JP2012182603A - Antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accommodate an antenna device to a compact and flat design of a communication device, ensuring satisfactory antenna performance in a state separated from a circuit board and connected thereto with a coaxial cable.SOLUTION: An antenna device 1 connected via a coaxial cable C to a circuit board 10 with a ground surface GND formed includes: an insulating substrate body 2; a ground pattern GP pattern-formed of metal foil on a circuit board side of the substrate body and connected with a ground wire of the coaxial cable; an open antenna pattern 3 pattern-formed of metal foil on the substrate body with a base end connected to the ground pattern and a tip end extended as an open end, and provided at the base end with an antenna side feeding point FP1 connected with a core wire of the coaxial cable; and a high frequency current control terminal 4 having a base end connected to the ground pattern and extended toward the circuit board and the other end connected to a substrate body side of the ground surface.

Description

  The present invention relates to an antenna device provided separately from a circuit board and connected by a coaxial cable.

  Conventionally, in a communication device such as a mobile phone, an antenna device provided in a non-antenna region of a circuit board is known. For example, in Patent Document 1, an antenna device is mounted in a non-ground region of a circuit board of a wireless communication device, and a radiation electrode or the like is provided in this region. That is, as shown in FIG. 10A, a ground plane GND and a non-ground region, which are ground regions, are formed on a circuit board 10 on which a high-frequency circuit is formed, and a radiation electrode or the like patterned in the non-ground region. Thus, the antenna device 101 is formed.

JP 2010-166287 A

However, the following problems remain in the above-described conventional technology.
That is, conventionally, as shown in FIG. 10A, the antenna device 101 is integrally formed on a large circuit board 10 on which a high-frequency circuit or the like is formed. As shown in FIG. 10B, in order to make the circuit board 10 small, the circuit board 10 and the antenna board 102 on which the antenna device 101 is formed may be separately designed and connected to each other via the coaxial cable C. It is being considered. In this case, an unstable element due to ground connection via the coaxial cable C occurs, and the performance of the antenna device 101 depends on the shape and mounting state of the circuit board 10 to be connected and the connection position with the circuit-side feeding point FP2 to be connected. There was a problem of being influenced. In particular, when the size of the ground plane GND of the circuit board 10 is reduced and the distance to the circuit-side feeding point FP2 is increased, there is a problem that the antenna performance is deteriorated. Furthermore, as shown in FIG. 10C, there is a disadvantage that the antenna performance is further deteriorated under use conditions in which the communication device 103 is in close contact with the human body or the metal M.

  The present invention has been made in view of the above-mentioned problems, and in a form provided separately from a circuit board and connected by a coaxial cable, good antenna performance can be obtained, and communication devices can be made smaller and thinner. An object of the present invention is to provide an antenna device that can cope with the above.

  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 is an antenna device connected to a circuit board on which a ground surface is formed via a coaxial cable, the insulating board body, and at least the circuit board side of the board body A pattern formed with a metal foil and a ground pattern to which the ground wire of the coaxial cable is connected, and a base end is connected to the ground pattern and a distal end side extends as an open end, and the substrate body is patterned with the metal foil. An open-type antenna pattern that is formed and provided with an antenna-side feeding point that is connected to the core of the coaxial cable on the base end side, and has a base end connected to the ground pattern and extends toward the circuit board The other end includes a high-frequency current control terminal connected to the substrate body side of the ground surface.

  This antenna device has a high-frequency current control terminal that is connected to the ground pattern and has a high-frequency current control terminal that extends toward the circuit board and has the other end connected to the substrate body side of the ground surface. The high-frequency current flowing from the substrate main body side to the opposite side of the ground surface to which the terminals are connected becomes dominant on the ground surface, and an effective high-frequency current flow viewed from the antenna device can be stably obtained. Therefore, the flow of high-frequency current in the board body can be flowed directly to the circuit board side via the high-frequency current control terminal, which can suppress unstable elements caused by coaxial cables and maximize antenna performance. become.

An antenna device according to a second invention is characterized in that, in the first invention, an insulating spacer is provided on the back surface of the substrate body.
That is, in this antenna device, since the insulating spacer is provided on the back surface of the substrate body, even when used in close contact with a human body or metal, the substrate body is separated from the human body or metal by the insulating spacer. The deterioration of performance can be suppressed, and the installation stability and strength can be improved.

In the antenna device according to a third aspect of the present invention, in the first or second aspect of the invention, the open antenna pattern includes an antenna element of a dielectric antenna on a tip side and a passive element in an intermediate portion. It is characterized by.
That is, in this antenna device, the open antenna pattern is provided with the antenna element of the dielectric antenna on the tip side and the passive element in the middle portion, so that it is shortened with respect to the wavelength of the desired resonance frequency. In addition, the antenna element of the dielectric antenna allows the open antenna pattern to be shortened and can be reduced in size, and the frequency adjustment and impedance adjustment can be performed by the passive element.

  An antenna device according to a fourth invention is the antenna device according to any one of the first to third inventions, wherein the open antenna pattern has a base end connected to the ground pattern and is opposite to the ground surface from the ground pattern. A first extension portion extending in a direction, a second extension portion having a base end connected to a tip end of the first extension portion and extending along a side of the ground surface facing the substrate body In addition, a base F is connected in the middle of the second extension portion, and the reverse F is configured by a third extension portion extending toward the ground pattern and provided with the antenna-side feeding point at the tip end. It is a type antenna pattern.

The present invention has the following effects.
That is, according to the antenna device of the present invention, the base end is connected to the ground pattern, the high frequency current control terminal is provided that extends toward the circuit board and the other end is connected to the board body side of the ground plane. Therefore, it is possible to suppress unstable elements due to the coaxial cable and to maximize the antenna performance.
Therefore, the antenna device of the present invention can save space and improve the degree of freedom of wiring and installation while maintaining good antenna performance, and can cope with downsizing and thinning of communication equipment.

1 is a plan view showing an antenna device connected to a circuit board in a first embodiment of an antenna device according to the present invention. The direction of the high-frequency current when there is no high-frequency current control terminal (a) and when it is close (b), and when the high-frequency current control terminal is long and the distance between the power supplies is long (c) It is a top view for demonstrating. 1 is a schematic cross-sectional view showing a case where a communication device equipped with an antenna device is used in close contact with a human body or metal in the first embodiment (a) and the second embodiment (b) of the antenna device according to the present invention. FIG. In other examples of the antenna device concerning a 2nd embodiment of the present invention, it is a schematic sectional view showing the case where it uses in the state where communication equipment carrying an antenna device was stuck to a human body or metal. In 3rd Embodiment of the antenna device which concerns on this invention, it is a top view which shows the antenna device connected to the circuit board. In 3rd Embodiment, it is a perspective view (a) which shows an antenna element, a top view (b), a front view (c), and a bottom view (d). It is a graph which shows the VSWR characteristic (voltage standing wave ratio) with the case where there is no high frequency current control terminal (a) and the case of 3rd Embodiment with a high frequency current control terminal (b). In the case where there is no high-frequency current control terminal, in the case of the third embodiment where the high-frequency current control terminal is arranged near the open end, and in the case of the third embodiment where the high-frequency current control terminal is arranged far from the open end, It is a graph which shows the result of having investigated the frequency bandwidth. In 1st Embodiment, it is a schematic sectional drawing which shows the other mounting form at the time of using the communication apparatus carrying an antenna apparatus in the state closely_contact | adhered to a human body or a metal. Schematic plan views (a) and (b) showing a conventional example and a reference example of an antenna device according to the present invention, and an explanation showing a case where a communication device having the antenna device mounted on a human body or metal is used in close contact This is shown in FIG.

  Hereinafter, a first embodiment of an antenna device according to the present invention will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the antenna device 1 according to the present embodiment is an antenna device connected to a circuit board 10 on which a ground plane GND is formed via a coaxial cable C, and includes an insulating substrate body 2, A ground pattern GP that is patterned with a metal foil on at least the circuit board 10 side of the substrate body 2 and connected to a ground wire (not shown) of the coaxial cable C, a base end is connected to the ground pattern GP, and a distal end side is connected to the ground pattern GP. An open antenna pattern 3 that extends as an open end, is patterned with a metal foil on the substrate body 2, and is provided with an antenna-side feed point FP1 to which a core wire (not shown) of the coaxial cable C is connected on the base end side; The base end of the ground pattern GP is connected to the circuit board 10 and the other end is connected to the substrate body 2 side of the ground plane GND. And a frequency current control terminal 4.

The board body 2 and the circuit board 10 are general printed boards, and in this embodiment, a printed board body made of a rectangular glass epoxy resin or the like is employed.
The ground pattern GP and the open antenna pattern 3 are formed with a copper foil or the like, for example.
The circuit board 10 is provided with a high-frequency circuit (not shown), and a ground plane GND is formed of a metal foil such as a copper foil on at least one surface.

  A ground wire (not shown) on one end side of the coaxial cable C is connected to the ground pattern GP, and a core wire (not shown) on the one end side of the coaxial cable C is connected to the antenna-side feeding point FP1. The ground wire (not shown) on the other end side of the coaxial cable C is connected to the ground plane GND, and the core wire (not shown) on the other end side of the coaxial cable C is a circuit of a high-frequency circuit on the circuit board 10 side. It is connected to the side feeding point FP2. The connection between the feeding points and the coaxial cable C may be performed via a connector such as a receptacle.

The open antenna pattern 3 includes a first extending portion 3a having a base end connected to the ground pattern GP and extending from the ground pattern GP in a direction opposite to the ground plane GND, and the first extending portion 3a. A base end is connected to the front end of the second extended portion 3b and extends along the side of the ground plane GND facing the substrate body 2, and a base end is connected to the middle of the second extended portion 3b. And an inverted F-type antenna pattern composed of a third extending portion 3c extending toward the ground pattern GP and provided with an antenna-side feeding point FP1 at the tip.
The high-frequency current control terminal 4 is a short pin such as a metal rod or copper plate, and is made of a material that allows a high-frequency current to flow with a low impedance in a desired frequency band.

Next, the flow of high-frequency current in the antenna device of this embodiment will be described with reference to FIG.
When the antenna device and the circuit board 10 are provided separately and connected by the coaxial cable C, the high-frequency current flowing through the coaxial cable C is greatly influenced by the design conditions such as the length of the coaxial cable C and the routing. Unstable elements are large. For example, as shown in FIG. 2A, when the high-frequency current control terminal 4 is not provided and the distance between the feeding points is long, the unstable high-frequency current 5A by the coaxial cable C and the effective high-frequency current 5C as viewed from the antenna device On the other hand, the high-frequency current 5B flowing in the opposite direction becomes dominant, and the antenna performance deteriorates.

Further, as shown in FIG. 2B, when the high-frequency current control terminal 4 is not provided and the distance between the feeding points is short, the unstable high-frequency current 5A by the coaxial cable C becomes dominant, and the antenna performance is also deteriorated. End up.
On the other hand, in the antenna device 1 of the present embodiment, the high-frequency current control terminal 4 is provided so that the flow of the high-frequency current in the substrate body 2 is also applied to the circuit board 10 side as shown in FIG. The high-frequency current 5C can be directly flown, and unstable elements due to the coaxial cable C can be suppressed and the antenna performance can be maximized.

Each design condition in the antenna apparatus 1 of this embodiment is demonstrated below.
<Ground conditions>
The ground pattern GP in the substrate body 2 may be small. However, as an ideal condition, it is desirable that the area is large and the circuit pattern 10 is long. Further, it is desirable that the length at that time is a quarter or more of the wavelength of the desired frequency band.
<Feeding point>
The positional relationship between the high-frequency current control terminal 4 and the antenna-side feeding point FP1 may be arbitrary, but as an ideal condition, the antenna-side feeding point FP1 is disposed far from the open end of the open antenna pattern 3, and the antenna-side feeding point Desirably, the high-frequency current control terminal 4 is disposed in the vicinity of the point FP1.

<Open antenna pattern>
In this embodiment, the open antenna pattern 3 employs an inverted F antenna pattern, but other open antenna patterns such as an inverted L antenna pattern may be used.
The open antenna pattern 3 may be double-resonant (two resonances, three resonances). In that case, it is desirable to set the high frequency current control terminal 4 for the open end of the lowest frequency band.

  As described above, in the antenna device 1 according to the present embodiment, the base end is connected to the ground pattern GP and extends toward the circuit board 10, and the other end is connected to the substrate body 2 side of the ground plane GND. Since the control terminal 4 is provided, the high-frequency current 5C that flows from the substrate main body 2 side to the opposite side of the ground plane GND to which the high-frequency current control terminal 4 is connected becomes dominant on the ground plane GND. In addition, an effective high-frequency current flow can be obtained stably. Therefore, the flow of the high-frequency current 5 in the board body 2 can be directly flowed to the circuit board 10 side via the high-frequency current control terminal 4, and unstable elements due to the coaxial cable C are suppressed, and the antenna performance is maximized. It becomes possible to pull out.

  Next, a second embodiment and a third embodiment of the antenna device according to the present invention will be described below with reference to FIGS. Note that, in the following description of the embodiment, the same components described in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The difference between the second embodiment and the first embodiment is that, in the first embodiment, as shown in FIG. 3A, the antenna device 1 and the circuit board 10 are installed on the same plane. In some cases, the antenna device 21 of the second embodiment is used in close contact with a human body or a metal M. As shown in FIG. 3B, an insulating spacer 22 is provided on the back surface of the substrate body 2. Even when the communication device is used in close contact with the human body or the metal M, the board main body 2 can be set apart from the human body or the metal M.

  The insulating spacer 22 is formed in a rectangular parallelepiped shape with an insulating sponge material such as polyethylene. The insulating spacer 22 desirably has a low dielectric constant in a desired frequency band. The insulating spacer 22 and the substrate body 2 may be bonded with a double-sided tape or a general adhesive. It is desirable that the bonding position of the insulating spacer 22 is a position that does not overlap the open end of the open antenna pattern 3 and the antenna side feeding point FP1 (a position that is not directly below). Further, since the board body 2 and the circuit board 10 have different height positions, the high-frequency current control terminal 4 extends and is connected in the height direction (board thickness direction).

  Thus, in the antenna device 21 of the second embodiment, since the insulating spacer 22 is provided on the back surface of the substrate body 2, the insulating spacer is used even when the communication device is used in close contact with the human body or the metal M. Since the substrate main body 2 is separated from the human body and the metal M by 22, it is possible to suppress the deterioration of the antenna performance and improve the installation stability and strength.

  Although it is preferable from the viewpoint of installation stability and strength that the antenna device 21 is separated from the human body and the metal M by the insulating spacer 22 as in the second embodiment, as another example, as shown in FIG. The antenna device 1 may be separated from the human body or the metal M by supporting the substrate body 2 on the circuit substrate 10 by the high-frequency current control terminal 4 without the insulating spacer 22. In this case, air is interposed in the space between the board body 2 and the human body or the metal M instead of the spacer, and the board body 2 and the human body or the metal M are separated from each other, so that deterioration of the antenna performance can be suppressed. .

  Next, the difference between the third embodiment and the first embodiment is that, in the first embodiment, the open antenna pattern 3 is only formed by a patterned metal foil, whereas the third embodiment is different from the third embodiment. In the antenna device 31, as shown in FIG. 5, the open antenna pattern 33 includes a dielectric antenna antenna element ANT on the tip side, and a first passive element P <b> 1 and a second passive element P <b> 2 in the middle part. It is a point that has.

  That is, in the second embodiment, the ground pattern GP is formed on the end side of the substrate body 2, and the open antenna pattern 33 is connected to the ground pattern GP at the base end and is opposed to the ground pattern GP. A first extending portion 33a extending in a direction along one side of the surface GND (long side direction of the substrate body 2), a first passive element P1 connected in the middle of the first extending portion 33a, and a first extending portion The base end of the antenna element ANT connected to the tip of the existing portion 33a is connected to the middle of the first extending portion 33a, extends toward the ground plane GND, and is bent in the middle to be connected to the ground pattern GP. It is comprised from the 2nd extension part 33b and the 2nd passive element P2 connected to the middle of this 2nd extension part 33b.

  The antenna element ANT is a loading element that does not self-resonate at a desired resonance frequency. For example, as shown in FIG. 6, the antenna element ANT is a chip antenna in which a conductor pattern 122 such as Ag is formed on the surface of a dielectric 121 such as ceramics. is there. As the antenna element ANT, elements having different lengths, widths, conductor patterns 122, etc. may be selected according to the setting of the resonance frequency or the like, and the same element may be selected.

For example, an inductor, a capacitor, or a resistor is used for the first passive element P1 and the second passive element P2.
That is, in this antenna device 31, the open antenna pattern 33 includes the antenna element ANT of the dielectric antenna on the tip side, and includes the first passive element P1 and the second passive element P2 in the middle portion. The antenna element ANT of the dielectric antenna shortened with respect to the wavelength of the desired resonance frequency enables the open antenna pattern 33 to be shortened and downsized, and the first passive element P1 and the second passive element. P2 enables frequency adjustment and impedance adjustment.

  Next, in the antenna device 31 of the third embodiment, the results of measuring the VSWR characteristics (voltage standing wave ratio) when the high frequency current control terminal 4 is not provided and when the high frequency current control terminal 4 is provided are shown in FIG. (A) and (b). In the measurement of FIG. 7A, an inductor with L = 47 nH was used as the first passive element P1, and an inductor with L = 10 nH was used as the second passive element P2. In the measurement of FIG. 7B, an inductor of L = 37 nH was used as the first passive element P1, and an inductor of L = 15 nH was used as the second passive element P2.

  As can be seen from this measurement result, in the case where there is no high-frequency current control terminal 4, as shown in FIG. 7A, the bandwidth is narrow and the antenna performance is deteriorated due to adverse effects and unstable factors of the high-frequency current. On the other hand, in the case where the high-frequency current control terminal 4 is provided, as shown in FIG. 7B, unstable elements due to ground connection via the coaxial cable C are suppressed, and the antenna performance is improved (broadband). Is realized.

  Next, FIG. 8 shows the result of examining the change in the frequency bandwidth when the arrangement of the high-frequency current control terminal 4 is changed. In this measurement, based on the case where there is no high-frequency current control terminal 4 (the leftmost data “present invention: none” in the graph of FIG. 8), the high-frequency current control terminal 4 is in the vicinity of the open end of the open antenna pattern 33 (substrate 8 (center of the main body 2) (in the graph of FIG. 8, the center data “present invention: arrangement near the open / closed end”), the high-frequency current control terminal 4 is far from the open end of the open antenna pattern 33. In the case of being arranged at the (end of the substrate body 2) (in the graph of FIG. 8, the data at the right end “present invention: disposition at the presence / absence of the open end”) was examined.

As can be seen from the measurement results, in the present embodiment in which the high-frequency current control terminal 4 is not provided and the high-frequency current control terminal 4 is provided, the bandwidth is widened. In particular, the high-frequency current control terminal 4 is open. When the antenna pattern 33 is disposed far from the open end of the pattern antenna pattern 33, the improvement is 2.2 times.
In addition, as long as the open antenna pattern 33 is arranged far from the open end, the high-frequency current control terminal 4 having a narrow line that can be connected may be used. However, when the open antenna pattern 33 is arranged near the open end of the open antenna pattern 33 By making it thicker or wider in the direction away from the open end, the ground contact area is expanded, and the antenna performance improvement effect can be further obtained.

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

  For example, as described above, in the first embodiment, as shown in FIG. 3A, the antenna device 1 and the circuit board 10 are installed on the same plane and are in close contact with the human body or the metal M. However, in order to separate the antenna device from the human body and the metal M as in the second embodiment, the circuit boards 10A and 10B are stacked in two stages by the pillar parts 32 and separated from the human body and the metal M as shown in FIG. The high frequency current control terminal 4 may be connected to the upper circuit board 10A, and the antenna device 1 may be supported by the upper circuit board 10A while being separated from the human body or the metal M. By fixing the antenna device 1 to the upper part of the circuit board laminated in a plurality of stages as described above, the antenna device 1 can be separated from the human body or the metal M without the insulating spacer 22 to reduce the influence thereof. it can.

  1, 2, 31 ... Antenna device, 2 ... Substrate body, 3 ... Open antenna pattern, 3a, 33a ... 1st extension part, 3b, 33b ... 2nd extension part, 3c ... 3rd extension part, 4 ... high frequency current control terminal 10, 10A, 10B ... circuit board, 22 ... insulating spacer, ANT ... antenna element, C ... coaxial cable, GND ... ground plane, GP ... ground pattern, FP1 ... antenna side feeding point, FP2 ... Circuit-side feed point, P1 ... first passive element, P2 ... second passive element

Claims (4)

An antenna device connected to a circuit board on which a ground plane is formed via a coaxial cable,
An insulating substrate body;
A ground pattern that is patterned with a metal foil on at least the circuit board side of the substrate body and to which the ground wire of the coaxial cable is connected;
An antenna-side feeding point having a base end connected to the ground pattern and a tip end extending as an open end and patterned with a metal foil on the substrate body, and a core wire of the coaxial cable connected to the base end side An open antenna pattern provided;
A base end is connected to the ground pattern and includes a high-frequency current control terminal that extends toward the circuit board and has the other end connected to the substrate body side of the ground surface. Antenna device. The antenna device according to claim 1,
An antenna device, wherein an insulating spacer is provided on a back surface of the substrate body. The antenna device according to claim 1 or 2,
The open antenna pattern is provided with an antenna element of a dielectric antenna on the front end side and a passive element in an intermediate part. In the antenna device according to any one of claims 1 to 3,
The open-type antenna pattern has a base end connected to the ground pattern and extends from the ground pattern in a direction opposite to the ground plane, and at a tip of the first extension portion. A base end is connected and the second extending portion extends along the side of the ground surface facing the substrate body, and a base end is connected in the middle of the second extending portion and the ground pattern An antenna device, wherein the antenna device is an inverted F-type antenna pattern including a third extending portion extending toward the top and provided with the antenna-side feeding point at a tip thereof.