JP5282898B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device used for an RFID (Radio Frequency IDentification) reading / writing device that performs non-contact communication with a data carrier.

  In recent years, an RFID system comprising a data carrier such as a non-contact IC card or IC tag composed of a transmission / reception antenna and an IC chip, and an RFID reader / writer, and performing non-contact communication by electromagnetic induction or radio waves, It is widely used for personal authentication, article management, process management, and the like. In general, there are three main types of communication frequency bands such as electromagnetic induction or radio waves used in RFID systems: 13.56 MHz band, 800 MHz to 1000 MHz band, and 2400 MHz to 2500 MHz band. Based on this, a system is constructed by selecting a communication frequency band to be used.

  The communication frequency 13.56 MHz band is generally used in a communication system using electromagnetic induction (hereinafter referred to as an electromagnetic induction system). In this communication method, the communication distance is shortened, but relatively large power can be stably supplied to the data carrier. For this reason, it is used for security applications that require arithmetic processing in an IC chip built in a data carrier.

  Further, the communication frequencies of 800 MHz to 1000 MHz and 2400 MHz to 2500 MHz are used in radio communication systems (hereinafter referred to as radio systems). This communication method is characterized by a long communication distance. A transmission / reception antenna used for a data carrier used in a radio wave system is often a dipole antenna having a length that is one-half the wavelength of a radio wave to be used. Therefore, the size of the transmission / reception antenna of the data carrier can be made smaller when the communication frequency 2400 MHz to 2500 MHz band is used than when the communication frequency 800 MHz to 1000 MHz band is used, and the data carrier itself is downsized. can do. On the other hand, the spatial attenuation of radio waves by the transmission / reception antenna of the data carrier is smaller when the communication frequency 800 MHz to 1000 MHz band is used than when the communication frequency 2400 MHz to 2500 MHz band is used. Can do.

  By the way, the antenna device used for the RFID reading / writing device has different antenna shapes depending on the communication frequency band and communication method to be used. In general, as an antenna device of an RFID reading / writing device used in an electromagnetic induction method with a communication frequency of 13.56 MHz, a loop antenna for both transmission and reception, which is composed of a loop conductor placed in one plane, is used. For example, Patent Document 1 discloses a technique in which a loop antenna for both transmission and reception is used as a reader / writer of a non-contact data carrier system, that is, an antenna device of an RFID reader / writer.

  Further, the antenna device of the RFID reading / writing device used in the radio frequency system of the communication frequency 800 MHz to 1000 MHz band and the communication frequency 2400 MHz to 2500 MHz band is the same as the transmission / reception antenna of the data carrier corresponding to each communication frequency band. A transmission / reception dipole antenna, a transmission / reception antenna configured by combining a reflector with the dipole antenna, a transmission / reception patch antenna, or the like is used. For example, Patent Document 2 discloses a technique using a patch antenna that receives circularly polarized waves as an interrogator of a non-contact IC tag system, that is, an antenna device of an RFID reader / writer.

Japanese Patent Laid-Open No. 10-224277 (FIG. 8) JP-A-11-308147 (page 5, paragraph 0026)

  What kind of communication frequency band, communication method, or antenna device is used in the RFID system is not particularly important for users who use the RFID system, and the communication frequency band, communication method, Alternatively, it is preferable that the antenna device or the like can be operated smoothly without the user being aware of it.

  When communicating with a data carrier having a different communication frequency band or communication method, an RFID reader / writer corresponding to each communication frequency band or communication method is required individually, increasing the RFID system introduction cost, or Inefficiency during operation is a problem. In order to cope with this, an RFID system that can be operated by a single RFID reading / writing device by arranging a plurality of antenna devices corresponding to a plurality of communication frequency bands or a plurality of communication systems in the RFID reading / writing device. Is realized.

  However, in this case, it is necessary to prepare a plurality of different antenna devices having an optimum shape or size corresponding to the communication frequency band or communication method to be used. For example, when an RFID system is constructed using an RFID reader / writer that performs communication in three communication frequency bands of a communication frequency of 13.56 MHz, a communication frequency of 800 MHz to 1000 MHz, and a communication frequency of 2400 MHz to 2500 MHz, The reading / writing device has various shapes and dimensions, such as an antenna device made up of an electromagnetic induction type loop antenna, an antenna device made up of a radio wave type dipole antenna, and an antenna device made up of a radio wave type patch antenna. It becomes a complicated configuration in which three types of antenna devices are mixed.

  Further, as a means for avoiding such a complicated configuration, a loop-shaped antenna element capable of communicating in a communication frequency of 13.56 MHz, a loop-shaped antenna element capable of communicating in a communication frequency of 800 MHz to 1000 MHz, and a communication frequency It has loop-shaped antenna elements that can communicate in the band of 2400 MHz to 2500 MHz, and the total length of each antenna element has a length that is a quarter of the wavelength corresponding to the communication frequency to be used. There has been proposed a small and low-cost antenna device that is arranged concentrically and performs each communication by an electromagnetic induction method.

  However, the above-described technique performs communication using a loop antenna element that can communicate in the communication frequency range of 800 MHz to 1000 MHz and a loop antenna element that can communicate in the communication frequency range of 2400 MHz to 2500 MHz among the three communication frequency bands. The total length of each antenna element or the arrangement thereof is determined in accordance with the communication conditions at the time, and when communication is performed using a loop-shaped antenna element capable of communication in a communication frequency of 13.56 MHz, a magnetic field necessary for communication You may not get the strength of.

  Although it is possible to increase the magnetic field strength to some extent by increasing the total length of the loop-shaped antenna element capable of communicating in the communication frequency 13.56 MHz band and increasing the number of turns of the antenna element, for example, the communication frequency 13.56 MHz band If the loop-shaped antenna elements that can communicate with each other are arranged on the outermost side of the concentric circle, the proportion of the antenna elements on the substrate increases, which is not suitable for downsizing.

  In addition, when there is metal or the like around the loop-shaped antenna element, for example, on the opposite side of the detection surface of the antenna device incorporating the loop-shaped antenna element, there is a problem that the antenna characteristics are deteriorated due to the magnetic effect. Become. That is, the magnetic energy generated by the loop-shaped antenna element is consumed as a current inside the surrounding metal or the like, and the strength of the magnetic field necessary for communication that was originally assumed cannot be obtained, and the communication distance May decrease. In particular, the influence is remarkable in the case of communication in the 13.56 MHz band having a wide magnetic field area.

  In the future, RFID readers / writers will be able to be mounted on devices such as mobile phones and watches for the ubiquitous society where information on data carriers such as IC tags can be accessed anytime and anywhere. The downsizing of the writing / writing device is indispensable, and accordingly, the downsizing of the antenna device incorporated in the RFID reading / writing device is required.

  The present invention has been made in view of such problems, and an object of the present invention is to provide at least three communication frequencies of a communication frequency band of 13.56 MHz, a communication frequency of 800 MHz to 1000 MHz, and a communication frequency of 2400 MHz to 2500 MHz. At least three loop-shaped antenna elements corresponding to each of the communication frequency bands are provided so that communication can be performed by electromagnetic induction in the band, and the total length of each antenna element corresponds to the communication frequency to be used. They have a length of one-fourth of the wavelength, are arranged concentrically on one substrate, perform each communication by electromagnetic induction, and form a loop-shaped magnetic body into the three loop-shapes. Among the antenna elements of the above, in the vicinity of the lower part of the loop-shaped antenna element capable of communication in the communication frequency 13.56 MHz band, the surrounding metal RFID which is capable of suppressing magnetic influences, increasing the strength of the magnetic field when communicating in the communication frequency 13.56 MHz band, suppressing deterioration of antenna characteristics, and being small and low cost. An object of the present invention is to provide an antenna device used for a reading / writing device.

  That is, according to the present invention, an antenna device used in an RFID read / write device that performs non-contact communication with a data carrier, the antenna device being a loop antenna that communicates at a frequency of at least 13.56 MHz band. A loop-shaped antenna element that communicates at a frequency of 800 MHz to 1000 MHz band and a loop-shaped antenna element that communicates at a frequency of 2400 MHz to 2500 MHz, and communicates at a frequency of 13.56 MHz band The total length of the antenna element is shorter than a quarter of the wavelength corresponding to the frequency, and the total length of the loop-shaped antenna element communicating at the frequency of the 800 MHz to 1000 MHz band is 4 of the wavelength corresponding to the frequency. Shorter than one-half length and the circumference of the 2400 MHz to 2500 MHz band The total length of the loop-shaped antenna element that communicates by number is shorter than a quarter of the wavelength corresponding to the frequency, and the loop-shaped antenna element that communicates at a frequency of the 13.56 MHz band, the 2400 MHz to 2400 MHz The loop-shaped antenna element that communicates at a frequency of 2500 MHz band and the loop-shaped antenna element that communicates at a frequency of 2400 MHz to 2500 MHz are in the same plane, and are concentric, concentric, and concentric. A loop-shaped magnetic body in the vicinity of the lower portion of the loop-shaped antenna element that is arranged and configured so as to have a shape, a concentric polygonal shape, or a substantially concentric polygonal shape and communicates at a frequency of the 13.56 MHz band. Is obtained.

  The antenna device of the present invention is used in an RFID reader / writer, and has at least three communication frequency bands, that is, at least a communication frequency of 13.56 MHz band, a communication frequency of 800 MHz to 1000 MHz, and a communication frequency of 2400 MHz to 2500 MHz. In order to be able to communicate with the data carrier, it is preferable to provide at least three loop antenna elements.

  The at least three loop-shaped antenna elements may be any of an antenna element for transmission, an antenna element for reception, or an antenna element for both transmission and reception. For example, an insulation-coated copper wire fixed on an insulating substrate Or the like, or a loop-shaped antenna element formed of a conductive pattern formed of copper foil or the like on an insulating substrate and wound for at least one turn.

  When the communication frequency bands to be used are the above three types, a loop antenna element that communicates at a frequency of 13.56 MHz band (hereinafter referred to as a first loop antenna element), and a communication at a frequency of 800 MHz to 1000 MHz band. Each of the total length of a loop-shaped antenna element (hereinafter referred to as a second loop antenna element) and a loop-shaped antenna element (hereinafter referred to as a third loop antenna element) communicating at a frequency of 2400 MHz to 2500 MHz band, It is preferable that the length is shorter than a quarter of the wavelength corresponding to each frequency.

  Further, each of the first loop antenna element, the second loop antenna element, and the third loop antenna element is disposed on the same plane, for example, on one surface of a flat insulating substrate. For example, a circular third loop antenna element is disposed at the center of the insulating substrate, and the circular second loop antenna element is separated from the circular third loop antenna element on the outside thereof. It is preferable that a circular first antenna element is disposed on the outer side of the circular second loop antenna element so as to be concentric. .

  In addition to the circular shape, each of the first loop antenna element, the second loop antenna element, and the third loop antenna element has a rectangular shape, a substantially rectangular shape, a concentric polygonal shape, or a concentric shape. Any of substantially polygonal shapes may be used, and according to the respective shapes, each of the first loop antenna element, the second loop antenna element, and the third loop antenna element is a concentric shape, It is preferable that they are arranged in the same plane so as to have a concentric substantially square shape, a concentric polygonal shape, or a concentric substantially polygonal shape.

  Further, in the vicinity of the lower part of the first loop antenna element, that is, on the side opposite to the detection surface of the antenna device, the portion of the first loop antenna element is disposed on the first loop antenna element. It is preferable to arrange a loop-shaped magnetic body processed according to the shape directly or at a distance. For example, when the shape of the first loop antenna element is circular, the first loop antenna element is formed of a sheet-like body having a band width and a certain thickness that can sufficiently cover the projected area of the first loop antenna element. A circular loop-shaped magnetic body is fixed directly on the back surface of the insulating substrate with an adhesive or the like, or a medium such as a spacer is disposed between the insulating substrate and the loop-shaped magnetic body to separate them. Each of them may be fixed with an adhesive or the like.

  As a result, the antenna device of the present invention can communicate in at least three communication frequency bands, and at least three loop antenna elements corresponding to each of the at least three communication frequency bands can be efficiently combined in the same plane. It is possible to reduce the size and cost because it can be arranged well and the area occupied by the antenna element can be reduced. At the same time, each of the total lengths of the at least three loop-shaped antenna elements is made shorter than a quarter length of the wavelength corresponding to the corresponding frequency, whereby the conductor constituting the at least three loop-shaped antenna elements is formed. The direction of the current flowing through each of the two is uniform, and a larger and more directional magnetic field can be generated.

  Furthermore, among the at least three loop-shaped antenna elements, a loop-shaped antenna element that communicates at a frequency of 13.56 MHz band, that is, a loop-shaped magnetic body is disposed near the lower portion of the first loop antenna element. Since the magnetic energy can be converged on the loop-shaped magnetic body, even if there is a metal or the like in the vicinity, the ratio of the magnetic field reaching the metal or the like can be reduced, and as a result, the magnetic energy can be reduced. Loss can be reduced. Therefore, in communication in the communication frequency 13.56 MHz band by the first loop antenna element, it is possible to suppress the deterioration of the antenna characteristics and increase the communication distance.

  By adopting the above-described configuration, the present invention has the following effects. That is, the antenna device of the present invention can communicate in at least three communication frequency bands, for example, 13.56 MHz band, 800 MHz to 1000 MHz band, and 2400 MHz to 2500 MHz band, and each communication frequency band in the same plane. By arranging the loop-shaped antenna elements having a circular shape corresponding to the above in a concentric manner, particularly when the RFID reader / writer and the data carrier are close to each other and the distance between them is short, Communication in at least three communication frequency bands can be an electromagnetic induction system, and a loop-shaped antenna element capable of communication in the 13.56 MHz band among the at least three communication frequency bands, that is, a first loop antenna By arranging a loop-shaped magnetic body in the vicinity of the lower part of the element, the first loop Even if the strength of the magnetic field generated by the antenna element is increased and there is metal around it, it is possible to suppress the deterioration of the antenna characteristics, and at the same time, it is possible to reduce the size and cost. is there.

The figure which shows the structure of the antenna apparatus which concerns on the Example of this invention. 1A is a top view and FIG. 1B is a side view.

  Hereinafter, embodiments of the present invention will be described in detail.

  The antenna device of the present invention is used for an RFID reading / writing device capable of wirelessly communicating with a data carrier, that is, a contactless IC card having at least an IC chip and a looped transmitting / receiving antenna. . The antenna device can communicate with the contactless IC card in three different communication frequency bands, that is, a 13.56 MHz band, an 800 MHz to 1000 MHz band, and a 2400 MHz to 2500 MHz band.

  The antenna device includes three loop-shaped antenna elements corresponding to the three communication frequency bands, each of which is shorter than a quarter of a wavelength corresponding to each frequency. Have

  The three loop antenna elements, ie, a first loop antenna element that communicates at a frequency of 13.56 MHz band, a second loop antenna element that communicates at a frequency of 800 MHz to 1000 MHz band, and a frequency of 2400 MHz to 2500 MHz band. For example, when each of the three loop antenna elements is formed in a circular shape, the third loop antenna element for communication is concentrically formed from the inner side to the outer side in the above order, and is insulated with glass epoxy or the like. On the front surface of the substrate, they are arranged and fixed separately from each other.

  The first loop antenna element, the second loop antenna element, and the third loop antenna element are formed by circularly forming a copper film by etching or the like on the front surface of the insulating substrate such as glass epoxy. What was formed in a loop shape, copper foil having adhesiveness on the back surface was processed into a circular loop shape, and was pasted on the front surface of the insulating substrate such as glass epoxy, or insulation coated copper The wire may be processed into a circular loop shape and bonded or fixed to the front surface of the insulating substrate such as glass epoxy via an adhesive or the like.

  In addition, a loop-shaped magnetic body processed according to the shape of the first loop antenna element is provided directly or near the lower portion of the first loop antenna element provided on the front surface of the insulating substrate. It is better to arrange them apart.

  For example, when the first loop antenna element has a circular shape, the loop-shaped magnetic body has a band width and a certain thickness that can sufficiently cover the projected area of the first loop antenna element. , Circular loop-shaped magnetic body made of a sheet-like body in which magnetic powder is dispersed and solidified in a binder, or a circular loop-shaped magnetic body made of a ceramic material such as soft magnetic ferrite or a metal material such as an iron alloy It is better to use the body. In particular, a circular loop-shaped magnetic body made of the sheet-like body is flexible, lightweight, and easy to process. Therefore, the workability when fixing to the insulating substrate is good.

  Further, each of the input / output terminals of the three loop antenna elements may be provided so as to be aligned with one end face of the insulating substrate, or may be led out to the back surface of the insulating substrate through a through hole or the like. You may make it provide.

  An embodiment of the antenna device of the present invention will be described below with reference to FIG.

  FIG. 1 is a diagram illustrating a configuration of an antenna device according to an embodiment of the present invention. 1A is a top view and FIG. 1B is a side view.

  The antenna device 100 of the present invention includes a data carrier, that is, a non-contact IC card, three communication frequency bands, that is, a communication frequency of 13.56 MHz using an electromagnetic induction method, a communication frequency of 800 MHz to 1000 MHz using a radio wave method and an electromagnetic induction method, In the present embodiment, the actual frequencies used for communication are set to 13.56 MHz, 953 MHz, and 2450 MHz, respectively, in the communication frequency range of 2400 MHz to 2500 MHz using the radio wave system and electromagnetic induction system. .

  However, here, although the communication method for communication at the communication frequency of 953 MHz and the communication frequency of 2450 MHz is the radio wave method and the electromagnetic induction method, the communication frequency of 953 MHz and the communication frequency of 2450 MHz using the antenna device 100 of the present invention is used. However, the communication method is not limited to so-called radio wave communication, and the communication method varies depending on the actual communication distance when the user carrying the non-contact IC card accesses the RFID reader / writer. Is. Specifically, when the non-contact IC card is relatively far away from the RFID reading / writing device and the distance between the two is long, for example, in the case of several meters, communication is performed by a radio wave system, and the RFID reading / When the writing device and the non-contact IC card are close to each other and the distance between them is short, for example, several centimeters to several tens of centimeters, communication is performed by electromagnetic induction.

  In general, electromagnetic waves exhibit different properties in the near field and the far field. In other words, the electromagnetic wave propagating while the electric and magnetic fields orthogonal to each other vibrate are dominated by the magnetic field component in the near field, and conversely, the electric field component is dominant in the far field, or the electric field component and the magnetic field component are equal. Present in quantity. That is, the electromagnetic wave can be communicated in the near field by the electromagnetic induction method and in the far field by the radio wave method by using a loop-shaped antenna element as exemplified in this embodiment.

  As shown in FIGS. 1A and 1B, the antenna device 100 of the present invention includes at least three insulating substrates 107 and three loop-shaped elements arranged on the front surface of the insulating substrate 107. It consists of an antenna element. The insulating substrate 107 is a glass epoxy substrate having a length of 50 mm, a width of 50 mm, and a thickness of 0.8 mm. The three loop antenna elements, that is, a first loop antenna element 101 communicating at a frequency of 13.56 MHz, a second loop antenna element 102 communicating at a frequency of 953 MHz, and a third loop antenna element communicating at a frequency of 2450 MHz Each of 103 is formed on the front surface of the insulating substrate 107 by etching so that a strip-shaped copper film having a certain width becomes a square shape.

  Each of the square second loop antenna element 102 and the square third loop antenna element 103 has a number of turns of one turn, and only the square first loop antenna element 101 is 2 It is assumed to have the number of turns of the turn.

  In actual design, especially when communicating by an electromagnetic induction method with a frequency of 13.56 MHz, if the number of turns is small, the reception sensitivity may be lowered. Therefore, the strip-shaped copper constituting the first loop antenna element 101 is used. The number of turns is increased by increasing the total length of the membrane.

  However, the portion overlapped by the winding is insulated so as to be connected to the band-shaped bridge copper film 112 formed by etching on the back surface of the insulating substrate 107 through the through holes 108a and 108b formed in the insulating substrate 107. Secured.

  When the RFID reading / writing device and the data carrier, that is, the non-contact IC card are close to each other and the communication distance between them is short, each antenna element constituting the antenna device 100 has a loop shape as described above. Thus, a magnetic field is generated by electromagnetic induction, and an induced current can be induced and fed to the conductors constituting the transmitting and receiving antennas of the non-contact IC card that are present relative to each other, thereby enabling communication between the two It becomes.

  The total length of the strip-shaped copper film formed by etching constituting the first loop antenna element 101 is 340 mm, the total length of the strip-shaped copper film formed by etching constituting the second loop antenna element 102 is 68 mm, The total length of the strip-shaped copper film formed by etching and constituting the third loop antenna element 103 is 24 mm. The length of a quarter of the wavelength corresponding to the frequency 13.56 MHz communicated with the first loop antenna element 101 is about 5530 mm, and the length of 4 corresponding to the frequency 953 MHz with which the second loop antenna element 102 communicates. The length of a quarter is about 78.7 mm, and the length of a quarter of the wavelength corresponding to the frequency 2450 MHz at which the third loop antenna element 103 communicates is 30.6 mm. Each of the overall lengths of the antenna elements is configured to be shorter than a quarter length of the wavelength corresponding to each of the communication frequencies.

  Each of the total lengths of the three loop-shaped antenna elements is configured to be shorter than a quarter of the wavelength. This is because the total length of any of the three loop-shaped antenna elements is equal to the quarter of the wavelength. If the length is longer than 1, the direction of the current flowing through the elongated antenna element is reversed, and the direction of the current flowing through the three loop-shaped antenna elements is not uniform, so that the generated magnetic fields cancel each other. As a result, it is not possible to generate a magnetic field having a sufficiently large size for communication.

  In addition, although the site | part which concerns on transmission / reception of communication by an electromagnetic induction system is described with the 1st loop antenna element 101, the 2nd loop antenna element 102, and the 3rd loop antenna element 103, strictly speaking, “ It should be written not as an “antenna” but as a “loop conductor” or a one-turn or two-turn “coil” involved in electromagnetic induction. However, here, for the sake of convenience, the first loop antenna element 101, the second loop antenna element 102, and the third loop antenna element 103 are represented as described above.

  The three loop antenna elements are arranged concentrically on the front surface of the insulating substrate 107. That is, a square-shaped third loop antenna element 103 is arranged at the center on the front surface of the insulating substrate 107, and on the outer side thereof, spaced apart from the square-shaped third loop antenna element 103, A second loop antenna element 102 having a shape is disposed, and further, the first antenna element 101 having a square shape is disposed on the outer side of the second loop antenna element 102 so as to be concentric. It comprised so that it might become a shape.

  Each of the input / output terminals 104a, 104b, 105a, 105b, 106a, 106b of the three loop antenna elements is provided so as to be arranged on one end face of the insulating substrate 107, but the second loop Each of the input / output terminals 105a and 105b of the antenna element 102 and the input / output terminals 106a and 106b of the third loop antenna element 103 is one end of a strip-shaped copper film constituting the second loop antenna element 102 and the other. An end, and one end and the other end of the strip-shaped copper film constituting the third loop antenna element 103, and one end and the other end of the strip-shaped copper film are formed on the insulating substrate 107. Etched on the back surface of the insulating substrate 107 connected through each of the through holes 109a, 109b, 110a, 110b. Strip drawer copper film 113a has, 113b, 114a, and the respective ends of 114b.

  Further, the loop-shaped magnetic body 111 is disposed near the lower portion of the rectangular first loop antenna element 101 disposed on the outermost side of the concentric shape, that is, on the opposite side of the detection surface of the antenna device 100. Specifically, an adhesive was directly applied and fixed to the back surface of the insulating substrate 107 corresponding to the portion where the first loop antenna element 101 was disposed. In addition, as the loop-shaped magnetic body 111, Basterade (registered trademark) manufactured by NEC TOKIN Corporation made of a sheet-like body processed into a square shape having an outer shape of 50 mm × 50 mm, a band width of 10 mm, and a thickness of 0.25 mm. It was used.

  Further, in order to confirm the effect of suppressing the deterioration of antenna characteristics by the loop-shaped magnetic body 111, a square-shaped Busterade (registered trademark) facing the detection surface of the antenna device 100 is formed on the back surface of the insulating substrate 107. When not arranged, the strength of the magnetic field generated by the first loop antenna element 101 (hereinafter referred to as the first loop antenna element without magnetic material) and the B-shaped Bastadeido (registered trademark) are The intensity of the magnetic field generated by the first loop antenna element 101 (hereinafter referred to as the first loop antenna element with a square-shaped magnetic body) when arranged on the back surface was measured and compared. However, each antenna device 100 is arranged with its detection surface facing upward, and is placed on a table with a metal plate (not shown) laid on the lower portion of the antenna device 100.

  As a result, the strength of the magnetic field generated by the first loop antenna element having the square-shaped magnetic body toward the detection surface of the antenna device 100 is the magnetic field generated by the first loop antenna element without the square-shaped magnetic body. It was 1.4 times the strength of the antenna, and the effect of suppressing the deterioration of the antenna characteristics was confirmed. At the same time, a current during communication is passed through each of the second loop antenna element 102 and the third loop antenna element 103 provided on the front surface of the insulating substrate 107 to generate a magnetic field. Although the strength of each magnetic field was confirmed, the strength of the magnetic field did not decrease in both cases, and both had no problem in communication.

  Furthermore, Buster Raid (registered trademark) having the same shape as that of the insulating substrate 107 and having a length of 50 mm, a width of 50 mm, and a thickness of 0.25 mm is fixed to the back surface of the insulating substrate 107 with an adhesive. The strength of the magnetic field generated by the first loop antenna element 101 (hereinafter referred to as the first loop antenna element with a full magnetic body) in the case of covering the entire surface of was measured.

  In addition, a current during communication is passed through each of the second loop antenna element 102 and the third loop antenna element 103 provided on the front surface of the insulating substrate 107 to generate a magnetic field. The strength of each magnetic field was confirmed.

  As a result, the strength of the magnetic field generated by the first loop antenna element with the magnetic material toward the detection surface of the antenna device 100 is the strength of the magnetic field generated by the first loop antenna element without the magnetic material. Compared to 1.5 times. On the other hand, the strength of the magnetic field generated by the second loop antenna element 102 and the third loop antenna element 103 provided on the front surface of the insulating substrate 107 is determined by the square-shaped buster raid ( Unlike the case of using (registered trademark), the strength of the magnetic field was reduced in both cases, and both could not communicate well.

  From these results, it was confirmed that the characteristics of the antenna device 100 as a whole were better when the loop-shaped magnetic body 111 was used than when the magnetic body covering the entire surface was used.

  By adopting such a configuration, it is possible to reduce the size and cost, and the loop-shaped magnetic body such as the above-mentioned B-shaped Busterade (registered trademark) is used as the first antenna element. Since the magnetic energy can be converged on the loop-shaped magnetic body by arranging it near the lower part of the metal, even if there is a metal or the like in the vicinity, the rate at which the magnetic field reaches the metal or the like is reduced. As a result, the loss of magnetic energy can be reduced. As a result, the loop-shaped magnetic body functioning as a magnetic yoke can increase the strength of the magnetic field toward the detection surface of the antenna device, and the communication by the second antenna element, and the third The deterioration of the antenna characteristics of the first antenna element can be suppressed without affecting the communication by the antenna element.

  The above-described embodiment has been described on the assumption that a user carrying a data carrier, that is, a non-contact IC card, accesses an antenna device of a fixed RFID reader / writer. Separately, an RFID reading / writing device having the antenna device of the present invention is applied to a fixed data carrier, for example, an IC tag attached to and fixed to an article such as a product arranged in a product shelf. The antenna device of the present invention can be used even when a user carrying an electronic communication device with a built-in mobile phone such as a mobile phone accesses.

  Further, in the above-described embodiment, the antenna device of the present invention is exemplified by three loop-shaped antenna elements arranged in the same plane so as to be concentric, with a rectangular shape. However, the present invention is not limited thereto, and loop-shaped antenna elements having a circular shape are concentric, loop-shaped antenna elements having a substantially rectangular shape are concentric and substantially rectangular, and a loop-shaped antenna having an arbitrary multi-shape is formed. The antenna elements may be configured by concentric polygonal shapes, or loop-shaped antenna elements having any substantially polymorphic shape, arranged concentrically and substantially in the same plane, or loop-shaped antennas having different shapes. It may be arranged and arranged in the same plane in a state where elements are mixed.

  Note that the loop-shaped magnetic body has a circular shape, a substantially rectangular shape, an arbitrary polygonal shape, or an arbitrary substantially polygonal shape other than the rectangular shape as illustrated in accordance with the shape of the loop-shaped antenna element. It may be a thing.

  The antenna device of the present invention can communicate in at least three communication frequency bands, for example, 13.56 MHz band, 800 MHz to 1000 MHz band, and 2400 MHz to 2500 MHz band, and each communication frequency band in the same plane. By arranging the loop-shaped antenna elements having a corresponding rectangular shape in a concentric rectangular shape, particularly when the RFID reader / writer and the data carrier are close to each other and the distance between the two is short, Communication in at least three communication frequency bands can be an electromagnetic induction system, and a loop-shaped antenna element capable of communication in the 13.56 MHz band among the at least three communication frequency bands, that is, a first loop antenna By arranging a loop-shaped magnetic body near the lower part of the element, the first loop amplifier It is possible to increase the strength of the magnetic field generated by the N element and suppress the deterioration of the antenna characteristics even when there are metals around it, and at the same time, it is possible to reduce the size and cost. is there.

  The embodiments of the present invention have been described above using the embodiments. However, the present invention is not limited to the embodiments, and the present invention is not limited to the scope of the present invention. Included in the invention. That is, it goes without saying that the present invention also includes various variations and modifications that would be obvious to those skilled in the art.

  The antenna device of the present invention can be used in a communication technical field related to an RFID system using an RFID reading / writing device that performs non-contact communication with a data carrier by electromagnetic induction or radio waves. The present invention can be used in a communication technology field related to an RFID system that performs communication using different communication frequency bands or a plurality of different communication methods.

100 antenna device 101 first loop antenna element 102 second loop antenna element 103 third loop antenna element 104a, 104b, 105a, 105b, 106a, 106b input / output terminal 107 insulating substrate 108a, 108b, 109a, 109b, 110a 110b Through hole 111 Loop-shaped magnetic body 112 Bridge copper film 113a, 113b, 114a, 114b Draw copper film

Claims (1)

An antenna device for use in an RFID reader / writer that communicates without contact with a data carrier,
The antenna device is
A first antenna element that communicates at a first frequency of at least 13.56 MHz and includes a loop conductor and is connected to each input / output terminal ;
A second antenna element including a loop conductor and connected to each input / output terminal, which communicates at a second frequency of 800 MHz to 1000 MHz;
Communicating a third frequency of 2400MHz to 2500MHz band, and a third antenna element connected to each input terminal comprises a loop conductor,
The length of the loop conductor of the first antenna element is shorter than the first length of 4 minutes of the first wavelength corresponding to the frequency, and the length of the loop conductor of the second antenna element, the first less than 1 in a length of quarter of the wavelength corresponding to the second frequency, and the length of the loop conductor of the third antenna element is shorter than the first length of 4 minutes of the third wavelength corresponding to the frequency And
Each of the loop conductor of the first antenna element, the loop conductor of the second antenna element, and the loop conductor of the third antenna element is in the same plane and is concentric, concentric, or substantially concentric. Arranged to be either rectangular, concentric polygonal, or concentric polygonal,
An antenna device comprising a loop-shaped magnetic body in the vicinity of the lower portion of the first antenna element.

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