JP2010108148A - Reader/writer system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reader/writer for distinguishing passing and the direction of passing of an RFID tag by obtaining the timing when the RFID is closest to each antenna. <P>SOLUTION: A reader/writer system 100 is constituted by the reader/writer 50 including the antennas 6a, 6b, and a personal computer 60. The personal computer (control means) 60 includes: a communication part 20 which transmits/receives information to/from the reader/writer 50; a relative velocity operation means 22 which operates the relative velocity of a tag 7 and the antennas based on the delay time operated by the reader/writer 50; a closest point detection means 23 which detects the closest point of the moving line of the tag 7 and the antennas; a determination part 24 which determines passing and the direction of passing of the tag 7 from the relative velocity and the closest point; a storage part 25 which stores the name of the antenna whose closest approaching is detected; and a control part 21 which synchronizes and controls the whole. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reader / writer system, and more particularly to a technique for determining a passing direction of a non-contact information recording medium from a relative speed between an antenna and the non-contact information recording medium.

An RFID system using radio waves has a long communicable distance of several tens of centimeters to several meters even for a passive RFID tag without a power source. However, since the communicable distance with the RFID tag is determined by the characteristics of the antenna mounted on the RFID tag, RFID using a band (such as a UHF band of 1 GHz or less) in which it is difficult to realize a small antenna with a narrow directivity. Until now, the system has been able to detect the passing direction by installing multiple antennas and judging using the order of entering the reading range, but the readable range in an RFID system using radio waves Because of the vagueness, there was a problem in installation and accuracy, such as the need to greatly separate the antenna to avoid false detection.
Patent Document 1 discloses a tag communication antenna that can cover a wide communication area having no communication impossible portion with a small number of highly directional antennas.
JP 2006-20083 A

However, in the prior art disclosed in Patent Document 1, the tag communication antenna used in the reader / writer is a beam scan antenna that can scan a beam of radio waves to be transmitted, and the beam has a strong directivity in the scan direction. Because there are many constraints such as the scanning of the beam is performed so that the plane including the scanning direction intersects the floor surface, which is the reflecting surface where the strongest reflected wave is generated, the antenna is optimally used depending on the location. There is a problem that it cannot be installed at the position.
The present invention has been made in view of such a problem, and includes two antennas. Based on the delay time of the radio wave transmitted from the reader / writer and the radio wave reflected from the RFID tag, each antenna and the RFID tag It is an object of the present invention to provide a reader / writer system that can determine the passage and passing direction of an RFID tag based on the timing at which the RFID tag is closest to each antenna by obtaining the relative speed of the RFID tag.

In order to solve this problem, the present invention provides a reader / writer system that determines the passage and passing direction of a non-contact information recording medium using radio waves, and the radio waves are applied to the non-contact information recording medium. Transmitting means for transmitting; demodulating means for demodulating a reflected wave obtained by modulating a part of the radio wave by the non-contact information recording medium; calculating means for calculating a delay time of the reflected wave; A reader / writer having a plurality of antennas for reading a contact information recording medium, and a control means for controlling the reader / writer, the control means based on the delay times calculated by the computing means. The relative speed of the non-contact information recording medium in relation to the antenna is calculated, and the non-contact information recording medium is calculated based on the timing at which the non-contact information recording medium is closest to each antenna. And judging the passing and the passing direction of the broadcast recording medium.
The present invention is a reader / writer in a microwave system that communicates with a non-contact information recording medium using microwaves, and radio waves (microwaves) transmitted from the reader / writer are radiated from two antennas and are contactless information. Modulated by the recording medium and received as a reflected wave by each antenna. At this time, a delay time corresponding to the distance occurs between the transmitted radio wave and the reflected wave. The present invention determines the passage and passing direction of the non-contact information recording medium by obtaining the relative speed from the delay time between each antenna and the non-contact information recording medium at that time. Thereby, when identifying from which direction the non-contact information recording medium that has passed in front of the antenna has moved, the degree of freedom of the antenna installation position is improved.

According to a second aspect of the present invention, the control means calculates a relative speed between the non-contact information recording medium and the antenna based on a communication unit that exchanges information with the reader / writer and a delay time calculated by the reader / writer. Relative speed calculation means; closest approach point detection means for detecting the closest point between the flow line of the non-contact information recording medium and the antenna; and passage and passage of the non-contact information recording medium from the relative speed and closest point A determination unit for determining a direction, a storage unit that stores the name of the antenna where the closest approach is detected, and a control unit that performs synchronous control of the whole are provided.
The reader / writer outputs a delay time between each antenna and the non-contact information recording medium. The control means obtains the relative speed between each antenna and the non-contact information recording medium from this delay time. Also, the point at which the direction of the relative speed changes is the closest point to the antenna. Based on the obtained relative speed and the closest point, the passage and the passage direction of the non-contact information recording medium are determined. Thereby, it is possible to easily determine the passage and the passing direction of the non-contact information recording medium from a simple calculation result.
According to a third aspect of the present invention, in the case where the antenna in which the closest approach to the non-contact information recording medium is first detected and the antenna in which the closest approach is last detected are other antennas, It is determined that the non-contact information recording medium has passed in the direction of the antenna in which the closest approach was last detected from the antenna first detected.
When a plurality of antennas are arranged side by side, when the non-contact information recording medium advances in a certain direction on a straight line, the antenna closest to the non-contact information recording medium is detected first, and the closest approach is the last. There is always a detected antenna. Therefore, when detected in this order, it can be determined that the non-contact information recording medium has passed from the antenna where the closest approach was first detected to the antenna where the closest approach was last detected. Thereby, not only the passage of the non-contact information recording medium but also the direction of passage can be determined.

According to a fourth aspect of the present invention, the control means makes the non-contact information recording medium again approach the antenna where the closest approach to the non-contact information recording medium is first detected, and thereafter approaches the other antenna. If the signal is not detected, it is determined that the closest approach has been returned after approaching the first detected antenna.
The non-contact information recording medium does not always move in a certain direction on the flow line. For example, it may be turned back as it is closest to one antenna. In order to determine such a situation, the non-contact information recording medium again comes closest to the antenna where the closest approach to the non-contact information recording medium is first detected, and thereafter the closest approach to a different antenna is detected. It is to detect the case where there was no. As a result, it is possible to determine when the non-contact information recording medium that has been reversed and returned in the middle has been difficult to determine.
According to a fifth aspect of the present invention, the control means detects the closest approach to the non-contact information recording medium simultaneously by the plurality of antennas, and the closest approach is detected last from the antenna from which the closest approach is first detected. If it is not determined that the non-contact information recording medium has passed in the direction of the antenna, and if it is not determined that the closest approach has been approached to the first detected antenna and then turned back, before the plurality of antennas It is characterized in that it is determined to have turned back.
When a non-contact information recording medium is detected by a plurality of antennas at the same time, it is closest to each antenna. After that, when it is not determined that the non-contact information recording medium has passed and it is not determined that the closest approach has been approached from the direction of the first detected antenna, it is determined that the contact has been returned before a plurality of antennas. . As a result, the non-contact information recording medium that has approached the antenna but has returned as it is can be detected and removed from the control target such as door opening and closing.

According to the present invention, since the relative speed is obtained from the delay time between each antenna and the non-contact information recording medium, the passage and the passing direction of the non-contact information recording medium are determined. When identifying from which direction the recording medium has moved, the degree of freedom of the antenna installation position is improved, and as a result, it can be assured that the non-contact information recording medium has surely passed in front of the antenna. it can.
Also, the relative speed between each antenna and the non-contact information recording medium is obtained from the delay time, and the point at which the direction of the relative speed changes becomes the closest point to the antenna, and the non-contact information is based on the determined relative speed and the closest point. Since the passage and passage direction of the recording medium are determined, the passage and passage direction of the non-contact information recording medium can be easily determined from a simple calculation result.
In addition, when a plurality of antennas are arranged side by side, when the non-contact information recording medium advances in a certain direction on a straight line, the closest approach to the antenna first detected with the non-contact information recording medium is There is always an antenna detected last. Therefore, when detected in this order, it can be determined that the non-contact information recording medium has passed in the direction of the antenna in which the closest approach was last detected from the antenna in which the closest approach was first detected. In addition to the passage of the non-contact information recording medium, the direction of passage can be determined.

In addition, since the non-contact information recording medium again comes closest to the antenna where the closest approach to the non-contact information recording medium is first detected, and then detects the case where the closest approach to a different antenna is not detected, With respect to a non-contact information recording medium that has been reversed and returned in the middle, which has conventionally been difficult to determine, it is possible to determine at which point it is turned back.
When a non-contact information recording medium is detected by a plurality of antennas at the same time, it is closest to each antenna. After that, when it is not determined that the non-contact information recording medium has passed and it is not determined that the closest approach has been approached from the direction of the first detected antenna, it is determined that it has been returned before a plurality of antennas. Therefore, the non-contact information recording medium that has approached the antenna but has returned as it is can be detected and removed from the control target such as door opening and closing.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .
FIG. 1 is a block diagram of a reader / writer unit (hereinafter simply referred to as a reader / writer) according to an embodiment of the present invention. The reader / writer 50 synchronizes the phase of the output signal of the VCO 2 with the phase of the reference input signal, the VCO 2 that oscillates at a predetermined frequency based on the control voltage of the PLL circuit 1, and the transmission from the VCO 2. A modulator 3 that modulates the received signal into a microwave (radio wave), an amplifier 4 that amplifies the microwave (up to here is a transmission means), a circulator 5 that determines the direction according to the direction of the microwave, and a microwave. Then, antennas 6a and 6b that receive reflected waves from a non-contact IC tag (non-contact information recording medium) (hereinafter simply referred to as a tag) 7, an amplifier 8 that amplifies the synthesized wave synthesized by the circulator 5, and The VCO2 signal and the signal amplified by the amplifier 8 are added and superposed to demodulate the sine wave, and the VCO2 signal is phase-shifted by a 90 ° phase shifter 10. The mixer 11 that demodulates the cosine wave by adding and superimposing the signal and the signal amplified by the amplifier 8, the BPF 12 that passes only a predetermined frequency component from the signal of the mixer 9, and only the predetermined frequency component from the signal of the mixer 11 Passing BPF 13, A / D converter 14 for converting the output signal of BPF 12 into a digital signal, A / D converter 16 for converting the output signal of BPF 13 into a digital signal (so far the demodulating means), an A / D converter 14 and an A / D converter 16 for calculating a phase (the calculation means so far) and two antennas 6a and 6b arranged so that the tag 7 can be read simultaneously. ing.

In an RFID system using radio waves, a part of the radio waves (CW waves) given to the tag 7 is modulated back by the tag 7 (reflected by changing the amplitude and phase), and then the reader / writer from the tag 7 is read. 50 communication.
The “reflected wave (backscattered wave) of the radio wave transmitted by itself” is returned to the reader / writer 50. This backscattered wave is a wave reciprocated between the tag 7 and the antenna 6a or 6b. It can be considered that the wave has a delay proportional to the distance between the tag 7 and the antenna 6a or 6b with respect to the radio wave transmitted by itself.
In this embodiment, a plurality of antennas 6a and 6b are used to measure the delay of the backscattered wave from the tag 7, and the relative speed between the respective antennas 6a and 6b and the tag 7 is obtained. The presence / absence of movement and the direction of movement can be determined.

・・・（１）
とした時（Ａとθ_Cは回路による決まる一定値）、同じアンテナで受信されるタグ７からの後方散乱波は、以下のように表せる。

・・・（２）
ｌ［ｍ］はタグ−アンテナ間の距離、ｃは電波の速度［ｍ／ｓ］、Ｂは空間やタグでの減衰を表す係数、θ_Tはタグでの反射時の位相変化である。電波を利用するＲＦＩＤにおいては、タグ７からリーダライタ５０への通信を行う際、タグ７で加えられる変調により、このＢとθ_Tが変化する。
ここで、タグ７→リーダライタ５０間における通信がＡＳＫ変調により行われる場合には、１を表すシンボルに同期して遅延時間の測定を行うとする。これにより、θ_Tをタグ固有のある一定の値とする事ができる。 The present invention is a microwave reader / writer 50 that communicates with a tag 7 using microwaves, and radio waves (microwaves) transmitted from the reader / writer 50 are radiated from two antennas 6a and 6b to the tag. 7 is received as a reflected wave by the respective antennas 6a and 6b. At this time, a delay time corresponding to the distance occurs between the transmitted radio wave and the reflected wave. In the present invention, the passage and the passing direction of the tag 7 are determined by obtaining the relative speed from the delay time between the respective antennas 6a and 6b and the tag 7 at that time. As a result, when the tag 7 that has passed in front of the antennas 6a and 6b has been moved from which direction is identified, the degree of freedom of the installation positions of the antennas 6a and 6b is improved. It is possible to guarantee that the antennas 6a and 6b have passed in front of each other.
Here, CW waves transmitted from the antennas 6a and 6b connected to the reader / writer 50 are

... (1)
(A and θ _C are constant values determined by the circuit), the backscattered wave from the tag 7 received by the same antenna can be expressed as follows.

... (2)
l [m] is the distance between the tag and the antenna, c is the velocity of the radio wave [m / s], B is a coefficient representing the attenuation in the space or the tag, and θ _T is the phase change upon reflection at the tag. In RFID using radio waves, when communication from the tag 7 to the reader / writer 50 is performed, B and θ _T change due to modulation applied by the tag 7.
Here, when communication between the tag 7 and the reader / writer 50 is performed by ASK modulation, the delay time is measured in synchronization with a symbol representing 1. Thereby, θ _T can be set to a certain value specific to the tag.

In the case of BPSK modulation, it is assumed that the delay time is measured in synchronization with a symbol representing 1 or 0. As a result, θ _T can be set to a certain value θ _T1 specific to the tag or θ _T2 (= θ _T1 −π). Similarly, in other phase modulations, θ _T can be set to a certain value specific to the tag by measuring the delay time in synchronization with a certain symbol.
Thus, when communicating with the tag 7, the phase when reflected by the tag 7 is stabilized by measuring the delay time in synchronization with the symbol, and θ _T can be regarded as a constant value. it can.
In addition, by measuring the modulated backscattered wave, it becomes possible to remove the backscattered wave (reflected wave) having no change by the BPF, and there is no surrounding metal object or communication state. The influence of reflection from the tag can be eliminated.
Further, since the delay time is measured when the communication from the tag 7 to the reader / writer 50 is performed, under the protocol having the anti-collision function, the communication partner is limited to one tag. It is possible to measure the delay time, and even in an environment where there are a plurality of tags, only the backscattered wave of a specific tag is selected to measure the delay time, and the data (ID ) And the delay time can be managed in association with each other.

・・・（３）
を使用して、直交検波を行うことによって行う。
これにより、以下のＩＱ信号が得られる。

・・・（４）

・・・（５）
ここで、Ｃとθ_Rは、直交検波の操作により付加される変数であるが、Ｃは回路により決まる値であるため一定値と考える事ができる。また、ローカル信号とＣＷ波は、同じ信号源からの信号であるため、その位相差を回路により決まる一定値とみなすことができ、これにより、θ_Rも回路により決まる一定値とみなすことができる。 The measurement of the delay time of the backscattered wave is a local signal generated from the same signal source as the CW wave.

... (3)
Is used to perform quadrature detection.
Thereby, the following IQ signals are obtained.

... (4)

... (5)
Here, C and θ _R are variables added by the operation of quadrature detection, but C is a value determined by the circuit and can be considered as a constant value. Further, since the local signal and the CW wave are signals from the same signal source, the phase difference can be regarded as a constant value determined by the circuit, and thus θ _R can also be regarded as a constant value determined by the circuit. .

・・・（６）
ただし、θ_Rは回路による固有値であるため、使用するアンテナによって、値が異なる場合がある。そこで、あらかじめそれぞれのアンテナを使用した際のθ_constの値を得ておき、各アンテナにおいて測定されたθ_rから、固有のオフセット量θ_constを減算することで補正を行うこととし、その補正後の値をθ_ANTnとする。

・・・（７）
タグ７への電波の送信をアンテナ６ａとアンテナ６ｂからそれぞれ行い、その後方散乱波の遅延を同じアンテナで得たとする。この時、θ_ANT1−θ_ANT2により、タグ７−アンテナ６ａの距離ｌ₁とタグ７−アンテナ６ｂの距離ｌ₂の差のｄ＝ｌ₁−ｌ₂を得る事ができる。

・・・（８）
このとき、θ_ANT1とθ_ANT2の測定を行う間にタグ７が移動すると、その移動量が誤差となるが、この場合、θ_ANT2の測定後に、再度θ_ANT1の測定を行い平均化することで、誤差を補正できる。 Here, since θ _c · θ _T · θ _R can be regarded as constant values, θ _r can be expressed as follows.

... (6)
However, since θ _R is an eigenvalue by the circuit, the value may differ depending on the antenna to be used. Therefore, the value of θ _const when using each antenna is obtained in advance, and correction is performed by subtracting the specific offset amount θ _const from θ _r measured at each antenna. _Let θ _ANTn be the value of.

... (7)
It is assumed that radio waves are transmitted to the tag 7 from the antenna 6a and the antenna 6b, respectively, and the delay of the backscattered wave is obtained by the same antenna. At this time, the difference d = l ₁ −l ₂ between the distance l ₁ of the tag 7 and the antenna 6a and the distance l ₂ of the tag 7 and the antenna 6b can be obtained by θ _ANT1 −θ _ANT2 .

... (8)
At this time, if the tag 7 moves during the measurement of θ _ANT1 and θ _ANT2 , the amount of movement becomes an error. In this case, after the measurement of θ _ANT2 , the measurement of θ _ANT1 is performed again and averaged. The error can be corrected.

・・・（９）
そして、回路による固有値であるθ_Rの補正を、前記と同様に行い、その補正後の値をθ_ANTmnとする。

・・・（１０）
ここで、タグ７への電波の送信をあるアンテナａから行い、その後方散乱波の遅延をアンテナ６ａとアンテナ６ｂで得たとすれば、θ_ANTa1−θ_ANTa2により、タグ７−アンテナ６ａの距離ｌ₁とタグ７−アンテナ６ｂの距離ｌ₂の差のｄ＝ｌ₁−ｌ₂を得る事ができる（アンテナａはアンテナ６ａもしくはアンテナ６ｂであっても構わない）。

・・・（１１）
この場合には、二組の直交検波回路を使用して同時にθ_ANTa1とθ_ANTa2の取得を行うこともできる。また、１つの直交検波回路とアンテナ切替回路を用いて、アンテナ６ａにおいてθ_ANTa1の測定を行った後で、アンテナ切替を行い、アンテナ６ｂにおいてθ_ANTa2の取得を行ってもよい。
後者の手段を用いる場合は、θ_ANTa1とθ_ANTa2の測定を行う間にタグ７が移動すると、その差が誤差となるが、この場合、θ_ANTa2の測定後に、再度θ_ANTa1の測定を行い平均化することで、誤差を補正できる。 When transmission is performed with antenna m and reception is performed with different antenna n, when the distance between antenna m and tag 7 is 1 _m and the distance between antenna n and tag is 1 _n , Can be represented.

... (9)
Then, the correction of θ _R , which is an eigenvalue by the circuit, is performed in the same manner as described above, and the corrected value is set to θ _ANTmn .

... (10)
Here, if transmission of radio waves to the tag 7 is performed from an antenna a and the delay of the backscattered wave is obtained by the antenna 6a and the antenna 6b, the distance l between the tag 7 and the antenna 6a is _obtained by _{θANTa1− θANTa2. It} is possible to obtain d = l ₁ −l ₂ which is the difference between the distance l ₂ between ₁ and the tag 7 -antenna 6b (the antenna a may be the antenna 6a or the antenna 6b).

(11)
In this case, θ _ANTa1 and θ _ANTa2 can be simultaneously acquired using two sets of quadrature detection circuits. Further, by using one of the quadrature detection circuit and the antenna switching circuit, after performing measurement of theta _ANTa1 the antenna 6a, it performs the antenna switching may be performed to acquire theta _ANTa2 the antenna 6b.
When using the latter means, the tag 7 is moved during the measurement of theta _ANTa1 and theta _ANTa2, but the difference becomes an error, in this case, after measurement of the theta _ANTa2, average was measured again theta _ANTa1 By making it, error can be corrected.

FIG. 2 is a block diagram showing functions of the reader / writer system according to the present invention. The reader / writer system 100 includes a reader / writer 50 having antennas 6a and 6b and a PC 60. The PC (control means) 60 calculates the relative speed between the communication unit 20 that exchanges information with the reader / writer 50 and the relative speed between the tag 7 and the antenna based on the delay time calculated by the reader / writer 50. Means 22, a closest point detection means 23 for detecting the closest point between the flow line of the tag 7 and the antenna, a determination unit 24 for determining the passage and passing direction of the tag 7 from the relative speed and the closest point, The storage unit 25 stores the name of the antenna in which the approach is detected, and the control unit 21 controls the whole in synchronization.
That is, the reader / writer 50 outputs the delay time between the antennas 6 a and 6 b and the tag 7. The PC 60 obtains the relative speed between the antennas 6a and 6b and the tag 7 from the delay time. The point where the direction of the relative speed changes is the closest point to the antennas 6a and 6b. Based on the obtained relative speed and the closest point, the passage and the passing direction of the tag 7 are determined. Thereby, the passage and the passing direction of the tag 7 can be easily determined from a simple calculation result.

FIG. 3A is a diagram illustrating an operation in which the reader / writer according to the first embodiment of the present invention detects the passage and the passing direction of the tag. A circle 23 represents the equidistant range to the point 21 when the tag flow line 20 is closest to the antenna 6a, and a circle 24 is a point when the tag flow line 20 is closest to the antenna 6b. The range of equidistant to 22 is represented. In the present invention, a plurality of antennas (two in the present embodiment) 6a and 6b are prepared, and the points where the antennas 6a and 6b and the flow line 20 of the target tag are the shortest (perpendicular to the flow line 20). Point) Install so that 21 and 22 are different. The timing at which the tag is closest to each antenna 6a, 6b is obtained from the change in the distance (relative speed) of the tag to each antenna 6a, 6b, and the passage and passing direction of the tag are determined as follows. As shown in FIG. 3A, when the antenna 6a that has detected the closest approach first differs from the antenna 6b that has detected the closest approach, it is determined that the antenna 6a has passed in the direction of the antenna 6b.
That is, when the two antennas 6a and 6b are arranged side by side, when the tag advances in a certain direction on the straight line 20, the antenna 6a in which the closest approach to the tag is detected first, and the closest approach is detected last. There is always an antenna 6b. Therefore, when detected in this order, it can be determined that the tag has passed from the antenna 6a in which the closest approach is first detected to the antenna 6b in which the closest approach is detected last. Thereby, not only the passage of the tag but also the direction of passage can be determined.

FIG. 3B is a diagram illustrating an operation in which the reader / writer according to the second embodiment of the present invention detects the passage of the tag and the passage direction. When the first and last closest antennas are detected at the same time (the antenna 6a first detected at the point 25 is closest again at the point 26, and thereafter the closest approach to the different antenna 6b is detected. If not, it is determined that it has come back from the direction of the antenna 6a and turned back. However, if the closest approach is to a plurality of antennas at the same time, it is ignored.
That is, the tag does not always move on the flow line 27 in a certain direction. For example, the closest antenna 6a may be brought back as it is. In order to determine such a situation, it is detected that the tag is again closest to the antenna 6a where the closest approach to the tag is first detected, and thereafter the closest approach to the different antenna 6b is not detected. That is. As a result, it is possible to determine at which point the tag has been turned back for a tag that has been reversed and returned in the middle, which has conventionally been difficult to determine.

  FIG. 3C is a diagram for explaining an operation in which the reader / writer according to the third embodiment of the present invention detects the passage and the passage direction of the tag. At the same time, when the closest approach is detected by the plurality of antennas 6a and 6b at the point 29 and neither the above-mentioned FIG. 3 (a) or FIG. 3 (b) is detected, it is determined that the movement is turned back. That is, when a tag is detected by two antennas 6a and 6b at the same time, it means that the antennas 6a and 6b are closest to each other. Thereafter, it is not determined that the tag has passed (in the case of FIG. 3A), and it is not determined that the closest approach has been approached from the direction of the antenna 6a that was first detected (in FIG. 3B). In the case), it is determined that the two antennas 6a and 6b are turned back. As a result, the tag that has approached the antennas 6a and 6b but has returned as it is can be detected and removed from the control target. Further, it is possible to perform detection with higher accuracy by adding information on relative speed. That is, the movement away from any antenna is not detected in the movement before the closest approach to the antenna 6a for the first time, and the movement after the closest approach to the antenna 6b is finally detected for any of the antennas. If no approaching movement is detected, it is determined that the antenna 6a has passed in the direction of the antenna 6b. Further, when the movement away from the antenna 6a is indicated and the movement toward the antenna 6b is indicated, it is determined that the tag is passing (exists between the antenna 6a and the antenna 6b). To do.

  FIG. 4 is a flowchart for explaining the operation of the PC that controls the operation of FIG. The PC 60 detects whether the reader / writer 50 has detected the closest approach by the two antennas 6a and 6b at the same time by the closest approach detecting means 23 (S1). As a result, when re-approaching is detected at the same time (YES in S1), the determination unit 24 determines that it has turned back before the antenna (in the case of FIG. 3C) (S9). When the closest approach detection unit 23 detects that the closest approach is not detected at the same time in step S1 (NO in S1), it is verified whether there is an antenna in which the closest approach is detected first (S2). If not (NO in S2), return to Step S1 and repeat. When the closest approach is first detected (YES in S2), the antenna name X is stored in the storage means 25 (S3). Next, the closest approach detection means 23 verifies whether there is an antenna that has been detected as being closest (S4). Finally, when the closest approach is detected (YES in S4), the antenna name Y is stored in the storage means 25 (S5). Then, it is determined whether or not the antenna names X and Y stored in the storage means 25 are the same (S6). If they are equal (YES in S6), it is determined that they have been exchanged after coming from the antenna X direction ((b) of FIG. 3). )) (S8). On the other hand, if the antenna names are not equal in step S6 (NO in S6), it is determined that the antenna X has passed in the antenna Y direction (in the case of FIG. 3A) (S7).

  FIG. 5 is a diagram for explaining an operation in which the reader / writer detects the passage and the passing direction of the tag using three antennas. In FIG. 5, the shortest distance point to the antenna 6a with respect to the flow line 36 of the tag 1 is 30, the shortest distance point to the antenna 6b is 31, and the shortest distance point to the antenna 6c is 32. The point of the shortest distance to the antenna 6a with respect to the flow line 37 is 33, the point of the shortest distance to the antenna 6b is 35, and the point of the shortest distance to the antenna 6c is 34. Each point is at a position where each antenna and the flow line are orthogonal to each other. For example, the operation when passing through the flow line 36 of the tag 1 in the direction of the arrow will be described. The timing at which the tag is closest to each antenna 6a, 6b, 6c is obtained from the change (relative speed) of the distance of the tag 1 with respect to each antenna 6a, 6b, 6c. Judging. From FIG. 5, when the antenna 6a at which the closest approach is first detected at the point 30 is different from the antenna 6c at which the closest approach is finally detected at the point 32, it is determined that the antenna 6a has passed in the direction of the antenna 6c. . Similarly, regarding the operation when passing through the flow line 37 of the tag 2 in the direction of the arrow, from the change (relative speed) of the distance of the tag 2 with respect to the respective antennas 6a, 6b, 6c, the respective antennas 6a, 6c, The timing at which the tag is closest to 6b is obtained, and the passage and the passing direction of the tag are determined as follows. From FIG. 5, when the antenna 6a at which the closest approach is first detected at the point 33 and the antenna 6b at which the closest approach is detected at the point 35 are different, it is determined that the antenna 6a has passed in the direction of the antenna 6b. .

1 is a block diagram of a reader / writer according to an embodiment of the present invention. It is a block diagram showing the function of the reader / writer system concerning this invention. (A) is a figure explaining the operation | movement which the reader / writer concerning the 1st Embodiment of this invention detects the passage and passage direction of a tag, (b) is the reader / writer concerning the 2nd Embodiment of this invention, and a tag FIG. 6C is a diagram for explaining the operation of detecting the passage and passage direction of the tag by the reader / writer according to the third embodiment of the present invention. It is a flowchart explaining operation | movement of PC which controls operation | movement of FIG. It is a figure explaining the operation | movement which a reader / writer detects the passage of a tag, and a passage direction with three antennas.

Explanation of symbols

  1 PLL circuit, 2 VCO, 3 modulator, 4, 8 amplifier, 5 circulator, 6a, 6b antenna, 7 tag, 9, 11 mixer, 12, 13 BPF, 14, 16 A / D converter, 15 calculator, 20 Communication unit, 21 control unit, 22 relative speed calculation unit, 23 closest approach detection unit, 24 determination unit, 25 storage unit, 50 reader / writer, 60 PC, 100 reader / writer system

Claims (5)

A reader / writer system that uses radio waves to determine whether or not a non-contact information recording medium has passed,
Transmitting means for transmitting radio waves to the non-contact information recording medium, demodulating means for demodulating reflected waves obtained by modulating a part of the radio waves by the non-contact information recording medium, and calculating a delay time of the reflected waves A reader / writer having calculation means and a plurality of antennas for reading the target non-contact information recording medium;
Control means for controlling the reader / writer,
The control means calculates a relative speed of the non-contact information recording medium in relation to each antenna based on the delay time calculated by the arithmetic means, and the non-contact information recording medium is closest to each antenna. The reader / writer system is characterized by determining whether or not the non-contact information recording medium passes and the passing direction based on the determined timing.   The control means includes a communication unit that exchanges information with the reader / writer, and a relative speed calculation means that calculates a relative speed between the non-contact information recording medium and the antenna based on a delay time calculated by the reader / writer. , A closest point detecting means for detecting a closest point between the flow line of the non-contact information recording medium and the antenna, and a determination for determining a passage and a passing direction of the non-contact information recording medium from the relative speed and the closest point 2. The reader / writer system according to claim 1, further comprising: a storage unit that stores an antenna name at which the closest approach is detected; and a control unit that performs synchronous control of the entire unit.   The control means detects the closest approach first when the antenna in which the closest approach to the non-contact information recording medium is first detected is different from the antenna in which the closest approach is detected last. 3. The reader / writer system according to claim 1, wherein it is determined that the non-contact information recording medium has passed in a direction of an antenna in which the closest approach is detected from an antenna.   The control means, the non-contact information recording medium again approaches the antenna where the closest approach to the non-contact information recording medium was first detected, and thereafter, the closest approach to another antenna was not detected 3. The reader / writer system according to claim 1, wherein the reader / writer system determines that the closest approach has been turned back after approaching the first detected antenna.   The control means detects the closest approach to the non-contact information recording medium simultaneously by the plurality of antennas, and moves from the antenna where the closest approach is first detected to the antenna where the closest approach is detected last. If it is not determined that the non-contact information recording medium has passed, and it is not determined that the closest approach has returned after approaching the first detected antenna, it is determined that the contact has been returned before the plurality of antennas. The reader / writer system according to claim 1 or 2.

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