JP2005151257A - Two-frequency communication system in rfid communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a two-frequency communication system in RFID communication, which can automatically recognize two carrier frequencies to switch and use the frequencies, and establishes compatibility between a plurality of carrier frequencies. <P>SOLUTION: In a front end of an RFID chip, two sets of antenna tuning circuits, i.e. an antenna tuning circuit for 950 MHz and an antenna tuning circuit for 13.56 MHz are connected, a detection rectification circuit for envelope detection and power supply, a voltage detecting circuit and a frequency dividing circuit for dividing a frequency to value of near 13.56 MHz are provided on the poststage of the antenna tuning circuit for 950 MHz, and a detection rectification circuit for envelope detection and power supply and a voltage detecting circuit are provided on the poststage of the antenna tuning circuit for 13.56 MHz. Moreover, a clock generating circuit for generating a system clock, a modulating circuit for applying load modulation to each of the antenna tuning circuits, and a switching element and the like are provided to constitute the apparatus. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention automatically uses two carrier frequencies in RFID (Radio Frequency Identification) communication for data transmission between a reader called interrogator and a transponder called transponder in a contactless IC card or wireless ID tag system. The present invention relates to a two-frequency communication method in RFID communication that can be recognized and used.

  In recent years, automatic recognition by individual ID identification has been widely used in many fields such as service industry, manufacturing industry, distribution industry, sales industry, and logistics. As a means for identifying the ID, a barcode system in which the content of a barcode label attached to an individual is read by a barcode reader to perform information processing has been common. Although the bar code system can be constructed at a low cost, there are disadvantages in that the information storage capacity is low and the information cannot be rewritten. For this reason, an IC card provided with a memory of a silicon chip as an information storage medium is used in various fields such as an IC card for public telephones, a credit card, and a fuel card.

  The IC card has a disadvantage that it is inferior in practicality because it requires mechanical contact between the signal terminals when performing data transmission with the interrogator. For this reason, a non-contact method in which data transmission is RFID communication using magnetic field or electromagnetic field inductive coupling has been attracting attention and is becoming popular. The non-contact method includes a contact type (international standard is ISO / IEC10536) with a communication distance of several millimeters, a proximity type (international standard is ISO / IEC14443), and a proximity of about 50 cm to 1 m. There is a type (the international standard is ISO / IEC15693). The carrier frequency is generally 4.915 MHz for the contact type and 13.56 MHz for the proximity type and the proximity type. The communication distance is a guideline and is not defined in the standard document, but is defined by the magnetic field strength.

  In the RFID communication, in the case of an application that requires a communication distance, a proximity type is used. The theoretical limit distance of near-field RFID communication using a carrier frequency of 13.56 MHz is 3.5 m, but the magnetic field strength from the interrogator that can be recognized by the responder is inversely proportional to the cube of the distance in the near field. The actual communication distance is less than the theoretical value. As a remote type, in the wireless ID tag system in the US distribution field, 915 MHz is widely used as a carrier frequency, and a communication distance of 5 m or more is put into practical use. Also in Japan, in order to keep pace with the spread in the US distribution field, legalization is progressing in the direction that the use of carrier frequencies in the 860 MHz to 960 MHz band is approved by the end of 2004, and 950 MHz is promising.

In the United States, an RFID chip capable of supporting two frequencies of 915 MHz and 2.45 GHz carrier frequency has begun to be used. This is because one RFID chip corresponds to an application using carrier frequencies of 915 MHz and 2.45 GHz.
RFID handbook, written by Klaus Finkenzeller, translated by Institute of Software Engineering, published by Nikkan Kogyo Shimbun

  In the far-field RFID communication using the carrier frequency of 915 MHz, the communication distance is 5 m or more, and the same communication distance is available even at 2.45 GHz, which is useful for applications that require a communication distance. However, although the straightness of the electromagnetic field improves as the carrier frequency becomes higher, the reflection or absorption of the electromagnetic field becomes significant depending on the material and size of the individual, and there is a problem that it cannot be used depending on the object. there were. In addition, 950 MHz, which is expected to be widely used, will be approved in the future, and the 13.56 MHz compatible system currently used in the neighborhood type will continue to be used. A vessel is required. In addition, by selecting and using only one of the two frequencies according to the usage conditions and environmental conditions, or by automatically switching between two frequencies, the data reliability can be improved, and applications with different communication distances and transmission characteristics. It becomes possible to make it correspond.

  The present invention has been made in order to solve the above problems and necessity, and 950 MHz and 13 are used as carrier frequencies of RFID communication between an interrogator and a responder in a non-contact IC card or a wireless ID tag system. An object of the present invention is to provide a two-frequency communication method in RFID communication that can correspond to two frequencies of .56 MHz. Since 950 MHz is promising as a carrier frequency to be approved in the future, it is mainly described in the present specification. However, it covers the frequency range of 860 MHz to 960 MHz band depending on the contents of legalization.

  In order to solve the above-described problem, in the two-frequency communication system for RFID communication according to the present invention, the antenna / tuning circuit compatible with 950 MHz and the antenna / tuning circuit compatible with 13.56 MHz are supported at the front end of the RFID chip. Two sets of antennas and tuning circuits are connected, and the detection and rectification circuit for detecting the envelope of the modulated wave and supplying the power for driving the RFID chip and the power-on voltage are detected after the antenna and tuning circuit for 950 MHz. A voltage detection circuit and a frequency dividing circuit for dividing the frequency of 950 MHz to near 13.56 MHz are provided, and the succeeding stage of the 13.56 MHz compatible antenna / tuning circuit is for detecting the envelope of the modulated wave and supplying power for driving the RFID chip. And a voltage detection circuit for detecting the power-on voltage. Furthermore, a clock generation circuit for generating a system clock of the RFID chip, a modulation circuit for performing load modulation on each antenna / tuning circuit, a switching element, and the like are provided.

  If the two-frequency communication method in the RFID communication of the present invention is adopted as the front end portion of the RFID chip, the carrier frequency of the RFID communication between the interrogator and the responder in the non-contact IC card or the wireless ID tag system is 950 MHz and 13. It can support two frequencies of 56 MHz, and uses the advantages of each carrier frequency, that is, the straightness of 950 MHz and the communication distance and the transmission of 13.56 MHz, etc., and only one of the two frequencies depending on the use conditions and environmental conditions. In applications where selection is used or security is emphasized, the reliability of data can be improved by automatically recognizing and switching the data transmission of each of the two frequencies. In addition, there is an effect that it is possible to correspond to an application that takes advantage of the difference in communication distance and transmission characteristics.

  The best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a circuit block diagram for realizing a two-frequency communication system in RFID communication according to the present invention.

  At the front end of the RFID chip, two sets of antenna / tuning circuit 1 for 950 MHz and antenna / tuning circuit 1 for 13.56 MHz and antenna / tuning circuit 5 for 13.56 MHz are connected. The antenna is different in shape and size depending on the carrier frequency to be used, and in the case of a loop antenna, the number of turns is also different.

  Further, the antenna / tuning circuit 1 for 950 MHz is followed by a detection / rectification circuit 2 for detecting the envelope of the modulated wave and supplying power for driving the RFID chip, and a voltage detection circuit 4 for detecting the power-on voltage and 950 MHz. A frequency dividing circuit 3 for dividing the frequency to 13.56 MHz is provided, and a detection circuit for detecting the envelope of the modulated wave and supplying power for driving the RFID chip is provided at the subsequent stage of the antenna and tuning circuit 5 compatible with 13.56 MHz. A rectifier circuit 6 and a voltage detection circuit 7 for detecting the power-on voltage are provided. The detector / rectifier circuits 2 and 6 are composed of a single-wave or full-wave or voltage doubler rectifier circuit and a smoothing capacitor, etc., using a short-circuit barrier diode with a low forward voltage drop for an AC voltage of the carrier frequency. The voltage detection circuits 4 and 7 are configured by a voltage dividing circuit, a comparator, and the like in order to input a reset signal to the RFID chip to which the operating voltage is supplied.

  Furthermore, a clock generation circuit 14 for generating a system clock of the RFID chip, a modulation circuit 8 for load-modulating each antenna / tuning circuit 1, 5, switching elements 10, 12, and the like are provided. The modulation circuit 8 is not particularly limited, but according to the asynchronous communication method using the pulse gap signal described in Japanese Patent Application No. 2003-384604 by the applicant of the present application, it can be used in a system of any carrier frequency. More preferred. Further, the switching elements 10 and 12 are preferably FETs.

  Embodiments of the present invention will be described with reference to the drawings. First, FIG. 2 is a configuration block diagram for explaining the communication principle in RFID communication. The principle of RFID communication for performing data transmission between an interrogator and a responder in a non-contact IC card or a wireless ID tag system will be described.

  The interrogator 16 and the responder 20 in the non-contact IC card or the wireless ID tag system perform data transmission by inductive coupling at a frequency lower than the microwave. Here, the responder 20 receives power supply from the interrogator 16 as a passive element and operates the RFID chip 21. In this figure, when the magnetic field or electromagnetic field 24 output from the antenna 19 connected to the interrogator 16 penetrates the loop of the antenna 23 connected to the responder 20, an electromotive force is generated in the antenna 23 by mutual induction. At this time, a tuning capacitor 18 is connected in parallel to the antenna 19 of the interrogator 16 to constitute a resonance circuit having a resonance frequency that matches the carrier frequency output from the oscillator 17. In addition, a tuning capacitor 22 is connected in parallel to the antenna 23 of the responder 20, and a resonance circuit adjusted to resonate with the carrier frequency output from the interrogator 16 is configured. Communication and power supply are performed. That is, it is considered that the inductive coupling by the interrogator 16 and the responder 20 constitutes a transformer through a space.

  Next, FIG. 1 is a circuit block diagram for realizing the two-frequency communication method in the RFID communication according to the present invention. The two-frequency communication of the RFID communication using the carrier frequency of 950 MHz and the RFID communication using the carrier frequency of 13.56 MHz. The method will be described.

  Similar to the antenna 23 and the tuning capacitor 22 in FIG. 2, at the front end portion of the RFID chip 21, two sets of antennas / tuning circuits corresponding to the antenna / tuning circuit 1 compatible with 950 MHz and the antenna / tuning circuit 5 compatible with 13.56 MHz are used. Connect. The antenna differs in shape and size depending on the carrier frequency used, and in the case of a loop antenna, the number of turns also differs. In the case of a loop antenna, since it is often configured by a printed pattern of copper foil or aluminum foil, it is generally connected outside the RFID chip 21.

  Next, a detection / rectification circuit 2 for detecting the envelope of the modulated wave and supplying power for driving the RFID chip, and a voltage detection circuit 4 for detecting the power-on voltage are provided at the subsequent stage of the antenna / tuning circuit 1 for 950 MHz. A frequency dividing circuit 3 for dividing the frequency of 950 MHz to near 13.56 MHz is provided, and a detection circuit for detecting the envelope of the modulated wave and supplying power for driving the RFID chip is provided at the subsequent stage of the antenna / tuning circuit 5 compatible with 13.56 MHz. A rectifier circuit 6 and a voltage detection circuit 7 for detecting the power-on voltage are provided. When the carrier frequency is 950 MHz, the frequency dividing circuit 3 is 13.57 MHz by dividing 1/70 (in the case of 915 MHz, 13.46 MHz by dividing 1/68), and the other carrier The frequency is almost equal to 13.56 MHz which is a frequency, and each circuit block in the RFID chip can be shared. The detector / rectifier circuits 2 and 6 are composed of a single-wave or full-wave or voltage doubler rectifier circuit and a smoothing capacitor using a short-circuit barrier diode or the like with a low forward voltage drop of the carrier voltage AC voltage. When an electrically rewritable memory is built in the RFID chip, a booster circuit (not shown) for generating a higher voltage is built in. The voltage detection circuits 4 and 7 are configured by a voltage dividing circuit, a comparator, and the like in order to input a reset signal to the RFID chip to which the operating voltage is supplied. Since the power supply of the RFID chip is derived from induced electromotive force and is unstable, the relationship between the operating voltage and the reset voltage is important. In FIG. 1, the reset signal is output to the subsequent logic circuit via the gate 15 in order to support two frequencies.

  Next, the clock generation circuit 14 for generating the system clock of the RFID chip, the modulation circuit 8 for load-modulating the antenna / tuning circuits 1 and 5, the switching elements 10 and 12, and the like are provided. In FIG. 1, in order to correspond to two frequencies, a frequency obtained by dividing 950 MHz by 1/70 and 13.56 MHz are input to the clock generation circuit 14 through the gate 13, and the system clock is obtained by dividing the frequency by 1/192. In addition, the modulation circuit 8 performs ASK modulation with subcarriers and supports two frequencies. Therefore, the frequency obtained by dividing 1/70 of 950 MHz by 1/32 and the output of the modulation circuit 8 are output to the gate 9. Is input to the switching element 10 through the 950 MHz, and the load modulation of the antenna / tuning circuit 1 corresponding to 950 MHz is performed, and the frequency obtained by dividing 13.56 MHz by 1/32 and the output of the modulation circuit 8 through the gate 11 are switched. To perform load modulation of the antenna / tuning circuit 5 compatible with 13.56 MHz. With the configuration described above, two-frequency communication in RFID communication is possible.

  As an application mode of 2 frequencies, the oscillator 17 on the interrogator 16 side is compatible with 2 frequencies of 950 MHz and 13.56 MHz, and only one of the 2 frequencies can be selected and used depending on use conditions and environmental conditions, or an application that emphasizes security In, the data transmission at two frequencies of 950 MHz and 13.56 MHz may be automatically recognized and switched for use, and the data reliability may be improved by transmitting data at different frequencies. Moreover, if it is applied to an application that makes use of 950 MHz straightness and communication distance and 13.56 MHz transparency, the range of use will be expanded.

  In the above description, two frequencies of 950 MHz and 13.56 MHz have been described. However, other frequencies used in RFID communication, for example, a combination of two frequencies of 125 KHz and 13.56 MHz may be arbitrarily used. . In addition, if it corresponds to the asynchronous communication system by the pulse gap signal described in Japanese Patent Application No. 2003-384604 by the applicant of the present application, data transmission from the responder (20) corresponds to the pulse gap signal and a plurality of carrier frequencies. By adopting an asynchronous communication system composed of compatible logic circuits, an arbitrary carrier frequency can be used in the system by remote operation.

It is a circuit block diagram for implement | achieving the 2 frequency communication system in RFID communication of this invention. It is a block diagram for explaining a communication principle in RFID communication.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna and tuning circuit 2 Detection and rectification circuit 3 Frequency division circuit 4 Voltage detection circuit 5 Antenna and tuning circuit 6 Detection and rectification circuit 7 Voltage detection circuit 8 Modulation circuit 9 Gate 10 Switching element 11 Gate 12 Switching element 13 Gate 14 Clock generation Circuit 15 Gate 16 Interrogator 17 Oscillator 18 Tuning Capacitor 19 Antenna 20 Responder 21 RFID Chip 22 Tuning Capacitor 23 Antenna 24 Magnetic Field or Electromagnetic Field

Claims (3)

At the front end portion of the RFID chip (21), two sets of antenna / tuning circuits corresponding to two frequencies of the antenna / tuning circuit (1) compatible with 950 MHz and the antenna / tuning circuit (5) compatible with 13.56 MHz are connected to each other at 950 MHz. Following the corresponding antenna / tuning circuit (1) is a detection / rectification circuit (2) for detecting the envelope of the modulated wave and generating power for driving the RFID chip, and a voltage detection circuit (4) for detecting the power-on voltage. ) And a frequency dividing circuit (3) for dividing the frequency of 950 MHz to 13.56 MHz, and the antenna and tuning circuit (5) compatible with 13.56 MHz are used for detecting the envelope of the modulated wave and driving the RFID chip. A detection / rectification circuit (6) for generating power and a voltage detection circuit (7) for detecting the power-on voltage are provided.
Further, a clock generation circuit (14) for generating a system clock of the RFID chip (21), a modulation circuit (8) for load modulating each antenna / tuning circuit (1, 5), and a switching element (10, 12) A two-frequency communication system in RFID communication, characterized in that it is provided with a configuration.   The oscillator (17) on the interrogator (16) side is compatible with two frequencies of 950 MHz and 13.56 MHz, and only one of the two frequencies is selected and used depending on the use conditions and environmental conditions, or 2 for applications that place importance on security. 2. The two-frequency communication system in RFID communication according to claim 1, wherein data reliability can be improved by automatically recognizing and switching data transmission of each frequency.   Data transmission from the responder (20) is an asynchronous communication system composed of a pulse gap signal and a logic circuit having compatibility so as to be compatible with a plurality of carrier frequencies. 3. The two-frequency communication system in RFID communication according to claim 1, wherein the two-frequency communication system can be used in a system.

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