JP3979309B2 - Communication system responder and communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a responder and a communication system of a communication system in which an interrogator transmits an interrogation wave, and a plurality of transponders receiving the interrogation wave reflect reply information back to the interrogator.
[0002]
[Prior art]
A communication system is known in which a main carrier is sent from an interrogator to a plurality of transponders, and the responder that has received the main carrier returns a reflected wave signal that has been modulated with respect to the main carrier by means of response device identification signal information or the like to the interrogator. It has been. In this communication system, it is possible to manufacture a responder at low cost, and in particular, a communication system having a large number of responders is excellent in cost performance. However, in this communication system, interference of a large number of reflected wave signals that are replies from a large number of responders becomes a problem. In this regard, a plurality of time slots, which are time frames in which the responder returns the reflected signal, are provided, and each responder uses a different time slot to return the reflected signal, and the reflected signal returned from the responder is modulated. There has been proposed a communication system that avoids interference between reflected signals by a method that uses frequency hopping in which subcarrier frequencies are divided and multiplexed and hopping is performed by randomly selecting a subcarrier frequency for each reply (for example, Patent Document 1). reference).
[0003]
[Patent Document 1]
JP 2000-49658 A
[0004]
[Problems to be solved by the invention]
However, in the method of providing a plurality of time slots, when there are a large number of responders, there is a problem that it takes a long time to complete communication with all the responders.
Further, in the method of multiplexing the subcarriers using frequency hopping, the time for completing the communication between the interrogator and all the transponders is shortened. However, the reflected signal from the transponder located far from the interrogator may be interfered by the reflected signal from the transponder located near the interrogator, or the harmonic signal of the reflected signal. There is a problem that even the presence of a reflected signal from a transponder at a remote position cannot be recognized. In other words, when multiple responders return reflected signals using the same subcarrier frequency, the interrogator cannot correctly demodulate if the intensity of the reflected signals is approximately the same. It is possible to request retransmission, but the reflected signal from the transponder located far from the interrogator interferes with the reflected signal from the transponder located closer to the interrogator or the harmonic signal of the reflected signal. In this case, it is possible to correctly demodulate the reflected signal from the responder in the near position, so that the interrogator does not request retransmission and recognizes the reflected signal from the responder in the far position. Can not do it.
[0005]
The present invention provides a communication system that can communicate a reflected wave from a transponder far from the interrogator without being interfered by a reflected wave from a transponder close to the interrogator or a harmonic. An object is to provide a transponder and a communication system.
[0006]
[Means for Solving the Problems]
The responder of the communication system according to claim 1, wherein an interrogator including a main carrier is transmitted from an interrogator, and the responder that has received the main carrier modulates the main carrier with predetermined information. A responder of a communication system for returning a reflected wave to an interrogator, comprising: distance detection means for detecting a distance between the interrogator and the responder; and the interrogation wave including a main carrier transmitted from the interrogator. The main carrier wave receiving / reflecting means for receiving and reflecting, the information creating means for creating information to be transmitted from the responder, and the frequency band of the modulation signal for modulating the reflected wave reflected by the main carrier wave receiving / reflecting means, the distance A band determining unit that determines based on the distance detected by the detecting unit; and the information generating unit that creates the frequency band of the modulated signal to be a frequency band determined by the band determining unit. Characterized in that it comprises a modulation signal generating means for generating the modulated signal based on the information.
According to this configuration, since the frequency band of the modulation signal is set based on the distance between the interrogator and the responder, the distance is often different. As a result, the frequency of the reflected wave of each responder is dispersed, Interference of reflected waves between responders can be reduced.
[0007]
The transponder of the communication system according to claim 2 is characterized in that the band determination unit increases the frequency band of the modulation signal as the distance detected by the distance detection unit decreases.
According to this configuration, in order to increase the frequency band of the modulated signal of the reflected wave returned from the responder located close to the interrogator, the reflected wave returned from the responder located far away is the response located near Interference from the fundamental wave or harmonics of the reflected wave returned from the instrument.
[0008]
The responder of the communication system according to claim 3, Obi The area determining means calculates the frequency band from a distance detected by the distance detecting means by a predetermined relational expression.
According to this configuration, since the relationship between the distance and the frequency band is determined by a mathematical expression, the frequency band can be obtained simply and accurately, and the memory capacity can be reduced.
[0009]
The responder of the communication system according to claim 4, Obi The area determining means determines the frequency band based on a correspondence table between the frequency band and the distance detected by the distance detecting means.
According to this configuration, since the relationship between the distance and the frequency band is determined as a table, the frequency band can be determined by simple processing.
[0010]
The responder of the communication system according to claim 5 Obi The range determining means is configured to randomly or for each responder select the frequency band from the group of the frequency bands selected based on the correspondence table between the grouped frequency bands and the distance detected by the distance detecting means. It is determined based on a unique definition.
According to this configuration, since the frequency band of the modulated signal of the reflected wave is changed in each responder, the probability that the responses of the responders interfere with each other when a plurality of responders exist at the same distance may be reduced. it can.
[0011]
The responder of the communication system according to claim 6, wherein the modulation Signal generation The means is characterized in that a plurality of transmission time frames are set, and in which transmission time frame modulation is performed is determined based on a random or unique definition for each responder.
According to this configuration, since the transmission time frame of the reflected wave is changed in each responder, it is possible to further reduce the probability of interference between the responders even when a plurality of responders exist at the same distance. .
[0012]
8. The responder of the communication system according to claim 7, wherein the modulation Signal generation The means does not change the frequency band determined by the band determination means until the transmission of the information is completed.
According to this configuration, the frequency band of the modulated signal of the reflected wave is not changed until the response of the responder is completed, so that the demodulation by the interrogator can be performed accurately.
[0013]
9. The responder of the communication system according to claim 8, further comprising a charging unit that takes out the power of the interrogation wave and performs charging, and the charging unit has power accumulated in the responder exceeding a predetermined capacity. Then, each means of the responder is operated to respond to the interrogation wave.
According to this configuration, since it is not necessary to provide a power source for the responder, the responder can be reduced in size and weight. Further, since the responder does not operate until the predetermined capacity or more is stored, a stable reply can be performed.
In addition, since the reception strength varies depending on the distance between the interrogator and the transponder, the charging time varies, and the time until charging is naturally distributed among the transponders. Disperse and reduce interference.
[0014]
The responder of the communication system according to claim 9, wherein the distance detection unit is configured such that, in the charging unit, a change amount per unit time of the voltage or power to be charged, or a predetermined amount of the voltage or power to be charged. The distance between the interrogator and the responder is detected based on the time when the change is obtained.
According to this configuration, since the distance is detected based on the voltage and power to be charged, the distance can be detected while charging, and the distance between the interrogator and the responder is determined not by the physical length but by the path length. A distance in accordance with the actual positional relationship limited by the passage can be detected.
[0015]
The responder of the communication system according to claim 10 is characterized in that the distance detecting means detects a distance from the intensity of the interrogation wave.
According to this configuration, since the distance is detected based on the intensity of the interrogation wave, the distance can be easily detected, and the distance between the interrogator and the responder is determined not by the physical length but by the path length, A distance in accordance with the actual positional relationship limited by the passage can be detected.
[0016]
12. The communication system according to claim 11, wherein the interrogator uses the interrogator and the response from the intensity of the modulated signal obtained from the modulated reflected wave returned from the responder that has received the interrogation wave. Interrogator distance detecting means for detecting the distance to the receiver, and distance information transmitting means for transmitting the distance information to the responder, wherein the responder receives the distance information by the main carrier reception reflecting means. The distance detecting means detects the distance between the interrogator and the responder from the distance information.
According to this configuration, since the distance between the interrogator and the responder can be detected on the interrogator side, the burden on the responder side can be reduced and the configuration of the responder can be simplified.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
<First Embodiment>
Hereinafter, a first embodiment according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration example of a communication system 1 according to the first embodiment.
[0018]
As shown in FIG. 1, the communication system 1 includes an interrogator 2 and responders 3a to 3c. In the example of FIG. 1, the responders 3 a to 3 c are arranged in the order of the responder 3 a, the responder 3 c, and the responder 3 b from the order close to the interrogator 2. The communication system 1 transmits an interrogation wave having the main carrier frequency Fc1 from the interrogator 2 to the responders 3a to 3c. When the responders 3 a to 3 c receive the interrogation wave transmitted from the interrogator 2, the responders 3 a to 3 c return the reflected waves of the subcarrier frequencies f <b> 1 to f <b> 3 modulated by the reply information that they have to the interrogator 2. Thus, the communication system 1 is suitable for a system that collects information on each responder itself or information acquired by each responder from the plurality of responders 3 a to 3 c via the interrogator 2. For example, by arranging the interrogator 2 in the store and giving the responders 3a to 3c to the customer, it is possible to acquire the movement route of the customer in the store. In addition, the interrogator 2 is arranged in the factory, and the responders 3a to 3c are connected so as to acquire the status of each apparatus provided in the factory, thereby centrally managing the status of each apparatus in the factory. Is possible. In FIG. 1, one interrogator 2 has three responders 3 a to 3 c. However, the number of the responders 3 a to 3 c can be arbitrarily set depending on the scale of the communication system 1 and the use environment.
[0019]
Hereinafter, the configuration of the interrogator 2 and the responders 3a to 3c constituting the communication system 1 shown in FIG. 1 will be described in order with reference to the drawings.
[0020]
First, the configuration of the interrogator 2 will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the interrogator 2. As shown in FIG. 2, the interrogator 2 includes an analog circuit unit 10, a digital circuit unit 20, and an antenna 17. The analog circuit unit 10 includes an oscillator 11, a modulator 12, a power amplifier 13, a circulator 14, a low noise amplifier (Low Noise Amp: LNA) 15, and a main carrier demodulator 16.
[0021]
The oscillator 11 oscillates a main carrier wave having a frequency such as 900 MHz, 2.45 GHz, and 5 GHz, and outputs the oscillated main carrier wave to the modulator 12. The modulator 12 modulates the main carrier wave inputted from the oscillator 11 by amplitude modulation (Amplitude Shift Keying: ASK) of the ID number of the interrogator 2 itself, and outputs the modulated main carrier wave to the power amplifier 13. The power amplifier 13 amplifies the power of the main carrier modulated by the modulator 12 and outputs it to the circulator 14. The circulator 14 separates the output and the input so that the amplified main carrier after amplification input from the power amplifier 13 is transmitted to the antenna 17 and the radio wave received by the antenna 17 is transmitted to the LNA 15. The amplified modulated main carrier wave (interrogation wave) transmitted to the antenna 17 is radiated from the antenna 17.
[0022]
The LNA 15 amplifies the reflected waves from the responders 3 a to 3 c received by the antenna 17 input from the circulator 14 and outputs the amplified waves to the main carrier demodulator 16. The main carrier demodulator 16 mixes the received signal amplified by the LNA 15 with the signal from the oscillator 11, performs homodyne detection, and outputs it to the band division filter 21 described later of the digital circuit unit 20.
[0023]
The digital circuit unit 20 includes a band division filter 21, a subcarrier demodulator 22, a frame divider 23, a frame sorter 24, a frame coupler 25, a controller 26, and a subcarrier strength comparator 27. Has been. The band division filter 21 A / D converts the received signal homodyne detected by the main carrier demodulator 16 of the analog circuit unit 10 from an analog signal to a digital signal, and the A / D converted received signal is subjected to Fourier transform. The signal is separated into channels corresponding to the hopping frequency by filtering, and the separated signals are converted into time series by inverse Fourier transform to take out each as a modulated subcarrier signal. The subcarrier demodulator 22 and the subcarrier intensity comparator 27 Output to. The subcarrier demodulator 22 demodulates the subcarrier signal separated by the band division filter 21 to generate an original information signal, and outputs it to the frame divider 23. The frame divider 23 separates the output from each channel generated by the subcarrier demodulator 22 into an appropriate frame and outputs it to the frame sorter 24. The frame sorter 24 sorts the frames divided by the frame divider 23 and outputs them to the frame coupler 25. The frame connector 25 concatenates the frames sorted by the frame sorter 24 in time series for each responder and outputs the frames to the controller 26. The subcarrier strength comparator 27 compares the signal strength of the subcarrier signal from the subcarrier signal separated by the band division filter 21 with a predetermined threshold value, and outputs the comparison result to the controller 26. The controller 26 controls the entire interrogator 2.
[0024]
Next, the configuration of the responder 3a will be described with reference to FIG. FIG. 3 is a block diagram showing the configuration of the responder 3a. The configuration of the responders 3b and 3c is substantially the same as that of the responder 3a, and the description of the responder 3a can be applied.
[0025]
As shown in FIG. 3, the responder 3 a includes an antenna (reception reflection means) 31, a modulator / demodulator 32, an information acquisition unit 33, and a digital circuit unit 40. The modem 32 demodulates the interrogation wave received by the antenna 32 and outputs it to the information acquisition unit 33. Also, the modem 32 modulates the interrogation wave with the subcarrier modulated by the subcarrier modulator 46 described later, and returns the modulated wave as a reflected wave from the antenna 31. The information acquisition unit 33 acquires signal strength information from the signal intensity demodulated by the modem 32, signal content information from the signal demodulated by the modem 32, and distance detection unit 42, which will be described later. The signal content information is output to the information creation unit 44 described later.
[0026]
The digital circuit unit 40 includes a controller 41, a subcarrier oscillator 45, and a subcarrier modulator 46 (modulation signal generating means). The subcarrier oscillator 45 oscillates a subcarrier having a frequency determined by a band determination unit 43 described later of the controller 41, and outputs the oscillated subcarrier to the subcarrier modulator 46. The subcarrier modulator 46 modulates the subcarrier input from the subcarrier oscillator 45 by phase modulation (Phase Shift Keying: PSK) based on the information signal created by the information creation unit 44 (to be described later) of the controller 41. The subcarrier is output to the modem 32. The controller 41 controls the responder 3a. The distance detector (distance detector) 42, the band determiner (band determiner) 43, and the information generator (information generator) are functional units. 44 and so on. Note that the subcarrier oscillator 45 and the subcarrier modulator 46 may be configured in software using the clock of the controller 41. Further, subcarrier modulation may be frequency modulation (Frequency Shift Keying: FSK), amplitude modulation (Amplitude Shift Keying), or the like in addition to phase modulation. Further, the subcarrier oscillator 45 and the subcarrier modulator 46 may be provided in the controller 41 and integrated into one chip.
[0027]
Next, each functional unit configured by the controller 41 will be described. The distance detection unit 42 detects the distance between the interrogator 2 and the responder 3 a from the intensity information of the interrogation signal acquired by the information acquisition unit 33. Specifically, the interrogator 2 and the responder are obtained from the intensity of the signal acquired by the information acquisition unit 33 using a correspondence table between the intensity of the grouped signal and the distance between the interrogator 2 and the responder 3a. It detects by selecting the distance with 3a. Then, the distance detection unit 42 outputs the detected distance information between the interrogator 2 and the responder 3a to the band determination unit 43. Instead of using the correspondence table, detection may be performed by calculating the distance between the interrogator 2 and the responder 3a from the signal strength information using a predetermined relational expression.
[0028]
The band determination unit 43 determines the frequency band of the reflected subcarrier and outputs the determined frequency band to the subcarrier oscillator 45 to oscillate the subcarrier. The frequency band of the subcarrier is determined by a frequency hopping method. The frequency hopping method is a method of randomly selecting a subcarrier frequency band from a plurality of frequency bands (channels). The responder 3a hops the frequency band of the subcarrier for each reply by the frequency hopping method. By using the frequency hopping method in this way, it is possible to reduce the possibility that a plurality of reflected waves returned at the same time interfere with each other, and to increase the confidentiality of the returned reply information. However, if the frequency of the subcarrier is hopped over the entire frequency band, as described above, the reflected wave of the responder far from the interrogator 2 is reflected from the responder near the interrogator 2. Or may be interfered by the harmonics of the reflected wave. Therefore, the band determination unit 43 groups the frequency bands to be hopped so that the frequency band of the subcarrier is high when the distance between the interrogator 2 and the responder 3a is short, and the frequency band of the subcarrier is low when the distance is long. To limit.
[0029]
Specifically, using the correspondence table between the distance between the interrogator 2 and the responder 3a and the limited frequency band, from the distance information between the interrogator 2 and the responder 3a detected by the distance detector 42, The frequency band of the subcarrier to be hopped is determined. FIG. 4 shows an example of a correspondence table between the distance between the interrogator 2 and the responder 3a and the limited frequency band. As shown in FIG. 4, the center frequency of the limited frequency band is set to decrease from 300.0 kHz to 10 kHz as the distance between the interrogator 2 and the responder 3a increases from 0.5 m to 0.1 m. Has been. According to this correspondence table, for example, when the distance between the interrogator 2 and the responder 3a detected by the distance detector 42 is 0.6 m, the frequency band to be hopped is from 285.0 kHz to 295.0 kHz. The frequency band of the subcarrier of the reflected wave is determined by hopping within a plurality of channels that are limited and grouped in this frequency band.
[0030]
Instead of using the correspondence table, the frequency band may be calculated from the distance between the interrogator 2 and the responder 3a using, for example, the relational expressions (1) to (3). Further, the relational expression is not limited to the relational expressions (1) to (3), and the relational expression that the frequency band of the subcarrier becomes lower as the distance between the interrogator 2 and the responders 3a to 3c becomes longer. If it is.
f = a / r + b (1)
f = a / r2 + b (2)
f = a / r2 + b / r + c (3)
a, b, c: constant
f: Center value of subcarrier frequency band
r: Distance between the interrogator and the responder
[0031]
In addition, the band determination unit 43 controls the timing of returning the reflected wave by controlling the timing of outputting the determined frequency band to the subcarrier oscillator 45. The timing for returning the reflected wave is determined by setting a plurality of predetermined time frames sufficient to complete one reply and randomly selecting a time frame for replying from the plurality of time frames. To do. In addition, you may make it select the time frame to reply in accordance with the order prescribed | regulated previously.
[0032]
The information creation unit 44 reads the reply information stored in a memory (not shown) provided in the controller 41 based on the signal content information of the interrogation wave acquired by the information acquisition unit 33 and outputs it to the subcarrier modulator 46. To do. The reply information may be read from an external device connected to the responder 3a.
[0033]
Next, refer to FIG. 5 for details of the circuit configuration of the demodulating means of the modulator / demodulator 32 of the responders 3a to 3c, which is means for extracting signal strength information and signal content information from the received interrogation wave, and the information acquisition unit 33. However, it will be explained. FIG. 5 is a block diagram of the demodulation means of the modem 32 and the information acquisition unit 33 of the responders 3a to 3c.
[0034]
As shown in FIG. 5A, the demodulating means of the modem 32 includes a band pass filter (BPF) 51 and a detection circuit 52. The BPF 51 extracts a signal in the main carrier frequency band from the interrogation wave received by the antenna 31 and outputs the signal to the detection circuit 52. The detection circuit 52 demodulates the signal extracted by the BPF 51 and outputs it to an amplifier 53 of the information acquisition unit 33 and a low-pass filter (LPF) 55 described later. The information acquisition unit 33 includes an amplifier 53, an A / D converter 54, an LPF 55, an amplifier 56, and a limiter 57. The amplifier 53 amplifies the signal demodulated by the modem 32 and outputs the amplified signal to the A / D converter 54. The A / D converter 54 converts the signal amplified by the amplifier 53 into a digital signal corresponding to the signal strength, and outputs the digital signal to the distance detection unit 42 of the controller 41 as signal strength information. Further, the LPF 55 removes high frequency noise from the signal demodulated by the modem 32 and outputs it to the amplifier 56. The amplifier 56 amplifies the signal from which the high frequency noise has been removed by the LPF 55 and outputs the amplified signal to the limiter 57. The limiter 57 forms the signal amplified by the amplifier 56 into a digital signal and outputs the signal to the information creation unit 44 of the controller 41 as signal content information.
[0035]
If the main carrier is not amplitude-modulated, the configuration shown in FIG. As shown in FIG. 5 (b), the demodulator of the modem 32 includes a detection circuit 61. The detection circuit 61 demodulates the interrogation wave received by the antenna 31 and outputs it to the LPF 62 of the information acquisition unit 33 described later. The information acquisition unit 33 includes an LPF 62, an amplifier 63, an A / D converter 64, and a limiter 65. The LPF 62 removes high frequency noise from the signal demodulated by the modem 32 and outputs it to the amplifier 63. The amplifier 63 amplifies the signal from which the high frequency noise has been removed by the LPF 62 and outputs the amplified signal to the A / D converter 64 and the limiter 65, respectively. The A / D converter 64 converts the signal amplified by the amplifier 63 into a digital signal corresponding to the intensity of the signal, and outputs the digital signal to the distance detection unit 42 of the controller 41 as signal intensity information. Further, the limiter 65 forms the signal amplified by the amplifier 63 into a digital signal and outputs it as signal content information to the information creation unit 44 of the controller 41.
[0036]
Next, communication during the communication system 1 will be described with reference to FIGS. First, the interrogator 2 oscillates the main carrier wave having the frequency Fc1 from the oscillator 11 of the analog circuit unit 10. The main carrier wave oscillated by the oscillator 11 is amplitude-modulated by the modulator 12 with information indicating the ID number of the interrogator 2 and the like. The main carrier wave amplitude-modulated by the modulator 12 is amplified by the power amplifier 13. The main carrier wave amplified by the power amplifier 13 is transmitted as an interrogation wave by the circulator 14 via the antenna 17.
[0037]
The interrogation wave transmitted from the interrogator 2 is received by the antennas 31 of the responders 3a to 3c. The interrogation wave received by the antenna 31 is demodulated by the modem 32. The interrogation wave demodulated by the modem 32 is extracted by the information acquisition unit 33 as signal strength information and signal content information. The distance between the interrogator 2 and the responders 3a to 3c is detected by the distance detection unit 42 from the intensity information of the signal extracted by the information acquisition unit 33. The information creation unit 44 creates reply information based on the signal content information extracted by the information acquisition unit 33. Then, based on the distance detected by the distance detection unit 42, the band determination unit 43 determines the frequency band of the subcarrier by hopping so that the frequency band is low when the distance is long and the frequency band is high when the distance is short. Then, the determined frequency band of the subcarrier is output to the subcarrier oscillator 45 in accordance with the timing of a time frame randomly selected from a plurality of time frames. The subcarrier oscillator 45 oscillates the subcarrier according to the frequency band of the subcarrier determined by the band determination unit 42. The subcarrier oscillated by the subcarrier oscillator 45 is phase-modulated by the subcarrier modulator 46 according to the return information created by the information creation unit 44. The modem 32 reflects the interrogation wave being received from the interrogator 2 by performing amplitude modulation or phase modulation with the subcarrier phase-modulated by the subcarrier modulator 46, and returns the reflected wave as a reflected wave from the antenna 31.
[0038]
The reflected waves returned from the responders 3a to 3c are received by the antenna 17 of the interrogator 2. The reflected waves from the responders 3 a to 3 c received by the antenna 17 are amplified by the LNA 15 via the circulator 14. The reflected wave amplified by the LNA 15 is mixed by the main carrier demodulator 16 with the signal from the oscillator 11 and the signal mixed with the subcarrier signal is demodulated by homodyne detection. A signal in which the subcarrier signals demodulated by the main carrier demodulator 16 are mixed is taken out by the band division filter 21 as the modulated subcarrier signals of the responders 3a to 3c. It is output to the intensity comparator 27.
[0039]
Each subcarrier signal extracted by the band division filter 21 is demodulated by the subcarrier demodulator 22 and an information signal is extracted. Each information signal extracted by the subcarrier demodulator 22 is separated by the frame divider 23 into an appropriate frame from the output from each channel. The information signal separated into frames by the frame divider 23 is sorted by the frame sorter 24 into the responders 3a to 3c. The information signals sorted by the frame sorter 24 are reconstructed as reply information by linking them in time series by the frame coupler 25. The reply information reconstructed by the frame coupler 25 is input to the controller 26. The output from each channel input to the controller 26 is processed by the controller 26 when the subcarrier intensity comparator 27 determines that the intensity of the information signal is greater than a predetermined intensity.
[0040]
Next, the state of the subcarrier in the communication system 1 will be described with reference to FIGS. 6 and 7. FIG. 6 shows the subcarrier when the interrogator 2 simultaneously receives and demodulates the reflected waves from the responders 3a to 3c. FIG. The vertical axis represents the signal intensity, and the horizontal axis represents the frequency. As shown in FIG. 6, the band decision unit 43 decides the frequency band of the subcarrier to be higher as the distance from the interrogator 2 becomes shorter. Therefore, as shown in FIG. 1, the responders 3 a to 3 c When arranged so as to be far from the interrogator 2 in the order of the responder 3a, the responder 3c, and the responder 3b, the frequency f2 of the subcarrier of the responder 3b, the frequency f3 of the subcarrier of the responder 3c, the response The frequency of the subcarrier increases in order according to the frequency f1 of the subcarrier of the device 3a. Since the signal intensity decreases as the distance increases, the signal intensity gradually decreases as the distance from the interrogator 2 increases. The subcarrier shows a strong harmonic at an odd multiple of the frequency, but the distance 3 from the interrogator 2 is a harmonic 3f2 that is far from the interrogator 2 and has a frequency three times that of the subcarrier f2 from the weak responder 3b. Even if it overlaps with the subcarrier f1 of the responder 3a close to, the influence on the communication can be ignored because the subcarrier f1 is sufficiently stronger than the harmonic 3f2.
[0041]
FIG. 7 is a diagram showing the frequency distribution of subcarriers in time units in the communication system 1. The vertical axis is frequency and the horizontal axis is time. CH1 to CH30 are channels for hopping the subcarrier frequency band. L1 to L10 are distance ranges from the interrogator 2, and indicate the ranges of channels grouped corresponding to each distance range in FIG. That is, the transponder frequency in which the responders in the distance range of L1 are CH1 to CH3, the responders in the distance range of L2 are CH4 to CH6, and the responders in the distance range of L3 are CH7 to CH9. It becomes a band. The distance from the interrogator 2 is close in the order of L1, L2, and L3. Assume that the responder 3b is arranged in the range of L1, the responders 3c and 3c ′ (not shown in FIG. 1) are arranged in the range of L2, and the responder 3a is arranged in the range of L3. t1 to t12 are time frames sufficient for the responders 3a to 3c and 3c ′ to complete one reply. The plurality of rectangular frames arranged in FIG. 7 indicate the relationship between the returned time frame and the sub-carrier frequency band of the returned reflected wave with respect to the reflected wave returned by the responders 3a to 3c, 3c ′. ing.
As shown in FIG. 7, the responder 3a is in the range of CH7 to CH9, the responder 3b is in the range of CH1 to CH3, and the responders 3c and 3c ′ are in the range of CH4 to CH6. Hopping. The responders 3a to 3c and 3c ′ return the reflected waves in the time frames selected at random.
[0042]
As described above, in the first embodiment described above, the frequency band of the modulation signal is set based on the distance between the interrogator 2 and the responders 3a to 3c, 3c ′. As described above, the frequency of the reflected wave of each of the responders 3a to 3c and 3c ′ can be dispersed to reduce interference of the reflected wave between the responders 3a to 3c and 3c ′.
[0043]
Further, since the transponder 3b at a far position lowers the frequency band of the subcarrier and the transponder 3a at a near position raises the frequency band of the subcarrier, the reflected signal from the responder 3b is reflected on the reflected signal from the responder 3b. The harmonics of the signal will not interfere.
[0044]
In addition, since the band determination unit 43 hops the frequency band of the subcarrier, the reflected waves between the responders in the same distance range are less likely to interfere with each other.
[0045]
In addition, since the reflected wave is transmitted in a time frame randomly selected from a plurality of time frames, the reflected waves between the responders in the same distance range are further reduced from interfering with each other.
[0046]
In addition, since the distance is detected based on the intensity of the interrogation wave, the distance can be easily detected, and the distance between the interrogator 2 and the responders 3a to 3c is determined not by the physical length but by the path length. It is possible to detect a distance in accordance with the actual positional relationship that is restricted.
[0047]
<Second Embodiment>
A second embodiment according to the present invention will be described below with reference to the drawings. In the second embodiment according to the present invention, the demodulating means of the modulator / demodulator 32 of the responders 3a to 3c and the information acquiring unit 33 for extracting the signal strength information and the signal content information from the received interrogation wave. Except for the circuit configuration, it is substantially the same as that of the first embodiment according to the present invention. The demodulating means of the modulator / demodulator 32 of the responders 3a to 3c of the first embodiment and the circuit configuration of the information acquisition unit 33 Since explanations other than are applicable, details are omitted.
[0048]
Next, refer to FIG. 8 for details of the circuit configuration of the demodulating means of the modulator / demodulator 32 of the responders 3a to 3c and means for acquiring the signal intensity information and signal content information from the received interrogation wave. However, it will be explained. FIG. 8 is a block diagram of the demodulation means of the modem 32 and the information acquisition unit 33 of the responders 3a to 3c.
[0049]
As shown in FIG. 8, the demodulating means of the modem 32 includes a detection circuit 71. The detection circuit 71 demodulates the interrogation wave received by the antenna 31 and outputs it to a charging circuit 72 and an LPF 74 of the information acquisition unit 33 described later. The information acquisition unit 33 includes a charging circuit 72, a voltage detection circuit 73, an LPF 74, an amplifier 75, and a limiter 76. The charging circuit 72 extracts power from the signal demodulated by the modem 32 and charges the capacitor 34 provided in the responders 3a to 3c. The voltage detection circuit 73 detects the voltage of the charging circuit 72, converts the detected voltage value into a digital signal, and outputs the digital signal to the distance detection unit 42 of the controller 41 as signal intensity information. The LPF 74 removes high frequency noise from the signal demodulated by the modem 32 and outputs it to the amplifier 75. The amplifier 75 amplifies the signal from which the high frequency noise has been removed by the LPF 74 and outputs the amplified signal to the limiter 76. The limiter 76 shapes the signal amplified by the amplifier 75 into a digital signal and outputs the signal to the information creation unit 44 of the controller 41 as signal content information.
Then, the distance detection unit 42 of the controller 41 is connected to the interrogator 2 from the amount of change per unit time of the charged voltage of the charging circuit 72 or the time until the charged voltage is changed to a predetermined voltage amount. Detect the distance. In addition, a power detection circuit is provided instead of the voltage detection circuit 73, and the amount of change per unit time of the charged power of the charging circuit 72 or the time until the charged power is changed to a predetermined amount of power. The distance from the interrogator 2 may be detected.
[0050]
The capacitor 34 is a power source that operates the responders 3a to 3c. The capacitor 34 is charged by extracting power from the interrogation wave received by the charging circuit 72. When the electric power charged in the capacitor 34 becomes equal to or higher than a predetermined electric power, the responders 3a to 3c are activated using the charged electric power to operate each function.
[0051]
Since the operation state of the communication system 1 according to the second embodiment is substantially the same as the operation state of the communication system 1 according to the first embodiment, the operation state of the communication system 1 according to the second embodiment. The details about are omitted.
[0052]
As described above, in the second embodiment described above, in addition to the effects described in the first embodiment, the responders 3a to 3c operate with the electric power charged in the capacitor 34. It is not necessary to provide a device, and the responders 3a to 3c can be reduced in size and weight.
In addition, since the reception intensity varies depending on the distance between the interrogator 2 and the responders 3a to 3c, the charging time is different, and the time until charging is naturally dispersed in each of the responders 3a to 3c. Response timing is also dispersed by the responders 3a to 3c, and interference can be reduced.
When the capacitor 34 has a relatively large capacity, there is a case where power is still held in the capacitor 34 at the next response, and is held in the capacitor 34 every time the charging response is repeated over time. Since the power and dispersion of capacitor specification and the like are also added, the response is naturally distributed for each of the responders 3a to 3c, and the same effect is produced. Therefore, even when the distance is almost the same, the interference between the responders 3a to 3c is considerably reduced. be able to.
[0053]
<Third Embodiment>
The third embodiment of the present invention will be described below with reference to the drawings. The configuration example of the communication system 1 according to the third embodiment is substantially equivalent to the configuration of the communication system 1 according to the first embodiment, and the configuration of the communication system 1 according to the first embodiment. Since the explanation of is applicable, the details are omitted.
The configuration of the interrogator 2 constituting the communication system 1 is substantially the same as the configuration of the interrogator 2 constituting the communication system 1 according to the first embodiment. Since the description of the configuration of the interrogator 2 constituting the communication system 1 can be applied, details are omitted.
[0054]
Next, the function part comprised by the controller 26 of the interrogator 2 is demonstrated, referring FIG. FIG. 9 is a block diagram showing a configuration of the interrogator 2 in the third embodiment. The controller 26 further includes a distance detection unit (interrogator distance detection unit) 28, a distance information transmission unit (distance information transmission unit) 29, and the like as functional units. The distance detector 28 detects the distance between the interrogator 2 and the responders 3a to 3c from the intensity of the reflected wave signals of the responders 3a to 3c received by the interrogator 2. Specifically, the signal strength of each of the subcarrier signals divided by the band filter 21 is compared with a multi-stage threshold by the subcarrier strength comparator 27, and the strength of the signal stored in advance is determined from the comparison result. The distance between the interrogator 2 and the responders 3a to 3c is detected using a correspondence table between the distance between the interrogator 2 and the responders 3a to 3c. The distance information transmitting unit 29 transmits the distance between the interrogator 2 and the responders 3a to 3c detected by the distance detecting unit 28 to the respective responders 3a to 3c as distance information according to a communication procedure described later.
[0055]
Next, the configuration of the responder 3a will be described with reference to FIG. FIG. 10 is a block diagram showing the configuration of the responder 3a. The configuration of the responders 3b and 3c is substantially the same as that of the responder 3a, and the description of the responder 3a can be applied.
[0056]
As shown in FIG. 10, the responder 3 a includes an antenna 31 (reception reflection unit), a modem 32, an information acquisition unit 33 (distance detection unit), and a digital circuit unit 40. The modem 32 demodulates the interrogation wave received by the antenna 32 and outputs it to the information acquisition unit 33. Also, the modem 32 modulates the interrogation wave with the subcarrier modulated by the subcarrier modulator 46 described later, and returns the modulated wave as a reflected wave from the antenna 31. The information acquisition unit 33 acquires signal content information from the signal demodulated by the modem 32 and outputs the signal content information to the information creation unit 44 described later.
[0057]
The digital circuit unit 40 includes a controller 41, a subcarrier oscillator 45, and a subcarrier modulator 46 (modulation signal generating means). The subcarrier oscillator 45 oscillates a subcarrier having a frequency determined by a band determination unit 43 described later of the controller 41, and outputs the oscillated subcarrier to the subcarrier modulator 46. The subcarrier modulator 46 modulates the subcarrier input from the subcarrier oscillator 45 by phase modulation (Phase Shift Keying: PSK) based on the information signal created by the information creation unit 44 (to be described later) of the controller 41. The subcarrier is output to the modem 32. The controller 41 controls the responder 3a, and constitutes a bandwidth determining unit 43 (band determining unit) and an information creating unit 44 (information creating unit) that are functional units. Note that the subcarrier oscillator 45 and the subcarrier modulator 46 may be configured in software using the clock of the controller 41. The subcarrier modulation may be frequency modulation (FSK) in addition to phase modulation. Further, the subcarrier oscillator 45 and the subcarrier modulator 46 may be provided in the controller 41 and integrated into one chip.
[0058]
Next, each functional unit configured by the controller 41 will be described. The band determination unit 43 determines the frequency band of the reflected subcarrier and outputs the determined frequency band to the subcarrier oscillator 45 to oscillate the subcarrier. The frequency band of the subcarrier is determined by a frequency hopping method. The responder 3a hops the frequency band of the subcarrier for each reply by the frequency hopping method. By using the frequency hopping method in this way, it is possible to reduce the possibility that a plurality of reflected waves returned at the same time interfere with each other, and to increase the confidentiality of the returned reply information. However, if the frequency of the subcarrier is hopped over the entire frequency band, as described above, the reflected wave of the responder far from the interrogator 2 is reflected from the responder near the interrogator 2. Or may be interfered by the harmonics of the reflected wave. Therefore, the band determining unit 43 limits the frequency band to be hopped so that the frequency band of the subcarrier is high when the distance between the interrogator 2 and the responder 3a is short, and the frequency band of the subcarrier is low when the distance is long. To do. Specifically, first, signal content information is extracted from the interrogation wave transmitted from the interrogator 2 to the responder 3a by the information acquisition unit 33, and distance information between the interrogator 2 and the responder 3a detected by the interrogator 2 is obtained. Get. Then, from the distance information between the interrogator 2 and the responder 3a transmitted from the interrogator 2, from the correspondence table between the distance between the interrogator 2 and the responder 3a and the limited frequency band, the interrogator 2 and the responder The frequency band of the subcarrier to be hopped is determined by the distance information with 3a. An example of the correspondence table between the distance between the interrogator 2 and the responder 3a and the limited frequency band is substantially the same as the correspondence table (FIG. 4) used in the first embodiment. As shown in FIG. 4, the center frequency of the limited frequency band is set to decrease from 300.0 kHz to 10 kHz as the distance between the interrogator 2 and the responder 3a increases from 0.5 m to 0.1 m. Has been. According to this correspondence table, for example, when the distance between the interrogator 2 and the responder 3a detected by the information acquisition unit 33 is 0.6 m, the hopping frequency band is 285.0 kHz to 295.0 kHz. The frequency band of the subcarrier of the reflected wave is determined by frequency hopping from a plurality of channels included in this frequency band.
[0059]
In addition, the band determination unit 43 controls the timing of returning the reflected wave by controlling the timing of outputting the determined frequency band to the subcarrier oscillator 45. The timing for returning the reflected wave is determined by setting a plurality of predetermined time frames sufficient to complete one reply and randomly selecting a time frame for replying from the plurality of time frames. To do.
[0060]
The information creation unit 44 reads the reply information stored in a memory (not shown) provided in the controller 41 based on the signal content information of the interrogation wave acquired by the information acquisition unit 33 and outputs it to the subcarrier modulator 46. To do. The reply information may be read from an external device connected to the responder 3a.
[0061]
Next, regarding the circuit configuration of the demodulating means of the modulator / demodulator 32 of the responders 3a to 3c, which is means for extracting signal content information from the received interrogation wave, and the information acquisition unit 33, the responder according to the first embodiment. It is substantially equivalent to the circuit configuration of the demodulating means of the modems 3a to 3c and the information acquisition unit 33 (except for means for extracting signal strength information), and the responders 3a to 3c according to the first embodiment. Since the description of the circuit configuration of the demodulating means of the modem 3c and the information acquiring unit 33 can be applied, the details are omitted.
The operation sequence during communication in the communication system 1 is substantially the same as the operation sequence during communication in the communication system 1 according to the first embodiment, and the communication system 1 according to the first embodiment. The description of the operation sequence at the time of communication in FIG.
Further, the state of the subcarrier in the communication system 1 is substantially the same as the state of the subcarrier in the communication system 1 according to the first embodiment, and the subcarrier in the communication system 1 according to the first embodiment. Since the explanation of the state of the carrier wave is applicable, the details are omitted.
[0062]
Next, the operation of the communication procedure of the interrogator 2 will be described with reference to FIG. FIG. 11 is a flowchart showing the operation of the communication procedure of the interrogator 2. First, the process proceeds to step S110 (hereinafter abbreviated as S110, the same applies to other steps), and interrogation waves for searching for the responders 3a to 3c are transmitted. Thereafter, the process proceeds to S120, and it is determined whether or not a reflected wave, which is a reply to the link request from the responders 3a to 3c, has been received in response to the interrogation wave for searching for the responders 3a to 3c within a predetermined time. When a reflected wave that is a response to the link request from the responders 3a to 3c is not received (S120: NO), the process proceeds to S110 again, and an interrogation wave is transmitted to search for the responders 3a to 3c. When a reflected wave that is a response to the link request from the responders 3a to 3c is received (S120: YES), the process proceeds to S130, and the distance detection unit 28 of the controller 26 uses the reflected wave signal that is a response to the link request. From the intensity, the distance between the interrogator 2 and the responders 3a to 3c that requested the link is detected.
[0063]
Thereafter, the process proceeds to S140, and the distance information detected from the intensity of the reflected wave signal by the distance information transmitting unit 29 of the controller 26 is transmitted as a question wave to the responders 3a to 3c that have returned the link request. Thereafter, the process proceeds to S150, and a reflected wave that is a reply from the responders 3a to 3c that requested the link is received and communication is started. Thereafter, the process proceeds to S160, and the reply from the responders 3a to 3c that requested the link is completed and the communication is terminated. Thereafter, the process proceeds to S110 again, and a query wave is transmitted to search for the responders 3a to 3c.
[0064]
Next, the operation of the communication procedure of the responders 3a to 3c will be described with reference to FIG. FIG. 12 is a flowchart showing the operation of the communication procedure of the responders 3a to 3c. First, the process proceeds to S210, and it is determined whether or not an interrogation wave for searching the responders 3a to 3c from the interrogator 2 has been received. When the interrogation wave for searching the responders 3a to 3c is not received (S210: NO), the process proceeds to S210 again and is repeated until the interrogation wave for searching the responders 3a to 3c is received. When the interrogation wave for searching the responders 3a to 3c is received (S210: YES), the process proceeds to S220, and it is determined whether or not the own station is the responder that is the search target of the interrogator 2. If the responder is the search target that is the subject station (S220: YES), the process proceeds to S240. When the own station is not the searcher that is the search target (S220: NO), the process proceeds to S230, and it is determined whether there is transmission information to be transmitted to the interrogator 2. When there is no transmission information (S230: NO), the process proceeds to S210 again, and is repeated until a query wave for searching the responders 3a to 3c is received. If there is transmission information (S230: YES), the process proceeds to S240. In S240, in order to communicate with the interrogator 2, a link request is returned to the interrogator 2 as a reflected wave of the received interrogation wave.
[0065]
Thereafter, the process proceeds to S250, and distance information between the interrogator 2 and the own station is received from the interrogator 2 as an interrogation wave. Thereafter, the process proceeds to S260, and the frequency band of the subcarrier is determined by the band determination unit 43 from the received distance information. Thereafter, the process proceeds to S270, and the interrogation wave received by the subcarrier in the frequency band determined by the band determination unit 43 is modulated and reflected, and transmission of transmission information is started. Thereafter, the process proceeds to S280, where the reply is completed and the communication is terminated. Thereafter, the process proceeds to S210 again, and is repeated until a query wave for searching for the responders 3a to 3c is received.
[0066]
Next, the operation sequence of the communication procedure of the communication system 1 will be described with reference to FIG. FIG. 13 is an operation sequence diagram of a communication procedure of the communication system 1. First, the interrogator 2 transmits an interrogation wave to search for the responders 3a to 3c (S310). And the responders 3a-3c receive the interrogation wave transmitted from the interrogator 2 (S410). Thereafter, the responders 3a to 3c searched by the interrogator 2 return a link request to the interrogator 2 (S420). Then, the interrogator 2 receives the link request returned from the responders 3a to 3c (S320). Thereafter, the interrogator 2 detects the distance between the interrogator 2 and the responders 3a to 3c from the received signal strength of the link request from the responders 3a to 3c by the distance detector 28 (S330). ). Then, the interrogator 2 transmits the detected distance information between the interrogator 2 and the responders 3a to 3c to the responders 3a to 3c by the distance information transmission unit 29 (S340).
[0067]
Then, the responders 3a to 3c receive the interrogator 2, the responders 3a to 3c and the distance information transmitted from the interrogator 2 (S430). Thereafter, the responders 3a to 3c determine the frequency band of the subcarrier by the band determination unit 43 based on the received distance information (S440). Thereafter, the responders 3a to 3c send back information to the interrogator 2 by modulating and reflecting the interrogation wave transmitted from the interrogator 2 by the frequency band of the subcarrier determined by the band determining unit 43 (S450). When the responders 3a to 3c complete the return of the information to the interrogator 2, the communication ends (S460). Then, the interrogator 2 receives the information returned from the responders 3a to 3c (S360). When the interrogator 2 completes the reception of the information returned from the responders 3a to 3c, the interrogator 2 ends the communication (S360).
[0068]
As described above, in the third embodiment described above, since the frequency band of the modulation signal is set based on the distance between the interrogator 2 and the responders 3a to 3c, the distance is often different. The frequency of the reflected waves of the devices 3a to 3c can be dispersed to reduce the interference of the reflected waves between the responders 3a to 3c.
[0069]
Further, since the transponder 3b at a far position lowers the frequency band of the subcarrier and the transponder 3a at a near position raises the frequency band of the subcarrier, the reflected signal from the responder 3b is reflected on the reflected signal from the responder 3b. The harmonics of the signal will not interfere.
[0070]
In addition, since the band determination unit 43 hops the frequency band of the subcarrier, the reflected waves between the responders in the same distance range are less likely to interfere with each other.
[0071]
In addition, since the reflected wave is transmitted in a time frame randomly selected from a plurality of time frames, the reflected waves between the responders in the same distance range are further reduced from interfering with each other.
[0072]
Further, the distance detector 28 of the interrogator 2 detects the distance between the interrogator 2 and the responders 3a to 3c, and the distance information transmitter 29 transmits the distance information to the responders 3a to 3c. It is not necessary to detect the distance on the ~ 3c side, the burden on the responders 3a to 3c can be reduced, and the structures of the responders 3a to 3c can be simplified.
[0073]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made as long as they are described in the claims. For example, in the first to third embodiments, the transponder having a long distance from the interrogator lowers the frequency band of the subcarrier, and the transponder having a short distance from the interrogator increases the frequency band of the subcarrier. However, the present invention is not limited to such a configuration, and may be a configuration that is not limited to a specific frequency band depending on the distance from the interrogator. Further, in this case, a configuration may be adopted in which the time frames for replying with the responders located at a position far from the interrogator and the responders located at a close position do not overlap.
[0074]
In the first to third embodiments, the frequency band of the subcarrier is randomly hopped. However, the present invention is not limited to such a configuration, and may be configured to hop according to a predetermined order. Good.
[0075]
In the first to third embodiments, the range for hopping the subcarrier frequency band is limited to a frequency band in which a plurality of channels are grouped according to the distance between the interrogator and the responder. The configuration is not limited to such a configuration, and a configuration in which a frequency band of a specific subcarrier corresponding to the distance between the interrogator and the responder may be determined.
[0076]
Further, in the first to third embodiments, in the response of the reflected wave of the responder, a plurality of time frames are set, and the time frame to be replied is randomly selected from the time frames. The present invention is not limited to such a configuration, and transmission may be performed at a predetermined time frame timing or a time frame may not be set.
[0077]
In the third embodiment, the distance between the interrogator and the transponder is detected on the interrogator side and transmitted to the transponder as distance information. On the transponder side that has received the distance information, the distance information is based on the distance information. This is a configuration that determines the frequency band of the subcarrier, but is not limited to such a configuration. The interrogator side detects the distance between the interrogator and the responder, and further detects the subcarrier based on the detected distance. The frequency band may be determined, and the determined frequency band may be transmitted to the responder as frequency band information.
[0078]
In the first to third embodiments, the responder has been described focusing on an example in which the frequency of the subcarrier is changed at each time interval, that is, the frequency of the subcarrier is hopped. However, the distance between the interrogator and the responder is described. If the frequency or timing of the subcarrier is set based on the above, it is needless to say that the interference of the reflected wave of each responder can be sufficiently reduced only by fixing the subcarrier frequency.
[0079]
【The invention's effect】
According to the present invention, since the frequency band of the modulation signal is set based on the distance between the interrogator and the responder, the distance is often different. As a result, the frequency of the reflected wave of each responder is dispersed, Interference of reflected waves between responders can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration example of a communication system according to a first embodiment.
FIG. 2 is a block diagram showing a configuration of an interrogator shown in FIG.
FIG. 3 is a block diagram showing a configuration of a responder shown in FIG.
FIG. 4 is an example of a correspondence table between a distance between an interrogator and a responder and a limited frequency band.
5 is a block diagram of a demodulation unit and an information acquisition unit of a modem unit of the responder shown in FIG.
6 is a frequency distribution diagram of subcarriers when a reflected wave is simultaneously received from the responder shown in FIG. 1 and demodulated.
7 is a diagram showing a frequency distribution in time units in the communication system shown in FIG. 1; FIG.
FIG. 8 is a block diagram of a demodulation unit and an information acquisition unit of a modem unit of a responder according to a second embodiment.
FIG. 9 is a block diagram showing a configuration of an interrogator in the third embodiment.
FIG. 10 is a block diagram showing a configuration of a responder in a third embodiment.
FIG. 11 is a flowchart showing an operation of a communication procedure of an interrogator in the third embodiment.
FIG. 12 is a flowchart showing an operation of a communication procedure of a responder in the third embodiment.
FIG. 13 is an operation sequence diagram of a communication procedure of the communication system in the third embodiment.
[Explanation of symbols]
1 Communication system
2 interrogator
3a-3c transponder
31 Antenna
32 modem
33 Information acquisition unit
42 Distance detector
43 Band decision part
44 Information creation department
45 Subcarrier oscillator

Claims (11)

A responder of a communication system that transmits an interrogation wave including a main carrier from an interrogator, and a responder that has received the main carrier returns a reflected wave obtained by modulating the main carrier with predetermined information to the interrogator. Because
Distance detecting means for detecting a distance between the interrogator and the responder;
Main carrier receiving and reflecting means for receiving and reflecting the interrogation wave including the main carrier transmitted from the interrogator;
Information creating means for creating information to be transmitted from the responder;
Band determining means for determining a frequency band of a modulation signal for modulating a reflected wave reflected by the main carrier wave receiving / reflecting means based on a distance detected by the distance detecting means;
Modulation signal generating means for generating the modulation signal based on the information created by the information creating means so that the frequency band of the modulated signal is a frequency band determined by the band determining means. The responder of the communication system.   The responder of the communication system according to claim 1, wherein the band determining unit increases the frequency band of the modulated signal as the distance detected by the distance detecting unit is shorter. Before Symbol - band determining means, the frequency band, the response in a communication system according to claim 1 or 2, characterized in that calculated from the detected distance by the predetermined relationship by the distance detecting means. Before Symbol - band determining means, a communication system according to the frequency band, to claim 1 or 2, wherein the determining based on the correspondence table between the detected distance by said frequency band and said distance detecting means Responder. Prior Symbol - band determining means, the frequency band, from a group of the frequency band selected based on the correspondence table between the detected distance by said distance detection means and grouped the frequency band, random or response The responder of the communication system according to claim 1 or 2, wherein the response is determined based on a unique definition for each device. The modulation signal generating means sets a plurality of transmission time frames, and determines which transmission time frame is to be modulated based on a random or unique definition for each responder. The responder of the communication system according to any one of 5. The communication system according to any one of claims 1 to 6, wherein the modulation signal generation unit does not change the frequency band determined by the band determination unit until the transmission of the information is completed. Responder. It further comprises a charging means for taking out the electric power of the interrogation wave and charging it,
2. The charging device according to claim 1, wherein when the electric power stored in the responder exceeds a predetermined capacity, each unit of the responder is operated to respond to the interrogation wave. The responder of the communication system according to any one of 7.   The distance detecting means is based on the amount of change per unit time of the charged voltage or power in the charging means, or the time when a change in the predetermined amount of the charged voltage or power is obtained. The responder of the communication system according to claim 8, wherein a distance from the responder is detected.   The responder of the communication system according to any one of claims 1 to 8, wherein the distance detection unit detects a distance from the intensity of the interrogation wave. The interrogator detects the distance between the interrogator and the responder from the intensity of the modulated signal obtained from the modulated reflected wave returned from the responder that has received the interrogation wave. Detection means;
Distance information transmitting means for transmitting the distance information to the responder;
The transponder receives the distance information by the main carrier wave reception reflection means,
The interrogator and the communication system according to any one of claims 1 to 8, wherein the distance detection unit detects a distance between the interrogator and the responder from the distance information. A communication system composed of transponders.

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