JP4286875B2 - UWB antenna device - Google Patents

Description

  The present invention relates to a UWB (Ultra Wide Band) antenna apparatus.

Since the frequency band used for UWB communication exceeds GHz, ultra-high speed communication is possible. This UWB was approved for use by the Ministry of Internal Affairs and Communications in August 2006, and is expected to be applied to portable electronic devices and high-precision positioning systems that require ultrahigh-speed communication. An ultra-wideband antenna corresponding to such a frequency band has been developed (see, for example, Patent Document 1).
JP 2005-217897 A

  By the way, an antenna device for UWB communication has a conical or teardrop-shaped antenna portion, and a thin and high-performance antenna device has been desired.

  Therefore, an object of the present invention is to provide a UWB antenna device that is small (particularly thin) and has a low VSWR.

One aspect of the UWB antenna apparatus of the present invention is formed on one surface of the substrate, a flat antenna of the substantially home base type in plan view the left and right symmetrical, the said substrate is formed on one surface, the The antenna unit includes: a power feeding unit connected to an apex portion located on the symmetry axis of the antenna unit; and a flat ground unit formed on the one surface of the substrate and capacitively coupled to the antenna unit. The power feeding portion connected to the projection protrudes in a convex shape in a line symmetry with respect to the symmetry axis from the apex portion located on the symmetry axis of the antenna portion, and the ground portion is in a portion adjacent to the power feeding portion. In order to avoid the convex shape, it has a notch portion that is notched in a concave shape in line symmetry with respect to the symmetry axis, and the length X1 on the symmetry axis of the antenna portion has a wavelength at the lowest usable frequency as λ Then, (λ / 4) × 0.5 ≦ X ≦ (λ / 4) × 0.8, and the length X2 of the ground portion in the direction parallel to the symmetry axis is (λ / 4) × 0.8 ≦ X2 ≦ (λ / 4) meet × 1.2, each said angle and symmetry axis forms a pair of sides which are connected by the vertices Ri der below 70 degrees 50 degrees, the length of the symmetry axis of the substrate 40 mm .

  The antenna unit includes a first side and a second side which are a pair of sides connected at the apex, and a third side which is parallel to the symmetry axis and connected to the first side and the second side. And a fourth base and an antenna part of a substantially home base type in plan view having a fifth side that is orthogonal to the axis of symmetry and is connected to the third side and the fourth side, and the third side and the fourth side The connection portion with the fifth side and the connection portion between the fourth side and the fifth side may be configured by an arc having a radius of curvature of 2 to 4 mm.

  The overlap between the antenna unit and the ground unit in the direction of the symmetry axis may be set to −1.0 to +1.0 mm.

  According to the present invention, it is possible to provide a specific effect that it is possible to provide a small UWB antenna device having a low VSWR value.

  Hereinafter, embodiments to which the UWB antenna device of the present invention is applied will be described.

  FIG. 1 is a diagram showing a configuration of the UWB antenna device of the present embodiment. In this UWB antenna device, as shown in FIG. 1A, an antenna unit 1, a power feeding unit 2, and a ground unit 3 are formed on one surface of a film 4. The film 4 may be a flexible resin film, for example. In this embodiment, a polyimide film having a length of 40 mm, a width of 30 mm, and a thickness of 0.1 mm is used.

  The antenna unit 1 is a planar antenna unit having a substantially home base type in a plan view and functions as a radiating unit. The antenna unit 1 is made of a highly conductive metal such as copper.

  Here, the substantially home base type refers to a shape realized by connecting five sides L1 to L5 to the home base type as shown in FIG. The sides L1 and L2 are sides connected by the vertex P1 on the home base type symmetry axis l. The sides L3 and L4 are sides connected to the sides L1 and L2, respectively, and the side L5 is a side connecting the sides L3 and L4. FIG. 1B shows the home base type antenna unit 1 in which the sides L1 to L5 are connected at the vertices P1 to P5. However, the connecting portion of each side is not necessarily a vertex, P2 to P5 may be rounded and adjacent sides may be connected by a curve.

  As shown in FIG. 1A, the power feeding unit 2 is connected to the apex P1 of the antenna unit 1 (see FIG. 1B). A terminal 2 </ b> A for connecting a coaxial cable is disposed in the power feeding unit 2, and a core wire of the coaxial cable is connected to the power feeding unit 2.

  The ground portion 3 is a flat plate-like conductor having a rectangular shape in plan view and having a cutout portion 3A for avoiding the power feeding portion 2, and is formed of a highly conductive metal such as copper. An external conductor line of a coaxial cable is connected to the ground portion 3 and is maintained at the ground potential.

  The UWB antenna device having such a configuration can be manufactured by attaching a copper foil having the shape of the antenna unit 1, the power feeding unit 2, and the ground unit 3 to one surface of the polyimide film 4.

<Antenna characteristics>
Next, the antenna characteristics of the UWB antenna device of the present embodiment will be specifically described. Here, the dimensions of each part for obtaining the optimum VSWR characteristic (process average value) will be described in particular.

  Table 1 shows the dimensions of each part for optimizing the characteristics of the UWB antenna device. FIG. 2 is a diagram showing a portion changed for optimization on the UWB antenna device. By changing the dimensions of each part as shown in Table 1, the antenna characteristics of the UWB antenna device were optimized.

As shown in FIG. 2, the symbol A indicates the length on the symmetry axis of the antenna unit 1. A symbol B indicates the width of the antenna unit 1. Reference symbol C indicates the length of the ground portion 3. Reference sign D indicates the width of the ground portion 3. A symbol θ represents an angle formed by the side L1 of the antenna unit 1 with the symmetry axis l. A symbol E indicates an overlap in the length direction of the antenna unit 1 and the ground unit 3. In the state shown in the figure, the overlap is -0.5 mm. That is, the antenna unit 1 and the ground unit 3 are separated by 0.5 mm in the length direction. A symbol F indicates a radius of curvature when the vertices P4 and P5 are rounded. In addition, the antenna part which changed the edge | side L1 and L3 and the edge | side L2 and L4 into the continuous curve, respectively was created, and the characteristic comparison with the antenna part of illustration was also performed.

  FIG. 3 is a diagram showing the process average value (dB) of the UWB antenna device obtained by changing the dimensions of each part as shown in Table 1. This process average value is a value derived by obtaining VSWR values when the operating frequencies are 3 GHz, 4 GHz and 5 GHz, respectively, calculating these average values, and further converting the average VSWR values in decibels.

  Since the length of the UWB antenna device is constant at 40 mm, the change in the length C of the ground portion is the same as the change in the length A of the antenna portion 1 and is therefore omitted.

  As shown in FIG. 3, when the length A of the antenna part 1 was the longest (17 mm), the process average value became the highest value. As a result of changing the length A of the antenna unit 1 in accordance with the lowest usable frequency, (λ / 4) × 0.5 ≦ A ≦ (λ / 4) × 0.8 with respect to the wavelength λ of the lowest usable frequency. It was found that the process average value is a good value when the above relationship is satisfied.

  That is, when the minimum frequency used was 3 GHz (λ / 4 = 25 mm), the process average value was a good value when 12.5 mm ≦ A ≦ 20 mm.

  When the width of the antenna portion 1 was the widest (18 mm), the process average value was the highest value.

  Here, although the length of the UWB antenna device is constant at 40 mm, (λ / 4) × 0.8 ≦ C ≦ (λ / 4) × 1.2 with respect to the wavelength λ of the lowest frequency used. It was found that the process average value is a good value when the above relationship is satisfied.

  That is, when the minimum frequency used was 3 GHz (λ / 4 = 25 mm), the process average value was a good value when 20 mm ≦ A ≦ 30 mm.

  When the width D of the ground part 3 was the widest (29 mm), the process average value was the highest value. As a result of changing the width D of the ground portion 3, it was found that the process average value takes a favorable value when 1.5B ≦ D is satisfied with respect to the width B of the antenna portion 1.

  When the angle E between the side L1 of the antenna unit 1 and the axis of symmetry 1 is 63 °, the process average value is the highest value. As a result of changing the angle E by changing the shape of the antenna unit 1, the process average value shows a relatively good value between 40 ° and 80 °, and in particular, the process average value between 50 ° and 70 °. It was found to take a good value.

As a result of adjusting the overlap E in the length direction between the antenna portion 1 and the ground portion 3, a good process average value is obtained when the overlap is between −1.0 to +1.0 mm, and in particular, −0.5 mm. The highest value was obtained in the case of (i.e., no overlap and 0.5 mm apart).

As a result of rounding the corners of the vertices P4 and P5 and adjusting the curvature radius F , a good process average value was obtained when the curvature radius was 2 to 4 mm, and the maximum value was obtained particularly when the curvature radius was 4 mm. . It has been found that the antenna characteristics are improved by the edges of the vertices P4 and P5.

  An antenna unit in which the sides L1 and L3 and the sides L2 and L4 were changed to continuous curves was created, and a characteristic comparison with the UWB antenna device shown in FIG. 2 was also performed. As a result, it has been found that a better process average value can be obtained when the sides L1, L3, L2, and L4 are all constituted by straight lines.

From the above, the length A of the antenna part 1 = 17 mm, the width B of the antenna part 1 = 18 mm, the width D of the ground part 3 = 29 mm, the angle θ = 63 ° between the side L1 of the antenna part 1 and the symmetry axis l, the antenna The overlap E in the length direction of the portion 1 and the ground portion 3 is −0.5 mm, the radii of curvature F of the vertices P4 and P5 are 4 mm, and the sides L1 and L3, and the sides L2 and L4 are configured by straight lines, respectively. It was found that the best process average value was obtained.

  FIG. 4 is a diagram illustrating the VSWR characteristics of the UWB antenna device optimized in the present embodiment. FIG. 5 is a diagram illustrating the directivity characteristics of the UWB antenna device of the UWB antenna device optimized in the present embodiment.

  As shown in FIG. 4, a good value of VSWR characteristics of 2.0 or less was obtained at frequencies between 3.1 and 5 GHz. Further, assuming that the direction perpendicular to the film surface of the UWB antenna device is the X axis, the direction perpendicular to the symmetry axis of the antenna portion in the film surface is the Y axis, and the direction of the symmetry axis is the Z axis, as shown in FIG. Uniform directional characteristics were obtained in the (a) XY direction and (b) YZ direction.

  As described above, according to the present embodiment, it is possible to provide a thin UWB antenna apparatus having a low VSWR value.

  In the above description, the antenna unit 1 and the ground unit 3 are described as being disposed on the same surface of the film 4. For example, as shown in FIG. May be disposed on the opposite surface (the back side of the paper surface in FIG. 6). In this case, the power feeding unit 2 may be connected using a microstrip line. When a microstrip line is used, as shown in the figure, a terminal 2A may be disposed at a connection part (an end part of the film 4 in the figure) between the microstrip line and the ground part 3. In addition, when the width of the microstrip line was changed and the process average value was obtained, the maximum value was obtained when the width was 1.45 mm among 0.95 mm, 1.45 mm, and 1.95 mm.

  Moreover, although the form which uses the flexible film 4 was demonstrated above, instead of the film 4, you may use a board | substrate like a glass base material epoxy resin laminated board (FR4).

  The antenna device according to the exemplary embodiment of the present invention has been described above, but the present invention is not limited to the specifically disclosed embodiment, and does not depart from the scope of the claims. Various modifications and changes are possible.

  The UWB antenna device of the present invention can be used for an antenna for a portable electronic device capable of ultra-high speed communication, a high-precision positioning system, and the like.

It is a figure which shows the UWB antenna apparatus of embodiment. It is a figure which shows the location changed for the optimization in the UWB antenna apparatus of embodiment. It is a figure which shows the process average value of the UWB antenna apparatus obtained by changing the dimension of each part in the UWB antenna apparatus of embodiment. It is a figure which shows the VSWR characteristic of the UWB antenna apparatus optimized in embodiment. It is a figure which shows the directivity of the UWB antenna apparatus optimized in embodiment. It is a figure which shows the UWB antenna apparatus by the modification of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Antenna part 2 ... Feed part 2A ... Terminal 3 ... Ground part 3A ... Notch part 4 ... Film

Claims (3)

Formed on one surface of the substrate, symmetrical in plan view with left and right line symmetry and a substantially home base type flat antenna portion;
A power feeding portion formed on the one surface of the substrate and connected to a vertex portion located on the symmetry axis of the antenna portion;
A flat ground portion formed on the one surface of the substrate and capacitively coupled to the antenna portion;
The power feeding part connected to the antenna part protrudes in a convex shape in line symmetry with respect to the symmetry axis from the apex part located on the symmetry axis of the antenna part, and the ground part is close to the power feeding part In order to avoid the convex shape in the portion to have a notch portion that is notched in a concave shape in line symmetry with respect to the symmetry axis,
The length X1 on the axis of symmetry of the antenna section satisfies (λ / 4) × 0.5 ≦ X1 ≦ (λ / 4) × 0.8, where λ is the wavelength at the lowest usable frequency,
A length X2 of the ground portion in a direction parallel to the symmetry axis satisfies (λ / 4) × 0.8 ≦ X2 ≦ (λ / 4) × 1.2 with respect to λ.
Each an angle and forms the axis of symmetry of the pair of sides which are connected by the vertices Ri der below 70 degrees 50 degrees,
The UWB antenna device , wherein a length of the substrate in the direction of the symmetry axis is 40 mm . The antenna unit is
A first side and a second side which are a pair of sides connected at the vertex;
A third side and a fourth side parallel to the symmetry axis and connected to the first side and the second side;
A substantially home-base type antenna unit in plan view having a fifth side orthogonal to the axis of symmetry and connected to the third side and the fourth side;
2. The UWB according to claim 1, wherein a connection portion between the third side and the fifth side and a connection portion between the fourth side and the fifth side are configured by arcs having a curvature radius of 2 to 4 mm. Antenna device.   The UWB antenna device according to claim 1, wherein an overlap between the antenna unit and the ground unit in the direction of the symmetry axis is −1.0 to +1.0 mm.

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