JP4738240B2 - Communication frequency setting method for wireless communication - Google Patents

Description

  The present invention relates to a communication frequency setting method for wireless communication performed while hopping a communication frequency.

  As is well known, spread wireless communication is intended to reduce the influence of noise on communication and to improve communication frequency utilization efficiency. As one of the methods, frequency hopping involves performing wireless communication while changing the communication frequency and performing hopping. There is a method.

In this frequency hopping method, the communication frequency is set at random in order to suppress the deviation of the communication frequency used in the specified communication frequency band. For example, the communication frequency is set using a random number or a random number table, or one of a plurality of hopping patterns is selected using a random number, and the communication frequency is set using the selected hopping pattern. (See Patent Document 1).
JP 2000-151468 A

  By the way, in the frequency hopping method, the maximum transition width of the communication frequency by hopping is the transition width when the communication frequency is changed from the highest channel frequency to the lowest channel frequency in the specified communication frequency band, or conversely, the largest. This is the transition width when the communication frequency is changed from the lower channel frequency to the highest channel frequency. And the communication speed of the communication device tends to decrease as the maximum transition width of the communication frequency becomes wider.

  For example, if 24 channel frequencies are set at 1 MHz intervals and the communication frequency is set to any one of the channel frequencies, the specified communication frequency band is 23 MHz and the maximum transition width of the communication frequency is 23 MHz. The average transition width of the communication frequency is 12 MHz. Even if the average transition time when the average transition width is 12 MHz is shorter than the maximum transition time when the maximum transition width is 23 MHz, when the transition of the communication frequency starts, until the maximum transition time elapses from the transition start time Prohibits communication. For this reason, useless non-communication time zone became long and the communication speed fell.

  In addition, in the case of using a battery-less passive wireless tag in an RFID (Radio Frequency Identification) system, if the non-communication time zone becomes longer, the time during which the power supply to the wireless tag is interrupted becomes longer. Has been cleared, communication can no longer be continued, and communication has to be performed again.

  On the other hand, if the response speed (communication frequency transition speed) of the communication device is increased, the maximum transition time is shortened, the non-communication time zone is also shortened, and the communication speed is increased. When the communication frequency is controlled using the PLL circuit, the response speed of the loop filter may be increased. Thereby, the maximum transition time is shortened and the non-communication time zone is also shortened.

  However, when the response speed of the loop filter is increased, the operation of the loop filter becomes unstable, the noise component of the output of the PLL circuit increases, and spurious waves are easily generated. In particular, when the transition width of the communication frequency is wide, spurious is more likely to occur and occurs outside the specified communication frequency band, which adversely affects communications outside the specified communication frequency band. For this reason, the response speed of the PLL circuit cannot be sufficiently increased.

  Such a problem may occur not only in the RFID system or the PLL circuit but also in other types of communication devices or frequency oscillation circuits to which the frequency hopping method is applied.

  Therefore, the present invention has been made in view of the above-described conventional problems, and can shorten the non-communication time period and increase the communication speed without increasing the response speed of the communication apparatus. It is an object of the present invention to provide a communication frequency setting method for wireless communication that can suppress the occurrence of noise.

In order to solve the above-described problem, the present invention provides a communication frequency setting method for wireless communication performed while hopping a communication frequency, and includes three or more communication frequency bands used for the wireless communication that do not overlap each other . Dividing into sub-frequency bands, a plurality of channel frequencies are set in each of the sub-frequency bands, selecting one of the sub-frequency bands, and one channel frequency included in the selected sub-frequency band being When set as the communication frequency, the next communication frequency is randomly set to one of the channel frequencies included in the selected sub-frequency band or another sub-frequency band adjacent to the selected sub-frequency band. .

  In addition, among the sub-frequency bands, the highest frequency side sub-frequency band and the lowest frequency side sub-frequency band have a smaller number of channel frequencies allocated than other sub-frequency bands.

  Furthermore, the set frequency of the channel frequency in the sub frequency band is set according to the number of channel frequencies in the sub frequency band.

  Further, the communication time in the sub frequency band is set according to the number of channel frequencies in the sub frequency band.

  Further, among the sub-frequency bands, each sub-frequency band from the highest frequency side to the second sub-frequency band and each sub-frequency band from the lowest frequency side to the second sub-frequency band are channel frequencies allocated to other sub-frequency bands. The number of has been reduced.

  In the communication frequency setting method of the present invention, the communication frequency band is divided into three or more sub-frequency bands, and a plurality of channel frequencies are respectively allocated to these sub-frequency bands. When one channel frequency included in the sub-frequency band is set as the communication frequency, either the sub-frequency band or another sub-frequency band adjacent to the sub-frequency band is set as the next communication frequency. The channel frequency is set. Therefore, the maximum transition width of the communication frequency is equal to the transition width between the highest channel frequency and the lowest channel frequency in two sub frequency bands adjacent to each other, and the highest channel frequency and the highest in all communication frequency bands. Narrower than the transition width between lower channel frequencies. For this reason, the maximum transition time from the start of transition of the communication frequency to the end of transition is shortened. Therefore, even if communication is prohibited during the period from the start of transition of the communication frequency until the maximum transition time elapses, the non-communication time zone is shortened, and a decrease in communication speed can be suppressed. Further, it is not necessary to increase the response speed (communication frequency transition speed) of the communication device, and the maximum transition width of the communication frequency is narrowed, so that it is difficult for spurious waves to occur.

  The highest frequency side sub-frequency band and the lowest frequency side sub-frequency band have fewer channel frequencies allocated than other sub-frequency bands. Therefore, the sub-frequency band on the highest frequency side and the sub-frequency band on the lowest frequency side are narrower than the other sub-frequency bands. Therefore, the maximum transition width between the highest channel frequency in the sub-frequency band on the highest frequency side and the lowest channel frequency in other sub-frequency bands adjacent to the sub-frequency band becomes narrower, and similarly the lowest frequency The maximum transition width between the lowest channel frequency in the side sub-frequency band and the highest channel frequency in the other sub-frequency bands adjacent to the sub-frequency band becomes narrower. In this way, if the maximum transition width of the communication frequency is narrower on the high frequency side and the low frequency side, it is difficult for spurious waves to occur outside the communication frequency band, and it does not adversely affect communication outside the communication frequency band. It will end.

  Furthermore, the number of channel frequency settings in the sub frequency band is set according to the number of channel frequencies in the sub frequency band. That is, as the number of channel frequencies in the sub-frequency band increases, the number of channel frequency settings increases, and as the number of channel frequencies decreases, the number of channel frequency settings decreases. Thereby, the selection probability of all the channel frequencies becomes equal, and the bias of the communication frequency used can be suppressed.

  The communication time in the sub frequency band is set according to the number of channel frequencies in the sub frequency band. That is, the communication time is lengthened as the number of channel frequencies in the sub-frequency band is increased, and the communication time is shortened as the number of channel frequencies is decreased. For this reason, even if the number of channel frequencies in the sub-frequency band is large and the channel frequency selection probability is low, the communication time per channel frequency becomes long. Thereby, the communication power of all the channel frequencies becomes equal, and the bias of the communication power density in the communication frequency band can be suppressed.

  Furthermore, each sub-frequency band from the highest frequency side to the second sub-frequency band and each sub-frequency band from the lowest frequency side to the second sub-frequency band of each sub-frequency band are channel frequencies allocated to other sub-frequency bands. The number has been reduced. In this case, the maximum transition width between the sub-frequency bands from the highest frequency side to the second is narrower, and similarly, the maximum transition width between the sub-frequency bands from the lowest frequency side to the second is the same. Narrower. For this reason, spurious is less likely to occur outside the communication frequency band.

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

<Embodiment 1>
FIG. 1 is a block diagram showing an RFID system to which Embodiment 1 of a communication frequency setting method of the present invention is applied. This RFID system includes a reader / writer 1 and a wireless tag 2, and performs bidirectional wireless communication while changing the communication frequency and causing hopping.

  The reader / writer 1 changes the communication frequency f to cause hopping, and at each hopping, transmits a radio wave of the communication frequency f at that time, and receives and demodulates the radio wave of the same communication frequency f. The wireless tag 2 is a general battery-less passive type. When receiving a radio wave from the reader / writer 1, the radio tag 2 converts the power of the received radio wave into a DC voltage for operation (of the wireless tag 2). ,Operate. In addition, when the radio tag 2 receives a radio wave from the reader / writer 1, the impedance of the antenna is controlled to change the reflectance of the radio wave received by the antenna, thereby returning it to the reader / writer 1.

  Accordingly, the communication frequency f is set on the reader / writer 1 side, and the communication frequency on the wireless tag 2 side follows this.

  The reader / writer 1 includes a control unit 11, a PLL circuit 12, a transmission circuit 13, a reception circuit 14, a circulator 15, and an antenna 16.

  The control unit 11 includes a CPU, a memory, an interface, and the like, and controls the entire reader / writer 1. The control unit 11 drives and controls the PLL circuit 12, changes the frequency (communication frequency f) of the carrier signal Sm output from the PLL circuit 12, and hops the carrier signal Sm of the PLL circuit 12. And input to the receiving circuit 14. In addition, the control unit 11 outputs transmission data conforming to a communication protocol performed with the wireless tag 2 to the transmission circuit 13.

  When the transmission circuit 13 receives the transmission data from the control unit 11 and the carrier signal Sm having the communication frequency f from the PLL circuit 12, the transmission circuit 13 modulates the carrier signal Sm according to the transmission data to form a transmission signal indicating the transmission data. Output. This transmission signal is applied to the antenna 16 through the circulator 15 and transmitted from the antenna 16 as a radio wave having a communication frequency f.

  When the radio tag 2 receives a radio wave from the reader / writer 1 as described above, the radio tag 2 operates with power obtained from the received radio wave, controls the antenna impedance, and changes the reflectance of the radio wave received by the antenna. Thus, a transmission radio wave indicating received data according to the communication protocol is obtained. Therefore, the radio wave transmitted from the wireless tag 2 has the same communication frequency f as the radio wave transmitted from the reader / writer 1.

  The radio wave from the wireless tag 2 is received by the antenna 16 of the reader / writer 1 and becomes a received signal. This received signal is applied to the receiving circuit 14 through the circulator 15. When the reception circuit 14 receives the reception signal from the antenna 16 and the carrier signal Sm of the communication frequency f from the PLL circuit 12, the reception circuit 14 demodulates the reception signal using the carrier signal Sm of the communication frequency f, The reception data is formed as a demodulated output, and this reception data is output to the control unit 11. When receiving the reception data from the reception circuit 14, the control unit 11 processes the reception data.

  In the present embodiment, for example, bidirectional wireless communication is performed while changing the communication frequency f in units of 1 MHz in the communication frequency band BB (bandwidth is 23 MHz) of 2402 MHz to 2425 MHz and performing hopping. Accordingly, the communication frequency f is set to one of 24 channel frequencies 2402 MHz, 2403 MHz,..., 2424 MHz, 2425 MHz.

  The PLL circuit 12 includes a reference oscillator 21, a reference frequency divider 22, a phase comparator 23, a loop filter 24, a voltage control oscillator 25, and a communication frequency divider 26.

  The reference oscillator 21 oscillates and outputs a reference signal Sb having a reference frequency of 10 MHz. The reference frequency divider 22 receives the reference signal Sb, divides the reference frequency 10 MHz of the reference signal Sb by the division ratio 10, and outputs a 1 MHz reference input signal S1.

  The voltage controlled oscillator 25 oscillates in a communication frequency band BB of at least 2402 MHz to 2425 MHz and outputs a carrier wave signal Sm of the communication frequency f in the communication frequency band BB. The control signal is input, oscillates at a frequency corresponding to the voltage of the control signal, and the carrier signal Sm having this frequency is output.

  The carrier wave signal Sm output from the voltage controlled oscillator 25 is output to the transmission circuit 13 and the reception circuit 14 and also to the communication frequency divider 26.

  Further, the control unit 11 instructs the communication frequency divider 26 of any one of the frequency division ratios 2402, 2403, ..., 2424, 2425 corresponding to the 24 channel frequencies.

  The communication frequency divider 26 receives the carrier wave signal Sm from the voltage controlled oscillator 25, and when the frequency division ratio corresponding to one channel frequency is instructed from the control unit 11, the frequency of the carrier wave signal Sm is indicated. The frequency is divided by the divided frequency ratio, and the divided signal Si is output.

  The phase comparator 23 receives the 1 MHz reference input signal S1 from the reference frequency divider 22 and also receives the divided signal Si from the communication frequency divider 26, and the phase and frequency division of the 1 MHz reference input signal S1. The phases of the signals Si are compared, and a voltage control signal corresponding to the phase difference between the two is output. The loop filter 24 extracts the direct current component of the control signal and outputs the direct current component control signal to the voltage controlled oscillator 25.

  For example, if a frequency division ratio 2402 is instructed from the control unit 11 to the communication frequency divider 26, the communication frequency divider 26 converts the frequency of the carrier signal Sm from the voltage controlled oscillator 25 with the frequency division ratio 2402. Frequency division is performed and a frequency division signal Si is output. At this time, if the frequency of the carrier wave signal Sm is significantly different from the channel frequency 2402 MHz, the frequency of the frequency-divided signal Si is greatly different from 1 MHz. Therefore, the phase of the 1 MHz reference input signal S1 compared by the phase comparator 23 and the phase of the frequency-divided signal Si are greatly shifted. From the phase comparator 23, a voltage control signal corresponding to the phase difference between the two is obtained. Is output. When the direct current component of the control signal is applied to the voltage controlled oscillator 25 via the loop filter 24, the oscillation frequency of the voltage controlled oscillator 25 changes according to the voltage of the control signal, and the carrier wave output from the voltage controlled oscillator 25 The frequency of the signal Sm approaches the channel frequency 2402 MHz.

  Then, as the frequency of the carrier signal Sm approaches the channel frequency 2402 MHz, the frequency of the divided signal Si approaches 1 MHz, and the voltage of the control signal corresponding to the phase difference between the reference input signal S1 and the divided signal Si converges. As a result, the frequency of the carrier wave signal Sm oscillated and output by the voltage controlled oscillator 25 converges to a channel frequency of 2402 MHz.

  Further, when the frequency of the carrier signal Sm from the voltage controlled oscillator 25 matches the channel frequency 2402 MHz, the frequency of the divided signal Si becomes 1 MHz, the voltage of the control signal applied to the voltage controlled oscillator 25 becomes stable, and the carrier signal Sm. Is maintained at a channel frequency of 2402 MHz.

  Similarly, when any one of the other division ratios 2403,..., 2424, 2425 is instructed from the control unit 11 to the communication frequency divider 26, the frequency of the carrier wave signal Sm is also increased by the instructed amount. The phase comparator 23 compares the phase of the 1 MHz reference input signal S1 with the phase of the divided signal Si, and the voltage of the control signal corresponding to the phase difference between them is applied to the voltage controlled oscillator 25. The frequency of the carrier signal Sm is controlled so as to match the channel frequency corresponding to the designated frequency division ratio.

  In this way, in the PLL circuit 12, when the frequency division ratio is instructed from the control unit 11, the frequency of the carrier wave signal Sm is matched with the channel frequency corresponding to the instructed frequency division ratio, and the communication frequency is set to this channel frequency. Set f.

  By the way, in the communication frequency band BB of 2402 to 2425 MHz, the communication frequency f is hopped (transitioned) from the lowest channel frequency 2402 MHz to the highest channel frequency 2425 MHz, or conversely from the channel frequency 2425 MHz to the channel frequency. If the transition is made to 2402 MHz, the maximum transition width of the communication frequency f becomes 23 MHz, and the maximum transition time becomes long.

  Therefore, in this embodiment, as shown in FIG. 2A, the communication frequency band BB of 2402 MHz to 2425 MHz is divided into three sub frequency bands SB1, SB2, and SB3, and 24 corresponding to the channel frequencies 2402 to 2425 MHz. Channels 02Ch to Ch25 are allocated to three sub-frequency bands SB1 to SB3. Specifically, eight channels 02Ch to 09Ch are allocated to the sub-frequency band SB1, eight channels 10Ch to 17Ch are allocated to the sub-frequency band SB2, and eight channels 18Ch to Ch25 are allocated to the sub-frequency band SB3.

  When the communication frequency f is set to one channel frequency in one sub-frequency band, the next communication frequency f is either the sub-frequency band or another sub-frequency band adjacent to the sub-frequency band. The channel frequency is set.

  For example, when the communication frequency f is set to the channel frequency 2402 MHz in the sub-frequency band SB1, the next communication frequency f is set to each channel frequency 2402 MHz to the sub-frequency band SB1 and the sub-frequency band SB2 adjacent to the sub-frequency band SB1. One of 2417 MHz is set. Similarly, when the communication frequency f is set to the channel frequency of the sub-frequency band SB3, the next communication frequency f is set to one of the channel frequencies in the sub-frequency band SB3 and the sub-frequency band SB2. When the communication frequency f is set to the channel frequency of the sub frequency band SB2, the next communication frequency f is set to any one of the channel frequencies in the sub frequency band SB2 and the sub frequency band SB1, or the next communication The frequency f is set to any channel frequency in the sub frequency band SB2 and the sub frequency band SB3.

  For this reason, the maximum transition width of the communication frequency f is equal to the transition width between the channel frequency on the lowest frequency side and the channel frequency on the highest frequency side in each sub frequency band adjacent to each other. For example, the transition width is 15 MHz between the channel frequency 2402 MHz in the sub-frequency band SB1 and the channel frequency 2417 MHz in the sub-frequency band SB2.

  Since this maximum transition width 15 MHz is narrower than the maximum transition width 23 MHz in the communication frequency band BB of 2402 MHz to 2425 MHz, the maximum transition time of the communication frequency f is shortened. Therefore, even if communication is prohibited between the transition start time of the communication frequency f and the maximum transition time elapses, the non-communication time zone is shortened, and a decrease in communication speed can be suppressed. Further, in order to shorten the non-communication time zone, it is not necessary to reduce the time constant of the loop filter 24 of the PLL circuit 12 to increase the response speed of the loop filter 24 and the maximum transition width is narrow. Spurious is less likely to occur.

  Next, a control process for hopping the communication frequency f while selecting each sub-frequency band and channel so that the maximum transition width of the communication frequency f can be suppressed will be described with reference to the flowcharts of FIGS. To do.

  First, the control unit 11 initializes the order index STEP to the value 1 (step S101), and then proceeds to the routine shown in the sub-flowchart of FIG. 4 (step S102).

  In this sub-flowchart routine, the control unit 11 refers to the value 1 of the order index STEP set in step S101, and selects the sub-frequency band SB1 corresponding to the value 1 of the order index STEP (step S201). The lowest frequency channel 02Ch in the sub frequency band SB1 is set as the minimum channel Chmin in the sub frequency band, and the value 08 is set as the number N of channels in the sub frequency band SB1 (step S202). And it returns to step S103 of the flowchart of FIG.

  Next, the control unit 11 substitutes the channel 02Ch and the value 08 set in step S202 for the minimum channel Chmin and the number of channels N in the sub-frequency band in the following equation (1), further obtains and substitutes the random number RND, Ch is obtained (step S103).

Ch = Chmin + int (RND × N) (1)
However, int (RND × N) is a function indicating truncation after the decimal point of (RND × N).

  Here, the random number RND is set in a range of 0 ≦ random number RND <1. For this reason, int (RND × N) in the above formula (1) is set in the range of 0 to 7, and Ch = 02 + (0 to 7). Accordingly, the channel Ch is randomly set to one of the channels 02Ch to 09Ch in the sub frequency band SB1.

  Subsequently, the control unit 11 substitutes the channel Ch obtained in step S103 into the following equation (2) to obtain the next communication frequency f (step S104).

f = 2400 + Ch (MHz) (2)
For example, if the channel Ch obtained in step S103 is 02, f = 2400 + 02 = 2402 MHz. Then, the control unit 11 divides the communication frequency f obtained in step S104 by the frequency 1 MHz of the reference input signal S1 output from the reference frequency divider 22 to obtain the division ratio of the communication frequency divider 26. (Step S105), this frequency division ratio is instructed to the communication frequency divider 26.

  For example, if the communication frequency f obtained in step S104 is 2402 MHz, 2402 MHz is divided by 1 MHz to obtain a division ratio of 2402, and this division ratio 2402 is instructed to the communication frequency divider 26.

  In the PLL circuit 12, when the frequency division ratio 2402 is instructed from the control unit 11 as described above, the frequency of the carrier wave signal Sm is matched with the channel frequency 2402 MHz corresponding to the instructed frequency division ratio 2402, The communication frequency f is set to this channel frequency 2402 MHz.

  At this time, the control unit 11 waits for a certain time necessary for the communication frequency f to transition with the maximum transition width (15 MHz) from the time when the frequency division ratio is instructed. Then, when a certain time has elapsed, the control unit 11 outputs transmission data to the transmission circuit 13, transmits the transmission data, takes in the reception data from the wireless tag 2 through the reception circuit 14, and processes the reception data. (Each step S106, S107).

  Thereafter, the control unit 11 adds 1 to the order index STEP set in step S101, updates the order index STEP to the value 2 (step S108), and the value 2 of the order index STEP becomes the cyclic index M (= 6). ) After confirming the following ("No" in step S109), the process returns to step S102 and proceeds to the routine shown in the sub-flowchart of FIG.

  Next, the control unit 11 refers to the value 2 of the order index STEP set in step S108, selects the sub-frequency band SB2 corresponding to the value 2 of the order index STEP (step S201), and within the sub-frequency band The lowest frequency channel 10Ch in the sub-frequency band SB2 is set as the minimum channel Chmin, and the value 08 is set as the number N of channels in the sub-frequency band SB2 (step S203). And it returns to step S103 of the flowchart of FIG.

  In this case, the channel 10Ch and the value 08 set in step S203 are substituted into the above equation (1), the random number RND is obtained and substituted, and any of the channels 10Ch to 17Ch in the sub-frequency band SB2 is random. (Step S103), the channel Ch set in step S103 is substituted into the above equation (2) to obtain the next communication frequency f (step S104), and the communication frequency f obtained in step S104 is the reference frequency. The frequency division ratio is obtained by dividing the reference input signal S1 output from the frequency divider 22 by the frequency of 1 MHz (step S105). This frequency division ratio is instructed to the communication frequency frequency divider 26, and this instruction is performed. To the channel frequency corresponding to the divided frequency ratio, that is, to the next communication frequency f obtained in step S104. Frequency of m is set.

  The transmission data and the reception data are transmitted / received after a certain time required for the communication frequency f to transition with the maximum transition width (15 MHz) (steps S106 and S107).

  Further, 1 is added to the order index STEP, the order index STEP is updated to the value 3 (step S108), and it is confirmed that the value 3 of the order index STEP is equal to or less than the round index M (= 6) ( "No" in step S109), the process returns to step S102, and proceeds to the routine shown in the sub-flowchart of FIG.

  Next, the sub frequency band SB3 corresponding to the value 3 of the order index STEP set in step S108 is selected (step S201), and the sub-frequency band minimum channel Chmin becomes the lowest frequency side channel 18Ch in the sub-frequency band SB3. The value 08 is set as the number N of channels in the sub-frequency band SB3 (step S204), and the process returns to step S103 in the flowchart of FIG.

  In this case, the channel 18Ch and the value 08 set in step S204 are substituted into the above equation (1), the random number RND is obtained and substituted, and any of the channels 18Ch to 25Ch in the sub-frequency band SB3 is random. (Step S103), the channel Ch set in step S103 is substituted into the above equation (2) to obtain the next communication frequency f (step S104), which corresponds to the communication frequency f obtained in step S104. A frequency division ratio is obtained (step S105), the frequency division ratio is instructed to the communication frequency divider 26, and the frequency of the carrier wave signal Sm is controlled to a channel frequency corresponding to the instructed frequency division ratio, The next communication frequency f obtained in step S104 is set.

  Then, after a certain time has passed, transmission / reception of transmission data and reception data is performed (each step S106, S107).

  Further, 1 is added to the order index STEP, the order index STEP is updated to the value 4 (step S108), and it is confirmed that the value 4 of the order index STEP is less than or equal to the cyclic index M (= 6) ( "No" in step S109), the process returns to step S102, and proceeds to the routine shown in the sub-flowchart of FIG.

  Thereafter, the same processing is repeated. In the routine shown in the sub-flowchart of FIG. 4, since the order index STEP set in step S108 is the value 4, the sub frequency band SB3 corresponding to the value 4 of the order index STEP is selected (step S201), and the sub frequency The in-band minimum channel Chmin and the number N of channels are set (step S204), and the process returns to step S103 in the flowchart of FIG. Then, the channel frequency in the sub frequency band SB3 is set at random (step S103), the next communication frequency f is obtained (step S104), and the frequency division ratio of the communication frequency divider 26 is obtained (step S105). The next communication frequency f is set to the channel frequency corresponding to this frequency division ratio. Thereafter, transmission data and reception data are transmitted and received (steps S106 and S107).

  Subsequently, the order index STEP is updated to the value 5 (step S108), and it is confirmed that the value 5 of the order index STEP is equal to or less than the cyclic index M (= 6) (“No” in step S109). Returning to S102, the process proceeds to the sub-flowchart of FIG. At this time, since the order index STEP is 5, the sub-frequency band SB2 corresponding to the order index STEP value 5 is selected (step S201), and the sub-frequency band minimum channel Chmin and the number of channels N are set ( In step S203), the process returns to step S103 in the flowchart of FIG. Then, the channel frequency in the sub frequency band SB2 is set at random (step S103), the next communication frequency f is obtained (step S104), and the division ratio of the communication frequency divider 26 is obtained (step S105). The next communication frequency f is set. Thereafter, transmission data and reception data are transmitted and received (steps S106 and S107).

  Further, the order index STEP is updated to the value 6 (step S108), and it is confirmed that the value 6 of the order index STEP is equal to or less than the cyclic index M (= 6) (“No” in step S109). Returning to FIG. 4, the process proceeds to the sub-flowchart of FIG. At this time, since the order index STEP is 6, the sub-frequency band SB1 corresponding to the order index STEP value 6 is selected (step S201), and the sub-frequency band minimum channel Chmin and the number of channels N are set ( Step S202), the process returns to Step S103 of the flowchart of FIG. Then, the channel frequency in the sub-frequency band SB1 is randomly set (step S103), the next communication frequency f is obtained (step S104), the frequency division ratio is obtained (step S105), and the next communication frequency f is set. Is done. Thereafter, transmission data and reception data are transmitted and received (steps S106 and S107).

  In this way, the order index STEP is sequentially incremented from the value 1 to the value 6, and the sub frequency bands SB1 to SB3 are selected in the order of SB1, SB2, SB3, SB3, SB2, SB1, and the sub frequency band is selected. In addition, a channel frequency in the sub-frequency band is selected at random, and the communication frequency f is set to the selected channel frequency.

  When the order index STEP is updated to the value 7 (step S108), the order index STEP value 7 is not less than or equal to the cyclic index M (= 6) (“Yes” in step S109), and therefore communication is not completed. Is confirmed (“No” in step S110), the process returns to step S101, and the order index STEP is initialized to a value of 1.

  Thereafter, similarly, the processes of steps S101 to S110 and the processes of steps S201 to S204 are repeated. Accordingly, as shown in FIG. 2B, each of the sub frequency bands SB1 to SB3 is repeatedly selected in the order of SB1, SB2, SB3, SB3, SB2, SB1, and SB1, and each time the sub frequency band is selected. In addition, a channel frequency in the sub-frequency band is selected at random, and the communication frequency f is set to the selected channel frequency.

  When it is confirmed that the communication is completed (“Yes” in step S110), the processing of the flowcharts in FIGS. 3 and 4 is terminated.

  By setting the communication frequency f in this way, the transition width of the communication frequency f is suppressed and narrowed in the sub frequency bands adjacent to each other. Therefore, the maximum transition time is shortened and the non-communication time period is shortened. Therefore, a decrease in communication speed can be suppressed. Further, it is not necessary to increase the response speed of the loop filter 24 of the PLL circuit 12 in order to shorten the non-communication time zone, and since the maximum transition width is narrow, it is difficult for radio wave spurious to occur. Furthermore, since the non-communication time zone is short, the interruption time of power supply to the wireless tag 2 is shortened, and the buffer of the wireless tag 2 is not cleared.

  In addition, since the sub frequency bands are sequentially selected in the order shown in FIG. 2B, the channel selection probability is uniform in each sub frequency band, and the selection probabilities of all channels are also equal. Thus, it is possible to suppress the bias of the communication frequency used. When one of the eight channels in the sub-frequency band SB1 is selected twice when the order index STEP is sequentially incremented from the value 1 to the value 6, the probability that the channel in the sub-frequency band SB1 is selected. Is (1/8) × (2/6) = 1/24. Similarly, any of the eight channels is selected twice for the other two sub-frequency bands SB2 and SB3, so the probability that the channel is selected is (1/8) × (2/6) = 1/24.

  In this embodiment and the following embodiments, the channel selection setting is performed using the random number RND. However, a random number table, a transition table indicating random transition of the channel, A channel may be selected and set using a generation formula that generates a random number.

<Embodiment 2>
Next, an RFID system to which Embodiment 2 of the communication frequency setting method of the present invention is applied will be described. The RFID system of the present embodiment has the same configuration as that of the system of FIG. 1, and the sub frequency band dividing method and the sub frequency band and channel selecting methods are different.

  In this embodiment, as shown in FIG. 5A, the communication frequency band BB of 2402 MHz to 2425 MHz is divided into five sub-frequency bands SB1, SB2, SB3, SB4, and SB5, corresponding to channel frequencies 2402 to 2425 MHz. Twenty-four channels 02Ch to 25Ch are allocated to five sub-frequency bands SB1 to SB5.

  Three channels 02Ch to 04Ch are allocated to the lowest frequency side sub-frequency band SB1. Similarly, three channels 23Ch to 25Ch are also allocated to the sub-frequency band SB5 on the highest frequency side.

  Further, six channels are allocated to each of the other sub-frequency bands SB2, SB3, and SB4.

  Therefore, the sub-frequency band SB1 on the lowest frequency side and the sub-frequency band SB5 on the highest frequency side are narrow, and the other sub-frequency bands SB2, SB3, and SB4 are wide.

  When the sub-frequency band SB1 on the lowest frequency side is narrowed in this way, the maximum transition width of the communication frequency f is narrower at 8 MHz between the sub-frequency band SB1 and the sub-frequency band SB2, and between the sub-frequency bands SB1 and SB2 At the time of transition of the communication frequency f, it is possible to further suppress spurious radio waves generated outside the communication frequency band BB on the lower frequency side.

  Similarly, if the sub-frequency band SB5 on the highest frequency side is narrowed, the maximum transition width of the communication frequency f is 8 MHz which is narrower between the sub-frequency band SB4 and the sub-frequency band SB5. The spurious of the radio wave generated outside the side can be further suppressed. For this reason, communication of another communication system using a communication frequency outside the communication frequency band BB is not disturbed.

  Since the maximum transition width between the sub-frequency bands SB2 and SB3 and the maximum transition width between the sub-frequency bands SB3 and SB4 are 11 MHz, a slight amount of radio wave spurious is generated in the communication frequency band BB. However, some spurious in the communication frequency band BB is allowed because it does not interfere with communication of other communication systems.

  Next, the control process for hopping the communication frequency in this embodiment will be described with reference to the flowcharts of FIGS. 3 and 6.

  First, the control unit 11 initially sets the order index STEP to a value 1 (step S101), and then proceeds to the routine shown in the sub-flowchart of FIG. 6 (step S102).

  In the sub-flowchart routine, the control unit 11 refers to the value 1 of the order index STEP set in step S101, and selects the sub-frequency band SB1 corresponding to the value 1 of the order index STEP (step S301). The lowest frequency side channel 02Ch in the sub frequency band SB1 is set as the minimum channel Chmin in the sub frequency band, and the value 03 is set as the number N of channels in the sub frequency band SB1 (step S302). And it returns to step S103 of the flowchart of FIG.

  Next, the control unit 11 substitutes the channel 02Ch and the value 03 set in step S302 for the minimum channel Chmin and the number of channels N in the sub-frequency band in the above equation (1), and further obtains and substitutes the random number RND. Ch is obtained (step S103).

  Subsequently, the control unit 11 substitutes the channel Ch obtained in step S103 into the above equation (2) to obtain the next communication frequency f (step S104).

  Then, the control unit 11 divides the communication frequency f obtained in step S104 by the frequency 1 MHz of the reference input signal S1 output from the reference frequency divider 22 to obtain the division ratio of the communication frequency divider 26. (Step S105), this frequency division ratio is instructed to the communication frequency divider 26.

  Thereby, the frequency of the carrier wave signal Sm is controlled to the next communication frequency f obtained in step S104, and the next communication frequency f is set.

  At this time, the control unit 11 waits for a certain time necessary for the communication frequency f to transition with the maximum transition width (11 MHz) from the time when the frequency division ratio is instructed. And the control part 11 will transmit / receive transmission data and reception data, if fixed time passes (each step S106, S107).

  Thereafter, the control unit 11 adds 1 to the order index STEP set in step S101 to update the order index STEP to the value 2 (step S108), and the value 2 of the order index STEP is set to the cyclic index M (= 8). ) After confirming the following (“No” in step S109), the process returns to step S102 and proceeds to the routine shown in the sub-flowchart of FIG.

  Next, the sub frequency band SB2 corresponding to the value 2 of the order index STEP set in step S108 is selected (step S301), and the lowest frequency channel 05Ch in the sub frequency band SB2 is set as the minimum channel in the sub frequency band Chmin. The value 06 is set as the number of channels N in the sub-frequency band SB2 (step S303), and the process returns to step S103 in the flowchart of FIG.

  In this case, the channel 05Ch and the value 08 set in step S303 are substituted into the above equation (1), the random number RND is obtained and substituted, and any of the channels 05Ch to 10Ch in the sub-frequency band SB2 is randomly selected. (Step S103), the channel Ch set in step S103 is substituted into the above equation (2) to obtain the next communication frequency f (step S104), which corresponds to the communication frequency f obtained in step S104. A frequency division ratio is obtained (step S105), the frequency division ratio is instructed to the communication frequency divider 26, and the next communication frequency f obtained in step S104 is set.

  The transmission data and the reception data are transmitted / received after a certain time required for the communication frequency f to transition with the maximum transition width has elapsed (steps S106 and S107).

  Further, 1 is added to the order index STEP, the order index STEP is updated to the value 3 (step S108), and it is confirmed that the value 3 of the order index STEP is equal to or less than the round index M (= 8) ( "No" in step S109), the process returns to step S102, and proceeds to the routine shown in the sub-flowchart of FIG.

  Thereafter, the same processing is repeated. In the routine shown in the sub-flowchart of FIG. 6, since the order index STEP set in step S108 is the value 3, the sub frequency band SB3 corresponding to the value 3 of the order index STEP is selected (step S301), and the sub frequency The in-band minimum channel Chmin (channel 11Ch) and the number of channels N (value 06) are set (step S304), and the process returns to step S103 in the flowchart of FIG. Then, the channel frequency in the sub-frequency band SB3 is set randomly (step S103), the next communication frequency f is obtained (step S104), the frequency division ratio is obtained (step S105), and the next communication frequency f is set. Is done. Thereafter, transmission data and reception data are transmitted and received (steps S106 and S107).

  Subsequently, the order index STEP is updated to the value 4 (step S108), and it is confirmed that the value 4 of the order index STEP is equal to or less than the cyclic index M (= 8) (“No” in step S109). Returning to S102, the process proceeds to the sub-flowchart of FIG. Then, the sub-frequency band SB4 corresponding to the value 4 of the order index STEP is selected (step S301), and the sub-frequency band minimum channel Chmin (channel 17Ch) and the number of channels N (value 06) are set (step S305). Returning to step S103 of the flowchart of FIG. Further, the channel frequency in the sub-frequency band SB4 is set randomly (step S103), the next communication frequency f is obtained (step S104), the frequency division ratio is obtained (step S105), and the next communication frequency f is set. Is done. Thereafter, transmission data and reception data are transmitted and received (steps S106 and S107).

  Subsequently, the order index STEP is updated to the value 5 (step S108), and it is confirmed that the value 5 of the order index STEP is equal to or less than the cyclic index M (= 8) (“No” in step S109). Returning to S102, the process proceeds to the sub-flowchart of FIG. Then, the sub frequency band SB5 corresponding to the value 5 of the order index STEP is selected (step S301), and the sub-frequency band minimum channel Chmin (channel 23Ch) and the number of channels N (value 03) are set (step S306). Returning to step S103 of the flowchart of FIG. Further, the channel frequency in the sub-frequency band SB5 is set randomly (step S103), the next communication frequency f is obtained (step S104), the frequency division ratio is obtained (step S105), and the next communication frequency f is set. Is done. Thereafter, transmission data and reception data are transmitted and received (steps S106 and S107).

  In the same manner, each time the order index STEP is sequentially updated with the values 6, 7, and 8, the processes of steps S102 to S110 and the process of the sub-flowchart of FIG. 6 are repeated, and each sub-frequency band SB4, SB3, SB2 is sequentially selected, the channel frequency in the selected sub frequency band is set at random, and the next communication frequency f is set. When the order index STEP is updated to the value 9 (step S108), the order index STEP value 9 is not less than or equal to the cyclic index M (= 8) (“Yes” in step S109), and therefore communication is not completed. Is confirmed (“No” in step S110), the process returns to step S101, and the order index STEP is initialized to a value of 1.

  Accordingly, the sub frequency bands SB1 to SB5 are repeatedly selected in the order of SB1, SB2, SB3, SB4, SB5, SB4, SB3, and SB2, as shown in FIG. 5B, and the sub frequency bands are selected. Each time, the channel frequency in the sub-frequency band is randomly selected.

  In the sub-frequency band SB1 on the lowest frequency side and the sub-frequency band SB5 on the highest frequency side, one of the three channels is selected at random. Further, in each of the other sub-frequency bands SB2, SB3, and SB4, one of the six channels is selected at random.

  Since the sub frequency bands are sequentially selected in this order, the channel selection probabilities are equal in each sub frequency band, and the selection probabilities of all the channels are equal. The bias can be suppressed. When one of the three channels in the sub-frequency band SB1 is selected once when the order index STEP is sequentially stepped from the value 1 to the value 8, one of the three channels in the sub-frequency band SB1 is selected, so the probability that the channel in the sub-frequency band SB1 is selected Is (1/3) × (1/8) = 1/24. Similarly, since any of the three channels in the sub frequency band SB5 is selected once, the probability that the channel in the sub frequency band SB5 is selected is (1/3) × (1/8) = 1 / 24. For the other three sub-frequency bands SB2, SB3, and SB4, since any of the six channels is selected twice, the probability that the channel is selected is (1/6) × (2/8) = 1/24, and the same probability is obtained in any sub-frequency band.

  Furthermore, even if a communication failure occurs in one sub-frequency band, communication can be continued as long as the communication frequency transitions between the other sub-frequency bands, so that the amount of data that can be transmitted and received is guaranteed. Can do.

  On the other hand, when the communication frequency band is not divided into a plurality of sub-frequency bands, it is not known at all when the communication frequency is set in the frequency zone where the communication failure occurs, so that the amount of data that can be transmitted and received can be guaranteed. Can not.

<Embodiment 3>
Next, an RFID system to which Embodiment 3 of the communication frequency setting method of the present invention is applied will be described. The RFID system of the present embodiment has the same configuration as that of the system of FIG. 1, and the sub frequency band dividing method and the sub frequency band and channel selecting methods are different.

  In this embodiment, the communication frequency band BB of 2402 MHz to 2425 MHz is divided into five sub frequency bands SB1, SB2, SB3, SB4, and SB5 as shown in FIG.

  Then, four channels 02Ch to 05Ch and four channels 06Ch to 10Ch are allocated to the first sub-frequency band SB1 and the second sub-frequency band SB2 from the low frequency side, respectively. Similarly, the four channels 22Ch to 25 and the four channels 18Ch to 21Ch are allocated to the first sub frequency band SB5 and the second sub frequency band SB4 from the high frequency side, respectively. In addition, eight channels 10Ch to 17Ch are allocated to the central sub-frequency band SB3.

  Therefore, the sub frequency bands SB1 and SB2 from the lowest frequency side to the second are narrow, the sub frequency bands SB4 and SB5 from the highest frequency side to the second are narrow, and only the central sub frequency band SB3 is wide. ing.

  For this reason, the maximum transition width of the communication frequency f is 7 MHz which is narrower between the sub-frequency bands SB1 and SB2 from the lowest frequency side to the second sub-frequency band SB4 and SB5. The maximum transition width of the communication frequency f between them is 7 MHz which is narrower, so that spurious radio waves generated outside the communication frequency band BB can be reliably suppressed, and communication of other communication systems can be prevented.

  Next, a control process for hopping the communication frequency in the present embodiment will be described with reference to the flowcharts of FIGS. 3 and 8.

  First, after the order index STEP is initially set to the value 1 (step S101), the routine proceeds to the routine shown in the sub-flowchart of FIG. 6 (step S102).

  Then, the sub frequency band SB1 corresponding to the value 1 of the order index STEP set in step S101 is selected (step S401), and the lowest frequency channel 02Ch in the sub frequency band SB1 is set as the minimum channel in the sub frequency band Chmin. Then, the number N of channels in the sub-frequency band SB1 is set to a value 04 (step S402), and the process returns to step S103 in the flowchart of FIG.

  Further, the channel 02Ch and the value 04 set in step S402 are substituted into the above equation (1), and the random number RND is obtained and substituted, and any of the channels 02Ch to 05Ch in the sub-frequency band SB1 is set at random. (Step S103), the channel Ch set in Step S103 is substituted into the above equation (2) to obtain the next communication frequency f (Step S104), and the frequency division corresponding to the communication frequency f obtained in Step S104 The ratio is obtained (step S105), the frequency division ratio is instructed to the communication frequency divider 26, and the next communication frequency f is set to the channel frequency corresponding to the instructed frequency division ratio.

  Thereafter, transmission data and reception data are transmitted and received after a certain time required for the communication frequency f to transition with the maximum transition width (11 MHz) (steps S106 and S107).

  Then, 1 is added to the order index STEP, the order index STEP is updated to the value 2 (step S108), and it is confirmed that the value 2 of the order index STEP is equal to or less than the cyclic index M (= 12) ( "No" in step S109), the process returns to step S102, and proceeds to the routine shown in the sub-flowchart of FIG.

  Next, the sub frequency band SB2 corresponding to the value 2 of the order index STEP set in step S108 is selected (step S401), and the sub-frequency band minimum channel Chmin (channel 06Ch) and the number of channels N (value 08) are selected. The setting is made (step S403), and the process returns to step S103 in the flowchart of FIG. Then, the channel frequency in the sub-frequency band SB2 is randomly set (step S103), the next communication frequency f is obtained (step S104), the division ratio is obtained (step S105), and the frequency division ratio corresponds to this division ratio. The next communication frequency f is set as the channel frequency. Thereafter, transmission data and reception data are transmitted and received (steps S106 and S107).

  Subsequently, the order index STEP is updated to the value 3 (step S108), and it is confirmed that the value 3 of the order index STEP is equal to or less than the cyclic index M (= 12) (“No” in step S109). It returns to S102 and moves to the sub flowchart of FIG. Then, the sub-frequency band SB3 corresponding to the value 3 of the order index STEP is selected (step S401), and the sub-frequency band minimum channel Chmin (channel 10Ch) and the number of channels N (value 08) are set (step S404). Returning to step S103 of the flowchart of FIG. Further, the channel frequency in the sub-frequency band SB3 is set randomly (step S103), the next communication frequency f is obtained (step S104), the frequency division ratio is obtained (step S105), and the next communication frequency f is set. Is done. Thereafter, transmission data and reception data are transmitted and received (steps S106 and S107).

  Subsequently, when the order index STEP is updated to the value 4 (step S108), exactly the same processing as when the order index STEP is the value 3 is repeated, the sub-frequency band SB3 is selected, and the next communication frequency f Is set, and transmission data and reception data are transmitted and received.

  Therefore, in the sub frequency band SB3, channel selection is performed twice in succession.

  Further, the order index STEP is updated to the value 5 (step S108), and it is confirmed that the value 5 of the order index STEP is equal to or less than the cyclic index M (= 12) (“No” in step S109). Returning to FIG. 8, the process proceeds to the sub-flowchart of FIG. Then, the sub frequency band SB4 corresponding to the value 5 of the order index STEP is selected (step S401), and the sub-frequency band minimum channel Chmin (channel 18Ch) and the number of channels N (value 04) are set (step S405). Returning to step S103 of the flowchart of FIG. Further, the channel frequency in the sub-frequency band SB4 is set randomly (step S103), the next communication frequency f is obtained (step S104), the frequency division ratio is obtained (step S105), and the next communication frequency f is set. Is done. Thereafter, transmission data and reception data are transmitted and received (steps S106 and S107).

  Subsequently, the order index STEP is updated to the value 6 (step S108), and it is confirmed that the value 6 of the order index STEP is equal to or less than the cyclic index M (= 12) (“No” in step S109). It returns to S102 and moves to the sub flowchart of FIG. Then, the sub-frequency band SB5 corresponding to the value 6 of the order index STEP is selected (step S401), and the sub-frequency band minimum channel Chmin (channel 22Ch) and the number of channels N (value 04) are set (step S406). Returning to step S103 of the flowchart of FIG. Further, the channel frequency in the sub-frequency band SB5 is set randomly (step S103), the next communication frequency f is obtained (step S104), the frequency division ratio is obtained (step S105), and the next communication frequency f is set. Is done. Thereafter, transmission data and reception data are transmitted and received (steps S106 and S107).

  In the same manner, each time the order index STEP is sequentially updated with the values 7 to 12, the processes of steps S102 to S110 and the process of the sub-flowchart of FIG. 8 are repeated, and each sub-frequency band SB5, SB4, SB3, SB3, SB2, and SB1 are sequentially selected, the channel frequency in the selected sub frequency band is set at random, and the next communication frequency f is set. When the order index STEP is updated to the value 13 (step S108), the order index STEP value 13 is not less than or equal to the cyclic index M (= 12) (“Yes” in step S109), and therefore communication is not completed. Is confirmed (“No” in step S110), the process returns to step S101, and the order index STEP is initialized to a value of 1.

  Accordingly, each of the sub-frequency bands SB1 to SB5 is repeatedly selected in the order of SB1 → SB2 → SB3 → SB3 → SB4 → SB5 → SB5 → SB4 → SB3 → SB3 → SB2 as shown in FIG. 7B. .

  In each of the sub frequency bands SB1 and SB2 from the lowest frequency side to the second, any one of the four channels is selected at random. Similarly, any of the four channels is selected at random in the sub-frequency bands SB4 and SB5 from the second highest frequency side. In the central sub-frequency band SB3, any of the eight channels is randomly selected, and the channel selection is performed twice in succession.

  When sub frequency bands are selected in this order, the channel selection probabilities are equal in all sub frequency bands, and the selection probabilities of all channels are also equal. Can be suppressed. When the order index STEP is sequentially incremented from the value 1 to the value 12, one of the four channels in each sub-frequency band SB1, SB2, SB4, and SB5 is selected twice, so that the channel is selected. The probability is (1/4) × (2/12) = 1/24. For the central sub-frequency band SB3, since any of the eight channels is selected four times, the probability that the channel is selected is (1/8) × (4/12) = 1/24. The same probability is obtained in any sub-frequency band.

  Even if a communication failure occurs in one sub-frequency band, communication can be continued as long as the communication frequency transitions between the other sub-frequency bands.

<Embodiment 4>
Next, an RFID system to which Embodiment 4 of the communication frequency setting method of the present invention is applied will be described. The RFID system of the present embodiment has the same configuration as that of the system of FIG. 1, and the sub frequency band dividing method and the sub frequency band and channel selecting methods are different.

  In this embodiment, as shown in FIG. 9A, the communication frequency band BB of 2402 MHz to 2425 MHz is divided into three sub-frequency bands SB1, SB2, and SB3, and 24 channels 02Ch to Ch25 are divided into three pieces of eight. The sub frequency bands SB1 to SB3 are evenly allocated.

  Each sub-frequency band SB1 to SB3 is repeatedly selected in the order of SB1 → SB2 → SB3 → SB2 as shown in FIG. 9B, and every time the sub-frequency band is selected, A channel frequency is selected at random, and the communication frequency f is set to the selected channel frequency.

However, when sub-frequency bands are selected in this order, the selection probabilities of the sub-frequency bands SB1 and SB3 on both sides are ½ of the selection probabilities of the central sub-frequency band SB2. Channel selection is performed four times while each of the sub-frequency bands SB1 to SB3 makes a round, and any one of the eight channels in the sub-frequency bands SB1 and SB3 on both sides is selected once. 1/8) × (1/4) = 1/32. In addition, since any of the eight channels in the sub-frequency band SB2 is selected twice, the channel selection probability is (1/8) × (2/4) = 1/16. In this case, the communication time when the channels in the sub frequency bands SB1 and SB3 on both sides are selected is set to be twice the communication time when the channel in the center sub frequency band SB2 is selected. Thereby, the communication power of all the channel frequencies becomes equal, and the bias of the communication power density in the communication frequency band can be prevented.

  Next, the control process for hopping the communication frequency in this embodiment will be described with reference to the flowcharts of FIGS. 10 and 11. Note that, in the flowchart of FIG. 10, steps in which the same processing as in the flowchart of FIG. 3 is performed are denoted by the same reference numerals.

  First, the control unit 11 initializes the order index STEP to a value 1 (step S101), and then proceeds to a routine shown in the sub-flowchart of FIG. 11 (step S102).

  In the routine of this sub-flowchart, the control unit 11 refers to the value 1 of the order index STEP set in step S101, selects the sub frequency band SB1 corresponding to the value 1 of this order index STEP (step S501), The channel 02Ch on the lowest frequency side in the sub frequency band SB1 is set as the minimum channel Chmin in the sub frequency band, and the value 08 is set as the number of channels N in the sub frequency band SB1 (step S502). And it returns to step S103 of the flowchart of FIG.

  Next, the control unit 11 substitutes the channel 02Ch and the value 03 set in step S502 for the minimum channel Chmin and the number N of channels in the sub-frequency band in the above equation (1), obtains and substitutes the random number RND, and sets the channel Ch. Is obtained (step S103).

  Subsequently, the control unit 11 substitutes the channel Ch obtained in step S103 into the above equation (2) to obtain the next communication frequency f (step S104).

  And the control part 11 calculates | requires a frequency division ratio by dividing the communication frequency f calculated | required by step S104 by the frequency 1MHz of the reference | standard input signal S1 (step S105).

  Further, the control unit 11 selects the sub-frequency band SB1 corresponding to the value 1 of the order index STEP set in step S101 (step S111), and sets the communication time to 2T (step S112).

  Thereafter, the control unit 11 instructs the communication frequency divider 26 on the frequency division ratio obtained in step S105. Thereby, the frequency of the carrier wave signal Sm is set to the next communication frequency f obtained in step S104.

  The control unit 11 waits for a certain time required for the communication frequency f to transition with the maximum transition width (15 MHz) from the time when the division ratio is instructed, and when the certain time has elapsed, the communication time 2T set in step S112. Only the communication is continuously performed, and transmission data and reception data are transmitted and received (steps S106 and S107).

  Thereafter, the control unit 11 adds 1 to the order index STEP set in step S101 to update the order index STEP to the value 2 (step S108), and the value 2 of the order index STEP becomes the cyclic index M (= 4). ) After confirming the following (“No” in step S109), the process returns to step S102 and proceeds to the routine shown in the sub-flowchart of FIG.

  Next, the sub frequency band SB2 corresponding to the value 2 of the order index STEP set in step S108 is selected (step S501), and the sub-frequency band minimum channel Chmin (channel 10Ch) and the number of channels N (value 08) are set. (Step S503), the process returns to Step S103 of the flowchart of FIG. Then, the channel frequency in the sub-frequency band SB2 is set at random (step S103), the next communication frequency f is obtained (step S104), and the frequency division ratio is obtained (step S105).

  Further, the sub frequency band SB2 corresponding to the value 2 of the order index STEP set in step S108 is selected (step S111), and the communication time is set to T (step S113).

  Thereafter, the frequency division ratio obtained in step S105 is instructed to the communication frequency divider 26, and the frequency of the carrier signal Sm is set to the next communication frequency f obtained in step S104.

  Then, after a certain time has elapsed, communication is continuously performed for the communication time T set in step S113, and transmission data and reception data are transmitted and received (steps S106 and S107).

  Further, 1 is added to the order index STEP, the order index STEP is updated to the value 3 (step S108), and it is confirmed that the value 3 of the order index STEP is less than or equal to the round index M (= 4) ( “No” in step S109), the process returns to step S102, and proceeds to the routine shown in the sub-flowchart of FIG.

  Next, the sub-frequency band SB3 corresponding to the value 3 of the order index STEP is selected (step S501), and the sub-frequency band minimum channel Chmin (channel 18Ch) and the number of channels N (value 08) are set (step S504). ), The process returns to step S103 of the flowchart of FIG. Then, the channel frequency in the sub-frequency band SB3 is set at random (step S103), the next communication frequency f is obtained (step S104), and the frequency division ratio is obtained (step S105).

  Further, the sub frequency band SB3 corresponding to the value 3 of the order index STEP is selected (step S111), and the communication time is set to 2T (step S114).

  Thereafter, the frequency division ratio is instructed to the communication frequency divider 26, and the next communication frequency f is set. Then, after a certain time has elapsed, communication is continuously performed for the communication time 2T, and transmission data and reception data are transmitted and received (steps S106 and S107).

  Further, the order index STEP is updated to the value 4 (step S108), and it is confirmed that the value 4 of the order index STEP is equal to or less than the cyclic index M (= 4) (“No” in step S109). Returning to FIG. 11, the routine proceeds to the routine shown in the sub-flow chart of FIG.

  When the order index STEP is 4, the same processing as when the order index STEP is 2 is performed. Accordingly, the sub frequency band SB2 is selected (step S501), the sub-frequency band minimum channel Chmin and the number of channels N are set (step S503), and the process returns to step S103 in the flowchart of FIG. Then, the channel frequency is set at random (step S103), the next communication frequency f is obtained (step S104), and the frequency division ratio is obtained (step S105).

  Further, the sub frequency band SB2 is selected (step S111), and the communication time is set to T (step S114).

  Then, the division ratio is instructed, the next communication frequency f is set, and after a predetermined time has elapsed, communication is continuously performed for the communication time T, and transmission data and reception data are transmitted and received ( Steps S06 and S107).

  Subsequently, when the order index STEP is updated to the value 5 (step S108), the value 5 of the order index STEP is not less than the one-round index M (= 4) (“Yes” in step S109), so communication is not completed. (No in step S110), the process returns to step S101, and the order index STEP is initialized to a value of 1.

  Thereafter, the same processing is repeated. Accordingly, each of the sub-frequency bands SB1 to SB5 is repeatedly selected in the order of SB1, SB2, SB3, SB2, SB1, SB2, as shown in FIG. 9B. For this reason, the selection probability of the sub-frequency bands SB1 and SB3 on both sides is ½ of the selection probability of the central sub-frequency band SB2.

  However, the communication time 2T is selected when the channels in the sub-frequency bands SB1 and SB3 on both sides are selected, and the communication time T is selected when the channel in the center sub-frequency band SB2 is selected. The communication time in the bands SB1 and SB3 is twice the communication time in the central sub-frequency band SB2, and the communication power density in the communication frequency band is not biased.

  For example, when a channel is hopped every 1/100 seconds, the communication time is 2/100 seconds when the channels in the sub-frequency bands SB1 and SB3 on both sides are selected, and the channel in the center sub-frequency band SB2 is When selected, the communication time is 1/100 second.

  In addition, this invention is not limited to said each embodiment, It can deform | transform variously. For example, although a batteryless passive type is illustrated as a wireless tag, the present invention can be applied to a passive type having a battery or an active type.

  Further, the present invention can be applied not only to the RFID system but also to other wireless communication systems such as a mobile phone that hops the communication frequency.

It is a block diagram which shows the RFID system to which Embodiment 1 of the communication frequency setting method of this invention is applied. (A) is a figure which shows the division | segmentation method of the communication frequency band in the RFID system of Embodiment 1, (b) is a figure which shows the selection order of a sub frequency band. 3 is a flowchart illustrating communication frequency hopping control by the RFID system according to the first embodiment. FIG. 4 is a sub-flowchart showing processing of one step in the flowchart of FIG. 3. (A) is a figure which shows the division | segmentation method of the communication frequency band in the RFID system of Embodiment 2, (b) is a figure which shows the selection order of a sub frequency band. 10 is a sub-flowchart showing a part of communication frequency hopping control by the RFID system of the second embodiment. (A) is a figure which shows the division | segmentation method of the communication frequency band in the RFID system of Embodiment 3, (b) is a figure which shows the selection order of a sub frequency band. 10 is a sub-flowchart showing a part of communication frequency hopping control by the RFID system of the third embodiment. (A) is a figure which shows the division | segmentation method of the communication frequency band in the RFID system of Embodiment 4, (b) is a figure which shows the selection order of a sub frequency band. 10 is a flowchart illustrating communication frequency hopping control by the RFID system according to the fourth embodiment. FIG. 11 is a sub-flowchart showing processing of one step in the flowchart of FIG. 10.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reader writer 2 Wireless tag 11 Control part 12 PLL circuit 13 Transmission circuit 14 Reception circuit 15 Circulator 16 Antenna 21 Reference oscillator 22 Reference frequency divider 23 Phase comparator 24 Loop filter 25 Voltage control oscillator 26 Communication frequency divider

Claims (5)

In the communication frequency setting method for wireless communication performed while hopping the communication frequency,
The communication frequency band used for the wireless communication is divided into three or more sub-frequency bands that do not overlap each other , and a plurality of channel frequencies are set in each of the sub-frequency bands,
When one of the sub-frequency bands is selected and one channel frequency included in the selected sub-frequency band is set as the communication frequency, the next communication frequency is set to the selected sub-frequency band or the selected sub-frequency band. A communication frequency setting method for wireless communication, which is randomly set to any one of channel frequencies included in another sub-frequency band adjacent to the sub-frequency band .   2. The sub-frequency band on the highest frequency side and the sub-frequency band on the lowest frequency side of each of the sub-frequency bands have a smaller number of channel frequencies allocated than other sub-frequency bands. A communication frequency setting method for wireless communication described in 1.   2. The communication frequency setting method for wireless communication according to claim 1, wherein the set frequency of the channel frequency in the sub frequency band is set according to the number of channel frequencies in the sub frequency band.   2. The communication frequency setting method for wireless communication according to claim 1, wherein a communication time in the sub frequency band is set according to the number of channel frequencies in the sub frequency band.   Of each of the sub-frequency bands, each sub-frequency band from the highest frequency side to the second sub-frequency band and each sub-frequency band from the lowest frequency side to the second sub-frequency band is the number of channel frequencies allocated to other sub-frequency bands. The communication frequency setting method of wireless communication according to claim 1, wherein the communication frequency is low.

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