JP2005277501A - Uwb antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of a conventional UWB antenna that, since an antenna shape is complicated, mass production and use as a high performance small antenna in nonmilitary application such as a household electric appliance are difficult. <P>SOLUTION: An antenna assembly comprises a pair of antenna elements wherein the antenna element is composed of a pointed feeding point, a pointed outermost point farthest from the feeding point, and a planar region arranged between the feeding point and the outermost point, and the distance between the feeding point and the outermost point is equal to one half of the wavelength of a target wave. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antenna device that can be used in an ultra-wideband frequency range.

In recent years, a wireless communication system having a far wider frequency spectrum than conventional wireless communication has attracted attention. This ultra-wideband technology is generally called UWB (Ultra Wide Band). Therefore, in UWB, the occupied band is very wide and broadband communication is easily realized. Therefore, many manufacturers are trying to put it into practical use as an ultra-high-speed interface that connects digital devices such as a PDP (Plasma Display Panel) television, a camera-integrated VTR (Video Tape Recorder), a personal computer and peripheral devices. The antenna used for UWB has completely different characteristics from other narrow-band radio technologies so far, and a design method significantly different from the conventional one is required. For this reason, an antenna as disclosed in Patent Document 1 has been proposed.
Special table flat 10-500817

  However, since the conventional UWB antenna has a complicated antenna shape, it is difficult to mass-produce or use it as a small and high-performance antenna that can be used in consumer applications such as home appliances.

  The present invention has been made in view of the above problems.

The first invention is an antenna device comprising a pair of antenna elements, the antenna element is a point-shaped feeding point, a point-shaped outermost point farthest from the feeding point, the feeding point, The present invention relates to an antenna device comprising a planar region portion arranged in the middle of the outermost point, wherein a distance between the feeding point and the outermost point is a length of a half wavelength of a target wave.
A second invention relates to the antenna device according to the first invention, wherein the pair of antenna elements have the same shape.
A third invention relates to the antenna device according to the first invention or the second invention, wherein the antenna element has a quadrilateral shape.
A fourth invention relates to the antenna device according to the third invention, wherein the quadrilateral shape is a rhombus shape.
According to a fifth aspect of the invention, the change in impedance at the feed point is within 20% in absolute value with respect to the center value with respect to the change in frequency of the high-frequency signal input from the feed point. The antenna device according to any one of the above.
A sixth invention relates to the antenna device according to any one of the first to fifth inventions, wherein the antenna element is planar.
A seventh invention relates to the antenna device according to any one of the first to fifth inventions, wherein the antenna element has a three-dimensional shape.

  According to the present invention, the antenna device is composed of a pair of antenna elements. Since the change in impedance at the feeding point of the antenna device can be reduced, the antenna device can be used as an ultra-wideband antenna with a simple configuration.

Embodiments of the present invention will be described below. The relationship between the embodiment and the claims is generally as follows.
The first embodiment mainly describes claims 1, 2, 3, 4, 6 and the like.
The second embodiment mainly describes claim 5.
The third embodiment mainly describes claim 7.

<< Embodiment 1 >>
Embodiment 1 will be described below.

<Concept of Embodiment 1>
Below, the concept of Embodiment 1 will be described.
Recently, broadband communication called UWB has attracted attention. The used frequency band is 3.1 to 10.6 GHz. When the frequency used is divided in the system using UWB, which is attracting attention as the mainstay, (1) OFDM (Orthogonal Frequency Division Multiplexing) (2) DS-SS (Direct) It is classified into those using the Sequence Spectrum Spread (direct diffusion) method. (1) In the OFDM system, this entire frequency band (except for the frequency of the wireless LAN in the 5.2 GHz band) is used. (2) In the DS-SS system, (2-1) the lower side of the 3.1 GHz to 5.2 GHz band wireless LAN is used, and (2-2) the upper side of the 5.2 GHz band wireless LAN. It is classified into those using 10.6 GHz. Both systems are considered so as not to cause interference with the 5.2 GHz wireless LAN.

  The key technology in UWB here is the ultra-wideband antenna. The key technologies for designing an ultra-wideband antenna are: first, a high-frequency current flows near the feeding point of the antenna element, the shape of the antenna that distributes the high-frequency current at the end of the antenna element, and second, the frequency change For example, a structure applying anti-resonance that makes the change in impedance look dull at the feeding point is used. By using these technologies in combination, it is possible to realize a small and high gain ultra wideband antenna having a planar structure. The present embodiment relates to an antenna device that combines the above two techniques.

  FIG. 17 is a diagram illustrating an example of an antenna device 1700 having the first key technique. The antenna device illustrated in FIG. 17 includes antenna elements 1701 and 1702. Each antenna element has feeding points 1704 and 1705. The antenna element is connected to the electronic circuit unit 1703 from the feeding point via a lead wire. The pair of antenna elements is characterized by a triangular shape. The vicinity of the apex of the triangle is a feeding point. In the antenna element of FIG. 17, the shape of the antenna element on the side opposite to the feeding point (the triangle base side) is made planar or three-dimensionally large, and the high-frequency current flowing through the antenna element is reduced to the triangle shape The density of the high frequency current is lowered by dispersing at both ends. At this time, from the viewpoint of the high-frequency current, the position of the end of the antenna element (the bottom side of the triangle) is difficult to understand from the feeding point. That is, it becomes difficult to understand the resonance frequency of the antenna device from the feeding point. For this reason, even if high-frequency signals of various frequencies are input from the feed point, the current density near the feed point is high, but the current density at the end (bottom side of the triangle) is low, so the current distribution is constant. Waves are obscured and a wider band can be realized. Note that the triangular shape of the antenna element corresponds to an isosceles triangle, a right isosceles triangle, an unequal triangle, and the like. Moreover, it is not limited to planar shape, You may have a three-dimensional structure.

<Clarification of configuration requirements>
In the following, the configuration requirements of this embodiment will be clarified.
FIG. 1 is a diagram for explaining the configuration requirements of the antenna device 0100 of the present embodiment. The antenna device includes a pair of antenna elements 0101 and 0102. Each antenna element has feeding points 0104 and 0105, outermost points 0106 and 0107, and planar regions 0108 and 0109.

<Description of configuration requirements>
The configuration requirements of this embodiment will be described below.

<Antenna element>
Below, the component requirement of an antenna element is demonstrated.

(Feeding point)
The “feeding point” refers to a small dot-like region that is connected to the electronic circuit unit 0103 by a lead wire or the like and is supplied with power. The feeding point has a pointed shape. Here, the “pointed shape” refers to a pointed shape formed by matching two straight lines or curves at the tip thereof. The angle of the tip of the tip shape is not limited to a right angle, and may be an acute angle or an obtuse angle.

(Outermost point)
The “outermost point” refers to a point-like minute region farthest from the feeding point. The outermost point has a pointed shape. Here, the “pointed shape” refers to a pointed shape formed by matching two straight lines or curves at the tip thereof. The angle of the tip of the tip shape is not limited to a right angle, and may be an acute angle or an obtuse angle.

(Surface area)
The “planar region portion” refers to a planar region disposed between the feeding point and the outermost point. Here, the “surface” is not limited to a plate-shaped plane, and may be a smooth curved surface.

(Antenna element)
In the antenna element, the distance between the feeding point and the outermost point has a length of a half wavelength of the target wave. In addition, the distance between the feeding point and the outermost point of the antenna element is not limited to the length of the half wavelength of the target wave, and may be a length that is an odd multiple of the half wavelength. The shape of the antenna element is, for example, a quadrilateral shape. Furthermore, this quadrilateral shape is a rhombus shape as an example. Here, the rhombus shape includes a square. As an example, the antenna element having the above shape is formed to be planar. As an example, the antenna element can be made of a conductor such as gold, silver, copper, or aluminum, or a conductive ceramic. When the antenna element is configured to be planar, it can be easily mounted on a small UWB device by configuring the antenna element to be thin. As an example, the thickness of the antenna element corresponds to about 0.1 mm to 10 mm.

<Antenna device>
Hereinafter, the configuration requirements of the antenna device will be described.

(Antenna device)
The antenna device includes a pair of antenna elements. For example, the pair of antenna elements are formed so as to have the same shape. Each feeding point of the pair of antenna elements is connected to the electronic circuit unit of the UWB by a lead wire or the like. As an example, the electronic circuit unit of the UWB includes a broadband amplifier, a switch, a mixer, and the like.

  In general, the use bandwidth of an antenna is determined by how much the impedance of the feed point does not change with respect to the change of the frequency of the high-frequency signal input from the feed point. Hereinafter, based on the drawings, it will be described whether the antenna apparatus of the present embodiment operates in a wide band as a UWB antenna.

  FIG. 2 is a diagram showing an outline of the current distribution of the antenna device 0200 when power is supplied from the feeding point of the antenna element. The antenna device includes a pair of antenna elements 0201 and 0202. The feeding point of the antenna element is connected to the electronic circuit unit 0203 by a lead wire. Electric power is supplied from the electronic circuit unit. As shown in FIG. 2, the antenna device has a standing wave 0204 related to the current distribution. The standing wave has a valley (node) 1, a valley (node) 2, a valley (node) 3, a mountain (belly) 1, and a mountain (belly) 2. When power is supplied (voltage power supply) to the standing wave trough (node) 1, the change in impedance at the power feeding point becomes duller than when power is supplied to the standing wave peak (antinode) part as in the prior art. . This can be seen from the following equation. That is, in general, the impedance Z at the feeding point is

Z = V / I
(V: potential difference between feeding points of a pair of antenna elements, I: current flowing through the antenna elements)

It is represented by Here, when power is supplied (voltage power supply) to the peak (antinode) of the standing wave of the current distribution as in the past, the change in the frequency of the high-frequency signal input from the power supply point is The amplitude of the current distribution in the standing wave peak (antinode) (i.e., I in the above equation) varies. That is, in the above equation, if V is constant, it means that the impedance Z of the feeding point varies. However, as in this embodiment, when power is supplied (voltage power supply) to the portion of the standing wave trough (node) of the current distribution at the power supply point, the frequency of the high-frequency signal input from the power supply point is reduced. Thus, there is almost no fluctuation in the amplitude of the current distribution in the valley (node) of the standing wave (ie, I in the above equation). That is, assuming that V is constant, the impedance Z at the feeding point hardly changes. Therefore, according to the antenna device of the present embodiment, power can be fed (voltage fed) to the standing wave trough (node) of the current distribution, so that the frequency of the high-frequency signal input from the feeding point can be changed. On the other hand, since the change in the impedance Z at the feeding point can be reduced, a wide band can be realized.

(Example 1: Mainly corresponding to claims 2, 4, and 6)
Example 1 will be described below. The antenna device according to the first embodiment is characterized in that the shape of the antenna element is a planar square and the shape of the pair of antenna elements is the same.
FIG. 3 is a plan view or a bottom view of the antenna device according to the first embodiment. Here, as an example, if the operating frequency f is 3.1 to 10.6 GHz of UWB, the wavelength λ is expressed by the following equation, where the speed of light is c = 3.0 × 10 ⁸ (m / s). Calculated.

λ = c / f
= (3.0 × 10 ⁸ ) / (10.6 × 10 ⁹ )
~ (3.0 × 10 ⁸ ) / (3.1 × 10 ⁹ )
= About 28.3-96.8 (mm)

It becomes. Therefore, the antenna element is a square having a side length of about 10.2 to 34.2 mm (from (λ / 2) / √2).

FIG. 4 is a front view or a rear view of the antenna device according to the first embodiment.
FIG. 5 is a right side view or a left side view of the antenna device according to the first embodiment.
FIG. 6 is a perspective view of the antenna device according to the first embodiment.

  FIG. 7 shows a return loss (voltage return loss) or VSWR (Voltage Standing Wave Ratio) when using the antenna apparatus of this embodiment, and a UWB use frequency of 3.1 to 10.6 GHz. Is obtained by simulation. Here, the left vertical axis represents Return Loss (dB), the right vertical axis represents VSWR, and the horizontal axis represents the operating frequency (GHz). In general, if the return loss of the antenna is about −10 dB or less and converted to VSWR of about 2.0 or less, the antenna can be used without degrading the quality. Return Loss and VSWR are defined by the following equations, respectively.

Return Loss = 20 log (Vr / Vf) (dB)
(Vf: traveling wave voltage, Vf: reflected wave voltage)

VSWR = (1+ | ρ |) / (1− | ρ |)
(Ρ = Vr / Vf: voltage reflection coefficient)

  In FIG. 7, the Return Loss of the antenna device of the present embodiment is about −10 dB or less and about 2.0 or less in terms of VSWR, over the UWB use frequency of 3.1 to 10.6 GHz. I understand. In FIG. 7, the wavelength λ is calculated as 6.85 GHz, which is the center frequency of the UWB operating frequency 3.1 to 10.6 GHz, and the length of one side of the antenna element is calculated as approximately 15.5 mm. ing.

(Example 2: Mainly corresponding to claim 1)
Example 2 will be described below. The antenna device according to the second embodiment is characterized in that the shapes of the pair of antenna elements are not the same.
FIG. 8 is a plan view or a bottom view illustrating an example of the antenna device according to the second embodiment. In the antenna device shown in FIG. 8, the shape of the antenna element on the right side is a square, and the shape of the antenna element on the left side is rounded at the two corners of the square except for the feeding point and the outermost point. It is characterized by having.

(Example 3: mainly corresponding to claim 2)
Example 3 will be described below. The antenna device according to the third embodiment is characterized in that the shape of the pair of antenna elements is the same.
FIG. 9 is a plan view or a bottom view illustrating an example of the antenna device according to the third embodiment. The antenna device shown in FIG. 9 is characterized in that the shape of the pair of antenna elements is rounded at two corners other than the feeding point and the outermost point among the four corners of the square.

(Example 4: mainly corresponding to claims 2 and 3)
Example 4 will be described below. The antenna device according to the fourth embodiment is characterized in that the antenna element has a quadrilateral shape.
FIG. 10 is a plan view or a bottom view illustrating an example of the antenna device according to the fourth embodiment. The antenna device shown in FIG. 10 is characterized in that the shape of the pair of antenna elements is a rectangle. Note that the shape of the pair of antennas may be different.

(Example 5: mainly corresponding to claims 2 and 4)
Example 5 will be described below. The antenna device according to the fifth embodiment is characterized in that the antenna element has a rhombus shape.
FIG. 11 is a plan view or a bottom view illustrating an example of the antenna device according to the fifth embodiment. The antenna device shown in FIG. 11 is characterized in that the shape of the pair of antenna elements is a rhombus. Note that the shape of the pair of antennas may be different.

        <Simple explanation of effect of Embodiment 1>

  According to the antenna device of the present embodiment, since the change in impedance at the feed point can be reduced with respect to the change in the frequency of the high-frequency signal input from the feed point, a wide band can be realized.

<< Embodiment 2 >>
The second embodiment will be described below.

<Concept of Embodiment 2>
Below, the concept of Embodiment 2 is demonstrated.
The antenna apparatus according to the first embodiment is such that the change in impedance at the feed point is within 20% in absolute value with respect to the center value with respect to the change in the frequency of the high-frequency signal input from the feed point. About.
FIG. 12 is a diagram illustrating an example of the relationship between the UWB use frequency (horizontal axis) and the impedance of the feeding point (vertical axis). When the feed point impedance is 50Ω with respect to 6.85 GHz which is the center frequency of the frequency 3.1 to 10.6 GHz of the high frequency signal input from the feed point, the antenna device of the present embodiment is 45 to 55Ω. It is comprised so that it may become.

        <Simple explanation of effect of embodiment 2>

  According to the antenna device of the present embodiment, a high-quality antenna device is provided for a UWB usage region by making the change in impedance at the feeding point within 20% in absolute value with respect to the center value. Can do.

  << Embodiment 3 >>

<Concept of Embodiment 3>
The concept of Embodiment 3 will be described below.
The antenna device according to the present embodiment relates to the antenna device according to the first or second embodiment, in which the antenna element has a three-dimensional shape.

(Example 6)
Example 6 will be described below. The antenna device according to the sixth embodiment has a three-dimensional shape.
FIG. 13 is a plan view or a bottom view of the antenna device according to the sixth embodiment.
FIG. 14 is a front view or a rear view of the antenna device according to the sixth embodiment.
FIG. 15 is a right side view or a left side view of the antenna device according to the sixth embodiment.
FIG. 16 is a perspective view of the antenna device according to the sixth embodiment.

        <Simple explanation of effect of Embodiment 3>

  According to the antenna device of the present embodiment, since the change in impedance at the feed point can be reduced with respect to the change in the frequency of the high-frequency signal input from the feed point, a wide band can be realized.

  The present invention can be used as a small and high-performance UWB antenna that can be used in consumer applications such as home appliances.

Conceptual diagram of the antenna device of the first embodiment The figure explaining operation | movement of the antenna apparatus of Embodiment 1. The top view or bottom view of Example 1 of the antenna apparatus of Embodiment 1 The left view or right view of Example 1 of the antenna apparatus of Embodiment 1 Front view or rear view of Example 1 of antenna apparatus of Embodiment 1 The perspective view of Example 1 of the antenna apparatus of Embodiment 1. FIG. Explanatory drawing of Example 1 of the antenna apparatus of Embodiment 1. FIG. The top view or bottom view of Example 2 of the antenna apparatus of Embodiment 1 The top view or bottom view of Example 3 of the antenna apparatus of Embodiment 1 The top view or bottom view of Example 4 of the antenna device of Embodiment 1 The top view or bottom view of Example 5 of the antenna apparatus of Embodiment 1 Explanatory drawing of the antenna apparatus of Embodiment 2. The top view or bottom view of Example 6 of the antenna device of Embodiment 3 Left side view or right side view of Example 6 of the antenna device of Embodiment 3 Front view or rear view of Example 6 of antenna apparatus of Embodiment 3 The perspective view of Example 6 of the antenna apparatus of Embodiment 3. FIG. Schematic diagram of antenna device 2 of Embodiment 1

Explanation of symbols

0100 Antenna device 0101 Antenna element 0102 Antenna element 0103 Electronic circuit part 0104 Feeding point 0105 Feeding point 0106 Outermost point 0107 Outermost point 0108 Planar region part 0109 Planar region part

Claims (7)

An antenna device comprising a pair of antenna elements,
The antenna element is
A point-shaped feeding point;
A pointed outermost point furthest away from the feed point;
A planar region disposed between the feeding point and the outermost point;
Consists of
An antenna apparatus, wherein a distance between the feeding point and the outermost point is a length of a half wavelength of a target wave.   The antenna device according to claim 1, wherein the pair of antenna elements have the same shape.   The antenna device according to claim 1, wherein the antenna element has a quadrilateral shape.   The antenna device according to claim 3, wherein the quadrilateral shape is a rhombus shape.   The antenna apparatus according to any one of claims 1 to 4, wherein a change in impedance at a feeding point is within 20% in absolute value with respect to a center value with respect to a change in frequency of a high-frequency signal input from the feeding point.   The antenna device according to claim 1, wherein the antenna element is planar.   The antenna device according to claim 1, wherein the antenna element has a three-dimensional shape.

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