Antenna device and electronic apparatus comprising the same

An embodiment of the present invention relates to an antenna device and an electronic device including the antenna device.

A personal computer or television receiver has a built-in wireless interface that uses wireless LAN (Local Area Network), WiMAX (registered trademark), UWB (Ultra Wideband), Bluetooth (registered trademark), etc. Various electronic devices have been developed that allow content and various data to be downloaded from sites and the like.

By the way, in the antenna device used for the wireless interface, two antennas are generally used in order to obtain a diversity effect. Therefore, when accommodating the antenna device in the electronic device, it is necessary to secure a larger accommodating space as compared with the case where one antenna is used. On the other hand, in electronic devices such as personal computers, the surplus space in the housing is limited due to the thinning of the housing and the high-density mounting of circuit parts. Therefore, when the antenna device is housed in the electronic device, the two antennas have to be brought close to each other. However, if the two antennas come close to each other, the interference between the antennas increases, and the desired antenna performance may not be obtained.

Therefore, an antenna device has been proposed in which a notch is provided at a position between two antennas in the ground pattern to prevent a high-frequency signal from being propagated between the antennas due to this notch (for example, Patent Document). See 1). In addition, slits are provided at positions corresponding to the two antennas in the ground pattern, and stubs are provided at positions that are the axes of symmetry of the two antennas in the ground pattern, thereby reducing mutual coupling between the antennas. An antenna device has also been proposed (see, for example, Patent Document 2).

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2008-283464 (Fig. 7)</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2008-177668 (Fig. 9)</text></patcit></p>

<p> However, all of these conventionally proposed antenna devices have a configuration in which the high frequency current transmitted between the feeding ends of the two antennas is canceled by the open stub. For this reason, it is necessary to form notches, slits, and the like in which the dimensions are strictly set in the ground contact pattern, which requires labor and is complicated in structure and large-scale. Further, when wiring the power supply cable or the like, the notch provided in the grounding pattern may be short-circuited, which causes a decrease in reliability.</p><p> The present invention has been made by paying attention to the above circumstances, and an object of the present invention is to reduce the high frequency current transmitted between the feeding terminals of the antennas without using a complicated and large-scale structure, thereby reducing the high frequency current transmitted between the antennas. An object of the present invention is to provide an antenna device in which mutual interference is reduced and isolation characteristics are improved, and an electronic device equipped with the antenna device.</p>

<p> In the antenna device according to the embodiment, the first and second feeding terminals are provided on the antenna substrate on which the grounding pattern is formed. The distance between the first and second feeding terminals is set within a distance of approximately 1/4 wavelength or less of the wavelength corresponding to the preset resonance frequency. One end of a first antenna having a first band including the resonance frequency as a communication band is connected to the first power feeding terminal. Further, one end of a second antenna having a second band including at least the resonance frequency of the first antenna as a communication band is connected to the second feeding terminal. Further, between the first antenna and the second antenna, a first protruding portion is provided so as to protrude from the ground pattern of the antenna substrate. The first protruding portion has a function of laterally flowing a part of the current flowing through the grounding pattern between the first and second feeding terminals.</p>

<figref num="1">The figure which shows the structure of the electronic device provided with the antenna device which concerns on 1st Embodiment.</figref><figref num="2">The figure which shows the Example of the antenna device shown in FIG.</figref><figref num="3">The figure which shows the frequency characteristic of the interference between antennas by the antenna device shown in FIG.</figref><figref num="4">The figure which shows the VSWR frequency characteristic by each antenna of the antenna device shown in FIG.</figref><figref num="5">The figure which shows the relationship between the space between the 2nd antenna and a convex part, and the amount of band expansion in the antenna device shown in FIG.</figref><figref num="6">The figure which shows the structure of the electronic device provided with the antenna device which concerns on 2nd Embodiment.</figref><figref num="7">The figure which shows the structure of the electronic device provided with the antenna device which concerns on 3rd Embodiment.</figref><figref num="8">The figure which shows an example of the current distribution in the antenna device shown in FIG.</figref><figref num="9">The figure which shows the VSWR frequency characteristic by the antenna device shown in FIG.</figref><figref num="10">The figure which shows the structure of the electronic device provided with the antenna device which concerns on 4th Embodiment.</figref><figref num="11">The figure which shows the VSWR frequency characteristic by each antenna of the antenna device shown in FIG.</figref>

Hereinafter, embodiments will be described with reference to the drawings. [First Embodiment] FIG. 1 is a diagram showing a main configuration of an electronic device provided with an antenna device according to the first embodiment. This electronic device includes a notebook personal computer or a television receiver equipped with a wireless interface, and a printed wiring board 1 is housed in a housing (not shown).

The electronic device may be a portable terminal such as a navigation terminal, a mobile phone, a smart phone, a PDA (Personal Digital Assistant), or a tablet terminal, in addition to a notebook personal computer or a television receiver. Further, the printed wiring board 1 may be a part of a metal housing, a metal member such as a copper foil, or a laminated circuit board.

The printed wiring board 1 has a first area 1a and a second area 1b. An antenna device is provided in the first area 1a. A grounding pattern 3 is formed in the second area 1b. A plurality of circuit modules necessary for forming an electronic device are mounted on the back surface side of the printed wiring board 1. The circuit module includes a wireless unit 2. The wireless unit 2 has a function of transmitting and receiving a wireless signal using a frequency band assigned to the wireless system to be communicated.

Further, in the first area 1a, the first power supply terminal 5A is provided at a position corresponding to the vicinity of the corner of the grounding pattern 3, and a second power feeding terminal is provided at a position corresponding to the central portion of the grounding pattern 3. Terminal 5B is provided. These power supply terminals 5A and 5B are connected to the wireless unit 2 via power supply cables 4A and 4B, respectively. The power supply cables 4A and 4B consist of a coaxial cable in which the core wire is covered with a shielded wire, and are wired along the side of the ground pattern 3. The reason is to prevent adverse effects such as limitation of mounting space on the circuit module and the like mounted on the printed wiring board 1.

By the way, the antenna device is configured as follows. That is, the antenna device includes a first antenna 6A and a second antenna 6B. Both of these antennas 6A and 6B are composed of L-shaped monopole elements, and are arranged so that the horizontal portions parallel to the ground pattern 3 face in the same direction. The first and second antennas 6A, 6B cover the same frequency band of the wireless system in order to obtain the diversity effect.

Further, a convex portion 7 as a strip-shaped first protruding portion is provided between the first and second antennas 6A and 6B in the first area 1a. The convex portion 7 is formed by extending a part of the grounding pattern 3 to the first area 1a, and is formed parallel to the vertical portion of the second antenna 6B.

FIG. 2 is a diagram showing a specific arrangement relationship of the antenna device. In the figure, the arrangement interval between the first feeding terminal 5A and the second feeding terminal 5B is approximately 1/4 of the wavelength corresponding to the resonance frequencies of the first and second antennas 6A and 6B. Is set to. Note that this arrangement interval does not necessarily have to be limited to 1/4 wavelength, and can be set to any value as long as it is 1/4 wavelength or less.

Further, the distance D between the portion perpendicular to the grounding pattern 3 of the second antenna 6B and the convex portion 7 is a wavelength corresponding to the resonance frequencies of the first and second antennas 6A and 6B. It is set to 1/10 wavelength or less of. When the interval D is set in this way, the convex portion 7 operates as a non-feeding element with respect to the second antenna 6B, and the second antenna 6B is compared with the case where the second antenna 6B is used alone. It is possible to expand the resonance bandwidth of. Figure 5 shows an example of the analysis results. The figure shows the relationship between the interval D and the band expansion amount [MHz] for the resonance frequency of 5,850 MHz. As is clear from the figure, when the interval D is set to 1/10 wavelength or less, that is, 5 mm or less of the wavelength corresponding to the resonance frequency, the resonance bandwidth is expanded.

In the antenna device configured as described above, the distribution of the current flowing through the ground pattern 3 is distributed by providing the convex portion 7 in the vicinity of the second antenna 6B between the first and second antennas 6A and 6B. Changes, and the amount of high-frequency current flowing into each other's feeding terminals 5B, 5A between the first and second feeding terminals 5A, 5B decreases, and as a result, between the first and second antennas 6A, 6B. Mutual interference is reduced. FIG. 3 shows the change in the magnitude of interference between antennas with respect to frequency. As is clear from the figure, the maximum value of inter-antenna interference in the low frequency region can be suppressed by providing the convex portion 7.

Further, according to the first embodiment, it is possible to realize a wide band of the resonance band. FIG. 4 shows the results of analyzing the frequency characteristics of the voltage standing wave ratio (VSWR) of the first and second antennas 6A and 6B before and after the convex portion 7 is provided, respectively. As shown in the figure, the first antenna 6A can obtain almost the same characteristics as before the convex portion 7 is installed even after the convex portion 7 is installed. On the other hand, for the second antenna 6B, if the convex portion 7 is installed, the resonance band can be significantly widened in the medium and high frequency region as compared with before the convex portion 7 is installed.

As described in detail above, in the first embodiment, the first antenna 6A and the second antenna 6B made of the L-shaped monopole element have a wavelength in which the distance between the feeding terminals 5A and 5B corresponds to the resonance frequency. It is set so that it is within 1/4 wavelength, and the horizontal part parallel to the grounding pattern 3 is arranged so as to face the same direction. Then, it is extended from the ground pattern 3 to a position near the second antenna 6B between the first antenna element 6A and the second antenna 6B, for example, a position of 1/10 wavelength or less of the wavelength corresponding to the resonance frequency. The convex portion 7 is arranged.

Therefore, by providing the convex portion 7, the distribution of the current flowing through the ground pattern 3 changes, and the current of the high-frequency current flowing into each other's feeding terminals 5B and 5A between the first and second feeding terminals 5A and 5B. The amount decreases. Therefore, mutual interference between the first and second antennas 6A and 6B is reduced. That is, it is possible to improve the isolation characteristic between the antennas 6A and 6B with an extremely simple configuration in which the convex portion 7 is provided between the first and second antennas 6A and 6B.

Further, since the convex portion 7 is arranged near the second antenna 6B, for example, at a position within 1/10 of the wavelength corresponding to the resonance frequency from the second feeding point 5B, the convex portion 7 is arranged. Can be operated as a non-feeding element of the second antenna 6B, whereby the resonance band of the second antenna 6B can be expanded to widen the bandwidth of the antenna device.

Further, the horizontal portions parallel to the ground pattern 3 of the first and second antennas 6A and 6B are set to face the same direction, and the first power feeding terminal 5A is located near the corner of the ground pattern 3 and the first The power supply terminal 5B of 2 is provided at a position corresponding to the central portion of the grounding pattern 3. Therefore, even when the power supply cables 4A and 4B are wired along the side of the grounding pattern 3, the parallel sections where the power supply cables 4A and 4B and the horizontal parts of the first and second antennas 6A and 6B are close to each other are formed. It can be reduced, and the distance between the power supply cable 4B and the first antenna 6A can be separated by the outer diameter of the power supply cable 4A even in the parallel section, which makes it possible to separate the power supply cable for the first antenna 6A. The adverse effects of 4A and 4B can be reduced.

[Second Embodiment] FIG. 6 is a diagram showing a configuration of the antenna device according to the second embodiment. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. The grounding pattern 3 formed on the printed wiring board 1 is formed in a stepped shape so that the sides in contact with the first area 1a have steps at two locations 31A and 31B, respectively. The power supply cables 4A and 4B are wired along the side of the grounding pattern 3 from the wireless unit 2 to the portions 31A and 31B where the step is formed. Then, the core wires of the power feeding cables 4A and 4B are connected to the power feeding terminals 5A and 5B provided in the vicinity of the portions 31A and 31B where the step is formed on the first area 1a, respectively. Further, the shielded wires of the power feeding cables 4A and 4B are connected to the grounding pattern 3 at the portions 31A and 31B where the step is formed. As the connecting means of the core wire and the shielded wire, for example, soldering is used.

One ends of the first and second antennas 6A and 6B made of L-shaped monopole elements are connected to the power feeding terminals 6A and 6B, respectively. The first and second antennas 6A and 6B are arranged so that the horizontal portions parallel to the ground pattern 3 face in the same direction. Further, in the vicinity of the portion 31B where the above-mentioned step of the grounding pattern 3 is formed, a strip-shaped protruding portion (convex portion) is formed by extending a part of the grounding pattern 3 in parallel with the vertical portion of the second antenna 6B. ) 7 is formed. The distance D between the convex portion 7 and the vertical portion of the second antenna 6B is set to be 1/10 or less of the wavelength corresponding to the resonance frequencies of the first and second antennas 6A and 6B. There is.

In the second embodiment, as described in the first embodiment, the convex portion 7 is provided in the vicinity of the second antenna 6B between the first and second antennas 6A and 6B. An extremely simple configuration can improve the isolation characteristics between the antennas 6A and 6B and reduce the interference between the antennas 6A and 6B.

Further, since the convex portion 7 is arranged near the second antenna 6B, for example, at a position within 1/10 of the wavelength corresponding to the resonance frequency from the feeding point 5B, the convex portion 7 is placed at the second position. It is possible to operate the antenna 6B as a non-feeding element, thereby expanding the resonance band of the second antenna 6B and widening the wavelength of the antenna device.

Moreover, by forming the sides of the grounding pattern 3 in a staircase pattern so that there are steps at the two locations 31A and 31B, the power supply cables 4A and 4B are arranged along the sides of the grounding pattern 3 without bending into an unreasonable shape. This makes it possible to improve the reliability of the antenna device and the electronic device. Further, by wiring the power supply cables 4A and 4B along the end edge of the printed wiring board 1, the mounting space of the printed wiring board 1 is effectively utilized to improve the mounting efficiency of electronic components and circuit modules per unit area. be able to.

[Third Embodiment] FIG. 7 is a diagram showing a configuration of an electronic device including the antenna device according to the third embodiment. In the same figure as well, the same parts as those in FIGS. 1 and 6 are designated by the same reference numerals, and detailed description thereof will be omitted. The grounding pattern 3 formed on the printed wiring board 1 is formed in a stepped shape so that the sides in contact with the first area 1a have steps at two locations 31A and 31B, respectively. The power supply cables 4A and 4B are wired along the side of the grounding pattern 3 from the wireless unit 2 to the portions 31A and 31B where the step is formed. Then, the core wires of the power feeding cables 4A and 4B are connected to the power feeding terminals 5A and 5B provided in the vicinity of the portions 31A and 31B where the step is formed on the first area 1a, respectively.

On the other hand, the antenna device has first and second athena 8A and 8B each formed by combining a plurality of antenna elements. The first antenna 8A is composed of a folded monopole element 81 and an L-shaped non-feeding element 82. One end of the folded monopole element 81 is connected to the first power feeding terminal 5A, and the other end is connected to the ground pattern 3. The base end of the non-feeding element 82 is connected to the ground pattern 3 in the vicinity of the first feeding terminal 5A, and the horizontal portion is arranged above the folded monopole element 81.

The second antenna 8B is composed of a folded monopole element 83 having a stub 84 and a monopole element 85. One end of the folded monopole element 83 with a stub is connected to the second power feeding terminal 5B, and the other end is connected to the ground pattern 3. The base end of the monopole element 85 is connected to the second power feeding terminal 5B, and the tip is open.

Further, in the first area 1a of the printed wiring board 1, a convex portion 7 as a second protruding portion is provided at a position between the first antenna 8A and the second antenna 8B. The convex portion 7 is formed of a strip-shaped conductive pattern in which a part of the ground contact pattern 3 is extended in the vertical direction, as in the first and second embodiments described above. The distance D between the convex portion 7 and the second feeding point 5B is set to be 1/10 or less of the wavelength corresponding to the resonance frequencies of the first and second antennas 8A and 8B.

As described above, in the third embodiment, the convex portion is located near the second antenna 6B between the first and second antennas 6A and 6B, for example, at a position within 1/10 of the wavelength corresponding to the resonance frequency. 7 is installed. Therefore, for example, as shown in FIG. 8, the current distribution of the high-frequency current flowing on the ground pattern 3 changes, which reduces the current values flowing into each other between the first and second power feeding terminals 5A and 5B. Therefore, mutual interference between the first and second antennas 8A and 8B is reduced, which improves the isolation characteristics between both antennas 8A and 8B. As a result, it is possible to obtain the same characteristics as when the first antenna 8A is provided alone.

FIG. 9 shows the VSWR frequency characteristics when the convex portion 7 is provided between the first and second antennas 8A and 8B, when the convex portion 7 is not provided and when the first antenna 8A is provided alone. It is the figure which showed in comparison. As is clear from the figure, by providing the convex portion 7, the isolation characteristic between the first and second antennas 8A and 8B is improved, which is equivalent to the case where the first antenna 8A is provided alone. It is possible to obtain the characteristics.

Further, since the convex portion 7 is arranged near the second antenna 6B, for example, at a position within 1/10 of the wavelength corresponding to the resonance frequency from the feeding point 5B, the convex portion 7 is placed at the second position. It is possible to operate the antenna 6B as a non-feeding element, thereby expanding the resonance band of the second antenna 6B and widening the wavelength of the antenna device.

Moreover, by forming the sides of the grounding pattern 3 in a staircase pattern so that there are steps at the two locations 31A and 31B, the power supply cables 4A and 4B are arranged along the sides of the grounding pattern 3 without bending into an unreasonable shape. This makes it possible to improve the reliability of the antenna device and the electronic device. Further, by wiring the power supply cables 4A and 4B along the end edge of the printed wiring board 1, the mounting space of the printed wiring board 1 is effectively utilized to improve the mounting efficiency of electronic components and circuit modules per unit area. be able to.

[Fourth Embodiment] FIG. 10 is a diagram showing a configuration of an electronic device including the antenna device according to the fourth embodiment. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. In the first area 1a of the printed wiring board 1, a convex portion 7 as a second protruding portion is provided between the first and second antennas 6A and 6B as described in the first embodiment. There is. At the same time, a convex portion 9 as a second protruding portion is also provided on the side of the first antenna 6A where the second antenna 6B is not installed. Each of these convex portions 7 and 9 consists of a strip-shaped conductive pattern formed by extending a part of the grounding pattern 3 to the first area 1a, and is vertical to the second and first antennas 6B and 6A, respectively. It is formed parallel to the site. The distance between the convex portion 9 and the vertical portion of the first antenna 6A is the same as the distance between the convex portion 7 and the vertical portion of the second antenna 6B of the first and second antennas 6A and 6B. It is set to 1/10 or less of the wavelength corresponding to the resonance frequency.

With such a configuration, by providing the convex portion 7 in the vicinity of the second antenna 6B between the first and second antennas 6A and 6B, the distribution of the current flowing through the ground pattern 3 changes. The amount of high-frequency current flowing into each other's feeding terminals 5B and 5A between the first and second feeding terminals 5A and 5B is reduced, and as a result, mutual interference between the first and second antennas 6A and 6B is reduced. To. Further, by providing the convex portion 9 in the vicinity of the first antenna 6A, the convex portion 9 operates as a non-feeding element for the first antenna 6A, thereby expanding the resonance band of the first antenna 6A. It becomes possible.

FIG. 11 shows the VSWR frequency characteristics of the second antenna 6B provided with the convex portion 7 and the first antenna 6A provided with the convex portion 9 in comparison with the case where the convex portions 7 and 9 are not provided. It is a figure. As shown in the figure, by providing the convex portions 7 and 9, it is possible to widen the resonance band of both the first and second antennas 6A and 6B in the high frequency direction.

[Other Embodiments] In each of the above embodiments, the case where the first and second antennas are arranged so that their horizontal portions face the same direction has been described as an example. However, the present invention is not limited to this, and the horizontal portions may be arranged so as to face opposite directions, that is, the first and second antennas may be arranged symmetrically. In this case, if the first and second power supply cables are bundled and wired along the side of the grounding pattern, a section in which the horizontal portion of the first antenna and the first power supply cable are parallel to each other is generated, and the first The antenna is affected. However, the protrusion 7 arranged between the first and second antennas suppresses the interference between the first and second antennas.

In addition, the types and configurations of the first and second antennas, the shape and installation position of the protrusions, the wiring structure of the feeding table, the types and configurations of electronic devices, and the like can be variously modified and implemented. Although some embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... printed wiring board, 2 ... wireless circuit, 3 ... grounding pattern, 4A, 4B ... power supply cable, 5A, 5B ... power supply point, 6A, 8A ... first antenna , 6B, 8B ... 2nd antenna, 7 ... 1st protrusion (convex part), 9 ... 2nd protrusion (convex part), 31A, 31B ... crank-shaped part, 81,83 ... folded monopole element, 82 ... no power supply element, 84 ... stub, 85 ... monopole element.