JP5720807B2 - Antenna device and communication terminal device - Google Patents

Description

  The present invention relates to an antenna device and a communication terminal device used in a communication system of HF band or UHF band.

  An RFID (Radio Frequency Identification) system is widely used as a system for charging and article management. In an RFID system, a reader / writer and an RFID tag are wirelessly communicated in a non-contact manner, and a high-frequency signal is transmitted and received between these devices. Each of the reader / writer and the RFID tag includes a wireless IC chip for processing a high-frequency signal and an antenna element for transmitting and receiving the high-frequency signal. As an antenna element, for example, in the case of an HF band RFID system using the 13.56 MHz band, a coiled antenna is used, and the antenna coil on the reader / writer side and the antenna coil on the tag side are coupled via an induction magnetic field. The

  In this HF band RFID system, an antenna coil is built in a portable communication terminal such as a FeliCa (registered trademark) compatible terminal disclosed in Patent Document 1, and the communication terminal itself is used as a reader / writer or an RFID tag. There is. FIG. 6 is a longitudinal sectional view of the reader / writer 1 for a non-contact IC card described in Patent Document 1. In FIG.

  The non-contact IC card reader / writer 1 includes an antenna substrate having a loop antenna and a capacitor provided on the upper surface, a control substrate 6 having a transmission / reception circuit and a chip-type coil 5 provided on the upper surface, an antenna substrate 4 and a control substrate 6. And a magnetic material sheet 10 and an insulating case 15. The magnetic sheet 10 is disposed away from the top of the chip coil 5 in order to form the opening 11 above the chip coil 5 provided on the control board 6. The chip type coil (feeding coil) 5 is coupled to the loop antenna of the antenna substrate 4 via an induction magnetic field as indicated by a magnetic flux φ1. The antenna substrate 4 is magnetically coupled to the IC card 20 as indicated by the magnetic flux φ2. With this structure, the RFID IC chip and the antenna coil can be substantially connected without using a contact pin or a flexible cable.

Japanese Patent No. 4325621

  However, in such a configuration, since the chip-type coil and the loop antenna are provided on different substrates, if the distance between them changes, the strength of magnetic coupling also changes, resulting in variations in communication characteristics. May occur. In addition, a space for arranging the chip-type coil and the loop antenna is necessary, but there may be a case where a sufficient space cannot be secured in the terminal housing.

  An object of the present invention is to provide a small antenna device that can obtain stable communication characteristics and can be accommodated in a limited space, and a communication terminal device including the antenna device.

(1) The antenna device of the present invention
A printed wiring board having a ground conductor provided on a surface layer or an inner layer of the insulating base material, with an insulating base material as a base body;
On the surface layer or inner layer of the printed wiring board, a feeding coil patterned in a coil shape,
A power supply element mounted on the printed wiring board and connected to the power supply coil ,
The ground conductor has, in part, a loop coupling portion having a first end and a second end,
The first end and the second end of the feeding coil are connected to two input / output terminals of the feeding element, respectively.
The feeding coil is coupled to the loop coupling portion of the ground conductor via an electromagnetic field.

  According to this configuration, since the ground conductor of the printed wiring board is used as a radiator for transmitting and receiving radio signals, and the feeding coil is provided on the printed wiring board, the distance between the feeding coil and the radiator is large. There is no variation, and variations in the degree of electromagnetic field coupling between the feeding coil and the radiation plate are reduced.

(2) It is preferable that a capacitive element is provided between the first end and the second end. With this configuration, a resonance circuit is formed by the inductance component of the loop-shaped coupling portion of the ground conductor and the capacitance component of the chip capacitor, and the loop-shaped coupling portion acts as a resonator, and the resonance frequency is within the use frequency band (for example, HF). The efficiency can be improved and the maximum readable distance can be increased.

(3) It is preferable that the loop-shaped coupling portion is formed by a notch provided in the ground conductor. With this configuration, it is not necessary to independently provide a loop-shaped coupling portion with a special conductor pattern, and the size can be easily reduced.

(4) It is preferable that the coil opening of the feeding coil overlaps with the opening of the loop coupling portion. With this configuration, the coupling between the feeding circuit and the ground conductor and the coupling between the feeding coil and the loop-shaped coupling portion are further enhanced.

(5) The feeding coil is a laminated coil formed by laminating a plurality of loop patterns, and the first end surface and the second end surface of the laminated coil are the first main surface side and the second end surface of the ground conductor. It is preferably located on the main surface side. With this configuration, it is possible to maintain the necessary degree of electromagnetic field coupling between the feeding coil and the loop coupling portion while reducing the planar dimension of the feeding coil.
(6) When the printed wiring board is viewed in plan, it is preferable that at least a part of the power feeding element does not overlap with a coil opening of the power feeding coil.

( 7 ) The communication terminal device of the present invention
A printed wiring board having a ground conductor provided on a surface layer or an inner layer of the insulating base material, with an insulating base material as a base body;
On the surface layer or inner layer of the printed wiring board, a feeding coil patterned in a coil shape,
A power feeding element mounted on the printed wiring board and connected to the power feeding coil;
A housing for storing the printed wiring board,
The ground conductor has, in part, a loop coupling portion having a first end and a second end,
The first end and the second end of the feeding coil are connected to two input / output terminals of the feeding element, respectively.
The feeding coil is coupled to the loop coupling portion of the ground conductor via an electromagnetic field.

  According to the above-described structure, a small communication terminal device having a small variation in electromagnetic field coupling between the feeding coil and the radiation plate and having stable communication characteristics is configured.

  According to the present invention, the ground conductor of the printed wiring board is used as a radiator for transmitting and receiving radio signals, and the feeding coil is provided on the printed wiring board, so that the distance between the feeding coil and the radiator is large. There is no variation, and variation in the electromagnetic field coupling between the feeding coil and the radiator is small. Therefore, it is possible to realize a small antenna device and a communication terminal device having stable communication characteristics.

FIG. 1A is a plan view of the antenna device and the communication terminal device of the first embodiment. FIG. 1B is a cross-sectional view of the antenna device and the communication terminal device of the first embodiment. FIG. 2 is a schematic perspective view of the antenna device according to the first embodiment. FIG. 3 is a schematic plan view of the antenna device according to the first embodiment. FIG. 4 is a diagram illustrating a state of current flowing through the power feeding coil 112 and the ground conductor 111 due to the coupling between the power feeding coil 112 and the loop-shaped coupling portion of the opening AP of the ground conductor 111. FIG. 5A is a plan view of the antenna device of the second embodiment, and FIG. 5B is a sectional view thereof. FIG. 6 is a longitudinal sectional view of the reader / writer 1 for a non-contact IC card described in Patent Document 1. In FIG.

<< First Embodiment >>
The communication terminal device of the first embodiment is a mobile communication terminal equipped with an NFC (Near Field Communication) system as an HF band RFID system.

  FIG. 1A is a plan view of the antenna device 206 and the communication terminal device 306 of the first embodiment, and FIG. 1B is a cross-sectional view thereof. FIG. 2 is a schematic perspective view of the antenna device 206 according to the first embodiment. FIG. 3 is a schematic plan view of the antenna device 206.

  The communication terminal device according to the first embodiment has a first printed wiring board 71, a second printed wiring board 81, a battery pack 83, and the like mounted in a casing (exterior). The first printed wiring board 71 and the second printed wiring board 81 are mounted with various functional elements and functional circuits such as a cellular antenna 72, a liquid crystal display element drive circuit, and a power supply control circuit. These functional elements and functional circuits are configured as surface mount components. On the printed wiring boards 71 and 81, wiring patterns for connecting these functional elements and functional circuits are three-dimensionally formed.

  The first printed wiring board 71 and the second printed wiring board 81 are made of a flame-retardant insulating base material such as an epoxy resin. These printed wiring boards 71 and 81 have a multilayer structure, and a ground conductor is provided in the inner layer over almost the entire area of the printed wiring boards 71 and 81. The ground conductor is used as a ground conductor for the various functional elements and functional circuits described above.

  An opening is provided in the vicinity of the end of the ground conductor 111 of the first printed wiring board 71, and a slit SL that connects the opening AP and the end of the ground conductor is formed. The slit SL connects the opening AP of the ground conductor 111 and the adjacent side of the opening AP. The opening AP and the slit SL provided in the ground conductor 111 are defined by a notch CP formed in the planar ground conductor 111. Of the cutout CP of the ground conductor 111, the portions facing each other across the slit SL are used as the first end and the second end, and the inner periphery of the opening AP is used as the loop coupling portion.

  A feeding coil 112 is provided in the inner layer of the first printed wiring board 71. The feeding coil 112 is patterned simultaneously with other various wirings formed on the first printed wiring board 71, and is patterned into a single-layer coil shape of a plurality of turns. The first end and the second end of the power feeding coil 112 are respectively connected to two input / output terminals of the NFC IC chip 73 which is a power feeding element. The coil opening of the feeding coil 112 has the same shape and size as the opening AP of the ground conductor 111. That is, the coil pattern of the feeding coil 112 overlaps with the periphery of the opening of the ground conductor 111. The NFC IC chip 73 may be a bare chip or a package IC. A chip capacitor 74 is connected in parallel to the power supply coil 112 between the NFC IC chip 73 and the power supply coil 112, and a resonance circuit is configured by the power supply coil 112 and the chip capacitor 74. The resonance frequency of this resonance circuit is set to be substantially equal to the frequency of the transmission / reception signal. A filter element and a matching element may be further provided between the NFC IC chip 73 and the feeding coil 112.

  FIG. 4 is a diagram illustrating a state of current flowing through the power feeding coil 112 and the ground conductor 111 due to the coupling between the power feeding coil 112 and the loop-shaped coupling portion of the opening AP of the ground conductor 111.

  As shown in FIG. 4, when a signal current flows through the feeding coil 112, an induced current flows around the edge of the ground conductor 111 through the opening AP and the slit SL of the ground conductor 111. That is, when a high frequency signal is sent from the NFC IC chip 73 to the power feeding coil 112 in the transmission mode, the induced current of the current that has flowed through the power feeding coil 112 flows to the loop-shaped coupling portion of the ground conductor and flows to the loop-shaped coupling portion. The current is guided to the whole (or part) of the ground conductor 111, and the ground conductor 111 acts as a radiator for the high-frequency signal. In the reception mode, when a high-frequency signal is received by the ground conductor 111, a current flows through the loop coupling portion of the ground conductor 111, and the induced current is received by the feeding coil 112, and this induced current is applied to the NFC IC chip 73. Sent.

  A chip capacitor 74 is connected to the loop coupling portion of the ground conductor. The first end of the slit SL of the ground conductor 111 is connected to the first terminal of the chip capacitor, and the second end of the slit SL is connected to the second terminal of the chip capacitor. As a result, a resonance circuit is formed by the inductance component of the loop-shaped coupling portion of the ground conductor and the capacitance component of the chip capacitor 74, and the ground conductor acts as a part of the resonator, and the resonance frequency is the HF that is the use frequency. By approaching the belt, the maximum reading distance can be increased.

  Although not shown, a display element such as a liquid crystal display panel electrostatically shielded by a metal plate is provided on the surface S2 side of the casing 91. Therefore, the directivity direction of the NFC antenna device is It is the back surface S1 side. In particular, the communication distance in the side surface direction where the feeding coil 112 and the slit SL are provided is increased. Therefore, the feeding coil 112 is preferably disposed in the vicinity of the end of the casing 91 on the side where the directivity is provided, and the slit SL is also preferably extended toward the end of the casing 91.

  As described above, according to the antenna device and the communication terminal device of the present embodiment, the ground conductor 111 of the first printed wiring board 71 is used as a radiator for transmitting and receiving a high-frequency signal, and the first feeding coil 112 is the same. Since it is provided on the printed wiring board 71, the distance between the feeding coil 112 and the ground conductor (radiating body) 111 is substantially determined when the first printed wiring board 71 is manufactured, and the assembly accuracy and casing of the communication terminal device are determined. Due to the warp and deformation, the distance between the feeding coil and the ground conductor (radiating body) is unlikely to vary. Therefore, the degree of electromagnetic field coupling between the feeding coil 112 and the loop coupling portion is not likely to vary, and stable communication characteristics can be obtained.

  In addition, since both the feeding coil 112 and the ground conductor (radiating body) 111 are provided on the first printed wiring board 71, in other words, the feeding coil separate from the printed wiring board and the radiation separate from the printed wiring board. Since it is not the structure which provides a body, it is not necessary to ensure a big space for an antenna apparatus in a housing, and it contributes greatly to size reduction of an antenna apparatus and by extension, a communication terminal device.

  Further, since the flowing out solder, processing waste or the like is not undesirably sandwiched between the feeding coil and the loop-shaped coupling portion of the ground conductor, the communication characteristics can be further stabilized.

  In addition, since the feeding coil 112 and the ground conductor 111 are not connected in direct current, even if surge noise such as ESD is applied to the ground conductor 111, it is difficult for surge noise to enter the NFC IC chip 73, and for NFC. The surge resistance of the IC chip 73 is improved. Further, even if noise enters the ground conductor 111 from various functional circuits, the characteristics of the NFC IC chip 73 are not greatly affected by the noise.

  In the present embodiment, the feeding coil 112 is provided on the front surface S2 side of the housing 91 when viewed from the ground conductor 111, and the NFC IC chip 73 is mounted on the back surface S1 side of the housing 91 when viewed from the ground conductor 111. . Therefore, the NFC IC chip 73 and the power feeding coil 112 are connected without passing through the layer of the ground conductor 111.

<< Second Embodiment >>
FIG. 5A is a plan view of the antenna device according to the second embodiment, and FIG. 5B is a sectional view thereof.

  In the second embodiment, the feeding coil 112 is a laminated coil formed by laminating a plurality of loop patterns. The first end surface of the multilayer coil is located on the first main surface side of the ground conductor 111, and the second end surface of the multilayer coil is located on the second main surface side of the ground conductor 111. With such a structure, the required electromagnetic coupling degree between the feeding coil 112 and the loop coupling portion of the ground conductor 111 can be maintained while reducing the planar dimension of the feeding coil 112.

<< Other embodiments >>
As mentioned above, although this invention was demonstrated based on specific embodiment, this invention is not limited to said embodiment.

  For example, the communication terminal device may be various devices having a wireless communication function, such as a tablet-type terminal and a notebook PC, in addition to a mobile communication terminal. Various elements such as a liquid crystal display element may be mounted on the terminal housing in addition to the printed wiring board and the battery pack.

  The ground conductor may be provided not on the inner layer of the printed wiring board but on the surface layer. When the ground conductor is formed over a plurality of layers, each ground conductor layer may be used as a radiator, or only the outermost or lowermost ground conductor may be used as a radiator. .

  The outer shape of the ground conductor is not limited to a rectangular shape, and can take various shapes according to the shape of the printed wiring board and the wiring patterns of various functional elements and functional circuits.

  The feeding coil may also be provided on the surface layer instead of the inner layer of the printed wiring board. The number of layers and the number of turns of the feeding coil can be appropriately designed according to the required inductance value.

  The loop-shaped coupling portion provided in the ground conductor is not limited to the one constituted by the opening portion and the slit portion. For example, a concave portion is provided in the edge portion of the ground conductor, and the peripheral surface of the concave portion is used as the loop-shaped coupling portion. May be used. Further, a loop-shaped conductor may be added to the edge of the ground conductor, and this may be used as a loop-shaped coupling portion. The widths of the opening and the slit may be the same.

  It is preferable that at least a part of the coil opening of the feeding coil 112 and the opening AP of the ground conductor 111 overlap in plan view, and the shape and size of the coil opening of the feeding coil 112 are not necessarily the opening AP of the ground conductor 111. Need not be the same shape or size. For example, the coil opening of the feeding coil 112 may be larger than the opening AP of the ground conductor 111, or the coil opening of the feeding coil 112 may be smaller than the opening AP of the ground conductor 111. When the outer dimension of the feeding coil 112 is smaller than the opening AP of the ground conductor 111, the feeding coil 112 may be formed in the same layer as the ground conductor 111 (inside the opening AP).

  The arrangement position of the feeding coil 112 with respect to the ground conductor 111 may be on the back surface S1 side of the casing 91 when viewed from the ground conductor 111. In that case, the NFC IC chip 73 is also preferably mounted on the rear surface S1 side of the housing.

AP ... Opening CP ... Notch S1 ... Back surface S2 ... Front surface SL ... Slit 71 ... First printed wiring board 72 ... Cellular antenna 73 ... NFC IC chip 74 ... Chip capacitor 81 ... Second printed wiring board 83 ... Battery pack 91 ... Housing 110 ... Printed wiring board 111 ... Ground conductor 112 ... Feed coil 206 ... Antenna device 306 ... Communication terminal device

Claims (7)

A printed wiring board having a ground conductor provided on a surface layer or an inner layer of the insulating base material, with an insulating base material as a base body;
On the surface layer or inner layer of the printed wiring board, a feeding coil patterned in a coil shape,
A power supply element mounted on the printed wiring board and connected to the power supply coil,
The ground conductor has, in part, a loop coupling portion having a first end and a second end,
The first end and the second end of the feeding coil are connected to two input / output terminals of the feeding element, respectively.
The antenna device, wherein the feeding coil is coupled to the loop coupling portion of the ground conductor via an electromagnetic field.   The antenna device according to claim 1, wherein a capacitive element is provided between the first end and the second end.   The antenna device according to claim 1, wherein the loop coupling portion is formed by a notch provided in the ground conductor.   The antenna device according to claim 1, wherein the coil opening of the feeding coil overlaps with the opening of the loop coupling portion.   The feeding coil is a laminated coil formed by laminating a plurality of loop patterns, and the first end surface and the second end surface of the laminated coil are the first main surface side and the second main surface side of the ground conductor. The antenna device according to claim 1, which is located at The antenna device according to any one of claims 1 to 5, wherein when the printed wiring board is viewed in plan, at least a part of the power feeding element does not overlap with a coil opening of the power feeding coil. A printed wiring board having a ground conductor provided on a surface layer or an inner layer of the insulating base material, with an insulating base material as a base body;
On the surface layer or inner layer of the printed wiring board, a feeding coil patterned in a coil shape,
A power feeding element mounted on the printed wiring board and connected to the power feeding coil;
A housing for storing the printed wiring board,
The ground conductor has, in part, a loop coupling portion having a first end and a second end,
The first end and the second end of the feeding coil are connected to two input / output terminals of the feeding element, respectively.
The communication terminal device, wherein the power supply coil is coupled to the loop coupling portion of the ground conductor via an electromagnetic field.

Images