plane 15 and a center (feeding point 16) of the bottom surface 11b of the antenna element 11.

    [0018] Although each of the spacers 12, 13 is formed in an annular shape in this embodiment, one of the spacers 12, 13 through which the feeding cable 17 is not inserted, may be formed in a disk shape instead of the annular shape. Also, when viewed from the X-Y plane, the spacers 12, 13 are smaller than the ground planes 14, 15, respectively. More specifically, the top surface 12a of the spacer 12 and the bottom surface 13b of the spacer 13 are smaller than the bottom surface 14b of the ground plane 14 and the top surface 15a of the ground plane 15, respectively. In this case, it is preferable that the spacers 12, 13 are smaller than the antenna element 11 when viewed from the X-Y plane. More specifically, it is preferable that the bottom surface 12b of the spacer 12 and the top surface 13a of the spacer 13 are smaller than the top surface 11a of the antenna element 11 and the bottom surface 11b of the antenna element 11, respectively. It is noted that each of the spacers 12, 13 may be larger than the antenna element 11 when viewed from the X-Y plane.

    [0019] As illustrated in FIGS. 1 and 2, each of the ground planes 14, 15 is formed in a square thin plate shape and is made of a conductive material such as metal (e.g., copper or iron). In this embodiment, a length L1 of each of the first sides 141, 141 and the second sides 142, 142 of the ground plane 14 is 200 mm. Similarly, a length L2 of each of the first sides 151, 151 and the second sides 152, 152 of the ground plane 15 is 200 mm. It is noted that the length of each of the first sides 141, 141, 151, 151 and the second sides 142, 142, 152, 152 is not limited to 200 mm.

    [0020] The ground plane 14 has a top surface 14a formed in a square shape and located on the + side of the Z-direction, and the bottom surface 14b formed in a square shape and located on the - side of the Z-direction. The ground plane 15 has the top surface 15a formed in a square shape and located on the + side of the Z-direction, a bottom surface 15b formed in a square shape and located on the - side of the Z-direction, and the insertion hole 15c penetrating through the ground plane 15 along the Z-direction.

    [0021] In this embodiment, the ground plane 15 is a ground face (ground plane). For example, when the thin antenna 10 is mounted to a roof of a vehicle (not illustrated) or the like, the ground plane 15 is grounded on the roof or a metal body of the vehicle.

    [0022] The ground planes 14, 15 are larger than the antenna element 11 when viewed from the X-Y plane. More specifically, the top surface 14a and the bottom surface 14b of the ground plane 14 are larger than the top surface 11a of the antenna element 11. The top surface 15a and the bottom surface 15b of the ground plane 15 are larger than the bottom surface 11b of the antenna element 11.

    [0023] The thin antenna 10 is formed with a height H less than λ/4 in the Z-direction when a wavelength of an antenna frequency (electromagnetic wave) to be used in the thin antenna 10 is λ. More specifically, the thin antenna 10 is a low-profile antenna with the height H of about 11 mm. It is noted that the height H is a dimension that includes the height of the antenna element 11, thicknesses of the spacers 12, 13, and a thickness of the ground plane 14 in the Z direction. In other words, the height H is the height of the thin antenna 10 in the Z-direction, excluding a thickness of the ground plane 15.

    [0024] In this embodiment, the antenna element 11, the spacers 12, 13, and the ground planes 14, 15 have the above-described shapes and dimensions when the thin antenna 10 is used for a frequency band between 0.815 GHz and 0.875 GHz. The shapes and dimensions of the antenna element 11, the spacers 12, 13, and the ground planes 14, 15 are adequately changed according to a desired frequency.

    [0025] According to this embodiment, as illustrated in FIG. 2, the height H of the thin antenna 10 is reduced to less than λ/4 by the combination of the antenna element 11, the spacers 12, 13, and the ground planes 14, 15. The diameter of the antenna element 11 is determined according to a desired bandwidth. In other words, the thin antenna 10 is a low-profile antenna with a height H of about 11 mm.

    [0026] As illustrated in FIG. 4, an analysis of an average gain in a vertical polarization (V polarization) relative to a horizontal plane (X-Y plane) shows that an average gain of the thin antenna 10 is more than -3 dBi in the frequency band between 0.815 GHz and 0.875 GHz. This enables the thin antenna 10 to have good radiation characteristics in the vertical polarization relative to the horizontal plane.

    [0027] By forming the ground plane 14 and the ground plane 15 to the same size as each other, as illustrated in FIG. 5, a radiation pattern (radiation characteristics) on the + side of the Z-direction is the same as a radiation pattern (radiation characteristics) on the - side of the Z-direction in the thin antenna 10. This enables good communication in the horizontal plane.

    [0028] Thus, according to this embodiment, the radiation characteristics in the vertical polarization relative to the horizontal plane can be made good while the height H of the thin antenna 10 is made low. In addition, by making the height H of the thin antenna 10 low, it is possible to install the thin antenna 10 in a limited space. Furthermore, it is possible to perform good communication (transmission and reception) in the horizontal plane. Therefore, the thin antenna 10 whose the height H is reduced, is suitable for use as an on-vehicle antenna.

    [0029] Although the ground plane 14 and the ground plane 15 are formed to the same size as each other in this embodiment, the ground plane 15 may be formed larger than the ground plane 14. For example, the ground plane 14 is formed in a square shape with a side length L1 of 200 mm, and the ground plane 15 is formed in a square shape with a side length L2 of 600 mm. In this case, as illustrated in FIG. 6, a radiation pattern (radiation characteristics) that radiates strongly upward can be obtained. Furthermore, if the ground plane 15 is formed larger than the ground plane 14, a roof of a vehicle can be used as a ground plane of the thin antenna 10. In this case, the feeding point 16 is provided on the bottom surface 11b of the antenna element 11.

    [0030] Although the ground plane 14 and the ground plane 15 are formed to the same size as each other in this embodiment, the ground plane 14 may be formed larger than the ground plane 15. For example, the ground plane 14 is formed in a square shape with a side length L1 of 600 mm, and the ground plane 15 is formed in a square shape with a side length L2 of 200 mm. In this case, as illustrated in FIG. 7, a radiation pattern (radiation characteristics) that radiates strongly downward can be obtained. In this case, the feeding point 16 is provided on the top surface 11a of the antenna element 11.

    [0031] It is preferable to provide the feeding point 16 on the larger of the two ground planes 14, 15. Since a radiation power is more stronger in a direction of the smaller of the two ground planes 14, 15, a radiation plane will not be affected by the feeding cable 17 and the like by providing the feeding point 16 on the larger of the two ground planes 14, 15.

    [0032] Although the embodiment is described above, the invention is not limited to it. Various modifications are possible within the scope of the invention as defined by the claims.

    [0033] According to this embodiment, the antenna element 11 is made of the conductive metal and formed in the solid circular column shape, but the invention is not limited to this. The antenna element 11 may be made of the conductive metal and formed in a prismatic column shape (e.g., rectangular column shape) or the like. The antenna element 11 may also be formed in a hollow circular column shape, as long as the top surface 11a and the bottom surface 11b thereof are closed. The antenna element 11 only needs to be formed in a column shape. It is noted that the term "column" encompasses both of the circular column and the prismatic column.

    [0034] According to this embodiment, each of the ground planes 14, 15 is formed in the square thin plate shape that is larger than the top surface 11a and the bottom surface 11b of the antenna element 11, but the invention is not limited to this. Each of the ground planes 14, 15 may be formed in a circular (round) or polygonal thin plate shape that is larger than the top surface 11a and the bottom surface 11b of the antenna element 11. In a case where a vehicle has a plastic roof, any one of the ground planes 14, 15 may be made up of a whole or part of a body of the vehicle. In a case where a vehicle has a metal roof, any one of the ground planes 14, 15 may be composed of a whole or part of the roof of the vehicle.

    [0035] Furthermore, according to this embodiment, each of the spacers 12, 13 is formed in the annular thin plate shape, but the invention is not limited to this. Each of the spacers 12, 13 may be formed in a polygonal thin plate shape. Also, an outer shape of each of the spacers 12, 13 may be formed in a polygonal shape.


    Claims

    1. A thin antenna (10) comprising:

    an antenna element (11) formed in a column shape, and having a top surface (11a) and a bottom surface (11b) facing each other;

    a first spacer (12) made of an insulating material;

    a second spacer (13) made of an insulating material;

    a first ground plane (14) formed larger than the top surface (11a) of the antenna element (11); and

    a second ground plane (15) formed larger than the bottom surface (11b) of the antenna element (11),

    wherein the first spacer (12) is formed smaller than a bottom surface (14b) of the first ground plane (14),

    the second spacer (13) is formed smaller than a top surface (15a) of the second ground plane (15),

    the first ground plane (14) is disposed to face the top surface (11a) of the antenna element (11) via the first spacer (12),

    the second ground plane (15) is disposed to face the bottom surface (11b) of the antenna element (11) via the second spacer (13), and

    a power is fed at one of the top surface (11a) and the bottom surface (11b) of the antenna element (11).


     
    2. The thin antenna (10) according to claim 1, wherein the antenna element (11) is made of a conductive metal and formed in a circular column shape, and
    the first ground plane (14) and the second ground plane (15) are the same size as each other.
     
    3. The thin antenna (10) according to claim 1, wherein one of the first ground plane (14) and the second ground plane (15) is larger than the other of the first ground plane (14) and the second ground plane (15).
     
    4. A vehicle comprising the thin antenna (10) according to claim 3, wherein the one of the first ground plane (14) and the second ground plane (15) is made up of a whole or part of a body of the vehicle.
     


    Ansprüche

    1. Eine dünne Antenne (10), aufweisend:

    ein Antennenelement (11) das in einer Säulengestalt geformt ist, und eine obere Fläche (11a) und eine Bodenfläche (11b) hat die sich einander gegenüberliegen;

    einen ersten Abstandshalter (12) der aus isolierendem Material hergestellt ist;

    einen zweiten Abstandshalter (13) der aus isolierendem Material hergestellt ist;

    eine erste Grundebene (14) die größer als die obere Fläche (11a) des Antennenelements (11) geformt ist; und

    eine zweite Grundebene (15) die größer als die Bodenfläche (11b) des Antennenelements (11) geformt ist,

    wobei der erste Abstandshalter (12) kleiner als eine Bodenfläche (14b) der ersten Grundebene (14) geformt ist,

    der zweite Abstandshalter (13) kleiner als eine obere Fläche (15a) der zweiten Grundebene (15) geformt ist,

    die erste Grundebene (14) gegenüber der oberen Fläche (11a) des Antennenelements (11) mittels des ersten Abstandshalters (12) angeordnet ist,

    die zweite Grundebene (15) gegenüber der Bodenfläche (11b) des Antennenelements (11) mittels des zweiten Abstandshalters (13) angeordnet ist, und

    eine Leistung an die obere Fläche (11a) oder an die Bodenfläche (11b) des Antennenelements (11) zugeführt wird.


     
    2. Die dünne Antenne (10) gemäß Anspruch 1, wobei das Antennenelement (11) aus leitfähigem Metall hergestellt ist und in einer kreisförmigen Säulengestalt geformt ist, und die erste Grundebene (14) und die zweite Grundebene (15) gegenseitig die gleiche Größe haben.
     
    3. Die dünne Antenne (10) gemäß Anspruch 1, wobei eine der ersten Grundebene (14) und der zweiten Grundebene (15) größer als die andere der ersten Grundebene (14) und der zweiten Grundebene (15) ist.
     
    4. Ein Fahrzeug aufweisend die dünne Antenne (10) gemäß Anspruch 3, wobei die eine der ersten Grundebene (14) und der zweiten Grundebene (15) teilweise oder vollständig Teil einer Karosse des Fahrzeugs ist.
     


    Revendications

    1. Antenne mince (10) comprenant :

    un élément d'antenne (11) conformé comme une colonne, et comportant une surface supérieure (11a) et une surface inférieure (11b) qui se font face ;

    une première entretoise (12) constituée d'un matériau isolant ;

    une deuxième entretoise (13) constituée d'un matériau isolant ;

    un premier plan de base (14) formé de manière à être plus grand que la surface supérieure (11a) de l'élément d'antenne (11) ; et

    un deuxième plan de base (15) formé de manière à être plus grand que la surface inférieure (11b) de l'élément d'antenne (11),

    dans laquelle la première entretoise (12) est formée de manière à être plus petite que la surface inférieure (14b) du premier plan de base (14),

    la deuxième entretoise (13) est formée de manière à être plus petite que la surface supérieure (15a) du deuxième plan de base (15),

    le premier plan de base (14) est disposé pour faire face à la surface supérieure (11a) de l'élément d'antenne (11) via la première entretoise (12),

    le deuxième plan de base (15) est disposé pour faire face à la surface inférieure (11b) de l'élément d'antenne (11) via la deuxième entretoise (13), et

    une alimentation est fournie à une surface parmi la surface supérieure (11a) et la surface inférieure (11b) de l'élément d'antenne (11).


     
    2. Antenne mince (10) selon la revendication 1, dans laquelle l'élément d'antenne (11) est constitué d'un métal conducteur et conformé comme une colonne circulaire, et
    le premier plan de base (14) et le deuxième plan de base (15) sont de même taille.
     
    3. Antenne mince (10) selon la revendication 1, dans laquelle un plan parmi le premier plan de base (14) et le deuxième plan de base (15) est supérieur à l'autre plan parmi le premier plan de base (14) et le deuxième plan de base (15).
     
    4. Véhicule comprenant une antenne mince (10) selon la revendication 3, dans lequel ledit plan parmi le premier plan de base (14) et le deuxième plan de base (15) est constitué comme un corps du véhicule, en tout ou en partie.
     




    Drawing

















    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description