JP4834651B2 - Wireless communication apparatus and control method thereof - Google Patents

Description

  The present invention relates to a wireless communication apparatus including an antenna that radiates read radio waves to a radio tag and receives response radio waves from the radio tag with respect to the read radio waves, and a control method thereof.

  In recent years, a wireless communication device and a wireless tag (also referred to as an IC tag, an RFID tag, an electronic tag, a transponder, etc.) provided with an IC chip, both of which communicate data via an antenna, An RFID (Radio Frequency Identification) system in which a wireless communication apparatus can read information on a wireless tag in a non-contact manner has become widespread.

  In this RFID system, a radio communication device radiates a radio frequency signal for querying a radio tag from an antenna as a radio wave. When a radio tag receives a radio wave from a radio communication device with a built-in antenna, information stored in an IC chip Thus, backscatter modulation is performed by changing the reflection amount of the high-frequency signal. When the wireless communication device receives the backscatter modulated wave from the wireless tag by the antenna, the wireless communication device demodulates it and reads the information of the wireless tag.

However, when there are a plurality of wireless tags in the communication area of the wireless communication device, there is a case where a collision of received data occurs and accurate data is not recognized. Therefore, at the implementation stage, collision avoidance of received data is attempted by using an anti-collision (collision prevention) technique. (For example, see Patent Document 1)
Typical anti-collision methods include a binary tree method and a time slot method. The time slot method is an access control method widely used in packet communication such as a wireless local area network (LAN), and is also called an ALOHA method.

An operation of a general time slot type anti-collision function will be described. First, the wireless communication apparatus designates specific bits (2 ⁰ to 2 ^Q : Q is a fixed value of ≧ 1) as a time slot for a wireless tag existing in the communication area of the antenna. The wireless tag that has received the designation of the time slot generates a random number within the bit range. For example, when the time slot is 2 bits (Q = 1), the communication medium generates a 2-bit random number “00”, “01”, “10”, or “11”. Then, a response is returned to the wireless communication device using a time slot having a timing that matches the generated random number.

  At this time, when only one wireless tag returns a response to one time slot, the wireless tag data is received by the wireless communication device. However, when a plurality of wireless tags respond to one time slot, data collision occurs, and data of those wireless tags is not received. The wireless communication device sends a sleep command to the wireless tag that has received the data so as not to participate in subsequent responses.

On the other hand, a random number is generated again for the wireless tag that has collided. Then, a response is returned to the wireless communication device using a time slot having a timing that matches the generated random number. By repeating such a series of processing, the wireless communication apparatus can receive data from a plurality of wireless tags substantially simultaneously.
JP 2006-72672 A

  The RFID system using the above-described time slot type anti-collision technique is applied to a system that detects the passage of a wireless tag attached to a product or the like, such as a shoplifting prevention system. In such a system, when data is received from a wireless tag that passes through a gate equipped with an antenna, a predetermined process such as operating an alarm device based on the data is executed.

  Here, in order to cope with a case where a large number of wireless tags pass through the gate at the same time, it is necessary to set the Q value to be somewhat large. However, in such a setting, the number of time slots increases, so the monitoring cycle of the wireless tag is increased. It will be long. Therefore, a wireless tag that has not been detected before the end of one monitoring cycle may pass through the gate. On the other hand, if the Q value is set to be small, the number of time slots is reduced, and the occurrence of collision increases. For this reason, there is a case where a single wireless tag cannot be detected because a collision occurs all the time while the wireless tag passes through the gate.

  The present invention has been made based on the above situation, and an object of the present invention is to provide a wireless communication apparatus and a control method thereof capable of detecting a wireless tag in an antenna communication area in a short time and with certainty. Is to provide.

  A wireless communication apparatus according to the present invention is a wireless communication apparatus including an antenna that radiates a read radio wave to a radio tag and receives a response radio wave from the radio tag with respect to the read radio wave. The radio communication apparatus is fixed in a communication area of the antenna. Radio wave radiating means for radiating a read radio wave from the antenna to cause the fixed tag that is a wireless tag and the monitoring tag that is a radio tag attached to an object to be monitored to respond in the same time slot, and the radio wave radiating means A receiving unit that processes the response radio wave received by the antenna with respect to the read radio wave radiated by the signal and demodulates the data into predetermined data; and the response radio wave from the fixed tag and the monitoring based on the data demodulated by the receiving unit Judgment means for judging whether or not the response radio wave from the tag collides, and this judgment means is the response radio wave from the fixed tag and the response from the monitoring tag When it is determined that the waves and collide, and characterized by being provided with informing means for informing to that effect, the.

  According to the present invention in which such measures are taken, it is possible to provide a wireless communication apparatus and a control method therefor that can detect a wireless tag in the antenna communication area in a short time and with certainty.

  The best mode for carrying out the present invention will be described below with reference to the drawings. In this embodiment, an example in which the wireless communication apparatus according to the present invention is applied to a shoplifting prevention system installed in a retail store or the like will be described.

  FIG. 1 is a schematic perspective view showing a usage mode of a wireless communication device 10 according to the present invention. The wireless communication device 10 includes an antenna stand 30 that includes an antenna that radiates read radio waves to the radio tag and receives response radio waves from the radio tag, and an alarm device 40 that includes sound generation means that emits a predetermined warning sound. Are connected to each other via a wired or wireless communication. The antenna stand 30 is disposed opposite to a stand 31 that does not have an antenna to constitute a gate 32. A radio wave having directivity in the direction of the stand 31 is radiated from the antenna built in the antenna stand 30.

  FIG. 2 is a schematic perspective view showing the internal structure of the antenna stand 30. The antenna stand 30 includes four antennas 1, 2, 3, and 4. On the surface of the directivity direction side of the radio wave radiated from each antenna 1, 2, 3 and 4, predetermined data is sent to the center of one end parallel to the arrangement direction of each antenna 1, 2, 3 and 4 as an IC chip The fixed tag 5 which is the wireless tag stored in is installed. Each fixed tag 5 belongs to a communication area of only the installed antenna, and each fixed tag 5 always returns a response radio wave when a read radio wave is emitted from the installed antenna. .

  In a store where the shoplifting prevention system is installed, a product tag, which is a wireless tag storing product data or the like in an IC, is attached to each product to be monitored. The product tag is removed at the time of accounting for the attached product, and the customer who has finished accounting for the product passes the gate 32 and leaves the store. The fixed tag 5 and the product tag are wireless tags that determine a time slot that responds based on a Q value that is a setting value for determining the number of time slots designated by the wireless communication device 10.

  The wireless communication device 10 radiates a read radio wave accompanied by a command for setting the Q value to 0 when the wireless tag is read. That is, the fixed tag and the monitoring tag are caused to respond in the same time slot by radiating a read radio wave with a set value that makes the number of time slots unitary. That is, when a reading radio wave is radiated from any of the antennas 1, 2, 3, and 4, and there is a product tag in the communication area of the antenna, the same time slot as the fixed tag 5 installed in the antenna Because the product tag returns a response radio wave, a collision occurs. Therefore, in such a case, the wireless communication device 10 cannot read the fixed tag 5.

  FIG. 3 is a block diagram illustrating a main configuration of the wireless communication device 10. The wireless communication device 10 includes a control unit 11 mainly composed of a CPU (Central Processing Unit), a storage unit 12 composed of a ROM (Read Only Memory) and a RAM (Random Access Memory), an external device such as an alarm device 40, and various devices. A communication unit 13 that transmits and receives data, a timer 14 that measures time at a predetermined timing, a wireless unit 16 that performs various processes related to wireless data transmission and reception, and an antenna selection switch 17 that switches an antenna connected to the wireless unit 16 are provided. ing.

  The alarm device 40 connected via the communication unit 13 operates to sound an alarm when receiving an operation command from the control unit 11. On the other hand, the alarm device 40 stops its operation when receiving a stop command from the control unit 11 during its operation.

  The radio unit 16 includes a PLL (Phase Locked Loop) circuit 19, a transmission unit 18, a circulator 22, a reception unit 20, and an RSSI (Receive Signal Strength Indicator) circuit 21. The PLL circuit 19 generates a high-frequency sine wave signal. The transmission unit 18 modulates the digital data sent from the control unit 11, amplifies a high frequency signal obtained by adding the modulation signal and the high frequency signal generated by the PLL circuit 19 to a predetermined output level, and circulators 22. Output to.

  Here, the antenna selection switch 17 is interposed between the circulator 22 and each of the antennas 1, 2, 3, 4, and operates to switch to the connection terminal designated by the control signal S 1 from the control unit 11. , 2, 3 and 4 are connected to the circulator 22. When a high frequency signal is input from the transmission unit 18, the circulator 22 outputs the high frequency signal to any one of the antennas 1, 2, 3, and 4 via the antenna selection switch 17. The antenna that receives the output of the high-frequency signal radiates the high-frequency signal as a radio wave read by the wireless tag.

  Here, when the wireless tag receives the read radio wave radiated from any one of the antennas, the wireless tag performs back scatter modulation that changes the reflection amount of the high-frequency signal with the data stored in the IC chip. Each of the antennas 1, 2, 3, and 4 receives the backscatter modulated high frequency signal as a response radio wave.

At this time, the response radio wave received by the antenna connected to the circulator 22 by the antenna selection switch 17 is converted into a high frequency signal and input to the circulator 22. The circulator 22 has a characteristic of outputting to the receiving unit 20 side when a high frequency signal is inputted from the antennas 1, 2, 3, 4 side. The receiving unit 20 amplifies the input high-frequency signal, then combines the amplified high-frequency signal and the high-frequency signal of the PLL circuit 19 to convert it to a baseband signal, and then demodulates the baseband signal to digital data. And output to the control unit 11. The RSSI circuit 21 generates an analog signal indicating the level of the signal demodulated by the receiving unit 20.
In this way, the wireless communication device 10 can read the tag data stored in the wireless tag in the communication area of each antenna 1, 2, 3, 4 in a contactless manner.

  Next, the effect | action by the structure of the radio | wireless communication apparatus 10 in the above shoplifting prevention systems is demonstrated. FIG. 4 is a flowchart of processing executed by the control unit 11 of the wireless communication apparatus 10 during operation of the shoplifting prevention system. First, the control unit 11 issues a control signal S1 to the antenna selection switch 17 as ST1, and connects any one of the antennas 1, 2, 3, and 4 to the radio unit 16 (antenna setting means). Thereafter, the control unit 11 outputs digital data for reading the wireless tag to the transmission unit 18 as ST2. The transmitter 18 demodulates the digital data, amplifies the high frequency signal obtained by adding the modulated signal and the high frequency signal generated by the PLL circuit 19 to a predetermined output level, and outputs the amplified signal to the circulator 22. The circulator 22 outputs this high-frequency signal to the antenna connected via the antenna selection switch 17, and the antenna that has received this output radiates the high-frequency signal as a read radio wave (radiation means). In response to the read radio wave, the fixed tag 5 installed on the antenna that radiates the read radio wave always returns a response radio wave. Since the read radio wave is accompanied by a command for setting the Q value to 0 as described above, if the product tag exists in the communication area of the antenna that radiates the read radio wave, the product tag is also the same as the fixed tag 5. A response radio wave is returned in the time slot. The antenna that receives these response radio waves converts the response radio wave into a high-frequency signal and outputs it to the receiving unit 20 via the antenna selection switch 17 and the circulator 22. Then, the receiving unit 20 amplifies the input high frequency signal and converts it into a baseband signal by combining with the high frequency signal of the PLL circuit 19. The receiving unit 20 demodulates the baseband signal and converts it into digital data, and then outputs the digital data to the control unit 11.

  Thereafter, the control unit 11 compares the digital data demodulated as ST3 with the tag data of the fixed tag 5 stored in advance in the storage unit 12 to determine whether the tag data of the fixed tag 5 has been read. Judgment (determination means). When it is determined that the tag data of the fixed tag 5 has been read (Yes in ST3), the process returns to ST1 and antenna setting is performed again. At this time, which of antennas 1, 2, 3, and 4 is set is not particularly limited. For example, antenna 1, antenna 2, antenna 3, and antenna 4 are sequentially set every time the antenna setting process is performed.

  When it is determined in the process of ST3 that the tag data of the fixed tag 5 is not read (No in ST3), the control unit 11 transmits an operation command to the alarm device 40 via the communication unit 13 as ST4. The alarm device 40 that has received this operation command starts its operation and sounds an alarm (notification means). After that, the timer 14 is operated as ST5 and waits for elapse of a predetermined time set in advance. When it is determined that the predetermined time has elapsed (Yes in ST5), the control unit 11 transmits a stop command to the alarm device 40 via the communication unit 13 as ST6. The alarm device 40 that has received this stop signal stops its operation. Thereafter, during the operation of the shoplifting prevention system, the control unit 11 repeats the processes of ST1 to ST6.

  Thus, the wireless communication device 10 in the shoplifting prevention system cannot read the tag data of the fixed tag 5 installed on the antenna after radiating the read radio wave from each antenna 1, 2, 3, 4 If the alarm occurs, the alarm 40 is activated to sound an alarm. In such a case, there is a case where the fixed tag 5 cannot be read because the product tag enters the communication area of the antenna that radiates the read radio wave and the response radio wave between the product tag and the fixed tag 5 collides. Applicable. That is, by monitoring the collision between the fixed tag 5 and the product tag, it is possible to prevent unsettled products from being taken out.

  In the shoplifting prevention system, since the Q value for determining the number of time slots to be used is 0, that is, only a single tom slot is used, the product tag monitoring cycle is the shortest setting in the time slot type anti-collision method. Therefore, since the monitoring cycle is long, the probability of passing through the security gate without detecting the product tag is lowered. On the other hand, even when a large number of products with product tags attached are about to be taken out at the same time, if the wireless communication device 10 that detects fraud is detected by the occurrence of a collision, the response radio waves between the product tags may collide. Product tags can be detected reliably without need.

  The present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.

  For example, the number of antennas connected to the wireless communication apparatus 10 is not limited to four, and may be more or fewer. When connecting a different number of antennas, the number of connection terminals of the antenna selection switch 17 may be added or deleted in accordance with the number of antennas, and the connection terminals may be adjusted to be switchable by the control signal S1.

  Further, the position where the fixed tag 5 is installed is not limited to the position shown in FIG. 2 as long as it can be reliably read from each antenna, and the reading can be performed without preparing one fixed tag 5 for each antenna. If one fixed tag 5 returns a response radio wave to radio wave radiation, a configuration may be adopted in which one fixed tag 5 is installed for a plurality of antennas.

  In addition, the notification means is not limited to the alarm device 40, but instead of the alarm device 40 or using a circuit breaker or the like that blocks traffic between the gates 32 when the passage of the product tag is detected together with the alarm device 40. Or you may make it alert | report by the other method.

  In addition, in the shoplifting prevention system according to the present embodiment, the product tag affixed to the product is removed after the transaction and the gate 32 is passed, but the present invention is not limited to this mode. For example, each product tag is provided with a flag for determining whether or not to return a response radio wave to the read radio wave, and the flag attached to the product before the transaction is set to valid (response radio wave is returned). Then, the cashier sets the flag to invalid (does not return a response radio wave) by a predetermined operation after the commodity is checked. Thereafter, the customer leaves the store through the gate 32 with the product tag attached to the product. In other words, because the flag is set to invalid for the product tag attached to the product after accounting, the response radio wave is not returned to the read radio wave even when passing through the antenna communication area. Since the flag of the previous product is set to be valid, a response radio wave is returned to the read radio wave when passing through the antenna communication area. Therefore, the wireless communication device 10 can detect only the passage of the product tag attached to the product before the transaction.

  In the present embodiment, an example in which the wireless communication apparatus 10 is applied to a shoplifting prevention system has been described. However, the present invention may be applied to other systems in which it is effective to detect a predetermined wireless tag that passes through a gate.

  When the product tag is read without reading the fixed tag 5 or when the fixed tag cannot be read continuously for a predetermined number of times, the wireless communication device 10 determines that the fixed tag 5 or the antenna is malfunctioning, You may make it alert | report by using the alarm device 40.

  In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment.

1 is a schematic perspective view illustrating a usage mode of a wireless communication device according to an embodiment of the present invention. The typical perspective view which shows the internal structure of the antenna stand in the embodiment. The block diagram which shows the principal part structure of the radio | wireless communication apparatus in the embodiment. The flowchart of the process which the control part of a radio | wireless communication apparatus performs in the embodiment.

Explanation of symbols

1, 2, 3, 4 ... antenna, 5 ... fixed tag, 10 ... wireless communication device, 11 ... control unit, 12 ... storage unit, 13 ... communication unit, 14 ... timer, 16 ... wireless unit, 17 ... antenna selection switch , 18 ... Transmitter, 19 ... PLL circuit, 20 ... Receiver, 21 ... RSSI circuit, 22 ... Circulator, 30 ... Antenna stand, 31 ... Stand, 32 ... Gate, 40 ... Alarm

Claims (5)

In a wireless communication device including an antenna that radiates a read radio wave to a radio tag and receives a response radio wave from the radio tag with respect to the read radio wave,
Read radio waves that cause a fixed tag, which is a wireless tag fixed in the communication area of the antenna, and a monitoring tag, which is a wireless tag attached to an object to be monitored, to respond in the same time slot are radiated from the antenna. Radio wave radiation means;
A receiving unit that processes the response radio wave received by the antenna with respect to the read radio wave radiated by the radio wave radiating means and demodulates the data into predetermined data;
Based on the data demodulated by the receiving unit, determination means for determining whether or not the response radio wave from the fixed tag and the response radio wave from the monitoring tag collide,
When this determination means determines that the response radio wave from the fixed tag and the response radio wave from the monitoring tag have collided, an informing means for informing that effect,
A wireless communication apparatus comprising:   The notification means notifies that the monitoring tag has been detected when the determination means determines that the response radio wave from the fixed tag and the response radio wave from the monitoring tag have collided. The wireless communication device according to 1. A plurality of the antennas;
An antenna setting means for selectively setting an antenna used for receiving the read radio wave and receiving the response radio wave from the plurality of the antennas;
The wireless communication apparatus according to claim 1, further comprising: The fixed tag and the monitoring tag are wireless tags for determining a time slot to respond based on a setting value for determining the number of time slots designated from the wireless communication device,
The radio wave radiating means radiates the read radio wave accompanied by designation of the set value with a single time slot number, thereby causing the fixed tag and the monitoring tag to respond in the same time slot. The wireless communication device according to claim 1. A method for controlling a wireless communication apparatus including an antenna that radiates a read radio wave to a radio tag and receives a response radio wave from the radio tag with respect to the read radio wave,
Read radio waves that cause a fixed tag, which is a wireless tag fixed in the communication area of the antenna, and a monitoring tag, which is a wireless tag attached to an object to be monitored, to respond in the same time slot are radiated from the antenna. A radiation step;
A reception step of processing the response radio wave received by the antenna with respect to the read radio wave radiated in this radiation step and demodulating it into predetermined data;
Based on the data demodulated in this receiving step, a determination step of determining whether or not the response radio wave from the fixed tag and the response radio wave from the monitoring tag collide,
When it is determined that the response radio wave from the fixed tag and the response radio wave from the monitoring tag have collided in this determination step, a notification step for notifying that effect;
A method for controlling a wireless communication apparatus, comprising:

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