JP5317341B2 - RFID reader / writer system - Google Patents

Description

  The present invention relates to an RFID (Radio Frequency IDentification) reader / writer system for reading or writing an IC tag.

  An RFID reader / writer that reads or writes an IC tag is connected to an antenna for performing wireless communication, and can communicate with the IC tag using radio waves transmitted from the antenna. An RFID reader / writer system in which an RFID reader / writer is incorporated in a gate of a warehouse or the like is used for entering / exiting a person who has an IC tag, managing loading / unloading of luggage, and the like.

  In recent RFID reader / writer systems, the UHF (Ultra High Frequency) band is frequently used as the frequency band of radio waves because of the long communication distance. On the other hand, since the communicable distance becomes longer, there is a problem of communication interference due to unnecessary radio waves from a distant RFID reader / writer.

  As a method of avoiding communication interference with other RFID reader / writers, the carrier of the channel to be used (discrete frequency band set in advance so that it can be used) is searched before starting communication, and the interference level among them is the highest. It has been proposed to select and use a low channel, to reduce the transmission level of the interfering RFID reader / writer, or to change the polarization direction of the radio wave.

  Patent Document 1 is a reader / writer device that has communication means with variable transmission speed, and reads / writes RFID via the communication means, and the communication means includes a carrier sense unit for detecting a carrier, The electric field strength detected by the carrier sense unit is compared with a level determined according to communication conditions, and an electric field level determination unit that determines whether or not the level is equal to or lower than the level. A reader / writer device is disclosed that includes a communication condition setting unit that sets a higher transmission rate when it is determined that the level is exceeded when determined.

  In Patent Document 2, even when a plurality of reader / writers for communicating with an RFID tag are arranged in close proximity to each other, communication failure caused by radio wave interference between the reader / writers is disclosed. As a means to enable the generation to be suppressed while ensuring good communication quality, the system controller sequentially commands multiple reader / writers to transmit test signals with default output levels consisting of unmodulated signals. However, when the test signal is transmitted from the reader / writer, the reception level of the test signal measured by another reader / writer is collected, and some of the collected reception levels exceed the preset non-interference level. In this case, the transmission level of the reader / writer that is the transmission source of the test signal is set between the reader / writer and the RFID tag that has entered the communication area. Wireless communication system that reduces does not fall below a minimum transmission level necessary for communication is disclosed in.

  Patent Document 3 includes a reader / writer having a reader / writer main body and a polarization-switchable antenna, a reader / writer that transmits a continuous carrier wave, and a tag that modulates the continuous carrier wave with tag information and returns a response signal to the reader / writer. The reader / writer main unit determines a level of the received interference signal, determines a channel and a polarization direction in which the level of the interference signal is equal to or less than a threshold, and determines the determined channel and polarization An RFID system is disclosed that receives a response signal from the tag in a direction.

JP 2008-228091 A JP 2007-124321 A International Publication No. 2006/082612

  The RFID air protocol is standardized by ISO or EPCglobal, which is a standardization organization, and in particular, detailed specifications of UHF band RFID are determined by EPCglobal (Class-1 Generation-2). In the standardization specification of EPCglobal, other RFID reader / writers are adopted by adopting an encoding method in which the carrier frequency of the reply from the IC tag is different from the frequency of transmission from the RFID reader / writer even at the same frequency (channel). A communication method for reducing interference in the same channel from the network is defined.

  Among the UHF band RFID air protocols, the FM0 method and the mirror subcarrier method (hereinafter referred to as “MS method”) are used as the encoding method of the signal returned from the IC tag.

  FIG. 4 is a schematic diagram for explaining an RFID encoding method, and shows (a) FM0 method and (b) MS method encoding.

  FIG. 5 is a schematic diagram showing an example of a spectrum waveform in the RFID encoding method. In the figure, (1) is a transmission wave from the RFID reader / writer, (2) is a reception wave returned from the IC tag, and (3) is a spectrum of an interference wave from another RFID reader / writer. Among the received waves of (2), (a) is a spectrum at the time of transmission by the FM0 system.

  The transmission wave from the RFID reader / writer and the return wave from the IC tag have the same frequency. In this case, if there is an interference wave from another RFID reader / writer in the same channel, the interference wave often has a signal level much higher than the return wave from the IC tag, and the return wave of the IC tag by the RFID reader / writer. May be difficult to recognize.

  (B) of FIG. 5 (2) is a spectrum in the case of the MS system. The transmission carrier is modulated with a link frequency (hereinafter referred to as “LF”), and the subcarrier of the return wave is shifted from the transmission wave by LF. This suppresses interference with the transmission wave of another RFID reader / writer.

  As an example, when LF is set to an intermediate value of a channel, the frequency is not used for transmission from the RFID reader / writer, so that interference with other RFID reader / writers can be reduced. is there. In this case, interference due to return waves from a plurality of IC tags may occur. However, since the signal level is very small compared to interference from the RFID reader / writer, it can be substantially ignored.

  In the MS system, data is generated by repeating a baseband fundamental wave, which is synonymous with providing redundancy for encoding. Therefore, even if some bits are missing, there is a feature that reading errors are unlikely to occur.

  At the same time, the transfer rate is reduced by the amount of redundancy, and if the redundancy is M times the basic period, the transfer rate is reduced to 1 / M.

  As shown in the above example, the communication performance of a general RFID system, in particular the communication speed, and the immunity against large external noise and interference with other RFID reader / writers are in a contradictory relationship, and maximum in various communication environments. It was difficult to demonstrate the performance of.

  FIG. 12 is a schematic diagram illustrating communication interference in a conventional RFID reader / writer as disclosed in Patent Document 1. In FIG. In the figure, RFID reader / writers 1 and 11 perform encoding and decoding in logic circuits 3 and 13 according to instructions from control circuits 2 and 12, and analog signal amplification and transmission / reception separation in high-frequency analog circuits 4 and 14, respectively. Then, radio waves are transmitted from the antennas 5 and 15 toward the target IC tag. The RFID reader / writer 1 sets the IC tag 7 as a communication target.

  When the IC tag 7 that moves in the direction of the solid arrow in the figure and the RFID reader / writer 1 communicate with each other, the reception levels from all the channels that can be used are searched in advance, and the reception levels of the detected carriers are detected. Depending on the size, the transfer rate for newly communicating and the number of occupied channels are changed, the communication condition that maximizes the transfer rate under interference is selected, and the communication time is shortened.

  That is, the frequency of the channel used by the RFID reader / writer 11 on the interference side is detected by the RFID reader / writer 1, and the RFID reader / writer 1 avoids this channel and uses another channel, thereby enabling high-speed communication. It becomes possible.

  However, since the transmission frequency transmitted by the conventional RFID reader / writer and the response frequency returned by the IC tag are the same, in the area where there are a plurality of RFID reader / writers, there is essentially communication interference. There is a problem that cannot be avoided.

  In addition, since the communication conditions are set by searching all available channels before transmission from the RFID reader / writer, once communication is started, it cannot be changed in the middle, or the communication conditions are frequently changed. However, since all channels are searched every time, there is a problem that the time required for communication is not shortened.

  The present invention has been made to solve the problems of the prior art, and an object thereof is to provide an RFID reader / writer system capable of optimizing communication conditions between the RFID reader / writer and the IC tag.

According to the present invention, each of an IC tag that includes an IC chip and performs wireless communication, a plurality of RFID reader / writers that read or write the IC tag in a contactless manner by the communication, and the plurality of RFID reader / writers An RFID reader / writer system having a plurality of antennas connected to a reference IC tag for detecting the communication state is fixed within a range where the communication with one of the plurality of RFID reader / writers is possible And detecting the state of communication between one of the plurality of RFID reader / writers and the reference IC tag, and transmitting from one of the plurality of RFID reader / writers according to the detection result / Or encoding method and / or modulation method when replying from the IC tag, the communication state is optimal Code for configured to switch the system, if the no communication is desired the IC tag to a range that can be present, from the reference IC tag or the IC tag circuit the read of the detection result, for performing the communication When the desired IC tag exists in a range where communication is possible, the ID number of the reference IC tag and / or the IC tag circuit is not read. An RFID reader / writer system characterized by the above can be obtained.

  According to the present invention, an IC tag including an IC chip that performs wireless communication, an RFID reader / writer that reads or writes the IC tag in a contactless manner by the communication, and an antenna that is connected to the RFID reader / writer are provided. An RFID reader / writer system comprising an IC tag synthesis circuit including an IC tag circuit for impedance matching of a directional coupler and the IC chip and connecting the IC chip to the directional coupler, wherein the RFID reader / writer The antenna is connected via a tag synthesizing circuit, the communication state between the RFID reader / writer and the IC tag circuit is detected, and transmission from the RFID reader / writer and / or the IC tag is detected according to the detection result. The encoding method and / or modulation method used when replying from State the RFID reader-writer system is obtained, characterized by configured to switch the system to be optimized.

  According to the present invention, it is possible to obtain an RFID reader / writer system configured to detect the communication state using the number of readings per unit time of the reference IC tag or the IC tag circuit.

  According to the present invention, it is possible to obtain an RFID reader / writer system characterized by switching between the FM0 method and the mirror subcarrier method as the encoding method in the reply from the IC tag.

  According to the present invention, it is possible to obtain an RFID reader / writer system characterized in that a link frequency or M value can be changed using a mirror subcarrier method as the encoding method in the reply from the IC tag. .

According to the present invention, when the desired IC tag does not exist in a range where the communication is possible, the encoding for performing the communication is performed based on the detection result obtained by reading the reference IC tag or the IC tag circuit. switch the scheme and / or modulation scheme, wherein when the communication is the desired the IC tag to the extent possible is present, be configured not to take read ID number of the reference IC tag and / or the IC tag circuit An RFID reader / writer system characterized by the above can be obtained.

  According to the present invention, the antenna includes a radiating element that radiates radio waves and a feeding line that feeds power to the radiating element, and the feeding line forms at least a part of the IC tag synthesis circuit. RFID reader / writer system is obtained.

  According to the present invention, the IC tag synthesis circuit selects the directional coupler, the IC tag circuit, a termination circuit for terminating each connection, and either the IC tag circuit or the termination circuit. Thus, an RFID reader / writer system including a means for switching connections is obtained.

  In the present invention, the communication state with the reference IC tag or the IC tag circuit is constantly or periodically monitored, and when the communication state deteriorates due to interference with other RFID reader / writers, transmission from the RFID reader / writer and / or By switching the encoding method and / or modulation method used for reception from the IC tag to a method that optimizes the communication state, the communication state is always maintained well, even if the communication environment changes. Can perform optimal communication.

  According to the present invention, the communication state between the RFID reader / writer and the reference IC tag is detected, and the coding method and / or the modulation method of the RFID reader / writer and / or the IC tag are switched according to the detection result, thereby reducing the cost. It is possible to provide an RFID reader / writer system that can optimize communication conditions in a simple system.

  Further, according to the present invention, an IC tag synthesis circuit having the same function as the reference IC tag is provided between the RFID reader / writer and the antenna, and the communication state between the IC tag circuit and the RFID reader / writer provided in the IC tag synthesis circuit is set. By detecting, it is possible to optimize the communication conditions similar to the case of using the reference IC tag without providing the reference IC tag, so that the operation is easy and does not depend on the normal communication state with the reference IC tag. It is possible to provide an RFID reader / writer system that can perform stable determination and reliably optimize communication conditions.

It is the schematic which shows 1st Embodiment by this invention. It is the schematic which shows 2nd Embodiment by this invention. It is the schematic which shows the structure of the IC tag synthetic | combination circuit based on 2nd Embodiment by this invention. It is the schematic explaining the encoding system of RFID. It is the schematic which shows the example of the spectrum waveform in the encoding system of RFID. It is the schematic explaining the example of the waveform by the encoding system of RFID. It is the schematic explaining the difference of the waveform by the value of LF. It is the schematic explaining the example of the spectrum waveform in the encoding system of FIG. It is the schematic explaining the difference of the spectrum waveform by the value of LF. It is a figure explaining the change of the transfer rate by an encoding system and LF. It is a figure which shows the measurement result of the frequency | count of reading and interference level by 1st Embodiment. It is the schematic explaining the communication interference in the conventional RFID reader / writer. It is the schematic explaining the structure of the conventional antenna. 13A shows the front surface of the antenna, FIG. 13B shows the back surface of the antenna, and FIG. 13C shows the side surface of the antenna. It is the schematic which shows 3rd Embodiment by this invention. It is the schematic which shows 4th Embodiment by this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram showing a first embodiment according to the present invention.

  The overall configuration is obtained by adding a reference IC tag 6 to the conventional RFID reader / writers 1 and 11 shown in FIG. 12, and a description of the overlapping parts is omitted.

  The reference IC tag 6 faces the antenna 5 connected to the RFID reader / writer 1 and is fixedly installed in a communicable range. The RFID reader / writer 1 communicates with the reference IC tag 6 constantly or periodically to read ID information. In an environment where there is little influence of communication interference or external interference wave, a communication speed according to the transfer rate defined by the applied communication method can be obtained.

  When the desired IC tag 7 moves and passes in front of the antenna 5 and enters a communicable range, communication can be performed at the same communication speed as that of the reference IC tag 6.

  On the other hand, when another RFID reader / writer 11 is present in the vicinity of the RFID reader / writer 1 and the RFID reader / writer 11 also transmits a radio wave from the antenna 15 in the same manner, the radio wave from the RFID reader / writer 11 becomes an interference wave and the RFID Interference may occur with the transmission wave of the reader / writer 1 or the return wave from the IC tag.

  FIG. 6 is a schematic diagram illustrating an example of a waveform by an RFID encoding method. FIG. 10 is a diagram for explaining changes in the transfer rate due to the encoding method and LF.

  Here, examples of the FM0 method and the MS method are given as encoding methods at the time of transmission. In the case of the MS method, the M value (the number of waveforms having the minimum change period necessary to represent 1-bit data) is 2, 4 , 8 will be described.

  Since the MS system in FIG. 6 is a system in which the same pulse is repeated as compared with the FM0 system, it has a higher tolerance to external noise and interference. Moreover, the proof stress increases as the M value increases.

  On the other hand, as shown in FIG. 10, since the transfer rate decreases as the M value increases, the time required for communication increases. Therefore, the tolerance to interference and the communication speed (transfer rate) are in a trade-off relationship. In operation, it is desirable to select the optimum conditions.

  FIG. 8 is a schematic diagram illustrating an example of a spectrum waveform in the encoding method of FIG.

  (1) is a transmission wave from the RFID reader / writer 1, (2) is a reception wave returned from the reference IC tag 6, and (3) is an interference wave from the RFID reader / writer 11.

  In the figure, first, communication is performed at (a) FM0 having the maximum transfer rate. When the interference wave is generated, the reading performance of the received wave returned from the reference IC tag 6 is degraded. When the reading performance falls below a set threshold value, interference is improved by sequentially changing (b) MS M = 2, (c) MS M = 4, and (d) MS M = 8. The influence of waves can be suppressed. In the case of FIG. 8, by setting (c) MS M = 4, it is possible to ensure optimum reading performance with less interference.

  FIG. 7 is a schematic diagram for explaining the difference in waveform depending on the value of LF. FIG. 9 is a schematic diagram for explaining the difference in spectrum waveform depending on the value of LF, and shows a case where both the M value is 2 and LF is f, f / 2, and f / 4.

  FIG. 9 shows that optimum reading performance with less interference can be ensured by setting LF = f / 2, as in FIG.

  FIG. 11 is a diagram showing the measurement results of the number of readings and the interference level according to the first embodiment, and shows a measurement example when M = 4 and M = 8 in FIG. 6 or FIG.

  As measurement conditions, LF = 320 kHz, transmission wave frequency = 952.4 MHz, and interference wave frequency = 952.6 MHz. As the reading performance, the number of readings (ID number) of the IC tag per second is used.

  When the interference level is low, reading performance is higher when M = 4, but when the interference level exceeds a specific value, the IC tag cannot be read. On the other hand, when M = 8, the reading performance is lower than that of M = 4, but stable reading can be performed even when the interference level is high.

  Therefore, if the threshold value for switching to the method that optimizes the communication state based on the result of detecting the communication state between the RFID reader / writer 1 and the reference IC tag 6 is, for example, the number of readings is 20 times / second, the interference is low. By setting M = 4 and setting M = 8 when interference increases, an RFID reader / writer system capable of optimizing communication conditions with an inexpensive system can be configured.

(Second Embodiment)
FIG. 2 is a schematic diagram showing a second embodiment according to the present invention.

  The entire configuration is obtained by adding an IC tag synthesis circuit 8 between the conventional RFID reader / writer 1 and the antenna 5 shown in FIG.

  FIG. 3 is a schematic diagram showing a configuration of an IC tag synthesis circuit according to the second embodiment of the present invention.

  In the figure, the IC tag synthesis circuit 8 is composed of a directional coupler 9 and an IC tag circuit 10. The IC tag circuit 10 is a circuit that is impedance-matched to an IC chip used for an IC tag and can be directly connected by a connector.

  In FIG. 2, the IC tag synthesis circuit 8 is used instead of the reference IC tag 6 in the configuration of FIG. 1, and the reading performance of the IC tag circuit 10 inside the IC tag synthesis circuit 8 is measured.

  The transmission wave of the other RFID reader / writer 11 is input to the directional coupler 9 in the IC tag synthesis circuit 8 via the antenna 15, and a reply wave signal from the IC tag circuit 10 is transmitted by the directional coupler 9. And sent to the RFID reader / writer 1.

  In this case, the RFID reader / writer 1 and the antenna 5 are connected so that there is almost no loss, and the IC tag circuit 10 has a degree of coupling with the RFID reader / writer 1 and is connected to the antenna 5 so as to be isolated. With such a configuration, the same effect can be obtained without using the reference IC tag 6.

  With such a configuration, it is not necessary to install the reference IC tag 6, so that there is no problem that there is a shielding object that affects reading before the reference IC tag 6 and accurate detection cannot be performed. On the other hand, in the first embodiment shown in FIG. 1, since a cheap normal IC tag can be used as the reference IC tag 6, it is possible to configure a system that is less expensive than the second embodiment.

(Third embodiment)
FIG. 13 is a schematic diagram illustrating the configuration of a conventional antenna, and shows a general patch antenna as an example. 13A shows the front surface of the antenna, FIG. 13B shows the back surface of the antenna, and FIG. 13C shows the side surface of the antenna.

  The patch antenna of FIG. 13 includes a radiating element 21, a ground conductor plate 22, a feeding point 23, a feeding line 24, and a connector 25.

  In FIG. 13, a signal output transmitted from an RFID reader / writer (not shown) is input to a connector 25 via a coaxial cable (not shown). The input signal is fed to the feeding point 23 through the feeding line 24 and radiated from the radiating element 21 into the air as a radio wave.

  FIG. 14 is a schematic view showing a third embodiment according to the present invention, and relates to an RFID reader / writer system using an IC tag synthesis circuit instead of a reference IC tag as in the second embodiment according to the present invention. Is.

  In FIG. 14, in order to explain the structural difference from the patch antenna of FIG. 13, the back surface of the antenna is shown. In FIG. 14, the IC tag synthesis circuit 8 is incorporated in the power supply line 24, and functions as a directional coupler by forming a circuit pattern close to and in parallel with the power supply line 24.

  The IC tag circuit 10 and the termination circuit 26 are connected to the circuit pattern. In other words, the IC tag circuit 10 is arranged on the connector 25 side of the circuit pattern, the termination circuit 26 is arranged on the feeding point 23 side, and each terminal is connected to the ground conductor plate 22 on the ground side.

  With such a configuration, a signal input from the RFID reader / writer (not shown) to the connector 25 is transmitted to the feeding point 23 with almost no loss, while being transmitted to the IC tag circuit 10 with a loss of about several tens dB. The Therefore, a function similar to that of the IC tag synthesis circuit 8 shown in FIG. 3 can be obtained.

  The configuration shown in FIG. 14 eliminates the need for providing the IC tag synthesizing circuit 8 outside the apparatus, so that the installation is easy, and it is not necessary to provide an independent dedicated case, connector, or the like. There is an advantage that it contributes to reduction.

(Fourth embodiment)
FIG. 15 is a schematic view showing a fourth embodiment according to the present invention.

  In the present embodiment, as means for selecting either the IC tag circuit 10 or the termination circuit 27 and switching the connection, the switch 28 having two input terminals and one output terminal on the IC tag circuit 10 side in FIG. Is provided. With this configuration, when the IC tag circuit 10 is not used, the termination circuit 27 is selected by the switch 28 and the connection is switched to eliminate the influence of the IC tag circuit 10 and perform the same operation as a normal antenna. It can be carried out.

  That is, the RFID reader / writer system using the reference IC tag according to the first embodiment of the present invention and the RFID reader / writer system using the IC tag combining circuit according to the second and third embodiments of the present invention. Both systems can be handled with a single type of antenna.

  As a means for switching the connection, it is naturally possible to use a device other than a switch. For example, a part of the circuit pattern may be replaced with a cable, and a connector attached to the end of the cable may be inserted and removed.

  As described above, the RFID reader / writer 1 is monitored when the communication state with the reference IC tag 6 or the IC tag circuit 10 is constantly or periodically monitored and the communication state deteriorates due to interference with other RFID reader / writers 11. By switching the encoding method and / or modulation method used for transmission from and / or reception from the IC tag 7 to a method that optimizes the communication state, the communication state is always kept good and the communication environment has changed. Even in this case, the optimum communication at that time can be performed.

  The reference IC tag 6 or the IC tag circuit 10 reads only when there is no other IC tag. When an IC tag that is originally read is detected, the ID number of the reference IC tag 6 or the IC tag circuit 10 is set. On the other hand, by applying a filter on the RFID reader / writer 1 side so as not to read, the influence on normal reading can be eliminated.

  In the above-described embodiment, the number of readings per unit time has been described as an example of reading performance. However, the present invention is not limited to this, and it is obvious that a similar function can be performed by those having the same function. It is.

DESCRIPTION OF SYMBOLS 1,11 RFID reader / writer 2,12 Control circuit 3,13 Logic circuit 4,14 High frequency analog circuit 5,15 Antenna 6 Reference IC tag 7 IC tag 8 IC tag composition circuit 9 Directional coupler 10 IC tag circuit 21 Radiating element 22 Ground conductor plate 23 Feed point 24 Feed line 25 Connector 26, 27 Termination circuit 28 Switch

Claims (8)

An IC tag including an IC chip that communicates wirelessly, a plurality of RFID readers / writers that read or write the IC tag without contact through the communications, and a plurality of antennas that are connected to each of the plurality of RFID reader / writers An RFID reader / writer system having a reference IC tag for detecting the communication state in a range where the communication with one of the plurality of RFID reader / writers is possible, A state of the communication between one of a plurality of RFID reader / writers and the reference IC tag is detected, and transmission from one of the plurality of RFID reader / writers and / or from the IC tag according to the detection result Switching the encoding method and / or modulation method when sending a reply to the method that optimizes the communication status Configured such, when said communication is desired the IC tag to the extent possible does not exist, from the reference IC tag or the IC tag circuit the read of the detection result, the coding scheme for performing the communication and And / or switching the modulation method, and when the desired IC tag exists in a range where the communication is possible, the ID number of the reference IC tag and / or the IC tag circuit is not read. RFID reader / writer system.   An RFID reader / writer system having an IC tag equipped with an IC chip for wireless communication, an RFID reader / writer for reading or writing the IC tag without contact by the communication, and an antenna connected to the RFID reader / writer. And an IC tag synthesizing circuit including an IC tag circuit for impedance matching of the IC chip and connecting to the directional coupler, and the RFID reader / writer is connected via the IC tag synthesizing circuit. When the antenna is connected, the state of communication between the RFID reader / writer and the IC tag circuit is detected, and transmission from the RFID reader / writer and / or reply from the IC tag is performed according to the detection result The coding state and / or modulation method of the communication state is optimized. RFID reader-writer system, characterized by configured to switch to expression. When the desired IC tag does not exist in the range where communication is possible, the encoding method and / or the modulation method for performing the communication based on the detection result obtained by reading the reference IC tag or the IC tag circuit The ID number of the reference IC tag and / or the IC tag circuit is not read when the desired IC tag exists in a range where the communication is possible. 2. The RFID reader / writer system according to 2. Characterized by configured to sense a state of the communication using the number of reads per the reference IC tag or the IC tag circuit, a unit time, RFID reader-writer according to any one of claims 1 to 3 system. As the encoding scheme in the response from the IC tag, and switches the FM0 scheme and the mirror sub-carrier method, RFID reader-writer system according to any one of claims 1 to 3. The RFID according to any one of claims 1 to 3, wherein a link frequency or an M value can be changed using a mirror subcarrier method as the encoding method in the reply from the IC tag. Reader / writer system.   The antenna includes a radiating element that radiates radio waves and a feeding line that feeds power to the radiating element, and the feeding line forms at least a part of the IC tag synthesis circuit. 7. The RFID reader / writer system according to any one of 6 above.   The IC tag synthesizing circuit includes a directional coupler, the IC tag circuit, a termination circuit that terminates each connection, and a means for selecting one of the IC tag circuit or the termination circuit and switching the connection. The RFID reader / writer system according to claim 7, further comprising:

Images