JP4862018B2 - Wireless communication apparatus and wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication apparatus that performs wireless communication with a passive wireless communication medium, and a wireless communication system including a plurality of such wireless communication apparatuses.

  There are two types of small wireless communication media including an antenna and an IC chip, so-called wireless tags, an active type with a built-in battery for transmitting data and a passive type without a battery.

As shown in FIG. 6, a wireless communication device that performs wireless communication with a passive wireless tag first transmits an unmodulated signal CW for a certain period of time to supply power to the wireless tag (section T1 in FIG. 6). Next, information is transmitted to the wireless tag using the modulated wireless signal ASK modulated by amplitude shift keying (section T2 in FIG. 6). After the transmission of information, the unmodulated signal CW is continuously transmitted again. A wireless tag that is supplied with power by an unmodulated signal performs backscatter modulation by changing the amount of reflection of the unmodulated signal according to information from the wireless communication device, and transmits information to the wireless communication device. . The wireless communication device receives the backscatter modulated wave BW, demodulates it, and reads the information of the wireless tag (section T3 in FIG. 6). Thus, the wireless communication device can read information such as a tag ID stored in the wireless tag in a non-contact manner and can write information in the wireless tag in a non-contact manner (see, for example, Patent Document 1).
JP 2007-235209 A

  In a conventional wireless communication system with a passive wireless communication medium, an unmodulated signal CW for supplying power to the wireless communication medium must be transmitted for a certain period of time before transmitting information to the wireless communication medium. This time (section T1 in FIG. 6) is useless considering the efficiency of information transmission.

  On the other hand, when a plurality of wireless communication devices are used in combination, it is necessary to adjust the wireless communication devices so that the same frequency is not used. In order to perform the adjustment, it is necessary to connect each wireless communication device via a wired LAN (Local Area Network) or the like to transmit information between them. For this purpose, it is necessary to route the communication cable, and it takes time to construct the system, and there are problems such as complicated design changes such as relocation of the wireless communication device.

  Such problems may be achieved by using wireless communication for information transmission between wireless communication devices. However, when wireless communication is used, the wireless communication efficiency with the wireless communication medium is deteriorated accordingly. For this reason, it is not practical to use wireless communication for information transmission between wireless communication devices.

  The present invention has been made based on such circumstances, and the object of the present invention is to transmit information using wireless communication with other wireless communication devices without deteriorating wireless communication efficiency with the wireless communication medium. The present invention is intended to provide a wireless communication apparatus that can easily perform a system that uses a plurality of wireless communication apparatuses and a wireless communication system that uses a plurality of such wireless communication apparatuses.

The present invention provides a signal for supplying power to a passive wireless communication medium, a modulation signal for transmitting information to the wireless communication medium, and a non-modulated signal for acquiring information from the wireless communication medium, A wireless communication apparatus for wirelessly transmitting from a antenna, a means for wirelessly transmitting a modulated signal modulated at a constant amplitude from the antenna within a period for transmitting a signal for supplying power to a wireless communication medium ; And a means for demodulating the received modulated signal subjected to constant amplitude modulation and acquiring information of the other wireless communication apparatus for transmitting information using the modulated signal subjected to constant amplitude modulation .

  According to the present invention in which such measures are taken, a plurality of wireless communication apparatuses can perform information transmission using wireless communication with another wireless communication apparatus without deteriorating wireless communication efficiency with the wireless communication medium. It is possible to provide a wireless communication apparatus that can easily construct a system that uses both and a wireless communication system that uses a plurality of such wireless communication apparatuses.

The best mode for carrying out the present invention will be described below with reference to the drawings.
In this embodiment, as shown in FIG. 2, a case will be described in which information of a plurality of passive wireless tags 2 is read using two wireless communication apparatuses 1 (1A, 1B) in combination.

  The principal part structure of the radio | wireless communication apparatus 1 (1A, 1B) in this Embodiment is shown with the block diagram of FIG. The wireless communication devices 1A and 1B have the same configuration, and include a control unit 11, a storage unit 12, a communication interface 13, a digital signal processing unit 14, a transmission unit 15, a reception unit 16, and an oscillator 17. Further, a circulator 18 is provided so that the transmission unit 15 and the reception unit 16 share the antenna 10, and the transmission unit 15 and the reception unit 16 are connected to the circulator 18. The antenna 10 is connected to a circulator 18 via a BPF (band pass filter) 19.

  The transmission unit 15 includes an I signal system DAC (digital / analog converter) 151 and an LPF (low pass filter) 152, a Q signal system DAC 153 and an LPF 154, a quadrature modulator 155, and an amplifier 156. ing. The encoded I signal and Q signal output from the digital signal processing unit 14 are input to the quadrature modulator 155 via the DACs 151 and 153 and the LPFs 152 and 154, respectively. The quadrature modulator 155 supplies the I signal and the Q signal to different mixers, modulates the local signal from the oscillator 17 as it is in one mixer, and modulates the local signal from the oscillator 17 in the other mixer. The signal is modulated with a phase shift of 90 degrees, and the output of each mixer is combined to generate a modulated signal. The modulated signal is amplified by the amplifier 156, then supplied to the antenna 10 via the circulator 18 and the BPF 19, and radiated, for example, as a radio wave in the UHF band.

  The receiving unit 16 includes an orthogonal demodulator 161, an I signal LPF 162 and an ADC (analog / digital converter) 163, and a Q signal LPF 164 and an ADC 165. The reception modulation signal from the antenna 10 is supplied to the quadrature demodulator 161 via the BPF 19 and the circulator 18. The quadrature demodulator 161 supplies the reception modulation signal from the antenna 10 to the two mixers, respectively, adds one local signal from the oscillator 17 to one mixer and demodulates the I signal, and the other mixer uses the oscillator. The local signal from 17 is added with the phase shifted by 90 degrees to demodulate the Q signal. The demodulated I signal and Q signal are given to the digital signal processing unit 14 via the LPFs 162 and 164 and the ADCs 163 and 165, respectively, and decoded as wireless reception information.

  When the wireless communication device 1 (1A, 1B) having such a configuration communicates with the wireless tag 2, the digital signal processing unit 14 transmits the I signal and the Q signal having the signal waveform shown in FIG. In FIG. 3, the horizontal axis indicates time, and the vertical axis indicates amplitude.

  A section T11 shows the modulated signal FSK that has been subjected to constant amplitude modulation by frequency shift keying. A section T12 shows the unmodulated signal CW. In these sections T11 and T12, the wireless communication device 1 (1A, 1B) supplies power to the passive wireless tag 2. When compared with FIG. 6 described in the background art section, these sections T11 and T12 correspond to the section T1. In the present embodiment, a modulated signal FSK obtained by constant amplitude modulation of its own identification number and transmission schedule information by frequency shift keying in a section T11 during which a signal for supplying power to the wireless tag 2 is transmitted. Is wirelessly transmitted from the antenna 10 (constant amplitude modulation transmission means).

  Incidentally, each wireless communication device 1 (1A, 1B) stores a unique identification number in the storage unit 12.

  A section T13 indicates a modulation signal ASK modulated by amplitude shift keying. In this section T13, the wireless communication device 1 (1A, 1B) transmits information to the wireless tag. When compared with FIG. 6, this section T13 corresponds to the section T2.

  A section T14 shows the unmodulated signal CW. In this section T14, the passive wireless tag 2 activated upon receiving power supply by the modulation signal FSK performs backscatter modulation and wirelessly transmits information such as a tag ID. When compared with FIG. 6, the section T14 corresponds to the section T3.

The digital signal processing unit 14 is controlled by the control unit 11. Accordingly, the main control procedure executed by the control unit 11 will be described with reference to the flowcharts of FIGS. 4 and 5.
The control unit 11 determines whether or not the information of the other wireless communication device is received wirelessly as ST (step) 1. If not received (NO in ST1), the control unit 11 determines whether an inquiry request command has been received from the external host device as ST2. If no inquiry request command has been received, the process returns to ST1. That is, the control unit 11 receives information on the other wireless communication device or waits for an inquiry request command from the external host device.

  As described above, when each wireless communication device 1 (1A, 1B) communicates with the wireless tag 2, the modulated signal FSK obtained by constant amplitude modulation of its own identification number and transmission schedule information by frequency shift keying. Send. The modulation signal FSK radiated from the antenna 10 of one radio communication device can be received by the antenna 10 of the other radio communication device. When the modulation signal FSK is received by the antenna 10, the modulation signal FSK is supplied to the reception unit 16. In the receiving unit 16, the identification number and the transmission schedule information are demodulated from the modulated signal FSK. The demodulated identification number and transmission schedule information are given to the control unit 11 via the digital signal processing unit 14 (other device information acquisition means).

  When information (identification number, transmission schedule information) wirelessly transmitted from the other wireless communication device by frequency shift keying is received via the digital signal processing unit 14 (YES in ST1), the control unit 11 receives as ST3. The storage unit 12 stores the identification number of the other wireless communication device included in the information and the transmission schedule information in association with each other. Thereafter, the control unit 11 returns to ST1 and receives the information of the other wireless communication device again or waits for an inquiry request command from the external host device.

  On the other hand, the external host device is connected to the communication interface 13. The external host device outputs an inquiry request command to the wireless communication device 1 (1A, 1B) when it is time to read the information stored in the wireless tag 2.

  When the inquiry request command from the external host device is received via the communication interface 13 (YES in ST2), the control unit 11 determines whether or not the use frequency is released as ST4. If not open (NO in ST4), the control unit 11 determines whether or not the frequency is occupied continuously for a long time as ST5.

  The transmission schedule information transmitted from the other wireless communication device includes information regarding the frequency used and the transmission time when the wireless communication device performs wireless communication with the wireless tag 2. The control unit 11 determines whether or not the use frequency is released from the information regarding the use frequency of the other wireless communication device stored in the storage unit 12. If it is not open, it is determined from the information regarding the transmission time of the other wireless communication device stored in the storage unit 12 whether or not it is occupied continuously for a long time.

  If it is determined that the occupied time of the used frequency is shorter than the set time and is shorter (NO in ST5), the control unit 11 waits for the used frequency to be released (ST4). On the other hand, when it is determined that the occupied time of the used frequency is longer than the set time and is a long time (YES in ST5), the control unit 11 switches the used frequency to another frequency as ST6. Thereafter, the control unit 11 starts inquiry transmission as ST7.

  On the other hand, when the use frequency is released or when it is released in a short time (YES in ST4), the control unit 11 starts inquiry transmission without changing the use frequency.

  The detailed procedure of inquiry transmission is shown in the flowchart of FIG. As shown in the figure, when inquiry transmission is started, the control unit 11 acquires its own identification number and transmission schedule information as ST11. The transmission schedule information includes transmission required time, use frequency, and the like. The control unit 11 outputs the identification number and transmission schedule information to the digital signal processing unit 14 together with a constant amplitude modulation transmission command.

  Upon receiving this transmission command, the digital signal processing unit 14 generates an I signal and a Q signal corresponding to the constant amplitude modulation from the identification number and the transmission schedule information, and outputs them to the transmission unit 15 (section T11 in FIG. 3). . Then, the transmitter 15 generates a modulated signal FSK that has been subjected to constant amplitude modulation by frequency shift keying, and is wirelessly transmitted from the antenna 10.

  The controller 11 waits for a predetermined time to elapse from the start of transmission of the modulation signal FSK as ST12. When the predetermined time has elapsed, the control unit 11 outputs a non-carrier wave transmission command as ST13.

  In response to this transmission command, the digital signal processing unit 14 generates an I signal and a Q signal corresponding to no carrier wave and outputs them to the transmission unit 15 (section T12 in FIG. 3). Then, an unmodulated signal CW is generated in the transmission unit 15 and wirelessly transmitted from the antenna 10.

  The controller 11 waits for a predetermined time to elapse from the start of transmission of the unmodulated signal CW in ST14. If the predetermined time has elapsed, the control unit 11 outputs a tag inquiry command to the digital signal processing unit 14 together with an amplitude shift keying transmission command in ST15.

  Upon receiving this transmission command, the digital signal processing unit 14 generates an I signal and a Q signal corresponding to amplitude shift keying from the tag inquiry command, and outputs them to the transmission unit 15 (section T13 in FIG. 3). Then, a modulation signal ASK modulated by amplitude shift keying is generated in the transmission unit 15 and is wirelessly transmitted from the antenna 10.

  The control unit 11 waits for a predetermined time to elapse from the start of transmission of the modulation signal ASK as ST16. If the predetermined time has elapsed, the control unit 11 outputs a non-carrier wave transmission command as ST17.

  Upon receiving this transmission command, the digital signal processing unit 14 generates an I signal and a Q signal corresponding to no carrier wave and outputs them to the transmission unit 15 (section T14 in FIG. 3). Then, an unmodulated signal CW is generated in the transmission unit 15 and wirelessly transmitted from the antenna 10.

  On the other hand, the wireless tag 2 that is supplied with power by the carrier wave of the modulated signal FSK and the subsequent unmodulated signal CW determines the reflection amount of the subsequent unmodulated signal CW in response to the tag inquiry command demodulated from the modulated signal ASK. The backscatter modulation to be changed is performed, and the RFID tag response information including the tag ID is transmitted.

  The control unit 11 determines whether or not the wireless tag response information is received as ST18. When the backscatter modulated wave is received by the antenna 10, the RFID tag response information is demodulated by the receiving unit 16 based on the signal of the backscatter modulated wave. The demodulated RFID tag response information is given to the control unit 11 via the digital signal processing unit 14. In ST19, the control unit 11 outputs this RFID tag response information to the external host device, and ends this inquiry transmission.

  The controller 11 waits for the inquiry transmission to end as ST8. When the inquiry transmission is completed, the control unit 11 stops the transmission of the non-carrier and returns to the process of ST1.

  In this embodiment configured as described above, it is assumed that an inquiry request command is transmitted from the external host device to one of the wireless communication apparatuses 1A. In this case, the wireless communication device 1A that has received the command determines whether or not the frequency used by itself is open. Assuming that the used frequency is open, the wireless communication device 1A starts inquiry transmission.

  First, the wireless communication device 1A wirelessly transmits a modulation signal FSK obtained by performing constant amplitude modulation of its own identification number and transmission schedule information by frequency shift keying for a certain period of time. Next, the wireless communication device 1A wirelessly transmits the non-modulated signal CW for a certain period of time, and then wirelessly transmits the modulated signal ASK obtained by modulating the tag inquiry command by amplitude shift keying for a certain period of time. When the transmission of the modulation signal ASK is finished, the wireless communication device 1A continues to wirelessly transmit the non-modulation signal CW.

  The wireless tag 2 that has received the modulated signal FSK wirelessly transmitted from the wireless communication apparatus 1A converts the constant-amplitude modulated carrier wave into power, charges the power necessary for the wireless tag 2 to start up, and starts up. When the activated wireless tag 2 receives the tag inquiry command, the wireless tag 2 transmits wireless tag response information including the tag ID by backscatter modulation. That is, the wireless tag response information is sent back to the wireless communication device 1A by changing the amount of reflection of the carrier wave of the unmodulated signal CW transmitted following the modulated signal ASK. The wireless communication device 1A receives a signal subjected to backscatter modulation while transmitting the non-modulated signal CW, demodulates it, and acquires wireless tag response information.

  The wireless communication device 1A continues to transmit the non-modulated signal CW until acquisition of the wireless tag response information is completed. When the acquisition is completed, the unmodulated signal CW is stopped. As a result, radio waves from the wireless communication device 1A do not reach the wireless tag 2, so that the wireless tag 2 stops its operation.

  By the way, the other wireless communication device 1B can receive the modulation signal FSK of constant amplitude modulation wirelessly transmitted from the wireless communication device 1A. When the modulation signal FSK is received, the signal FSK is demodulated. Then, the identification number and transmission schedule information of the wireless communication device 1A are demodulated and stored in the storage unit 12.

  At this time, it is assumed that an inquiry request command is also transmitted from the external host device to the wireless communication apparatus 1B. In this case, the use frequency is recognized as being used from the transmission schedule information of the wireless communication device 1A. Here, assuming that the occupation time of the use frequency extends for a long time, the wireless communication device 1B changes the use frequency to another frequency. Then, the inquiry transmission is started using this different frequency.

  That is, a modulated signal FSK obtained by constant frequency modulation of its own identification number and transmission schedule information by frequency shift keying is wirelessly transmitted for a certain period of time, and then a non-modulated signal CW is wirelessly transmitted for a certain period of time. A modulated signal ASK modulated by amplitude shift keying is wirelessly transmitted for a certain period of time. When transmission of this modulated signal ASK is completed, wireless transmission of the non-modulated signal CW is continued until acquisition of the wireless tag response information is completed.

  As described above, the wireless communication apparatus 1 according to the present embodiment wirelessly transmits the modulated signal FSK modulated with constant amplitude from the antenna 10 within a period in which a signal for supplying power to the wireless tag 2 is transmitted. . The modulated signal FSK is used to notify other wireless communication devices of information such as its own identification number and transmission schedule information. Therefore, it is possible to effectively transmit a signal transmission period for supplying power to the wireless tag 2 and perform information transmission by wireless communication with other wireless communication devices. As a result, there is no need to route communication cables when building a system that uses multiple wireless communication devices together, making it easy to build a system and easily handle design changes such as moving wireless communication devices. An effect that can be achieved.

  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, in the above embodiment, the constant amplitude modulation method of the signal wirelessly transmitted by the constant amplitude modulation transmission unit is the frequency shift key modulation, but the constant amplitude modulation method is not limited to the frequency shift key modulation, Any modulation method in which the amplitude of the carrier wave is constant may be used.

  In the above-described embodiment, the information transmitted to another wireless communication device using the modulated signal subjected to constant amplitude modulation is the identification number and the transmission schedule information. However, the type of information transmitted is particularly limited. It can be implemented as appropriate.

  Further, the present invention is not limited to a wireless communication system including two wireless communication devices, and the number of wireless communication devices constructing the system may be three or more.

  In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, the constituent elements over different embodiments may be combined.

The block block diagram of the radio | wireless communication apparatus which is one embodiment of this invention. 1 is a schematic diagram of a wireless communication system in the same embodiment. FIG. The figure which shows the example of a pattern of the I / Q signal processed with a radio | wireless communication apparatus in the embodiment. 4 is a flowchart showing a main control procedure executed by the control unit of the wireless communication apparatus in the embodiment. The flowchart which shows the procedure after the inquiry transmission start in FIG. 4 concretely. The figure for demonstrating the prior art example of the signal pattern radio-transmitted by the radio | wireless tag from a radio | wireless communication apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 (1A, 1B) ... Wireless communication apparatus, 2 ... Wireless tag, 10 ... Antenna, 11 ... Control part, 12 ... Memory | storage part, 13 ... Communication interface, 14 ... Digital signal processing part, 15 ... Transmission part, 16 ... Reception Part, 17 ... oscillator, 18 ... circulator, 19 ... BPF (band pass filter).

Claims (4)

A signal for supplying power to a passive wireless communication medium, a modulation signal for transmitting information to the wireless communication medium, and a non-modulated signal for acquiring information from the wireless communication medium are transmitted from an antenna. In a wireless communication device for wireless transmission,
Constant amplitude modulation transmission means for wirelessly transmitting a modulation signal modulated with constant amplitude from the antenna within a period of transmitting a signal for supplying power to the wireless communication medium ;
Other apparatus information acquisition means for demodulating a constant amplitude modulated modulation signal received by the antenna and acquiring information of the other wireless communication apparatus that transmits information using the constant amplitude modulated modulation signal;
A wireless communication apparatus comprising:   The wireless communication apparatus according to claim 1, wherein the constant amplitude modulation is frequency shift keying. A wireless communication system comprising a plurality of wireless communication devices according to claim 1 , wherein information is transmitted between the wireless communication devices using the modulation signal modulated with constant amplitude. 4. The wireless communication system according to claim 3 , wherein information transmitted between the wireless communication devices using the modulated signal subjected to constant amplitude modulation is information relating to the identification information and transmission schedule.

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