JP6352348B2 - Film antenna and antenna device - Google Patents

Description

  The present invention relates to a film antenna and an antenna device having a plurality of resonance frequencies.

  Patent Document 1 describes a film antenna including a ground plate and a radiating element formed on the surface of a dielectric substrate (see FIG. 3 of Patent Document 1).

  A film antenna including a radiating element constituted by a plurality of sub-elements having different lengths is known. Since such a film antenna operates at a plurality of resonance frequencies corresponding to the lengths of the plurality of sub-elements, the operating band can be widened.

  As a demand for such a film antenna, it is possible to reduce the space required for mounting the film antenna. When the space required for mounting the film antenna is narrowed, it is preferable to employ a flexible substrate having flexibility as the dielectric substrate, and a conductor foil as the ground plate and the radiation element. Since such a film antenna can be bent, it can be mounted in a narrow space.

JP 2007-235404 A (published September 13, 2007)

  However, the inventors of the present application show that when such a film antenna is bent, the radiation characteristics of the film antenna deteriorate due to the proximity of the radiating elements, the ground plates, or the radiating element and the ground plate. I found it.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a film antenna that operates at a plurality of resonance frequencies and can be mounted in a narrow space while suppressing deterioration of radiation characteristics. It is to provide an antenna.

  In order to solve the above problems, a film antenna according to an aspect of the present invention includes a first radiating element having a first resonance frequency, and a second resonance frequency that is higher than the first resonance frequency. The first radiating element is disposed along a first plane, and the second radiating element includes at least a second plane that intersects the first plane. The first radiating element is disposed along a third plane that faces the first plane and intersects the second plane, and the first radiating element is viewed in a plan view from a direction orthogonal to the first plane. In a region of one radiating element that does not overlap with the second radiating element, a branch portion whose resonance frequency is included in the operating band of the second radiating element is formed.

  Since the film antenna configured as described above has the first resonance frequency and the second resonance frequency, the film antenna has a plurality of resonance frequencies. Further, since the first radiating element of the film antenna is arranged along the first plane and the second radiating element of the film antenna is arranged along at least the second to third planes, the film antenna Compared to a film antenna that is deployed and arranged on the same plane, it can be mounted in a narrow space.

  Furthermore, in the region of the first radiating element that does not overlap with the second radiating element, a branch portion whose resonance frequency is included in the operating band of the second radiating element is formed. Can emit an electromagnetic wave included in the operating band of the second radiating element in addition to the electromagnetic wave having the first resonance frequency. As a result, even when the configuration in which the portion of the second radiating element arranged along the third plane faces the first radiating element is adopted, the radiation characteristic of the second radiating element is deteriorated. Can be suppressed.

  In the film antenna according to one aspect of the present invention, the first radiating element includes a main portion extending in a first direction, which is a direction away from the second plane, and a branch portion branched from the main portion. It is preferable that a branch extending along the first direction is formed.

  According to this configuration, since the branch portion is extended in the first direction, the branch portion can be formed without increasing the length in the direction along the second plane of the first radiating element.

  The film antenna which concerns on 1 aspect of this invention WHEREIN: It is preferable that the said main part is provided with opening.

  By providing the opening in the main part, the path through which the current fed to the first radiating element flows is a path that reaches the end of the first radiating element along the outer peripheral portion of the first radiating element. In addition, there is a path along the contour of the aperture from the near point to the remote point and then to the end of the first radiating element. Therefore, the main part can have a plurality of resonance frequencies.

  The film antenna which concerns on 1 aspect of this invention WHEREIN: The proximity | contact point which is a point which comprises the edge part of the said 2nd plane side of the said opening, and the edge part on the opposite side to the edge part of the said 2nd plane side of the said opening When the contour of the opening is bisected by a remote point that is a constituent point, the contour length of one contour and the contour length of the other contour are preferably different from each other.

  The contour length of one contour in the opening and the contour length of the other contour in the opening are different from each other, so that a path along one contour from the proximity point to the remote point and then to the end of the first radiating element And the path from the proximity point to the remote point along the other contour and then to the end of the first radiating element has different path lengths. Therefore, the resonance frequency of the main part can be further increased.

  In order to solve the above problems, an antenna device according to an aspect of the present invention includes a film antenna according to any one of the aspects described above, a feeder line connected to a feeding region of the film antenna, and the film antenna. A first support surface, a second support surface that intersects the first support surface, and a third surface that faces the first support surface and intersects the second support surface. The film antenna has a support surface, the first plane is in contact with the first support surface, the second plane is in contact with the second support surface with respect to the support, The third flat surface is wound so as to contact the third support surface.

  According to this configuration, it is possible to provide an antenna device that can be mounted in a narrow space while suppressing deterioration of radiation characteristics in an antenna device including a film antenna having a plurality of resonance frequencies.

  In the support provided in the antenna device according to one aspect of the present invention, an interval between the first support surface and the third support surface is 1 / (an effective length of an electromagnetic wave corresponding to the first resonance frequency). 16 or less, and the support further includes a holding unit for holding the power supply line so that a part of the power supply line extends in a direction along the first support surface and the second support surface. And when the first radiating element is viewed in a plan view from a direction orthogonal to the first plane, the length of the first radiating element in the direction along the second plane of the region overlapping with the feeder line Is preferably shorter than the length of the main part in the direction along the second plane.

  By setting the distance between the first support surface and the third support surface to 1/16 or less of the effective length of the electromagnetic wave corresponding to the first resonance frequency, the space in which the antenna device can be mounted can be further reduced. .

  In addition, when the holding portion of the support body holds the feed line so that a part of the feed line extends in a direction along the first support surface and the second support surface, the holding portion is provided outside the antenna device. Compared with, it is possible to improve the tensile strength of the feeder without expanding the space in which the antenna device can be mounted.

  On the other hand, parasitic capacitance is generated between a part of the feeder line extending in the direction along the first support surface and the second support surface and the first radiating element arranged on the first support surface, and as a result. The inventors of the present application have found that the radiation characteristics of the antenna device deteriorate.

  When the first radiating element is viewed in plan from a direction orthogonal to the first plane, the length of the first radiating element in the direction along the second plane of the region overlapping with the feeder line is the second plane of the main part. The parasitic capacitance can be suppressed by making it narrower than the length in the direction along the line. Therefore, this antenna device suppresses deterioration of radiation characteristics even when the distance between the first support surface and the third support surface is 1/16 or less of the effective length of the electromagnetic wave corresponding to the first resonance frequency. can do.

  In the antenna device according to one aspect of the present invention, when the first radiating element is viewed in a plan view from a direction orthogonal to the first plane, the branch portion is connected to the feeder line of the first radiating element. It is preferable that the second region extends from the end of the overlapping region opposite to the second plane side in a direction along the first direction.

  The region of the first radiating element that overlaps the power supply line is close to a part of the power supply line extending in the direction along the first support surface and the second support surface, and thus functions as a virtual power supply region. . By extending the branch portion in the direction along the first direction from the region of the first radiating element that overlaps the feeder line, that is, the end portion on the opposite side to the second plane side of the virtual feeding region, The portion can be made to reliably function as a sub-radiating element having the second resonance frequency. Therefore, it is possible to reliably suppress the deterioration of the radiation characteristics in the vicinity of the second resonance frequency.

  According to the present invention, it is possible to provide a film antenna that can be mounted in a narrow space while suppressing deterioration of radiation characteristics in a film antenna that operates at a plurality of resonance frequencies.

It is a trihedral view of an antenna device according to an embodiment of the present invention. (A) And (b) is an expanded view of the film antenna with which the antenna apparatus shown in FIG. 1 is provided. (A) And (b) is a perspective view of the support body with which the antenna apparatus shown in FIG. 1 is provided. (A) is a perspective view of the vehicle body which mounts the spoiler which incorporates the antenna apparatus shown in FIG. (B) is a perspective view of the spoiler. It is an expanded view of the film antenna with which the Example of this invention is provided. (A) is a graph which shows VSWR of the Example of this invention. (B) is a graph which shows the radiation gain of the Example of this invention. (A) is an expanded view of the film antenna with which the comparative example of this invention is provided. (B) is an expanded view of the film antenna with which the reference example of this invention is equipped.

  The antenna apparatus 1 provided with the film antenna 10 which concerns on one Embodiment of this invention is demonstrated with reference to FIGS. 1-3. FIG. 1 is a three-view diagram of an antenna device 1 according to the present embodiment. 1 is a plan view of the antenna device 1, the upper right diagram in FIG. 1 is a right side view of the antenna device 1, and the lower left diagram in FIG. 1 is a front view of the antenna device 1. FIG. 2A and 2B are development views in which the film antenna 10 is developed on one plane. FIG. 3A is a top perspective view of the support 30 provided in the antenna device 1, and FIG. 3B is a bottom perspective view of the support 30.

  In the coordinate system shown in FIG. 1, the x axis and the y axis are determined so that the first plane on which the first radiating element 12 is arranged is parallel to the xy plane. The x-axis is parallel to the longitudinal direction of the first radiating element 12, and the direction from the front surface to the back surface of the antenna device 1 is defined as the positive x-axis direction. The y-axis is orthogonal to the x-axis, and the direction from the right side surface to the left side surface of the antenna device 1 is the y-axis positive direction. The z-axis is determined to be orthogonal to the xy plane, and the direction from the lower surface to the upper surface of the antenna device 1 is defined as the positive z-axis direction.

[Configuration of Antenna Device 1]
As shown in FIG. 1, the antenna device 1 includes a film antenna 10, a coaxial cable 20, and a support 30. The film antenna 10 is a film antenna according to one embodiment of the present invention. The coaxial cable 20 is an example of a feeder line described in the claims. The film antenna 10 is wound around the support 30 so as to have a predetermined three-dimensional structure described later.

  The coaxial cable 20 includes an inner conductor, an insulating layer, an outer conductor, and a covering layer from the center toward the outer side. The coaxial cable 20 is connected to the feeding area 14 (see FIG. 2) of the film antenna 10. The coaxial cable 20 is held by the support 30 so as to pass through a predetermined wiring path. The configuration of the support 30 will be described later with reference to FIG.

[Film antenna 10]
As shown in FIG. 2, the film antenna 10 is a dipole antenna including a dielectric substrate 11, a radiating element 12, and a radiating element 13. The radiating element 12 is a first radiating element recited in the claims, and the radiating element 13 is a second radiating element recited in the claims. In FIG. 2, the film antenna 10 is developed on the xy plane, and is arranged so that the longitudinal direction of the radiating element 12 is parallel to the x-axis direction. In FIG. 2A, the wiring path of the coaxial cable 20 in the antenna device 1 shown in FIG. 1 is indicated by a virtual line (two-dot chain line).

  Hereinafter, a region where the first radiating element 12 and the second radiating element 13 are close to each other is referred to as a feeding region 14. The coaxial cable 20 is connected to the power feeding region 14. Specifically, the outer conductor of the coaxial cable 20 is soldered to the first connection point 14 a located on the radiating element 12, and the second connection in which the inner conductor of the coaxial cable 20 is located on the radiating element 13. Soldered to the point 14b (see FIG. 2A).

  As shown in FIG. 2A, the coaxial cable 20 is wired so as to cross the radiating element 12 by being pulled out from the feeding region 14 in the negative y-axis direction and then folded back.

  The dielectric substrate 11 is a flexible film-like substrate, for example, made of polyimide resin. Each of the radiating element 12 and the radiating element 13 is a flexible conductive foil formed on one surface of the dielectric substrate 11, and is made of, for example, copper.

  Since the dielectric substrate 11, the radiating element 12, and the radiating element 13 are all flexible, the film antenna 10 has flexibility. Therefore, the film antenna 10 can be bent into various shapes. The film antenna 10 includes a straight line CC (see FIG. 2A) that traverses between the radiating element 12 and the radiating element 13, and a straight line DD that traverses the radiating element 13 (see FIG. 2A). The ridgeline is wound around the support 30 by bending it into a U shape (or J shape) (see FIG. 1).

  In addition, when the film antenna 10 is bent with the straight line CC and the straight line DD as ridgelines, the end side (corresponding to the straight line EE shown in FIG. 2 coincides with the straight line BB shown in (a). Therefore, in the antenna device 1, the section sandwiched between the straight line CC and the straight line BB in the radiating element 12 is disposed to face the section sandwiched between the straight line DD and the straight line EE in the radiating element 13.

  The film antenna 10 may further include a dielectric substrate that covers the surfaces of the radiating elements 12 and 13. That is, the film antenna 10 may have a configuration in which the radiating elements 12 and 13 are sandwiched between two dielectric films. According to this configuration, damage or deterioration of the radiating elements 12 and 13 can be prevented.

(Radiation element 12)
When wound around the support 30, the radiating element 12 as the first radiating element is disposed along the first plane. In FIG. 1, the first plane corresponds to the xy plane on the z-axis negative direction side among the six surfaces surrounding the support 30 of the antenna device 1 from six directions. Hereinafter, the xy plane on the negative side of the z-axis of the antenna device 1 is referred to as the lower surface of the antenna device 1.

  The radiating element 12 has a first resonance frequency. In the present embodiment, the first resonance frequency is 698 MHz, which is the lowest frequency in the LTE (Long Term Evolution) frequency band (from 698 MHz to 2690 MHz). That is, the electrical length of the radiating element 12 is determined so as to correspond to an electromagnetic wave having a frequency of 698 MHz. The electrical length of the radiating element 12 is the length L12 from the second connection point 14b to the tip of the radiating element 12, the relative dielectric constant of the dielectric substrate 11, the conductor pattern of the radiating element 12, and the like. It is a physical quantity determined according to

  Since the first resonance frequency of the radiating element 12 is set to 698 MHz, the radiating element 12 has good radiation characteristics in a frequency band of 698 MHz or more and 960 MHz or less (frequency band on the low frequency side in the LTE frequency band). Can be obtained. Therefore, the radiation element 12 has a frequency band of 698 MHz or more and 960 MHz or less as an operation band.

  The radiating element 12 includes a root portion 12a, a neck portion 12b, and a head portion 12c. In addition, each part of the root part 12a, the neck part 12b, and the head part 12c is arrange | positioned in order toward the edge side on the opposite side to the electric power feeding area | region 14 from the edge side by the side of the electric power feeding area | region 14.

  The root portion 12 a is a region included in the power feeding region 14 of the radiating element 12. Note that the root portion 12a is a U-shaped conductor piece in which a concave portion dug in the negative direction of the x-axis from the straight line CC is formed. This recess surrounds the region included in the power feeding region 14 of the radiating element 13 from three directions.

  The neck portion 12b is a conductor piece disposed between the root portion 12a and the head portion 12c, and has a width (length along the y-axis direction) narrower than the width of the head portion 12c. It is. The neck portion 12b includes a first region 12b1 that is continuous with the root portion 12a and a second region 12b2 that is continuous with the head portion 12c. The width of the neck portion 12b becomes narrower as it approaches the boundary between the first region 12b1 and the second region 12b2 from the root portion 12a, and becomes wider as it approaches the head portion 12c from the boundary. That is, the neck portion 12b is configured to have the smallest width at the boundary.

  The head 12c is a conductor piece that forms the tip of the radiating element 12 (the end opposite to the power feeding region 14). As shown in FIG. 2A, the head 12c is based on a strip conductor whose longitudinal direction is along the x-axis direction, and a gap 12d is formed in the strip conductor.

  The air gap 12d digs the strip-shaped conductor from the middle part of the long side of the strip-shaped conductor on the y-axis positive direction side toward the negative y-axis direction, and further digs the strip-shaped conductor toward the positive x-axis direction. Is formed.

  The head 12c is divided into a main part 12c1 and a branch part 12c2 by a gap 12d. As shown in FIG. 2, the branch portion 12c2 is extended from the boundary between the second region 12b2 and the head portion 12c in the negative x-axis direction along the long side of the strip-shaped conductor on the positive y-axis side. It is a strip conductor.

  The branch part 12c2 is configured such that its resonance frequency is included in an operating band (1400 MHz or more and 2690 MHz) of the radiating element 13 (second radiating element) described later. In the present embodiment, the resonance frequency of the branch portion 12c2 is configured to be 1400 MHz, which is the lower limit frequency of the operating band of the radiating element 13. In other words, the electrical length of the branch portion 12c2 is determined so as to correspond to the electromagnetic wave of 1400 MHz. Note that the electrical length of the branch portion 12c2 is the length L12c2 that is the length from the point P121 to the point P122 shown in FIG. 2B, the relative dielectric constant of the dielectric substrate 11, and the conductor of the branch portion 12c2. It is a physical quantity determined according to the pattern.

  Since the resonance frequency of the branch part 12c2 is set to 1400 MHz, the radiating element 12 including the branch part 12c2 can radiate electromagnetic waves in a frequency band of 1400 MHz to 2000 MHz. Therefore, the radiation element 12 in which the branch portion 12c2 is formed on the head portion 12c can improve radiation characteristics in a frequency band of 1400 MHz to 2000 MHz. Therefore, by forming the branch portion 12c2 in the radiating element 12, the operating band of the radiating element 12 includes a frequency band of 1400 MHz to 2000 MHz in addition to a frequency band of 698 MHz to 960 MHz.

  In addition, as shown to (a) of FIG. 2, the space | gap 12d does not need to reach the edge by the side of the electric power feeding area | region 14 of the head 12c. That is, a widened portion 12c3 that widens the width of the branch portion 12c2 may be formed between the main portion 12c1 and the branch portion 12c2. By forming the widened portion 12c3 at the root of the branch portion 12c2, it is possible to prevent the root width of the branch portion 12c2 from becoming too narrow.

  As described above, the head portion 12c of the radiating element 12 includes the main portion 12c1 extended in the negative x-axis direction, which is the first direction, and the branch portion 12c2 branched from the main portion 12c1, and includes the negative x-axis direction. And a branch portion 12c2 extending along the line. According to this configuration, the branch portion 12c2 can be configured without increasing the width of the radiating element 12 (the length along the y-axis direction).

  Further, as shown in FIG. 2B, the main portion 12c1 is provided with an opening 12e. In the present embodiment, the shape of the opening 12e is a triangle formed by a point P124, a point P125, and a point P126. The point P124 is a point (an adjacent point described in the claims) that constitutes an end of the opening 12e on the x-axis positive direction side. The point P126 is a point that constitutes an end portion of the opening 12e on the x-axis negative direction side (a remote point described in the claims).

  By providing the opening 12e in the main part 12c1, the current from the second connection point 14b to the point P123 can take two paths as a path to the tip of the radiating element 12. The first path is a path from the point P123 to the point P128 along the outer peripheral portion of the radiating element 12 (the long side of the main portion 12c1 on the y-axis negative direction side). The second route is a route from the point P123 to the point P127 via the points P124 and P126 along the outline of the opening 12e.

  Since the path length of the first path is different from the path length of the second path, the main portion 12c1 has at least two resonance frequencies. In other words, the radiating element 12 has a first resonance frequency corresponding to the length L12, a resonance frequency corresponding to the first path, and a resonance frequency corresponding to the second path.

  The opening 12e has a triangular shape as described above. Therefore, when the contour of the opening 12e is bisected by the point P124 and the point P126, the contour length from the point P124 to the point P126 via the point P125 (the contour on the y-axis positive direction side), and from the point P124 to the point P126 The contour lengths of the contours directly extending to (the contour on the negative y-axis side) are different from each other. Specifically, the contour length of the contour on the y-axis positive direction side is longer than the contour length of the contour on the y-axis negative direction side. For this reason, the path length of the second path is different between the case along the contour on the y-axis positive direction side and the case along the contour on the y-axis negative direction side. Therefore, according to this configuration, a plurality of resonance frequencies corresponding to the second path can be provided.

  As described above, the radiating element 12 including the main portion 12c1 has a plurality of resonance frequencies including the first resonance frequency. The radiating element 12 configured as described above can flatten the radiation characteristics in the operating band as compared with the case where the opening 12e is not provided.

(Resonance frequency range of the branch portion 12c2)
In the present embodiment, the case where the resonance frequency of the branch portion 12c2 matches the second resonance frequency of 1400 MHz has been described. However, the resonance frequency of the branch part 12c2 only needs to be included in the operating band of the radiating element 13, and is not limited to the case where it matches the second resonance frequency. The resonance frequency of the branch portion 12c2 can be appropriately determined according to the frequency band in which the radiation characteristics are desired to be improved in the operating band of the radiating element 13.

  For example, in this embodiment, the resonance frequency of the branch portion 12c2 is set to 1400 MHz in order to improve the radiation characteristics in the frequency band of 1400 MHz to 2000 MHz in the operating band of the radiating element 13. However, even when the radiation characteristics in the frequency band of 1400 MHz to 2000 MHz are improved, the resonance frequency of the branch portion 12c2 is not limited to 1400 MHz. For example, the resonance frequency of the branch portion 12c2 only needs to be included in the range of 1400 MHz to 1800 MHz. This range corresponds to 100% to 129% of 1400 MHz.

(Radiation element 13)
When wound around the support 30, the radiating element 13 as the second radiating element is arranged along at least the second plane and the third plane. The second plane is a plane that intersects the first plane (the plane on which the radiating element 12 is disposed). The third plane is a plane that faces the first plane and intersects the second plane. In FIG. 1, the second plane corresponds to the yz plane on the x-axis positive direction side among the six surfaces surrounding the support 30 of the antenna device 1 from six directions. In the following, the yz plane on the x-axis positive direction side of the antenna device 1 is referred to as the back surface of the antenna device 1. In FIG. 1, the third plane corresponds to the xy plane on the z-axis positive direction side among the six surfaces. Hereinafter, the xy plane on the z-axis positive direction side of the antenna device 1 is referred to as the upper surface of the antenna device 1.

  Specifically, the radiating element 13 includes a first region 13a, a second region 13b, and a third region 13c (see FIG. 2A).

  The first region 13 a is a rectangular conductor piece included in the power supply region 14 and constitutes the root portion of the radiating element 13. In the antenna device 1, the film antenna 10 is wound around the support 30 so that the feeding region 14 is disposed along the lower surface (first plane) of the antenna device 1. In this case, the first region 13 a is disposed along the lower surface of the antenna device 1. The inner conductor of the coaxial cable 20 is soldered to the first connection point 14a located on the first region 13a.

  The 2nd field 13b is a conductor piece arranged along the 2nd plane among radiation elements 13, and is a bowl-shaped conductor piece. In FIG. 2A, the second region 13b is a region from the straight line CC to the straight line DD. The second region 13b is obtained by forming a curved portion 13b1 and a curved portion 13b2 by rounding two corners located on the power feeding region 14 side based on a rectangular conductor piece. In the present embodiment, the contours of the curved portions 13b1 and 13b2 are formed so as to coincide with the contour of the ellipse 13b3.

  The 3rd field 13c is a conductor piece arranged along the 3rd plane among radiation elements 13, and is a rectangular conductor piece. In FIG. 2A, the third region 13c is a region from the straight line DD to the straight line EE.

  The radiating element 13 has a second resonance frequency. In the present embodiment, the second resonance frequency is 1400 MHz included in the LTE frequency band. That is, the electrical length of the radiating element 13 is determined so as to correspond to an electromagnetic wave having a frequency of 1400 MHz. The electrical length of the radiating element 13 is the length L13 from the first connection point 14a to the tip of the radiating element 13, the relative permittivity of the dielectric substrate 11, the conductor pattern of the radiating element 13, and the like. It is a physical quantity determined according to

  Since the second resonance frequency of the radiating element 13 is set to 1400 MHz, the radiating element 13 has good radiation characteristics in a frequency band of 1400 MHz to 2690 MHz (frequency band on the high frequency side in the LTE frequency band). Can be obtained. Therefore, the radiating element 13 has a frequency band of 1400 MHz or more and 2690 MHz or less as an operation band.

[Support 30]
As shown in FIG. 3, the support 30 is opposed to the first support surface 31, the second support surface 32 that intersects the first support surface 31 (orthogonal in the present embodiment), and the first support surface 31. The third support surface 33 intersects with the second support surface 32 (orthogonally in the present embodiment). The film antenna 10 is wound around the support 30 such that the surface on which the radiating element 12 and the radiating element 13 are formed is in contact with the first support surface 31, the second support surface 32, and the third support surface 33. It is done.

  In the present embodiment, the box-shaped resin molded product shown in FIG. 3 is used as the support 30, the upper surface thereof is the first support surface 31, and the rear side surface (the side surface on the x-axis positive direction side in the illustrated coordinate system) is the first. The second support surface 32 and its lower surface are referred to as a third support surface 33. Since this resin molded product is thinned from the upper surface side, the upper end surface of the partition wall that remains without being thinned (the hatched portion in FIG. 3A) hatches the first support surface 31. Configure. The third support surface 33 of the support 30 protrudes forward (the negative x-axis direction in the illustrated coordinate system) from the first support surface 31 and is opposed to the region where the first support surface 31 is formed. 33a and a non-opposing region 33b that does not face the region where the first support surface 31 is formed.

  In the film antenna 10, the base portion 12 a and the neck portion 12 b of the radiating element 12 are in contact with the first support surface 31, the second region 13 b of the radiating element 13 is in contact with the second support surface 32, and the third The region 13 c is wound around the support body 30 so as to contact the third support surface 33. Therefore, in the antenna device 1, the root portion 12 a and the neck portion 12 b are opposed to the third region 13 c of the radiating element 13. In other words, when the radiating element 12 is viewed in plan, the root portion 12a and the neck portion 12b are superimposed on the third region 13c. On the other hand, the head 12c of the radiating element 12 is not superimposed on the third region 13c.

  By winding the film antenna 10 around the support 30 in this manner, the antenna device 1 can provide an antenna device that can be mounted in a narrow space while suppressing deterioration in radiation characteristics.

  The support 30 holds the coaxial cable 20 so as to pass through a predetermined wiring path, and as a holding means for enhancing durability against pulling of the coaxial cable 20, a first holding part 34, a second holding part 35, And the 3rd holding | maintenance part 36 is provided.

  The first holding portion 34 as the holding portion described in the claims is provided on the upper surface side (the z-axis positive direction side in the illustrated coordinate system) of the non-facing region 33 b of the third support surface 33. The first holding portion 34 extends a part of the coaxial cable 20 in a direction parallel to both the first support surface 31 and the second support surface 32 (y-axis direction in the illustrated coordinate system). Hold on. Since the first holding part 34 is provided outside the space region sandwiched between the region in contact with the first support surface 31 of the film antenna 10 and the region in contact with the third support surface 33 of the film antenna 10, Even after the film antenna 10 is wound around the support 30, the coaxial cable 20 can be attached to the first holding portion 34.

  In the present embodiment, a plurality of (four in the present embodiment) partition walls 34 a are arranged so that the wall surfaces thereof are perpendicular to both the first support surface 31 and the second support surface 32. Used as The partition wall 34a is formed with a concave portion 34b opened upward, and the coaxial cable 20 can be held as described above by fitting the coaxial cable 20 into the concave portion 34b. Further, in order to make it difficult for the coaxial cable 20 to come out of the holding portion 34, in this embodiment, a partition wall 34c is used in which the wall surface thereof is parallel to the wall surface of the partition wall 34a. The front end face of the partition wall 34c is inclined so as to protrude forward as it goes downward. For this reason, when the coaxial cable 20 is fitted deeply into the recess 34b of the partition wall 34a, the coaxial cable 20 meanders by being pushed forward by the partition wall 34c, and is more strongly pressed against the partition wall 34a. For this reason, the frictional force that the coaxial cable 20 receives from the partition wall 34a increases, and the coaxial cable 20 is difficult to come off.

  The second holding unit 35 is provided on the left side surface of the support 30 (the side surface on the y-axis negative direction side in the illustrated coordinate system). The second holding unit 35 holds a part of the coaxial cable 20 so as to extend in a direction perpendicular to the second support surface 32 (x-axis direction in the illustrated coordinate system). Since the second holding portion 35 is provided outside the space region sandwiched between the region in contact with the first support surface 31 of the film antenna 10 and the region in contact with the third support surface 33 of the film antenna 10, Even after the film antenna 10 is wound around the support 30, the coaxial cable 20 can be attached to the second holding portion 35.

  In the present embodiment, a rectangular parallelepiped protruding portion 35 a protruding leftward from the lower end of the left side surface of the support 30 is used as the second holding portion 35. The protruding portion 35a is formed with a recessed portion 35b that opens from the end surface on the second support surface 32 side to the opposite end surface. By fitting the coaxial cable 20 into the recessed portion 35b, the above-described concave portion 35b is inserted. Such holding of the coaxial cable 20 is realized.

  The third holding portion 36 is provided on the right side surface of the support 30 (the side surface on the negative y-axis side in the illustrated coordinate system). The third holding unit 36 holds a part of the coaxial cable 20 so as to extend in a direction perpendicular to the second support surface 32 (x-axis direction in the illustrated coordinate system). Since the third holding portion 36 is provided outside the space region sandwiched between the region in contact with the first support surface 31 of the film antenna 10 and the region in contact with the third support surface 33 of the film antenna 10, Even after the film antenna 10 is wound around the support 30, the coaxial cable 20 can be attached to the third holding portion 36.

  In the present embodiment, a rectangular parallelepiped protruding portion 36 a protruding rightward from the lower end of the right side wall of the support 30 is used as the third holding portion 36. The projecting portion 36a is formed with a recess 36b that opens from the end surface on the second support surface 32 side to the end surface on the opposite side. By fitting the coaxial cable 20 into the recess 36b, the above-described recess 36b is inserted. Such holding of the coaxial cable 20 is realized.

  Although not shown in FIG. 3, the film antenna 10 is fixed to the support 30 using a fixing means such as a double-sided tape. The fixing means is not limited to the double-sided tape, and may be, for example, a resin adhesive, or formed on each of the first support surface 31, the second support surface 32, and the third support surface 33. For example, it may be an L-shaped protrusion.

(Thickness of the support 30)
By the way, for an antenna device such as the antenna device 1, it is desired to further reduce the space required for mounting (hereinafter referred to as mounting space). This is because if the mounting space can be further reduced, the casing for housing the film antenna can be further reduced, and the degree of freedom in designing the casing can be increased.

  In order to further reduce the mounting space of the antenna device 1, the length of the support body 30 along the x-axis direction (length in the front-rear direction), the y-axis, while suppressing deterioration of radiation characteristics It is required to reduce either the length along the direction (length in the left-right direction) or the length along the z-axis direction (thickness or length in the vertical direction). Among them, there is a strong demand for the antenna device 1 to reduce its thickness.

  The antenna device 1 has the thickness of the support 30, that is, the effective length of the electromagnetic wave corresponding to the first resonance frequency (698 MHz in this embodiment) as the distance between the first support surface 31 and the third support surface 33. Even if it is 1/16 or less (specifically 23 mm or less), the deterioration of radiation characteristics can be suppressed. Specifically, even in such a case, the antenna device 1 can suppress the VSWR in the frequency band of 1400 MHz to 2000 MHz and improve the gain. In the following, the interval between the first support surface 31 and the third support surface 33 is set to 1/16 or less of the effective length of the electromagnetic wave corresponding to the first resonance frequency (698 MHz in the present embodiment). It is called that the thickness of the support 30 is reduced.

  This is because the branch portion 12c2 of the radiating element 12 in addition to the radiating element 13 has the second resonance frequency (1400 MHz in the present embodiment). 1400 MHz is the lower limit frequency of the frequency band (1400 MHz to 2690 MHz) on the high frequency side of the LTE frequency band. By reducing the thickness of the support 30, the radiation characteristics of the radiating element 13 in the frequency band on the high frequency side are lowered, but the branch portion 12c2 can compensate for the degradation of the radiation characteristics.

  Further, in the antenna device 1, when the radiating element 12 is viewed in a plan view, an area overlapping the coaxial cable 20 in the radiating element 12, that is, the width W12b (length along the y-axis direction) of the second area 12 b 2 of the neck 12 b. 2 (see FIG. 2B) is preferably narrower than the width (length along the y-axis direction) of the main portion 12c1 (see FIG. 2A).

  According to this configuration, even if the radiating element 12 and the coaxial cable 20 are close to each other by reducing the thickness (the length along the z-axis direction) of the antenna device 1, the radiating element 12 and the coaxial cable are arranged. The area of the region where 20 and 20 overlap can be reduced. Therefore, the parasitic capacitance generated between the radiating element 12 and the coaxial cable 20 can be suppressed. Therefore, the antenna device 1 can further suppress the deterioration of the radiation characteristics in the frequency band of 1400 MHz or more and 2000 MHz or less even when the thickness of the support 30 is reduced.

  When the first resonance frequency is 698 MHz, the width W12b is preferably 3 mm or more. When the width W12b is set to be less than 3 mm, the current concentrates at the boundary between the first region 12b1 and the second region 12b2. Due to this current concentration, undesirable effects such as a change in the operating band of the antenna device 1 occur.

(Virtual power supply area)
The region overlapping the coaxial cable 20 in the radiating element 12, that is, the second region 12 b 2 is close to a part of the coaxial cable 20 extending in the direction along the first support surface 31 and the second support surface 32. It functions as a virtual power supply area. Accordingly, the branch portion 12c2 is extended in the x-axis negative direction from the end of the second region 12b2 on the x-axis negative direction side (the end of the virtual power supply region, the end connecting the points P121 and P123). Preferably it is. In other words, the length L12C2 (see FIG. 2B) that determines the electrical length of the branch portion 12c2 is the end of the second region 12b2 on the x-axis negative direction side (points P121 and P123). It is preferable that the starting edge) be determined as the starting point.

  According to this configuration, the branch part 12c2 can reliably function as a sub-radiating element having the second resonance frequency. Therefore, it is possible to reliably suppress deterioration of radiation characteristics in a frequency band including the second resonance frequency (frequency band of 1400 MHz to 2000 MHz in the present embodiment).

[Example of mounting on a car body]
Although the object which mounts the antenna apparatus 1 is not limited, For example, it can mount suitably in vehicle bodies, such as a motor vehicle. Here, a mounting example when the antenna device 1 is mounted on a vehicle body will be described with reference to FIG. 4A is a perspective view of a vehicle body 50 on which a spoiler 52 incorporating the antenna device 1 is mounted. FIG. 4B is a perspective view of the spoiler 52.

  As shown in FIG. 4A, a spoiler 52 is mounted on the rear end of the roof 51 of the vehicle body 50. The spoiler 52 is an integrally molded resin member. The spoiler 52 has a structure for determining the position of the spoiler 52 with respect to the rear end of the roof 51 at a predetermined position (not shown in FIG. 4B), and the spoiler 52 is fixed at a predetermined position on the roof 51. A structure (not shown in FIG. 4B) is formed. The spoiler 52 is fixed to a predetermined position of the roof 51 using these structures.

  The spoiler 52 has functions such as suppressing turbulence of the airflow at the rear portion of the vehicle body 50 (rectifying the airflow) and improving the appearance of the vehicle body 50. In order to rectify the airflow, the spoiler 52 is configured so that the size in the vertical direction gradually decreases as it approaches the rear end. That is, the rear part of the spoiler 52 is a wedge shape, and is configured such that a gap is formed inside the wedge shape (a hollow structure is formed) (see FIG. 4B).

  In this mounting example, the spoiler 52 incorporating the antenna device 1 is realized by placing the antenna device 1 in the gap.

  FIG. 5 is a development view of the film antenna 10 provided in the embodiment of the antenna device 1 shown in FIG. The film antenna 10 provided in the antenna device 1 of the present embodiment is the same as the film antenna 10 illustrated in FIG. The unit of each size in FIG. 5 is millimeter (mm).

  The dielectric constant of the dielectric substrate 11 provided in the film antenna 10 is 4.4.

  This film antenna 10 employs 17 mm as the distance between the straight line CC and the straight line DD. Therefore, the thickness of the support 30 provided in the antenna device 1 of the present embodiment is 17 mm.

  In the antenna device 1 of the present embodiment, the first resonance frequency is 698 MHz, and the second resonance frequency is 1400 MHz. In the antenna device 1 of the present embodiment, the effective length of the electromagnetic wave having a frequency of 698 MHz is 368 mm, and 1/16 of the effective length is 23 mm. That is, the thickness of the support 30 in this embodiment is thinner than 1/16 of the effective length.

  FIG. 6A shows the VSWR obtained by the antenna device 1 of this example. FIG. 6B shows the radiation gain obtained by the antenna device 1 of this example. 6A and 6B also show the VSWR and the radiation gain obtained by the comparative example and the reference example of the antenna device 1 shown in FIG.

  A comparative example and a reference example of the antenna device 1 illustrated in FIG. 1 are configured as follows.

(Comparative example)
FIG. 7A is a development view of the film antenna 110 provided in the antenna device as a comparative example. The film antenna 110 included in the antenna device of this comparative example is obtained by changing the radiating element 12 included in the film antenna 10 illustrated in FIG. Each of the dielectric substrate 111 and the radiating element 113 included in the film antenna 110 is configured similarly to the dielectric substrate 11 and the radiating element 13 included in the film antenna 10. The unit of each size in FIG. 7 is millimeter (mm).

  In the film antenna 110, the distance between the straight line CC and the straight line DD is 17 mm. Therefore, the thickness of the support provided in the antenna device as a comparative example is also 17 mm. That is, the thickness of the support in this comparative example is thinner than 1/16 of the effective length.

  The radiating element 112 is a strip-shaped conductor in which a recess surrounding the end of the radiating element 113 is formed. Therefore, neither the branch part nor the neck part is formed in the radiating element 112.

(Reference example)
FIG. 7B is a development view of the film antenna 210 provided in the antenna device as a reference example. The film antenna 210 provided in the antenna device of this comparative example is obtained by changing the distance between the straight line CC and the straight line DD in the film antenna 110 provided in the antenna device which is the reference example to 25 mm. Therefore, the thickness of the support provided in the antenna device as a reference example is also 25 mm. That is, the thickness of the support in this comparative example is thicker than 1/16 of the effective length.

(Measurement environment for radiation characteristics)
In the present embodiment, as described above with reference to FIG. 4, it is assumed that the antenna device 1 is placed in the gap inside the spoiler and then the spoiler is mounted on the vehicle body. Therefore, in this example, the antenna device 1 was mounted on a spoiler, and then the VSWR and the radiation gain were measured in a state where the spoiler was mounted on a simulated vehicle body. The simulated vehicle body imitates a metal member such as a hatch gate included in the vehicle body.

  Note that the VSWR and the radiation gain were measured under the same conditions as those of the antenna device 1 of this example for each of the antenna device of the comparative example and the antenna device of the reference example.

  Further, regarding the antenna device of the reference example, the VSWR and the radiation gain were measured in a state where the antenna device was mounted on a spoiler and mounted on an actual vehicle body. It was confirmed that the antenna device of the reference example exhibited good radiation characteristics when mounted on the actual vehicle body. Specifically, the antenna device of the reference example had a VSWR of less than 2 and a radiation gain of more than −2 dBi in each frequency band of 698 MHz to 960 MHz and 1400 MHz to 2000 MHz.

  Here, when the VSWR and the radiation gain of the antenna device are similar to those of the antenna device of the reference example, it is determined that the VSWR and the radiation gain of the antenna device are good.

(VSWR and radiation gain)
Referring to (a) of FIG. 6, when the antenna device of the reference example and the antenna device of the comparative example are compared, the VSWR of the antenna device of the comparative example is deteriorated in a frequency band of 1400 MHz to 2000 MHz. I understood.

  On the other hand, it was found that the antenna device 1 of this example can suppress the deterioration of the VSWR in the frequency band of 1400 MHz to 2000 MHz. It has been found that the antenna device 1 of the present embodiment exhibits the same level of VSWR as the antenna device 1 of the reference example in the frequency band of 1400 MHz to 2000 MHz.

  Referring to FIG. 6B, when the antenna device of the reference example and the antenna device of the comparative example are compared, the radiation gain of the antenna device of the comparative example is reduced in the frequency band of 1400 MHz to 2000 MHz. I understood that.

  On the other hand, it was found that the antenna device 1 of this example can suppress a decrease in radiation gain in the frequency band of 1400 MHz to 2000 MHz. It has been found that the antenna device 1 of the present example exhibits a radiation gain comparable to that of the antenna device 1 of the reference example in the frequency band of 1400 MHz to 2000 MHz.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Antenna apparatus 10 Film antenna 11 Dielectric board 12 Radiation element (1st radiation element)
12a Root portion 12b Neck portion 12c Head portion 12c1 Main portion 12c2 Branch portion 12c3 Widened portion 12d Air gap 12e Opening 13 Radiation element (second radiation element)
13a 1st area | region 13b 2nd area | region 14 Electric power feeding area | region 14a 1st connection point 14b 2nd connection point 20 Coaxial cable (feed line)
30 Support body 31 1st support surface 32 2nd support surface 33 3rd support surface 34 1st holding part (holding part)
35 2nd holding part 36 3rd holding part

Claims (7)

A first radiating element having a first resonant frequency; and a second radiating element having a second resonant frequency that is higher than the first resonant frequency;
The first radiating element is disposed along a first plane, and the second radiating element includes at least a second plane that intersects the first plane, and faces the first plane and the first plane. Arranged along the third plane intersecting the two planes,
When the first radiating element is viewed in plan from a direction orthogonal to the first plane, a resonance frequency of the first radiating element that does not overlap with the second radiating element is the second frequency. Branches included in the operating band of the radiating element are formed,
A film antenna. The first radiating element includes a main portion extending in a first direction, which is a direction away from the second plane, and a branch portion branched from the main portion, and extends along the first direction. A branch is formed,
The film antenna according to claim 1. The main part is provided with an opening,
The film antenna according to claim 2. The opening is composed of a proximity point that is a point that constitutes an end portion of the opening on the second plane side, and a remote point that is a point that constitutes an end portion on the opposite side of the end portion on the second plane side of the opening. When the contour of is bisected, the contour length of one contour and the contour length of the other contour are different from each other.
The film antenna according to claim 3. A film antenna according to any one of claims 2 to 4, a feed line connected to a feed area of the film antenna, and a support that supports the film antenna,
The support includes a first support surface, a second support surface that intersects the first support surface, and a third support surface that faces the first support surface and intersects the second support surface. ,
In the film antenna, the first plane is in contact with the first support surface, the second plane is in contact with the second support surface, and the third plane is the third support surface with respect to the support. Wrapped around to touch,
An antenna device characterized by that. In the support, an interval between the first support surface and the third support surface is configured to be 1/16 or less of an effective length of an electromagnetic wave corresponding to the first resonance frequency,
The support further includes a holding portion that holds the power supply line such that a part of the power supply line extends in a direction along the first support surface and the second support surface,
When the first radiating element is viewed in plan from a direction orthogonal to the first plane, the length of the first radiating element in the direction along the second plane of the region overlapping the feeder line is Shorter than the length of the main part in the direction along the second plane,
The antenna device according to claim 5. When the first radiating element is viewed in a plan view from a direction orthogonal to the first plane, the branch portion is opposite to the second plane side of a region of the first radiating element that overlaps the feeder line. From the end on the side, it is stretched in the direction along the first direction,
The antenna device according to claim 5 or 6, wherein

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