JP2005136573A - Planar antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar antenna suitable for circular polarized wave communication. <P>SOLUTION: The planar antenna is provided with a loop-like antenna filament 3, a first capacitive coupling filament 1 connected to the antenna filament 3 and extending to the inside of the antenna filament 3 which are provided on a dielectric substrate, and a second capacitive coupling filament 2 connected to the antenna filament 3 and extending to the inside of the antenna filament 3. In this antenna, a first opening end 1a and a second opening end 2a are capacitively coupled so as to be close, and the first and second opening ends 1a and 2a forms a closest part in that the first and second capacitive coupling filaments 1 and 2 are close to each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a planar antenna, and more particularly to a planar antenna suitable for a vehicle glass antenna used for circularly polarized radio wave communication with a frequency of about 1 to 30 GHz.

  2. Description of the Related Art In recent years, GPS (satellite positioning system: Global Positioning System) and ETC (automatic toll collection system: Electric Toll Collection System) is used.

For example, a vehicle window glass antenna for UHF shown in FIG. 5 may be applied as an antenna of an in-vehicle communication device used in these systems (see, for example, Patent Document 1). In this conventional example, two capacitive coupling wires 14 are provided on a loop-shaped antenna wire 13.
Connect the, thereby improving the antenna gain by the capacitive coupling by the parallel proximity part of the capacitive coupling umbilical 14 of length L _13. However, this conventional example is an antenna for linearly polarized waves, and when used for circularly polarized waves with a frequency of GHz, there is a problem that the axial ratio and the antenna gain are poor. For this reason, there has been a demand for a circularly polarized flat antenna that is more excellent in axial ratio and antenna gain than in the past.

JP-A-9-93019

  An object of the present invention is to provide a planar antenna that eliminates the above-mentioned drawbacks of the prior art.

The present invention provides a loop-shaped antenna wire on a dielectric substrate, a first capacitive coupling wire connected to the antenna wire and extending inside the antenna wire, and connected to the antenna wire. In the planar antenna provided with the second capacitive coupling wire extending inside the antenna wire,
The open end of the first capacitive coupling line and the open end of the second capacitive coupling line are capacitively coupled in proximity,
In the proximity of the first capacitive coupling filament and the second capacitive coupling filament, the open end of the first capacitive coupling filament and the open end of the second capacitive coupling filament are recently Provided is a planar antenna characterized by being a tangent portion.

Further, a loop-shaped antenna wire on the dielectric substrate, a first capacitive coupling wire connected to the antenna wire and extending inside the antenna wire, and the antenna wire connected to the antenna wire A planar antenna for circular polarization provided with a second capacitive coupling wire extending inside the strip,
Provided is a circularly polarized wave planar antenna characterized in that a first capacitive coupling wire and a second capacitive coupling wire are capacitively coupled in proximity to each other.

  In the present invention, the open end of the first capacitive coupling wire and the open end of the second capacitive coupling wire connected to the loop-shaped antenna wire are capacitively coupled close to each other. In addition, it has excellent circular polarization characteristics.

  Hereinafter, a planar antenna of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings. FIG. 1 is a plan view of an embodiment of the planar antenna according to the present invention, and is a plan view of one side of a dielectric substrate (not shown) provided with antenna wires.

In FIG. 1, 1 is a first capacitive coupling wire, 1a is a first open end which is an open end of the first capacitive coupling wire 1, and 1b is an antenna wire 3 and a first capacitive coupling wire. 1st connection location which is a connection location with the wire 1, 2 is the 2nd line for capacitive coupling, 2a is the 2nd open end which is the open end of the 2nd capacitive coupling wire 2, 2b is A second connection point that is a connection point between the antenna wire 3 and the second capacitive coupling wire 2, 3 is an antenna wire, 4 is a feeding portion, and 5 is a center of gravity of a figure formed by the antenna wire 3. linear (one-dot chain line) passing through, alpha first interior angle, beta second interior angle, g is distance between the first open end 1a and a second open end 2a, L _a is the center of the feeding section 4 The distance between the straight line 5, L _b is the distance between the first capacitive coupling line 1 and the straight line 5, or the distance between the second capacitive coupling line 2 and the straight line 5, and L _c is the antenna line 3. Figure to do Base and the distance between the second interior angle beta, the distance L _x is antenna wire 3 is the length of the base of figures constituting, L _y from bottom of figures antenna wire 3 constitutes up to opposite sides of the bottom side of the It is.

  In the example shown in FIG. 1, the figure formed by the antenna wire 3 is a hexagon or a substantially hexagon, and the bottom side of this figure and the opposite side of the bottom side are parallel or substantially parallel, The angles of the two interior angles β other than the two interior angles that are in contact with the opposite side of the base are 180 degrees or more. The inner angle β is preferably 240 degrees or more.

  FIG. 2 is an embodiment different from the example shown in FIG. 1 and shows an embodiment in which the figure formed by the antenna wire 3 is a rectangle or a substantially rectangle. FIG. 3 shows an embodiment different from the example shown in FIG. 1, in which the figure formed by the antenna wire 3 is a hexagon or a substantially hexagon. In the example shown in FIG. The base and the opposite side of the base are parallel or substantially parallel, and the angles of the two internal angles other than the two internal angles in contact with the base and the two internal angles in contact with the opposite side of the base are 180 degrees or less. FIG. 4 is an embodiment different from the example shown in FIG. 1 and shows an embodiment in which the figure formed by the antenna wire 3 is elliptical or substantially elliptical.

  In the present invention, a loop-shaped antenna wire 3 is connected to a dielectric substrate, and is connected to the first capacitive coupling wire 1 and the antenna wire 3 that are connected to the antenna wire 3 and extended to the inside of the antenna wire 3. The second capacitive coupling wire 2 extending inside the antenna wire 3 is provided. Furthermore, the first open end 1a and the second open end 2a are capacitively coupled in proximity, and the first capacitive coupling line 1 and the second capacitive coupling line 2 are in proximity. The first open end 1a and the second open end 2a are the closest portions.

In the present invention, in order to improve the axial ratio, the range of g / lambda _g is preferably 0.034 or less. A more preferable range g / lambda _g is 0.024 or less, particularly preferably g / lambda _g range is 0.016 or less. Further, in consideration of prevention of short circuit of the gap g due to migration and easy manufacturing, the gap g is preferably 0.1 mm or more. Note that λ _g is the wavelength of the radio wave in the glass, and λ _g = λ ₀ · k. However, λ ₀ is the wavelength of radio waves in the air, k is the glass wavelength shortening rate, and k = 0.60.

  In the example shown in FIGS. 1, 2, 3, and 4, the first open end 1a is temporarily extended, and when the second open end 2a is extended, both extended portions collide with each other. This is preferable in terms of improving the axial ratio. However, the present invention is not limited to this, and the first open end 1a and the second open end 2a are capacitively coupled in close proximity even if the extended portions of both do not collide and collide with each other. If the wire 1 and the second capacitive coupling wire 2 are close to each other, the first open end 1a and the second open end 2a can be used if they are closest to each other.

  In the example shown in FIGS. 1, 2, 3, and 4, the figures are line symmetric or substantially line symmetric with respect to the straight line 5. Further, the first connection point 1b and the second connection point 2b are provided on the same side with the straight line 5 as a boundary, and the first connection point 1b and the second connection point 2b are separated from the straight line 5 and Is provided. The antenna wire 3 is provided with a power feeding part 4 or a power feeding line connected to the power feeding part 4, and the power feeding part 4 or the power feeding line is connected to the first connecting part and the second connecting part with a straight line 5 as a boundary. It is provided on the opposite side. By adopting such a configuration, the axial ratio is improved.

  In the example shown in FIGS. 1, 2, 3, and 4, a part of the antenna wire 3 is interrupted, and the power feeding unit 4 is provided in the interrupted part. However, the present invention is not limited to this, and a feeder line may be connected to the interrupted portion. In addition, the antenna wire 3 may be fed by electromagnetic coupling using a part of the antenna wire 3 without providing a break portion. The example shown in FIG. 3 illustrates that a part of the antenna wire 3 is cut off and both sides of the cut off portion are connected to the feed line 8.

  In the present invention, the antenna wire 3 once extended from the first connection location 1b is bent or bent, and is extended toward the first open end 1a and the second open end 2a. In this extended portion, it is preferable that the first open end 1a and the second open end 2a are close to each other and capacitively coupled.

  In the example shown in FIG. 1, the central corner of the three corners close to the first connection location 1b and the second connection location 2b is close to the first open end 1a and the second open end 2a. Capacitive coupling is used, and such a configuration is preferable in terms of improving the axial ratio.

  The antenna wire 3, the first capacitive coupling wire 1, and the second capacitive coupling wire 2 are produced by forming a conductive pattern on a dielectric substrate such as a circuit board. When the planar antenna of the present invention is a glass antenna for a vehicle, the antenna wire 3, the first capacitive coupling wire 1, and the second capacitive coupling wire 2, for example, usually a silver paste A paste containing a conductive metal such as is printed on the inner surface of the window glass plate and baked. However, the present invention is not limited to this method, and a linear or foil-like body made of a conductive material such as copper may be formed on the vehicle inner surface or the vehicle outer surface of the window glass plate 3. It may be provided inside itself.

  The present invention will be described below with reference to examples, but the present invention is not limited to these examples, and various improvements and modifications are also included in the present invention as long as the gist of the present invention is not impaired. Hereinafter, embodiments will be described in detail with reference to the drawings.

  Assuming that a planar antenna as shown in FIG. 1 is formed on the inner surface of a window glass plate of an automobile, the characteristics shown in the following characteristic diagrams were calculated by the moment method. The operating frequency is 2.22 GHz, and FIGS. 8 and 10 are calculated based on the operating frequency. The dimensions and constants of each part are as follows. The frequency-reflection loss (dB) is shown in FIG.

L _a 0.074 · λ _g mm,
L _b 0.074 · λ _g mm,
L _c 0.081 · λ _g mm,
L _x 0.356 · λ _g mm,
L _y 0.163 · λ _g mm,
λ _g 81.02 mm,
α 45deg,
β 270 deg.

  FIG. 7 is a schematic diagram when the antenna wire 3, the first capacitive coupling wire 1, and the second capacitive coupling wire 2 are provided on the x, z coordinate plane in the x, y, z coordinate plane. It is. In FIG. 7, the center of gravity of the hexagon formed by the antenna wire 3 coincides with the intersection of the x-axis, y-axis, and z-axis, and the base of this hexagon is parallel to the x-axis. The angle φ is an angle formed by the radial direction and the x axis. The characteristics of the angle φ and the axial ratio (dB) are shown in FIG.

The Figure 9 shows the characteristics of the g / lambda _g and the axial ratio (dB). In FIG. 9, k = 0.60. In the case where the variable L _a at the operating frequency in Figure 10, showing characteristics of the L _a and the axial ratio (dB).

  It is used for communications such as ETC and SDARS (Satellite Digital Audio Radio System, around 2.6 GHz) or the like.

1 is a plan view of an embodiment of a planar antenna according to the present invention, and is a plan view of one side of a dielectric substrate provided with antenna wires 3; The top view of the Example which is an Example different from the example shown in FIG. 1, Comprising: The figure which the antenna filament 3 comprises is a rectangle or a substantially rectangular shape. The top view of the Example which is an Example different from the example shown in FIG. 1, Comprising: The figure which the antenna wire 3 comprises is a hexagon or a substantially hexagon. The top view of the Example which is an Example different from the example shown in FIG. 1, Comprising: The figure which the antenna wire 3 comprises is an ellipse or a substantially ellipse. The top view of the conventional window glass antenna for vehicles. The frequency-reflection loss characteristic figure of an Example. FIG. 5 is a schematic diagram when an antenna wire 3, a first capacitive coupling wire 1, and a second capacitive coupling wire 2 are provided on the x, z coordinate plane in the x, y, z coordinate plane. The characteristic figure of angle (phi) and an axial ratio. characteristic diagram of the _g / λ g and axial ratio. In the case of the _{L a} at the operating frequency and variable characteristic diagram of the _{L a} and the axial ratio (dB).

Explanation of symbols

1: 1st capacitive coupling wire 1a: 1st open end 1b: 1st connection location which is a connection location of the antenna wire and 1st capacitive coupling wire 2: 2: 2nd capacitive coupling Line 2a: Second open end 2b: Connection point between antenna line 3 and second capacitive coupling line 2 Second connection point 3: Antenna line 4: Feeding part 5: With a one-dot chain line A straight line passing through the center of gravity of the figure formed by the antenna wire 3

Claims (11)

A loop-shaped antenna wire on the dielectric substrate, a first capacitive coupling wire connected to the antenna wire and extending inside the antenna wire, and the antenna wire connected to the antenna wire In the planar antenna provided with the second capacitive coupling wire extending inward,
The open end of the first capacitive coupling line and the open end of the second capacitive coupling line are capacitively coupled in proximity,
In the proximity of the first capacitive coupling filament and the second capacitive coupling filament, the open end of the first capacitive coupling filament and the open end of the second capacitive coupling filament are recently A planar antenna characterized by being a contact portion. A loop-shaped antenna wire on the dielectric substrate, a first capacitive coupling wire connected to the antenna wire and extending inside the antenna wire, and the antenna wire connected to the antenna wire A planar antenna for circular polarization provided with a second capacitive coupling wire extending inward;
A planar antenna for circular polarization, wherein the first capacitive coupling filament and the second capacitive coupling filament are capacitively coupled in close proximity.   The extension part of both collides and connects, when the open end of the 1st capacitive coupling wire is extended and the open end of the 2nd capacitive coupling wire is extended temporarily. Flat antenna. When the figures are line-symmetric or substantially line-symmetric with respect to a straight line passing through the center of gravity of the figure formed by the antenna line,
A connection point between the antenna line and the first capacitive coupling line is referred to as a first connection point.
When the connection point between the antenna wire and the second capacitive coupling wire is referred to as a second connection point,
The first connection point and the second connection point are provided on the same side with the straight line as a boundary,
The planar antenna according to any one of claims 1 to 3, wherein a first connection point and a second connection point are provided apart from the straight line.   The antenna wire is provided with a power feeding unit, or a power feeding line is connected to the antenna wire, and the power feeding unit or the power feeding line is connected to the first connection point and the second line with the straight line as a boundary. The planar antenna according to claim 4, which is provided on the side opposite to the connection location.   The planar antenna according to claim 5, wherein a part of the antenna line is interrupted, and the power supply unit is provided in the interrupted part, or the power supply line is connected to the interrupted part. . The figure is a hexagon or a substantially hexagon, and the base of the figure and the opposite side of the base are parallel or substantially parallel;
The planar antenna according to any one of claims 4 to 6, wherein two internal angles other than the two internal angles in contact with the base and the two internal angles in contact with the opposite side of the base are 180 degrees or more.   The antenna wire once extended from the first connection portion is bent or bent, and the open end of the first capacitive coupling wire and the open end of the second capacitive coupling wire 5. In this extended part, the open end of the first capacitive coupling line and the open end of the second capacitive coupling line are adjacent to each other and capacitively coupled. The planar antenna in any one of -7.   Of the three corners close to the first connection location and the second connection location, the central corner is the open end of the first capacitive coupling line and the second capacitive coupling line. The planar antenna according to claim 7, wherein the planar antenna is capacitively coupled close to the end.   The planar antenna according to any one of claims 4 to 9, wherein the straight line and the first capacitive coupling line are parallel or substantially parallel. The planar antenna according to any one of claims 4 to 10, wherein the straight line and the second capacitive coupling line 2 are parallel or substantially parallel.

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