JP2008022123A - Antenna device - Google Patents

Abstract

To provide a new and improved antenna device capable of changing directivity with a simple configuration and improving communication capacity.
A power supply terminal is provided at a position that is spaced from the end face 10a of the circuit board 10 by the same distance along one surface and the other surface of the circuit board 10 and that has a plane symmetry relationship via the circuit board 10. The first and second antenna elements 22 and 24, and power supply control means for selectively supplying power to one or both of the first and second antenna elements 22 and 24. A conductor region serving as a radio wave reflector is formed or built in the region reaching the arrangement position. When the power feeding control unit feeds power to both the first and second antenna elements 22 and 24, the first and second The radio waves radiated from the antenna elements 22 and 24 are combined and have directivity toward the end face of the circuit board 10.
[Selection] Figure 1

Description

  The present invention relates to an antenna device, and is particularly suitable for application to an antenna device used in a multiple-input multiple-output communication system.

  Recently, a wireless communication system of multiple input multiple output (MIMO) has been attracting attention. In the MIMO system, a plurality of antennas are provided on both the transmission side and the reception side, and a multi-input multi-output system via a radio propagation path is configured.

  In an antenna used in the MIMO scheme, in order to transmit and receive more information, it is necessary to increase the communication capacity, and it is necessary to optimally control the directivity of radio waves. As a technique for changing the directivity, for example, Japanese Patent Application Laid-Open No. 2002-185235 discloses a configuration in which a plurality of microstrip radiation elements are arranged in a dielectric and elements in a direction in which directivity is desired are connected by a switch. Yes.

  Japanese Patent Laying-Open No. 2005-45351 discloses a configuration in which patch antennas are arranged on both sides of a PC card and the patch antennas are selected in order to improve the communication status.

JP 2002-185235 A JP-A-2005-45351

  However, it is necessary to dynamically change the directivity for the purpose of improving the communication capacity. In the method of switching a large number of elements with a switch as described in Japanese Patent Laid-Open No. 2002-185235, the structure of the antenna is There is a problem of complexity. In addition, when a plurality of antennas are provided, the antenna interval is required to be about 0.5λ (λ is the wavelength of the transmission radio wave) in order to ensure the directivity of each antenna. There is.

  Further, as described in Japanese Patent Application Laid-Open No. 2005-45351, the method of arranging two antennas on both surfaces of a PC card limits directivity, and thus directs all possible directions. Therefore, it is difficult to secure a sufficient communication capacity in the entire communication direction.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a novel configuration capable of changing directivity with a simple configuration and improving communication capacity. Another object of the present invention is to provide an improved antenna device.

  In order to solve the above-described problem, according to one aspect of the present invention, a plane substrate is spaced apart from the end surface of the circuit board by the same distance along one surface and the other surface of the circuit board, and a plane symmetry relationship is established via the circuit board. First and second antenna elements each having a power supply terminal at a position thereof, and power supply control means for selectively supplying power to one or both of the first and second antenna elements, A conductor region serving as a radio wave reflector is formed or built in a region from the end face to the position where each of the feeding terminals is disposed, and the feeding control unit feeds both the first and second antenna elements. At this time, the radio waves radiated from the first and second antenna elements are combined to provide an antenna device having directivity in the end face direction of the circuit board.

  According to the above configuration, the first and second antenna elements are separated from the end surface of the circuit board by the same distance along one surface and the other surface of the circuit board, and the first and second antenna elements are not connected to the first and second antenna elements. A power supply terminal is provided at each position having a plane symmetry via the circuit board. The power supply control unit selectively supplies power to one or both of the first and second antenna elements. A conductor region serving as a radio wave reflector is formed or built in an area from the end face of the circuit board to the position where each feed terminal is arranged, and the feed control means feeds power to both the first and second antenna elements. Then, the radio waves radiated from the first and second antenna elements are combined and have directivity in the end face direction of the circuit board. Therefore, it is possible to radiate radio waves having directivity toward the end face of the circuit board.

  In addition, the distance from the end face of the circuit board to the position where each of the feeding terminals is arranged may be 0.15λ or less, where λ is the wavelength of the radio wave radiated from the first and second antenna elements. Good. According to this configuration, when the power feeding control unit feeds power to both the first and second antenna elements, radio waves can be reliably radiated in the direction of the end face of the circuit board.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the antenna apparatus which can change directivity with a simple structure and can improve communication capacity.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  FIG. 1 is a perspective view showing an antenna apparatus according to an embodiment of the present invention. The antenna device shown in FIG. 1 is configured by an offset T-type monopole antenna. As shown in FIG. 1, the antenna device includes a circuit board 10, an antenna 20 provided on the circuit board 10, and an antenna 30.

  The antenna device of this embodiment is mounted on a terminal such as a mobile phone, for example, and performs communication by the MIMO method using the antenna 20 and the antenna 30.

  The circuit board 10 is provided inside a terminal such as a mobile phone. On the circuit board 10, electronic devices such as a chip for causing the terminal to function are mounted. In the present embodiment, a single substrate is illustrated as the circuit substrate 10, but a multilayer substrate may be used.

  The antenna 20 includes an antenna element 22 and an antenna element 24. The antenna element 30 includes an antenna element 32 and an antenna element 34. Each of the element 22, the element 24, the element 32, and the element 34 is made of a metal having a low resistance such as copper or gold.

  As shown in FIG. 1, the antenna 20 is provided along the outer edge (side 10 a) of one end of the circuit board 10, and the antenna 30 is provided along the outer edge (side 10 b) of the other end of the circuit board 10. ing. The elements 22 and 24 of the antenna 20 and the elements 32 and 34 of the antenna 30 are all provided in the plane of the circuit board 10 (inside the outer edge). The elements 22, 24, 32, and 34 are opposed to the surface of the circuit board 10 and are separated from the surface of the circuit board 10 by a predetermined distance.

  Power is supplied to the element 22 from the circuit board 10 through the power supply unit 22a. The power feeding unit 22a is a part where the element 22 and the circuit board 10 are connected, and is located at a position offset from the intermediate position in the longitudinal direction with respect to the element 22 extending in the vertical direction. Here, the element 22 is configured to generate a vertically polarized wave and radiate a wide directivity wave having an isotropic pattern when power is supplied in the absence of the circuit board 10. .

  Similarly, power is supplied to the element 24 from the circuit board 10 via the power supply unit 24a. The power feeding part 24a is a part where the element 22 and the circuit board 10 are connected, and is located at a position offset from the intermediate position in the longitudinal direction with respect to the element 24 extending in the vertical direction. The element 24 is configured to generate vertically polarized waves and radiate wide directivity waves having an isotropic pattern when power is supplied in the absence of the circuit board 10.

  Similarly, power is supplied to the elements 32 and 34 from the power supply unit. The power supply to each element 22, 24, 32, 34 is controlled by a power supply control unit. The power supply control unit is provided, for example, on a chip mounted on the circuit board 10.

  In the present embodiment, the elements 22, 24, 32, and 34 and the power feeding units 22a, 24a, 32a, and 34a are arranged in the plane of the circuit board 10, but the power feeding units 22a, 24a, 32a, 34 a may be disposed in the plane of the circuit board 10, and the elements 22, 24, 32, and 34 may be partially outside the circuit board 10.

  The antenna 30 is configured similarly to the antenna 20. For this reason, in the following description, the antenna 20 will be described in detail.

  The antenna device of this embodiment is mounted on an APS (Antenna pattern selection) system in order to improve communication capacity. In the APS system, the directivity (beam pattern) of the antenna 20 and the antenna 30 is controlled to a state optimal for the communication environment.

  FIG. 2 is a schematic diagram showing the directivity required in the APS method. In FIG. 2, for convenience, a region located at the midpoint between the elements 22 and 24 is illustrated as the antenna 20, and a region located at the midpoint between the elements 32 and 34 is illustrated as the antenna 30. As shown in FIG. 2, each of the antenna 20 and the antenna 30 has three directivities A, B, and C.

  The directivities A, B, and C are selected according to the communication environment. For example, when the mobile terminal on which the base station and the circuit board 10 are mounted communicates, the directivity in the direction in which the base station exists is selected from the three directivities. The directivity is selected independently for both the antenna 20 and the antenna 30.

  In the present embodiment, the elements 22 and 24 are arranged on both sides of the circuit board 10, and the circuit board 10 is used as a reflector, so that three directivities A, B, and C are obtained from the two elements 22 and 24. It is trying to produce. Usually, since a predetermined wiring pattern made of metal is provided on the circuit board 10, the surface of the circuit board 10 has a property equivalent to that of metal with respect to the frequency of radio waves. Therefore, the radio waves radiated from the elements 22 and 24 are reflected by the surface of the circuit board 10. In the case where the circuit board 10 is formed of a multilayer board, even if the wiring pattern is not provided on the uppermost circuit board at the position corresponding to the element 22 and the element 24, the lower circuit board is not provided. If the wiring pattern is provided, the radio wave can be reflected on the surface of the lower circuit board. A metal pattern (dummy pattern) may be provided on the surface of the circuit board 10 for the purpose of reflecting radio waves.

  The directivity of radio waves may be set to four or more for one antenna, but is assumed if there are three directivities A, B, and C for one of the antenna 20 and the antenna 30. It is possible to ensure a sufficient communication capacity for all communication environments.

  In the present embodiment, the circuit board 10 is used as a reflecting surface for the radio waves radiated from the antenna 20 and the antenna 30, and the directivity is narrowed to generate the three directivities A and B shown in FIG. I have to. The directivity C is generated by combining the directivity A and the directivity B. Hereinafter, a method for generating three directivities A, B, and C from the antenna 20 will be described in detail.

  3, FIG. 4 and FIG. 5 show the radiation directivities A, B and C of the antenna in correspondence with FIG. 3, 4, and 5, the center point O corresponds to the midpoint between the element 22 and the element 24. 3, 4, and 5, the angular positions of 0, 90 °, 180 °, and 270 ° correspond to the angular positions shown in FIG. 2, and the circuit board 10 has 0 ° and 180 °. It arrange | positions so that it may extend in the direction of the straight line to connect. 3, 4, and 5 schematically show the reach of radio waves, and this range is much wider than the distance between the elements 22 and 24, so the elements 22 and 24 are not shown. Not.

  FIG. 3 is a schematic diagram showing directivity when power is supplied only to the element 22 of the antenna 20, and FIG. 4 is a schematic diagram showing directivity when power is supplied only to the element 24. FIG. 5 is a schematic diagram showing directivity when power is supplied to both the element 22 and the element 24 of the antenna 20. 3, 4, and 5, the angle in the circumferential direction corresponds to the angle shown in FIG. 2.

  As shown in FIG. 3, when only the element 22 is fed, the radio wave from the element 22 is reflected by the circuit board 10 and the width of the radio wave radiated becomes narrow. Therefore, the directivity peak is in the direction of 90 °. (The direction perpendicular to the surface of the circuit board 10). Thereby, the beam pattern of directivity A shown in FIG. 2 can be generated.

  Also, as shown in FIG. 4, when only the element 24 is fed, the radio wave from the element 24 is reflected by the circuit board 10 so that the width of the radio wave radiated becomes narrow, and the directivity peak is 270 °. Direction (perpendicular to the surface of the circuit board 10). Thereby, the beam pattern of directivity B shown in FIG. 2 can be generated.

  An isotropic radio wave is radiated from each of the element 22 and the element 24, but the directivity of the radio wave is narrowed when reflected by the circuit board 10. Therefore, according to the present embodiment, the communication capacity can be improved as compared with an antenna that generates an isotropic and omnidirectional beam pattern (omni pattern).

  FIG. 5 is a characteristic diagram showing directivity when power is supplied to both the element 22 and the element 24. As described above, when power is supplied to only one of the element 22 and the element 24, the directivity peak is in the direction of 90 ° or 270 °. On the other hand, since the element 22 is disposed in the vicinity of the side 10 a of the circuit board 10, the reflection of radio waves is weak in the region on the side 10 a side with respect to the element 22. For this reason, the directivity A in the case where power is supplied only to the element 22 is generated in a biased direction from 90 ° to 180 ° (see FIG. 3). Similarly, since the element 24 is disposed in the vicinity of the side 10 a of the circuit board 10, the reflection of radio waves is weak in the region on the side 10 a side with respect to the element 24. For this reason, the directivity B in the case where power is supplied only to the element 24 is generated in a biased direction from 270 ° to 180 ° (see FIG. 4).

  Since radio waves having the same amplitude and the same phase are radiated from the elements 22 and 24, when power is supplied to both the elements 22 and 24, the radio waves of directivity A that are biased from the 90 ° to 180 ° region The directivity B radio waves that are biased from 270 ° to 180 ° are combined, and the directivity peak is in the 180 ° direction (the surface direction of the circuit board 10). Therefore, by supplying power to both the element 22 and the element 24, it is possible to generate the beam pattern of directivity C shown in FIG. When power is supplied to both the element 22 and the element 24, the total power value is the same as the power value when power is supplied to one element.

  Here, if an antenna with very narrow directivity, such as a patch antenna, is used as the element 22 and the element 24, the radio waves radiated from the element 22 and the element 24 cannot be synthesized, and the directivity C is radiated. I can't. In the present embodiment, since a beam pattern having a wide isotropic property is generated from the element 22 and the element 24, the directivity A and the directivity B can be reliably combined, and the directivity C can be radiated. . Further, since the element 22 and the element 24 are arranged at a position where the circuit board 10 can be used as a reflector, the directivity A and directivity B can be narrowed, and as a result, the directivity C is also narrowed. can do. Therefore, it is possible to cope with an environment where the communication capacity in the lateral direction (directivity C) can be improved, and the communication capacity of the entire antenna device can be improved.

  As described above, according to this embodiment, by selectively supplying power to the element 22 and the element 24, radio waves of directivity A, directivity B, and directivity C shown in FIG. 2 can be generated. . As a result, the directivity A, directivity B, and directivity C can be optimally selected according to the communication environment, and stable communication can be performed with sufficient communication capacity.

6 is a schematic diagram showing the positional relationship between the circuit board 10 and the elements 22 and 24, and shows a state in which the circuit board 10, the elements 22 and the elements 24 are viewed from the direction of arrow A in FIG. As shown in FIG. 6, the distance between each of the elements 22 and 24 and the circuit board 10 is D1, and the distance between the side 10a of the circuit board 10 and the elements 22 and 24 is D2. The simulations of FIGS. 3 to 5 show characteristics when the wavelength of the radio wave is λ and the distance D1 and the distance D2 are both 0.087λ. If the frequency f of the radio wave is 5 × 10 ⁹ [Hz] and the speed of light c is 3 × 10 ⁸ [m / s], then λ = c / f = (3 × 10 ^8/5 × 10 ⁹ ), 087λ is a value of about 5 mm.

  The directivity shown in FIGS. 3 to 5 can be changed by changing the distances D1 and D2 in FIG. In particular, the directivity A and the directivity B can be varied by changing the distance D2. 3 and 4, the radio waves of directivity A and directivity B are more biased in the direction of 180 ° as the distance D2 is decreased. For this reason, as the distance D2 is decreased, the directivity C radio wave obtained by combining the directivity A and the directivity B becomes narrower about the 180 ° direction. When the distance D2 is greater than 0.15λ, the directivity A and the directivity B are less biased in the 180 ° direction, and the directivity C is not directed in the 180 ° direction. . Accordingly, the distance D2 is preferably set to 0.15λ or less.

  With respect to the distance D1, by setting D1 = 0.087λ, the element 22 and the element 24 are sufficiently close to the circuit board 10, so that the directivity can be narrowed by the reflection of radio waves by the circuit board 10. Even if the element 22 and the element 24 are further brought closer to the circuit board 10, the directivity of the radio wave hardly changes. On the other hand, when the value of D1 is increased to 0.5λ or more, since the reflection by the circuit board 10 is weakened, the directivity of radio waves changes. Therefore, as long as the value of D1 is not increased to 0.5λ or more, even if the value of D1 is slightly changed, the influence on directivity A and directivity B is small, and as a result, the influence on directivity C is also small.

  FIG. 7 is a characteristic diagram showing a result of improving the communication capacity by the antenna device of the present embodiment. In FIG. 7, the vertical axis represents the communication capacity [bps / Hz], and the horizontal axis represents the four environments P1, P2, P3, and P4 in which communication is performed. In FIG. 7, the characteristic of the solid line indicates the communication capacity of the antenna device of this embodiment. Also, the broken line characteristic indicates the communication capacity of the monopole antenna having an isotropic beam pattern. As shown in FIG. 7, according to the antenna device of the present embodiment, the directivity of the isotropic beam pattern can be narrowed by the reflection of the circuit board 10, and therefore in each environment P1, P2, P3, P4. Obviously, the communication capacity can be improved.

  FIG. 8 is a schematic diagram illustrating another example of the antenna device. FIG. 8 shows an example in which the antenna device is composed of a T-shaped monopole antenna. As shown in FIG. 8, the T-shaped monopole antenna 40 includes an antenna element 42 and an antenna element 44. The T-shaped monopole antenna 50 includes an antenna element 52 and an antenna element 54. Since the configurations of the antenna 40 and the antenna 50 are substantially the same, in the following description, the configuration of the antenna 40 will be mainly described.

  Power is supplied to the element 42 from the circuit board 10 via the power supply part 42a. When power is supplied from the circuit board 10 to the power supply unit 42a, vertical polarization is generated mainly in a portion extending in the vertical direction of the element 42, and radio waves are radiated. Similarly, power is supplied to the element 44 from the circuit board 10 via the power supply unit 44a. The power feeding units 42 a and 44 a are connected to the circuit board 10 via the power feeding line 45. When power is supplied from the circuit board 10 to the power supply unit 44a, vertical polarization is generated mainly in a portion extending in the vertical direction of the element 44, and radio waves are radiated.

  And the radio wave radiated | emitted from the element 42 and the element 44 is reflected by the circuit board 10 similarly to the antenna apparatus of FIG. Accordingly, a beam pattern with directivity A can be generated by supplying power only to the element 42, and a beam pattern with directivity B can be generated by supplying power only to the element 44. Further, by supplying power to both the element 42 and the element 44, a beam pattern of directivity C can be generated.

  FIG. 9 is a schematic diagram illustrating still another example of the antenna device. In FIG. 9, the antenna 70 includes an antenna element 72 and an antenna element 74. The antenna 80 includes an antenna element 82 and an antenna element 84. Since the configurations of the antenna 70 and the antenna 80 are substantially the same, in the following description, the configuration of the antenna 70 will be mainly described. In the example of FIG. 9, an element 72, an element 74, an element 82, and an element 84 made of metal are formed on the surface of a cubic dielectric 60. The elements 72, 74, 82, and 84 can be formed on the surface of the dielectric 60 by a method such as printing.

  Each of the elements 72, 74, 82, and 84 is supplied with power from the circuit board 10 via the power supply unit at the lower end. In FIG. 8, the power feeding portion 74a of the element 74 and the power feeding portion 84a of the element 84 located on the front side are illustrated. The dielectric 60 is provided on the plate material 62 and is mounted on the circuit board 10. An electrode plate 64 is provided on the upper surface of the dielectric 60. Each of the plate material 62 and the electrode plate 64 is grounded.

  In the example of FIG. 9, the elements 72, 74, 82, 84 of the antennas 70, 80 can be configured integrally with the dielectric 60, so that the antennas 70, 80 are mounted by mounting the dielectric 60 on the circuit board 10. Can be placed on the circuit board 10. Therefore, the antenna device can be mounted on the circuit board 10 without complicated work. Further, since the antenna is integrally formed with the dielectric 60, it is possible to increase the strength against disturbance even when the elements 72, 74, 82, 84 are thin.

  1 may be configured such that the antennas 20 and 30 are provided on the surface of the dielectric and the dielectric is mounted on the circuit board 10 as in the example of FIG.

  As described above, according to the present embodiment, since the isotropic pattern radiated from the antenna elements 22 and 24 can be reflected by the circuit board 10, the radiated radio wave has directivity. Communication capacity can be increased. In addition, by simultaneously feeding power to the elements 22 and 24 arranged on the front and back of one end of the circuit board 10, radio waves radiated from the two elements can be synthesized, and the direction in which the circuit board 10 extends ( It is possible to radiate radio waves in the direction C). Therefore, communication by the APS method can be performed with a simple configuration.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

It is a perspective view which shows the antenna apparatus concerning one Embodiment of this invention. It is a schematic diagram which shows the directivity required by an APS system. It is a schematic diagram which shows the result of having simulated the electric field strength of the directivity A shown in FIG. It is a schematic diagram which shows the result of having simulated the electric field strength of the directivity B shown in FIG. It is a schematic diagram which shows the result of having simulated the electric field strength of the directivity C shown in FIG. It is a schematic diagram which shows the positional relationship of a circuit board and two elements. It is a characteristic view which shows the result of having improved communication capacity with the antenna apparatus of one Embodiment of this invention. It is a schematic diagram which shows the other example of an antenna device. It is a schematic diagram which shows the example which comprised the antenna of FIG. 8 more concretely.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Circuit board 20, 30, 40, 50 Antenna 22, 24, 32, 34, 42, 44, 52, 54 Element 22a, 24a, 32a, 34a Feed part 60 Dielectric material

Claims (2)

First and second antennas that are separated from the end surface of the circuit board by the same distance along one surface and the other surface of the circuit board, and are provided with feed terminals at positions having a plane symmetry relationship through the circuit board, respectively. Elements,
Power supply control means for selectively supplying power to one or both of the first and second antenna elements,
In the region from the end face of the circuit board to the arrangement position of each of the power supply terminals, a conductor region that becomes a radio wave reflector is formed or incorporated,
When the power supply control unit supplies power to both the first and second antenna elements, the radio waves radiated from the first and second antenna elements are combined and directed toward the end face direction of the circuit board. An antenna device characterized by having a characteristic.   The distance from the end face of the circuit board to the position where each of the feeding terminals is arranged is 0.15λ or less, where λ is the wavelength of the radio wave radiated from the first and second antenna elements. The antenna device according to claim 1.

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