JP2013131800A - Antenna device, downsizing method of antenna device, and communication device including antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna device including a loop shaped antenna formed by a pattern on a substrate, and to provide a technique of a downsizing method of the antenna device.SOLUTION: In an antenna device, an antenna is mounted on a substrate. The antenna device includes: a ground part formed on the substrate; a feeding point connected with the ground part and supplying electric power to the antenna; and the antenna which has one end serving as a feeding part and connected with the ground part through the feeding point and the other end serving as an earth part, connected with a point near the ground part with which the feeding part is connected, forming a loop shape, and having a portion located adjacent to the ground part and formed into a meander shape.

Description

  The present invention relates to an antenna device including an antenna patterned on a substrate, a method for miniaturizing the antenna device, and a communication device including the antenna device.

  At present, the antennas of wireless devices are becoming more and more built-in, and further downsizing of the devices themselves and the number of antennas are increasing, so it is necessary to ensure the characteristics in a narrow antenna area.

  In general, the length of the antenna corresponds to the wavelength of the received signal, and the antenna length becomes longer when the frequency of the received signal is low. Since the resonance frequency of the loop-shaped antenna is λ (λ is the wavelength) and the resonance frequency of the inverted L-shaped antenna is λ / 4, the length of the loop-shaped antenna is the wavelength and the inverted L-shaped antenna. Is designed to be 1/4 of the wavelength.

  FIG. 16A shows an example in which a loop-shaped antenna 30 ′ is mounted on a substrate 10 ′ as a 2.4 GHz band wireless LAN antenna. FIG. 16B is an enlarged view showing the configuration of the antenna portion of the antenna device 1 ′ shown in FIG. In this example, the board 10 'is assumed to be a wireless LAN router, and the distance between the antenna 30' and the ground portion (GND) 20 'is 5 mm. In this configuration, the length in the horizontal direction of the antenna 30 'patterned on the substrate is 44.5 mm.

  On the other hand, FIG. 17A shows an example in which an inverted L-shaped antenna 30 ′ having the same distance of 5 mm between the antenna 30 ′ and the ground portion (GND) 20 ′ is designed. FIG. 17B is an enlarged view showing the configuration of the antenna portion of the antenna device 1 ′ shown in FIG. In this case, the lateral length of the antenna 30 'is 19.5 mm. This is because, as described above, the resonance of the loop-shaped antenna 30 ′ is λ, but the inverted L-shaped antenna 30 ′ resonates at λ / 4.

  18A illustrates the impedance characteristics and the return loss characteristics of the loop-shaped antenna 30 ′ illustrated in FIG. 16, and FIG. 18B illustrates the inverted L-shaped antenna 30 illustrated in FIG. It is a figure for demonstrating the impedance characteristic and return loss characteristic of '. As is apparent from the antenna characteristics shown in FIGS. 18A and 18B, the antenna characteristics of the loop-shaped antenna 30 ′ and the inverted L-shaped antenna 30 ′ are not preferable values for wireless communication. Absent. Thus, these antenna devices 1 ′ cannot obtain the antenna characteristics necessary for wireless communication.

  On the other hand, various antenna devices that incorporate an antenna on a substrate have been proposed.

  For example, Patent Document 1 discloses an antenna device that is downsized and widened. The antenna device disclosed in Patent Document 1 includes an antenna element formed on the same surface of a substrate and a ground element. In Patent Document 1, in the second embodiment, the entire antenna region is in a meander configuration.

  An example of a portable wireless terminal including an antenna element is described in Patent Document 2. In the portable wireless terminal, meandering meander portions are formed in a part of the ground portion of the flexible cable on the substrate disposed in the two housings slidably connected. . In Patent Document 2, the antenna characteristic is ensured by adjusting the GND length of the device by forming a meander in the flexible cable.

JP 2011-41097 A JP 2008-47949 A

  However, in the antenna device described above, when the distance between the antenna and the ground portion is small, the radiation resistance becomes small, so that it is difficult to secure a return loss that maintains the functionality of the antenna device, and thus the desired antenna characteristics can be obtained. In order to obtain this, there is a problem that a separate matching circuit is required.

  Further, in Patent Document 1, an inverted L-shaped antenna is used. However, when a loop-shaped antenna is used for an inverted L-shaped antenna, the resonance of the loop-shaped antenna has a wavelength λ and an inverted L-shape. Since the resonance of the shape antenna has a wavelength of λ / 4, the size of the loop shape antenna is increased, which is inconvenient for further miniaturization of the device. Therefore, since the loop-shaped antenna is larger than the inverted L-shaped antenna, the antenna device is rarely used to reduce the size of the antenna device. Further, in Patent Document 1, there is a problem that the ground loss position is on the side opposite to the feeding position, and the return loss is deteriorated simply by making the antenna meander.

  By the way, according to the diligent research of the present inventors, it is generally possible to reduce the size of the antenna device while ensuring a desired return loss by improving the loop-shaped antenna, which has been considered unsuitable for downsizing the antenna device. It became clear that it was possible to plan.

  An object of the present invention is to provide an antenna device including a loop-shaped antenna configured by a pattern on a base substrate and a method for downsizing the antenna device, which solves the above-described problem that requires a matching circuit. .

  In view of the above problems, according to one embodiment of the present invention, in an antenna device in which an antenna is mounted on a substrate, the ground portion formed on the substrate is connected to the ground portion, and power is supplied to the antenna. A feeding point and one end serving as a feeding part are connected to the ground part via the feeding point, and the other end serving as a grounding part is connected to the vicinity of the ground part to which the feeding part is connected to form a loop shape. And an antenna in which a portion adjacent to the ground portion is formed in a meander shape.

  According to another aspect of the present invention, in a method for reducing the size of an antenna device in which an antenna is mounted on a substrate, one end serving as a feeding portion of the antenna is connected to a ground portion formed on the substrate via a feeding point. And connect the other end, which becomes the grounding portion of the antenna, to the vicinity of the ground portion to which the feeding portion is connected to form a loop shape, and further form a portion adjacent to the ground portion in a meander shape. A method for miniaturizing an antenna device can be provided.

  According to the embodiment of the present invention, it is possible to reduce the size of a loop-shaped antenna whose pattern is designed on the device substrate, and it is possible to ensure a desired return loss without a matching circuit.

  Further advantages and embodiments of the present invention are described in detail below using the description and the drawings.

It is the schematic which shows the structure of the antenna apparatus by the 1st Embodiment of this invention. It is an enlarged view which shows the 1st step of the size reduction process of the antenna device by the 1st Embodiment of this invention. It is a figure which shows the characteristic of the antenna apparatus of FIG. It is an enlarged view which shows the 2nd step of the size reduction process of the antenna device by the 1st Embodiment of this invention. It is a figure which shows the characteristic of the antenna apparatus of FIG. It is the schematic which shows the structure of the antenna device by the 2nd Embodiment of this invention. The enlarged view of the antenna part in the antenna apparatus of FIG. 6 is shown. It is a figure which shows the characteristic of the antenna apparatus of FIG. It is a comparison figure which shows the antenna characteristic of the antenna apparatus in each embodiment of this invention. It is a figure which shows the structural example of a related antenna apparatus. It is a figure which shows the characteristic of the antenna apparatus of FIG. The enlarged view of the antenna part in the antenna device by the 3rd Embodiment of this invention is shown. It is a figure which shows the characteristic of the antenna apparatus of FIG. The enlarged view of the antenna part in the modification of the antenna device by the 3rd Embodiment of this invention is shown. It is a figure which shows the characteristic of the antenna apparatus of FIG. (A) is the schematic which shows the other structural example of the related antenna apparatus, (b) shows the enlarged view of the antenna part of the said antenna apparatus. (A) is the schematic which shows another structural example of the related antenna apparatus, (b) shows the enlarged view of the antenna part of the said antenna apparatus. (A) is a figure which shows the characteristic of the antenna apparatus of FIG. 16, (b) is a figure which shows the characteristic of the antenna apparatus of FIG.

  Embodiments of the present invention will be described below with reference to the drawings. However, the technical scope of the present invention is not construed as being limited by the embodiments described below.

(First embodiment)
First, a first embodiment of the present invention will be described.

  FIG. 1 is a schematic diagram illustrating a configuration of an antenna device 1 according to a first embodiment of the present invention. The antenna device 1 according to the present embodiment is used for, for example, a wireless device in which a built-in antenna device is configured on a device substrate.

  In the present embodiment, the coordinate system (X, Y) is used for convenience. In the state illustrated in FIGS. 1 to 5, in the coordinate system (X, Y), the X-axis direction is the front-rear direction (longitudinal direction) extending in parallel to the substrate 10, and the Y-axis direction is the substrate 10. The horizontal direction (lateral direction) extends in parallel and is orthogonal to the X-axis direction.

  The antenna device 1 shown in FIG. 1 includes a substrate 10, a ground portion 20, a loop-shaped antenna 30, and a feeding point 40 that supplies AC power. 2 to 5 are diagrams for explaining the details of the antenna device 1 according to the first embodiment of the present invention.

  Hereinafter, each component which comprises the antenna apparatus 1 by the 1st Embodiment of this invention is demonstrated in detail.

  The substrate 10 is, for example, a printed circuit board provided with an oscillation circuit or an electronic circuit that generates an electric signal, and has a rectangular flat plate shape. On the surface of the substrate 10, a ground portion 20, an antenna 30, and the like are arranged. In the present embodiment, the board size is assumed to be a wireless LAN router. As an example, the board 10 is 120 mm long and 90 mm wide. This dimension is exemplary and is not limited to the vertical and horizontal dimensions.

  The ground portion 20 is formed on the surface of the substrate 10 as a ground pattern, and functions as an earth side. In the present embodiment, the distance between the antenna 30 and the ground portion 20 is 5 mm.

  The antenna 30 is a member formed in a loop shape disposed on the surface of the substrate 10 and can be formed of a conductive material such as a copper wire, an aluminum wire, or an aluminum alloy wire. Here, the antenna 30 is designed to have a lateral length (Y-axis direction) of 16.75 mm.

  Referring to FIG. 4, it can be seen that the antenna 30 includes a first antenna element 30A, a second antenna element 30B, a third antenna element 30C, and a fourth antenna element 30D. Specifically, the loop-shaped antenna 30 includes a first antenna element 30A connected to the ground portion via a feeding point and extending in the first direction (X-axis direction), and the first antenna element 30A. A second antenna element 30B connected and extending in a second direction (Y-axis direction) orthogonal to the first direction, and connected in parallel to the first antenna element 30B and connected to the second antenna element 30B A third antenna element 30C extending in parallel with the second antenna element 30B and a fourth antenna element 30D formed in a meander shape extending parallel to the third antenna element 30C. Have

  The feeding point 40 is a point for feeding AC power to the supply unit of the antenna 30. The feeding point 40 is electrically connected to the ground unit 20 at one end and electrically connected to the supply unit of the antenna 30 at the other end.

  Next, each step of reducing the size of the antenna device 1 according to the present embodiment will be described with reference to FIGS. Note that the antenna characteristics shown in FIGS. 3 and 5 are exemplary, and return loss and the like can be further improved by finely adjusting the antenna length.

  FIG. 2 is an enlarged view of the antenna device 1 in which the grounding unit of the loop-shaped antenna device illustrated in FIG. 16 is moved to the vicinity of the supply unit. In the example of FIG. 16, the length of the antenna 30 in the horizontal direction is 44.5 m. However, the antenna 30 of FIG. 2 can be designed to have a horizontal length of 19.5 m. FIG. 3 shows impedance characteristics and return loss characteristics according to the antenna configuration of FIG. Referring to FIG. 3, it can be seen that the antenna device 1 can secure a return loss that allows wireless communication. According to the inventors of the present invention, in general, it is clear that desired antenna characteristics can be obtained when a return loss of about −5 dB or less can be secured.

  Next, FIG. 4 shows the antenna device 1 in which the fourth antenna element 30D of the antenna 30 shown in FIG. 2 in the vicinity of the ground portion 20 formed on the surface of the substrate 10 is formed in a meander shape. In this configuration, the lateral length of the antenna 30 of the antenna device 1 can be designed to be 16.75 mm. FIG. 5 shows impedance characteristics and return loss characteristics of the antenna configuration of FIG. Referring to FIG. 5, it can be seen that the antenna device 1 can secure a return loss that allows wireless communication.

  The first embodiment of the present invention described above has the following effects.

  The first effect is that the antenna device 1 corresponding to a desired frequency band can be reduced in size. The second effect is that desired antenna characteristics can be secured without providing a matching circuit in the antenna device 1 itself. The reason is that the antenna 30 of the antenna device 1 is formed in a loop shape, the grounding portion thereof is grounded adjacent to the feeding portion, and a part of the antenna elements 30D are configured in a meander shape.

(Second Embodiment)
Subsequently, a second embodiment of the present invention will be described. The second embodiment of the present invention is a modification of the above-described first embodiment. Hereinafter, in the present embodiment, parts having the same functions as those already described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  Here, as shown in FIGS. 6 to 8, a coordinate system (X, Y) is used. 6 to 8, in the coordinate system (X, Y), the X-axis direction is the front-rear direction (longitudinal direction) extending in parallel to the substrate 10, and the Y-axis direction is the substrate 10. The horizontal direction (lateral direction) extends in parallel and is orthogonal to the X-axis direction.

  In the antenna device 1 according to the second embodiment of the present invention shown in FIGS. 6 to 8, the antenna element 30 </ b> D is formed in a meander shape, and the ground portion 20 is formed in a meander shape of the antenna 30. It has a meander-shaped extending portion 21 extending corresponding to the element 30D.

  In this embodiment, the horizontal length of the antenna 30 can be designed to be 14 mm by matching the shape of a part of the ground portion 20 with the meander shape of the antenna element 30D as shown in FIG.

  FIG. 8 shows impedance characteristics and return loss characteristics according to the antenna configurations of FIGS. 6 and 7. Referring to FIG. 8, it can be seen that the antenna device 1 can secure a return loss that allows wireless communication. Note that the antenna characteristics shown in FIG. 8 are exemplary, and it goes without saying that the return loss and the like can be further improved by finely adjusting the antenna length.

  The second embodiment of the present invention described above has the following effects.

  The first effect is that the antenna device 1 corresponding to a desired frequency band can be further downsized. The reason is that a curved portion is formed in the ground portion 20 of the antenna device 1 in a portion adjacent to the antenna element 30D, and a part of the ground portion 20 is formed in a meander shape so as to correspond to the meander shape of the antenna element 30D. Because.

(Comparative example)
Next, FIG. 9 shows a graph comparing the antenna characteristics of each antenna device 1 described above. Note that a matching circuit is separately added to the antenna device shown in FIGS. 16 and 17. As can be seen from FIG. 9, the antenna device 1 according to the first and second embodiments has antenna characteristics capable of wireless communication at each frequency of 2400, 2442, and 2484 MHz without adding a matching circuit. . Therefore, it is not necessary to provide a matching circuit in the antenna device 1 described in each embodiment, and the antenna device 1 can be simplified.

  As an example, FIG. 10 shows a configuration in which the shape of the antenna in the antenna device of FIG. FIG. 11 shows impedance characteristics and return loss characteristics of the antenna configuration of FIG. Referring to FIG. 11, it is apparent that this antenna device 1 has a poor return loss value, and with this configuration, it is difficult to secure antenna characteristics to the extent that wireless communication is possible even if adjustment is performed with a matching circuit.

(Third embodiment)
Subsequently, a third embodiment of the present invention will be described. The third embodiment of the present invention is a modification of the above-described first embodiment. Hereinafter, in the present embodiment, parts having the same functions as those already described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  Here, as shown in FIGS. 12 to 15, a coordinate system (X, Y) is used. 12 to 15, in the coordinate system (X, Y), the X-axis direction is the front-rear direction (longitudinal direction) extending in parallel to the substrate 10, and the Y-axis direction is the substrate 10. The horizontal direction (lateral direction) extends in parallel and is orthogonal to the X-axis direction.

  12 to 15 are schematic views for explaining an antenna device 1 according to a third embodiment of the present invention. The antenna device 1 corresponding to the 2.4 GHz band of the wireless LAN has been described so far. However, in this embodiment, the two resonance circuits 50 </ b> A and 50 </ b> B are mounted in the middle of the antenna 30 in order to support the 5 GHz band. An antenna device 1 (see FIG. 12) is provided.

  The resonant circuits 50A and 50B are each configured by an inductor (coil) and a capacitor (capacitor) connected in parallel or the like. In addition, the resonance circuits 50A and 50B can be electrically connected to the antenna 30 on one side and electrically connected to the ground unit 20 on the other side. For example, the resonance circuits 50A and 50B are connected between the antenna elements 30C and 30D. There is a case.

  The resonant circuit 50A cuts the 2.4 GHz band and passes the 5 GHz band. The position of the resonance circuit 50A can be adjusted by the corresponding band. On the contrary, the resonant circuit 50B passes the 2.4 GHz band and cuts the 5 GHz band. The position of the resonance circuit 50B can be adjusted by the corresponding band. Further, the resonance circuit 50B may not be mounted on the antenna device 1 depending on the corresponding frequency. As a position where these resonant circuits 50A and 50B are mounted, for example, the antenna 30 of the antenna device 1 is divided into one of the antenna elements 30A, 30B, 30C and 30D and the antenna elements 30A and 30B of the divided antenna 30 are separated. , 30C, 30D can be mounted so as to be connected.

  FIG. 13 shows impedance characteristics and return loss characteristics of the antenna device 1 shown in FIG. This antenna device 1 ensures return loss in both the 2.4 GHz band and the 5 GHz band. Specifically, referring to FIG. 13, it can be seen that the antenna device 1 can secure a return loss that allows wireless communication.

  In some cases, the resonance circuit 50B can be deleted. FIG. 15 shows an antenna device 1 in which only the resonance circuit 50A is mounted without providing the resonance circuit 50B. FIG. 15 shows impedance characteristics and return loss characteristics of the antenna device 1 shown in FIG. This antenna device 1 ensures return loss in both the 2.4 GHz band and the 5 GHz band. Specifically, referring to FIG. 15, it can be seen that the antenna apparatus 1 has a return loss that allows wireless communication. In the antenna device 1 of FIG. 14, the return loss is slightly degraded as compared with the antenna device 1 of FIG. The antenna characteristics shown in FIGS. 13 and 15 are exemplary, and return loss and the like can be further improved by finely adjusting the antenna length.

  The third embodiment of the present invention described above has the following effects.

  The first effect is that the miniaturized antenna device 1 can cope with two frequency bands. The reason is that the resonant circuit 50A and / or the resonant circuit 50B is mounted at a desired position of the antenna 30 according to the corresponding band.

  The second effect is that the antenna device 1 capable of supporting a plurality of bands can be realized without changing the dimensions of the antenna 30 of the antenna device 1. The reason is that a part of the antenna element 30D and the ground part 20 facing the antenna element 30D are arranged in a meander shape by adjoining the power feeding part and the grounding part of the antenna 30 formed in a loop shape, and a resonance circuit is provided in the antenna 30. This is because it was implemented appropriately.

  Note that communication devices such as a wireless LAN router equipped with the antenna device 10 included in the first and second embodiments described above are also included in the scope of the present invention.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-mentioned embodiment is only a mere illustration in all points, and should not be interpreted limitedly. The scope of the present invention is indicated by the scope of the claims, and is not restricted by the text of the specification. Furthermore, all modifications, various improvements, substitutions and modifications belonging to the equivalent scope of the claims are all within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Antenna apparatus 10 Board | substrate 20 Ground part 21 Extension part 30 Antenna 30A 1st antenna element 30B 2nd antenna element 30C 3rd antenna element 30D 4th antenna element 40 Feeding points 50A and 50B Resonant circuit

Claims (10)

In an antenna device that mounts an antenna on a substrate,
A ground portion formed on the substrate;
A feeding point connected to the ground part and supplying power to the antenna;
One end to be a power feeding part is connected to the ground part through the feeding point, and the other end to be a grounding part is connected to the vicinity of the ground part to which the power feeding part is connected to form a loop shape, An antenna device comprising: an antenna in which a portion adjacent to a ground portion is formed in a meander shape.   The antenna device according to claim 1, wherein the ground portion includes a meander-shaped extending portion that extends corresponding to a portion of the antenna formed in the meander shape.   The loop-shaped antenna is connected to the ground part via the feeding point and extends in a first direction, and is connected to the first antenna element and orthogonal to the first direction. A second antenna element extending in a second direction, a third antenna element extending parallel to and opposed to the second antenna element in parallel with the first antenna element, and the second antenna element The antenna device according to claim 1, further comprising: a fourth antenna element formed in a meander shape facing the antenna element in parallel and extending in connection with the third antenna element.   A resonance circuit connected to an arbitrary position of the antenna and having a capacitive element and an inductive element connected in parallel to each other, the first frequency band and a second frequency band different from the first frequency band The antenna device according to any one of claims 1 to 3, wherein the antenna device corresponds to. A resonance circuit that is connected to an arbitrary position of the antenna and in which a capacitive element and an inductive element are connected in parallel with each other; a first resonance circuit and a second resonance circuit;
4. The antenna device according to claim 1, wherein the antenna device corresponds to a first frequency band and a second frequency band different from the first frequency band. 5.   The antenna device according to any one of claims 1 to 3, wherein a signal band transmitted and received by the antenna is a 2.4 GHz band.   The antenna device according to claim 4 or 5, wherein the first frequency band is a 2.4 GHz band, and the second frequency band is a 5 GHz band. In a method for miniaturizing an antenna device that mounts an antenna on a substrate,
One end of the antenna serving as a power feeding portion is connected to a ground portion formed on the substrate via a feeding point, and the other end serving as a grounding portion of the antenna is near the ground portion to which the power feeding portion is connected. A method for miniaturizing an antenna device, comprising: forming a loop shape by connection, and further forming a portion adjacent to the ground portion in a meander shape.   9. The method of downsizing an antenna device according to claim 8, wherein the ground portion is formed in a meander shape so as to correspond to a portion of the antenna formed in the meander shape.   A communication device comprising the antenna device according to any one of claims 1 to 7.

Images