JP2005079972A - Flat antenna system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat antenna system of an ultrathin type advantageous to miniaturization. <P>SOLUTION: The flat antenna system 10 is roughly configured by placing an H-shaped inner conductor 12 with a pair of recessed parts 12b and a ground conductor 13 having a pair of projections 13b projected into the recessed parts 12b and enclosing the inner conductor 12 onto a board 11 to connect a point in the vicinity of an outer circumferential edge 12a of the inner conductor 12 to a feeding circuit and to connect a point in the vicinity of an inner circumferential edge 13a of the ground conductor 13 to an earth circuit. A frame-shaped slot 14 is demarcated between the outer circumferential edge 12a of the inner conductor 12 and the inner circumferential edge 13a of the ground conductor 13, and selecting the length of a semicircle of the slot 14 to about a half the resonance electric length allows the planar antenna system 10 to act like a slot antenna. Since the length of the outer circumferential edge 12a of the inner conductor 12 is increased by the recessed parts 12b, the slot antenna as above can easily secure a required resonance electric length. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a very thin planar antenna device that operates as a slot antenna.

  As an ultra-thin planar antenna device that can be mounted on a glass window of an automobile, the inner conductor made of conductive metal foil or conductive film is surrounded by a ground conductor such as a vehicle body through a frame-shaped slot. Conventionally, a configuration in which power is supplied to the vicinity of the outer peripheral edge of the inner conductor to operate as a slot antenna is known (for example, see Patent Document 1).

  FIG. 4 is a plan view for explaining the basic configuration of this type of conventional planar antenna apparatus. In the planar antenna device 1 shown in the figure, a rectangular inner conductor 3 and a ground conductor 4 surrounding the inner conductor 3 are disposed on a substrate 2 made of glass or the like. Between the outer peripheral edge 3a and the inner peripheral edge 4a of the ground conductor 4, a frame-like slot 5 having a constant width dimension is defined. The vicinity of the outer peripheral edge 3a of the inner conductor 3 is connected to a power supply circuit (not shown), and the vicinity of the inner peripheral edge 4a of the ground conductor 4 is connected to a ground circuit (not shown).

In the planar antenna device 1 schematically configured as described above, since the outer peripheral edge 3a of the inner conductor 3 and the inner peripheral edge 4a of the ground conductor 4 are opposed to each other via the slot 5, an electric field crossing the slot 5 is generated during power feeding. If the length of the half circumference of the slot 5 is set to about one half of the resonance electric length λ _0, a standing wave of the electric field can be generated. Therefore, the planar antenna device 1 can be operated as a high gain slot antenna with little transmission loss.
JP 2002-290145 A (2nd page, FIG. 1)

As described above, in the conventional planar antenna device 1 shown in FIG. 4, it is necessary to set the length of the half circumference of the slot 5 to about one half of the resonance electrical length λ _0. radio waves except when particularly high frequency, since the length of lambda _0/2 are never short, the inner conductor 3 in order to secure the length of the outer peripheral edge 3a must be somewhat larger. Therefore, the conventional planar antenna device 1 is likely to be a relatively large antenna, and there is a problem that it is difficult to reduce the size that is highly demanded in vehicles.

  The present invention has been made in view of such a state of the art, and an object of the present invention is to provide an ultra-thin planar antenna device advantageous for miniaturization.

  In order to achieve the above-described object, in the planar antenna device of the present invention, an inner conductor formed in an outer shape having a concave portion and a convex portion projecting into the concave portion on the same plane, the inner conductor having the convex portion protruding into the concave portion. By arranging the surrounding ground conductor, the outer peripheral edge of the inner conductor and the inner peripheral edge of the ground conductor are opposed to each other through a frame-shaped slot, and the vicinity of the outer peripheral edge of the inner conductor is provided as a power feeding circuit. In addition to being connected to the ground conductor, the vicinity of the inner peripheral edge of the ground conductor is connected to a ground circuit to operate as a slot antenna.

  The planar antenna device thus configured operates as a slot antenna in which a frame-like slot having irregularities is interposed between the outer peripheral edge of the inner conductor and the inner peripheral edge of the ground conductor. In such a slot antenna, since the length of the outer peripheral edge of the inner conductor is increased by the recess, the path of the current flowing along the outer peripheral edge at the time of feeding is extended, and the resonance electric length is increased correspondingly. Therefore, even if the size of the inner conductor is reduced, it becomes easy to secure the necessary resonance electric length, and the miniaturization of the planar antenna device is facilitated.

  In the planar antenna device having such a configuration, it is preferable that an inner conductor has a plurality of the concave portions and a ground conductor has a plurality of the convex portions, thereby further increasing the resonance electric length, thereby facilitating further miniaturization. Become.

  In the planar antenna device having such a configuration, the inner conductor is connected to the feeder circuit on a substantially bisector passing through the concave portion, and the ground conductor is connected to the ground circuit at a position facing the feeder point via the slot. It is preferable to connect them, and this can efficiently resonate during power feeding, so that the gain is improved.

  In the planar antenna device having such a configuration, it is preferable that the outer conductor has a line-symmetric or point-symmetric outer shape. In other words, when the radio wave used is linearly polarized, the design is facilitated by making the inner conductor a line-symmetric outer shape with a concave portion. When the radio wave used is circularly polarized, the inner conductor is The design is facilitated by having a point-symmetric outer shape.

  In the planar antenna device of the present invention, the length of the outer peripheral edge of the inner conductor is increased by the recess, and the path of the current flowing along the outer peripheral edge during power feeding is extended, so the size of the inner conductor is reduced. However, it is easy to ensure the necessary resonance electric length, and therefore, an ultra-thin planar antenna device advantageous for miniaturization can be provided.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a planar antenna device according to a first embodiment of the present invention. In the planar antenna device 10 shown in the figure, on a flat substrate 11 made of glass or the like, an H-shaped inner conductor 12 having a pair of recesses 12b and a pair of projections protruding into the recesses 12b. A ground conductor 13 having a portion 13b and surrounding the inner conductor 12 is disposed. Both the conductors 12 and 13 are made of conductive metal foil or the like, the vicinity of the outer peripheral edge 12a of the inner conductor 12 is connected to a power supply circuit (not shown), and the vicinity of the inner peripheral edge 13a of the ground conductor 13 is connected to an earth circuit (not shown). Has been. A frame-like slot 14 having a constant width dimension is defined between the outer peripheral edge 12 a of the inner conductor 12 and the inner peripheral edge 13 a of the ground conductor 13. That is, the outer peripheral edge 12 a of the inner conductor 12 and the inner peripheral edge 13 a of the ground conductor 13 are opposed to each other via the slot 14 that is bent in a crank shape and surrounds the H-shaped inner conductor 12. The inner conductor 12 is connected to the power feeding circuit in the vicinity of the bottom of the one recess 12b, and the ground conductor 13 is connected to the ground circuit in the vicinity of the top of the one protrusion 13b protruding into the recess 12b.

In the planar antenna device 10 configured as described above, since an electric field is generated across the slot 14 during feeding, the length of the half circumference of the slot 14 is set to about one half of the resonance electrical length λ _0. Can generate a standing wave of an electric field, and can thus be operated as a slot antenna. In such a slot antenna, the inner conductor 12 and the slot 14 are formed in a line-symmetric outer shape, and the feeding point is located in the vicinity of the symmetry axis, so that linearly polarized waves can be transmitted and received. Moreover, since the shape is simple, the design is easy. Further, in such a slot antenna, the length of the outer peripheral edge 12a of the inner conductor 12 is increased by the pair of recesses 12b, so that the path of the current flowing along the outer peripheral edge 12a during power feeding extends, and the resonance electric power is correspondingly increased. The length is getting longer. Accordingly, the planar antenna device 10 is not only ultra-thin and can be manufactured at low cost, but it is easy to ensure the necessary resonance electrical length even when the size of the inner conductor 12 is reduced, and thus downsizing is promoted. It is easy to do.

  The planar antenna device 10 is connected to the feeder circuit on a substantially bisector where the inner conductor 12 passes through the pair of recesses 12b, and is grounded at a position facing the feeder point via the slot 14. Since the conductor 13 is connected to the ground circuit, it can resonate efficiently during power feeding. Therefore, the planar antenna device 10 can be operated as a high gain slot antenna with little transmission loss.

  FIG. 2 is a plan view of a planar antenna device according to the second embodiment of the present invention, and the same reference numerals are given to portions corresponding to those in FIG. In the planar antenna device 20 shown in FIG. 2, the inner conductor 12 is formed in a substantially circular shape having recesses 12b at four equally spaced locations, and the four protrusions 13b of the ground conductor 13 protrude into the recesses 12b. In addition, a frame-shaped slot 14 having a constant width dimension is defined between the outer peripheral edge 12 a of the inner conductor 12 and the inner peripheral edge 13 a of the ground conductor 13. In the case of the planar antenna device 20, the outer shape of the inner conductor 12 is substantially circular. However, since the number of the concave portions 12b is large, the length of the outer peripheral edge 12a is relatively long, and therefore it is necessary even if the size is reduced. It is easy to ensure the resonant electrical length. The planar antenna device 20 can also transmit and receive linearly polarized waves.

  FIG. 3 is a plan view of a planar antenna device according to a third embodiment of the present invention, and portions corresponding to those in FIG. In the planar antenna device 30 shown in FIG. 3, since the degenerate separation elements 12c are provided at two locations of the inner conductor 12 formed in a substantially H shape having the recess 12b, it is possible to transmit and receive circularly polarized waves. is there. In addition, since the degenerate separation element 12c having an obliquely cut shape is attached, the planar antenna device 30 includes the shape of the ground conductor 13 having the convex portion 13b and the outer peripheral edge 12a of the inner conductor 12 and the ground. The shape of the frame-shaped slot 14 defined between the inner periphery 13 a of the conductor 13 is also slightly different from that of the planar antenna device 10. In this embodiment, the degenerate separation element is formed by a notch, but the degenerate separation element may be formed by a protrusion.

1 is a plan view of a planar antenna device according to a first embodiment of the present invention. It is a top view of the planar antenna device concerning the example of a 2nd embodiment of the present invention. It is a top view of the planar antenna device concerning the example of a 3rd embodiment of the present invention. It is a top view of the planar antenna apparatus which concerns on a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 20, 30 Planar antenna apparatus 11 Board | substrate 12 Inner conductor 12a Outer peripheral edge 12b Recessed part 12c Degeneration separation element 13 Ground conductor 13a Inner peripheral edge 13b Convex part 14 Slot

Claims (4)

  By arranging an inner conductor formed in an outer shape having a concave portion on the same plane and a ground conductor having a convex portion protruding into the concave portion and surrounding the inner conductor, the inner conductor of the inner conductor is arranged. The outer peripheral edge and the inner peripheral edge of the ground conductor are opposed to each other via a frame-shaped slot, and the vicinity of the outer peripheral edge of the inner conductor is connected to a power feeding circuit and the vicinity of the inner peripheral edge of the ground conductor is connected to a ground circuit. By doing so, the planar antenna device is made to operate as a slot antenna.   2. The planar antenna device according to claim 1, wherein the inner conductor has a plurality of the concave portions, and the ground conductor has a plurality of the convex portions.   3. The ground conductor according to claim 1, wherein the inner conductor is connected to the feeder circuit on a substantially bisector passing through the concave portion, and the ground conductor is disposed at a position facing the feeder point via the slot. A planar antenna device, wherein the planar antenna device is connected to the ground circuit. 4. The planar antenna device according to claim 1, wherein an outer shape of the inner conductor is a line-symmetrical or point-symmetrical shape.

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