JP2013093660A - Dual band antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dual band antenna with a small occupied area.SOLUTION: The dual band antenna has: a ground pattern formed on an insulation substrate to have an opening; a conductive pattern for a first frequency band formed in the opening of the ground pattern; and a capacity coupling type chip antenna for a second frequency band having first and second external electrodes. Then, the first external electrode of the chip antenna is connected to the ground pattern, and the second external electrode of the chip antenna is connected to the conductive pattern. Furthermore, power is supplied to the chip antenna via the conductive pattern.

Description

  The present invention relates to a dual-band antenna.

  Recently, portable devices are required to be miniaturized and multifunctional, and the number of components is being reduced. However, wireless components are also required to be reduced in size and the number of components. Among them, IC (Integrated Circuit) chips related to radio have appeared that incorporate a plurality of radio standard functions in one chip. There are already four-band IC chips for mobile phones, but recently there are similar movements in fields other than mobile phones. Specifically, GPS (Global Positioing System) and Bluetooth (registered trademark), 2.4 GHz band wireless LAN (Local Area Network), and 5 GHz band wireless LAN combo ICs have been developed. Accordingly, a multi-resonant antenna corresponding to a plurality of frequency bands is also required.

  For example, in Japanese Patent Laid-Open No. 2002-319811, a feed exciter and a non-feed exciter are individually configured in order to create a multiple resonance antenna having a large electrical volume. The feed exciter and the non-feed exciter are coupled to each other by electric field coupling means provided separately. With this configuration, it is not necessary to configure the entire multi-resonant antenna on a single dielectric substrate. Specifically, each of the feed exciter and the parasitic exciter is composed of a dielectric substrate, and an electric field coupling means is formed on a normal circuit board, and the feed exciter, the parasitic exciter and the electric field coupling are formed on the circuit board. Connect means. If the power feeding exciter and the non-feeding exciter are formed of a dielectric base, the size can be reduced, but no other ingenuity for reducing the size can be seen.

JP 2002-319811 A

  Accordingly, an object of the present invention is to provide a novel dual-band antenna that occupies a small area.

  The dual-band antenna according to the present invention includes (A) a ground pattern formed on an insulating substrate so as to have an opening, and (B) a second pattern formed on the insulating substrate in the opening of the ground pattern. A conductive pattern for one frequency band, and (C) a capacitively coupled chip antenna for the second frequency band having first and second external electrodes. The first external electrode of the chip antenna is connected to the ground pattern, and the second external electrode of the chip antenna is connected to the conductive pattern. Further, the chip antenna is fed with power through the conductive pattern.

  By adopting such a configuration, since the conductive pattern also acts as a ground pattern of the chip antenna, the region on the insulating substrate can be effectively used, and the overall size can be reduced.

  In the case where the first external electrode and the second external electrode described above are provided in the direction in which the chip antenna faces, the conductive pattern described above is connected from the first external electrode to the second external electrode. It may be formed to extend in the direction toward the electrode. In this way, the chip antenna and at least a part of the conductive pattern are arranged on a straight line, and the characteristics of the chip antenna can be improved efficiently.

  Furthermore, the conductive pattern described above may have a length for realizing the first frequency band. The length is adjusted to realize the first frequency band while making the characteristics of the chip antenna favorable.

  Furthermore, if the conductive pattern described above is bent or has a meander structure, further space saving can be achieved and desired characteristics can be obtained.

  Moreover, you may make it the opening part described above have an opening of 2 directions. In this way, when provided on the corner of the insulating substrate, even if the user holds the portable device mounted with the dual-band antenna by hand, it is possible to suppress the occupied area on the insulating substrate while effectively suppressing the characteristic deterioration. it can.

  Moreover, you may make it further have the 2nd conductive pattern which connects the conductive pattern mentioned above and a ground pattern. Thereby, impedance matching is realized without separately preparing an inductor and a capacitor.

  According to the present invention, a dual band antenna with a small occupied area is realized.

FIG. 1 is a top view of a dual-band antenna according to the first embodiment. FIG. 2 is a diagram for explaining the outer shape of the chip antenna. FIG. 3 is a diagram illustrating the frequency characteristics of VSWR in the vicinity of 2.4 GHz. FIG. 4 is a diagram illustrating the frequency characteristics of VSWR in the vicinity of 5 GHz. FIG. 5 is a diagram illustrating an example when a part of the conductive pattern is deleted. FIG. 6 is a diagram illustrating a modified example of the dual-band antenna in the first embodiment. FIG. 7 is a diagram illustrating a modification of the dual-band antenna according to the first embodiment. FIG. 8 is a diagram illustrating a modification of the dual band antenna according to the first embodiment. FIG. 9 is a diagram illustrating a modification of the dual band antenna according to the first embodiment. FIG. 10 is a top view of the dual-band antenna according to the second embodiment. FIG. 11 is a diagram illustrating a configuration example of the antenna when the length L21 of the radiating unit is 0 mm. FIG. 12 is a diagram illustrating a configuration example of the antenna when the length L21 of the radiating portion is 5 mm. FIG. 13 is a diagram illustrating a configuration example of the antenna when the length L21 of the radiating portion is 9 mm. FIG. 14 is a diagram illustrating a configuration example of an antenna in the case where the length L21 of the radiating portion is 11 mm. FIG. 15 is a diagram illustrating the frequency characteristics of VSWR in the vicinity of 2.4 GHz in the second embodiment. FIG. 16 is a diagram illustrating the relationship between the length L21 of the radiating portion and the bandwidth. FIG. 17 is a diagram illustrating frequency characteristics of VSWR in the vicinity of 5 GHz according to the second embodiment.

[Embodiment 1]
FIG. 1 shows a top view of a dual band antenna according to a first embodiment of the present invention.

  It may be preferable to place the antenna at the corner of the portable device so that it is not covered with the hand when the portable device with the antenna is held by hand. On the other hand, when a chip antenna having a strong capacitive coupling is generally adopted, the area occupied on the substrate can be reduced. However, the band tends to be narrowed, and the performance is degraded when it is arranged at the corner of the substrate. It has been. If such problems are solved and an antenna, particularly a dual-band antenna, is arranged at the corner of the board, not only can the miniaturization of the portable device be promoted, but the antenna performance can be maintained in a normal usage mode of the portable device.

  Therefore, as shown in FIG. 1, a ground pattern 2 is formed on an insulating substrate having a length L2 (for example, 20 mm) and a width L1 (for example, 35 mm), and a length L4 (for example, 13 mm) is formed on the upper side in the upper right of the ground pattern 2. In addition, a cutout portion having two-direction openings having a length L3 (for example, 5 mm) is provided on the right side. The notch portion has a capacitively coupled chip antenna 3 for a low frequency band, a conductive pattern 5 for a high frequency band, and a feeding point 4 for feeding power to the chip antenna 3 and the conductive pattern 5. A power supply pattern 6 and a conductive pattern 7 connecting the conductive pattern 5 and the ground pattern 2 are provided.

  As described above, in the present embodiment, when the dual band antenna is formed in the upper right corner, the capacitively coupled chip antenna 3 for the low frequency band is arranged on the left side in the cutout, while the conductive is on the right side. An inverted F-type antenna having a pattern 5, a feeding pattern 6, and a conductive pattern 7 is arranged. More specifically, the chip antenna 3 is arranged near the center of the upper side of the insulating substrate 1, while the tip portion of the inverted F-type antenna is arranged near the upper right corner of the insulating substrate 1. The conductive pattern 5 extends in the longitudinal direction of the chip antenna 3, and the length of the conductive pattern 5 is determined in accordance with a target frequency band.

  By adopting such an arrangement, the conductive pattern 5 for the high frequency band functions like a ground pattern with a long electric length as viewed from the chip antenna 3 for the low frequency band. Will improve. Originally, it is preferable to provide a conductive pattern having a length of ¼ of the wavelength λ of the target frequency on both sides of the capacitively coupled chip antenna 3, so that the chip antenna 3 is placed toward the corner of the insulating substrate 1. When placed, the characteristics deteriorated. However, if the conductive pattern 5 is arranged in this way, the conductive pattern 5 not only functions as an antenna element for the original frequency band, but also functions as a ground pattern for the antenna in the low frequency band. The area on the insulating substrate 1 is effectively utilized for the area occupied by the pattern 5, thereby reducing the size of the entire dual-band antenna.

  The chip antenna 3 has a shape as shown in FIG. 2, for example. The chip antenna 3 is a rectangular parallelepiped, and has, for example, a first external electrode 31 on a part of the left side and a part of the bottom, and a second external electrode 32 on a part of the right side and a part of the bottom. ing. Since the chip antenna 3 itself may be an existing one, the description of the internal structure is omitted. Further, for example, the first external electrode 31 is in contact with a land provided at the end of the ground pattern 2 so as to be conductive with solder or the like. On the other hand, the second external electrode 32 is in contact with a land provided at the left end of the conductive pattern 5 so as to be conductive by solder or the like. As a result, the chip antenna 3 is fed through the feeding pattern 6 and a part of the conductive pattern 5.

  In this way, the chip antenna 3 is arranged between the ground pattern 2 and the conductive pattern 5, and the conductive pattern 5 is directed in the direction from the first external electrode 31 connected to the ground pattern 2 to the second external electrode 32. Is stretched. However, the front end portion of the conductive pattern 5 may be bent mainly due to the space.

  Here, it is assumed that the chip antenna 3 is in charge of the 2.4 GHz band in the wireless LAN, and the conductive pattern 5 is in charge of the 5 GHz band in the wireless LAN. However, it is not limited to such a combination.

  Next, the characteristics of the dual-band antenna shown in FIG. 1 will be described with reference to FIGS. FIG. 3 shows the frequency characteristics of the VSWR in the vicinity of 2.4 GHz of the dual band antenna. In FIG. 3, the horizontal axis represents frequency, and the vertical axis represents VSWR (Vertical Standing Wave Ratio). Here, the solid curve represents the frequency characteristics of the dual band antenna shown in FIG. 1 in the vicinity of 2.4 GHz. For example, looking at the bandwidth W1 where VSWR is 3.0 or less, it can be seen that the bandwidth is approximately 160 MHz.

  FIG. 4 shows the frequency characteristics of VSWR in the vicinity of 5 GHz of the dual band antenna shown in FIG. Thus, also in FIG. 4, the horizontal axis represents frequency and the vertical axis represents VSWR. As can be seen from FIG. 4, in the vicinity of 5 GHz, the bandwidth with a VSWR of 3.0 or less is 1 GHz or more, which indicates that the bandwidth is sufficiently wide.

  Here, the influence of the conductive pattern 5 on the chip antenna 3 will be considered. At this time, as shown in FIG. 5, the characteristic when the conductive pattern 5 is removed along the right end of the power feeding pattern 6 is represented by a dotted line curve in FIG. Not only the entire curve has shifted to a higher frequency, but the bandwidth W2 with a VSWR of 3.0 or less is approximately 120 MHz, which is narrower than W1. Thus, it can be seen that the provision of the conductive pattern 5 improves the characteristics in the low frequency band.

  The shape shown in FIG. 1 is an example, and various modifications are possible. For example, you may make it employ | adopt a structure as shown in FIG. In the example of FIG. 6, the opening in two directions is the same in the ground pattern 2b, but the shape of the notch is not rectangular. In this way, the lateral length of the opening is set to L12 (for example, 10 mm), and when the length is made shorter than L4 in FIG. 1, the length L11 (for example, 8 mm) of the right opening is set to FIG. A space is formed in the tip direction of the conductive pattern 5b so as to be longer than L3 and L13 (for example, 5 mm). That is, since the conductive pattern 5b has a shorter length in the longitudinal direction of the notch, the conductive pattern 5b is bent in the middle so that its tip faces downward. The power supply pattern 6b having the power supply point 4b at the tip is also bent, and the shape of the conductive pattern 7b is adjusted.

  Furthermore, in order to lower the target high frequency band, the length of the conductive pattern 5 is lengthened. For this purpose, in FIG. 7, the conductive pattern 5 is modified to have a meander structure. Is also possible. In the example of FIG. 7, a rectangular notch is formed at the corner of the ground pattern 2c, and the capacitively coupled chip antenna 3 for the low frequency band and the tip near the corner are meandered in the notch. A conductive pattern 5c having a structure, a power supply pattern 6c having a power supply point 4c, and a conductive pattern 7c connecting the conductive pattern 5c and the ground pattern 2c are arranged. Due to the meander structure, the electrical length of the conductive pattern 5c is long, and the target high frequency band is lowered.

  Moreover, although the example which provides a dual band antenna in the upper right corner of the insulated substrate 1 was shown, you may make it provide in an upper left corner as shown in FIG. In this case, an arrangement like the mirror image of FIG. 1 may be employed.

  Furthermore, it does not necessarily have to be arranged at the corner of the insulating substrate 1. For example, as shown in FIG. 9, the ground pattern 2d on the insulating substrate 1 is provided with a cutout so as to have an opening only in the direction of the upper side. That is, a part of the ground pattern 2 d is formed on the right side portion of the insulating substrate 1. Other configurations are the same as those of the dual-band antenna of FIG. 1, and the same operational effects can be obtained.

[Embodiment 2]
In the first embodiment, an inverted F antenna is used for the high frequency band, but an antenna that is not an inverted F antenna can also be used. For example, as shown in FIG. 10, a ground pattern 2e is provided on the insulating substrate 1, and a notch is formed in the upper right corner portion of the ground pattern 2e so as to provide openings in two directions of the upper side and the right side. This point is the same as in the first embodiment. However, the ground pattern 2e is provided with a protrusion 17 in order to connect an element for impedance matching so that the power feeding pattern and the ground pattern 2e can be conducted. L1 to L3 are the same as those in the first embodiment.

  A conductive pattern 21 having a capacitively coupled chip antenna 3 for a low frequency band, a power supply unit 18 for a connection part to the chip antenna 3 and a radiating unit 15 for a high frequency band at a notch, and a tip Is a first element for impedance matching that connects the first power supply pattern 23, the second power supply pattern 16, and the first power supply pattern 23 and the second power supply pattern 16. 20 and a second element 19 for impedance matching that connects the protrusion 17 of the ground pattern 2e and the first power supply pattern 23 are arranged to constitute a dual-band antenna.

  The first element 20 and the second element 19 are inductors or capacitors used for impedance matching. Thus, instead of the conductive pattern 7 in the first embodiment, impedance matching is realized by the first element 20 and the second element 19.

  As described above, in the present embodiment, when the dual band antenna is formed in the upper right corner of the insulating substrate 1, the capacitively coupled chip antenna 3 for the low frequency band is disposed on the left side in the notch portion. A T-type antenna having a conductive pattern 21 is arranged on the right side. More specifically, the chip antenna 3 is disposed near the center of the upper side of the insulating substrate 1, while the right tip portion of the T-shaped antenna is disposed near the upper right corner of the insulating substrate 1. The radiating portion 15 of the conductive pattern 21 extends in the longitudinal direction of the chip antenna 3, and the length L21 of the radiating portion 15 is determined in accordance with a target frequency band. For example, when the chip antenna 3 is in charge of the 2.4 GHz band and the conductive pattern 21 is in charge of the 5 GHz band, L21 is preferably approximately 7 mm.

  By adopting such an arrangement, the power supply unit 18 and the radiation unit 15 function like a ground pattern with a long electric length as viewed from the chip antenna 3 for the low frequency band. improves. If the radiating unit 15 is arranged in this way, the radiating unit 15 not only functions as an antenna element for the original frequency band, but also functions as a ground pattern for the antenna in the low frequency band. The area of the insulating substrate 1 is effectively utilized for the area occupied by the portion 15, and the entire dual band antenna is reduced in size.

  Next, how the length L21 of the radiating unit 15 affects the characteristics of the dual-band antenna will be described with reference to FIGS. First, when the length L21 of the radiating portion 15 of the conductive pattern 21 shown in FIG. 11 is 0 mm, the length L21 of the radiating portion 15 of the conductive pattern 21 shown in FIG. When the length L21 of the radiation portion 15 of the pattern 21 is 9 mm, the frequency characteristics are compared with respect to the case where the length L21 of the radiation portion 15 of the conductive pattern 21 is 11 mm shown in FIG. When L21 = 9 mm, the distal end of the radiating portion 15 is bent. When L21 = 11 mm, the distal end of the radiating portion 15 is bent and also has a folding back toward the chip antenna 3 side.

  FIG. 15 shows the frequency characteristics of VSWR in the vicinity of 2.4 GHz. When the length L21 of the radiating portion 15 changes from 0 to 11 mm, the approximate frequency band is almost the same, but when comparing the bandwidth with VSWR = 3.0 as a reference, the band is greatly increased when L21 = 0 mm. It can be seen that the width is narrow, and the width is narrow even when L21 = 5 mm. If L21 = 7 mm or more, a sufficient bandwidth can be secured.

  More specifically, FIG. 16 is a graph showing the relationship between L21 and bandwidth. According to FIG. 16, as L21 increases, the bandwidth at VSWR = 3.0 becomes wider. When L21 = 0 mm, the bandwidth is 85 MHz, whereas when L21 = 7 mm, the bandwidth is 95 MHz. , Approximately 12% wider. Thus, it can be seen that the radiating unit 15 effectively acts on the characteristics of the low frequency band.

  On the other hand, the length L21 of the radiating portion 15 acts to shift the target frequency. FIG. 17 shows the frequency characteristics of VSWR in the vicinity of 5 GHz. Thus, the shorter the L21, the higher the band, and the longer L21, the lower the band. It can be seen that L21 = 7 mm is appropriate when used as a 5 GHz band antenna.

  Although not shown, as described in the first embodiment, the insulating substrate 1 may be provided not at the upper right corner but at the upper left corner, or may be arranged at a non-corner portion with a single opening. May be.

  In the second embodiment, the characteristics can be adjusted not only for the wireless LAN but also for other uses such as GPS and Bluetooth.

  Although the embodiment of the present invention has been described above, the present invention is not limited to this. For example, the shape of the connecting portion between the power feeding pattern 6 and the conductive pattern 5 is also arbitrary and can be adjusted according to desired characteristics. Further, FIG. 2 shows an example in which the external electrodes of the chip antenna 3 are provided on a part of the side surface and a part of the bottom surface, but it may be provided on the entire right side surface and the entire left side surface. . In the present embodiment, since the chip antenna 3 is arranged so as to connect the ground pattern 2 and the conductive pattern 5, it is preferable that external electrodes are provided at both ends of the chip antenna 3. An external electrode may be provided.

DESCRIPTION OF SYMBOLS 1 Insulation board | substrate 2-2e Ground pattern 3 Chip antenna 4 Feeding point 5 Conductive pattern 6 Feeding pattern 7 Conductive pattern 15 Radiation part 16 Feeding pattern 17 Protrusion part 18 Feeding part 19,20 Element 21 Conductive pattern 23 Feeding pattern 22 Feeding point

Claims (6)

A ground pattern formed on the insulating substrate so as to have an opening; and
A conductive pattern for the first frequency band formed in the opening of the ground pattern on the insulating substrate;
A capacitively coupled chip antenna for the second frequency band having first and second external electrodes;
Have
The first external electrode of the chip antenna is connected to the ground pattern;
The second external electrode of the chip antenna is connected to the conductive pattern;
The chip antenna is a dual-band antenna that is fed through the conductive pattern. The first external electrode and the second external electrode are provided in the facing direction of the chip antenna;
The dual-band antenna according to claim 1, wherein the conductive pattern extends in a direction from the first external electrode to the second external electrode. The dual-band antenna according to claim 1, wherein the conductive pattern has a length for realizing the first frequency band. The dual-band antenna according to claim 1, wherein the conductive pattern is bent or has a meander structure. The dual-band antenna according to any one of claims 1 to 4, wherein the opening is open in two directions. The dual-band antenna according to claim 1, further comprising a second conductive pattern that connects the conductive pattern and the ground pattern.

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