JP2006014281A - Reading device, data carrier system, and demodulation method of reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable secure data demodulation for a non-contact information memory medium even having a wide resonant frequencies. <P>SOLUTION: The reading device 10 for receiving and demodulating a radio signal transmitted from a non-contact information memory medium 20, includes antenna primary coil 11-1, antenna secondary coil 11-2 and detection coil 11a, each having a different coupling factor to an antenna 21 provided on the non-contact information memory medium 20; demodulation circuits 17a-17c connected to the antenna primary coil 11-1, the antenna secondary coil 11-2 and the detection coil 11a, respectively, for demodulating the radio signal; and an OR-circuit 18 for OR'ing the respective outputs from the demodulation circuits 17a-17c, so as to demodulate and output. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reader that receives and demodulates a radio signal transmitted from at least a non-contact information storage medium, a data carrier system, and a method for demodulating the reader.

  In recent years, data carrier systems capable of non-contact communication wirelessly from a non-contact information storage medium incorporating an IC have been actively introduced. For example, a traffic gate entrance / exit device or an entrance / exit room management device using an IC card with an IC built in the card, a logistics management device for managing an article by attaching a tag with an IC to an article, an IC with an IC built in a wristwatch There are data carrier systems using non-contact information storage media of various shapes such as an entrance / exit room management device using a wristband.

  FIG. 16 is a block diagram showing a schematic configuration of a conventional data carrier system. As shown in FIG. 16, the conventional data carrier system includes a reading device 110 and a non-contact information storage medium 20 having data to be read by the reading device 110. The reading device 110 amplifies a predetermined carrier signal generated by the carrier signal generation unit 115, for example, a 13.56 MHz carrier signal, by an amplifier 116, and a magnetic field via an antenna 111 which is a loop antenna formed on the printed board 111a. Output as.

  On the other hand, the non-contact information storage medium 20 includes an antenna 21 that is a loop antenna that detects a magnetic field output from the antenna 111 and a data processing IC 22. The resonance frequency of the antenna 21 is adjusted by a capacitor C20 connected in parallel. Here, when the non-contact information storage medium 20 is located within a range that causes sufficient electromagnetic induction to the antenna 111 on the reading device 110 side, power is supplied to the data processing IC 22 side via the antenna 21. The non-contact information storage medium 20 is supplied with power in this state, and the digital signal processing unit 23 turns on and off the switch SW in accordance with data corresponding to the read instruction, thereby modulating the received carrier signal. Then, the data is sent to the reading device 110 side via the antenna 21.

  The reading device 110 side receives the modulated radio signal, demodulates the data by the demodulation circuit 117, outputs it to the digital signal processing unit 113, and sends the result to the computer 114. The demodulating circuit 117 detects the radio signal received by the antenna 111 by the detecting circuit 117a, the amplifying circuit 117b amplifies the detected output, and the binarized circuit 117c digitalizes the digital data. It outputs to 113.

  In order to increase the radiation magnetic field, some antennas 111 are configured by a transformer-coupled primary coil and secondary coil as shown in FIG.

JP 2002-222400 A JP 2001-103101 A

  By the way, in the conventional data carrier system, the reader 110 may not be able to demodulate the radio signal amplitude-modulated by the non-contact information storage medium 20 side. Here, a case where the reading apparatus 110 cannot demodulate will be described. First, when the switch SW is turned on and off by the transmission signal shown in FIG. 18A, the carrier signal is modulated, and the antenna reception voltage shown in FIG. 18B is generated in the antenna 111 on the reader 110 side. The amplitude-modulated signal is detected and demodulated as binarized data by a demodulation circuit 117 as shown in FIG.

  Here, the resonance frequency on the non-contact information storage medium 20 side is set in the vicinity of the carrier frequency such as 13.56 MHz, but has a width due to manufacturing variations. Alternatively, in order to positively identify a plurality of non-contact information storage media 20, a resonance frequency may be set in the 15 to 17 MHz band (see Patent Document 1). In such a case, a null point that cannot recognize the modulated wave is generated.

  As shown in FIG. 19, the antenna 21 on the non-contact information storage medium 20 side and the antenna 111 on the reading device 110 side are arranged so that the loop surfaces face each other, and FIG. 20 and FIG. The relationship between the distance L between 21 and 111 and the signal voltage δV (= Va−Vb) is shown using the resonance frequency fc on the non-contact information storage medium 20 side as a parameter. FIG. 9 shows a case where the reading device 110 is set to be in the best reading state when the resonance frequency of the non-contact information storage medium 20 is 13.5 MHz. In this case, as shown in FIG. 20, when the resonance frequency on the non-contact information storage medium 20 side is 17 MHz, the signal voltage δV is positive and the modulation wave can be recognized. However, when the resonance frequency is 15 MHz, at a certain distance L. The signal voltage δV becomes zero, and a null point PP1 where the modulated wave cannot be recognized is generated. Similarly, FIG. 21 shows a case where the reading device 110 is set to be in the best reading state when the resonance frequency of the non-contact information storage medium 20 is 15 MHz. Also in this case, when the resonance frequency is 17 MHz, the signal voltage δV is positive and the modulation wave can be recognized. However, when the resonance frequency is 13.5 MHz, the signal voltage δV becomes zero at a certain distance L and the modulation wave cannot be recognized. A null point PP2 is generated. That is, the reading device 110 set to a certain resonance frequency generates a null point for the non-contact information storage medium 20 having a resonance frequency other than the set resonance frequency, and cannot demodulate and demodulate the modulated wave. It may not be possible. Accordingly, there has been a demand for the appearance of a reading device 110 that does not form a null point for the non-contact information storage medium 20 having a wide range of resonance frequencies.

  In order to solve this problem, there is one that corrects the frequency characteristics of the received signal from the non-contact information storage medium 20 (see Patent Document 2). FIG. 22A shows the frequency characteristics of the received signal when a null point is generated. As shown in FIG. 22 (b), the correction according to Patent Document 2 is performed by increasing the level of the upper side band of the carrier frequency including the modulated data component and decreasing the level of the lower side band. Even if a null point is generated, it can be demodulated by subsequent correction processing.

  However, when the distance is different from the state shown in FIG. 22, the frequency characteristics of the received signal shown in FIG. In this case, as described above, when correction processing is performed to increase the level of the upper sideband and decrease the level of the lower sideband, the frequency characteristics of the received signal shown in FIG. There are cases where the sideband levels are the same and cannot be demodulated. That is, even if the above-described correction processing is performed, there is a problem that a null point is generated again for another resonance frequency at a position where the distance L is different, and demodulation is not possible.

  The present invention has been made in view of the above, and provides a reader, a data carrier system, and a reader demodulation method capable of reliably demodulating data even with respect to a non-contact information storage medium having a wide range of resonance frequencies. The purpose is to provide.

  In order to solve the above-described problems and achieve the object, a reading apparatus according to claim 1 is a reading apparatus that receives and demodulates a radio signal transmitted from a non-contact information storage medium. ORed with a plurality of antennas having different coupling coefficients with respect to the antenna, a plurality of demodulation circuits connected to the plurality of antennas and demodulating the radio signals received by the antennas, and an output from each demodulation circuit And an OR processing circuit for demodulating and outputting.

  According to a second aspect of the present invention, in the above invention, the demodulating means having the plurality of demodulating circuits adds, subtracts, or adds all or part of the signals input from the plurality of antennas. An arithmetic circuit for performing addition / subtraction processing is provided.

  According to a third aspect of the present invention, in the above invention, in the above invention, the arithmetic circuit performs an addition process and a subtraction process so as not to form a null point in the distance dependency of the signal voltage input from the antenna with the resonance frequency as a parameter. Alternatively, addition / subtraction processing is performed.

  According to a fourth aspect of the present invention, in the above invention, the arithmetic circuit performs an addition process so that the absolute value of the signal voltage in the distance dependency of the signal voltage input from the antenna with the resonance frequency as a parameter becomes high. , Subtraction processing or addition / subtraction processing is performed.

  According to a fifth aspect of the present invention, in the above invention, the demodulating means having the plurality of demodulation circuits includes a detection circuit, an amplification circuit for amplifying a signal detected by the detection circuit, and the amplification circuit. And the arithmetic circuit is provided in a stage preceding the binarization circuit.

  According to a sixth aspect of the present invention, in the above invention, the demodulating means having the plurality of demodulation circuits includes a detection circuit, an amplification circuit that amplifies the signal detected by the detection circuit, and the amplification circuit. And the arithmetic circuit is provided in a preceding stage of the amplifier circuit.

  According to a seventh aspect of the present invention, in the above invention, the demodulating means having the plurality of demodulation circuits includes a detection circuit, an amplification circuit for amplifying a signal detected by the detection circuit, and the amplification circuit. And the arithmetic circuit is provided in the preceding stage of the detection circuit.

  According to an eighth aspect of the present invention, in the above invention, the arithmetic circuit performs a subtraction process, an addition process, or an addition / subtraction process by sharing signals input from the plurality of antennas. .

  According to a ninth aspect of the present invention, in the above invention, at least one of the plurality of antennas is an antenna that is transformer-coupled with another antenna.

  According to a tenth aspect of the present invention, in the above invention, at least one of the plurality of antennas is a transmission / reception antenna.

  According to an eleventh aspect of the present invention, in the above invention, at least one of the plurality of antennas is a reception-dedicated antenna.

  According to a twelfth aspect of the present invention, in the above invention, the resonance frequencies of the plurality of antennas are different resonance frequencies in the vicinity including the resonance frequency of the antenna included in the non-contact information storage medium. And

  A data carrier system according to claim 13 is a non-contact information storage medium and a reading device according to any one of claims 1 to 12, which receives and demodulates a radio signal from the non-contact information storage medium. And.

  The data carrier system according to claim 14 is characterized in that, in the above invention, the non-contact information storage medium modulates a carrier signal received from the reader and transmits data to the reader. And

  The reader demodulating method according to claim 15 is a demodulating method for a reader which receives and demodulates a radio signal transmitted from a non-contact information storage medium, and is coupled to an antenna provided in the non-contact information storage medium. A plurality of demodulation circuits respectively connected to a plurality of antennas having different coefficients; a demodulation step for demodulating the radio signal received by each antenna; an OR processing step for performing an OR process on an output from each demodulation circuit and a demodulating output; , Including.

  According to a sixteenth aspect of the present invention, in the demodulating method of the reading apparatus, in the above invention, the demodulating step performs addition processing, subtraction processing, or addition / subtraction processing on all or part of signals input from the plurality of antennas. It includes an operation step.

  In the reader, the data carrier system, and the demodulation method of the reader according to the present invention, each antenna receives a plurality of demodulation circuits respectively connected to a plurality of antennas having different coupling coefficients for the antenna provided in the non-contact information storage medium. Since the OR processing circuit OR-demodulates and outputs the output from each demodulation circuit, the data is reliably demodulated even for non-contact information storage media with a wide range of resonance frequencies. There is an effect that can be done.

  In the reader, the data carrier system, and the demodulation method of the reader according to the present invention, the arithmetic circuit of the demodulator having the plurality of demodulator circuits may receive all or part of the signals input from the plurality of antennas. Perform addition processing, subtraction processing, or addition / subtraction processing so that a null point is not formed in the distance dependence of the signal voltage input from the antenna, and the absolute value of the signal voltage is increased and input to the OR processing circuit. As a result, the demodulation process can be performed more reliably.

  Hereinafter, a reader, a data carrier system, and a demodulation method of the reader which are the best mode for carrying out the present invention will be described.

(Embodiment 1)
First, a data carrier system including the reading apparatus according to the first embodiment will be described. FIG. 1 is a schematic diagram showing the configuration of the data carrier system according to the first embodiment of the present invention. As shown in FIG. 1, this data carrier system has a reader 10 and a non-contact information storage medium 20, and each communicates in a non-contact manner.

  The reading apparatus 10 mainly includes an antenna system 11, a signal processing circuit 12 that performs analog processing, a digital signal processing unit 13, and a computer 14. The antenna system 11 corresponds to the antenna 111 shown in FIG. 16, and includes an antenna primary coil 11-1, an antenna secondary coil 11-2, and a detection coil 11a. The antenna primary coil 11-1 and the antenna secondary coil 11-2 are loop antennas that are transformer-coupled to each other as shown in FIG. 17, are physically separated from each other, and are antennas for both transmission and reception. On the other hand, the detection coil 11a is a reception-only antenna.

  The signal processing circuit 12 includes a carrier signal generator 15 and an amplifier 16. The amplifier amplifies a predetermined carrier signal generated by the carrier signal generator 15 and sends the amplified carrier signal to the antenna primary coil 11-1. The carrier signal is transmitted as a radio signal via the secondary coil 11-1 and the antenna secondary coil 11-2 that is transformer-coupled to the secondary coil 11-1. The signal processing circuit 12 further includes a demodulator 17, and the demodulator 17 includes three demodulator circuits 17 a to 17 c and an OR circuit 18.

  The demodulation circuits 17a to 17c are connected to the antenna secondary coil 11-2, the detection coil 11a, and the antenna primary coil 11-1, respectively, and demodulate the detected signals. The OR circuit 18 ORs the outputs from the demodulating circuits 17a to 17c and outputs the result to the digital signal processing unit 13 as a final demodulated output.

  On the other hand, the non-contact information storage medium 20 performs the same configuration and operation as the non-contact information storage medium 20 shown in FIG. That is, the carrier signal received by the antenna 21 is accumulated by a rectifier circuit including a diode D2 and a capacitor C2, and the received carrier signal is modulated by turning on and off the switch SW realized by an FET or the like. Output via. The degree of modulation for this carrier signal can be adjusted by setting the value of the resistor R2.

  Here, the antenna primary coil 11-1, the antenna secondary coil 11-2, and the detection coil 11a are set to have different coupling coefficients for the antenna 21 of the non-contact information storage medium 20. 2 and 3 show the distance L dependence of the signal voltage δV detected by the reading device 10, FIG. 2 shows the case where the resonance frequency of the non-contact information storage medium 20 is 13.5 MHz, and FIG. This is when the resonance frequency of the information storage medium 20 is 15 MHz. In FIG. 2 and FIG. 3, it is not possible to demodulate the reading device 10 regardless of the resonance frequency of the non-contact information storage medium 20.

  For example, in FIG. 2, the characteristic curve LL2 of the antenna secondary coil 11-2 generates a null point P1, but the characteristic curve LL1 of the other antenna primary coil 11-1 and the characteristic curve LL3 of the detection coil 11a are the same. A null point is not generated when the distance is L, and the signal voltage δV can be detected, and the OR circuit 18 performs an OR process on each demodulation result of the signal voltage δV of the antenna primary coil 11-1 and the detection coil 11a. Therefore, demodulation can be performed reliably. Also, when the null point P2 is generated in the detection coil 11a, the signal voltage δV of the antenna primary coil 11-1 and the antenna secondary coil 11-2 is not zero, so that demodulation is performed reliably by performing OR processing. Can do.

  Similarly, in FIG. 3, null points P4, P5, and P6 are generated in the antenna primary coil 11-1, the antenna secondary coil 11-2, and the detection coil 11a, respectively. Since the signal voltage δV does not become zero, it is possible to reliably perform demodulation by performing OR processing.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. In the first embodiment described above, the demodulation circuits 17a and 17c demodulate the reception signals received by both the antenna primary coil 11-1 and the antenna secondary coil 11-2 that function as transmission / reception antennas. In the second embodiment, the received signal is demodulated only by the reception-dedicated antenna.

  FIG. 4 is a schematic diagram showing the main configuration of the reading apparatus according to the second embodiment of the present invention. As shown in FIG. 4, the reader is further connected to three reception-dedicated detection coils 11a to 11c by adding detection coils 11b and 11c to the configuration of the reader 10 shown in the first embodiment. Demodulating circuits 37a to 37c are provided. The demodulating circuits 37a to 37c have the same configuration as the demodulating circuits 17a to 17c, and similarly to the demodulating circuit 117, include a detecting circuit 117a, an amplifying circuit 117b, and a binarizing circuit 117c. Therefore, both the antenna primary coil 11-1 and the antenna secondary coil 11-2 function as a transmission-dedicated antenna, and the demodulation circuit is not connected. Other configurations are the same as those of the first embodiment, and the same reference numerals are given to the same components.

  Here, the detection coils 11a to 11c have different coupling coefficients for the antenna 21 of the non-contact information storage medium 20 as in the first embodiment. For this reason, as in the first embodiment, a null point may occur at a certain distance L. However, since the signal voltage δV of another antenna does not become zero at this distance L, it is ensured by performing OR processing. Can be demodulated.

  Further, in the second embodiment, since the transmitting antenna and the receiving antenna are configured separately, a configuration such as a duplexer is not required, and power loss on the reading device side can be reduced.

  Note that each of the demodulation circuits 17a to 17c or the demodulation circuits 37a to 37c described above has a configuration of three demodulation circuits, but is not limited thereto, and two or four or more demodulation circuits may be provided. . In that case, the coupling coefficient of the coil to which each demodulation circuit is connected is made different.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. In the first and second embodiments, the demodulator 17 having the three demodulator circuits 17a to 17c or the demodulator 37 having the three demodulator circuits 37a to 37c is used. However, in the third embodiment, By using the subtracting means or the adding means, the demodulation process can be performed more reliably.

  FIG. 5 is a block diagram showing the configuration of the demodulator of the data carrier system according to the third embodiment of the present invention. As shown in FIG. 5, the demodulator 40 is a demodulator corresponding to the demodulator 17 shown in FIG. 1. The demodulator 40 includes a demodulator circuit 41 having the same configuration as each of the demodulator circuits 17a to 17c. , A demodulation circuit 44 having a subtracting unit 44 and an OR circuit 18.

  Similarly to the demodulation circuit 117 of FIG. 16, the demodulation circuit 41 includes a detection circuit 41a, an amplification circuit 41b, and a binarization circuit 41c that are sequentially connected, and realizes the function of the demodulation circuit 17c. On the other hand, the demodulation circuit 44 includes a detection circuit 42a that detects a signal from the antenna secondary coil 11-2, a detection circuit 43a that detects a signal from the detection coil 11a, and an amplification circuit 42b that amplifies the output of the detection circuit 42a. An amplifying circuit 43b for amplifying the output of the detection circuit 43b, a subtracting circuit 44 for subtracting the output of the amplifying circuit 43b from the output of the amplifying circuit 42b, and a binarizing circuit for converting the output of the subtracting circuit 44 into a digital value. 42.

  The subtraction circuit 44 subtracts the analog signal from the detection coil 11a from the analog signal from the antenna secondary coil 11-2, and outputs the subtraction result to the OR circuit 18 through the binarization circuit 42c. This subtracted output can have a distance dependency that does not form a null point.

  6 and 7 show the distance L dependence of the signal voltage δV detected by the reader 10, FIG. 6 shows the case where the resonance frequency of the non-contact information storage medium 20 is 13.5 MHz, and FIG. This is when the resonance frequency of the information storage medium 20 is 15 MHz. Here, the characteristic curve LL10 is obtained by subtracting the characteristic curve LL3 of the detection coil 11a from the characteristic curve LL2 of the antenna secondary coil 11-2, and corresponds to the signal voltage δV output from the subtraction circuit 44. In this case, since the null point is not formed in the characteristic curve LL3, the signal voltage δV can be read reliably. The characteristic curve LL20 shown in FIG. 7 is also output from the subtraction circuit 44, and no null point is formed in the signal voltage δV even when the resonance frequency is 15 MHz. As a result, for example, when the resonance frequency is 13.5 MHz, demodulation is performed by OR processing of the characteristic curve LL1 of the antenna primary coil 11-1 shown in FIG. 6 and the characteristic curve LL10 obtained from the subtraction circuit 44. In this case, since no null point is generated in any of the demodulation results input to the OR circuit 18, the output from the OR circuit 18 does not become null. Further, even when the resonance frequency is 15 MHz, by performing the subtraction process, the three null points on the characteristic curve become only one null point, and a highly reliable demodulation process becomes possible. That is, at least one of a plurality of demodulation results input to the OR circuit 18 has a distance dependency without a null point, thereby improving the certainty of the demodulation process.

  In particular, when there is a characteristic curve where a null point is formed, in the first and second embodiments, another characteristic curve is selectively output by the OR circuit 18, but the signal voltage at the null point of this other characteristic curve is If it is low, the signal voltage can be increased by the subtracting circuit 44 described above, so that the reliability of the demodulation process can be improved.

  FIG. 8 and FIG. 9 are diagrams showing a specific configuration of the subtraction circuit 44. The subtraction circuit 44 may be a circuit using the operational amplifier 51 as shown in FIG. 8, or may be a magnetic circuit shown in FIG. In the magnetic circuit shown in FIG. 9, a magnetic circuit is formed using the magnetic core 52, and the subtraction process is performed by reversing the winding direction of the coils 52a and 52b on the input side.

  In the demodulator 40 shown in FIG. 5, the subtraction circuit 44 is used. However, the present invention is not limited to this, and an addition circuit may be provided instead of the subtraction circuit 44. This is because a characteristic curve having no nulls or a characteristic curve having a large demodulated value as a whole can be obtained even by the addition process between the characteristic curves.

  10 and 11 are diagrams showing a specific configuration of the adder circuit. Similar to the subtraction circuit 44, the addition circuit may be a circuit using the operational amplifier 53 as shown in FIG. 10, or may be a magnetic circuit shown in FIG. In the magnetic circuit shown in FIG. 11, a magnetic circuit is formed using the magnetic core 52, and the addition processing is performed by setting the winding directions of the coils 52a and 52b on the input side to the same direction.

  Next, a modification of the third embodiment will be described. FIG. 12 is a circuit diagram showing a first modification of the demodulator of the data carrier system according to the third embodiment of the present invention. As shown in FIG. 12, in the demodulator 50, a subtracting circuit 54 is provided between the detecting circuits 42a and 43a and the amplifying circuit 42b.

  Also with the configuration of the demodulator 50, the same operational effects as the demodulator 40 shown in FIG. 5 can be obtained, and the number of amplifier circuits can be reduced by one, thereby simplifying the configuration.

  FIG. 13 is a circuit diagram showing a second modification of the demodulator of the data carrier system according to the third embodiment of the present invention. As shown in FIG. 13, the demodulating unit 60 includes a subtracting circuit 64 in the preceding stage of the demodulating circuit 61 having the same configuration as that of the demodulating circuit 41. In other words, since the subtraction circuit 64 is provided before the detection circuits 42a and 43a, one detection circuit can be reduced from the configuration of the demodulator 50, so that the configuration is further simplified.

  FIG. 14 is a circuit diagram showing a third modification of the demodulator of the data carrier system according to the third embodiment of the present invention. As shown in FIG. 14, the demodulator 70 further includes a subtractor 63 in the preceding stage of the demodulator 41 shown in FIG. 13, and the subtracter 63 receives the antenna 2 from the signal from the antenna primary coil 11-1. The signal from the next coil 11-2 is subtracted, and the subtraction result is demodulated by the demodulation circuit 41.

  In the third modification, since one subtracting circuit is added, a characteristic curve without a null point can be obtained, and thus the reliability of the demodulation process can be further improved. Here, in each characteristic curve, not only the null point, but also the subtraction process or the addition process can be performed so that the value of the signal voltage δV becomes large. From this point also, the certainty of the demodulation process can be improved. it can.

  In the above-described third embodiment and its modifications, all perform demodulation processing on signal inputs from the three antennas of the antenna primary coil 11-1, the antenna secondary coil 11-2, and the detection coil 11a. However, the present invention is not limited to this, and the reliability of the demodulation process can be improved by using the above-described subtraction circuit or addition circuit even during the demodulation process for the signal input from the two antennas.

  For example, FIG. 15 is a diagram showing a configuration of a demodulating unit in which a subtracting circuit is applied to signal inputs from two antennas. In this demodulating unit 80, the signal from the antenna primary coil 11-1 and the antenna 2 are shown. Demodulation processing is performed using the signal from the next coil 11-2. In this demodulator 80, two demodulator circuits 41 and 61 are provided, and a subtractor circuit 84 is provided in the preceding stage of the demodulator circuit 61. A signal from the antenna primary coil 11-1 is input to the demodulation circuit 41, and the demodulation circuit 41 performs demodulation processing on this signal and outputs it to the OR circuit 18. On the other hand, a signal from the antenna primary coil 11-1 and a signal from the antenna secondary coil 11-2 are input to the subtracting circuit 84, and the subtracting circuit receives the antenna from the signal of the antenna primary coil 11-1. The signal of the secondary coil 11-2 is subtracted, and the subtraction result is output to the demodulation circuit 61. The demodulation circuit 61 demodulates the input subtraction result and outputs it to the OR circuit 18. In this way, OR processing using a subtracting circuit or an adding circuit can be performed even with signal input from two antennas.

  In the third embodiment described above, the subtraction circuit or the addition circuit is provided. However, for example, when two or more subtraction circuits are provided as shown in FIG. 14, the subtraction circuit and the addition circuit are appropriately connected. You may make it comprise combining.

  In the third embodiment described above, the subtraction circuit or the addition circuit is applied to the first embodiment. However, the present invention is not limited to this and can be applied to the second embodiment. In this case, the demodulation unit described in Embodiment 3 may be applied to the demodulation unit 37.

  Note that the subtraction circuit or addition circuit described in the third embodiment described above performs subtraction processing or addition processing for two input signals, but is not limited thereto, and subtraction processing for three or more input signals. Alternatively, addition processing and further addition / subtraction processing may be performed.

  In the first to third embodiments described above, the reader (reader) 10 has been described. However, the reader / writer is not limited to this, and the reader / writer performs writing on the non-contact information storage medium 20. It may be. Further, the reader 10 has been described as being connected to the computer 14 and remotely controlled. However, the reader 10 is not limited to this, and may be a portable or portable reader.

It is a schematic diagram which shows the structure of the data carrier system concerning Embodiment 1 of this invention. It is a figure which shows the distance dependence of the signal voltage which each antenna of the reader shown in FIG. 1 receives when the resonant frequency of a non-contact information storage medium is set to 13.5 MHz. It is a figure which shows the distance dependence of the signal voltage which each antenna of the reader shown in FIG. 1 receives when the resonant frequency of a non-contact information storage medium is set to 15 MHz. It is a schematic diagram which shows the main structures of the reader concerning Embodiment 2 of this invention. It is a circuit diagram which shows the structure of the demodulation part of the data carrier system concerning Embodiment 3 of this invention. It is a figure which shows the distance dependence of the signal voltage whose resonance frequency in the case of performing a subtraction process is 13.5 MHz. It is a figure which shows the distance dependence of the signal voltage whose resonant frequency is 15 MHz at the time of performing a subtraction process. It is a circuit diagram which implement | achieved the subtraction circuit using the operational amplifier. It is a circuit diagram which implement | achieved the subtraction circuit using the magnetic circuit. It is the circuit diagram which realized the addition circuit using the operational amplifier. It is the circuit diagram which implement | achieved the addition circuit using the magnetic circuit. It is a circuit diagram which shows the structure of the demodulation part of the data carrier system concerning the 1st modification of Embodiment 3 of this invention. It is a circuit diagram which shows the structure of the demodulation part of the data carrier system concerning the 2nd modification of Embodiment 3 of this invention. It is a circuit diagram which shows the structure of the demodulation part of the data carrier system concerning the 3rd modification of Embodiment 3 of this invention. It is a circuit diagram which applied the subtraction circuit to two antenna inputs. It is a schematic diagram which shows the structure of the conventional data carrier system. It is a figure which shows the structure of the conventional antenna by which the transformer coupling was carried out. It is a figure which shows the transition of the signal sent to the reader from the non-contact information storage medium in the conventional data carrier system. It is a figure which shows the positional relationship of the antenna of a non-contact information storage medium, and the antenna of a reader. It is a figure which shows an example of the distance dependence of the signal voltage induced by the antenna by the side of a reader. It is a figure which shows an example of the distance dependence of the signal voltage induced by the antenna by the side of a reader. It is a spectrum figure which shows the state which corrects the receiving characteristic which enlarges the level of the upper side band wave which contains a data component, and makes the level of a lower side band wave small, and eliminates a null point. FIG. 12 is a spectrum diagram showing a case where a null point is generated even when the reception characteristic shown in FIG. 11 is corrected.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Reading apparatus 11 Antenna system 11a-11c Detection coil 11-1 Antenna primary coil 11-2 Antenna secondary coil 12 Signal processing circuit 13 Digital signal processing part 14 Computer 15 Carrier signal generation part 16 Amplifier 17, 37, 40, 50 , 60, 70, 80 Demodulator 17a-17c, 37a-37c, 41, 42, 45, 61 Demodulator 18 OR circuit 20 Non-contact information storage medium 21 Antenna 22 Data processing IC
23 Digital signal processing unit 41a, 42a, 43a Detection circuit 41b, 42b, 43c Amplification circuit 41c, 42c Binarization circuit 44, 54, 63, 64 Subtraction circuit 51, 53 Operational amplifier 52, 54 Magnetic core 52a, 52b, 54a , 54b Coil C1, C2, C20 Capacitor D2 Diode R2 Resistance SW Switch

Claims (16)

In a reader for receiving and demodulating a radio signal transmitted from a non-contact information storage medium,
A plurality of antennas having different coupling coefficients for the antenna provided in the non-contact information storage medium;
A plurality of demodulation circuits that are respectively connected to the plurality of antennas and demodulate the radio signals received by the antennas;
OR processing circuit that OR-processes the output from each demodulator circuit and outputs the demodulated signal,
A reading apparatus comprising:   The demodulating means having the plurality of demodulation circuits comprises an arithmetic circuit for performing addition processing, subtraction processing, or addition / subtraction processing on all or part of signals input from the plurality of antennas. The reading device according to 1.   The arithmetic circuit performs an addition process, a subtraction process, or an addition / subtraction process so as not to form a null point in the distance dependency of the signal voltage input from the antenna using the resonance frequency as a parameter. Reading device.   The arithmetic circuit performs an addition process, a subtraction process, or an addition / subtraction process so that an absolute value of a signal voltage in a distance dependency of a signal voltage input from an antenna is increased using a resonance frequency as a parameter. The reading device according to 2 or 3. The demodulation means having the plurality of demodulation circuits includes a detection circuit, an amplification circuit that amplifies the signal detected by the detection circuit, and a binarization circuit amplified by the amplification circuit,
The reading apparatus according to claim 2, wherein the arithmetic circuit is provided in a stage preceding the binarization circuit. The demodulation means having the plurality of demodulation circuits includes a detection circuit, an amplification circuit that amplifies the signal detected by the detection circuit, and a binarization circuit amplified by the amplification circuit,
The reading apparatus according to claim 2, wherein the arithmetic circuit is provided in a stage preceding the amplifier circuit. The demodulation means having the plurality of demodulation circuits includes a detection circuit, an amplification circuit that amplifies the signal detected by the detection circuit, and a binarization circuit amplified by the amplification circuit,
The reading apparatus according to claim 2, wherein the arithmetic circuit is provided in a stage preceding the detection circuit.   The reading device according to claim 2, wherein the arithmetic circuit performs subtraction processing, addition processing, or addition / subtraction processing by sharing signals input from the plurality of antennas.   The reading apparatus according to claim 1, wherein at least one of the plurality of antennas is an antenna that is transformer-coupled with another antenna.   The reading apparatus according to claim 1, wherein at least one of the plurality of antennas is a transmission / reception antenna.   The reading apparatus according to claim 1, wherein at least one of the plurality of antennas is a reception-only antenna.   The resonance frequency of the plurality of antennas is a different resonance frequency in the vicinity including the resonance frequency of the antenna included in the non-contact information storage medium. apparatus. A non-contact information storage medium;
The reader according to any one of claims 1 to 12, which receives and demodulates a radio signal from the non-contact information storage medium;
A data carrier system comprising:   14. The data carrier system according to claim 13, wherein the non-contact information storage medium modulates a carrier signal received from the reader and transmits data to the reader. In a demodulating method of a reading apparatus that receives and demodulates a radio signal transmitted from a non-contact information storage medium,
A demodulation step in which a plurality of demodulation circuits respectively connected to a plurality of antennas having different coupling coefficients for the antenna included in the non-contact information storage medium demodulates the radio signal received by each antenna;
OR processing step for ORing the output from each demodulating circuit and demodulating it,
A method for demodulating a reading apparatus.   16. The demodulation of a reading apparatus according to claim 15, wherein the demodulation step includes an operation step of performing addition processing, subtraction processing, or addition / subtraction processing on all or part of signals input from the plurality of antennas. Method.

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