JP2013168780A - Surface-mounted antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easy-to-manufacture surface-mounted antenna with a high gain.SOLUTION: A surface-mounted antenna 1 comprises: a laminate 2 formed by laminating plural base material layers; a coil conductor provided to the laminate 2 with one direction orthogonal to a lamination direction of the laminate 2 as a winding axial direction; and terminal electrodes 51 and 52 provided on a surface of the laminate 2 and connected to the coil conductor. To the coil conductor, plural conductor patterns 31C, 32C, 33C and 34C provided on an upper surface of the laminate 2, plural conductor patterns 31D, 32D and 33D provided on a bottom surface of the laminate 2, side face conductors 31A, 32A, 33A and 34A provided on one of two side faces parallel in the lamination direction of the laminate 2, and side face conductors 31B, 32B, 33B and 34B provided on the other of the two side faces are spirally connected.

Description

  The present invention relates to a surface mount antenna used in, for example, an NFC (Near Field Communication) system.

  As a coil antenna that is mounted on a circuit board of a portable terminal and has a radiation direction perpendicular to the mounting surface, a dielectric layer with a coil pattern is laminated on the surface of each layer, and each coil pattern is connected with an interlayer connection conductor. A configuration for connection is known. When this configuration is used for a small coil antenna used in a frequency band of about 13.56 MHz, as in the NFC system, the coil diameter is increased because the coil pattern is formed inside the dielectric layer. Because it is not possible, it is difficult to obtain a large inductance value. On the other hand, in order to obtain a large inductance value, the base material can be composed of a magnetic layer instead of a dielectric layer, but a part of the magnetic flux passing through the center of the coil is confined in the magnetic portion outside the coil, and the antenna characteristics Deteriorates.

  Patent Document 1 discloses an omnidirectional chip antenna that can obtain a high gain. In the antenna described in Patent Document 1, a coil conductor pattern is formed inside a substrate made of a dielectric material or a magnetic material so that a cross-sectional shape orthogonal to the winding axis is a rectangle. As a result, the line length of the coil conductor can be made longer than when the cross-sectional shape is circular or elliptical, and the current distribution region can be increased. This increases the radiation efficiency and further improves the antenna gain.

JP 9-36639 A

  In the chip antenna described in Patent Document 1, it is difficult to increase the coil diameter because the coil conductor pattern is formed inside the substrate. In particular, when the base is made of a magnetic material, a part of the magnetic flux passing through the center of the coil is confined in the magnetic body portion outside the coil, and the antenna characteristics deteriorate.

  Therefore, an object of the present invention is to provide a surface mount antenna having a high gain.

  The surface mount antenna according to the present invention includes a laminate having a plurality of base material layers, a first main surface, and a second main surface that is a main surface opposite to the first main surface. A coil conductor provided in the laminate with one direction orthogonal to the lamination direction of the laminate as a winding axis direction, and provided on a plane parallel to the lamination direction of the laminate, and the coil conductor is connected to the coil conductor. The coil conductor includes a plurality of first conductors provided along the surface of the base material layer and a plurality of second conductors provided along the surface of the base material layer. And a plurality of third conductors provided on one of the two side surfaces parallel to the stacking direction of the multilayer body, and a plurality of fourth conductors provided on the other of the two side surfaces, One conductor, the second conductor, the third conductor, and the fourth conductor are spirally connected. To.

  In this configuration, the coil diameter can be increased with respect to the size of the multilayer body by forming the coil conductor including the third conductor and the fourth conductor formed on the two side surfaces of the multilayer body. Further, since the third and fourth conductors are exposed on the side surfaces of the multilayer body, even if the multilayer body includes a magnetic body, a part of the magnetic flux passing through the coil center is not confined, and therefore the antenna characteristics are There is no deterioration. As a result, the antenna characteristics (gain) of the surface mount antenna can be improved.

  It is preferable that each of the third conductor and the fourth conductor is configured by connecting an interlayer connection conductor formed in each layer of the multilayer body.

  In this configuration, an interlayer connection conductor such as a via conductor or a through-hole conductor is formed in each layer, and they are connected to each other to form a third conductor and a fourth conductor. Can be formed.

  The laminate may have a magnetic layer.

  In this configuration, when the magnetic material is used, a large inductance value can be obtained, and the radiation efficiency of the antenna can be improved.

  The laminate has a nonmagnetic layer provided so as to sandwich the plurality of magnetic layers, and the coil conductor is formed between the nonmagnetic layer and the magnetic layer. Is preferred.

  In this configuration, since the base material layer located on the outer layer than the coil conductor is a non-magnetic material, it is possible to prevent a decrease in antenna characteristics due to the magnetic flux being confined in the laminate by the magnetic material. In general, a non-magnetic material has a smaller tan δ (dielectric loss tangent) than a magnetic material, so that the Q value of the coil conductor can be improved.

  The first conductor is preferably provided on a first main surface of the multilayer body, and the second conductor is preferably provided on a second main surface of the multilayer body.

  In this configuration, the coil diameter can be further increased with respect to the size of the multilayer body by providing both the first conductor and the second conductor on the first main surface and the second main surface of the multilayer body. Further, in addition to the third conductor and the fourth conductor, the first conductor and the second conductor are also exposed on the outer surface of the multilayer body. Therefore, even when the multilayer body includes a magnetic body, the magnetic flux passing through the center of the coil is reduced. The part is not confined, and therefore the antenna characteristics are not deteriorated. As a result, the antenna characteristics (gain) of the surface mount antenna can be improved.

  A plurality of the terminal conductors may be provided on the same surface of the multilayer body, and the coil conductor may be connected to one of the terminal conductors.

  In this configuration, the surface on which the terminal conductor is formed can be used as the mounting surface of the surface mount antenna.

  The coil conductor may be connected to the terminal conductor through a region surrounded by the first conductor, the second conductor, the third conductor, and the fourth conductor.

  In this structure, since it is connected to the terminal conductor through the region (coil opening) surrounded by the first conductor, the second conductor, the third conductor, and the fourth conductor, the line connecting the coil conductor and the terminal conductor. Can be shortened, the DC resistance can be suppressed, and the Q value can be prevented from lowering. Further, since the routing line is passed through the coil opening portion, it does not cause a harmful effect of securing the size of the coil diameter, so that deterioration of the antenna characteristics can be suppressed.

  The terminal conductor is preferably provided on a surface adjacent to the two side surfaces of the multilayer body and parallel to the lamination direction.

  In this configuration, it is necessary to form conductors on two side surfaces along the stacking direction of the multilayer body. However, if an interlayer connection conductor is formed, the interlayer connection conductor can be used as a terminal conductor. Therefore, no special manufacturing process is required.

  The structure provided with the dummy terminal conductor formed in the surface of the said laminated body in which the said terminal conductor was formed may be sufficient.

  In this configuration, by disposing the dummy terminal conductor, it is possible to connect to the mounting substrate via the dummy terminal conductor added to the terminal conductor. Thereby, the mounting property with respect to a mounting board increases, and connection reliability can be improved.

  According to the present invention, the antenna characteristics can be improved by increasing the diameter of the coil conductor. Moreover, a special manufacturing process for forming the third conductor and the fourth conductor on the two side surfaces by forming the interlayer connection conductors and connecting them to form a conductor along the stacking direction of the multilayer body. A surface mount antenna can be easily manufactured without the need.

FIG. 3 is a perspective view of the surface mount antenna according to the first embodiment before being mounted on a printed board. The perspective view of the surface mount type antenna after mounting to a printed circuit board. FIG. 3 is an exploded perspective view of the surface mount antenna according to the first embodiment. The schematic diagram of the coil conductor formed in the laminated body. The perspective view of the surface mount type antenna which concerns on Embodiment 2 before mounting in a printed circuit board. FIG. 4 is an exploded perspective view of a surface mount antenna according to a second embodiment. FIG. 6 is an exploded perspective view of a surface mount antenna according to a third embodiment. The figure which shows typically the stray capacitance comprised between the windings of a coil conductor. The figure which shows typically the stray capacitance comprised between the coil | winding of the coil conductor made into a comparison. (A) is front sectional drawing of the communication terminal device provided with the surface mount type antenna, (B) is a top perspective view of the communication terminal device. The figure explaining the case where a ground pattern is used as a booster antenna.

(Embodiment 1)
The surface mount antenna according to the first embodiment described below is, for example, an antenna for a reader / writer that is used in an NFC system using a high frequency signal in the HF band as a carrier frequency. The surface mount antenna according to the first embodiment is mounted on a printed board.

  FIG. 1 is a perspective view of a surface-mounted antenna according to Embodiment 1 before being mounted on a printed circuit board. FIG. 2 is a perspective view of the surface-mounted antenna after mounting on a printed circuit board. FIG. 3 is an exploded perspective view of the surface mount antenna 1 according to the first embodiment.

  The surface mount antenna 1 includes a laminate 2 in which a plurality of magnetic layers are laminated. For example, the multilayer body 2 is formed by stacking a plurality of magnetic green sheets formed with via conductors or conductor patterns, which will be described later, to create a mother substrate, and then to a predetermined work size (a size to be the surface mount antenna 1). It is produced by cutting and then firing. In the present embodiment, the stacked body 2 includes the first layer 21, the second layer 22, the third layer 23, the fourth layer 24, the fifth layer 25, the sixth layer 26, and the seventh layer 27 along the stacking direction. In addition, a total of nine magnetic layers of the eighth layer 28 and the ninth layer 29 are provided. Below, let the 1st layer 21 side be the upper side in the lamination direction. In addition, you may obtain the laminated body 2 by baking in the state of a mother substrate, and cutting after that.

  The layers 21 to 29 of the multilayer body 2 may not be all magnetic bodies having the same magnetic permeability, and the magnetic permeability may be different for each layer. Moreover, a part of each layer 21-29 of the laminated body 2 may be a dielectric material layer.

  In addition, in the manufacturing process, when the magnetic green sheets to be the layers 21 to 29 are overlaid, the surfaces of the magnetic green sheets of the layers 21 to 28 are overlapped in the same direction. As shown in FIG. 3, the magnetic green sheet of the ninth layer 29 is turned upside down and overlapped with the magnetic green sheet of the laminate 28. Therefore, the stacked body 2 becomes the surface of the first layer 21, and the bottom surface of the stacked body 2 becomes the surface of the ninth layer 29.

  Side conductors (third conductors) 31A, 32A, 33A, and 34A are formed on one of the two side surfaces of the opposite stacked body 2 along the stacking direction, and the other side conductors (fourth conductor) along the stacking direction. ) 31B, 32B, 33B, 34B are formed. The side conductors 31A, 32A, 33A, 34A and the side conductors 31B, 32B, 33B, 34B are exposed on the side surfaces of the multilayer body 2, respectively. Further, the side conductors 31A, 32A, 33A, 34A and the side conductors 31B, 32B, 33B, 34B are via conductors that are interlayer connection conductors formed in the respective layers 21 to 29 of the multilayer body 2, as shown in FIG. Are connected.

  The via conductors of the respective layers 21 to 29 are formed by filling a through hole formed by passing a laser through the magnetic green sheet with a conductive paste. When the magnetic green sheet is cut into a work size, the exposed via conductors are formed in the layers 21 to 29 by cutting the formed via conductor portions. Via conductors of these layers 21 to 29 are connected to form side conductors 31A, 32A, 33A, 34A and side conductors 31B, 32B, 33B, 34B.

  Conductive patterns 31C, 32C, 33C, and 34C (first conductors) are formed on the upper surface (first main surface, surface of the first layer 21) of the multilayer body 2. The conductor patterns 31C, 32C, 33C, and 34C are formed by printing a conductor pattern on the surface of the green sheet to be the first layer 21 and simultaneously firing the green sheet. The conductor pattern is made of, for example, Ag. The conductor pattern 31C is connected to the side conductors 31A and 31B. The conductor pattern 32C is connected to the side conductors 32A and 32B. The conductor pattern 33C is connected to the side conductors 33A and 33B. The conductor pattern 34C is connected to the side conductors 34A and 34B.

  Furthermore, as shown in FIG. 3, a plurality of conductor patterns 31D, 32D, and 33D (second conductors) are formed on the bottom surface (second main surface, the surface of the ninth layer 29) of the multilayer body 2. Yes. The conductor pattern 31D is connected to the side conductors 32A and 32B, the conductor pattern 32D is connected to the side conductors 33A and 33B, and the conductor pattern 33D is connected to the side conductors 34A and 34B. Thereby, the coil conductor having the winding axis direction in one direction orthogonal to the stacking direction is wound around the stacked body 2.

  Thus, by forming the coil conductor so as to be exposed on the outer surface of the multilayer body 2, the coil diameter can be further increased. As a result, the inductance value is increased, and the antenna characteristics of the surface mount antenna 1 are improved. Can be improved. Further, since the coil conductor is wound around the outer periphery of the magnetic body, the magnetic field is not confined by the magnetic body, and the radiation efficiency is increased. Further, the side conductors 31A, 32A, 33A, 34A and the side conductors 31B, 32B, 33B, 34B formed on the surface of the multilayer body 2 form via conductors in the respective layers 21 to 29, and are cut at the via conductor portions. Therefore, no special manufacturing process is required.

  In addition, terminal electrodes (terminal conductors) 51 and 52 are formed along the stacking direction on the top surface, bottom surface, and surfaces adjacent to the two side surfaces (hereinafter referred to as mounting surfaces) of the multilayer body 2. Similar to the side conductors 31A, 32A, 33A, 34A and the side conductors 31B, 32B, 33B, 34B, the terminal electrodes 51, 52 are formed by connecting via conductors formed in the respective layers 21-29. The terminal electrodes 51 and 52 are connected to electrodes 101 and 102 provided on the printed circuit board 100 on which the surface mount antenna 1 is mounted. Therefore, as shown in FIG. 2, the surface-mounted antenna 1 is mounted on the printed circuit board 100 in a state in which the stacking direction is parallel to the mounting surface (the plane of the printed circuit board 100).

  Both ends of a coil conductor wound around the laminate 2 are connected to the terminal electrodes 51 and 52. Specifically, a conductor pattern 35 that connects the side conductor 34 </ b> B and the terminal electrode 52 is formed on the second layer 22. The ninth layer 29 is provided with a conductor pattern 36 that connects the side conductor 31 </ b> A and the electrode 51.

  FIG. 4 is a schematic diagram of the coil conductor formed in the multilayer body 2. As shown in FIG. 4, the surface-mounted antenna 1 has a coil conductor in which terminal electrodes 51 and 52 formed on the mounting surface are input / output terminals and the normal direction of the mounting surface is the winding axis direction. Become. A signal line (conductor pattern 35) connected from one end of the coil conductor to the terminal electrode 52 passes through the inside of the coil conductor (coil opening). For this reason, it does not become an obstacle which enlarges a coil diameter by the signal line (conductor pattern 35) which connects the end and terminal electrode of a coil conductor. Further, the routing of the signal line (conductor pattern 35) can be shortened, the direct current resistance can be suppressed, and the Q value can be prevented from lowering.

(Embodiment 2)
FIG. 5 is a perspective view of the surface mount antenna according to the second embodiment before being mounted on a printed circuit board. FIG. 6 is an exploded perspective view of the surface mount antenna according to the second embodiment. In the present embodiment, the first layer 21 and the ninth layer 29 that are the outer layers of the stacked body 2 are nonmagnetic layers made of, for example, a dielectric material, and are layers between the first layer 21 and the ninth layer 29. 22 to 28 are magnetic layers. A part of the layers 22 to 28 between the first layer 21 and the ninth layer 29 may be a dielectric layer.

  The multilayer body 2 provided in the surface mount antenna 1 according to the present embodiment has a configuration in which the first layer 21 and the ninth layer 29 of the outer layer are non-magnetic layers, and the layers 22 to 28 are magnetic layers. . And each layer 21-29 of the laminated body 2 is laminated | stacked by making the surface the same direction. Therefore, unlike Embodiment 1, the bottom surface of the multilayer body 2 is the back surface of the ninth layer 29.

  Similarly to the first embodiment, side conductors 31A, 32A, 33A, and 34A and side conductors 31B, 32B, 33B, and 34B are exposed on the side surfaces of the laminate 2 on the two opposing side surfaces of the multilayer body 2. Yes. Conductive patterns 31C, 32C, 33C, and 34C are formed on the surface of the second layer 22 in contact with the outer layer (first layer 21). Thus, a plurality of conductor patterns 31C, 32C, 33C, and 34C are formed between the first layer 21 that is a nonmagnetic layer and the second layer 22 that is a magnetic layer. The conductor pattern 32C connects the side conductors 32A and 32B. The conductor pattern 33C connects the side conductors 33A and 33B. The conductor pattern 34C connects the side conductors 34A and 34B. On the surface of the ninth layer 29, a plurality of conductor patterns 31D, 32D, and 33D are formed. Thus, a plurality of conductor patterns 31D, 32D, 33D, and 34D are formed between the eighth layer 28 that is a magnetic layer and the ninth layer 29 that is a nonmagnetic layer. The conductor pattern 31D connects the side conductors 32A and 31B, the conductor pattern 32D connects the side conductors 33A and 32B, and the conductor pattern 33D connects the side conductors 34A and 33B.

  Furthermore, a conductor pattern 35 that connects the side conductor 34 </ b> B and the terminal electrode 52 is formed on the surface of the first layer 21. On the surface of the ninth layer 29, a conductor pattern 36 that connects the side conductor 31A and the terminal electrode 51 is formed.

  Similar to the first embodiment, the surface-mounted antenna 1 in this configuration has a configuration in which a coil conductor having a winding axis direction perpendicular to the stacking direction is wound around the stack 2, and the coil diameter is further increased. Therefore, the antenna characteristics of the surface mount antenna 1 can be improved. Moreover, since each layer 22-28 of the laminated body 2 in which the coil conductor is formed is a magnetic layer, and the first layer 21 and the ninth layer 29 outside the coil conductor are nonmagnetic layers, the magnetic flux from the coil conductor Is prevented from being confined in the chip of the surface mount antenna 1 by the magnetic material. Thereby, the antenna characteristic (gain) of the surface mount antenna 1 is improved.

(Embodiment 3)
FIG. 7 is an exploded perspective view of the surface mount antenna according to the third embodiment. The surface mount antenna 1 according to the third embodiment is an antenna using dielectric ceramics, and all the layers 21 to 29 of the multilayer body 2 are dielectric layers. Unlike the first embodiment, the second layer 22 is not formed with the conductor pattern 35 that connects the conductor 34 </ b> B and the terminal electrode 52. Accordingly, the surface mount antenna 1 constitutes a so-called helical antenna in which one end of the coil conductor is connected to the terminal electrode 51 and the other end is an open end. In the case of the third embodiment, the terminal electrode 52 is a dummy terminal electrode for mounting on the printed circuit board 100 (see FIG. 1).

  With this configuration, as in the first and second embodiments, the coil diameter can be increased and the antenna characteristics can be improved.

  Furthermore, in this embodiment, each layer of the laminate 2 is a dielectric layer. The coil conductor is exposed on the surface of the laminate 2. As a result, the stray capacitance formed between the windings of the coil conductor is smaller than when the coil conductor is formed inside the multilayer body 2. FIG. 8 is a diagram schematically showing the stray capacitance formed between the windings of the coil conductor. FIG. 9 is a diagram schematically showing a stray capacitance formed between windings of a coil conductor to be compared. FIG. 8 shows the surface-mounted antenna 1 according to the third embodiment, in which a coil conductor is formed by being exposed on the surface of the multilayer body 2. FIG. 9 is a view when a coil conductor is formed inside the multilayer body 2.

  In this embodiment, the stray capacitance C1 formed between the coil conductor and the printed circuit board 100 (ground) and the stray capacitance C2 formed between the windings of the coil conductor are formed outside the multilayer body 2. The On the other hand, when the coil conductor is formed inside the laminate 2, the stray capacitance C3 formed between the coil conductor and the printed board 100 and the stray capacitance C4 formed between the windings of the coil conductor are: It is formed inside the laminate 2. For this reason, the stray capacitance C1 is smaller than the stray capacitance C3, and the stray capacitance C2 is smaller than the stray capacitance C4. For this reason, in this embodiment, the electric field coupling with the ground can be reduced, and the radiation efficiency of the surface mount antenna 1 can be further improved by making it difficult for the electric field to be confined in the multilayer body 2.

  In the present embodiment, each layer of the laminate is a dielectric layer, and the stray capacitance formed between the windings of the stray capacitance coil conductor is reduced. Therefore, the surface mount antenna 1 according to the present embodiment is used as the UHF. It can also be used as a band antenna. (Even if each layer of the laminated body 2 is a magnetic body, when used in a high frequency band where the relative permeability of the magnetic body is about 1, the magnetic body acts as a dielectric).

  Note that the specific configuration of the surface-mounted antenna 1 can be appropriately changed in design, and the actions and effects described in the above-described embodiments are merely a list of the most preferable actions and effects resulting from the present invention. The operations and effects of the present invention are not limited to those described in the above embodiment.

  For example, in each embodiment, the interlayer connection conductor constituting the side conductor is formed of a via conductor, but is a through-hole conductor in which a conductor is provided on the inner wall surface of the through hole, or a conductor formed by plating. Also good. In the second embodiment, the plurality of magnetic layers are sandwiched between the non-magnetic layers. However, only one of the surfaces may be covered with the non-magnetic layer. Moreover, in Embodiment 3, the structure which made each layer of the laminated body 2 the magnetic body layer may be sufficient. In this case, the surface-mounted antenna 1 according to the third embodiment can be used as an FM broadcast receiving antenna as a helical antenna because one end of the coil conductor is an open end.

  Further, the surface mount antenna 1 described above may be used in combination with a so-called booster antenna that enhances the electromagnetic field generated by the surface mount antenna 1. Hereinafter, the combination of the surface mount antenna 1 and the booster antenna will be described.

  FIG. 10A is a front cross-sectional view of a communication terminal device including the surface-mounted antenna 1, and FIG. 10B is a top perspective view of the communication terminal device. In FIG. 10B, only the surface mount antenna 1 and the booster antenna 110 are shown, and other elements are omitted.

  The surface mount antenna 1 is provided in the terminal housing 60 </ b> A of the communication terminal device 60. A booster antenna 110 is attached to the inner surface of the terminal housing 60A with a double-sided tape or the like. The booster antenna 110 includes an insulating or dielectric base material 111 made of, for example, a polyimide film, and coil conductors 112 and 113 formed on the front and back surfaces of the base material 111. Further, a magnetic sheet made of ferrite or the like may be disposed on the coil conductor 113 side of the base material 111. The coil conductors 112 and 113 are loop conductors wound in opposite directions in a plan view (in the same direction in a perspective view). An LC resonance circuit is constituted by an inductance component formed by the coil conductors 112 and 113 and a capacitance component generated between the coil conductors 112 and 113, and LC resonance occurs.

  Further, the printed wiring board 40 having the ground pattern 41, the battery pack 120, and the like are housed in the terminal housing 60A. A communication circuit is formed on the printed wiring board 40, and an RFIC IC chip (feeding circuit) 51 and the surface-mounted antenna 1 are surface-mounted on the upper surface of the printed wiring board 40 in the figure. The surface-mounted antenna 1 is connected to the RFIC IC chip 42 by wiring (not shown). The IC chip for RFIC 42 includes a memory circuit, a logic circuit, a clock circuit, and the like, is configured as an integrated circuit chip that processes an RF signal, functions as a power feeding circuit, and supplies a high-frequency signal to the surface-mounted antenna 1. In addition, it receives power from the surface-mounted antenna 1 and receives signals.

  As shown in FIG. 10B, the booster antenna 110 mainly functions as a radiating element that transmits and receives radio signals to and from the communication partner antenna. Since the communication distance with the communication partner antenna greatly depends on the antenna outer dimensions, it is preferable that the booster antenna 110 has a larger outer dimension than the surface-mounted antenna 1 when viewed in plan.

  The surface mount antenna 1 is disposed so as to straddle the coil conductors 112 and 113 of the booster antenna 110 in plan view. The surface mount antenna 1 has a coil axis arranged in the same direction as the coil axis of the booster antenna 110 and is coupled to the coil conductors 112 and 113 of the booster antenna 110 via an electromagnetic field.

  Specifically, when a current flows through the coil conductor of the surface mount antenna 1, the coil conductors 112 and 113 of the booster antenna 110 overlapping the surface mount antenna 1 are magnetically coupled. As a result, lines of magnetic force (magnetic field) that greatly spread from the surface mount antenna 1 and the booster antenna 110 are generated.

  The ground pattern 41 provided in the printed wiring board 40 may be a booster antenna. In this case, the booster antenna 110 shown in FIG. 10 is not necessary.

  FIG. 11 is a diagram illustrating a case where the ground pattern 41 is a booster antenna. FIG. 11A is a perspective view showing the directions of the current flowing through the coil conductor of the surface-mounted antenna 1 and the current flowing through the ground pattern 41. FIGS. 11B and 11C are diagrams schematically showing the current flowing through the coil conductor of the surface-mounted antenna 1, the current flowing through the ground pattern 41, and the state of the magnetic flux generated by them. .

  When a current flows through the coil conductor of the surface mount antenna 1 in the direction of the current a, a current is induced in the direction of the current b in the ground pattern 41. That is, the induced current b circulates around the outer periphery of the planar conductor due to the current flowing through the coil conductor. As a result, as shown in FIG. 11B, a magnetic flux indicated by an arrow A is generated in the surface mount antenna 1, and a magnetic flux indicated by an arrow B is generated in the ground pattern 41. A magnetic flux A ′ shown in FIG. 11B represents a magnetic flux passing through a position avoiding the ground pattern 41.

  FIG. 11C is a diagram more equivalently showing the magnetic flux of FIG. A magnetic flux indicated by an arrow C is a magnetic flux generated by combining the magnetic flux B generated around the ground pattern 41 and the magnetic flux A ′ generated in the surface mount antenna 1. The surface-mounted antenna 1 is more likely to generate the magnetic flux indicated by the arrow A ′ when it does not overlap the ground pattern 41 in plan view, but may partially or entirely overlap depending on the design.

  When magnetic flux enters from the coil antenna on the communication partner side, the reverse phenomenon occurs. That is, when the magnetic flux of the coil antenna on the communication partner side passes around the ground pattern 41 and is linked to the surface mount antenna 1, a current b flows through the ground pattern 41, and a current a flows through the coil conductor of the surface mount antenna 1. Flowing.

  As described above, when the surface mount antenna 1 and the booster antenna are combined, and an HF band RFID system using the 13.56 MHz band as a communication frequency, for example, an electronic device (mobile phone) equipped with an RFID tag The telephone terminal) and the reader / writer antenna device can be coupled mainly via an induced magnetic field to transmit and receive predetermined information.

1-surface mount antenna 2-laminated body 21-first layer (base material layer, first outer layer)
22-second layer (base material layer)
23-third layer (base material layer)
24-4th layer (base material layer)
25-Fifth layer (base material layer)
26-sixth layer (base material layer)
27-seventh layer (base material layer)
28-Eighth layer (base material layer)
29-the ninth layer (base material layer, second outer layer)
31A, 32A, 33A, 34A-side conductor (third conductor)
31B, 32B, 33B, 34B-Side conductor (fourth conductor)
31C, 32C, 33C, 34C-Conductor pattern (first conductor)
31D, 32D, 33D-Conductor pattern (second conductor)
35-conductor pattern 36-conductor pattern 51, 52-terminal electrode (terminal conductor)
100-printed circuit board 101, 102-electrodes C1, C2, C3, C4-stray capacitance

Claims (9)

A laminate having a plurality of base material layers and having a first main surface and a second main surface that is a main surface opposite to the first main surface;
A coil conductor provided in the laminate with one direction orthogonal to the lamination direction of the laminate as the winding axis direction;
A terminal conductor provided on a plane parallel to the laminating direction of the laminated body and connected to the coil conductor;
With
The coil conductor is
A plurality of first conductors provided along the surface of the base material layer;
A plurality of second conductors provided along the surface of the base material layer;
A plurality of third conductors provided on one of two side surfaces parallel to the stacking direction of the laminate, and a plurality of fourth conductors provided on the other of the two side surfaces;
And the first conductor, the second conductor, the third conductor and the fourth conductor are spirally connected,
Surface mount antenna.   The surface-mount antenna according to claim 1, wherein the third conductor and the fourth conductor are each connected to an interlayer connection conductor formed in each layer of the multilayer body.   The surface mount antenna according to claim 1, wherein the laminated body includes a magnetic layer. The laminate has a nonmagnetic layer provided so as to sandwich the plurality of magnetic layers,
The coil conductor is formed between the non-magnetic layer and the magnetic layer.
The surface mount antenna according to claim 3. The first conductor is provided on a first main surface of the laminate,
The second conductor is provided on a second main surface of the laminate.
The surface mount antenna according to any one of claims 1 to 3. A plurality of the terminal conductors are provided on the same surface of the laminate,
The coil conductor is connected to one of the terminal conductors,
The surface mount antenna according to any one of claims 1 to 5. The coil conductor is connected to the terminal conductor through a region surrounded by the first conductor, the second conductor, the third conductor, and the fourth conductor.
The surface mount antenna according to claim 6. The terminal conductor is
Adjacent to the two side surfaces of the laminate, provided on a plane parallel to the lamination direction,
The surface mount antenna according to any one of claims 1 to 7.   The surface mount antenna according to any one of claims 1 to 8, wherein a dummy terminal conductor is formed on a surface of the laminate on which the terminal conductor is formed.

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