WO2005106525A1

WO2005106525A1 - Wireless tag communication apparatus

Info

Publication number: WO2005106525A1
Application number: PCT/JP2005/005513
Authority: WO
Inventors: Tsuyoshi Ohashi
Original assignee: Brother Kogyo Kabushiki Kaisha
Priority date: 2004-04-27
Filing date: 2005-03-25
Publication date: 2005-11-10
Also published as: JPWO2005106525A1

Abstract

A wireless tag communication apparatus capable of determining a distance from a wireless tag. There are included a question wave transmitting part (50) that transmits a plurality of types of question waves (Fc) having their respective different frequencies; I-phase and Q-phase signal converting parts (28,30) that receive and demodulate a plurality of types of response waves (Fr) transmitted from a wireless tag (14) in reply to the plurality of types of question waves (Fc) transmitted from the question wave transmitting part (50); and a distance calculating part (54) that calculates a distance (d) from the wireless tag (14) based on a result of demodulations of the plurality of types of response waves (Fr) by the I-phase and Q-phase signal converting parts (28,30). Accordingly, the distance (d) from the wireless tag (14) can be appropriately determined by communicating with the wireless tag (14).

Description

Specification

Wireless tag communication device

Technical field

The present invention relates to an improvement in a wireless tag communication device that performs communication with a wireless tag that can write and read information wirelessly.

Background art

[0002] RFID (Radio Frequency) that reads information from a small wireless tag (transponder) storing predetermined information in a non-contact manner by a predetermined wireless tag communication device (interrogator)

Identification) systems are known. This RFID system is capable of reading information stored in a wireless tag by communicating with the wireless tag communication device even when the wireless tag is dirty or invisible, is placed at a position, or is not visible. Because of this, practical applications are expected in various fields such as product management and inspection processes!

[0003] By the way, a wireless tag communication device has been proposed which detects the relative movement speed of the wireless tag by communicating with the wireless tag. For example, the modulation back-skiutter system described in Patent Literature 1 is that. According to this technology, a response wave in which the RFID tag power is also returned in response to an interrogation wave is received and converted into an I-phase signal and a Q-phase signal that are orthogonal to each other. Based on the signal, the presence / absence of the movement of the wireless tag, the extension, and the moving speed of the wireless tag with respect to the wireless tag communication device can be detected.

Patent Document 1: Japanese Patent Application Laid-Open No. 11 136161

[0005] However, in the conventional technique, although the moving speed of the wireless tag with respect to the wireless tag communication device can be detected by performing communication with the wireless tag, the distance between the wireless tag and the wireless tag is detected. I couldn't do it. In particular, techniques for finding such distances for relatively short distance RFID communication have been powerful. In other words, there has been a demand for the development of a wireless tag communication device capable of detecting the distance to the wireless tag!

Disclosure of the invention

Problems the invention is trying to solve The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wireless tag communication device capable of detecting a distance from a wireless tag.

Means for solving the problem

[0007] In order to achieve such an object, the gist of the present invention is a wireless tag communication device that performs non-contact information communication with a wireless tag in which predetermined information is stored. Interrogation wave transmitter for transmitting a plurality of types of interrogation waves having different frequencies, and a plurality of types of reply waves returned from the wireless tag in response to the plurality of types of interrogation waves transmitted from the interrogation wave transmission unit A reception demodulation unit that receives and demodulates the response wave, and a distance calculation unit that calculates a distance between the wireless tag based on a demodulation result of a plurality of types of response waves by the reception demodulation unit. It is a feature.

The invention's effect

[0008] According to this configuration, the interrogation wave transmitting unit for transmitting a plurality of types of interrogation waves each having a different frequency, and the interrogation wave according to the plurality of types of interrogation waves transmitted from the interrogation wave transmitting unit A reception demodulation unit that receives and demodulates a plurality of types of response waves returned from the wireless tag, and calculates a distance between the wireless tag based on a demodulation result of the plurality of types of response waves by the reception and demodulation unit. The distance between the wireless tag and the wireless tag can be suitably obtained by performing communication with the wireless tag. That is, it is possible to provide a wireless tag communication device capable of detecting a distance from the wireless tag.

[0009] Preferably, the reception demodulation unit converts the response wave returned from the wireless tag into an I-phase signal and a Q-phase signal that are orthogonal to each other and performs orthogonal demodulation. With this configuration, the distance between the wireless tag and the wireless tag can be suitably obtained in the wireless tag communication device including the demodulation circuit of the quadrature detection method.

[0010] Preferably, the distance calculation unit calculates a distance between the wireless tag based on a ratio between the I-phase signal and the Q-phase signal in which both the wireless tag power and the response wave power to be returned are converted. It is calculated. With this configuration, it is possible to obtain the distance between the wireless tag and the wireless tag in a practical manner in the wireless tag communication device including the quadrature detection waveform demodulation circuit.

[0011] Preferably, the radio communication apparatus further includes a main carrier phase control unit for distributing the main carrier of the interrogation wave, controlling the phase thereof, and supplying the main carrier to the reception demodulation unit. The response wave returned from the tag carrier is subjected to homodyne demodulation based on the main carrier whose phase is controlled and supplied by the main carrier phase controller. With this configuration, the distance from the wireless tag to the wireless tag communication device including the demodulation circuit of the homodyne detection method can be suitably obtained.

[0012] Preferably, the interrogation wave transmitter transmits a first interrogation wave and a second interrogation wave having different frequencies, and the reception / demodulation unit transmits the interrogation wave from the interrogation wave transmitter. A first response wave and a second response wave returned in response to the wireless tag power in response to the transmitted first and second interrogation waves are received and demodulated, respectively. In this way, the distance between the wireless tag and the wireless tag can be suitably obtained by the necessary and sufficient interrogation waves and response waves.

[0013] Preferably, the frequencies of the first interrogation wave and the second interrogation wave are indivisible values. In this way, the distance to the wireless tag can be more preferably determined.

[0014] Preferably, the distance calculation section includes a first distance candidate group obtained based on a demodulation result of the first response wave by the reception demodulation section, and a demodulation of the second response wave. The second distance candidate group determined based on the result is compared with the second distance candidate group, and the smallest value among the values commonly included in the first distance candidate group and the second distance candidate group is compared with the wireless tag. It is calculated as the distance between them. In this way, the distance between the wireless tag and the wireless tag can be obtained in a practical manner.

[0015] Preferably, the interrogation wave transmitting unit transmits the first interrogation wave and the second interrogation wave alternately. In this way, a necessary and sufficient interrogation wave can be transmitted with a simple configuration.

[0016] Preferably, the interrogation wave transmitting unit transmits the plurality of types of interrogation waves simultaneously. In this way, the distance to the wireless tag can be obtained as quickly as possible.

[0017] Preferably, the distance calculation unit calculates a distance from the wireless tag based on an intensity of a response wave returned from the wireless tag. In this way, the distance to the wireless tag can be more preferably obtained. [0018] Preferably, the distance calculation unit calculates a distance to the wireless tag based on a communicable distance to the wireless tag. In this way, the distance to the wireless tag can be more preferably obtained.

Brief Description of Drawings

FIG. 1 is a diagram illustrating a configuration of a communication system to which the present invention is suitably applied.

FIG. 2 is a diagram illustrating an electrical configuration of a wireless tag communication device according to an embodiment of the present invention.

FIG. 3 is a block diagram illustrating a wireless tag circuit included in the wireless tag of FIG. 1.

4 is a diagram exemplifying a subcarrier used for reply control by a control unit included in the wireless tag circuit of FIG. 3 and a code signal in which the subcarrier is encoded by a predetermined information signal.

FIG. 5 is a flowchart illustrating tag position detection control by a control unit of the wireless tag communication device in FIG. 2.

6 is a flowchart illustrating tag position determination control from a candidate string in the control of FIG. 5.

FIG. 7 is a diagram illustrating the principle of tag position detection control by a control unit of the wireless tag communication device in FIG. 2.

8 is a flowchart illustrating another example of tag position detection control by the control unit of the wireless tag communication device in FIG. 2.

FIG. 9 is a diagram illustrating an electrical configuration of a wireless tag communication device according to a second embodiment of the present invention.

FIG. 10 is a flowchart illustrating tag position detection control by a control unit of the wireless tag communication device in FIG. 9.

FIG. 11 is a diagram illustrating a state in which different interrogation waves are simultaneously transmitted from the two wireless tag communication devices shown in FIG. 2 to the wireless tag.

Explanation of symbols

[0020] 10: Communication system, 12, 70: Wireless tag communication device, 16: Main carrier generation unit, 18: PLL, 20: VCO, 22: Main carrier modulation unit, 24: Transmission signal amplification unit, 26: Antenna, 14: Wireless tag, 28: 1-phase signal converter (receiver / demodulator), 30: Q-phase signal converter (receiver / demodulator), 32: transmit / receive demultiplexer, 34: I¾ff ^ -BPF, 36: 1-phase signal amplifier, 38: Q Phase signal BPF, 40: Q-phase signal amplifier, 42: RSSI circuit, 44: controller, 50: interrogation transmitter, 52: signal processor (reception demodulator), 54: distance calculator, 56: wireless Tag circuit, 58: Antenna, 60: Clock block, 62: Power supply block, 64: Variable Z demodulation block, 66: Control block, 68: Memory block, 72: Phase shift circuit, 74: Receive demodulation block, 76: Demodulation Signal BPF, 78: Demodulated signal amplifier, 80: Carrier phase controller

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

Example 1

FIG. 1 is a diagram illustrating a configuration of a communication system 10 to which the present invention is suitably applied. The communication system 10 is a so-called RFID (Radio Frequency Identification) system including a wireless tag communication device 12 according to an embodiment of the present invention and one or more (single in FIG. 1) wireless tags 14. The wireless tag communication device 12 functions as an interrogator of the RFID system, and the wireless tag 14 functions as a transponder. That is, when the interrogation wave F (transmission signal) is transmitted from the radio tag communication device 12 to the wireless tag 14, the radio tag 14 receiving the interrogation wave F converts the interrogation wave F into a predetermined information signal (data). Further, the interrogation wave F is modulated and returned as a response wave F (return signal) to the RFID tag communication device 12, whereby information communication between the RFID tag communication device 12 and the RFID tag 14 is performed. Is performed. D in FIG. 1 indicates the distance between the wireless tag communication device 12 and the wireless tag 14 (the distance between the antenna 24 of the wireless tag communication device 12 and the antenna 58 of the wireless tag 14).

FIG. 2 is a diagram illustrating the electrical configuration of the wireless tag communication device 12 of the present embodiment. As shown in FIG. 2, the wireless tag communication device 12 of the present embodiment includes a reference frequency generator 16 for generating the main carrier of the interrogation wave F, a reference wave generated by the reference frequency generator 16 and a control signal. PLL (Phase Locked Loop) 18 that sets the frequency of the main carrier based on the control signal from unit 44, and VCO (Voltage Controlled Oscillator) 20 that controls the frequency of the main carrier according to the control voltage from PLL 18 And a main carrier having a predetermined frequency controlled by the VCO 20 is amplitude-modulated based on a predetermined control signal TX-ASK. And a transmission signal amplifying unit 24 for amplifying the transmission signal output from the main carrier modulation unit 22 based on a predetermined control signal TX-PWR, and a transmission signal amplifying unit. The transmitter / receiver transmits the transmission signal output from 24 as an interrogation wave F to the wireless tag 14 that is the object of communication, and receives a response wave F in which the wireless tag 14 also returns a response to the interrogation wave F. Antenna 26 and an I-phase signal converter 28 and Q that convert a received signal received by the antenna 26 into an I-phase signal and a Q-phase signal orthogonal to each other by two signals having a phase difference of ππ2 radians. The transmission signal output from the phase signal conversion unit 30 and the transmission signal amplification unit 24 is supplied to the antenna 26, and the reception signal received by the antenna 26 is converted into the I-phase signal conversion unit 28 and the Q-phase signal. Supply to converter 30 Transmission / reception separation unit 32, an I-phase signal BPF (Band Pass Filter) 34 that extracts only signals in a predetermined frequency band from the I-phase signals output from the I-phase signal conversion unit 28, and the I-phase signal BPF34 An I-phase signal amplifying unit 36 that amplifies the I-phase signal output from the Q-phase signal conversion unit 30, and a Q-phase signal BPF38 that extracts only a signal of a predetermined frequency band from the Q-phase signal output from the Q-phase signal conversion unit 30. The Q-phase signal amplifying section 40 amplifies the Q-phase signal output from the Q-phase signal BPF 38, and the I-phase signal and the Q-phase signal output from the I-phase signal amplifying section 36 and the Q-phase signal amplifying section 40. It is provided with an RSSI (Redeved Signal Strength Indicator) circuit 42 for detecting the strength and a control unit 44 for controlling the operation of the RFID tag communication device 12. Here, the I-phase signal conversion unit 28, the Q-phase signal conversion unit 30, and the signal processing unit 54 described later correspond to a reception demodulation unit. As the transmission / reception separating unit 32, a circulator or a directional coupler is preferably used.

The control unit 44 includes a CPU, a ROM, a RAM, and the like, and is a so-called microcomputer that performs signal processing in accordance with a program pre-stored in the ROM while using a temporary storage function of the RAM. The communication shown in Fig. 1 is based on the basic control of the transmission operation of the interrogation wave F to the tag 14 and the reception operation of the response wave F returned from the wireless tag 14 in response to the interrogation wave F. The distance detection control for detecting the distance d from the target wireless tag 14 is executed. In order to execute such control, while controlling the PLL 18 and the VCO 20 and supplying a control signal TX-PWR to the transmission signal amplifying unit, a plurality of types of interrogation waves F having different frequencies are transmitted from the antenna 26 to the antenna 26. An interrogation wave transmitter 50 for transmitting to the wireless tag 14 and the antenna 26 based on the I-phase signal and the Q-phase signal output from the I-phase signal amplifier 36 and the Q-phase signal amplifier 40, respectively. A signal processing unit 52 that performs quadrature demodulation of the received signal and performs signal processing such as supplying a control signal TX-ASK to the main carrier modulation unit 22, and a plurality of types of response waves by the signal processing unit 52. A distance calculator 54 for calculating a distance d from the wireless tag 14 based on the demodulation result of F is functionally included.

FIG. 3 is a block diagram illustrating a wireless tag circuit 56 included in the wireless tag 14. As shown in FIG. 3, the wireless tag 14 receives the interrogation wave F from the wireless tag communication device 12, and responds to the wireless tag communication device 12 in response to the interrogation wave F. An antenna 58 for transmitting, an interrogation wave received by the antenna unit 58, a clock unit 60 for extracting a clock signal, generating a subcarrier, and supplying it to the control unit 66, and an interrogation received by the antenna 58 A power supply unit 62 for rectifying a part of the wave F to be an energy source, a modulation / demodulation unit 64 connected to the antenna 58 for modulating and demodulating a signal, and controlling operations of the wireless tag circuit 56. It comprises a control unit 66 and a memory unit 68 capable of storing and reading out predetermined information. The control unit 66 controls the storage of the predetermined information in the memory unit 68 by communicating with the wireless tag generation device 12 and the Z-modulation of the interrogation wave F received by the antenna unit 58. In the section 64, based on the information signal stored in the memory section 68, basic control such as return control is performed, in which the signal is modulated and then reflected and returned from the antenna section 58 as a response wave F. .

FIG. 4 is a diagram exemplifying a subcarrier used for the reply control by the control unit 66 and a code signal in which the subcarrier is encoded by a predetermined information signal. When the interrogation wave F from the RFID tag communication device 12 is received by the antenna 58, the clock unit 60 uses the part of the interrogation wave F rectified by the power supply unit 62 as an energy source, and A subcarrier is generated. Next, the control unit 66 analyzes the command frame, encodes the subcarrier based on the information signal stored in the memory unit 68 (primary modulation), and sends it to the variable Z demodulation unit 64. Is entered. For example, the data 1 shown in FIG. 4 performs coding using a subcarrier, and the data 0 uses a subcarrier. There is no sign. The interrogation wave F received from the wireless tag communication device 12 is modulated (secondary modulated) based on the encoded signal by the modulation / demodulation unit 64, and the response wave F is received from the antenna 58 as the response wave F. Sent to wireless tag communication device 12. The frequency of the sub-carrier is set in advance so as to be included in the pass bands of the I-phase signal BPF34 and the Q-phase signal BPF38.

FIG. 5 is a flowchart illustrating the tag position detection control by the control unit 44 of the wireless tag communication device 12, which is repeatedly executed at a predetermined cycle. FIG. 6 is a flowchart illustrating the tag position determination control in the SB in FIG. 5.

First, in step (hereinafter, step is omitted) SA 1, the frequency f of the main carrier generated by the VCO 20 is set to f by the PLL 18. This frequency f c is 2πω, where ω is the angular frequency of the main carrier. Next, in SA2, after the main carrier is amplitude-modulated by the main carrier modulation unit 22 based on a predetermined control signal TX-ASK to be a transmission signal, based on the predetermined control signal TX-PWR, The signal is amplified by the transmission signal amplifying unit 24 and transmitted from the antenna 26 to the wireless tag 14 as an interrogation wave F. This interrogation wave F is represented by the following equation (1), where the amplitude is Α.

[0029] [number 1]

Next, in SA3, the response wave F returned from the wireless tag 14 in response to the interrogation wave F transmitted in SA2 is received by the antenna 26. The response wave F is expressed by the following equation (2) in the data 1 shown in FIG. In the equation (2), ω is the angular frequency of the subcarrier, and the subcarrier f is sincot. B indicates the reflection efficiency and m indicates the degree of modulation. For example, m = l, that is, modulation with a degree of modulation of 100% is performed.

[0031] [Equation 2] r = ABsin ωοΐ X (1 + msin 6L) S

Next, in SA 3 ′, the transmission of the interrogation wave F _e is stopped in the same manner as in SA 9 described later.

Next, in SA4, the phase difference の between the interrogation wave F and the response wave F generated by the reciprocation of the radio wave in the communication between the wireless tag communication device 12 and the wireless tag 14 is calculated, and the tag position is calculated. The candidate sequence d is determined. The received signal R received by the antenna 26 is

1 s

It is expressed as the following equation (3), where C is the attenuation factor due to round trip. This received signal R

s

Converted to I-phase signal R and Q-phase signal R by phase signal converter 28 and Q phase signal converter 30

si sq. The I-phase signal R is represented by the following equation (4), and the signal passing through the I-phase signal BPF34 and input to the control unit 44 is represented by the following equation (5). You. The Q-phase signal R is expressed by the following equation (6), passes through the Q-phase signal BPF38, and

Is expressed as in the following equation (7). The control unit 44 calculates tan 0, which is the ratio between the I-phase signal R and the Q-phase signal R, according to the following equation (8).

si sq c

If the signal R force is greater than or equal to ^, 0 is calculated as in the following equation (9). If the Q phase signal is less than the R force ^) sq c sq, Θ is calculated as in the following equation (10). Is calculated. In the equations (9) and (10), n is 0 and a natural number, and η = 0, 1, 2, 3,. R / R is indicated by R. Previous

sq si

The phase difference により generated by the radio wave going back and forth over the distance d in the communication between the wireless tag communication device 12 and the wireless tag 14 is determined by the wavelength of the interrogation wave F (= 3 × 10 ⁸ / f (m ]), If the term of 2πη is omitted, it is expressed as the following equation (11). Therefore, the minimum value of the distance D over which the radio wave reciprocates in such communication is expressed by the following equation (12), and the value obtained by adding ληΖ2 to the value of equation (12) is also the value of the wireless tag communication device. A tag position candidate sequence d that is a candidate for the distance D between the tag and the wireless tag 14 is determined.

[0034] [Equation 3]

R _s = ABCsinC 6Uct + 0 c) X (1 + msin 6L) st) [6 coagulation] [0 rinse]

(8)

[6S00]

(_) · · (VV U | SUJ ₊ t) x ³ 0uis _L [8S00]

sp u! SLU + | _) x soo x (.0+: i.P9) u! sogv— = ^bs id

[9] [ζεοο]

[S] [9S00]

() ... (^ CO UjSLU-i- 1.) X 0 SOO- ( ³ fT5 Q + ^ ()) S00} _; 2 ―

oav

[esoo] 0c2 arctanR + vert n (Q≥0)

[0041] [number 10]

0 c2 arctanR + 7T (n + 1) (Q <0)

[Equation 11] θ, = ψ ··· (")

Ac

[Equation 12] d = -¾ ^ · '· (12)

4 vault

Next, in SA5, the frequency f _{e of the} main carrier generated by the VCO 20 is set to f by the PLL 18 described above. Preferably, the frequency f set in SA5 and the frequency f

twenty two

The frequency f set in SA1 is a value that cannot be divided by each other.

Next, in SA 6, the main carrier is generated by the reference frequency generation section 16 and controlled to the frequency f set in SA 5, and based on a predetermined control signal TX-ASK,

2

After being amplitude-modulated by the main carrier modulating unit 22 to be a transmission signal, it is amplified by the transmission signal amplifying unit 24 based on a predetermined control signal TX-PWR, and is interrogated from the antenna 26 as an interrogation wave F by the radio tag. Sent to 14.

Next, in SA8, the wireless tag 14 transmits the The returned response wave is received by the antenna 26. Next, in SA8, the phase difference 0 generated by the reciprocation of the radio wave in the communication between the wireless tag communication device 12 and the wireless tag 14 is calculated by the same processing as SA4 described above, and the tag position candidate sequence d is calculated. Decision

2 2 is set. Next, in SA9, the oscillation of the VCO 20 is stopped, and the transmission of the interrogation wave F from the antenna 26 is stopped. Then, after the tag position determination control of the candidate row force shown in FIG. 6 is performed, the present routine is terminated.

In the tag position determination control from the candidate sequence shown in FIG. 6, first, in SB1, n and n (

1 2 n and n) corresponding to f and f are both set to 0. Next, at SB2, (12)

1 2

Expression forces d and d are calculated. Next, in SB3, it is determined whether or not I d — d I is less than the predetermined value E. If the determination at SB3 is affirmative, at SB4, the distance between the wireless tag communication device 12 and the wireless tag 14 (the distance between the antenna 24 of the wireless tag communication device 12 and the antenna 58 of the wireless tag 14) is determined. After determining that D is d, this routine is terminated.If the determination of SB3 is denied, it is determined in SB5 whether n is S3. You. If the judgment of SB5 is denied, then in SB8, 1 is added to n, and then the force at which the processing of SB2 and below is executed again If the judgment of SB5 is affirmed, at SB6, It is determined whether or not the force is n ^. This SB6 format

2

If the determination is affirmative, the error is determined to be an error at SB7, and then, if the determination of the force SB6 at which this routine is terminated is denied, the force is determined to be n at SB9, and to SB10 at SB10. , N is incremented by 1, and then the processing of SB2 and below is executed again. More than

2

In the control, SA1, SA2, SA5, and SA6 calculate the operation of the interrogation wave transmitting unit 50, SA3 and SA7 calculate the distance of the signal processing unit 52 (reception demodulation unit), and SA4, SA8, and SB calculate the distance. It corresponds to the operation of the unit 54, respectively. In SB3's judgment, | d—d

It is determined whether or not 1 2 I is less than the predetermined value E.However, this is because the solution is not determined based on the expected measurement error and the distance to the wireless tag 14 cannot be obtained. This is determined in consideration of the accuracy of the plurality of candidate tag positions dl and d2 and the upper limit of the natural number determined by SB5 and SB6 (3 in this embodiment).

FIG. 7 is a diagram illustrating the principle of the tag position detection control. The distance calculation unit 54 performs a plurality of types of responses returned from the wireless tag 14 in response to the plurality of types of interrogation waves F. The distance D from the wireless tag 14 is calculated based on the result of demodulation of the response wave ^. In this embodiment, the response wave F returned from the wireless tag 14 In a mode in which the distance D between the wireless tag 14 and the signal R is calculated based on the ratio between the signal R and the Q-phase signal R, sq

Is explained. In the tag position detection control shown in the flowchart of FIG. 5, the first interrogation wave having the frequency f and the second interrogation wave having the frequency f are generated by the interrogation wave transmitting section 50.

1 2

The first response wave and the second response wave transmitted alternately and returned from the wireless tag 14 according to the first and second interrogation waves are received and demodulated respectively. Then, the first distance candidate group (candidate sequence) d obtained by the distance calculation unit 54 based on the demodulation result of the first response wave, and the second distance candidate group d obtained based on the demodulation result of the second response wave Are compared with the first distance candidate group d and the second distance candidate group d.

2 1 2 The smallest value among the values included in common, that is, the value corresponding to n = 1, n = 1,

1 2

The distance D from the wireless tag 14 is calculated. In this embodiment, nl = l and n2 = l.

FIG. 8 is a flowchart illustrating another example of the tag position detection control by the control unit 44 of the wireless tag communication device 12, which is repeatedly executed at a predetermined cycle. Note that, in this embodiment, as shown in FIG. 11, a first wireless tag communication device 12a for generating a main carrier having a frequency f and a frequency f which is a value that is indivisible from each other.

A second wireless tag communication device 12b for generating 12 main carriers is separately provided, and information is transmitted between the wireless tag communication devices 12a and 12b and the wireless tag 14, respectively. The communication with the wireless tag 14 is calculated by the communication of the wireless tag and the control. Further, since the wireless tag communication devices 12a and 12b communicate with the same wireless tag 14, they are controlled so as to communicate at different timings. Alternatively, when communication is performed simultaneously, the content and timing are controlled so as to transmit the same interrogation wave only with a different frequency in order to perform communication with the same wireless tag 14.

First, at SC1, the frequency f of the main carrier generated by the VCO 20 is set to f 1 and f 2 by the PLL 18 described above. Next, at SC2, the first wireless tag communication

1 2

After the main carrier having the frequency f generated in the device 12a is amplitude-modulated by the main carrier modulator 22 based on a predetermined control signal TX-ASK to be a transmission signal, The signal is amplified by the transmission signal amplifying unit 24 based on the fixed control signal TX-PWR, and is transmitted from the antenna 26 to the wireless tag 14 as an interrogation wave F. In addition, the above-mentioned cl

In the wireless tag communication device 12b of No. 2, the unmodulated main carrier of the frequency f increases the transmission signal.

2

Amplified by the width portion 24 and directed from the antenna 26 to the wireless tag 14 as an interrogation wave F c2

Sent. That is, the first interrogation wave having the frequency f1 and the second interrogation wave having the frequency f2 are transmitted simultaneously to the wireless tag 14. Next, in SC3 corresponding to the operation of the signal processing unit 52, the first response wave returned from the wireless tag 14 in response to the first interrogation wave and the second interrogation wave transmitted in SC2, and A second response wave is received by the antenna 26.

Next, in SC4, the phase difference 0, する generated by the reciprocation of the radio wave in the communication between the wireless tag communication device 12 and the wireless tag 14 is calculated, and the tag position candidate strings d, d are determined. Is determined. The phase difference 0 is a value corresponding to the first interrogation wave of the frequency f. Based on the phase difference Θ and the wavelength of the interrogation wave, the first distance candidate group d as shown in the following equation (13) is obtained. (The term of λ ηΖ2 is omitted). The phase difference Θ is the frequency

2 f

22 This is a value corresponding to the interrogation wave of 2, and similarly based on the phase difference 0 and the wavelength 2 of the interrogation wave, the following (14)

2

), The second group of distance candidates d is obtained (λ

2 The term of ηΖ2 is omitted).

[0052] [Number 13]

[0053] [Number 14]

θ 2 λ

d ₂ = '(14)

4π

Next, in SC5, it is determined whether or not the received signal strength detected by the RSSI circuit 42 is less than a predetermined value K1, that is, whether or not the received signal strength is relatively small! . If the determination at SC5 is affirmative, the power at which the processing below SC10 is executed after n = 0 is set at SC6.If the determination at SC5 is negative, the RSSI circuit is set at SC7. It is determined whether the received signal strength detected by 42 is less than a predetermined value K2 (a value larger than K1), that is, whether the received signal strength is medium. If the determination in SC7 is affirmative, in SC8, η is set to 1 and then the processing below SC10 is performed.However, when the determination in SC7 is denied, that is, the received signal strength is compared. If it is determined that the target value is large, it is determined that η = 2 in SC9, and then it is determined in SC10 whether n has been determined for both of the frequencies f 1 and f 2. This SC10 decision

1 2

If the determination is negative, the power at which the processing below SC5 is executed again If the determination of SC10 is affirmative, the transmission of the interrogation wave F from the antenna 26 is stopped at SC11. Will be terminated. Since the distance between the wireless tag communication device 12 and the wireless tag 14 is constant, n, n (f, f

1 2 1 2 1 2 The corresponding n) is obtained. In the above control, SC1 and SC2 correspond to the operation of the interrogation wave transmitting unit 50, and SC4 to SC10 correspond to the operation of the distance calculating unit 54, respectively. Note that the frequencies f and f

Numeral 1 2 is selected such that the wavelengths 1 and λ 2 satisfy the following formula (15) with respect to the communicable distance Da with the wireless tag 14. Further, the wavelength difference between the frequencies f 1 and f 2 illustrated in FIG. 7 is more than the distance error corresponding to the phase measurement error.

1 2

It is set to be large so that the selection of n is not mistaken due to the measurement error.

[0055] [Number 15]

Da≥ ^-· '· (15)

As described above, according to the present embodiment, the interrogation wave transmitter 50 (SA1, SA2, SA5, SA6, SC1, and SC2) for transmitting a plurality of types of interrogation waves F having different frequencies, A reception demodulation unit for receiving and demodulating a plurality of types of response waves F returned from the wireless tag 14 in response to the plurality of types of interrogation waves F _e transmitted from the interrogation wave transmitting unit 50. That is, based on the I-phase signal conversion unit 28 and the Q-phase signal conversion unit 30 and the demodulation results of a plurality of types of response waves F by the I-phase signal conversion unit 28 and the Q-phase signal conversion unit 30, And a distance calculation unit 54 (SA4, SA8, SB, SC5 to SC10) for calculating a distance d between the wireless tag 14 and the wireless tag 14 by performing communication with the wireless tag 14. The distance d from 14 can be suitably obtained. That is, it is possible to provide the wireless tag communication device 12 capable of detecting the distance from the wireless tag 14.

The signal processing unit 52 (SA3 and SA7) converts the response wave F returned from the wireless tag 14 into an I-phase signal R and a Q-phase signal R, which are orthogonal to each other, and performs orthogonal demodulation. r si sq

Therefore, the distance from the wireless tag 14 can be suitably obtained in the wireless tag communication device 12 including the demodulation circuit of the quadrature detection method.

[0058] Further, the distance calculation unit 54 determines the distance between the wireless tag 14 based on the ratio between the I-phase signal R and the Q-phase signal R, in which the response wave F returned from the wireless tag 14 is also converted. Calculate the distance d

si sq

Therefore, the distance from the wireless tag 14 can be determined in a practical manner in the wireless tag communication device 12 including the orthogonal detection type demodulation circuit.

[0059] Further, the interrogation wave transmitting section 50 transmits a first interrogation wave and a second interrogation wave having different frequencies, and the signal processing section 52 transmits the interrogation wave from the interrogation wave transmission section 50. It is necessary to receive and demodulate the first response wave and the second response wave returned from the wireless tag 14 in response to the first and second interrogation waves received, respectively. Thus, a sufficient distance between the wireless tag 14 and the interrogation wave F and the response wave F can be suitably obtained.

Further, since the frequencies of the first interrogation wave and the second interrogation wave are indivisible values from each other, the distance between the first interrogation wave and the second interrogation wave can be more preferably obtained.

[0061] Further, the distance calculation unit 54 determines a first distance candidate group d obtained based on the demodulation result of the first response wave and a second distance candidate group d obtained based on the demodulation result of the second response wave. The first distance candidate group d and the second distance candidate group d are compared with the second distance candidate group d.

Since the minimum value among the values included in the data is calculated as the distance D to the wireless tag 14, the distance to the wireless tag 14 can be obtained in a practical manner. it can [0062] Further, since the interrogation wave transmitter 50 transmits the first interrogation wave and the second interrogation wave alternately, the interrogation wave transmitter 50 transmits a necessary and sufficient interrogation wave F with a simple configuration. be able to.

[0063] Further, since the interrogation wave transmitter 50 transmits the plurality of types of interrogation waves F at the same time, the distance D to the wireless tag 14 can be obtained as quickly as possible.

Further, the distance calculation unit 54 calculates the distance D to the wireless tag 14 based on the intensity of the response wave F returned from the wireless tag 14, so that it is more preferable. The distance d from the wireless tag 14 can be obtained.

Since the distance calculation unit 54 calculates the distance to the wireless tag 14 based on the communicable distance D to the wireless tag 14, the wireless tag 14 is more preferably used. The distance D from the object 14 can be obtained.

Example 2

Next, another preferred embodiment of the present invention will be described in detail with reference to the drawings. In the drawings used in the following description, the same parts as those in the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 9 is a diagram illustrating an electrical configuration of a wireless tag communication device 70 according to a second embodiment of the present invention. As shown in FIG. 2, the wireless tag communication device 70 of the second embodiment distributes the main carrier of the interrogation wave F output from the reference frequency generation unit 16 and performs the distribution based on a predetermined phase control signal. A phase shift circuit 72 for controlling the phase of the received signal; a reception demodulation unit 74 for homodyne demodulating the received signal received by the antenna 26 based on the phase-controlled main carrier supplied from the phase shift circuit 72; A demodulation signal BPF for extracting only a signal of a predetermined frequency band from the demodulation signal output from the reception demodulation unit 74; and a demodulation signal amplifying unit 78 for amplifying the demodulation signal output from the demodulation signal BPF. It is configured. The RSSI 42 in the wireless tag communication device 70 detects the signal strength of the demodulated signal output from the demodulated signal amplifier 78. Further, the control unit 44 of the wireless tag communication device 70 of the second embodiment is functionally provided with a carrier phase control unit 80 for supplying a predetermined phase control signal to the phase circuit 72.

FIG. 10 illustrates tag position detection control by the control unit 44 of the wireless tag communication device 70. This flowchart is repeatedly executed at a predetermined cycle.

First, in SD 1, the frequency f of the main carrier generated by the reference frequency generator 16 is set to f by the PLL 18, and is fixed to the frequency f by the VCO 20. Next, in SD2, the main carrier is generated by the reference frequency generation unit 16 and controlled to the frequency f set in SD1, and is controlled by the main carrier modulation unit 22 based on a predetermined control signal TX-ASK. After being amplitude-modulated to be a transmission signal, the signal is amplified by the transmission signal amplifying section 24 based on a predetermined control signal TX-PWR and transmitted from the antenna 26 to the wireless tag 14 as an interrogation wave F. You.

Next, in SD3, the phase control amount φ in the phase shift circuit 72 and the RSSI force which is the maximum value of the RSSI are both set to 0. Next, in SD4, the question sent in SD2

max

A response wave F returned from the wireless tag 14 in response to the wave F is received by the antenna 26, and is received by the reception demodulation unit 74 based on the phase-controlled main carrier supplied from the phase shift circuit 72. And is homodyne demodulated. Then, the RSSI 42 detects the signal strength RSSI of the demodulated signal output from the reception demodulation unit 74. The demodulated signal output from the reception demodulation unit 74 is represented by the following equation (16), where l + msin cot is M.

s

It is.

[0071] [Number 16]

Asin (6 (J _c t + 0 _c ) X sin (dt) c + 0) XM

=-"— {Cos (ω ct + θ ο + ω ct + 0) -cos (ω _c t + θ ο- ω _c t- φ)} Μ d-+ (cos (2 ω ct + Θ c + 0) -cos (Θ c-0)} M

Next, in SD5, it is determined whether or not the demodulated signal strength RSSI detected in SD4 is larger than the maximum value RSSI. If the judgment of SD5 is denied, the power to execute the processing below SD8 If the judgment of SD5 is affirmed, the RSSI Is made its maximum value RSSI. In SD7, after the phase control amount φ is set to its maximum value φ max max, in SD8, it is determined whether or not the force whose phase control amount φ is 2π or more. If the determination in SD8 is affirmative, in SD9, after the transmission of the interrogation wave F from the antenna 26 is stopped, if the determination in SD8 to terminate this routine is denied, In SD10, after the specified value φ is added to the phase control amount φ,

The following process is performed again. As described above, the phase control amount φ in the phase shift circuit 72 is set so that the demodulated signal strength RSSI is maximized, so that the wireless communication between the wireless tag communication device 12 and the wireless tag 14 for the first frequency f. The candidate sequence 位相 of the phase difference generated by the reciprocation of the radio wave in the communication between Θ is obtained as in the following equation (17). Similarly, for the second frequency f, a candidate sequence 位相 of the phase difference is obtained as in the following equation (18). And

twenty two

N and n are obtained in the same manner as in the first embodiment, and the distance D from the wireless tag 14 is calculated.

1 2

Will be issued. In the above control, SD1 and SD2 operate as the interrogation wave transmitter 50, SD4 operates as the signal processor 52, and SD5 to SD8 and SD10 operate as the distance calculator 54 and the carrier phase controller 80. Each corresponds.

[0073] [Equation 17]

0 ι = 0ι + 2ηι 7Γ (ηι = 0,1,2, ... ")---(1 7)

[0074] [Equation 18] 0 2η ₂ 7Γ (η ₂ = 0, 1, _2, ...)---(18)

As described above, according to the second embodiment, the phase shift circuit 72 and the main carrier phase for distributing the main carrier of the interrogation wave F and controlling the phase to supply the main carrier to the reception demodulator 74 are provided. The reception / demodulation unit 74 includes a control unit 80 (SD5 to SD8, SD10) .The reception / demodulation unit 74 converts the response wave F returned from the wireless tag 14 into a main carrier having a controlled phase supplied by the phase shift circuit 72. Since the homodyne demodulation is performed based on the above, the distance D between the RFID tag 14 and the RFID tag 14 in the RFID tag communication device 70 including the demodulation circuit of the homodyne detection method can be suitably obtained.

Further, the distance calculation unit 54 is further preferable because it calculates the distance D between the wireless tag 14 and the wireless tag 14 based on the strength RSSI of the demodulated signal demodulated by the reception demodulation unit 74. The distance D from the wireless tag 14 can be obtained.

As described above, the preferred embodiment of the present invention has been described in detail with reference to the drawings. The present invention is not limited to this, and may be embodied in still another mode.

For example, in the above-described embodiment, the interrogation wave transmitting unit 50, the signal processing unit 52, the distance calculating unit 54, the main carrier phase control unit 80, and the like are all controlled by the control unit 44. Forces provided as functions Each may be provided as an individual control device.

In the above-described embodiment, the distance calculation unit 54 is returned from the wireless tag 14 in response to the first and second interrogation waves transmitted from the interrogation wave transmission unit 50. Although the distance dD with respect to the wireless tag 14 is detected based on the first response wave and the second response wave, three or more types having different frequencies transmitted from the interrogation wave transmitting unit 50 are used. Based on the same three or more response waves returned from the wireless tag 14 in response to the interrogation wave, the distance d to the wireless tag 14 may be detected. In this way, the distance D from the wireless tag 14 can be obtained more accurately.

[0080] Although not specifically exemplified, the present invention is embodied with various modifications within a range not departing from the gist thereof.

Claims

The scope of the claims

[1] A wireless tag communication device that performs non-contact information communication with a wireless tag in which predetermined information is stored,

An interrogation wave transmitting unit for transmitting a plurality of types of interrogation waves having different frequencies, and a plurality of types of response waves returned from the wireless tag in response to the plurality of types of interrogation waves transmitted from the interrogation wave transmitting unit. A reception demodulation unit for receiving and demodulating each,

A distance calculating unit for calculating a distance between the wireless tag based on a result of demodulating a plurality of types of response waves by the receiving and demodulating unit;

A wireless tag communication device comprising:

2. The wireless tag communication device according to claim 1, wherein the reception demodulation unit converts a response wave returned from the wireless tag into an I-phase signal and a Q-phase signal orthogonal to each other and performs orthogonal demodulation.

[3] The distance calculation unit calculates a distance between the wireless tag and the wireless tag based on an angle difference between the I-phase signal and the Q-phase signal converted from a response wave returned from the wireless tag. The wireless tag communication device according to claim 2.

[4] A carrier wave phase control unit for distributing the main carrier wave of the interrogation wave and controlling the phase thereof to supply the main wave to the reception demodulation unit, wherein the reception demodulation unit is a response wave returned from the wireless tag. 2. The wireless tag communication apparatus according to claim 1, wherein the signal is subjected to homodyne demodulation based on the carrier supplied by the carrier phase controller, the phase of which is controlled.

[5] The interrogation wave transmitting unit transmits a first interrogation wave and a second interrogation wave having different frequencies, and the reception demodulation unit transmits a first interrogation wave transmitted from the interrogation wave transmission unit. The wireless communication device according to any one of claims 1 to 4, wherein the first response wave and the second response wave returned from the wireless tag in response to the inquiry wave and the second inquiry wave are received and demodulated, respectively. Tag communication device.

6. The wireless tag communication device according to claim 5, wherein the frequencies of the first interrogation wave and the second interrogation wave are indivisible values.

[7] The distance calculation unit obtains a first distance candidate group obtained based on a demodulation result of the first response wave by the reception demodulation unit and a demodulation result of the second response wave. The first distance candidate group and the second distance candidate are compared with each other. 7. The wireless tag communication device according to claim 5, wherein a minimum value among values included in the group is calculated as a distance from the wireless tag.

8. The wireless tag communication device according to claim 5, wherein the interrogation wave transmitting unit transmits the first interrogation wave and the second interrogation wave alternately.

9. The wireless tag communication device according to claim 1, wherein the interrogation wave transmitting unit transmits the plurality of types of interrogation waves simultaneously.

10. The wireless tag communication device according to any one of claims 1 to 9, wherein the distance calculation unit calculates a distance between the wireless tag and the wireless tag based on an intensity of a response wave returned from the wireless tag.

11. The wireless tag communication device according to claim 1, wherein the distance calculation unit calculates a distance between the wireless tag and the wireless tag based on a communicable distance between the wireless tag and the wireless tag.