JP6489153B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device that is thin and capable of directivity control even when the antenna occupation area is elongated.

  In recent years, wireless communication devices have been used not only in mobile phones and notebook personal computers with built-in wireless communication functions but also in various fields such as in-vehicle use, and there is a demand for thinner and smaller devices. In addition, it is desired that stable antenna characteristics can be obtained even when close to a human body. With these demands, the formation area and arrangement of the mounted antenna device are limited, and it is often difficult to obtain directivity in the required direction.

Conventionally, as a technique for controlling directivity and reducing changes in antenna characteristics due to the human body, for example, Patent Document 1 discloses a space that can be allocated to an antenna by providing a plurality of feeding ports and switching feeding positions. Thus, an antenna device capable of switching the directivity has been proposed.
Patent Document 2 proposes an antenna device including a rectangular one-wavelength loop antenna element that is installed close to a radio base plate. Furthermore, Patent Document 3 proposes an antenna device that includes a plurality of linear elements and plate elements provided on a ground plane.

JP 2011-55428 A JP 2002-43826 A JP 2003-87043 A

However, the following problems remain in the above-described conventional technology.
As described above, Patent Document 1 proposes an antenna apparatus that can switch directivity in an antenna space that is allocated to an antenna by providing a plurality of feeding ends and switching feeding positions. In the case of this configuration, since a plurality of feeding points are provided, it is necessary to design in consideration of interference between the feeding terminals, and interference cannot be suppressed in a limited antenna space, and a desired directivity can be obtained. It is difficult, and it is difficult to reduce the size and thickness. In addition, since a plurality of variable reactance units and variable matching circuits are provided, the circuit configuration becomes complicated, which affects the design conditions around the antenna space and is difficult to reduce in thickness. In particular, there is an inconvenience that it is difficult to control directivity with respect to a limited antenna space such as an elongated case.
Patent Document 2 proposes an antenna device including a rectangular one-wavelength loop antenna element that is installed in the vicinity of a radio base plate. In the case of this configuration, by bending both ends of the loop antenna element toward the power feeding part, a current distribution is formed in which the current at the folded-up frontmost part becomes zero, but the ratio of the short side to the long side is important. At the same time, a phase circuit is required for the antenna design conditions and the like, the degree of freedom of the antenna design conditions is lowered, and it is difficult to obtain antenna performance such as desired directivity. Further, since the current distribution is concentrated on the loop antenna and the current distribution flowing on the radio base plate is reduced, it is significantly affected by peripheral parts and the human body in the vicinity of the antenna portion, and it is difficult to reduce the thickness. In particular, there is an inconvenience that it is difficult to control the directivity with respect to a limited antenna occupation area such as a long and narrow case.
Furthermore, Patent Document 3 proposes an antenna device in which a plurality of cleaning elements and plate-like elements provided on a ground plane are configured. In particular, in an inverted F type antenna or an inverted L type monopole antenna that requires a quarter of the wavelength with respect to a so-called desired resonance frequency, an antenna using the ground plane is used. High-frequency current easily flows on the (ground plane), and the degree of freedom in design such as antenna design and housing design for peripheral parts, etc. is reduced, and it is difficult to achieve downsizing and desired directivity (antenna characteristics). .

  The present invention has been made in view of the above-described problems, and provides an antenna device that can be thinned, can control directivity even in an elongated antenna occupation region, and can reduce the influence of peripheral components. The purpose is to do.

  The present invention employs the following configuration in order to solve the above problems. That is, an antenna device according to a first aspect of the present invention includes an insulating substrate body, a ground surface patterned with a metal foil on the substrate body, and an area on which the ground surface is not formed on the substrate body. An antenna occupying region provided in contact with one side of the substrate body and extending in a strip shape along the one side, an open type antenna element patterned with a metal foil in the antenna occupying region, the ground plane and the open type And an adjustment element that is patterned with a metal foil between the antenna element and extends along the base end side of the open antenna element, and the open antenna element is provided on the end side of the antenna occupation region. A feeding point is provided on the base end side disposed in the vicinity of the ground plane and extends over substantially the entire length of the antenna occupying region, and the impedance A first passive element that enhances power, and the adjustment element has a base end connected to the ground plane and is connected to the open antenna element via a passive element, the open antenna element And the first passive element is connected to the ground plane via the adjustment element.

  In this antenna device, the open-type antenna element is provided with a feeding point on the base end side disposed in the vicinity of the ground plane on the end side of the antenna occupying area and extends over substantially the entire length of the antenna occupying area. The first passive element for increasing the impedance is connected in series, the adjustment element is connected to the ground plane at the base end, and is connected to the open antenna element via the passive element. Since one passive element is connected to the ground plane via the adjustment element, the first passive element has a high impedance at the base end side to suppress high-frequency current flowing through the ground plane, and is open from the first passive element. The directivity can be controlled by the length to the tip of the antenna element. Therefore, it is not necessary to stand the antenna element member on the substrate body separately, so that it is possible to reduce the thickness and improve the antenna performance such as directivity and radiation efficiency even in the elongated antenna occupying region extending in a band shape. Can be made.

An antenna device according to a second invention is characterized in that, in the first invention, an antenna element of a dielectric antenna is connected to the middle or tip of the open antenna element.
That is, in this antenna device, since the antenna element of the dielectric antenna is connected to the middle or tip of the open antenna element, the length of the open antenna element can be shortened to further reduce the overall size.

The antenna device according to a third aspect of the present invention is the antenna device according to the first or second aspect, wherein the second passive element that connects the middle of the adjustment element and a base end side of the open-type antenna element with respect to the first passive element. And at least one of a third passive element that connects the distal end of the adjustment element and the distal end side of the first passive element of the open antenna element.
That is, in this antenna device, the second passive element that connects the middle of the adjustment element and the base end side of the first passive element of the open antenna element, the distal end of the adjustment element, and the first of the open antenna element Since at least one of the third passive element that connects the tip side to the passive element is provided, the resonance frequency adjustment and the impedance adjustment can be flexibly performed by setting the second passive element and the third passive element.

In the antenna device according to a fourth invention, in any one of the first to third inventions, a fourth passive element is connected between the first passive element and a tip of the open antenna element. Features.
That is, in this antenna device, since the fourth passive element is connected between the first passive element and the tip of the open antenna element, the entire electrical length can be adjusted by setting the fourth passive element. The resonance frequency can be adjusted.

The present invention has the following effects.
According to the antenna device of the present invention, the open antenna element is provided with a feeding point on the base end side disposed near the ground plane on the end side of the antenna occupying area and extends over substantially the entire length of the antenna occupying area. The first passive element for increasing the impedance is connected in series to the base end side, and the adjustment element is connected to the ground plane through the base end and is connected to the open antenna element via the passive element. Since the antenna element and the first passive element are connected to the ground plane through the adjustment element, the antenna element and the first passive element can be reduced in thickness, and the antenna performance such as directivity and radiation efficiency can be achieved even in an elongated antenna occupation region. Can be improved.

It is a top view which shows one Embodiment of the antenna device which concerns on this invention. In this embodiment, it is a back view which shows an antenna device. In this embodiment, it is the top view to which the principal part which shows an antenna device was expanded. In this embodiment, it is a wiring diagram which shows an antenna apparatus. In this embodiment, they are a perspective view (a), a plan view (b), a front view (c), a bottom view (d), and a rear view (e) showing an antenna element. In the Example of the antenna apparatus which concerns on this invention, it is a graph which shows a VSWR characteristic. In the Example of this invention, it is a graph which shows a radiation pattern when length d1 of an open type antenna element is set to 36.5. In the Example of this invention, it is a graph which shows a radiation pattern when length d1 of an open type antenna element is set to 16.5 mm (a) and 26.5 mm (b).

  Hereinafter, an embodiment of an antenna device according to the present invention will be described with reference to FIGS.

  As shown in FIGS. 1 to 4, the antenna device 1 according to the present embodiment includes a rectangular insulating substrate body 2 and a ground plane patterned on the substrate body 2 with a metal foil such as a copper foil. GND, an antenna occupation area AOA which is provided on the board body 2 in contact with one side of the board body 2 as an area where the ground plane GND is not formed and extends in a band shape along the one side, and the antenna occupation area An open antenna element 3 having a pattern formed of a metal foil such as a copper foil in the AOA and having an antenna element AT of a dielectric antenna connected to the tip thereof is provided.

  The open antenna element 3 is provided with a feeding point FP on the base end side disposed in the vicinity of the ground plane GND on the end side of the antenna occupation area AOA and extends over substantially the entire length of the antenna occupation area AOA. A first passive element P1 that increases impedance on the side is connected in series.

In addition, the antenna device 1 includes an adjustment element that is patterned with a metal foil such as a copper foil between the ground plane GND and the open antenna element 3 and extends along the base end side of the open antenna element 3. 4 is provided.
The adjustment element 4 has a base end connected to the ground plane GND and is connected to the open antenna element 3 via a passive element. The open antenna element 3 and the first passive element P1 are connected to the adjustment element 4. Is connected to the ground plane GND.
Further, the antenna device 1 includes a second passive element P2 that connects the middle of the adjustment element 4 and a base end side of the first passive element P1 of the open type antenna element 3, and a front end of the adjustment element 4 and an open type. The antenna element 3 includes at least one of the third passive element P3 that connects the front end side of the first passive element P1.

A fourth passive element P4 is connected between the first passive element P1 and the tip (antenna element AT) of the open antenna element 3.
The electrical length of the open antenna element 3 is set to 1 / 2λ (λ: wavelength) or more, but the fourth passive element P4 does not have to be at the center of the open antenna element 3, and the open antenna element 3 The overall electrical length is adjusted by setting the position based on the pattern width 3 and the distance from the ground plane GND.

The substrate body 2 is a general printed circuit board, and in this embodiment, a printed circuit board body made of a rectangular glass epoxy resin or the like is employed.
The antenna occupation area AOA is provided with a tip at one corner of the substrate body 2.
The ground plane GND is formed not only on the front surface of the substrate body 2 but also on the back surface, and is formed in a pattern with a space just below the antenna occupation area AOA on the front surface.
Note that an RF circuit component mounting area can be provided on the ground plane GND, and a plurality of components can be mounted.

For example, a core wire of a coaxial cable (not shown) connected to a high-frequency circuit is connected to the feed point FP, and the ground wire of the coaxial cable is connected to a nearby ground plane GND.
Note that the portion of the open antenna element 3 between the feed point FP and the first passive element P1 functions as a feed line, and may be set to an arbitrary length.

  In the open antenna element 3, the length d1 from the first passive element P1 to the tip of the antenna element AT (hereinafter simply referred to as the open element length d1) is longer in the direction toward the tip of the open antenna element 3. The shorter the shorter, the stronger the directivity of the open antenna element 3 in the proximal direction. That is, when the direction orthogonal to the extending direction of the open antenna element 3 is the X direction, the extending direction is the Y direction, and the direction orthogonal to the surface of the substrate body 2 is the Z direction, the open element length d1 is The longer the directivity in the 90 ° direction of the XY plane, the stronger the directivity in the 270 ° direction of the XY plane, the shorter the open element length d1.

  The antenna element AT is a loading element that does not self-resonate at a desired resonance frequency, and is a chip antenna in which a conductor pattern 22 such as Ag is formed on the surface of a dielectric 21 such as ceramics as shown in FIG. is there. The antenna element AT is installed along the extending direction of the open antenna element 3. The tip of the antenna element AT is bonded and connected to a land portion 3a that is patterned on the substrate body 1 with a metal foil such as a copper foil.

  Next, the result of analyzing the flow of high-frequency current in the antenna device 1 of the present embodiment by simulation will be described. In this analysis result, a distribution is obtained in which the electric field is concentrated in both directions on the antenna element AT side and the feeding point FP side, centering on the intermediate portion of the open antenna element 3 (around the fourth passive element P4). all right. That is, the electric field is concentrated in the antenna occupation area AOA, and the flow of high-frequency current to the ground plane GND side is suppressed.

  As described above, in the antenna device 1 of the present embodiment, the open antenna element 3 is provided with the feeding point FP on the base end side disposed near the ground plane GND on the end side of the antenna occupation area AOA and the antenna occupation area The first passive element P1 extending over substantially the entire length of the AOA and increasing the impedance on the base end side is connected in series, the adjustment element 4 is connected to the ground plane GND, and the open antenna element 3 and the open antenna element 3 and the first passive element P1 are connected to the ground plane GND via the adjustment element 4, so that the base end side is connected by the first passive element P1. The high-frequency current flowing through the ground plane GND with high impedance is suppressed, and the tip of the open antenna element 3 from the first passive element P1. The length at, it is possible to control the directivity. Accordingly, it is not necessary to separately stand an antenna element member on the substrate body, so that the thickness can be reduced and the antenna performance such as directivity and radiation efficiency can be achieved even in the case of the elongated antenna occupation area AOA extending in a strip shape. Can be improved.

  Further, since the antenna element AT of the dielectric antenna is connected to the tip of the open antenna element 3, the length of the open antenna element 3 can be shortened and the whole can be further downsized. The antenna element AT may be connected in the middle of the open antenna element 3. That is, in order to achieve both miniaturization and high performance, it is desirable to mount the antenna element AT at the tip as in this embodiment and to increase the impedance of the open end portion. Also, if you want to reduce the influence of peripheral parts with downsizing and high performance, mount the antenna element AT in the middle, increase the impedance of the middle part to increase the gain, and compared with the state without the antenna element, It is desirable to increase the impedance of the open end portion. By these effects, the electric field in the antenna occupation area AOA can be further concentrated, and the flow of high-frequency current to the ground plane GND side can be suppressed.

Further, the second passive element P2 connecting the middle of the adjustment element 4 and the proximal end side of the first passive element P1 of the open antenna element 3, the tip of the adjustment element 4, and the first of the open antenna element 3 Since the third passive element P3 that connects the tip side to the first passive element P1 is provided, the resonance frequency adjustment and the impedance adjustment can be flexibly performed by setting the second passive element P2 and the third passive element P3. .
Further, since the fourth passive element P4 is connected between the first passive element P1 and the tip of the open antenna element 3, the entire electrical length can be adjusted and resonance can be made by setting the fourth passive element P4. The frequency can be adjusted.

  Next, in the example produced based on the antenna device of the above embodiment, the results of measuring the VSWR characteristics and the radiation pattern will be described with reference to FIGS.

The antenna device of this embodiment has a substrate body size of 110 × 70 mm and an antenna occupation area size of 40 × 6 mm. The open element length d1 is 36.5 mm.
As each passive element, the first passive element P1 is a 19 nH inductor, the second passive element P2 is not mounted, the third passive element P3 is a 0.2 pF capacitor, and the fourth passive element P4 is a 1.0 nH inductor. is there.

  Further, the direction orthogonal to the extending direction of the open antenna element (the extending direction of the antenna occupying region) is defined as the X direction, and the direction along the extending direction of the open antenna element (the extending direction of the antenna occupying region) is defined. The Y direction was used, and the direction perpendicular to the surface of the substrate body was the Z direction. At this time, vertical polarization and power gain with respect to the XY plane were measured.

As can be seen from the VSWR characteristics shown in FIG. 6, good characteristics with a resonance frequency of 2420 MHz are obtained.
Further, as can be seen from the radiation pattern shown in FIG. 7, stronger directivity is obtained in the 90-degree direction (the direction toward the tip of the open antenna element) than in the 270-degree direction. The FB ratio in the figure indicates “90-degree direction strength / 270-degree direction strength”.

Next, FIG. 8 shows the result of analyzing the radiation pattern when the open element length is changed.
FIG. 8A shows a radiation pattern when the open element length d1 is 16.5 mm and the length of the antenna occupation region is 20 mm. FIG. 8B shows a radiation pattern when the open element length d1 is 26.5 mm and the length of the antenna occupation region is 30 mm.

  As a result, when the open element length d1 is short, as shown in FIG. 8A, the directivity is stronger in the 270 degree direction than in the 90 degree direction, and when the open element length d1 is long, As shown in (b), the 90 degree direction and the 270 degree direction showed the same directivity. Thus, directivity can be controlled by changing the length of the open element.

  In addition, this invention is not limited to the said embodiment and said Example, A various change can be added in the range which does not deviate from the meaning of this invention.

In the above embodiment, one antenna occupying region is provided at one corner of the substrate body and one antenna is provided. However, two antennas are provided by providing antenna occupying regions at two corners of the substrate body, respectively. May be provided. In this case, the two antennas can be set to obtain different directivities. For example, one antenna may be set to have directivity in the 90 degree direction, and the other antenna may be set to have directivity in the 270 degree direction.
Furthermore, in the above-described embodiment, the antenna occupation area is provided at the corner of the board body. However, the antenna occupation area may be provided at the center of one side of the board body.

  DESCRIPTION OF SYMBOLS 1 ... Antenna apparatus, 2 ... Board | substrate main body, 3 ... Open type antenna element, 4 ... Adjustment element, AT ... Antenna element, GND ... Ground surface, FP ... Feeding point, P1 ... 1st passive element, P2 ... 2nd passive Element, P3 ... third passive element, P4 ... fourth passive element

Claims (4)

An insulating substrate body;
A ground surface patterned with a metal foil on the substrate body;
An elongated antenna occupying region provided in contact with one side of the substrate body on the substrate body as an area where the ground plane is not formed and extending in a band shape along the one side;
An open antenna element patterned with a metal foil in the antenna occupation area;
An adjustment element that is patterned with a metal foil between the ground plane and the open antenna element and extends along the base end side of the open antenna element;
The open-type antenna element is provided with a feeding point on the base end side arranged near the ground plane on the end side of the antenna occupying area, and is extended by being patterned with a metal foil over substantially the entire length of the antenna occupying area. A first passive element that increases impedance on the proximal side is connected in series;
The adjustment element has a base end connected to the ground plane, and is connected to the open antenna element via a passive element,
The open antenna element and the first passive element are connected to the ground plane via the adjustment element ;
The open antenna element patterned with the metal foil extends to the vicinity of the end of the antenna occupying region on the side opposite to the feeding point,
The first passive element suppresses a high-frequency current flowing through the ground plane by setting a base end side of the open antenna element to a high impedance, and depends on a length from the first passive element to a tip of the open antenna element. An antenna device characterized by being an element that controls directivity . The antenna device according to claim 1,
An antenna device, wherein an antenna element of a dielectric antenna is connected to the middle or tip of the open antenna element. In the antenna device according to claim 1 or 2,
A second passive element that connects the middle of the adjustment element and a base end side of the open antenna element with respect to the first passive element; a distal end of the adjustment element; and the first passive element of the open antenna element. An antenna device comprising at least one of a third passive element that connects a tip side to an element. In the antenna device according to any one of claims 1 to 3,
4. An antenna device, wherein a fourth passive element is connected between the first passive element and the tip of the open antenna element.