JP2007324961A - Antenna unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna unit capable of lessening the deterioration of antenna characteristics to reduce the lowering of a communication distance when mounting an antenna for near distance communication in high density packaged electronic equipment. <P>SOLUTION: The antenna unit 3 is incorporated together with a circuit board 2 and an electric component in a housing. It includes the antenna 32 and a dielectric sheet 31. The electric sheet 31 is inserted between the antenna 32 and the circuit board 2 disposed in the vicinity of the antenna 32. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a communication apparatus that performs communication at a close distance mainly by non-contact, and particularly relates to an antenna unit that is built in a housing of the communication apparatus together with a circuit board and electrical components.

  Wireless communication systems at close distances using antennas, such as RFID and non-contact IC cards, are widely used. This system is also called proximity contactless communication, and there is an increasing demand for the development of a small and high performance antenna for use in small electronic devices such as mobile phone terminals.

  As an example of an antenna used for this purpose, Patent Document 1 discloses that the communication distance is increased by expanding the conductor cross-sectional area of the antenna with a limited outer shape by using a multilayer substrate manufacturing technique, and An invention relating to an antenna that can be manufactured at low cost is described. In such an antenna structure composed of a multilayer substrate, each conductor layer laminated with an insulating resin layer interposed therebetween is patterned into a coil shape, and the coil patterns of each layer formed in multiple layers via the insulating resin layer are arranged. The antenna substrate is configured to function as a single coil by being electrically connected by through-hole plating layers formed at a predetermined interval. Further, it is described that the outer diameter of the coil pattern and the number of layers to be laminated can be arbitrarily increased or decreased according to the communication distance.

  On the other hand, in order to prevent the performance of the antenna mounted on the apparatus from deteriorating, Patent Document 2 discloses that a proximity non-contact communication device having a proximity non-contact communication function suppresses magnetic noise in the antenna for proximity non-contact communication. The antenna unit is composed of a sheet-like magnetic body and a sheet-like conductor, which can reduce the influence of a metal plate installed close to the antenna. It is described that deterioration can be reduced.

JP 2003-066762 A JP 2005-122595 A

  In an electronic device in which electronic components of recent years are mounted with high density, when an antenna for near field communication is to be mounted, the antenna placement unit is usually equipped with various types of components such as a casing, a circuit board, or an electric component such as a battery. Things will be close to each other, and ideal communication characteristics when an antenna exists alone will not be maintained, and characteristic deterioration will be unavoidable. Further, it is desirable that there is a degree of freedom that can be adjusted so as to obtain optimal transmission / reception characteristics according to the situation in which the antenna is arranged and mounted.

  In the antenna described in Patent Document 1, it is considered that there is no problem with the characteristics of an independent antenna alone, but degradation of the antenna characteristics when mounted on an actual device is not considered, and in that case the antenna alone It is not always possible to fully exhibit the characteristics.

  In addition, the antenna described in Patent Document 2 describes an antenna unit in which a sheet-like magnetic body and a sheet-like conductor are superimposed on an antenna in order to reduce the influence of a nearby metal plate or the like. When actually mounted in a device, there are many deterioration factors as described above. Therefore, the antenna unit is not sufficient when considering the degree of freedom in adjusting the characteristics in the mounted state.

  The present invention has been made in view of such a problem, and an object thereof is to minimize a decrease in the communication distance of an antenna when mounted in a device.

  That is, an object of the present invention is to provide an antenna unit that can reduce deterioration in antenna characteristics and decrease in communication distance when mounting an antenna for near-field communication in an electronic device mounted with high density There is to do.

  In order to solve the above problems, an antenna unit of the present invention is an antenna unit that is built in a casing together with a circuit board and an electrical component, and includes an antenna and a dielectric sheet, and the dielectric sheet includes the antenna and the antenna unit. It is inserted into at least one of the housing, the circuit board, or the electrical component.

  A magnetic layer may be provided between the dielectric sheet and the antenna.

  Moreover, you may provide a conductor layer in at least any one between the said dielectric material sheet, the said housing | casing, the said circuit board, or the said electrical component.

  The antenna may be any one of a loop antenna, a patch antenna, and a linear antenna formed in a planar shape.

  If a conductor such as a metal is present in the vicinity of the antenna, the radiation field of the antenna is reflected by the conductor, thereby affecting the radiation characteristics of the antenna. In other words, if there is a radio wave reflection surface at a distance sufficiently smaller than the wavelength of the radiated radio wave, the radiated radio wave is reflected with the phase reversed by 180 degrees, so that the electric field of the radio wave radiated directly from the antenna is canceled. As a result, the characteristics of the antenna are greatly deteriorated. This effect is more significant as the antenna and conductor are closer together.

  Therefore, in the present invention, a conductor sheet is provided substantially by providing a dielectric sheet having a certain dielectric constant between the antenna and the conductor surface or a magnetic layer having a certain degree of permeability and the dielectric sheet. This has the same effect as increasing the electrical length of the gap between the antenna and the antenna, and moving away the conductor that apparently deteriorates the antenna characteristics.

  In the present invention, the antenna characteristics are fixed by providing a conductor layer between the dielectric sheet and the housing or the circuit board or the electrical component, and the conductor layer and the circuit board are assembled when the communication device is assembled. Even if the distance between and varies, it can be prevented from being affected.

  As described above, according to the present invention, when an antenna for proximity communication is mounted on an electronic device mounted with high density, due to the proximity effect of various cases such as a housing, a circuit board, or a battery of the antenna placement unit. It is possible to provide an antenna unit capable of reducing the deterioration of antenna characteristics and the communication distance.

  Embodiments according to the present invention will be described below with reference to the drawings.

Example 1
FIG. 1 is a diagram schematically showing a cross-section of an example of the structure of a mobile phone terminal in which the antenna unit of the present invention is built, and a circuit board 2 and a circuit board 2 are separated from each other by a gap G in the housing 1. The antenna unit 3 for proximity communication arranged is mounted. The arrow indicates the radiation direction of the radio wave from the antenna.

  FIG. 2 is a diagram schematically showing a cross section of a first embodiment of an antenna unit 3 according to the present invention used in the mobile phone terminal of FIG. The antenna unit 3 of the present embodiment shows a case where the surface opposite to the radio wave radiation direction of the antenna is installed close to the circuit board. As shown in FIG. The body sheet 31 and the antenna 32 are arranged. In the present embodiment, as the antenna 32, a planar loop antenna, a patch antenna, a linear antenna, or the like formed of a coil pattern formed in multiple layers as shown in Patent Document 1 can be used. Further, the gap G between the circuit board 2 and the antenna 32 is usually several tens of μm to 1 mm, and the frequency of radio waves radiated from the antenna 32 for near field communication is 100 kHz to 2.5 GHz. The gap G is sufficiently small compared to the wavelength. Therefore, the radio wave radiated from the antenna 32 is affected by the radio wave reflected by the circuit board 2 and returning.

In the present embodiment, an effect similar to that of moving the circuit board 2 away is obtained by inserting the dielectric sheet 31 into the gap. As the dielectric sheet 31, a sheet or an organic film made of a composite dielectric material in which a dielectric powder having a high dielectric constant is mixed with FEP (fluorinated ethylene propylene) resin or the like can be used. t can be several tens of μm to 1 mm. In this case, since the relative dielectric constant ε of the dielectric sheet 31 is larger than the relative dielectric constant 1 of air, the electrical length of the gap G is increased by t × (ε) ^1/2 , and the influence due to the presence of the circuit board 2 is affected. Can be small.

It should be noted that if the relative dielectric constant ε of the dielectric sheet 31 is too large, it affects the impedance when power is supplied to the antenna and deteriorates the antenna characteristics. Therefore, the optimum value for the value of t × (ε) ^1/2 Exists. In this embodiment, for example, ε is about 5 to 20, and t is about 0.1 to 0.5 mm.

(Example 2)
FIG. 3 is a diagram schematically showing a cross section of a second embodiment of the antenna unit 3 according to the present invention used in the mobile phone terminal of FIG. As shown in FIG. 3, the antenna unit 3 of the present embodiment is configured by disposing a dielectric sheet 31, a magnetic layer 33, and an antenna 32 in order from the side close to the circuit board 2. In the present embodiment, as the antenna 32, the same antenna as in the first embodiment can be used.

  In the present embodiment, an effect similar to that of moving the circuit board 2 away is obtained by inserting the dielectric sheet 31 and the magnetic layer 33 into the gap between the antenna 32 and the circuit board 2. As the dielectric sheet 31, a dielectric sheet made of the same material as that used in the first embodiment can be used. The magnetic layer 33 may be inserted as an independent sheet, and may be provided integrally with the antenna 32 or integrally with the dielectric sheet 31. As a material for the magnetic layer 33, a sheet of a composite magnetic material such as Busterade (registered trademark), a ferrite plating layer, or the like can be used.

In this embodiment, if the relative permittivity of the dielectric sheet 31 is ε1, the relative permeability is μ1, the thickness is t1, the relative permittivity of the magnetic layer is ε2, the relative permeability is μ2, and the thickness is t2. , T1 × (ε1 · μ1) ^1/2 + t2 × (ε2 · μ2) ^1/2 increases the electrical length of the gap G, and the influence of the presence of the circuit board 2 can be reduced.

(Example 3)
FIG. 4 is a diagram schematically showing a cross section of a third embodiment of the antenna unit 3 according to the present invention used in the mobile phone terminal of FIG. As shown in FIG. 4, the antenna unit 3 of the present embodiment is configured by arranging a conductor layer 34, a dielectric sheet 31, and an antenna 32 in order from the side close to the circuit board 2. In the present embodiment, the antenna 32 can be the same antenna as in the first embodiment, and the material of the dielectric sheet 31 is the same as that in the first embodiment.

  In the present embodiment, by providing the conductor layer 34 in a portion close to the circuit board 2, the characteristics as the antenna unit are fixed so as not to be affected by the presence of the circuit board 2, and when the communication device is assembled, Even if the distance to the circuit board varies, it is not affected. Here, in order to reduce the influence of the reflection of the conductor layer 34 on the radiation characteristics of the antenna 32, the dielectric sheet 31 is inserted as in the first embodiment, and the effect is the same as in the first embodiment. However, in the case of the present embodiment, the gap between the antenna 32 and its reflecting surface (conductor layer 34) is smaller than G.

  The conductor layer 34 can be provided integrally with the dielectric sheet 31. In that case, a metal plating layer, a metal vapor deposition film, or the like can be used. Moreover, you may use the isolate | separated metal sheet. The thickness is sufficient if the mechanical strength is maintained.

Example 4
FIG. 5 is a diagram schematically showing a cross section of a fourth embodiment of the antenna unit 3 according to the present invention used in the mobile phone terminal of FIG. As shown in FIG. 5, the antenna unit 3 of this embodiment is configured by arranging a conductor layer 34, a dielectric sheet 31, a magnetic layer 33, and an antenna 32 in order from the side close to the circuit board 2. It is. In the present embodiment, the antenna 32 can be the same antenna as in the first embodiment, and the configurations and materials of the dielectric sheet 31 and the magnetic layer 33 are the same as those in the second embodiment.

  Also in the present embodiment, as in the third embodiment, by providing the conductor layer 34 in a portion close to the circuit board 2, the characteristics as the antenna unit are fixed so as not to be affected by the presence of the circuit board 2, and the circuit board and Even if the distance varies, it is not affected. Here, in order to reduce the influence of the reflection of the conductor layer 34 on the radiation characteristics of the antenna 32, the dielectric sheet 31 and the magnetic layer 33 are inserted as in the second embodiment, and the effect is the same as in the second embodiment. It is. However, in the case of the present embodiment, the gap between the antenna 32 and its reflecting surface (conductor layer 34) is smaller than G.

  The conductor layer 34 is configured in the same manner as in Example 3, and can be provided integrally with the dielectric sheet 31. Alternatively, a separated metal sheet may be used.

  In the above-described first to fourth embodiments of the antenna unit according to the present invention, the case where the surface opposite to the radio wave radiation direction of the antenna is installed close to the circuit board 2 has been described. When installed close to the case, the dielectric sheet 31 is inserted between the antenna and the case, and when the above surface of the antenna is set close to an electrical component such as a battery. By inserting the dielectric sheet 31 between the antenna and the electrical component, the same effects as those of the above embodiments can be obtained.

  Further, in the mounting state in the communication device to which the present invention is applied, the above-described surface of the antenna is both the case and the circuit board, or both the case and the electric component, or both the circuit board and the electric component, or the case. It may be installed close to any body, circuit board, or electrical component. In such a case, a dielectric sheet is inserted between the casing, circuit board, electrical component, and antenna that are in close proximity to each other. Is done.

  Needless to say, the materials, thicknesses, and the like of the dielectric sheet, magnetic layer, and conductor layer used in the antenna unit of the present invention are not limited to the above-described embodiments. For example, ceramic or the like can be used as the material of the dielectric sheet.

  In the above-described embodiments, the cellular phone terminal is described as an example of the antenna unit mounting device. However, the present invention is not particularly limited to this, and the reader / writer for non-contact communication, the non-contact IC card, etc. The proximity communication device may be used.

  As described above, when an antenna for near field communication is mounted on an electronic device mounted with high density according to the present invention, an antenna unit capable of reducing deterioration in antenna characteristics and reduction in communication distance can be obtained. It is done.

  Further, the antenna is not limited to the antenna for close-range communication, and the antenna used for the communication device such as TV, radio, portable terminal, etc. is also the antenna effect due to the proximity effect of various things such as the housing of the antenna placement unit, the circuit board, or the battery. When characteristic deterioration occurs, the present invention is an effective means as an improvement means.

The figure which shows typically the cross section of an example of the structure of the mobile telephone terminal in which the antenna unit of this invention is incorporated. The figure which shows typically the cross section of the 1st Example of the antenna unit by this invention used for the mobile telephone terminal of FIG. The figure which shows typically the cross section of the 2nd Example of the antenna unit by this invention used for the mobile telephone terminal of FIG. The figure which shows typically the cross section of the 3rd Example of the antenna unit by this invention used for the mobile telephone terminal of FIG. The figure which shows typically the cross section of the 4th Example of the antenna unit by this invention used for the mobile telephone terminal of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 2 Circuit board 3 Antenna unit 31 Dielectric sheet 32 Antenna 33 Magnetic layer 34 Conductor layer

Claims (4)

  An antenna unit built in a casing together with a circuit board and electrical components, the antenna unit having an antenna and a dielectric sheet, the dielectric sheet being interposed between the antenna and the casing or the circuit board or the electrical component An antenna unit that is inserted into at least one of the above.   The antenna unit according to claim 1, further comprising a magnetic layer between the dielectric sheet and the antenna.   3. The antenna unit according to claim 1, wherein a conductor layer is provided at least between the dielectric sheet and the housing, the circuit board, or the electrical component.   The antenna unit according to any one of claims 1 to 3, wherein the antenna is any one of a loop antenna, a patch antenna, and a linear antenna formed in a planar shape.

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