JP4940842B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device, and more particularly to an antenna device for UWB (Ultra Wide band).

  UWB generally means ultra-wideband radio, and is a broad term that refers to a radio transmission system that occupies a bandwidth of 25% or more of the center frequency or 1.5 GHz or more. In other words, this is a technology for communication using ultra-wideband short pulses (usually 1 ns or less).

  The difference between conventional radio and UWB is the presence or absence of a carrier wave. Specifically, in the conventional radio, a sine wave of a certain frequency called a carrier wave is modulated by various methods to transmit / receive data, whereas in UWB, a short pulse of an ultra-wide band is used without using a carrier wave. It has become. In addition, the conventional radio has a narrow frequency band, whereas UWB has an ultra-wideband frequency band. This is because, in conventional radio, radio waves are a finite resource, and it is considered that radio waves can be utilized when the frequency band is narrow. However, in UWB, the output energy at each frequency is very small, and interference with other wireless communications does not become a problem, so that the frequency band can be widened.

  Thus, since UWB is an ultra-wideband, the frequency band overlaps with the existing wireless communication service. Therefore, the UWB frequency band is currently limited to between 3.1 and 10.6 GHz.

  Further, the antenna device basically uses a resonance phenomenon, and the resonance frequency is determined by the length of the radiating element, etc., so that the more the frequency components are included, the more difficult it is to resonate. And there exists a problem that the design of an antenna apparatus will become difficult, so that a frequency band becomes wide like UWB.

  Here, an ultra-small ceramic chip antenna for UWB has been developed as a next-generation technology capable of simultaneously realizing large-capacity data transmission and low power consumption in short-range wireless communication. With the development of such ceramic chip antennas, UWB, which has been limited to military applications until now, has been expanded to consumer applications such as ultra-high-speed data transmission between digital devices such as PDP (Plasma Display Panel) TVs and digital cameras. It is possible to reduce the size of the equipment in view. Such a UWB antenna can be used for applications such as Bluetooth (registered trademark) and wireless LAN (Local Area Network).

  The inventors of the present invention have proposed a UWB antenna capable of improving frequency characteristics while increasing the bandwidth (for example, Patent Document 1). The antenna device described in Patent Document 1 includes an upper dielectric, a lower dielectric, and a conductor pattern sandwiched between them. The conductor pattern has a feeding point at a substantially central portion of the front surface, and includes an inverted triangular portion extending from the feeding point to the right side surface and the left side surface at a predetermined angle, and a rectangular portion whose bottom side is in contact with the upper side of the inverted triangular portion. It is configured.

The present inventors have also proposed an antenna device that exhibits a low VSWR characteristic over a wide band by lowering the low-frequency limit frequency (for example, Non-Patent Document 1 to Non-Patent Document 2). As shown in FIG. 7, the antenna device 30 includes a ground plate 32 extending in a horizontal plane, and a radiating element 33 arranged on the surface of the ground plate 32 so as to be perpendicular to the ground plate 32. And the radiating element 33 is fan-shaped. In this way, by providing the fan-shaped radiating element 33 upright on the ground plate 32, the VSWR characteristics can be reduced over a wide band (see FIG. 6). Moreover, as shown in FIG. 8, an antenna apparatus 50 including a radiating element 53 formed by providing a fan-shaped flat plate in a cruciform structure has been proposed. According to such an antenna device 50, it is possible to reduce the VSWR characteristic over a wider band by reducing the orthogonal polarization component in the high band (see FIG. 6).
JP 2005-94437 A Morishita, Yamauchi, Nakano, “Linear Broadband Fan Antenna”, IEICE Communication Society Conference, B-1-158, Hokkaido, September 2005 Morishita, Yamauchi, Nakano, “Linear Broadband Fan Antenna 2nd Report”, IEICE Communication Conference, B-164, Tokyo, March 2006

  However, in the conventional antenna device, the VSWR characteristic can be reduced over a wide band. However, in the frequency of the characteristic used for applications other than UWB (for example, 5.8 GHz in the case of an automatic fee system (ETC)) On the other hand, there was a problem that it might become an obstacle.

  The present invention has been made in view of these points, and an object of the present invention is to provide an antenna device capable of setting a desired stop band.

In order to solve the above problem, the invention according to claim 1 is:
In an antenna apparatus comprising: a ground plate ; a radiating element disposed on the ground plate so as to be perpendicular to the ground plate; and a power feeding means for feeding power to the ground plate and the radiating element .
The radiating element includes a plurality of unit feeding surfaces arranged radially with respect to a central axis along a vertical direction from the ground plate,
The edge of the unit feeding surface is
A reference straight line located on the central axis;
An upper arc curve that is a part of an arc centered on one point on the reference straight line;
A side edge curve consisting of a curve represented by an exponential function connecting the location closest to the ground plate and one end of the upper arc curve, and
A conductive member that connects the upper arc curve or the side edge curves of the unit feeding surface is provided.

The invention according to claim 2 is the antenna device according to claim 1 ,
The radiating element includes the unit feeding surface so as to be line symmetric with respect to the central axis.

The invention according to claim 3 is the antenna device according to claim 1 or 2 ,
The radiating element includes the unit feeding surface so that angles formed by the unit feeding surfaces are equal.

The invention according to claim 4 is the antenna device according to claim 3 ,
The number of unit feeding surfaces is four.

Invention of Claim 5 is an antenna apparatus as described in any one of Claims 1-4 ,
The conductive member is a metal wire, and is electrically connected to the upper arc curve or the side edge curve of the unit feeding surface.

The invention according to claim 6 is the antenna device according to claim 5 ,
The metal wire is bent at a portion not connected to the upper arc curve or the side edge curve of the unit feeding surface, and the length thereof is adjusted.

The invention according to claim 7 is the antenna device according to claim 6 ,
The metal wire is provided such that a portion of the unit feeding surface that is not connected to the upper arc curve or the side edge curve approaches toward the central axis side.

The invention according to claim 8 is the antenna device according to any one of claims 5 to 7 ,
The metal wire connects the upper arc curves or the side edge curves of all the unit feeding surfaces.

According to the first aspect of the present invention, the apparatus includes a plurality of unit feeding surfaces arranged radially with respect to the central axis, and a conductive member that connects the upper arc curves or the side edge curves of the unit feeding surfaces. Thus, it is possible to set a stop band at a specific frequency in the antenna device. Further, since the shape of the unit feeding surface constituting the radiating element is a shape formed from the reference straight line, the upper arc curve, and the side edge curve, the VSWR characteristic can be reduced even in a high frequency band. Therefore, the usable frequency band other than the stop band can be made wider.

According to the invention described in claim 2 , since the unit feeding surface is provided line-symmetrically in the radiating element, it can be a line-symmetric radiating element, and the radiation pattern of the antenna device can be made uniform. Directivity can be improved.

According to the invention described in claim 3 , since the unit feeding surfaces are arranged radially so that the angles formed by the unit feeding surfaces are equal to each other, the radiation element is configured. Directivity can be improved.

According to the invention described in claim 4 , since the unit feeding surfaces are arranged radially at 90 ° intervals so that the angles formed by the four unit feeding surfaces are equal, the radiation element is configured. A cruciform structure can be adopted, and the VSWR characteristics can be reduced even in a low frequency band. Therefore, the usable frequency band other than the stop band can be made wider.

According to the invention described in claim 5 , it is possible to easily set the stop band by electrically connecting the metal wires such as soldering.

According to the invention described in claim 6 , the length of the metal wire can be easily adjusted by bending a portion not used for connection with the unit feeding surface. It is possible to adjust the center frequency of the stop band by adjusting. Therefore, an antenna device capable of setting a stop band at a desired center frequency can be obtained.

According to the seventh aspect of the present invention, the metal wire is provided so that a portion not connected to the upper arc curve or the side edge curve of the unit feeding surface approaches the central axis side. The line does not protrude outward (in the direction away from the central axis) from the radiating element, and it is possible to prevent the antenna device from becoming large.

According to the invention described in claim 8 , since the metal wire connects the upper circular arc curves or the side edge curves of all the unit feeding surfaces, the radiating element goes around. Therefore, the metal wires are evenly provided around the radiating elements, and it is possible to prevent the radiation pattern from becoming unbalanced, and it is possible to set the stop band without reducing the directivity of the antenna device. .

  An embodiment of an antenna device according to the present invention will be described below with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

  As shown in FIG. 1, the antenna device 1 according to the present embodiment includes a disc-shaped ground plate 2 having a radius of 20 mm, and a radiating element 3 disposed on the ground plate 2 so as to be perpendicular to the ground plate 2. Is provided. Here, the surface of the ground plate 2 is the XY plane, and the vertical direction is the Z direction.

  The ground plate 2 is formed of a conductive material such as copper, aluminum, gold, silver, or platinum. In the center of the ground plate 2, a hole 2a as a ground feeding point is formed penetrating in the Z direction. A power supply means (not shown) for supplying power to the ground plate 2 is connected to the lower surface side of the ground plate 2 and on the circumference of the hole 2a. A feed line 4 that feeds power to the radiating element 3 through a dielectric is passed through the hole 2a. In addition, there is no restriction | limiting in particular in the power supply means to the ground plate 2 and the radiation element 3, and it can change suitably, and power supply means is simplified and illustrated in drawings other than FIG.

  The radiating element 3 is formed of a conductive material as in the case of the ground plate 2, and a plurality of unit feeding surfaces 6 that are arranged radially with respect to the central axis 5 along the Z direction from the center of the ground plate 2. It has ... Specifically, in the present embodiment, the radiating element 3 includes four unit feeding surfaces 6 and is arranged at intervals of 90 ° with respect to the central axis 5 as shown in FIG. A power supply line 4 that supplies power to the radiating element 3 is electrically connected to the lower end of the central shaft 5. The number and arrangement relationship of the unit power supply surfaces 6 are not particularly limited, but it is preferable to arrange the unit power supply surfaces 6 so that the angles formed by the unit power supply surfaces 6 are equal with respect to the central axis 5. The unit feeding surface 6 is preferably shaped so as to be line symmetric with respect to the central axis 5.

  As shown in FIG. 3, the edge of the unit power supply surface 6 is a reference straight line 6 a located on the central axis 5 and a part of an arc centering on one point on the reference straight line 6 a above the unit power supply surface 6. The upper arc curve 6b is composed of a side edge curve 6c composed of an exponential function connecting a portion closest to the ground plate 2 and one end of the upper arc curve 6b. The upper arc curve 6b is a part of an arc having a radius r centered on a point separated from the lower end of the reference straight line 6a by a predetermined distance r. The inner angle of the upper arc curve 6b is α, and the other end coincides with the upper end of the reference straight line 6a. In the present embodiment, the radius r is 21.8 mm, and the inner angle 2α is 120 °.

The side edge curve 6c is a curve represented by the following formula (1), where the coordinates of one end of the upper arc curve 6b are (y1, z1) on the YZ plane with the lower end of the reference straight line 6a as the origin. In addition, the coefficient a in this embodiment is 0.221651. Moreover, the length dimension of each part of the ground plate 2 and the radiation element 3 can be suitably changed according to the resonance frequency and use band to obtain | require.
y =-[exp {-a (z-z1)}-1] + y1 (1)

  The radiating element 3 includes a conductive member that connects edges that are not located on the central axis 5 of the unit feeding surface 6. The conductive member is a metal wire 7 in the present embodiment, and goes around the radiating element 3 to connect the edges of all the unit power supply surfaces 6. The metal wire 7 is fixed to a connecting portion between the upper arc curve 6b and the side edge curve 6c by soldering or the like. There is no restriction | limiting in particular in the fixing location of the metal wire 7, According to the shape of the unit electric power feeding surface 6, etc., it can change suitably. Further, the metal wire 7 is not limited to connecting the edges of all the unit feeding surfaces 6 around the radiating element 3, but can be appropriately changed so that the radiation pattern of the antenna device 1 is uniform. The conductive member is not limited to the metal wire 7 as long as it is conductive. However, the metal wire 7 is preferable because it can be easily fixed and electrically connected to the unit feeding surface 6 by soldering or the like.

  A portion of the metal wire 7 that is not connected to the edge of the unit power supply surface 6 may be linear, or may be bent and the length of the metal wire 7 may be adjusted. For example, as shown in FIG. 4, the center M may be bent in the space between the edges of the unit feeding surface 6. The metal wire 7 bent at the center M changes the length dimension of the metal wire 7 by changing the position of the center M in the Z direction without changing the connection point between the metal wire 7 and the unit feeding surface 6. It can be made to. That is, as shown in FIG. 5, the center frequency of the stop band is adjusted by changing the length dimension of the metal wire 7 by adjusting the height h from the lower end of the unit feeding surface 6 to the center M in the Z direction. It is supposed to be. Further, by changing the position of the center M in the Z direction, the metal wire 7 does not protrude outward (in the direction away from the central axis 5) from the radiating element 3, and the radiating element 3 provided with the metal wire 7 has the same structure. It is possible to avoid an increase in size. Although the center M changes its position along the Z direction, it may be provided so as to approach the center axis 5 side.

The ground plate 2 and the radiating element 3 are disposed so as to be separated in the Z direction by a predetermined distance delta _FD. Particularly limited interval delta _FD between the ground plate 2 and the radiating element 3 are not, can be tailored to conditions such as impedance matching. Interval delta _FD in the present embodiment is 0.375 mm.

Next, the operation of this embodiment will be described.
When the antenna device 1 transmits radio waves, a current is supplied to the radiating element 3 and the ground plate 2 with a predetermined amplitude and phase through a power feeding unit based on an electric signal from the signal processing device. The current fed to the radiating element 3 flows along the side edge curve 6c and the upper arc curve 6b of each unit feeding surface 6. As described above, when current flows through the radiating element 3 and the ground plate 2, radio waves are transmitted from the antenna device 1.

  When the antenna device 1 receives a radio wave, when a radio wave having a predetermined frequency is received by the radiating element 3, a voltage current having an amplitude and a phase corresponding to the received radio wave is supplied from the radiating element 3 and the ground plate 2 to the feeding unit. Flowing. And the electric current which injected into the electric power feeding means is transmitted to a signal processing apparatus, and is processed as an electrical signal.

Next, antenna characteristics of the antenna device 1 of the present embodiment will be described.
First, as shown in FIG. 6, in a conventional antenna device that does not include a conductive member, the VSWR characteristics are uniformly reduced in a wide frequency band, and no stop band is set. Here, “Flat” in FIG. 6 refers to the conventional antenna device 30 that forms a flat radiating element 33 by arranging two unit feeding surfaces so as to be line-symmetric as shown in FIG. That is. In addition, “Crossed” in FIG. 6 is a conventional antenna device 50 in which the radiating element 53 is configured by arranging four unit feeding surfaces at intervals of 90 ° with respect to the central axis as shown in FIG. is there. In this way, by increasing the number of unit feeding surfaces from two to four and arranging the four unit feeding surfaces so as to have a cross-shaped structure in plan view, the radiating element 53 is configured, so that the VSWR can be widely used. The characteristics are lowered, and a wider frequency band can be used. Here, “VSWR ₅₀ ” on the vertical axis in FIG. 6 indicates the VSWR characteristic when power is supplied at 50Ω.

  Subsequently, as shown in FIG. 9, it is understood that a stop band at a specific frequency is set in the antenna device according to the present invention including the conductive member. Further, the center frequency of the stop band is changed by changing the height h of the center M, which is the bent portion of the metal wire 7. That is, the center frequency of the stop band can be adjusted by changing the height h of the center M to adjust the length of the metal wire 7.

  As described above, according to the antenna device 1 according to the present embodiment, the plurality of unit feeding surfaces 6 arranged radially with respect to the central axis 5 are provided, and the edges that are not located on the central axis 5 of the unit feeding surface 6 are arranged. By providing the metal wire 7 as a conductive member to be connected, it is possible to set a stop band at a specific frequency in the antenna device 1.

  Since the stop band can be set in the antenna device 1 itself, it is not necessary to separately provide a stop filter or the like in the antenna device, and the number of parts can be reduced. Also, compared to the case where the stop band is set by providing the stop filter or the like in the antenna device, an antenna apparatus in which a stop band of a desired center frequency is set in advance can be manufactured, so that the stop band is set accurately. It is possible.

  Further, since the shape of the unit feeding surface 6 constituting the radiating element 3 is a shape formed from the reference straight line 6a, the upper circular arc curve 6b, and the side edge curve 6c, the VSWR characteristic is lowered even in a high frequency band. Is possible. Therefore, the usable frequency band other than the stop band can be made wider.

  Further, when the unit feeding surface 6 is provided with line symmetry in the radiation element 3, it is possible to make the radiation element 3 have a line symmetry shape, and the radiation pattern of the antenna device 1 can be made uniform and the directivity can be improved. It is.

  Further, if the radiating element 3 is configured by arranging the radiating elements 3 so that the angles formed by the unit feeding surfaces 6 are equal, the radiation pattern of the antenna device 1 can be made uniform and the directivity can be improved. .

  Further, by forming the radiating element 3 by arranging the four unit feeding surfaces 6 radially at equiangular (90 °) intervals, a planar cross-shaped structure can be obtained, and the VSWR characteristic can be obtained even in a low frequency band. It can be reduced. Therefore, the usable frequency band other than the stop band can be made wider.

  Further, by using the metal wire 7 as the conductive member, it is easy to make an electrical connection such as soldering, and it is possible to easily set the stop band.

  Further, by using the metal wire 7 as the conductive member, it is possible to easily adjust the length by bending a portion that is not used for connection with the unit feeding surface 6, and to adjust the center frequency of the stop band. It is possible. Therefore, the antenna device 1 can set the stop band at a desired center frequency.

  Further, when the metal wire 7 is provided so that a portion not connected to the edge of the unit feeding surface 6 approaches the central axis 5 side, the metal wire 7 is outside from the radiating element 3 (in a direction away from the central axis 5). It is possible to prevent the antenna device 1 from becoming large.

  Further, since the metal wire 7 connects all the edges of the four unit power supply surfaces 6, the radiating element 3 goes around. Therefore, the metal wire 7 is evenly provided around the radiating element 3, so that the radiation pattern can be avoided from being unbalanced, and the stop band can be set without reducing the directivity of the antenna device 1. It becomes possible.

  In the present embodiment, four unit power supply surfaces 6 are used. However, as shown in FIG. 10, two unit power supply surfaces 6 may be used. In that case, if the unit feeding surface 6 is arranged so as to be line-symmetric with respect to the central axis (not shown), the flat radiating element 3 is configured. The metal wire 7 is provided so as to connect the edges of the unit power supply surfaces 6 and be curved so as to be circular in plan view.

  Further, as shown in FIG. 11, three unit feeding surfaces 6 may be used. In this case, the unit power supply surfaces 6 are arranged radially so that the angles formed by the unit power supply surfaces 6 are equal with respect to the central axis 5. Further, the metal wire 7 is provided so as to connect the edges of the unit power supply surfaces 6 and to form a regular triangle in plan view.

It is a perspective view which shows the antenna apparatus which concerns on this invention. It is a top view of the antenna apparatus which concerns on this invention. 1 is a side view of an antenna device according to the present invention. It is a perspective view which shows the modification of the antenna device which concerns on this invention. It is a side view which shows the modification of the antenna device which concerns on this invention. It is a graph which shows the antenna characteristic of the conventional antenna device. It is a perspective view of the conventional antenna device. It is a perspective view of the conventional antenna device. It is a graph which shows the characteristic of the antenna device which concerns on this invention. It is a perspective view which shows the modification of the antenna device which concerns on this invention. It is a perspective view which shows the modification of the antenna device which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna apparatus 2 Ground board 2a Hole part 3 Radiating element 4 Feeding line 5 Center axis 6 Unit feeding surface 6a Reference straight line 6b Upper circular arc curve 6c Side edge curve 7 Metal wire

Claims (8)

In an antenna apparatus comprising: a ground plate ; a radiating element disposed on the ground plate so as to be perpendicular to the ground plate; and a power feeding means for feeding power to the ground plate and the radiating element .
The radiating element includes a plurality of unit feeding surfaces arranged radially with respect to a central axis along a vertical direction from the ground plate,
The edge of the unit feeding surface is
A reference straight line located on the central axis;
An upper arc curve that is a part of an arc centered on one point on the reference straight line;
A side edge curve consisting of a curve represented by an exponential function connecting the location closest to the ground plate and one end of the upper arc curve, and
An antenna device comprising: a conductive member that connects the upper arc curve or the side edge curves of the unit feeding surface. The antenna device according to claim 1 , wherein the radiating element includes the unit feeding surface so as to be line-symmetric with respect to the central axis. The radiating elements, the antenna device according to claim 1 or 2, characterized in that it comprises the unit feeding surface as the angle between the unit power supply plane are equal. The antenna device according to claim 3 , wherein the number of the unit feeding surfaces is four. The conductive member is a metal wire, antenna according to any one of claims 1 to 4, characterized in that it is electrically connected to the upper arcuate curve or said side edge curves of the unit feeding surface apparatus. The antenna according to claim 5 , wherein the length of the metal wire is adjusted by being bent at a portion not connected to the upper circular arc curve or the side edge curve of the unit feeding surface. apparatus. The metal wire, according to claim wherein the upper arc-shaped curved line or the side edges curve unconnected portions of the unit feeding surface, characterized in that are provided so as to approach toward the central axis side 6 The antenna device according to 1. The antenna device according to any one of claims 5 to 7 , wherein the metal wire connects the upper arc curve or the side edge curves of all the unit feeding surfaces.

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