Wireless tag system

A configuration that achieves stable wireless communication. In this configuration, electrical power according to transmission waves is reliably supplied to a wireless tag serving as a target of wireless communication. A first wireless communication device and a second wireless communication device are provided. Both the wireless communication devices substantially simultaneously transmit transmission waves on different channels separated from each other by a predetermined frequency or more on a frequency band in the frequency axis, when performing wireless communication processing to wirelessly communicate with a wireless tag in a predetermined communication area.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims the benefit of priority from earlier Japanese Patent Applications No. 2018-210438 filed on Nov. 8, 2018 and No. 2019-194512 filed on Oct. 25, 2019 the descriptions of which are incorporated herein by reference.

BACKGROUND

Technical Field

The present invention relates to a wireless tag system including a wireless communication device whose wireless communication target is a wireless tag present in a predetermined communication area such as a defined space.

RELATED ART

Background Art

Wireless tags present (or placed) in a predetermined defined communication area, such as in a box for storing articles, have often been read through wireless communication, and the frequency of reading wireless tags in this way has been increased. When performing reading in this way, there may be produced a range in which radio waves cannot be received (a null range) due to reflection or the like of radio waves, depending on the surrounding environment. In such a situation, if a wireless tag is arranged in this null range, stable communication is not necessarily performed with the wireless tag. This is because the wireless tag present in the null range cannot sufficiently receive transmission waves from the wireless communication device, and thus the electrical power required for operation as a wireless tag cannot be obtained.

As a technique for solving this issue, for example, there is known a tag communication device as disclosed in PTL 1 below. This tag communication device is provided with two antennas, and the phase of radio waves transmitted from each antenna is changed at a predetermined cycle so as not to fix the position of the communication-disabled region (null range) and to thereby prevent RFID tags from being disabled in communication.

CITATION LIST

Patent Literature

However, in the configuration in which the phases of the radio waves transmitted from the two antennas are changed at a predetermined cycle as described above, there is an issue of not only increasing the manufacturing cost due to the need of a dedicated transmission circuit or the like, but also limiting the sites of placing the antennas.

SUMMARY

Thus it is desired to provide a configuration capable of realizing stable wireless communication by reliably supplying electrical power according to transmission waves to a wireless tag as a target of wireless communication, while minimizing an increase in manufacturing cost as much as possible and avoiding restrictions on the sites of arranging antennas for use in electrical power supply as much as possible.

To achieve the above aim, according to a first exemplary embodiment, there is provided a wireless tag system (10) including two or more wireless communication devices (30,40) including a wireless tag (T, T1to T3) as a target of wireless communication in a predetermined communication area (S). In the system, the two or more wireless communication devices simultaneously transmit transmission waves for a predetermined period of time or more on different channels which are separated from each other by a predetermined channel number or more, when performing wireless communication processing to wirelessly communicate with the wireless tag.

It should be noted that the bracketed reference signs indicate correspondence to the specific means in the embodiments described later.

In the first exemplary embodiment, the two or more wireless communication devices simultaneously transmit transmission waves on different channels separated from each other by a predetermined frequency or more on a frequency band, when performing wireless communication processing to wirelessly communicate with the wireless tag in the predetermined communication area. Thus, transmission waves from a plurality of wireless communication devices are received by one wireless tag, and the electrical power required for the operation of the wireless tag can be easily obtained. Therefore, electrical power according to the transmission waves can be reliably supplied to the wireless tag as a target of communication, and consequently, stable wireless communication can be achieved.

In a second exemplary embodiment, at least some of the two or more wireless communication devices transmit unmodulated waves as the transmission waves to the wireless tag to supply electrical power. Since unmodulated waves have a higher electrical power density than modulated waves modulated to carry signals, electrical power according to the transmission waves (unmodulated waves) can be more reliably supplied to the wireless tag as a target of communication. Accordingly, even more stable wireless communication can be achieved.

In a third exemplary embodiment, any one of the two or more wireless communication devices supplies a transmission instruction related to transmission of the transmission waves to the rest of the wireless communication devices at every time point of transmitting the transmission waves; and the rest of the wireless communication devices perform the wireless communication processing according to the transmission instruction received. Thus, channels and transmission times of the wireless communication devices can be easily controlled. In particular, there is no need to use higher-level devices that control the wireless communication devices. In addition to that, even if a specific channel becomes unavailable, the wireless communication devices can be controlled so as to avoid that channel.

In a fourth exemplary embodiment, any one of the two or more wireless communication devices transmits a control table, in which at least channels and transmission times of the transmission waves are time-scheduled, to the rest of the wireless communication devices; and the rest of the wireless communication devices perform wireless communication processing according to the control table received. Thus, channels and transmission times of the wireless communication devices can be easily controlled. In particular, there is no need to use higher-level devices that control the wireless communication devices. In addition, there is no need to communicate with other wireless communication devices every time transmission waves are transmitted. Accordingly, frequency of communication between devices can be reduced.

In a fifth exemplary embodiment, at least some of the two or more wireless communication devices include a detection unit that detects a transmission status of the transmission waves from the rest of the wireless communication devices, and simultaneously transmit the transmission waves according to detection results derived from the detection unit, for a predetermined period of time or more on a channel different and separated from channels of the rest of the wireless communication devices by a predetermined frequency or more, when performing the wireless communication processing. Thus, channels and transmission times of the wireless communication devices can be easily controlled. In particular, there is no need to use higher-level devices that control the wireless communication devices. In addition to that, there is no need to use a wireless communication device that serves as a master unit for controlling other wireless communication devices. Therefore, even if one of the wireless communication devices fails, disabling transmission of transmission waves, stable wireless communication can be continued.

In a sixth exemplary embodiment, the system includes a control device that provides a transmission instruction related to transmission of the transmission waves to the two or more wireless communication devices; and the two or more wireless communication devices perform the wireless communication processing according to the transmission instruction received from the control device. Thus, the control device can collectively perform control related to transmission of transmission waves of all the wireless communication devices. In particular, even in a situation where a specific channel cannot be used, the wireless communication devices can be controlled so as to avoid the specific channel in question.

In a seventh exemplary embodiment, the system includes a control device that transmits a control table, in which at least channels and transmission times of the transmission waves are time-scheduled, to the two or more wireless communication devices; and the two or more wireless communication devices perform the wireless communication processing according to the control table received from the control device. Thus, the control device can collectively perform control related to transmission of transmission waves to all the wireless communication devices. In particular, since there is no need to communicate with the control device every time transmission waves are transmitted, frequency of communication with the control device can be reduced.

In an eighth exemplary embodiment, there are provided an outer box and an inner box, the outer box disabling passage of radio waves except through an opening, and the inner box being held in the outer box via the opening and enabling passage of radio waves. The predetermined communication area is configured by an internal space defined by the inner box that is held in the outer box. An antenna of the first wireless communication device and an antenna of the second wireless communication device are each arranged between an inner surface of the outer box and an outer surface of the inner box.

Thus, leakage of transmission waves from the outer box (casing) to the outside is minimized, so that electrical power can be reliably supplied to the wireless tag arranged in the internal space of the inner box as a predetermined communication area. In particular, in the vicinity of the inner surface of the outer box, a null region is likely to occur due to reflection of radio waves on the inner surface; however, since the internal space of the inner box held in the outer box serves as a predetermined communication area, the wireless tag in the internal space (predetermined communication area) of the inner box can be away from the vicinity of the inner surface of the outer box. Therefore, electrical power can be reliably supplied to the wireless tag in the internal space of the inner box.

In a ninth exemplary embodiment, the antenna of the first wireless communication device is arranged between an inner bottom surface of the outer box and an outer surface of the inner box, and the antenna of the second wireless communication device is arranged between any one of the four inner side surfaces and an outer surface of the inner box. Thus, the output direction of the transmission waves transmitted from the antenna of the first wireless communication device becomes substantially orthogonal to the output direction of the transmission waves transmitted from the antenna of the second wireless communication device. Accordingly, electrical power can be reliably supplied to the wireless tag regardless of the orientation of the wireless tag in the internal space of the inner box.

In a tenth exemplary embodiment, the antenna of the second wireless communication device is arranged being inclined with respect to the inner side surface so that an output direction of the transmission waves is away from the opening. Thus, the transmission waves transmitted from the antenna are less likely to leak from the opening as compared with the case where the antenna of the second wireless communication device is inclined with respect to the inner side surface in a direction in which the output direction of the transmission waves approaches the opening. Accordingly, erroneous reading of a wireless tag located outside the predetermined communication area can be minimized.

In an eleventh exemplary embodiment, four antennas are respectively arranged between inner surfaces of the outer box and outer surfaces of the inner box so that a first antenna of the first wireless communication device faces a first antenna of the second wireless communication device and a second antenna of the first wireless communication device faces a second antenna of the second wireless communication device. The first wireless communication device and the second wireless communication device simultaneously perform the wireless communication processing for a predetermined period of time or more on different channels which separate transmission waves transmitted from the first antenna of the first wireless communication device from transmission waves transmitted from the first antenna of the second wireless communication device by a predetermined frequency or more, or also simultaneously perform the wireless communication processing for a predetermined period of time or more on different channels which separate transmission waves transmitted from the second antenna of the first wireless communication device from transmission waves transmitted from the second antenna of the second wireless communication device by a predetermined frequency or more.

Thus, there can be provided a time when electrical power is supplied to the wireless tag in the internal space of the inner box (in the predetermined communication area) with the transmission waves transmitted from the first antenna of the first wireless communication device and the transmission waves transmitted from the first antenna of the second wireless communication device, and a time when electrical power is supplied to the wireless tag with the transmission waves transmitted from the second antenna of the first wireless communication device and the transmission waves transmitted from the second antenna of the second wireless communication device. In particular, since transmission waves are simultaneously transmitted from both antennas facing each other for a predetermined period of time or more, the radio waves can be easily mutually intensified and electrical power supplied to the wireless tag can be increased. Therefore, even if the radio wave intensity of the transmission waves is lowered for the purpose of minimizing erroneous reading of wireless tags located outside the predetermined communication area, electrical power can be reliably supplied to the wireless tag which is a target of wireless communication, according to the transmission waves.

In a twelfth exemplary embodiment, four antennas are respectively arranged between inner surfaces of the outer box and outer surfaces of the inner box so that a first antenna and a second antenna of the first wireless communication face each other, and a first antenna and a second antenna of the second wireless communication face each other. The first wireless communication device and the second wireless communication device simultaneously perform the wireless communication processing for a predetermined period of time or more on different channels at which separate transmission waves are transmitted from the first antenna of the first wireless communication device and from the first antenna of the second wireless communication device, the different channel being separate from each other by a predetermined channel number (or frequency) or more, or also simultaneously perform the wireless communication processing for a predetermined period of time or more on different channels at which separate transmission waves are transmitted from the second antenna of the first wireless communication device and from the second antenna of the second wireless communication device, the different channel being separate from each other by a predetermined channel number (or frequency) or more.

Thus, there can be provided a time when electrical power is supplied to the wireless tag in the internal space of the inner box (in the predetermined communication area) with the transmission waves transmitted from the first antenna of the first wireless communication device and the transmission waves transmitted from the first antenna of the second wireless communication device, and a time when electrical power is supplied to the wireless tag with the transmission waves transmitted from the second antenna of the first wireless communication device and the transmission waves transmitted from the second antenna of the second wireless communication device. Therefore, even if the radio wave intensity of the transmission waves is lowered for the purpose of minimizing erroneous reading of wireless tags located outside the predetermined communication area, electrical power can be reliably supplied to the wireless tag as a target of wireless communication, according to the transmission waves.

In a thirteenth exemplary embodiment, the two or more wireless communication devices include a third wireless communication device in addition to the first wireless communication device and the second wireless communication device. The present wireless tag system includes a reading unit that reads information from the wireless tag in the predetermined communication area as an internal space defined by the inner box, using wireless communication results derived from the first wireless communication device, the second wireless communication device, and the third wireless communication device. An antenna of the third wireless communication device is arranged outside the outer box.

Thus, the wireless tag can read not only by the first wireless communication device and the second wireless communication device but also by the third wireless communication device which can be determined to be a wireless tag having a high probability of being located outside the predetermined communication area. Thus, erroneous reading of wireless tags located outside the predetermined communication area can be minimized.

In a fourteenth exemplary embodiment, the antenna of the third wireless communication device is arranged outside the outer box so as to be located around the opening. Thus, the third wireless communication device can easily read the wireless tag located on the surface around the opening which is outside the predetermined communication area, compared to the first wireless communication device and the second wireless communication device. This can minimize erroneous reading due to the first wireless communication device or the second wireless communication device reading the wireless tag located on the surface around the opening.

In a fifteenth exemplary embodiment, the antenna of the third wireless communication device is arranged being inclined with respect to a plane provided by the opening so that an output direction of transmission waves is away from the opening. Thus, the third wireless communication device is less likely to read the wireless tag located in the predetermined communication area, minimizing erroneous reading due to the reading performed by the third wireless communication device.

In a sixteenth exemplary embodiment, the reading unit reads information from the wireless tag in the predetermined communication area as an internal space defined by the inner box, using received signal strength (RSSI) as a result of wireless communication of the first wireless communication device, the second wireless communication device, and the third wireless communication device. In the first wireless communication device or the second wireless communication device, the received signal strength when reading the wireless tag in the predetermined communication area is higher than the received signal strength when reading the wireless tag outside the predetermined communication area. In the third wireless communication device, the received signal strength when reading a wireless tag outside the predetermined communication area is arranged to be higher than the received signal strength when reading the wireless tag in the predetermined communication area. Therefore, even if wireless tags are read by all the wireless communication devices, the wireless tag whose received signal strength is higher in the first wireless communication device or the second wireless communication device is determined to be a wireless tag in the predetermined communication area, and the wireless tag whose received signal strength is higher in the third wireless communication device is determined to be a wireless tag outside the predetermined communication area. Thus, an accurate determination can be made as to whether the read wireless tag is in the predetermined communication area.

In a sixteenth exemplary embodiment, wireless communication of the first wireless communication device and the second wireless communication device, and wireless communication of the third wireless communication device are mutually exclusively performed. Thus, the electric power obtained by the wireless tag according to the transmission waves from the first wireless communication device or the second wireless communication device is not used during wireless communication with the third wireless communication device. Accordingly, since measurement accuracy of the received signal strength obtained during wireless communication of the third wireless communication device is enhanced, a more accurate determination can be made as to whether the read wireless tag is in the predetermined communication area.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

A first embodiment of a wireless tag system according to the present invention will be described with reference to the drawings.

A wireless tag system10according to the present embodiment is configured as a system including two or more wireless communication devices having one or two or more wireless tags as targets of wireless communication arranged in a predetermined communication area S defined such as by a box (casing) for storing products. Specifically, as shown inFIG.1, the wireless tag system10includes a storage box (casing)20for defining the predetermined communication area S, two wireless communication devices (also termed a first wireless communication device30and a second wireless communication device40hereinafter), and a control device50that manages both wireless communication devices.

The wireless tag system10is arranged in the vicinity of a POS register used for selling products and has a wireless tag (RFID tag) T in the storage box20as a target of wireless communication to transmit product information and other information read from the wireless tag T to the POS register and the like through wireless communication. As can be seen fromFIGS.2and3, one or two or more products with respective wireless tags T are placed in a shopping basket B held in the storage box20, so that the POS register and the like can acquire product information and other information from the wireless tag system10. It should be noted thatFIGS.2and3show a state in which a product G1with a wireless tag T1, a product G2with a wireless tag T2, and a product G3with a wireless tag T3are placed in the shopping basket B.

First, referring to the drawings, the storage box20will be described in detail.

Since the storage box20is formed in a box shape as a whole, it has a vertical direction, and has a lateral direction and a depth direction (or a longitudinal direction) which are both orthogonal to the vertical direction. The lateral direction and the depth direction (longitudinal direction) are reversed depending on the direction in which the storage box20is viewed.

The storage box20includes an outer box (casing)21, an inner box22, and a top plate23. The outer box21is made of a material, e.g., a metal plate, that blocks radio waves to disable passage therethrough. The outer box21has an opening21aon top in the vertical direction, and has inner surfaces, i.e., a rectangular inner bottom surface21bfacing the opening21a, and four inner side surfaces21cto21frespectively connected to four sides of the inner bottom surface21b. The inner side surfaces21cto21fdefine the opening21aat the upper edges thereof in a state where the inner side surfaces21cand21eface each other and the inner side surfaces21dand21fface each other.

The inner box22is a box opened on top to hold the shopping basket B inserted from above in the vertical direction, that is, a box defining an internal space for holding the shopping basket B to serve as the predetermined communication area S mentioned above. The inner box22is made of a material, e.g., a synthetic resin, enabling radio waves to pass therethrough. The inner box22is configured to have an opening22aon top through which the shopping basket B can be inserted, and to have outer surfaces, i.e., a rectangular outer bottom surface22band four outer surfaces22cto22frespectively connected to four sides of the outer bottom surface22b. The outer surfaces22cto22fdefine the opening22aat the upper edges thereof. The inner box22configured in this way is held in the outer box21via a predetermined gap. Specifically, the inner box22is formed so that, when it is held, the opening22ais substantially flush with the opening21a, and the outer bottom surface22bfaces the inner bottom surface21, while the outer side surfaces22cto22fface the respective inner side surfaces21cto21f.

The top plate23is made of a material, e.g., a metal plate, that blocks radio waves to disable passage therethrough. The top plate23has outer edges, which are larger than those of the opening21aof the outer box21, and define an opening23anear the center so as to have substantially the same rectangular shape as the opening22aof the inner box22. Thus, the top plate23is assembled to the outer box21and the inner box22held in the outer box21so as to close the gap between the outer and inner boxes21and22(the square annular gap around the inner box22as viewed perpendicularly from above).

Next, with reference to the drawings, the first wireless communication device30and the second wireless communication device40will be described in detail.

The first wireless communication device30includes a first control unit31and an antenna32. The first control unit31is configured to include a circuit or the like that performs transmission using a known radio wave method in response to an instruction or the like from the control device50. The first control unit31includes an oscillator, a modulator, an amplifier, and a demodulator, and is connected to the antenna32via the cable33. For example, the first control unit31is configured to allow the modulator to modulate the oscillation signal generated by the oscillator, and output the modulated waves as transmission waves (transmission radio waves) via the antenna32. When radio waves are received from a wireless tag T via the antenna32, the first control unit31is configured to allow the demodulator to demodulate the radio waves to thereby acquire the product information and other information recorded on the wireless tag T.

The second wireless communication device40includes a second control unit41and an antenna42, which have the same functions as those of the first control unit31and the antenna32described above, and also includes a cable43connecting between the second control unit41and the antenna42. The second wireless communication device40is configured as a wireless communication device having functions equivalent to those of the first wireless communication device30to operate in response to an instruction or the like from the control device50.

The antenna32of the first wireless communication device30configured in this way is arranged between the inner bottom surface21band the outer bottom surface22b, so that the transmission direction of the transmission waves (see the arrow F1ofFIG.2) is orthogonal to the outer bottom surface22bin the vicinity of the center of the inner bottom surface21b. The antenna42of the second wireless communication device40is arranged between the inner side surface21cand the outer side surface22c, so that the transmission direction of the transmission waves (see the arrow F2ofFIG.2) is orthogonal to the outer side surface22cin the vicinity of the center of the inner side surface21c. Specifically, the antenna32of the first wireless communication device30and the antenna42of the second wireless communication device40are arranged so that the transmission directions of the transmission waves are orthogonal to each other.

With such an arrangement configuration or the like, stable wireless communication can be realized with respect to the wireless tags T in the predetermined communication area S that is an internal space defined by the inner box22, and the reading success rate for the wireless tags T can be enhanced. The reason for this is as follows. Specifically, in the vicinity of the inner surfaces of the outer box21, a null range is likely to occur due to the reflection of radio waves on the inner surfaces. However, since the inside of the inner box22held in the outer box21serves as the predetermined communication area S, the wireless tags T in the inner box22(in the predetermined communication area S) can be away from the vicinity of the inner surfaces of the outer box21in which the null range is likely to occur. In addition, the reason for this is that the top plate23can minimize leakage of the transmission waves to the outside via the opening21aof the outer box21.

The control device50is mainly configured by a microcomputer as an example. Specifically, the control device50includes a CPU (central processing unit)50A performing calculation, and a main memory50B as a work area, and also includes a system bus and an input/output interface, both of which are not shown, to configure a microcomputer together with a memory51C. As will be described later, the CPU50A controls operation of the control units.

In the memory51C (including RAM (read only memory)51Ca and ROM (random access memory)51Cb), a predetermined program or the like for the control is stored in advance so as to be executed by the CPU50A. Therefore, the memory51C functions as a non-transitory computer-readable recording medium, and the procedure of the program related to predetermined control processing is stored as a source code.

The program is read into the main memory50B by the CPU50A and executed. The main memory50B is configured to be readable and writable using a memory element such as RAM. The CPU50A is an element that plays a central role in the calculation performed in the computer system, and may have a different name (e.g., a processor or an arithmetic unit), as a matter of course, as long as it has the same functions. The control processing may be readably stored in an external storage device.

The control processing executed by the control device50(i.e., the CPU50A) will be described later.

Next, the processing performed by the first and second wireless communication devices30and40will be described with reference to the drawings. This processing is performed under the control of the control device50(i.e., the CPU50A) when reading a wireless tag T in the shopping basket B inserted in the storage box20.

When the shopping basket B is inserted in the storage box20, the control device50instructs the first and second wireless communication devices30and40to start wireless communication processing (transmission instructions related to transmission of transmission waves) at predetermined intervals for a predetermined time (steps S11to S13ofFIG.15).

Specifically, the control device50outputs a transmission instruction for transmitting transmission waves on the channel23(23CH: 920.4 MHz) for a predetermined period of time or more to the first wireless communication device30, while outputting a transmission instruction for transmitting transmission waves for a predetermined period of time or more to the second wireless communication device40on the channel32(32CH: 922 MHz) that does not interfere the channel23(step S11ofFIG.15).

In particular, the control device50simultaneously gives transmission instructions to the first and second wireless communication devices30and40. In the present embodiment, the frequency between the channels23and32will be referred to as “constant frequencies (or specific frequencies)” that determine the width of separation between these channels on the frequency band (or o (n the frequency axis).

The control device50may automatically give the above transmission instructions by detecting the state in which the shopping basket B is inserted in the storage box20, using a sensor or the like provided to the storage box20, or according to a predetermined operation or the like after insertion of the car B in the storage box20(steps S10to S13ofFIG.16).

In response to the transmission instructions from the control device50, the first and second wireless communication devices30and40substantially simultaneously perform wireless communication processing to wirelessly communicate with the wireless tags T in the predetermined communication area S. Therefore, the first and second wireless communication devices30and40substantially simultaneously transmit transmission waves on different channels separated from each other by a predetermined channel number (or frequency) or more for a predetermined period of time or more.

Referring toFIG.4, the reason why transmission waves are substantially simultaneously transmitted on different channels will be described.FIG.4is a diagram illustrating electrical power obtained by a wireless tag T when receiving transmission waves transmitted substantially simultaneously on different channels. The vertical axis represents the electrical power obtained by the wireless tag T, and the horizontal axis represents the frequency of the transmission waves.

Wireless tags T receive transmission waves from the wireless communication devices to obtain electrical power required for operation as wireless tags. Therefore, if transmission waves are simply transmitted from the first wireless communication device30, the wireless tag T as a target of wireless communication does not necessarily obtain required electrical power from the transmission waves due to the influence of the null range, or interference of radio waves, or the like. Similarly, if transmission waves are simply transmitted from the second wireless communication device40, the wireless tag T as a target of wireless communication does not necessarily obtain required electrical power from the transmission waves.

In this regard, if transmission waves are substantially simultaneously transmitted from the first and second wireless communication devices30and40on different channels, the wireless tag T can receive both of the transmission waves substantially simultaneously because the frequency bandwidth of the wireless tag T is wide. That is, as shown inFIG.4, the electrical power supply due to reception of transmission waves from the first wireless communication device30(see reference sign P1ofFIG.4) and the electrical power supply due to reception of transmission waves from the second wireless communication device40(see reference sign P2inFIG.4) are conducted substantially simultaneously. Therefore, the wireless tag T can reliably obtain electrical power required for the operation as a wireless tag. In this case, the wireless tag T sends a reply to the wireless communication device, from which stronger transmission waves have been received, so that necessary data and other data can be transmitted.

As described above, in the wireless tag system10according to the present embodiment, the first and second wireless communication devices30and40perform wireless communication processing to wirelessly communicate with a wireless tag T in the predetermined communication area S. When performing this processing, transmission waves are substantially simultaneously transmitted (simultaneously for a predetermined period of time or more) on different channels separated from each other by a predetermined channel number (or frequency) or more.

Thus, one wireless tag T should receive transmission waves from the first and second wireless communication devices30and40, and electrical power required for the operation of the wireless tag can be easily obtained. Therefore, electrical power according to the transmission waves can be reliably supplied to the wireless tag T as a target of wireless communication. Consequently, stable wireless communication can be achieved.

In particular, the wireless tag system10includes the control device50that gives transmission instructions regarding transmission of transmission waves to the first and second wireless communication devices30and40, which perform wireless communication processing, in turn, in response to the transmission instructions received from the control device50. Thus, the control device50can collectively control transmission of transmission waves sent from the first and second wireless communication devices30and40. In particular, even when a specific channel becomes unavailable, the control device50can keep track of the unusable state to control the first and second wireless communication devices30and40, avoiding the specific channel in question.

Furthermore, the wireless tag system10according to the present embodiment includes the outer box21disabling passage of radio waves therethrough except for the opening21a, and the inner box22allowing passage of radio waves therethrough and held in the outer box21via the opening21a, with the predetermined communication area S as an internal space defined by the inner box22held in the outer box21. The antenna32of the first wireless communication device30and the antenna42of the second wireless communication device40are arranged between the inner surface of the outer box21and the outer surface of the inner box22.

Therefore, transmission waves are prevented from being leaked from the outer box21to the outside. Accordingly, electrical power can be reliably supplied to the wireless tags T arranged in the internal space of the inner box22as the predetermined communication area S. In particular, in the vicinity of the inner surface of the outer box21, a null range is likely to occur due to reflection of radio waves on the inner surface; however, since the internal space of the inner box held in the outer box21serves as the predetermined communication area S, the wireless tags T in the internal space (in the predetermined communication area) of the inner box22can be away from the vicinity of the inner surface of the outer box where a null range is likely to occur. Therefore, electrical power can be reliably supplied to the wireless tags T in the internal space of the inner box22.

In particular, the antenna32of the first wireless communication device30is arranged between the inner bottom surface21bof the outer box21and the outer bottom surface22bof the inner box22, while the antenna42of the second wireless communication device40is arranged between the inner side surface21cof the outer box21and the outer side surface22cof the inner box22. Accordingly, the output direction of the transmission waves transmitted from the antenna32of the first wireless communication device30is substantially orthogonal to the output direction of the transmission waves transmitted from the antenna42of the second wireless communication device40. Thus, electrical power can be reliably supplied to the wireless tags T regardless of the orientations of the wireless tags T in the internal space of the inner box22.

The antenna42of the second wireless communication device40does not necessarily have to be arranged between the inner side surface21cof the outer box21and the outer side surface22cof the inner box22, but may be arranged between the inner side surface21dof the outer box21and the outer side surface22dof the inner box22, or between the inner side surface21eof the outer box21and the outer side surface22eof the inner box22, or between the inner side surface21fof the outer box21and the outer side surface22fof the inner box22. Furthermore, the antenna32of the first wireless communication device30does not necessarily have to be arranged between the inner bottom surface21bof the outer box21and the outer bottom surface22bof the inner box22, but may be arranged between an inner side surface of the outer box21and an outer side surface of the inner box22so as to face the antenna42, or may be arranged between an inner side surface of the outer box21and an outer side surface of the inner box22so that the output direction of the transmission waves is orthogonal to the antenna42.

Second Embodiment

Next, a wireless tag system according to a second embodiment of the present invention will be described with reference to the drawings.

The second embodiment is mainly different from the first embodiment in that unmodulated waves are transmitted as transmission waves from one wireless communication device. Therefore, like reference signs are given to like components of the first embodiment to omit duplicate description.

Transmission waves transmitted to wirelessly communicate with a wireless tag T are modulated to carry signals from the viewpoint of electrical power supply, this may lower the supply efficiency for unmodulated waves. In this regard, in the present embodiment, one wireless communication device may transmit transmission waves modulated for wireless communication, and the other wireless communication device may transmit unmodulated waves as transmission waves for supplying electrical power to the wireless tag T to thereby easily enhance the power supply efficiency.

This is because unmodulated waves have a higher electrical power density than modulated waves that are modulated to carry signal waves, and thus because electrical power can be more reliably supplied to the wireless tag T as a target of communication according to the unmodulated wave, and even more stable wireless communication can be achieved.

In the present embodiment, the second wireless communication device40is configured to transmit unmodulated waves. Therefore, as can be seen fromFIG.5, the wireless tag T can receive electrical power supply due to reception of modulated transmission waves from the first wireless communication device30(see reference sign P1ofFIG.5), and electrical power supply due to reception of unmodulated waves from the second wireless communication device40(see reference sign P2ofFIG.5).

The wireless communication device transmitting unmodulated waves does not necessarily have to be the second wireless communication device40, but may be the first wireless communication device30.

Third Embodiment

Next, a wireless tag system according to a third embodiment of the present invention will be described with reference to the drawings.

The third embodiment is mainly different from the first embodiment in that the first wireless communication device30is configured as a master unit and the second wireless communication device40is configured as a slave unit. Therefore, like reference signs are given to like components of the first embodiment to omit duplicate description.

In the present embodiment, as shown inFIG.6, the first wireless communication device30is configured as a master unit and the second wireless communication device40is configured as a slave unit, so that a transmission instruction mentioned above can be supplied from the first wireless communication device30to the second wireless communication device40. In other words, a transmission instruction is supplied from the control device50to the first wireless communication device30. Thus, the first wireless communication device30gives a transmission instruction to the second wireless communication device40at each transmission time point of transmitting transmission waves, and the second wireless communication device40performs wireless communication processing in response to the transmission instruction received. In the present embodiment, the control device50is configured to collectively receive data acquired through the wireless communication processing of the first and second wireless communication devices30and40and other data, from the first wireless communication device30.

Even in this way, channels and transmission times in the first and second wireless communication devices30and40can be easily controlled. In particular, there is no need to use higher-level devices respectively controlling the first and second wireless communication device30and40. In addition to that, even in a situation where a specific channel cannot be used, the first and second wireless communication devices30and40can be controlled so as to avoid the specific channel in question by allowing the first wireless communication device30to keep track of the situation.

As a first modification of the third embodiment, it may be so configured that, under the transmission control of the control device50, the first wireless communication device30transmits a control table, in which at least channels and transmission times of transmission waves are time-scheduled, to the second wireless communication device40, and the second wireless communication device40performs wireless communication processing according to the control table received. Even in this way, channels and transmission times of the first and second wireless communication devices30and40can be easily controlled. In particular, there is no need to use higher-level devices respectively controlling the first and second wireless communication devices30and40. In addition to that, the first and second wireless communication devices30and40are not required to communicate with each other every time transmission waves are transmitted. Accordingly, frequency of communication between the devices can be reduced.

The characteristic configuration according to the first modification of the third embodiment may be applied to the first embodiment. Specifically, as a first modification of the first embodiment, it may be configured so that the control device50transmits a control table, in which at least channels and transmission times of transmission waves are time-scheduled, to the first and second wireless communication devices30and40, and the first and second wireless communication devices30and40perform wireless communication processing according to the control table received from the control device50. Thus, the first and second wireless communication devices30and40do not need to communicate with the control device50every time the transmission waves are transmitted. Accordingly, frequency of communication with the control device50can be reduced.

It should be noted that the second wireless communication device40may be a master unit, and the first wireless communication device30may be a slave unit. The characteristic configurations of the present embodiment and the modification in which one of the wireless communication devices is a master unit and the rest are slave units can be applied to other embodiments and the like.

Fourth Embodiment

Next, a wireless tag system according to a fourth embodiment of the present invention will be described with reference to the drawings.

The fourth embodiment is mainly different from the first embodiment in that the first wireless communication device30detects a transmission status of transmission waves in the second wireless communication device40and performs wireless communication processing according to the detection results. Therefore, like reference signs are given to like components of the first embodiment to omit duplicate description.

In the present embodiment, the first control unit31of the first wireless communication device30is configured to be able to detect a transmission status, such as the channel used for transmission waves, in the second wireless communication device40according to the detection results derived from a detection unit. This detection unit detects the transmission status by receiving and analyzing transmission waves transmitted from the second wireless communication device40. Then, when performing wireless communication processing, the first wireless communication device30simultaneously transmits transmission waves for a predetermined period of time on a channel different and separated from the channel of the second wireless communication device40by a predetermined channel number or more on the frequency band, according to the detection results derived from the detection unit.

Even in this way, channels and transmission times of the first and second wireless communication devices30and40can be easily controlled. In particular, there is no need to use higher-level devices that respectively control the first and second wireless communication devices30and40. In addition to that, there is also no need to use the wireless communication device that serves as a master unit for controlling other wireless communication devices. As will be described later, when three or more wireless communication devices are adopted, at least some of the wireless communication devices may be provided with the detection unit mentioned above, so that stable wireless communication can be continued in the occurrence of a failure disabling transmission of transmission waves in one of the wireless communication devices.

Fifth Embodiment

Next, a wireless tag system according to a fifth embodiment of the present invention will be described with reference to the drawings.

The fifth embodiment is mainly different from the first embodiment in that the antenna arranged between an inner side surface of the outer box21and an outer side surface of the inner box22is inclined. Therefore, like reference signs are given to like components of the first embodiment to omit duplicate description.

Since the storage box20is provided with an opening23afor inserting the shopping basket B therethrough, radio waves (transmission waves) may leak from the opening23a. In particular, if transmission waves leak from the opening23apassing over the top plate23, for example, the wireless tag affixed to a product handled by the adjacent POS register (the wireless tag that is not the target of wireless communication) may be erroneously read.

In this regard, in the present embodiment, the antenna42of the second wireless communication device40is arranged so as to incline with respect to the inner side surface in a direction in which the output direction of the transmission waves is away from the opening23a. Specifically, as shown inFIG.7, the antenna42is arranged being inclined downward with respect to the inner side surface21cso that the output direction of the transmission waves (see the arrow F2ofFIG.7) is away from the opening23a.

Thus, compared to the case where the antenna42of the second wireless communication device40is inclined with respect to the inner side surface in the direction in which the output direction of the transmission waves approaches the opening23a, transmission waves transmitted from the antenna42are less likely to leak from the opening23apassing over the top plate23, to thereby minimize erroneous reading of a wireless tag located outside the predetermined communication area S.

The characteristic configuration of the present embodiment in which the antenna arranged between an inner side surface of the outer box21and an outer side surface of the inner box22is inclined can be applied to other embodiments and the like.

Sixth Embodiment

Next, a wireless tag system according to a sixth embodiment of the present invention will be described with reference to the drawings.

The sixth embodiment is mainly different from the first embodiment in that antennas are arranged on both lateral sides and both depth direction sides (both longitudinal sides) in the predetermined communication area S. Therefore, like reference signs are given to like components of the first embodiment to omit duplicate description.

In the present embodiment, as shown inFIGS.8and9, it is so configured that the first wireless communication device30includes two antennas32aand32b, and the second wireless communication device40includes two antennas42aand42b.

Specifically, the antenna32ais arranged between the inner side surface21eand the outer side surface22eso that the transmission direction of the transmission waves is orthogonal to the outer side surface22ein the vicinity of the center of the inner side surface21e. The antenna32bis arranged between the inner side surface21dand the outer side surface22dso that the transmission direction of the transmission waves is orthogonal to the outer side surface22din the vicinity of the center of the inner side surface21d. The antenna42ais arranged between the inner side surface21cand the outer side surface22cso that the transmission direction of the transmission waves is orthogonal to the outer side surface22cin the vicinity of the center of the inner side surface21c. The antenna42bis arranged between the inner side surface21fand the outer side surface22fso that the transmission direction of the transmission waves is orthogonal to the outer side surface22fin the vicinity of the center of the inner side surface21f.

Specifically, the four antennas are respectively arranged between the inner side surfaces of the outer box21and the outer side surfaces of the inner box22so that the antennas32aand42aface each other in the lateral direction and the antennas32band42bface each other in the depth direction. It should be noted that the antenna32amay correspond to an example of “the first antenna of the first wireless communication device”, and the antenna32bmay correspond to an example of “the second antenna of the first wireless communication device”. Furthermore, the antenna42amay correspond to an example of “the first antenna of the second wireless communication device”, and the antenna42bmay correspond to an example of “the second antenna of the second wireless communication device”.

Then, for the first and second wireless communication devices30and40, the control device50alternates, at predetermined intervals, processing of simultaneously giving a transmission instruction using the antenna32aand a transmission instruction using the antenna42a, and processing of simultaneously giving a transmission instruction using the antenna32band a transmission instruction using the antenna42b.

The first and second wireless communication devices30and40simultaneously perform wireless communication processing for a predetermined period of time or more on different channels which separate the transmission waves transmitted from the antenna32afrom the transmission waves transmitted from the antenna42aby a predetermined frequency or more, and also perform wireless communication processing for a predetermined period of time or more on different channels which separate the transmission waves transmitted from the antenna32bfrom the transmission waves transmitted from the antenna42bby a predetermined frequency or more.

Thus, for the wireless tags T in the predetermined communication area S that is the internal space defined by the inner box22, there can be repeatedly provided a time when electrical power is supplied with transmission waves transmitted from the antennas32aand42a, and a time when electrical power is supplied with transmission waves transmitted from the antennas32band42b. In particular, since transmission waves are simultaneously transmitted from the two antennas facing each other for a predetermined period of time or more, radio waves can be easily mutually intensified and the electrical power supply to the wireless tags T can be increased. Therefore, even if the radio wave intensity of the transmission waves is lowered for the purpose of minimizing erroneous reading of wireless tags T located outside the predetermined communication area S, electrical power corresponding to the transmission waves can be reliably supplied to the wireless tag T as a target of wireless communication.

As a modification of the present embodiment, as shown inFIG.10, the four antennas may be respectively arranged between the inner side surfaces of the outer box21and the outer side surfaces of the inner box22such that the antennas32aand32bface each other and the antennas42aand42bface each other. Even in this way, for the wireless tags T in the predetermined communication area S that is the internal space defined by the inner box22, there can be repeatedly provided a time when electrical power is supplied with the transmission waves transmitted from the antennas32aand42a, and a time when electrical power is supplied with the transmission waves transmitted from the antennas32band42b. Therefore, even if the radio wave intensity of the transmission waves is lowered for the purpose of minimizing erroneous reading of wireless tags T located outside the predetermined communication area S, electrical power corresponding to the transmission waves can be reliably supplied to the wireless tag T as a target of wireless communication.

The characteristic configurations of the present embodiment and the modification in which antennas are respectively arranged in four directions in the predetermined communication area S can be applied to other embodiments and the like.

Seventh Embodiment

Next, a wireless tag system according to a seventh embodiment of the present invention will be described with reference to the drawings.

The seventh embodiment is mainly different from the first embodiment in that a third wireless communication device60is adopted in addition to the first and second wireless communication devices30and40. Therefore, like reference signs are given to like components of the first embodiment to omit duplicate description.

In the present embodiment, as shown inFIG.12, the wireless tag system10is configured to newly include a third wireless communication device60in addition to the first and second wireless communication devices30and40. The third wireless communication device60includes a third control unit61and antennas62ato62c, which have the same functions as those of the first control unit31and the antenna32described above, and also includes a cable63connecting the third control unit61to the antennas62ato62c. The third wireless communication device60is configured as a wireless communication device having functions equivalent to those of the first wireless communication device30, and these functions are exerted according to an instruction or the like supplied from the control device50(see the transmission instruction flow ofFIG.15).

As shown inFIG.13, the antennas62ato62care arranged at positions outside the outer box21, i.e., around the opening21a, to read wireless tags T located outside the predetermined communication area S. Specifically, the antenna62ais provided on the lower surface of the top plate23on the side where the user stands to place the product with a wireless tag T in the inner box22, so that the transmission direction of the transmission waves will be upward. The antennas62band62care provided on the lower surface of the top plate23so as to face each other via the opening21a, so that the transmission directions of the transmission waves will be upward.

With the antennas62ato62cbeing arranged in this way, the third wireless communication device60can read a wireless tag (see reference sign Ta ofFIG.12) on the surface around the opening21aoutside the predetermined communication area S more easily than the first and second wireless communication devices30and40. Thus, erroneous reading can be minimized, which may be due to the wireless tag T (Ta) on the surface around the opening21abeing read by the first wireless communication device30or the second wireless communication device40.

In the present embodiment, the control device50uses received signal strength (RSSI) resulting from wireless communication of the first, second and third wireless communication device30,40and60to serve as a reading unit that reads information from a wireless tag T in the predetermined communication area S that is an internal space defined by the inner box22. Due to the antenna arrangement as described above, the first wireless communication device30or the second wireless communication device40will have a received signal strength that is higher when reading the wireless tags T (T1to T3) in the predetermined communication area S than when reading the wireless tag T (Ta) outside the predetermined communication area S, while the third wireless communication device60will have a received signal strength that is higher when reading the wireless tag T (Ta) outside the predetermined communication area S than when reading the wireless tags T (T1to T3) in the predetermined communication area S.

Therefore, even if a wireless tag T is read by all the wireless communication devices, the wireless tag T for which the first wireless communication device30or the second wireless communication device40has a higher received signal strength is determined to be a wireless tag T in the predetermined communication area S, and the wireless tag T for which the third wireless communication device60has a higher received signal strength is determined to be a wireless tag T outside the predetermined communication area S. Thus, an accurate determination can be made as to whether the read wireless tag T is on the inside of the predetermined communication area S.

In particular, by alternately repeating a time when wireless communication of the first and second wireless communication devices30and40is performed and a time when the wireless communication of the third wireless communication device60is performed, wireless communication of the first and second wireless communication devices30and40and wireless communication of the third wireless communication device60can be mutually exclusively performed. Thus, electrical power obtained by the wireless tag T according to the transmission waves from the first wireless communication device30or the second wireless communication device40will not be used during wireless communication with the third wireless communication device60. This may enhance measurement accuracy of the received signal strength obtained during wireless communication of the third wireless communication device60. Accordingly, an even more accurate determination can be made as to whether the read wireless tag T is on the inside of the predetermined communication area S.

The third wireless communication device60is not limited to have a configuration including the antennas62ato62c, but may have a configuration including one or two or more antennas which are arranged outside the outer box21so that the wireless tag T in the predetermined communication area S is less likely to be read. Even in this way, the wireless tag T that has been read not only by the first and second wireless communication devices30and40but also by the third wireless communication device60can be determined to be a wireless tag T having a high probability of being located outside the predetermined communication area S. This may minimize erroneous reading of the wireless tag T located outside the predetermined communication area S.

Specifically, for example, as in the modification of the present embodiment shown inFIG.14, the antenna62of the third wireless communication device60may be arranged being inclined with respect to a plane provided by the opening21aso that the output direction of the transmission waves will be away from the opening21a. Thus, the third wireless communication device60is less likely to read the wireless tag T in the predetermined communication area S, and thus erroneous reading due to the reading that would be performed by the third wireless communication device60can be minimized.

The characteristic configurations of the present embodiment and the modification in which the third wireless communication device60is newly adopted can be applied to other embodiments and the like.

The present invention is not limited to the above embodiments, but may be embodied as follows, for example.

(1) The predetermined communication area S is not limited to be configured by the storage box20having an opening, i.e., the opening23a, on top, but may be configured by a storage box having an opening in at least a part of another surface. For example, as shown inFIG.11, the predetermined communication area S may be configured by a storage box20athat is open from the top to a side surface as an opening24. Furthermore, the storage box is not limited to have a rectangular bottom surface, but may have, for example, a polygonal or circular bottom surface. Furthermore, the predetermined communication area S is not limited to be an internal space clearly defined by the wall surfaces or the like such as of the storage box20or20a, but may be configured by a part of a space not clearly defined by wall surfaces or the like.

(2) The present invention is not limited to be applied to the wireless tag system10having two wireless communication devices30and40, but may be applied to a wireless tag system having three or more wireless communication devices. In such a configuration, the wireless communication devices simultaneously transmit transmission waves for a predetermined period of time or more on different channels separated from each other by a predetermined channel number or more when performing wireless communication processing to wirelessly communicate with a wireless tag T in the predetermined communication area S. Even in this way, transmission waves from the plurality of wireless communication devices should be received by one wireless tag T, and electrical power required for the operation of this wireless tag can be easily obtained. Therefore, electrical power according to transmission waves can be reliably supplied to the wireless tag T as a target of wireless communication, as a result of which, stable wireless communication can be achieved.

(3) Furthermore, the present invention is not limited to be applied to a wireless tag system for selling products, but may be applied to a wireless tag system targeting wireless tags located in a predetermined communication area within a relatively narrow range.

DESCRIPTION OF REFERENCE SIGNS

30. . . First wireless communication device