JP3329001B2 - Identification system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distribution system for managing tools and products and an identification system used for identifying a human body.

[0002]

2. Description of the Related Art Conventionally, in order to mechanize the identification of parts and products on an assembly and transfer line, a system for identifying and managing various articles such as tools, parts, and products is required. A system for managing visitors is required. Therefore, as shown in Japanese Patent Application Laid-Open No. 1-151832,
There has been proposed an identification system in which a data carrier having a memory is provided in an identification target, necessary information is written to such a memory by data transmission from the outside, and the information is read as necessary. .

[0003] Such a conventional identification system comprises a write / read control unit comprising an ID controller 1 and a read / write antenna (RWH) 2 and a data carrier 3 as shown in FIG. The transmitting section of the ID controller 1 intermittently oscillates at a constant frequency, and changes the duty ratio to transmit a binary signal to the data carrier 3 via the read / write antenna 2. If a signal with a constant duty ratio is sent when receiving data,
The reverberation is controlled by a resonance circuit in the data carrier. Then, the reverberation signal obtained via the read / write antenna 2 is determined by the ID controller and the signal is received.

[0004]

However, in such an identification system, when the read / write antenna receives data, it is necessary to determine the presence or absence of reverberation. Since such a reverberation vibration has an extremely low level, when the read / write antenna 5 of another identification system is installed close to the read / write antenna, if the other read / write antenna 5 has the same frequency, A strong carrier signal is received by the read / write antenna 2. Therefore, there is a disadvantage that a minute reverberation signal cannot be detected and normal communication with the data carrier 3 cannot be performed.
In order to solve such a defect, it is conceivable that adjacent read / write antennas are operated alternately in a time-division manner so that a plurality of read / write antennas do not oscillate in the same time zone. However, such time-division control not only complicates the structure, but also has the disadvantage that the communication time with the data carrier is long.

[0005] The present invention has been made in view of such a conventional problem, and it is possible to prevent mutual interference without lengthening the communication time when a plurality of read / write antennas are installed close to each other. Is a technical issue.

[0006]

According to a first aspect of the present invention, there is provided an identification system comprising a data carrier, and a write / read control unit for transmitting data to the data carrier and receiving the transmitted data. The write / read control unit is provided on a surface facing the data carrier,
A read / write antenna including a transmission coil for transmitting a signal to a data carrier and a reception coil for receiving reverberation vibration from the data carrier, and a carrier signal intermittent based on the transmission signal, and the transmission coil of the read / write antenna is driven. A transmission unit for transmitting a signal to a data carrier, and a reception unit including a synchronous detection unit for synchronously detecting a resonance signal obtained in a reception coil of the read / write antenna together with the carrier signal; It has a carrier signal source for providing a common carrier signal to a plurality of adjacent write / read control units.

According to the invention of claim 2 of the present application, the receiving section performs envelope detection of reverberation vibration obtained in the receiving coil of the read / write antenna, and determines an binary signal based on the level thereof; A synchronous detector for synchronously detecting a signal obtained in a receiving coil of a read / write antenna with a carrier signal of a transmitter, and a switching means for switching to a synchronous detector when a reception level is reduced and a detection signal is not obtained from an envelope detector. And characterized in that:

[0008]

According to the first aspect of the present invention having such a feature, in a plurality of identification systems including a plurality of write / read control units, a signal source of a carrier signal is used in an adjacent write / read control unit. Is common. Then, the transmission section of the write / read control unit performs data transmission with the data carriers arriving at the corresponding areas by interrupting the carrier signal. The receiving section performs synchronous detection of the carrier signal and the signal received from the data carrier. In this case, the signal from the adjacent write / read control unit is 9 times the carrier signal.
Since it has a phase difference of 0 °, its signal component is removed by synchronous detection. Since the reverberation reception signal from the data carrier has the same phase as that of the carrier signal or a phase difference of 180 °, only the signal from the data carrier is extracted.

Further, the invention according to claim 2 of the present application has an envelope detector for performing envelope detection and a synchronous detector for performing synchronous detection. Only when the output level from the envelope detector decreases. Switching to synchronous detection is performed by switching means. If the data carriers are close to each other, the synchronous detection may not operate normally due to the phase shift due to the influence of the strong magnetic field. If the envelope detection output of the received signal from the data carrier is sufficiently high, the data carrier is close to the data carrier. Therefore, by selecting the envelope detection, a malfunction due to the phase shift of the synchronous detection can be prevented.

[0010]

FIG. 1 is a schematic diagram showing the configuration of an identification system according to one embodiment of the present invention. As shown in the figure, the host computer 11 has a plurality of ID controllers 12 and 1
3 are connected. In this embodiment, the ID controllers 12 and 13 have the same configuration, and receive the same carrier frequency f from the oscillation circuit 14 which is a common carrier signal source.
It is assumed that the carrier signal of c is supplied. The ID controllers 12 and 13 have read / write antennas (RWA) A and B, respectively. ID controller 1
2 and the read / write antenna A, and the ID controller 13 and the read / write antenna B constitute two sets of write / read control units. These write / read control units are configured to perform data communication with the data carriers (DC) 15 and 16 from these read / write antennas A and B, respectively. The read / write antennas A and B have a transmission coil L1 and a reception coil L2, respectively, as described later. Then, the ID controllers 12 and 13 appropriately change the duty ratio using the same carrier signal having the same frequency and phase,
The signal is transmitted to the data carrier via the read / write antennas A and B, respectively, and the signal is received according to the presence or absence of the reverberation.

As shown in FIG. 1, the read / write antennas A and B perform data communication with a data carrier when a data carrier arrives in its communication area. However, when the read / write antennas A and B are close to each other as described above, mutual interference occurs, and the signal transmitted from the read / write antenna B may be directly received by the read / write antenna A. FIG. 2 shows an internal circuit of the read / write antenna A and the ID controller 12. A transmission unit 17 intermittently carries out a carrier signal of the frequency fc based on the transmission data TXD.
The transmission coil L1 is driven. Thus, the transmission signals from the respective transmission coils of the read / write antennas A and B are represented by the following equations a and b, respectively. a = Ar ₁ (t) cos ωt b = Br ₂ (t) cos ωt A, B: amplitude level r ₁ (t): read / write antenna A interrogation signal r ₂ (t): read / write antenna B interrogation signal

The signal of the read / write antenna A is transmitted to a data carrier 15 for performing data communication with the read / write antenna A.
And the signal whose reverberation is controlled during transmission from the data carrier 15 is input to the read / write antenna A again. Here, as shown in FIG. 2, when transmission is performed from the transmission coil L1 of the read / write antenna A to the coil L3 of the data carrier 15, a signal having a phase difference of 90 ° from the original transmission signal is received. This phase differs depending on the direction of the coil of the data carrier.
Shall be late. This is shown as -90 ° in the figure. In the direction of this coil, the receiving coil L2 of the read / write antenna A extends from the coil L3 of the data carrier 15
, The phase is advanced by 90 ° (+ 90 °). The amplitude, that is, the reverberation level varies depending on the signal transmitted from the data carrier 16.

FIG. 3 illustrates this as a waveform diagram. Although FIG. 3 shows only the phase change with the waveform level kept constant, the waveform level actually changes greatly. FIG. 3A shows an oscillation signal of the oscillation circuit 14, which is a signal having a frequency fc added to each section as a carrier signal. FIG. 3 (b) shows a signal waveform transmitted from the transmission coil L1 of the read / write antenna A, and FIG. 3 (e) shows a signal transmitted from the read / write antenna B. In this figure, the carrier intermittent timings of the antennas A and B are matched, but this is not always the case. FIG. 3C shows a signal waveform received by the data carrier 15.
In this case, as described above, 90 ° with respect to the carrier signal
Has occurred.

FIG. 3D shows a signal received by the receiving coil L2 of the read / write antenna A. In the period T1, since the signal from the transmission coil L1 is directly received, the signal is delayed by 90 ° from the carrier signal like the signal received by the coil L3 of the data carrier 15. In the period T2 shown in FIG. 3D, when the oscillation of the transmission coil L1 stops, the reverberation signal from the data carrier 15 is received. Since this signal has a phase difference of 90 ° from the reverberation in FIG. 3C, the signal shown in FIG. 3D is received. The signal c received by the receiving coil L2 of the read / write antenna A during the period T2 is represented by the following equation. c = Ar ₃ (t) cos ωtr ₃ (t): response signal of data carrier

If the signal transmitted from the other read / write antenna B is, for example, as shown in FIG. 3 (e), this signal causes mutual interference with the signal received by the receiving coil L2 of the read / write antenna A. As shown in FIG. 3F, the received signal has a phase shifted by 90 ° from the signal shown in FIG. 3E. That is, when the reverberation signal from the data carrier 15 is received by the receiving coil L2, the phase is the same (or 180 ° out of phase) with the original carrier signal, whereas the mutual interference received from another read / write antenna is The wave has a phase difference of 90 ° with respect to the carrier signal. Therefore, the received signal R (t) received by the receiving coil L2 of the read / write antenna A is represented by the following equation including the leakage of the transmission signal from the read / write antenna B. R (t) = Ar ₃ (t) cos ωt + B ′ r ₂ (t) sin ωt B ′: Amplitude level of the read / write antenna B signal received by the receiving coil L2

Now, the ID controller 1 in the present embodiment.
2 and 13, the carrier signal fc from the oscillation circuit 14
And the signal thus obtained by the receiving coil L2 is synchronously detected to demodulate the original signal. That is, FIG.
, The signal from the receiving coil L2 is
8 given. An amplifier 18a is provided in the synchronous detection circuit 18.
And its output is provided to the multiplier 18b.
The multiplier 18b outputs the amplified output and the carrier signal (cos ω
t) to obtain a synchronous detection output x (t).
The output x (t) after synchronous detection is expressed by the following equation.

(Equation 1) Here, the signal Ar from the data carrier 15 is removed by removing the high-frequency components cos 2ωt and sin 2ωt of the output x (t) of the multiplier 18b by the low-pass filter 18c.
₃ (t) is obtained. This indicates that only the response signal r ₃ (t) from the data carrier 15 can be extracted regardless of the interference from the read / write antenna B.

FIG. 4 is a block diagram showing a detailed configuration of an identification system based on the principle of the present invention. In the figure, a transmission signal TXD from the host computer 11 is supplied to an oscillation control circuit 22 via an encoding circuit 21. The encoding circuit 21 performs Manchester encoding of the transmission signal TXD and transmits it to the data carrier. Oscillation control circuit 2
2 is supplied with a carrier signal having a frequency fc from the oscillation circuit 14 shown in FIG. The oscillation control circuit 22 is, for example, H
The carrier signal fc is intermittently transmitted at a duty ratio of 7: 3 at the time of transmission of the level, at a duty ratio of 3: 7 at the time of transmission of the L level, and at a duty ratio of 5: 5 at the time of reception. L1. Here, the encoding circuit 21 and the oscillation control circuit 22 are examples of the transmission unit 17 shown in FIG.

The receiving coil L2 in the read / write antenna A forms a resonance circuit together with the capacitor C1.
The output is received by a receiving circuit 23 including an amplifier circuit. Note that the oscillation state signal of the oscillation control circuit 22 is also supplied to the receiving circuit 23 at the same time, and the amplified output is reduced while the transmission coil L1 is driven. The output of the receiving circuit 23 is supplied to the envelope detection circuit 25 of the envelope detection unit 24 and the changeover switch 26A. The envelope detection circuit 25 of the envelope detection unit 24 detects the envelope of the received signal.
The output is provided to a sample and hold circuit (S / H circuit) 27. The sample and hold circuit 27 holds the received signal at a predetermined timing after transmission, and its output is given to the comparator 28. Comparator 2
Reference numeral 8 denotes a circuit for converting a binary signal by discriminating the output of the sample and hold circuit 27 with a predetermined threshold value. The output is supplied to a switching circuit 26B and a detection method selection circuit 29. The detection method selection circuit 29 switches between envelope detection and synchronous detection. If the output of the envelope detection unit is sufficiently high, the detection mode is switched to envelope detection. If the output of the envelope detection unit 24 decreases, the synchronous detection unit is switched. 30 is switched to synchronous detection. The output of the detection method selection circuit 29 is supplied to the switching circuits 26A and 26B as a switching signal. The switching circuit 26A is turned on when the synchronous detection is selected, and the switching circuit 26B selectively selects the output of the synchronous detecting section 24 and the output of the synchronous detecting section 30.

The signal supplied through the switching circuit 26 is amplified by the amplifier 31 in the synchronous detector 30 and is input to the synchronous detector 32. As described above, the synchronous detection circuit 32 includes the multiplier and the low-pass filter and performs synchronous detection. The synchronous detection output is supplied to the sample and hold circuit 33. The reception timing signal is supplied to the sample hold circuit 33, and the input is held at that timing. The output is supplied to the comparator. The comparator 34 discriminates an input signal with a predetermined threshold value, and its output is connected to one input terminal of the switching circuit 26B. Switching circuit 26B
Selects one of the outputs of the envelope detection unit 24 and the synchronous detection unit 30 based on the output of the detection method selection circuit 29, and supplies the selected signal to the decoding circuit 35. Decoding circuit 3
5 decodes this signal to obtain the received data RXD
Is sent to the host computer 11 side. Here, the detection method selection circuit 29 and the changeover switch 26
A and 26B constitute switching means for switching to a synchronous detection unit when a detection signal cannot be obtained from the envelope detection unit.

In this embodiment, the encoding circuit 21 converts the transmission signal TXD into Manchester code, and the decoding circuit 35 converts the Manchester-coded signal into the original NRZ signal. . Similarly, the signal is transmitted as a Manchester code on the data carrier side. FIG. 5 is a block diagram showing an example of the detection method selection circuit 29 in such a case. In the figure, the detection method selection circuit 29 has a plurality of cascade-connected D-type flip-flops 41, 42 and 43, and the output of the comparator 28 is given to the D input terminal of the D-type flip-flop 41. A clock signal is applied to the clock input terminals of these flip-flops 41 to 43.
The bar output is provided to an AND circuit 44. AND circuit 4
Numeral 4 determines the logical product of the Q bar outputs of the flip-flops 41 to 43 to determine whether or not a signal is continuously supplied from the comparator 28.

Next, the operation of the detection method selection circuit 29 will be described with reference to FIG. FIG. 6A shows the output of the comparator 28, and this output is applied to the D input terminal of the D flip-flop 41 shown in FIG. FIG.
(B) is a clock signal input to each D-type flip-flop. Now is the time t ₁ after the output from the comparator 28 is continuously at L level. In the case of Manchester-encoded signals, the same code (H or L) will not be repeated three times if data transmission is performed normally. However, L continuously for three clocks shown in FIG.
If the level continues, the distance between the read / write antenna A and the data carrier 15 is wide, and no output is obtained from the envelope detector 24, so that it is determined that data transmission is not possible. Thus AND circuit 44 is synchronized detection wave switching signal as shown in FIG. 6 (c) are output at time t _2.
In this case, the output of the receiving circuit 23 is supplied to the synchronous detector 30 via the switching circuit 26, and at the same time, the switching circuit 26B is also switched to the output side of the comparator 34. Switching to the synchronous detection side is performed only when the reception level decreases in this way. This is because when the distance between the read / write antenna and the data carrier is too short, phase shift occurs due to the influence of the strong magnetic field, and the synchronous detection may not operate normally. In this embodiment, if the data carrier is close, it is considered that there is almost no influence of the mutual interference from other read / write antennas.Therefore, the envelope detection is performed, and if the data carrier is far away, the synchronous detection is selected to prevent the mutual interference. Can be.

[0022]

As described above in detail, according to the first aspect of the present invention, a read / write antenna of another identification system is installed near a specific read / write antenna. Even when a transmission signal from another read / write antenna is directly received by the reception coil of the read / write antenna, it is necessary to remove such mutual interference by performing synchronous detection and extract only a signal from the data carrier. Can be. Further, in each of the identification systems, data transmission with the corresponding data carrier can be performed at an arbitrary timing without depending on the time division processing, so that the effect of shortening the communication time can be obtained.

According to the second aspect of the present invention, when the data carrier is close to the write / read control unit, a malfunction may occur in the case of synchronous detection. Since the detection is switched to the detection, the effect that data transmission can be performed without malfunction is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an overall configuration of an identification system according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a main part of a read / write antenna and an ID controller of the identification system according to the embodiment.

FIG. 3 is a time chart showing waveforms at various parts in the embodiment.

FIG. 4 is a block diagram showing a detailed configuration of an ID controller according to one embodiment of the present invention.

FIG. 5 is a circuit diagram illustrating a configuration of a detection method selection circuit according to the present embodiment.

FIG. 6 is a time chart illustrating an operation of the detection method selection circuit according to the present embodiment.

FIG. 7 is a schematic diagram showing an example of a conventional identification system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Host computer 12, 13 ID controller 14 Oscillation circuit 15, 16 Data carrier 17 Transmission part 18 Synchronous detection circuit 18b Multiplier 18c Low-pass filter 21 Encoding circuit 22 Oscillation control circuit 23 Reception circuit 24 Envelope detection part 25 Envelope detection circuit 26A, 26B Changeover switches 27, 33 Sample hold circuits 28, 34 Comparators 29 Detection method selection circuit 30 Synchronous detection unit 32 Synchronous detection circuit 35 Decoding circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 5/00-5/02 G06K 17/00 G06K 19/00

Claims (2)

(57) [Claims] 1. An identification system comprising: a data carrier; and a write / read control unit for transmitting data to the data carrier and receiving transmitted data, wherein the write / read control unit comprises: A read / write antenna provided on a surface facing the data carrier and including a transmission coil for transmitting a signal to the data carrier and a reception coil for receiving reverberation vibration from the data carrier; and intermittently intermittently a carrier signal based on the transmission signal. A transmission unit that transmits a signal to a data carrier by driving a transmission coil of the read / write antenna; and a synchronous detection unit that synchronously detects a resonance signal obtained by a reception coil of the read / write antenna together with the carrier signal. And a receiving unit, wherein the write / read control unit includes a plurality of adjacent write / read units.
An identification system comprising a carrier signal source that supplies a common carrier signal to a read control unit. 2. The reception section, wherein: the envelope detection section performs envelope detection of reverberation vibration obtained in a reception coil of the read / write antenna, and determines a binary signal based on the level thereof; A synchronous detection unit that performs synchronous detection of a signal obtained in a reception coil with a carrier signal of a transmission unit, and a switching unit that switches to the synchronous detection unit when the reception level decreases and a detection signal cannot be obtained from the envelope detection unit. The identification system according to claim 1, comprising: