JP5533224B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device.

  The wireless communication device is, for example, an electronic device having a wireless communication function. Specifically, a wireless terminal such as a mobile phone, a smart phone, a PDA (Personal Digital Assistant), a PC (Personal Computer), a GPS (Global Positioning System) terminal, or a wireless communication card (for example, a PCMCIA card). Communication application equipment can be included.

  In recent years, in the field of wireless communication devices, there are multiband wireless communication devices that use a plurality of wireless frequency bands. The design of wireless communication devices, especially wireless terminals, is becoming more and more complex year by year, and it is desired that the antenna elements arranged in the device be as small and light as possible.

  Prior art documents related to the present application include the following patent documents 1 to 3.

Japanese Patent Laid-Open No. 10-51223 International Publication WO2007 / 043150 JP-T-2002-504770

  In a limited space in the wireless communication device, the high-frequency circuit (RF circuit) mounted on the ground plane and the internal antenna are arranged close to each other. For this reason, it is desired that efficient impedance matching be performed between the RF circuit and the internal antenna.

  One object of an aspect of the present invention is to provide an antenna device capable of achieving appropriate impedance matching for a plurality of bands.

One aspect of the present invention includes a main antenna element connected to a feeding point;
Including at least one parasitic antenna element disposed at a predetermined distance from the main antenna element and having no contact with the feeding point;
The parasitic antenna element has a smaller size than the main antenna element;
Each of the main antenna element and the parasitic antenna element is an antenna device formed in a flat plate shape having at least one corner bent at a right angle.

  According to one embodiment of the present invention, it is possible to provide an antenna device capable of appropriate impedance matching for a plurality of bands.

FIG. 1 shows a configuration example of an antenna device according to the first embodiment. FIG. 2 is a graph showing S parameters (scattering parameters) of the antenna apparatus shown in FIG. FIG. 3 is an impedance chart of the antenna device shown in FIG. FIG. 4 shows a radiation pattern related to the 1.8 GHz band of the antenna device shown in FIG. FIG. 5 shows a radiation pattern related to the 2.4 GHz band of the antenna device shown in FIG. FIG. 6 illustrates a configuration example of the antenna device according to the second embodiment. FIG. 7 is a graph showing S parameters (scattering parameters) of the antenna device shown in FIG. FIG. 8 shows a radiation pattern related to the 1.7 GHz band of the antenna device shown in FIG. FIG. 9 shows a radiation pattern related to the 2.0 GHz band of the antenna device shown in FIG. FIG. 10 shows a radiation pattern related to the 2.45 GHz band of the antenna device shown in FIG. FIG. 11 illustrates a configuration example of the antenna device according to the third embodiment. 12 is a graph showing S parameters (scattering parameters) of the antenna apparatus shown in FIG. FIG. 13 shows a radiation pattern related to the 1.8 GHz band of the antenna device shown in FIG. FIG. 14 shows a radiation pattern related to the 2.45 GHz band of the antenna device shown in FIG. FIG. 15 illustrates a configuration example of the antenna device according to the fourth embodiment. FIG. 16 is a graph showing S parameters (scattering parameters) of the antenna device shown in FIG. FIG. 17 shows a radiation pattern related to the 1.8 GHz band of the antenna device shown in FIG. 18 shows a radiation pattern related to the 2.45 GHz band of the antenna device shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The configuration of the following embodiment is an exemplification, and the present invention is not limited to the configuration of the embodiment.

Embodiment 1
FIG. 1 is a diagram illustrating a configuration example of an antenna device according to the first embodiment. In FIG. 1, an antenna device 1 is a multiband coupled monopole antenna that is assumed to be used in the 1.8 GHz band and the 2.45 GHz band.

  The antenna device 1 is provided in a state of extending in the plane direction of the substrate 3 from the end of the substrate 3 on which an RF circuit (not shown) connected to the antenna device 1 via the feeding point 2 is mounted. Yes. The antenna device 1 includes a main antenna element 4 formed in an L-shaped flat plate shape, and a parasitic antenna element 5 arranged at a predetermined interval (distance) from the main antenna element 4.

  The main antenna element 4 has a strip-shaped first portion 4a connected at one end to the feeding point 2 provided on the substrate 3, and the extending direction of the first portion from the other end of the first portion 4a. A second portion 4b extending in an orthogonal direction is formed, and a portion where the first portion 4a and the second portion 4b intersect forms a corner 4c that is bent at a right angle.

The parasitic antenna element 5 is a parasitic antenna element that does not have a feeding line (does not have a contact point with a feeding point). The parasitic antenna element 5 has a size smaller than that of the main antenna element 4 and is disposed inside the corner 4 c of the main antenna element 4. The parasitic antenna element 5 is disposed in parallel with the first part 5a and the second part 4b arranged in parallel with the first part 4a of the main antenna element 4, and is secondly orthogonal to the first part 5a. Part 5b. A portion where the first portion 5a and the second portion 5b intersect forms a corner 5c that is bent at a right angle.

  The parasitic antenna element 5 is arranged on the same plane as the main antenna element 4 with a predetermined gap (interval) D. By adjusting the distance D between the main antenna element 4 and the parasitic antenna element 5, appropriate impedance matching can be achieved.

  Although not shown, a region having the highest surface current density is generated only in the main antenna element 4 when radiating in the 1.8 GHz band. On the other hand, when radiating in the 2.45 GHz band, the region with the highest surface current density appears only in the parasitic antenna element 5, and the portion with the highest surface current density is the second portion 5 b of the parasitic antenna element 5. Appear in

  Part of the first portions 4a and 5a and the second portions 4b and 5b of the main antenna element 4 and the parasitic antenna element 5 are sealed by base materials 6a and 6b sandwiching the substrate 3 from both sides. The remaining portions 4b and 5b are also sealed with a base material 7a and 7b joined or integrally formed with the base materials 6a and 6b. The base materials 6a and 6b and the base materials 7a and 7b are formed using the same dielectric.

  FIG. 2 is a graph showing S parameters obtained by simulation of the antenna device 1. In the graph of FIG. 2, the vertical axis represents the S parameter (S1, 1: reflection loss), and the horizontal axis represents the frequency. A graph A shown in FIG. 2 shows an S parameter when the antenna device 1 shown in FIG. 1 is used. Graph B shown in FIG. 2 shows S parameters in a simulation when the main antenna element 4 and the parasitic antenna element 5 are formed in a straight line as a comparative example. FIG. 3 is an impedance chart showing the impedances of the first embodiment and the comparative example.

  In carrying out the simulation, the length (length of the first portion 4a and corner 4c) L1 of the main antenna element 4 of the first embodiment is set to 16 mm, and the length in the direction perpendicular to the extending direction is set. The length (the length of the corner 4c and the second portion 4b) was set to 30 mm. On the other hand, the length of the corner 5c and the second portion 5b of the parasitic antenna element was set to 24.25 mm. The main antenna element 4 and the parasitic antenna element 5 were set to have a gap of 0.5 mm. The base materials 6a, 6b and 7a, 7b were set to use a dielectric having a thickness of 2 mm and a relative dielectric constant of 4.2. The setting is an example, and the dimensions of the main antenna element 4 and the parasitic antenna element 5 can be set as appropriate.

  According to the graph A in FIG. 2, the antenna device 1 of Embodiment 1 has a small amplitude (reflection loss) of the S parameter in the 1.8 GHz band and 2.43 GHz, and in these two bands, It can be seen that more appropriate efficiency (sensitivity) can be obtained than in the comparative example (graph B). Further, as shown in FIG. 3, the impedance A according to the first embodiment is closer to the normalized impedance 1 (50Ω) than the impedance B according to the comparative example (see 1 and 2 in FIG. 3). It can be seen that impedance matching is achieved.

  The main antenna element 4 is used for 1.8 GHz radiation, and the parasitic antenna element 5 is used for 2.45 GHz radiation. FIG. 4 shows a radiation pattern related to the 1.8 GHz band of the antenna device 1 of the first embodiment, and FIG. 5 shows a radiation pattern related to the 2.45 GHz band of the antenna device 1 of the first embodiment.

  According to the first embodiment, the main antenna element 4 and the parasitic antenna 5 are formed in an L shape, and the parasitic antenna 5 is disposed inside the corner 4c of the main antenna element 4, so that each antenna element 4, The area occupied by the antenna element can be reduced as compared with the case where 5 is formed linearly. That is, the antenna can be downsized. On the other hand, the antenna device 1 is suitable for impedance matching for the 1.8 GHz band and the 2.45 GHz band, and can thus be used as a multiband antenna having appropriate radiation efficiency for a plurality of bands.

  In the example of FIG. 1, the parasitic antenna element 5 is disposed inside the corner 4c of the main antenna element 4. However, the parasitic antenna element 5 may be disposed along the main antenna element 4 outside the corner 4c. Good (see parasitic antenna 8 in FIG. 6).

[Embodiment 2]
Next, Embodiment 2 of the present invention will be described. Since the second embodiment has common points with the first embodiment, differences will be mainly described, and description of common points will be omitted. Constituent elements common to the first embodiment are given the same reference numerals.

  FIG. 6 illustrates a configuration example of the antenna device according to the second embodiment. As illustrated in FIG. 6, the antenna device 1 </ b> A according to the second embodiment includes a main antenna element 4 and two parasitic antenna elements 5 and 8. The main antenna element 4 and each of the parasitic antenna element 5 and the parasitic antenna element 8 are formed in an L shape. The configuration related to the main antenna element 4 and the parasitic antenna element 5 is substantially the same as that of the first embodiment.

  The parasitic antenna 8 includes a first portion 8a arranged in parallel along the first portion 4a of the main antenna 4 and a second portion arranged in parallel along the second portion 4b of the main antenna 4. 8b, and a portion where the first portion 8a and the second portion 8b intersect forms a corner 8c bent at a right angle. The parasitic antenna 8 is arranged on the same plane as the main antenna 4 with a predetermined gap (interval) corresponding to the distance D between the main antenna element 4 and the parasitic antenna element 5 outside the corner of the main antenna 4. ing.

  FIG. 7 is a graph showing S parameters (scattering parameters) obtained by simulation of the antenna device 1A shown in FIG. The vertical axis of the graph in FIG. 7 is the reflection loss and the horizontal axis is the frequency. In carrying out the simulation, the main antenna element 4 according to the second embodiment is set to have the same size (length L1, L2) as that of the first embodiment. The length L3 of the parasitic antenna element 5 was set to 23.5 mm, which is shorter than that of the first embodiment. The length L4 of the second portion 8b and the corner 8c of the parasitic antenna element 8 was set to 30.25 mm. Other conditions were set in the same manner as in the first embodiment. The setting is an example, and the dimensions of the main antenna element 4 and the parasitic antenna element 5 can be set as appropriate.

  As shown in FIG. 7, according to the antenna device 1A according to the second embodiment, it can be seen that the amplitude (reflection loss) is small in the 1.7 GHz band, the 2 GHz band, and the 2.45 GHz band. Therefore, it can be seen that the antenna device 1A according to the second embodiment is a multiband antenna in which appropriate impedance matching is achieved for the three bands of 1.7 GHz, 2 GHz, and 2.45 GHz.

  The main antenna element 4 is used for 1.7 GHz radiation, the parasitic antenna element 5 is used for 2.45 GHz radiation, and the parasitic antenna element 8 is used for 2.0 GHz radiation. FIG. 8 shows a radiation pattern related to the 1.7 GHz band of the antenna device shown in FIG. FIG. 9 shows a radiation pattern related to the 2.0 GHz band of the antenna device shown in FIG. FIG. 10 shows a radiation pattern related to the 2.45 GHz band of the antenna device shown in FIG.

  According to the second embodiment, when the parasitic antenna element 8 is added, the occupied area becomes larger than that of the first embodiment, but the parasitic antenna element 8 is arranged such that the main antenna element 4 and the corners (4c, 8c) coincide with each other. Since the antenna device 1A is disposed in the vicinity of the element 4, an increase in size of the antenna device 1A is suppressed. With a minimum size expansion, it is possible to obtain a multi-band antenna having appropriate impedance matching for the three bands and having appropriate radiation efficiency.

[Embodiment 3]
Next, a third embodiment of the present invention will be described. Since the third embodiment has common points with the first embodiment, differences will be mainly described, and description of common points will be omitted. Constituent elements common to the first embodiment are given the same reference numerals.

  FIG. 11 illustrates a configuration example of the antenna device 1B according to the third embodiment. As illustrated in FIG. 11, the antenna device 1 </ b> B according to the second embodiment includes a main antenna element 4 and a parasitic antenna element 5. However, unlike the first embodiment, the parasitic antenna element 5 is arranged in parallel with a gap (interval) D1 in a direction orthogonal to the main antenna element 4 and the antenna plane direction. The main antenna element 4 and the parasitic antenna element 5 are arranged in a state in which the corners 4c and 5c coincide with each other and the first and second portions extend in the same direction. In FIG. 11, the main antenna element 4 is sandwiched between the base materials 6a, 6b, 7a, 7b, and the parasitic antenna 5 is the base materials 7a, 7b and other base materials corresponding to the base materials 7a, 7b (not shown). It is placed between. Thus, in the third embodiment, as an example, the antenna element is housed inside the base material with a three-layer base material.

  12 is a graph showing S parameters (scattering parameters) of the antenna apparatus shown in FIG. The vertical axis of the graph of FIG. 12 is the reflection loss and the horizontal axis is the frequency. In carrying out the simulation, the main antenna element 4 according to Embodiment 3 was set to have a height L1 of 16 mm and a horizontal length L2 of 28 mm. The horizontal length L3 of the parasitic antenna 5 was set to 25.5 mm. The main antenna element 4 and the parasitic antenna element 5 are set to be sealed in the base material corresponding to the base materials 6a, 6b, 7a, and 7b. The setting is an example, and the dimensions of the main antenna element 4 and the parasitic antenna element 5 can be set as appropriate.

  As shown in FIG. 12, according to the antenna device 1B according to the third embodiment, it can be seen that the amplitude (reflection loss) is small in the 1.8 GHz band and the 2.45 GHz band. Therefore, it can be seen that the antenna device 1B according to the third embodiment is a multiband antenna in which proper impedance matching is achieved for two bands of 1.8 GHz and 2.45 GHz.

  The main antenna element 4 is used for 1.8 GHz radiation, and the parasitic antenna element 5 is used for 2.45 GHz radiation. FIG. 13 shows a radiation pattern related to the 1.8 GHz band of the antenna device shown in FIG. FIG. 14 shows a radiation pattern related to the 2.45 GHz band of the antenna device shown in FIG.

  Even if the position of the parasitic antenna element 5 with respect to the main antenna element 4 is changed from the same plane to a parallel state as in the antenna device 1B in the third embodiment, as in the first embodiment, 1.8 GHz and 2.45 GHz are used. A multiband antenna with appropriate impedance matching can be obtained.

  It is also possible to obtain a multiband antenna device having good radiation efficiency for the three bands by arranging a plurality of parasitic antennas 5 on both sides of the main antenna element 4.

[Embodiment 4]
Next, a fourth embodiment of the present invention will be described. Since the fourth embodiment has common points with the first embodiment, differences will be mainly described, and description of common points will be omitted. Constituent elements common to the first embodiment are given the same reference numerals.

  FIG. 15 illustrates a configuration example of the antenna device according to the fourth embodiment. As shown in FIG. 15, the antenna device 1C according to the fourth embodiment includes a main antenna element 4A and a parasitic antenna element 5A each formed in a crank shape.

  The main antenna element 4A has a first portion 4a and a second portion 4b that form a corner 4c bent at a right angle, and further, a first portion bent at a right angle in a direction opposite to the corner 4c with respect to the second portion 4b. A third portion 4d forming the two corners 4e is provided.

  The parasitic antenna element 5A is disposed on the same plane as the main antenna element 4A, and has a first portion 5a and a second portion 5b that form a corner 5c bent at a right angle, like the main antenna element 4. Further, a third portion 5d that forms a second corner 5e that bends at a right angle to the second portion 5b in a direction opposite to the corner 5c is provided.

  The parasitic antenna element 5A has the first portion, the second portion, and the third portion in a state where the corner 5c is matched with the corner 4c and the second corner 5e is matched with the second corner 4e. A predetermined gap (interval) D is provided along the main antenna element 4 in a parallel state. Further, in the example of FIG. 15, the third portions 4d and 5d are sandwiched between base materials 9a and 9b using the same dielectric as the base materials 7a and 7b, and are accommodated in the base material.

  FIG. 16 is a graph showing S parameters (scattering parameters) of the antenna device shown in FIG. In the graph of FIG. 16, the vertical axis represents reflection loss and the horizontal axis represents frequency. FIG. 16 includes a graph C showing the S parameter (reflection loss) of the antenna apparatus 1C according to Embodiment 4, and a graph A showing the S parameter (reflection loss) of the antenna apparatus 1 according to Embodiment 1 as a comparative example. It is shown.

  In contrast between graph C and graph A, there is a good reflection loss for 1.8 GHz and 2.45 GHz, respectively. Further, the antenna device 1C has a reflection loss smaller than the antenna device 1 at 1.8 GHz. Thus, it can be seen that the antenna device 1C according to the fourth embodiment is a multiband antenna in which proper impedance matching is achieved in two bands of 1.8 GHz and 2.45 GHz.

  The main antenna element 4 is used for 1.8 GHz radiation, and the parasitic antenna element 5 is used for 2.45 GHz radiation. FIG. 17 shows a radiation pattern related to the 1.8 GHz band of the antenna device shown in FIG. 18 shows a radiation pattern related to the 2.45 GHz band of the antenna device shown in FIG.

  According to the fourth embodiment, even when the main antenna element 4 and the parasitic antenna element 5 are formed in a crank shape having two corners, they are used as a multiband antenna in which appropriate impedance matching is achieved for the two bands. be able to.

  In the fourth embodiment, the parasitic antenna element 5 is disposed inside the main antenna element, but may be disposed outside. Further, two crank-shaped parasitic antennas can be provided on the same plane as the main antenna element 4 as in the second embodiment.

The parasitic antenna element 5 can also be arranged in parallel to the main antenna element. Furthermore, a crank-shaped parasitic antenna element can be arranged on both sides of the main antenna element 4A. Further, it is possible to prepare two or more parasitic antenna elements, one arranged on the same plane as the main antenna element, and the other arranged parallel to the main antenna element. At this time, one parasitic antenna may be L-shaped and the other parasitic antenna may be crank-shaped. Combinations of the constituent elements of Embodiments 1 to 4 as described above are possible without departing from the object of the present invention, and the combinations described above are included in the aspects of the present invention.

1, 1A, 1B, 1C ... Antenna device 2 ... Feed point 3 ... Substrate 4, 4A ... Main antenna elements 4a, 5a, 8a ... First portions 4b, 5b, 8b ..Second portions 4c, 5c, 8c... Corners 5, 5A, 8... Parasitic antenna elements 6a, 6b, 7a, 7b, 9a, 9b.

Claims (7)

A main antenna element connected to the feed point;
Including at least one parasitic antenna element that is disposed at a predetermined interval from the main antenna element and does not have a contact point with the feeding point and ground ;
The parasitic antenna element has a smaller size than the main antenna element;
Each of the main antenna element and the parasitic antenna element is formed in a flat plate shape having at least one corner bent at a right angle. The antenna device according to claim 1, wherein the main antenna element and the parasitic antenna element are arranged on the same plane. Each of the main antenna element and the parasitic antenna element is formed in an L shape,
The antenna device according to claim 2, wherein the parasitic antenna element is arranged along the main antenna element inside or outside the corner of the main antenna element. Two parasitic antenna elements,
Each of the main antenna element and the parasitic antenna element is formed in an L shape,
One of the parasitic antenna elements is disposed along the main antenna element inside the corner of the main antenna element;
The antenna apparatus according to claim 2, wherein the other of the parasitic antenna elements is disposed along the main antenna element outside the corner of the main antenna element. The antenna device according to claim 1 , wherein the main antenna element and the parasitic antenna element are arranged in parallel. Each of the main antenna element and the parasitic antenna element is formed in an L shape,
The antenna device according to claim 5, wherein the main antenna element and the parasitic antenna element are arranged in parallel with corners being matched. Each of the main antenna element and the parasitic antenna element is formed in a crank shape having a second corner that is bent at a right angle in a direction opposite to the corner,
The antenna device according to claim 2, wherein the parasitic antenna element is disposed along the main antenna element inside the corner of the main antenna element.

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