JPWO2012077406A1 - Antenna device - Google Patents

Abstract

The communication module (101) includes a module substrate (20), antenna elements (21, 22) provided on the module substrate (20), a shield case (23) for shielding a communication circuit provided on the module substrate (20), And a conductor (24). A first antenna element (21) and a second antenna element (22) are formed on the upper surface of the non-ground region (NGA) at the end of the module substrate (20). The conductor (24) is a metal plate connected in the vicinity of the end of the ground region (GA) on the lower surface of the module substrate (20), and protrudes so as to extend in a direction perpendicular to the module substrate (20). Yes. The conductor (24) has a length (height) dimension of about a quarter wavelength of the desired frequency. With this configuration, an antenna device is configured that improves the gain of vertical polarization in the plane direction of the substrate and increases the overall sensitivity.

Description

  The present invention relates to an antenna device, and more particularly to an antenna device used in wireless communication between devices, a wireless LAN, a mobile communication system, and the like.

  Patent Documents 1 and 2 disclose antenna devices configured for the purpose of improving directivity and gain in antennas used in wireless devices such as portable terminals.

  An example of the antenna device of Patent Document 1 is shown in FIG. In FIG. 1, an antenna device 10 includes an antenna body 13 having a conductor 11 and a feeding electrode 12 to which one end of the conductor 11 is connected, a power supply 14 to which the feeding electrode 12 is connected, and a conductive surface. It consists of a mounting substrate 17 having a linear conductor pattern 15 and a substantially rectangular ground electrode 16 formed by printing a material. The antenna body 13 and the power supply 14 are mounted on a mounting board 17, and the power feeding electrode 12 and the power supply 14 of the antenna body 13 are connected via a conductor pattern 15 on the surface of the mounting board 17. Here, the ground electrode 16 on the surface of the mounting substrate 17 serves as a ground portion that resonates with the antenna body 13.

  An example of the antenna device of Patent Document 2 is shown in FIG. In FIG. 2, the board 2 on which the radio circuit 10 is mounted, the built-in antenna 3 having a feeding point on the first conductor plate 1 provided on the board 2, and the second side different from the surface on which the built-in antenna 3 is arranged. The first conductor plate 1 is disposed on the first conductor plate 1, and a second conductor plate 5 having a ground side 4 that is grounded. Since the second conductor plate 5 is provided, the phase difference between the current on the first conductor plate 1 and the current on the second conductor plate 5 is increased, so that radiation from the first conductor plate 1 is performed. And the radiation from the second conductor plate 5 strengthen each other. As a result, the gain on the side where the second conductor plate 5 exists is higher than that in the case where the second conductor plate 5 is not provided, and a radiation pattern close to non-directionality is obtained.

Japanese Patent Laid-Open No. 11-195917 JP 2007-81712 A

In the antenna device having the configuration shown in FIG. 1, horizontal polarization is obtained in the plane direction of the substrate, but the vertical polarization component in that direction is small.
In the antenna apparatus having the configuration shown in FIG. 2, the provision of the second conductor plate 5 improves the vertical polarization gain in the plane direction of the substrate. Therefore, the gain of the vertically polarized wave in the horizontal plane in the installation direction of the built-in antenna 3 is not improved.

  For example, a wireless LAN antenna using MIMO (Multiple Input Multiple Output) technology may require vertical polarization and forward gain in a horizontal plane. However, in any of the configurations of FIGS. 1 and 2, when these antenna devices are incorporated into a set with the substrate surface facing the horizontal plane, there is a tendency that the problem of small gain of vertical polarization in the horizontal plane occurs. It is in.

  Accordingly, an object of the present invention is to provide an antenna device capable of improving the gain of vertical polarization in the surface direction of the substrate and enhancing the overall sensitivity.

In order to solve the above problems, the antenna device of the present invention is configured as follows.
(1) A substrate provided with a non-ground region at an end thereof and an antenna element (pattern or chip) provided in the non-ground region, connected to the ground of the substrate and perpendicular to the substrate A feature is that an extending plate-like conductor is provided.

(2) The extending length of the conductor corresponds to, for example, approximately ¼ wavelength at the resonance frequency of the antenna element.

(3) When the board includes a wireless communication circuit and a shield plate that covers the wireless communication circuit, a part of the shield plate may be used as the conductor.

(4) To that end, for example, the substrate may be provided with a slit hole that penetrates a part of the shield plate, and a part of the shield plate may protrude from the surface opposite to the surface on which the antenna element is formed. .

(5) A conductor surface is provided at a position away from the conductor in a direction opposite to the position of the antenna element, and the conductor surface is a housing (chassis or frame) that fixes the substrate. Good.

(6) When the antenna element includes a first antenna element and a second antenna element, the conductor may be provided only on the second antenna element side without being provided on the first antenna element side.

  According to the present invention, it is possible to improve the gain of vertical polarization in the surface direction of the substrate and enhance the overall sensitivity. Therefore, for example, it can be applied to a wireless LAN antenna using a MIMO system that requires a forward gain in a horizontal plane.

FIG. 1 is a diagram illustrating an example of an antenna device disclosed in Patent Document 1. In FIG. FIG. 2 is a diagram illustrating an example of the antenna device of Patent Document 2. In FIG. 3A and 3B are external perspective views of the communication module 101 including the antenna device according to the first embodiment, and FIG. 3C is a bottom view thereof. FIG. 4 is a diagram showing the directivity patterns of horizontal polarization and vertical polarization in the horizontal plane for 2.44 GHz. 4A shows the case of the first embodiment, and FIG. 4B shows the case where no conductor is provided in the first embodiment. FIG. 5 is a diagram showing the directivity patterns of horizontal polarization and vertical polarization in the horizontal plane for 5.6 GHz. FIG. 5A shows the case of the first embodiment, and FIG. 5B shows the case where no conductor is provided in the first embodiment. FIG. 6 is a diagram showing the pass characteristic and the return loss characteristic by simulation of the communication module 101. FIG. 7 is a diagram in which a current intensity pattern is added to the front view of the communication module 101. FIG. 8 is a diagram showing a change in gain of the first antenna element 21 when the width W of the conductor 24 is fixed to 50 mm and the length L is changed from 0 to 35 mm. FIG. 9A is a plan view of the communication module 102 including the antenna device according to the second embodiment, and FIG. 9B is a front view thereof. FIG. 10 is a front view of the communication module 103 including the antenna device according to the third embodiment. FIG. 11 shows a change in gain in the horizontal plane when the length L of the conductor 24 is fixed to 13.5 mm corresponding to a quarter wavelength at 5.6 GHz and the width W is changed from 0 to 50 mm. FIG. FIG. 11A is a characteristic diagram of the first antenna element 21, and FIG. 11B is a characteristic diagram of the second antenna element 22. FIG. 12 is a side view of the communication module 104 including the antenna device according to the fourth embodiment. 13A is a perspective view of a main part of an electronic device provided with the communication module 104, and FIG. 13B is a perspective view of a main part of the electronic device provided with a communication module as a comparative example. 14A shows the current flowing through the module fixing metal plate 26 and the conductor 24 shown in FIG. 13A, and FIG. 14B shows the current flowing through the module fixing metal plate 26 shown in FIG. 13B. FIG. FIG. 15 is a diagram illustrating S parameters of the antenna device according to the fourth embodiment and an antenna device which is a comparative example. 15A shows reflection characteristics (S11), FIG. 15B shows transmission characteristics (S21), and FIG. 15C shows reflection characteristics (S22). FIG. 16 shows the result of obtaining the amount of gain improvement in the horizontal plane due to the presence of the conductor 24 by simulation, FIG. 16A shows the amount of gain improvement of vertical polarization in the horizontal plane by the conductor 24, and FIG. 24 shows the amount of gain improvement of horizontal polarization in the horizontal plane. FIG. 17 is an actual measurement result of the gain improvement amount in the horizontal plane due to the provision of the conductor 24, FIG. 17A is the gain improvement amount of vertical polarization in the horizontal plane by the conductor 24, and FIG. Shows the amount of gain improvement of horizontal polarization in the horizontal plane. FIG. 18 is a diagram showing the gain improvement amount of vertical polarization in the horizontal plane in simulation and actual measurement for the 5.6 GHz band.

<< First Embodiment >>
An antenna device according to a first embodiment and a communication module including the antenna device will be described with reference to the drawings.
3A and 3B are external perspective views of the communication module 101 including the antenna device according to the first embodiment, and FIG. 3C is a bottom view thereof. FIG. 3A and FIG. 3B differ in the viewpoint position where the communication module 101 is viewed.

  The communication module 101 includes a module substrate 20, antenna elements 21 and 22 provided on the module substrate 20, a shield case 23 that shields a communication circuit provided on the module substrate 20, and a conductor 24.

  The module substrate 20 includes a region (ground region) GA where a ground electrode is formed and a region (non-ground region) NGA where a ground electrode is not formed. The end portion of the module substrate 20 is a non-ground region NGA on both the upper and lower surfaces, and a first antenna element 21 and a second antenna element 22 are formed on the upper surface of the non-ground region NGA by electrode patterns, respectively. The electrode patterns of these antenna elements 21 and 22 are bilaterally symmetric and are formed on the module substrate 20 as far as possible from each other. The antenna elements 21 and 22 are single-point feed dual antenna elements that resonate in the 2.4 GHz band and the 5 GHz band, respectively.

  The conductor 24 is, for example, a metal plate connected to the vicinity of the end of the ground region (GA) on the lower surface of the module substrate 20, and protrudes so as to extend in the vertical direction with respect to the module substrate 20. The module substrate 20 is, for example, a 50 mm square substrate, and the conductor 24 has a width of 50 mm and a length (height) of about 1/4 wavelength of a desired frequency. When matching to 5.6 GHz, it is about 13.5 mm which is a quarter wavelength thereof.

  FIG. 4 shows an example of the directivity pattern of horizontal polarization and vertical polarization in the horizontal plane for 2.44 GHz. 4A shows the characteristics of the antenna device of the first embodiment, and FIG. 4B shows the characteristics of the antenna device in which the conductor 24 is not provided in the configuration shown in FIG. FIG. 5 shows an example of directivity patterns of horizontal polarization and vertical polarization on a horizontal plane for 5.6 GHz. FIG. 5A shows the characteristics of the antenna device of the first embodiment, and FIG. 5B shows the characteristics of the antenna device in which the conductor 24 is not provided in the configuration shown in FIG. These patterns are directivity patterns in the direction shown in FIG. 3C (viewed from the back side of the substrate).

Here, the meaning of each curve is as follows.
Etheta1: Gain of vertical polarization in the horizontal plane of the first antenna element 21
Etheta2: vertical polarization gain in the horizontal plane of the second antenna element 22
Ephi1: Horizontal polarization gain in the horizontal plane of the first antenna element 21
Ephi2: Gain of horizontal polarization in the horizontal plane of the second antenna element 22 Here, “in the horizontal plane” means “a plane including the substrate surface”.

  Further, an azimuth angle of 90 degrees on the horizontal plane corresponds to the front shown in FIGS. 3 (A) and 3 (B). Since the electrode patterns of the first antenna element 21 and the second antenna element 22 are symmetrical, the directivity pattern is symmetrical with respect to a line connecting 90 degrees and 270 degrees.

  First, considering 2.44 GHz, as is apparent from a comparison between FIG. 4A and FIG. 4B, by providing the conductor 24, the first antenna element 21 and the second antenna element 22 are perpendicular to each other. The gain for the polarization is improved from -25 dB to -14 dB in the forward direction (90-degree direction).

  Regardless of the presence or absence of the conductor 24, the gain for horizontal polarization in the horizontal plane hardly changes. That is, the gain of horizontal polarization does not decrease.

  Next, considering 5.6 GHz, as is clear from a comparison between FIG. 5A and FIG. 5B, by providing the conductor 24, the horizontal plane of the first antenna element 21 and the second antenna element 22 is provided. The gain with respect to the vertical polarization is improved from -30 dB to about -5 dB in the forward direction (90-degree direction) and the backward direction (270-degree direction).

  Even at 5.6 GHz, regardless of the presence or absence of the conductor 24, the gain for horizontally polarized waves in the horizontal plane does not decrease.

  FIG. 6 is a diagram showing the pass characteristic and the return loss characteristic by simulation of the communication module 101. In FIG. 6, S11A is the reflection characteristic of the antenna device (S parameter S11 characteristic) in the communication module 101 of the first embodiment, and S11B is the reflection characteristic of the antenna device not provided with the conductor 24 (S parameter S11 characteristic). It is. Further, S21A is a transmission characteristic (S21 characteristic of S parameter) of the antenna device in the communication module 101 of the first embodiment, and S21B is a transmission characteristic (S21 characteristic of S parameter) of the antenna apparatus not provided with the conductor 24. . The S22 characteristic is the same as the S11 characteristic because the antenna is designed symmetrically.

  As can be seen from FIG. 6, by providing the conductor (metal plate), the distribution of the current flowing through the GND changes and the S parameter changes.

  Each of the above characteristic improvement principles can be explained as follows. FIG. 7 is a diagram in which a current distribution is added to the front view of the communication module 101. In the ground region GA of the module substrate 20, the current distribution is distributed by a quarter wavelength with the length in the horizontal direction in FIG. 7. The conductor 24 resonates at a quarter wavelength, and the conductor 24 has a current distribution corresponding to a quarter wavelength with a length in the vertical direction in FIG. That is, a standing wave corresponding to ¼ wavelength is generated, and the conductor 24 acts as a radiating element to generate a vertical current. As a result, a vertical polarization component in the horizontal plane is generated.

FIG. 8 is a diagram showing a change in gain in the horizontal plane of the first antenna element 21 when the width W of the conductor 24 is fixed to 50 mm and the length L is changed from 0 to 35 mm. The vertical axis represents the average gain over the entire 360 degrees, and the horizontal axis represents the length L of the conductor 24. Here, the meaning of each curve is as follows.
Etheta (2.44): Vertical polarization gain in the horizontal plane at 2.44 GHz
Etheta (5.6): Vertical polarization gain in the horizontal plane at 5.6 GHz
Ephi (2.44): Horizontal polarization gain in the horizontal plane at 2.44 GHz
Ephi (5.6): Gain of horizontal polarization in the horizontal plane at 5.6 GHz As is clear from FIG. 8, as the length L of the conductor 24 increases, the gain of vertical polarization in the horizontal plane increases. The gain improvement of vertical polarization is saturated at about 30 mm corresponding to the quarter wavelength at 2.44 GHz, and is saturated at about 13.5 mm corresponding to the quarter wavelength at 5.6 GHz. The gain of horizontal polarization in the horizontal plane is hardly affected by the length L of the conductor 24.

  The antenna element installed in the non-ground region may be mounted with a chip antenna other than being formed with an electrode pattern. The same applies to the embodiments described below.

<< Second Embodiment >>
FIG. 9A is a plan view of the communication module 102 including the antenna device according to the second embodiment, and FIG. 9B is a front view thereof. In this example, a slit-like through hole 25 is formed in the module substrate 20 so that a part of the shield case 23 penetrates the through hole 25. A part of this shield case is provided as a conductor 24. The first antenna element 21 and the second antenna element 22 are chip antennas, and these chip antennas are mounted on the non-ground region NGA of the module substrate.

  According to this configuration, it is not necessary to provide the conductor 24 as an individual component, and the number of components can be reduced.

<< Third Embodiment >>
FIG. 10 is a front view of the communication module 103 including the antenna device according to the third embodiment. In the third embodiment, changes in the gains of the first antenna element 21 and the second antenna element 22 when the width W of the conductor 24 is changed will be described.

FIG. 11 is a diagram showing a change in gain in the horizontal plane when the length L of the conductor 24 is fixed to 13.5 mm corresponding to a quarter wavelength at 5.6 GHz and the width W is changed from 0 to 50 mm. It is. The vertical axis represents the average gain over the entire 360 degrees, and the horizontal axis represents the width W of the conductor 24. FIG. 11A shows the characteristics of the first antenna element 21, and FIG. 11B shows the characteristics of the second antenna element 22. Here, the meaning of each curve is as follows as in the case of FIG.
Etheta (2.44): Vertical polarization gain in the horizontal plane at 2.44 GHz
Etheta (5.6): Vertical polarization gain in the horizontal plane at 5.6 GHz
Ephi (2.44): Horizontal polarization gain in the horizontal plane at 2.44 GHz
Ephi (5.6): Gain of horizontal polarization in the horizontal plane at 5.6 GHz As is clear from FIGS. 11A and 11B, if the width W of the conductor 24 is 1 mm, it is in the horizontal plane at 5.6 GHz. The gain of vertical polarization increases rapidly. Since the conductor 24 exists on the second antenna element 22 side, the gain improvement effect of vertical polarization in the horizontal plane of the second antenna element 22 is higher than that of the first antenna element 21. As for the second antenna element 22, when the width W of the conductor 24 exceeds 25 mm (half width), the gain of vertical polarization in the horizontal plane becomes constant. For the first antenna element 21, the gain of vertical polarization in the horizontal plane improves as W increases.

  From these facts, by making the length L of the conductor 24 a length corresponding to a quarter wavelength of the operating frequency, an effect of improving the gain of vertical polarization in the horizontal plane can be obtained almost without depending on the width W. I understand.

  Therefore, for example, in order to increase the gain of the vertically polarized wave in the horizontal plane at 2.44 GHz of the second antenna element 22 from the first antenna element 21, a conductor may be disposed only in the vicinity of the second antenna element 22.

  In this way, by providing a conductor only at a position close to one of the two antenna elements having the same configuration, the vertically polarized wave in the horizontal plane of the antenna element on the side where the conductor is arranged and the horizontal plane of the other antenna element are arranged. Since the plane of polarization with the horizontal polarization is orthogonal, the mutual coupling between the two antenna elements is improved. In addition, the directivity of the antenna element with the conductor close to the other antenna element is not similar to the directivity of the other antenna element (the correlation coefficient is small), so the communication capacity may be improved.

<< Fourth Embodiment >>
In the fourth embodiment, characteristics of the antenna device in a state where the communication module shown in the first and second embodiments is incorporated in an electronic device will be described.
FIG. 12 is a side view of the communication module 104 including the antenna device according to the fourth embodiment. FIG. 13A is a perspective view of a main part of an electronic device including the communication module 104. FIG. 13B is a perspective view of a main part of an electronic device including a communication module as a comparative example.

  The communication module 104 is attached to the module fixing metal plate 26 of the electronic device to be assembled by screwing or the like. The module fixing metal plate 26 is also a part of the casing 27 of the electronic device.

  As apparent from FIGS. 12 and 13, some conductors such as the module fixing metal plate 26 exist in the state where the communication module is incorporated in the electronic device. By arranging the conductor 24 of the antenna device in front (outside) of the antenna 26, the gain of vertical polarization in the horizontal plane is also improved.

  14A shows the current flowing through the module fixing metal plate 26 and the conductor 24 shown in FIG. 13A, and FIG. 14B shows the current flowing through the module fixing metal plate 26 shown in FIG. 13B. FIG. As shown in FIGS. 14A and 14B, by providing the conductor 24, the current flowing through the conductor 24 increases. Conversely, the current flowing through the module fixing metal plate 26 decreases. However, since the direction of the current in the vertical direction of the module fixing metal plate 26 and the direction of the current in the conductor 24 are aligned, the gain of vertical polarization mainly in the horizontal plane in the forward direction is improved.

  FIG. 15 is a diagram illustrating S parameters of the antenna device according to the fourth embodiment and an antenna device which is a comparative example. 15A shows reflection characteristics (S11), FIG. 15B shows transmission characteristics (S21), and FIG. 15C shows reflection characteristics (S22). In these drawings, the characteristic of the antenna according to the fourth embodiment is represented by α, and the characteristic of the antenna device of the comparative example is represented by β.

  As is apparent from FIG. 15, by providing the conductor surface (metal plate), it can be seen that the current distribution flowing through the GND changes and the S parameter changes.

  FIG. 16 shows the result of obtaining the amount of gain improvement in the horizontal plane due to the presence of the conductor 24 by simulation. 16A shows the amount of gain improvement in vertical polarization in the horizontal plane by the conductor 24, and FIG. 16B shows the amount of gain improvement in horizontal polarization in the horizontal plane by the conductor 24. FIG. 17 is an actual measurement result of the gain improvement amount in the horizontal plane due to the provision of the conductor 24, FIG. 17A is the gain improvement amount of vertical polarization in the horizontal plane by the conductor 24, and FIG. The amount of gain improvement of horizontal polarization in the horizontal plane by the conductor 24 is shown.

  In both figures, “Ave Gain” is an average value over the entire 360 degrees, and “Front Ave Gain” is an average value in the range of 180 degrees forward from 0 degrees to 180 degrees. Also, # 1 represents the characteristics of the first antenna element, and # 2 represents the characteristics of the second antenna element.

As is clear from FIGS. 16A and 17A, both the first antenna element 21 and the second antenna element 22 are improved by about 2 dB at 5.6 GHz. With respect to 2.44 GHz, according to the simulation, as shown in FIG. 16A, the gain of the vertically polarized wave in the horizontal plane of the second antenna element 22 decreases by about −4 dB. This is because the current flowing in the casing 27 adjacent to the second antenna element 22 is in a phase opposite to that of the current flowing in the conductor 24. However, since the average gain of vertically polarized waves in the horizontal plane of 2.44 GHz is as low as −20 dB or less, the influence is small. That is, it cannot be said that the value of the gain changes substantially even if the gain on the order of −20 dBi becomes −24 dBi. Therefore, the deterioration of the vertical polarization gain in the horizontal plane is small and can be ignored. Moreover, the deterioration of the gain of vertical polarization in the horizontal plane can be improved by adjusting the mounting position of the communication module. According to the actual measurement, the gain decrease is small as shown in FIG. (In the 2.4 GHz band, the current directions of the conductor 24 and the module fixing metal plate 26 are reversed.)
FIG. 18 summarizes the gain improvement amount of vertical polarization in the horizontal plane in the simulation and actual measurement for the 5.6 GHz band. Here, “Ave (omnidirectional)” is an average value over 360 degrees, and “Ave (forward)” is an average value in the range of 180 degrees forward from 0 degrees to 180 degrees. Also, # 1 represents the characteristics of the first antenna element, and # 2 represents the characteristics of the second antenna element.

  Thus, by making the length of the conductor 24 in accordance with the 5.6 GHz band, the gain of vertical polarization in the horizontal plane is reliably improved.

<< Other embodiments >>
In the first to fourth embodiments, the conductor 24 protrudes from the surface of the substrate opposite to the surface provided with the antenna element, but the conductor may protrude from the surface provided with the antenna element.

GA ... ground area NGA ... non-ground area 20 ... module substrate 21 ... first antenna element 22 ... second antenna element 23 ... shield case 24 ... conductor 25 ... through hole 26 ... module fixing metal plate 27 ... casings 101 to 104 ... Communication module

Claims (6)

A substrate provided with a non-ground region at an end, and an antenna element provided in the non-ground region,
An antenna device provided with a plate-like conductor connected to the ground of the substrate and extending in a direction perpendicular to the substrate.   The antenna device according to claim 1, wherein an extension length of the conductor corresponds to approximately ¼ wavelength at a resonance frequency of the antenna element. The substrate includes a wireless communication circuit and a shield plate covering the wireless communication circuit,
The antenna device according to claim 1, wherein the conductor is a part of the shield plate.   The antenna device according to claim 3, wherein the substrate includes a slit hole that penetrates a part of the shield plate, and a part of the shield plate protrudes from a surface opposite to a surface on which the antenna element is formed. . A conductor surface disposed at a predetermined distance away from the conductor in a direction opposite to the position of the antenna element;
The antenna device according to claim 1, wherein the conductor surface is a housing that fixes the substrate.   The antenna device according to claim 1, wherein the antenna element includes a first antenna element and a second antenna element, and the conductor is provided on the second antenna element side.