JP2009246560A - Antenna device and radio communication apparatus with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna device and the like suitable for miniaturization by reducing the antenna device in size while securing a property of excellent isolation between two antenna elements. <P>SOLUTION: The antenna device comprises: a substrate 10 with a ground conductor pattern 11 formed on a surface thereof; at least two antenna elements 12, 13 mounted, while being spaced apart from each other, in a mounting region R1 where the ground conductor pattern 11 is not formed on the surface of the substrate 10; and an isolation element 21 which is mounted at a position between the two antenna elements 12, 13 in the mounting region R1 and of which the proximal end is electrically connected with the ground conductor pattern 11. The isolation element 21 is configured by including a linear conductor connected by a plurality of bent portions. Thus, a length Y21 of the mounting region R1 in a Y direction can be reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an antenna device including a plurality of antenna elements, and more particularly to an antenna device in which an isolation element is mounted between two antenna elements in a mounting region of a substrate.

  In recent years, in a wireless communication device for portable use, a configuration including a plurality of antenna elements is increasing in order to cope with diversity reception and multiple-input multiple-output (MIMO) technology. In such a wireless communication device, in order to avoid interference between two adjacent antenna elements, it is desirable to dispose them apart. However, due to the demand for miniaturization of the wireless communication apparatus, two adjacent antenna elements are arranged at a relatively close distance on the substrate, and as a result, degradation of antenna characteristics due to interference between the two becomes a problem. As a countermeasure, a configuration has been proposed in which an isolation element connected to the ground conductor pattern is provided between two antenna elements adjacent to each other on the substrate to ensure sufficient isolation between the antenna elements (for example, Patent Documents 1 and 2).

  FIG. 12 shows a configuration example employing the above-described conventional isolation element. In FIG. 12, the ground conductor pattern 101 is formed on the surface of the substrate 100 of the wireless communication apparatus, and two antenna elements 102 are provided in the mounting region R0 from the position 101 a at one end of the ground conductor pattern 101 to the tip position of the substrate 100. , 103 are implemented. The base ends of the antenna elements 102 and 103 are connected to the power supply lines 104 and 105, and the other ends of the power supply lines 104 and 105 are connected to a power supply point (not shown) of the wireless circuit. In the mounting region R0, an isolation element 106 whose base end side is connected to the ground conductor pattern 101 is mounted between the two antenna elements 102 and 103.

As shown in the lower part of FIG. 12, for the sake of convenience, the X direction and the Y direction are defined. In this case, the isolation element 106 has a T-shape in which a linear conductor having a length Xa in the X direction is connected to the tip of a linear conductor having a length Ya in the Y direction, the base end of which is connected to the ground conductor pattern 101. It has the shape of In order to ensure sufficient isolation characteristics by the T-shaped isolation element 106, the total line length from the base end connected to the ground conductor pattern 101 to the tip of the linear conductor in the X direction is used. It is necessary to adjust to about ¼ of the wavelength λ of the frequency band. In addition, if the isolation element 106 and the antenna elements 102 and 103 are close to each other, the isolation characteristic deteriorates.
JP 2006-74446 A JP 2006-108830 A

  However, in FIG. 12, when the line length of the isolation element 106 is adjusted to about ¼ of the wavelength λ using the general substrate 100 made of glass epoxy, a large arrangement space for the isolation element 106 is required. . Assuming that 2.4 GHz, which is common in a wireless LAN, is assumed as the frequency band used, for example, the size is adjusted to about Xa = 10 mm and Ya = 14 mm. Even if a small chip antenna or the like is adopted as the antenna elements 102 and 103, the area of the mounting region R0 must be increased by the arrangement space of the isolation element 106, which hinders downsizing of the antenna device. Was a problem.

  Therefore, the present invention has been made to solve these problems, and while ensuring good isolation characteristics between two adjacent antenna elements, an antenna device suitable for miniaturization by reducing the arrangement space And it aims at providing the radio | wireless communication apparatus provided with the same.

  In order to solve the above problems, an antenna device of the present invention is mounted separately from a substrate having a ground conductor pattern formed on a surface thereof and a mounting region on the surface of the substrate where the ground conductor pattern is not formed. And at least two antenna elements, and an isolation element that is mounted at a position sandwiched between the two adjacent antenna elements in the mounting region and has a base end electrically connected to the ground conductor pattern, The isolation element includes a linear conductor connected by a plurality of bent portions.

  According to the antenna device of the present invention, two antenna elements are arranged in the mounting region on the surface of the substrate, and an isolation element electrically connected to the ground conductor pattern is arranged between the antenna elements. Since this isolation element includes a linear conductor connected by a plurality of bent portions, it is possible to configure a long line length suitable for the wavelength without increasing the total length of the isolation element itself. Therefore, the mounting area can be reduced by the reduction in the size of the isolation element while ensuring good isolation characteristics, and the entire antenna device can be configured in a small size.

  In the present invention, the isolation element may include the meander-shaped linear conductor. In this case, the line width, interval, and line length of the meander-shaped linear conductor may be set so as to have a resonance pole with respect to the used frequency band.

  In the present invention, the linear conductor may be formed by a pattern portion protruding from one end of the ground conductor pattern.

  In the present invention, the isolation element may have a structure in which a conductor pattern corresponding to the linear conductor is formed in an inner layer of a dielectric substrate.

  In the present invention, the dielectric substrate may be a ceramic substrate and may have a dielectric constant higher than that of the substrate.

  In the present invention, a base end of the conductor pattern corresponding to the linear conductor may be electrically connected to the ground conductor pattern via a side electrode of the dielectric substrate.

  In the present invention, the isolation element and the two antenna elements may be formed using the dielectric substrate having a common structure.

  In order to solve the above-described problem, a wireless communication device of the present invention includes any one of the antenna devices described above.

  According to the present invention, the isolation element positioned between the two antenna elements includes a linear conductor (for example, a meander-shaped linear conductor) connected by a plurality of bent portions. Without increasing the overall length of the isolation element, it is possible to increase the line length of the linear conductor and obtain an isolation characteristic suitable for the operating frequency band. Therefore, when the conventional T-shaped isolation element is used, it is possible to configure the isolation element with a small size compared to the case where the dimensional design of the wavelength order is required, so that the mounting area can be reduced and the antenna device can be downsized. Can be realized. If the isolation element is formed using a separate dielectric substrate, the size of the isolation element can be further reduced due to the wavelength shortening effect, and a configuration suitable for downsizing of the antenna device can be realized. On the other hand, if the dimension of the linear conductor of the isolation element is appropriately set, a resonance peak can be provided in the used frequency band, and the isolation characteristics of the antenna device can be improved.

  Embodiments of the present invention will be described with reference to the drawings. Below, two embodiment which applied this invention with respect to the antenna apparatus mounted in the radio | wireless communication apparatus for portable uses is described.

[First Embodiment]
FIG. 1 is a diagram illustrating a schematic configuration of the antenna device according to the first embodiment. FIG. 1 shows a substrate 10 on which a wireless circuit of a wireless communication device is configured. As the substrate 10, for example, a glass epoxy substrate is used. A ground conductor pattern 11 connected to the ground potential is formed on the surface of the substrate 10, and a mounting region R <b> 1 extends from a position 11 a at one end of the ground conductor pattern 11 to a tip position of the substrate 10. As shown in the lower part of FIG. 1, the X direction and the Y direction are defined for convenience. In this case, the substrate 10 is formed in a rectangular shape having a length X10 in the X direction and a length Y10 in the Y direction, and the upper mounting region R1 has a length X10 in the X direction similar to the substrate 10 and a position 11a. It is a rectangle with a length Y11 in the upper Y direction.

  Two antenna elements 12 and 13 are mounted in the mounting region R1. These antenna elements 12 and 13 are chip antennas on which meandering conductor patterns are formed, and have a similar structure and symmetrical arrangement. The antenna elements 12 and 13 have base ends connected to the feed lines 14 and 15, and feed points (not shown) provided on the ground conductor pattern 11 side of the feed lines 14 and 15 are connected to the radio circuit. Yes. The tip portions of the antenna elements 12 and 13 are connected to lands 16 and 17 provided in the mounting region R1, respectively. For the antenna elements 12 and 13, for example, a multilayer ceramic substrate is used, and a meander-like conductor pattern is formed in the inner layer.

  The isolation element 20 is a conductor pattern that is disposed at a position sandwiched between the two antenna elements 12 and 13 in the central portion of the mounting region R1 and has a proximal end connected to the ground conductor pattern 11. The isolation element 20 is connected to the proximal end portion 20a protruding from the vicinity of the center of the position 11a of the ground conductor pattern 11, the linear conductor portion 20b connected to the proximal end portion 20a, and the distal end of the linear conductor portion 20b. The front end portion 20c is connected to be configured. Among these, the linear conductor portion 20b is formed as a meander-shaped linear conductor and has a line length capable of resonating in the used frequency band. The isolation element 20 plays a role of ensuring isolation between the two antenna elements 12 and 13 in the used frequency band.

  FIG. 2 is a plan view showing a detailed configuration of the isolation element 20. The isolation element 20 is formed in the range of the full width X12 in the X direction and the full length Y12 in the Y direction. In the Y direction, a proximal end portion 20a having a length Y13 and a distal end portion 20c having a length Y14 are connected to both ends of the meander-shaped linear conductor portion 20b of the isolation element 20, respectively. The linear conductor portion 20b has a structure in which linear conductors connected by a large number of bent portions are arranged with a line width L1 and an interval S1. In the linear conductor portion 20b, the total line length from the connection point with the base end portion 20a to the connection point with the tip end portion 20c is set sufficiently longer than the full length Y12. If the line width L1 and the interval S1 are set small, the total line length of the linear conductor portion 20b becomes long. However, considering the deterioration of the high frequency characteristics when adjacent linear conductors are extremely close to each other, an appropriate line It is desirable to set the width L1 and the interval S1.

  FIG. 3 shows S parameters of the antenna device of the first embodiment. In FIG. 3, the change in the frequency range of 1 to 4 GHz is plotted with respect to the S parameter S11 corresponding to the reflection characteristics of the antenna elements 12 and 13 and the S parameter S21 corresponding to the isolation characteristics between the antenna elements 12 and 13. is doing. Here, a frequency band of 2.4 GHz is assumed, and as parameters of the dimensions of the isolation element 20, X12 = 3 mm, Y12 = 10.65 mm, Y13 = 1.35 mm, Y14 = 0.7 mm, L1 = S1 = 0.22 mm.

  As shown in FIG. 3, in the use frequency band of 2.4 GHz, peaks of S11 and S21 occur, and values m1 and m2 are obtained. Of these, with respect to S21, it is possible to ensure isolation of about −25 to −30 dB in the vicinity of 2.4 GHz based mainly on the resonance pole generated according to the line length of the meander-shaped linear conductor 20b. it can. If isolation is secured at about −25 to −30, the coupling between the two antenna elements 12 and 13 can be suppressed, and good antenna characteristics can be maintained.

  As described above, in the first embodiment, by providing the isolation element 20 that is maintained at the same potential as the ground conductor pattern 11, the coupling of electromagnetic waves between the two adjacent antenna elements 12 and 13 is suppressed. Thus, the isolation characteristics can be improved. In this case, by appropriately adjusting the line length of the linear conductor portion 20b, it is possible to appropriately generate resonance with respect to the wavelength λ of the used frequency band and to realize an isolation characteristic having a peak in the used frequency band. it can. Here, since the line length of the meander-shaped linear conductor portion 20b can be set longer than the total length Y12 of the isolation element 20, the total length Y12 can be sufficiently shortened with respect to the wavelength λ. Accordingly, the size of the mounting region R1 can be reduced by an amount that can reduce the overall length Y12 relative to the case where a conventional T-shaped isolation element is mounted.

  The isolation element 20 of the first embodiment includes a base end portion 20a and a tip end portion 20c in addition to the linear conductor portion 20b, which correspond to the configuration of the second embodiment described later. However, the isolation element 20 may be configured by only the linear conductor portion 20b without providing the base end portion 20a and the tip end portion 20c. In this case, the total length Y12 of the isolation element 20 can be further shortened.

[Second Embodiment]
FIG. 4 is a diagram illustrating a schematic configuration of the antenna device according to the second embodiment. In FIG. 4, as in FIG. 1, a substrate 10 on which a wireless circuit of the wireless communication device is configured is shown, and a ground conductor pattern 11 is formed on the substrate 10, and a position of one end of the ground conductor pattern 11 is shown. From 11a to the tip position of the substrate 10 is a mounting region R1. Compared to the first embodiment, the structure of the substrate 10 is the same, but the size is slightly smaller. That is, the substrate 10 is formed in a rectangular shape having a length X20 in the X direction and a length Y20 in the Y direction, and the upper mounting region R1 is the same as the length X20 in the X direction as in the substrate 10 and from the position 11a. This is a rectangle with a length Y21 in the Y direction. Among these, the lengths Y20 and Y21 are shorter than the lengths Y10 and Y11 in the Y direction in FIG. 1, and the reason will be described later.

  Since the two antenna elements 12 and 13 mounted in the mounting region R1 are the same as those in the first embodiment, description thereof is omitted. On the other hand, an isolation element 21 is mounted at a position between the two antenna elements 12 and 13 in the central portion of the mounting region R1. Unlike the first embodiment, the isolation element 21 is formed using a multilayer ceramic substrate separate from the ground conductor pattern 11. The isolation element 21 has a base end portion 21a connected to the ground conductor pattern 11, a linear conductor portion 21b connected to the base end portion 21a, and a tip end portion 21c connected to the tip of the linear conductor portion 21b. Concatenated. The base end portion 21 a is connected to a land 22 near the center of the position 11 a of the ground conductor pattern 11. The linear conductor portion 21b is formed as a meander-shaped linear conductor in an inner layer of a ceramic substrate, which will be described later, and has a line length capable of resonating in the use frequency band. The role of the isolation element 21 of the second embodiment is the same as that of the first embodiment, and is to ensure isolation between the two antenna elements 12 and 13 in the used frequency band.

  A detailed structure of the isolation element 21 of FIG. 4 will be described with reference to FIGS. 5 and 6. FIG. 5 is a plan view showing the pattern configuration of the isolation element 21, and FIG. 6 is a cross-sectional structure diagram showing the structure of the isolation element 21 taken along the line aa (FIG. 5). The isolation element 21 is formed in a range of a full width X22 in the X direction and a full length Y22 in the Y direction. The meander-shaped linear conductor portion 21b has a structure in which linear conductors connected by a large number of bent portions are arranged with a line width L2 and an interval S2 within a range of a length X23 in the X direction. The total line length from the proximal end side to the distal end side of the linear conductor portion 21b is set sufficiently longer than the full length Y22.

  As shown in FIG. 6, the isolation element 21 is formed on a ceramic substrate having a predetermined dielectric constant and a thickness T. A conductor pattern of the linear conductor portion 21b is formed on the inner layer of the ceramic substrate. Side electrodes E1 and E2 are formed on the substrate of the isolation element 21, the proximal end side of the linear conductor portion 21b is connected to the side electrode E1, and the distal end side of the linear conductor portion 21b is connected to the side electrode E2. Conductor patterns P1 and P2 are formed on both ends of the back surface of the ceramic substrate, the side electrode E1 is connected to the conductor pattern P1, and the side electrode E2 is connected to the conductor pattern P2. The side electrode E1 and the conductor pattern P1 integrally function as the aforementioned base end portion 21a, and the side electrode E2 and the conductor pattern P2 integrally function as the aforementioned distal end portion 21c.

  FIG. 7 shows S parameters of the antenna device of the second embodiment. 7, as in FIG. 3, the S parameter S11 corresponding to the reflection characteristics of the antenna elements 12 and 13 and the S parameter S21 corresponding to the isolation characteristics between the antenna elements 12 and 13 have frequencies of 1 to 4 GHz. The change in range is plotted. Here, a frequency band of 2.4 GHz is assumed, and the dimensions of the isolation element 21 are X22 = 3 mm, X23 = 2.6 mm, Y22 = 8.33 mm, Y23 = 1.35 mm, Y24 = 0. .53 mm and L2 = S2 = 0.165 mm.

  As shown in FIG. 7, in the use frequency band of 2.4 GHz, respective peaks of S11 and S21 occur, and values m3 and m4 are obtained. Focusing on S21 in FIG. 7, compared with FIG. 3, a sharp peak reaching −40 dB appears at the resonance pole. Thus, in the configuration of the second embodiment, appropriate isolation can be ensured according to the line length of the meander-shaped linear conductor 20b configured on the ceramic substrate. Thereby, the coupling between the two antenna elements 12 and 13 can be sufficiently suppressed, and good antenna characteristics can be maintained.

  Here, FIG. 8 is a diagram comparing the isolation characteristics of the second embodiment with the isolation characteristics when a conventional T-shaped isolation element is used. FIG. 8 shows S21 in the case where the isolation element 21 is replaced with a T-shape and other conditions are set in common with S21 in FIG. In the case of S21 in the case of the second embodiment, a resonance peak occurs in the used frequency band of 2.4 GHz, whereas in the conventional configuration, S21 does not cause a resonance peak in the used frequency band of 2.4 GHz. It changes gently in the range of 20 to -25 dB. Therefore, configuring the meander-shaped linear conductor portion 20b has the effect of sharpening the resonance peak in the operating frequency band, thereby improving the isolation characteristics.

  As described above, in the second embodiment, by providing the isolation element 21 that is maintained at the same potential as that of the ground conductor pattern 11, the coupling of electromagnetic waves between the two adjacent antenna elements 12 and 13 is suppressed. Thus, the isolation characteristics can be improved. In this case, due to the wavelength shortening effect based on the dielectric constant of the ceramic substrate on which the isolation element 21 is formed, even if the linear conductor portion 21b is adjusted to a shorter line length, it resonates with respect to the wavelength λ in the used frequency band. be able to. Therefore, the isolation element 21 of the second embodiment can realize the same isolation characteristic with a shorter line length than the isolation element 20 of the first embodiment. Therefore, the size of the mounting region R1 can be further reduced by an amount that can reduce the overall length Y22, which is suitable for downsizing of the antenna device. On the other hand, since the structure of the isolation element 21 is the same as that of the antenna elements 12 and 13, if the isolation element 21 is mounted on the substrate 10 together with the antenna elements 12 and 13 in the manufacturing process, the manufacturing process is not complicated. can do.

  Next, in the first and second embodiments, the relationship between the dimensional parameters of the isolation elements 20 and 21 and the isolation characteristics will be described. FIG. 9 shows the result of the S parameter obtained by simulation when the parameter setting of the dimensions of the isolation elements 20 and 21 of the first and second embodiments is changed. In FIG. 9, the total lengths Y12 and Y22 of the isolation elements 20 and 21 are changed within a range of 6 mm to 11.5 mm, and the lines of the linear conductor portions 20b and 21b are adapted to the use frequency band for each. The widths L1 and L2 and the intervals S1 and S2 are adjusted. In addition, the total line lengths M1 and M2 of the linear conductor portions 20b and 21b are shown corresponding to the respective settings. When the dimensional parameters are common with respect to the first and second embodiments, the S parameters S11 and S12 are calculated by simulation.

  FIG. 10 shows the relationship between the total lengths Y12 and Y22 and the S parameter S21 (isolation characteristics) among the results of FIG. First, in the case of the first embodiment, the peak of S21 appears in the range where the total length Y12 of the isolation element 20 is 10 to 11 mm. On the other hand, in the case of the second embodiment, the peak of S21 appears when the total length Y22 of the isolation element 21 is in the range of 8 to 9 mm. In the configurations of the first and second embodiments, the effect of adopting the meander-like linear conductors 20b and 21b is common, but in the case of the configuration of the second embodiment, a ceramic substrate having a relatively high dielectric constant. It was confirmed that the total length Y22 can be shortened because of the effect of shortening the wavelength due to the use of.

  Next, in the second embodiment, parameters including the dimensions of the isolation element 21 were optimized, and further shortening of the total length Y12 was verified by simulation. As a result, parameters for the isolation element 21 were set to Y22 = 7 mm, X22 = 3 mm, X23 = 2.6 mm, L2 = S2 = 0.075 mm, and the relative dielectric constant εr = 7.6 of the ceramic substrate. Sometimes good isolation characteristics were obtained. FIG. 11 shows S parameters of the antenna apparatus of the second embodiment corresponding to the parameters optimized in this way.

  In FIG. 11, changes in the S parameters S11 and S21 of the antenna elements 12 and 13 are plotted under the same frequency conditions as in FIG. The resonance peak of the S parameter S21 that reaches −60 dB occurs in the vicinity of the used frequency band of 2.4 GHz, and good isolation characteristics can be ensured. Thus, in the configuration of the second embodiment, it was confirmed that the total length Y22 of the isolation element can be shortened to about 7 mm. In this case, the length of the region R1 of the substrate 10 in the Y direction can be set to be slightly over 7 mm. Therefore, the size of the substrate 10 can be greatly reduced as compared with the case where a conventional T-shaped isolation element is employed.

  The contents of the present invention have been specifically described above based on the two embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. it can. For example, in each of the above-described embodiments, the case where the present invention is applied to the configuration including the two antenna elements 12 and 13 has been described. The present invention can be applied to a configuration in which the isolation elements 20 and 21 are arranged between two antenna elements. In each of the above embodiments, the case where the present invention is applied to the configuration using the chip antenna as the antenna elements 12 and 13 has been described. However, various antenna elements having a structure that can be arranged in the mounting region R1 are used. Even so, the present invention can be applied. Furthermore, in each of the above embodiments, the case where the isolation elements 20 and 21 include meander-shaped linear conductor portions 20b and 21b has been described. Various linear conductor portions may be formed.

It is a figure which shows schematic structure of the antenna device of 1st Embodiment. It is a top view which shows the detailed structure of the isolation element 20 of FIG. It is a figure which shows S parameter of the antenna device of 1st Embodiment. It is a figure which shows schematic structure of the antenna device of 2nd Embodiment. FIG. 5 is a plan view showing a pattern configuration of the isolation element 21 of FIG. 4. FIG. 6 is a cross-sectional structure diagram illustrating a structure of an aa cross section of the isolation element 21 of FIG. 5. It is a figure which shows the S parameter of the antenna device of 2nd Embodiment. It is the figure which compared the isolation characteristic of 2nd Embodiment with the isolation characteristic in the case of using the conventional T-shaped isolation element. It is a figure which shows S parameter at the time of changing the setting of the parameter of the dimension of the isolation elements 20 and 21 of 1st and 2nd embodiment. It is a figure which shows the relationship between full length Y12, Y22 and S parameter S21 among the results of FIG. It is a figure which shows S parameter of the antenna apparatus corresponding to the parameter optimized in 2nd Embodiment. It is a figure which shows the structural example which employ | adopted the conventional isolation element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Board | substrate 11 ... Grounding conductor pattern 12, 13 ... Antenna element 14, 15 ... Feed line 16, 17, 22 ... Land 20, 21 ... Isolation element R1 ... Area | region E1, E2 ... Side electrode P1, P2 ... Conductor pattern

Claims (9)

A substrate having a ground conductor pattern formed on the surface;
In the mounting area where the ground conductor pattern is not formed on the surface of the substrate, at least two antenna elements mounted separately from each other;
In the mounting region, an isolation element mounted at a position sandwiched between the two antenna elements adjacent to each other and having a base end electrically connected to the ground conductor pattern;
With
The said isolation element is comprised including the linear conductor connected by the some bending part, The antenna device characterized by the above-mentioned.   The antenna device according to claim 1, wherein the isolation element includes the meandering linear conductor.   The antenna device according to claim 2, wherein the meandering linear conductor has a line width, interval, and line length that are set to have resonance poles with respect to a used frequency band.   The antenna device according to claim 1, wherein the linear conductor is formed by a pattern portion protruding from one end of the ground conductor pattern.   The antenna device according to claim 1, wherein the isolation element has a structure in which a conductor pattern corresponding to the linear conductor is formed in an inner layer of a dielectric substrate.   The antenna device according to claim 5, wherein the dielectric substrate is a ceramic substrate and has a dielectric constant higher than a dielectric constant of the substrate.   6. The antenna device according to claim 5, wherein a base end of the conductor pattern corresponding to the linear conductor is electrically connected to the ground conductor pattern via a side electrode of the dielectric substrate.   The antenna device according to claim 5, wherein the isolation element and the two antenna elements are formed using the dielectric substrate having a common structure. A wireless communication device comprising the antenna device according to claim 1.

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