JP4963686B2 - RFID antenna device - Google Patents

Description

  The present invention relates to an RFID antenna device connected to a reader / writer for reading or writing an IC tag, and more particularly to an RFID antenna device having portability.

  An antenna for wireless communication is connected to a reader / writer that reads or writes an IC tag, and signal power transmitted from the reader / writer is transmitted as a radio wave from the antenna, thereby communicating with the IC tag. It can be performed.

  FIG. 5 is a diagram showing a first configuration example of a conventional reader / writer, in which a reader / writer 6 and an antenna 2 provided in the antenna case 1 are provided separately, and the reader / writer 6 and the antenna 2 are connected to a transmission line 10. It is a block diagram which shows the structure connected by.

  In accordance with an instruction from a control circuit 7 provided in the reader / writer 6, the logic circuit 8 performs encoding / combining, the high-frequency analog circuit 9 performs amplification / transmission / reception separation of the analog signal, and the antenna via the transmission line 10. Communication between the IC tag and the reader / writer 6 is performed by transmitting radio waves from an antenna 2 provided in the case 1 toward an IC tag (not shown).

  FIG. 6 is a diagram showing an example of the configuration of an antenna in a conventional reader / writer. A coaxial cable composed of a signal line 11 and a ground line 12 is connected to the antenna 2 provided in the antenna case 1 as a transmission line 10. The

  FIG. 7 is a diagram illustrating a second configuration example of a conventional reader / writer.

  The basic configuration and operation are the same as those of the first configuration example of the conventional reader / writer shown in FIG. 5, but in the example of FIG. 7, the switch 13 is provided in the antenna case 1 and the reader is connected by the control line 14. It is connected to the control circuit 7 of the writer 6, and the operation of the control circuit 7 can be controlled by operating the switch 13, and the transmission or stop of the radio wave from the antenna 2 can be remotely operated.

  Such a configuration is often used in a stationary type or gate type system in which the apparatus is relatively large and requires a long communication distance, and the reader / writer is separated by separating the antenna 2 and the reader / writer 6. 6 itself can be miniaturized, and the degree of freedom of arrangement of each member is improved, so that only the antenna 2 can be arranged in the vicinity of the IC tag, or the antenna 2 can be held and held over a desired IC tag. This increases convenience. Such a configuration is disclosed in Patent Document 1, for example.

  FIG. 8 is a diagram showing a third configuration example of a conventional reader / writer, which has a so-called handy type structure in which an antenna is installed in a reader / writer main body case so that an operator can hold it by hand. It is an integrated one.

  The handy reader / writer 16 includes a control circuit 7, a logic circuit 8, a high frequency analog circuit 9, and an antenna 2. The read or write operation is the same as in the example of FIGS. 5 and 7, but the configuration of FIG. 8 houses a primary or secondary battery 15 inside so that an operator can carry and use the device. .

  Such a handy type system is widely used in place of a conventional bar code reader because it can be operated in a wide range of places and has good workability.

JP 2006-60763 A

  However, in the system such as the first configuration example of the conventional reader / writer shown in FIG. 5, radio waves are always transmitted from the reader / writer 6 via the antenna 2, so that not only a desired IC tag but also other ICs are used. There is a possibility that communication may be performed with the tag, and there is a problem that the IC tag cannot be reliably read.

  Further, in the system like the second configuration example in the conventional reader / writer shown in FIG. 7, it is possible to communicate with a desired IC tag by transmitting a radio wave only when communication is necessary. A control line is required separately from the transmission line, and there is a problem that the configuration of the apparatus becomes complicated and the apparatus cost of the reader / writer increases.

  Further, in the system such as the third configuration example of the conventional reader / writer shown in FIG. 8, since a battery is used as an operation power source of the device, there is a problem that continuous use time is limited, and power consumption is reduced. There is a problem that it is difficult to increase the output of radio waves because of the necessity to suppress it, and therefore the communication distance with the IC tag cannot be increased.

  The object of the present invention is to solve the above-mentioned problems of the prior art and realize a reader / writer device that can perform reliable communication with a desired IC tag, suppress the price of the reader / writer, can be used continuously, and has a long communication distance. It is an object of the present invention to provide an RFID antenna device that can be used.

According to the present invention, the reader / writer and the antenna are provided by including an antenna, a switch circuit, and an impedance circuit provided in an antenna case, connected to a reader / writer that reads or writes an IC tag, and switching the switch circuit. An antenna device that selects conduction or disconnection with the antenna , wherein the antenna and the impedance circuit are connected to the switch circuit, the switch circuit is connected to the reader / writer via a transmission line, and the switch circuit is switched. And selecting the antenna enables communication with the IC tag, and selecting the impedance circuit disables communication with the IC tag. An RFID antenna device is obtained.

  Further, according to the present invention, there is obtained an RFID antenna device characterized in that the impedance circuit is matched in characteristic impedance with the transmission line.

  In the present invention, the reader / writer is separated from the antenna case in which the antenna connected to the switch circuit is provided, and the reader / writer and the antenna are selected to be conductive or disconnected by switching the switch circuit. By bringing the antenna disconnected from the writer close to the desired IC tag and then operating the switch circuit to select the continuity between the reader / writer and the antenna, the desired IC tag can be read without erroneous reading. It is possible to communicate with only the IC tag.

  Further, according to the configuration of the present invention, since a control line for switching the switch circuit is unnecessary, the configuration of the apparatus is simplified and the price of the reader / writer can be suppressed.

  Furthermore, in the present invention, by using the antenna and the reader / writer as separate bodies, it is possible to use the antenna close to the place where the IC tag is installed as in the conventional handy type. Compared to the handy type, the reader / writer itself can be installed in a place where commercial power can be used, so there is no need to replace exhausted batteries or recharge them. The communication distance can be extended by increasing the distance.

  Note that it is desirable that the reader / writer to be used has a function of stopping transmission of signal power when the switch circuit is disconnected from the antenna. This is because if signal power is transmitted in a state in which continuity with the antenna is cut off, reflection occurs at the end of the transmission line, that is, the switch circuit, and there is a possibility that the amplifier or the like of the high-frequency analog circuit may be damaged.

  On the other hand, when the conduction between the transmission line and the antenna is cut off via the switch circuit between the transmission line connected to the reader / writer and the antenna as in the present invention, the impedance circuit is selected to conduct. This makes it possible to reduce the reflection of the signal power sent from the reader / writer, and avoid the above-mentioned troubles even when using a reader / writer that does not have a function to stop sending the signal power. Therefore, the application range to the reader / writer can be expanded. Further, if the impedance of the impedance circuit is matched with the characteristic impedance of the transmission line so that the reflection of the signal power is eliminated, the effect of avoiding the above-mentioned device failure is further enhanced.

  As described above, according to the present invention, it is possible to realize a reader / writer device that can perform reliable communication with a desired IC tag, reduce the price of the reader / writer, can be used continuously, and has a long communication distance. An RFID antenna device capable of being provided can be provided.

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

  FIG. 1 is a diagram showing a first embodiment of the present invention. An antenna 2 provided in the antenna case 1 is connected to a switch circuit 3 and connected to a reader / writer 6 having a control circuit 7, a logic circuit 8, and a high-frequency analog circuit 9 through a transmission line 10.

  FIG. 2 is a diagram showing the configuration of the antenna case according to the first embodiment of the present invention.

  The antenna 2 is connected to the switch circuit 3 and is installed in the antenna case 1. In the transmission line 10 constituted by a coaxial cable, the signal line 11 is connected to the switch circuit 3 and the ground line 12 is connected to the antenna 2. FIG. 2 shows a state in which disconnection of conduction is selected by the switch circuit 3, and the antenna 2 and the signal line 11 of the transmission line 10 are not conductive. When conduction is selected by the switch circuit 3, the antenna 2 and the signal line 11 of the transmission line 10 become conductive, and communication with the IC tag is possible.

  In FIG. 1, when the reader / writer 6 is activated, signal power for communication is transmitted from the high-frequency analog circuit 9 and input to the switch circuit 3 via the transmission line 10. When the antenna 2 is selected and conducted by the switch circuit 3, radio waves are transmitted from the antenna 2 to an IC tag (not shown) to perform communication. In addition, when the switch circuit 3 is disconnected from the antenna 2, no radio wave is transmitted, so that communication with the IC tag is not performed.

  With such a configuration, the antenna 2 is brought close to a desired IC tag, and radio waves are transmitted only when communication is necessary, so that it is possible to reliably connect to the desired IC tag without performing communication with an unnecessary IC tag. Communication is possible.

  The above configuration is suitable for a usage method in which the antenna case 1 is held by hand and is held over an IC tag for communication.

  FIG. 3 is a diagram showing a second embodiment of the present invention. An antenna 2 and an impedance circuit 5 provided in the antenna case 1 are connected to a switch circuit 4 and a reader having a control circuit 7, a logic circuit 8, and a high-frequency analog circuit 9 through a transmission line 10 as in the example of FIG. Connect to writer 6.

  FIG. 4 is a diagram showing a configuration of an antenna case according to the second embodiment of the present invention.

  The antenna 2 and the impedance circuit 5 installed in the antenna case 1 are connected to the switch circuit 4. The transmission line 10 constituted by a coaxial cable has the signal line 11 as the switch circuit 4 and the ground line 12 as the antenna 2 and the switch circuit. 4 is connected. FIG. 4 shows a state where the switch circuit 4 has selected conduction between the impedance circuit 5 and the antenna 2 and the signal line 11 of the transmission line 10 are not conducted. When the switch circuit 4 selects the continuity with the antenna 2, the continuity between the impedance circuit 5 and the signal line 11 is cut off, the antenna 2 and the signal line 11 are brought into a conductive state, and communication with the IC tag is possible.

  In FIG. 3, the transmission line 10 is switched to either the antenna 2 or the impedance circuit 5 by the switch circuit 4 and is turned on to select the destination of the signal power sent from the reader / writer 6 via the transmission line 10. When the transmission line 10 is electrically connected to the antenna 2 by the switch circuit 4, the communication with the IC tag is performed in the same manner as in the first embodiment shown in FIG.

  On the other hand, when communication with the IC tag is not performed, transmission of radio waves from the antenna 2 can be stopped by connecting the transmission line 10 and the impedance circuit 5 by switching the switch circuit 4, and signal power can be reduced. Even when a reader / writer that does not have a transmission stop function is used, it is possible to avoid the signal power transmitted through the transmission line 10 from being reflected and causing an obstacle to the high-frequency analog circuit 9 of the reader / writer 6.

  In addition, if the impedance of the impedance circuit 5 and the characteristic impedance of the transmission line 10 are matched, the reflection of the signal power is extremely reduced, so that even if a standby state in which communication with the IC tag is not performed for a long time continues, the device may be damaged. The possibility of giving is further reduced, which is more preferable.

  In both the above embodiments, the switch circuit 3 or 4 conducts or disconnects the transmission line 10 and the antenna 2, or the connection destination of the transmission line 10 is selected from the antenna 2 or the impedance circuit 5, that is, In order to switch the switch circuit 3 or 4, a configuration in which an operation switch is provided on the antenna case 1 itself as a switching means for the switch circuit 3 or 4 is simple, reliable, and desirable. However, depending on the required usage, the reader / writer 6 side It is also possible to send a signal for operating the switch circuit 3 or 4 via the transmission line 10 and switch the switch circuit 3 or 4 by remote control.

  As mentioned above, although embodiment of this invention was described using drawing, this invention is not limited to these embodiment, There exists a change of a member and a structure in the range which does not deviate from the summary of this invention. Are also included in the present invention. For example, in the above embodiment, the operation method is described assuming that the operator holds and operates the antenna case 1 by hand. However, depending on the usage status of the device, such a structure is not necessarily required. Needless to say, even if the antenna case is fixedly installed or the switch operation is not performed manually, for example, the switch is turned on by the weight of the article placed on the device, the embodiment of the present invention is similarly formed. . That is, various modifications and corrections that can naturally be made by those skilled in the art are also included in the present invention.

The figure which shows the 1st Embodiment of this invention. The figure which shows the structure of the antenna case by the 1st Embodiment of this invention. The figure which shows the 2nd Embodiment of this invention. The figure which shows the structure of the antenna case by the 2nd Embodiment of this invention. The figure which shows the 1st structural example in the conventional reader / writer. The figure which shows an example of the structure of the antenna in the conventional reader / writer. The figure which shows the 2nd structural example in the conventional reader / writer. The figure which shows the 3rd structural example in the conventional reader / writer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna case 2 Antenna 3, 4 Switch circuit 5 Impedance circuit 6 Reader / writer 7 Control circuit 8 Logic circuit 9 High frequency analog circuit 10 Transmission line 11 Signal line 12 Ground line 13 Switch 14 Control line 15 Battery 16 Handheld reader / writer

Claims (2)

The antenna case includes an antenna, a switch circuit, and an impedance circuit, and is connected to a reader / writer that reads or writes an IC tag. By switching the switch circuit, the reader / writer and the antenna are connected or disconnected. The antenna device to be selected , wherein the antenna and the impedance circuit are connected to the switch circuit, the switch circuit is connected to the reader / writer via a transmission line, and the switch circuit is switched to select the antenna Thus, the RFID antenna device is configured such that communication with the IC tag is enabled and communication with the IC tag cannot be performed by selecting the impedance circuit . The RFID antenna device according to claim 1 , wherein the impedance circuit is matched in characteristic impedance with the transmission line.

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