JPH07296127A - Data carrier system - Google Patents

Abstract

PURPOSE:To eliminate necessity to connect access devices through a cable by suppressing interference to be applied mutually between the adjacent access devices to a minimum even when the plural access devices are installed together. CONSTITUTION:The influence of modulation to be applied to the carrier wave of an antenna 5 at the access device appears on a receiver 6 at the other access device. However, the transmission modulation on the access device side is a simple amplitude modulation, the influence is erased at the step of an output signal from a received signal component extracting circuit 9 inside the access device to be affected, and no fault is generated in the demodulation of received data at a data demodulating circuit 12. The received signal component extracting circuit 9 is functioned to remove a frequency component excepting for the frequency band of a frequency signal for transmission modulation on the side of a data carrier, and a signal component caused by the modulation of the carrier wave accompanying the transmission from the other access device is also removed before it is inputted to a data demodulating circuit 13. Therefore, the data demodulated result of the data demodulating circuit 12 is not affected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data carrier having a non-volatile semiconductor memory such as EEP-ROM or F-RAM as a data storage means, and for accessing the data carrier. The present invention relates to a data carrier system including an access device.

[0002]

2. Description of the Related Art In recent years, so-called remote-type data carriers, which have a relatively large accessible distance, have been increasingly applied. As a state-of-the-art technique relating to these, data carriers and access devices have been developed. Two-way communication between each other and battery-less data carriers are rapidly advancing. That is, the initial data carrier had a function of unilaterally transmitting fixed data to the access device, whereas the latest data carrier has a function of transmitting data from the access device. The so-called two-way communication type, which has a function of rewriting the stored data in its own storage circuit in response to the transmission of the command and the data, has become popular. In addition, in operation on the data carrier side,
A so-called batteryless type and two-way communication type data carrier, which is configured to supply required electric power from the access device side by utilizing electromagnetic inductive coupling, is already being generalized.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention
Two-way communication type data carrier using data carrier
In the system, in order to supply electric power to the data carrier side, a strong carrier wave is radiated as an electromagnetic field from the access device side, and bidirectional data exchange is performed therein. Therefore, it is very difficult for the access device side to receive the weak transmission data component generally returned from the data carrier side. In particular, when a plurality of access devices are installed side by side, a strong modulation signal is generated along with the modulation of the carrier wave when data is transmitted from each access device side to the data carrier side. In order to jump into other access devices in the vicinity, in these other access devices in the vicinity, reception of data sent from the data carrier in its own access area is disturbed, The risk of reception malfunction is extremely high. In the conventional data carrier system, in order to solve this problem, some transmission is performed between adjacent access devices so that data transmission from one access device can be transmitted to another access device. Attempts have been made to avoid or reduce interference with the device. However, in the prior art, it is necessary to connect a plurality of access devices with a cable for the above-mentioned synchronization, which is a constraint condition for the installation of the devices, and further, even if the synchronization is performed, the access devices are adjacent to each other. Mutual interference between access devices is still severe and communication failure occurs,
There were some drawbacks.

An object of the present invention is to improve the above-mentioned drawbacks of the prior art and to minimize the interference between adjacent access devices even when a plurality of access devices are provided side by side. To realize a carrier system.

[0005]

On the access device side, an antenna for radiating a predetermined carrier wave, a modulating means for modulating the carrier wave in accordance with serial transmission data at the time of data transmission, and data. Reception demodulation means for demodulating the reception data by receiving the transmission signal returned from the carrier side,
The data carrier side rectifies the antenna coil that receives the carrier wave and the carrier wave that is received through the antenna coil to generate a DC power supply that is power for driving the data carrier itself. Rectifying means, clock signal generating means for generating a clock signal having the same frequency as the carrier frequency based on the received carrier wave, and demodulating the serial transmission data from the access device by receiving the received carrier wave. In a two-way communication type data carrier system comprising reception demodulation means for transmitting and transmission modulation means for returning data to the access device, in order to achieve the above object, The present invention has the following configurations. That is, the transmission modulation means on the data carrier side divides the clock signal to form a modulation frequency signal, the content of the serial transmission data to be transmitted to the access device, and the modulation. Switching means for changing the AC impedance of the antenna coil based on the frequency signal for use,
And the receiving and demodulating means on the side of the access device is based on an envelope component corresponding to the modulation frequency signal in the reception signal of the reception device and the reception signal of the reception wave of the carrier wave, It comprises a received signal component extracting means for extracting the AC component of the envelope component and a data demodulating means for receiving the output from the received signal component extracting means and demodulating the received data.

[0006]

The received signal taken in by the receiver on the access device side is a signal having the frequency of the carrier wave itself, but its envelope has a shape corresponding to the frequency signal for transmission modulation on the data carrier side. have. Here, the reception signal component extraction means extracts a signal corresponding to the AC component of the envelope as a reception signal component, and further the data demodulation means demodulates the reception data based on the reception signal component. .

[0007]

1 to 5 show a data carrier system according to a first embodiment of the present invention, and FIG. 1 is a circuit diagram showing a configuration of an access device thereof. In the circuit shown in FIG. 1, ± 15 V is applied to the reference potential (GND).
A power supply with a positive or negative voltage of a certain degree is used. Oscillation circuit 1
The output signal of is transmitted through the transmission modulation circuit 2 as an original signal of a carrier wave to be sent to the data carrier side described later.
It is input to the antenna drive circuit 4, and drives the antenna 5 by series resonance. Sending of instructions and data
The transmission signal TA is input to the modulation circuit 2 from the data processing control circuit 3 that controls reception, and the carrier radiated from the antenna during serial data transmission from the access device side. Is amplitude-modulated according to the data content of the transmission signal TA. Transmission / reception of serial data between the access device side and the data carrier side is performed in an asynchronous manner in any direction, and the carrier wave radiated from the antenna 5 is transmitted. In the state where the signal TA is the data "1" (including the idling state in which the data is not transmitted from the access device side), it is in the non-modulation state, and the transmission signal TA is the data "1". In the state of "0", the modulation state is controlled in which the amplitude is suppressed. On the other hand, the antenna 5 is connected to the wave receiver 6 made of a resistor, and the current flowing through the antenna 5 is converted into a voltage here. That is, the wave receiver 6 is provided as a receiving means for receiving a reply from the data carrier side, and depending on the content of the transmission data from the data carrier side,
It has a function of converting a current change generated in the antenna 5 into a voltage change. The reception signal at the wave receiver 6 is input to a reception signal component extraction circuit 9 including a bandpass filter circuit (hereinafter referred to as BPF) 10 and an amplification circuit 11 via an amplification circuit 7 and an absolute value circuit 8 and received there. The envelope component corresponding to the modulation frequency signal in the signal is extracted as an AC signal. That is, the BPF 10 first erases the frequency component of the carrier itself, extracts the envelope component corresponding to the modulation frequency signal, and further the amplifier circuit 11 extracts and amplifies the AC component. The output signal of the amplifier circuit 11 is input to a data demodulation circuit 12 including an absolute value circuit 13, a diode detection circuit 14 and a comparator circuit 15 to demodulate received data. That is, the output signal from the amplifier circuit 11 is output by the absolute value circuit 13 and the detection circuit 14.
After being converted into a detection signal RS similar to the reception data, the reception data is finally demodulated by the comparator circuit 15 provided as an amplifier circuit. As described above, the reception demodulation means on the side of the access device is composed of the wave receiver 6, the reception signal component extraction circuit 9, the data demodulation circuit 12, etc., and the comparator of the data demodulation circuit 12 is connected. Circuit 15
The received data RA output from the input terminal is input to the data processing control circuit 3.

FIG. 2 is a circuit diagram showing the configuration of the data carrier side of this embodiment. In this circuit system, the V _DD side is the reference potential (GND) and the antenna coil 21 for receiving the carrier wave radiated from the access device side.
Has one end connected to the reference potential. The antenna coil 21 constitutes a parallel resonance circuit together with the resonance capacitor C1, and the diode D1 and the capacitor C2 constitute a level shift circuit. The carrier wave received through the antenna coil 21 is level-shifted by the level shift circuit, and then rectified by the rectifier circuit 22 including the power supply capacitor C4 and the rectifying diode D2. V _S is generated. The DC power supply V _S is further input to the constant voltage circuit 23, where it is regulated to a constant voltage power supply V _SS having a predetermined voltage. Regarding the configuration in which the carrier wave received by the antenna coil 21 is once level-shifted and then rectified as described above, one end of the antenna coil 21 can be set to the reference potential level of the circuit system. It becomes easy to integrate the entire circuit system including the transmission modulation transistor 32 into an IC, and the rectification power supply V
_Since the voltage of _S can be increased, the communication distance can be extended, and the like.
On the other hand, the received carrier wave is also input to the clock signal generation circuit 24 including a linear amplifier circuit,
The clock signal generation circuit 24 generates a clock signal f _c having the same frequency as the carrier frequency based on the AC signal component of the received carrier. The clock signal is further input to the frequency dividing circuit 26 via the buffer circuit 25, where it is frequency-divided into a modulation frequency signal f _m and a system clock signal f _s which will be described later. That is, a reception demodulation circuit 27, a data processing control circuit 28 described later having a reception data processing function and a transmission data processing function, and a storage circuit 2.
The main circuit portion of the data carrier composed of 9 or the like is configured to operate by using the constant voltage power source V _SS as driving power and receiving the system clock signal f _s as necessary. . The Zener diode D3 connected in parallel to the power supply capacitor C4 is a DC power supply V
It is provided to suppress the voltage of _{s from} exceeding a certain level. That is, in order to increase the communicable distance of the data carrier, it is necessary to increase the carrier wave output from the antenna 5 on the access device side. As a result, the data carrier comes very close to the antenna 5. In this state, the amplitude of the carrier wave received on the data carrier side and the voltage of the DC power supply V _S which is the input of the constant voltage circuit 23 become very large. There is a risk of damage to the circuit on the carrier side. The Zener diode D3 is provided as voltage suppressing means for preventing overvoltage, and the Zener diode D3 is provided for the antenna coil 21 and the voltage suppressing Zener diode D3. The resistor R1 is inserted so as to establish a serial relationship. The received carrier wave is taken out as a reception signal RW for demodulating the reception data from between the antenna coil 21 and the resistor R1 and inputted to the reception demodulation circuit 27. The reception demodulation circuit 27 is composed of a diode detection circuit 27a and an amplification circuit 27b for receiving the detection signal RX generated by the detection circuit 27a and finally demodulating the reception data RD, The reception data RD output from the reception demodulation circuit 27 is input to the reception function unit of the data processing control circuit 28. The data processing control circuit 28 is a memory composed of a non-volatile semiconductor memory circuit such as an EEP-ROM or F-RAM based on a command or data received from the access device side via the reception demodulation circuit 27. The memory data is written to or read from the circuit 29, and the processing result, read data, and the like are output as transmission data TD to the access device side. The transmission data TD is input to the NAND circuit 31 via the inverter 30 together with the above-mentioned modulation frequency signal f _m , and the output of the NAND circuit 31 is provided as transmission modulation switching means. It is configured so that it is input to the gate side of the connected transistor 32. That is, when the serial data is transmitted from the data carrier side to the access device side, the transmission data TD is transmitted.
Is 0, the NAND circuit 31 is O
It is controlled to the FF state, and as a result, the transistor 3
2 is also controlled to the OFF state, and the parallel resonant circuit constituted by the antenna coil 21 and the capacitor C1 maintains the resonant state.

Here, the communication operation when transmitting data from the access device side to the data carrier side will be described. FIG. 3 is a waveform diagram showing the voltage waveform of the received signal AW of the antenna coil 21 on the data carrier side,
Although illustration is omitted, the current waveform of the antenna 5 on the access device side also has the same amplitude change as the received signal AW. That is, when the transmission signal TA from the data processing control circuit 3 is in the state of data "1" (the same is true in the non-transmission state), the current waveform of the antenna 5 is kept constant. Further, when the transmission signal TA is the data "0", the amplitude is simply reduced. As a result, the received signal AW on the data carrier side is also in a state in which the data is "0" as compared with the state in which the transmitted data from the access device side is "1". Then, the waveform is modulated so that its amplitude is small. On the other hand, FIG. 4 is a waveform diagram showing a received signal LW in which the level of the received signal AW is level-shifted by the level shift circuit so that the peak of the waveform becomes substantially the reference potential level, and FIG. The received signal R extracted between the antenna coil 21 and the resistor R1 for demodulation of
It is a wave form diagram which shows W. 4 and 5 are waveforms corresponding to a state in which the data carrier is very close to the antenna 5 on the access device side and the level of the received signal generated in the antenna coil 21 is very large. Is shown. That is, in such a state, a voltage suppressing Zener diode D3 for preventing the occurrence of overvoltage.
, The amplitude of the level-shifted received signal LW is the sum V _Z of the Zener voltage V _Z of the voltage suppressing Zener diode D3 and the voltage drop V _D in the power rectifying diode D2. It is clamped at a voltage equal to + V _D. As a result, even when the transmission data from the access device side is "0", and therefore the amplitude of the reception signal LW is V _Z even when the amplitude is modulated to be small.
If the situation exceeds + V _D , the received signal L
In W, as shown in FIG. 4, the change in the amplitude of the waveform between the non-modulation of the data "1" and the modulation of the data "0" disappears. Become. However, the reception signal RW input to the reception demodulation circuit 27 is shown in FIG. 5 because the influence of the change in the current flowing through the resistor R1 appears as a voltage change across the resistor R1 itself even in such a situation. As described above, it is possible to secure a sufficiently large amplitude difference between the time of non-modulation and the time of modulation, and the reception demodulation circuit 27 can demodulate the reception data reliably and easily. Here, the value of the resistor R1 is
Although it depends on the sensitivity of the receiving and demodulating circuit, 100Ω or more and 10KΩ or less are suitable. That is, in the case of 100Ω or less, the amplitude change that can be secured is small, so that it is necessary to increase the sensitivity of the reception demodulation circuit, which increases the risk of causing a malfunction by excessively reacting to disturbance noise. On the other hand, if it is 10 KΩ or more, when the transmission modulation transistor 32 is turned off, the voltage applied to the transistor 32 becomes excessive and there is a risk of damage. Although illustration is omitted, the amplitude of the received signal AW also decreases as the data carrier moves away from the antenna 5 on the access device side. As a result, the amplitude of the received signal LW at the time of modulation (when the data is “0”) also becomes smaller than V _Z + V _D , but accordingly, the received signal LW is also in the non-modulated state and the modulated state. The amplitude change between and becomes larger.

On the other hand, the reception signal RW is detected by the diode detection circuit 27a of the reception demodulation circuit 27, and the detection signal RX formed here is input to the amplification circuit 27b. The amplifier circuit 27b is a DC cut capacitor C5.
, The bias setting resistors R2 and R3, and the comparison reference voltage V
It is composed of _R forming resistors R4 and R5, a comparator circuit 27c and the like. The resistor R6 and the capacitor C
Reference numeral 6 constitutes a low-pass filter for eliminating the frequency component of the carrier from the detected signal RX to make the signal smooth. In the amplifier circuit 27, the detection signal R from the diode detection circuit 27a is set so that the distance between the antenna 5 on the access device side and the data carrier may change.
After being DC-cut by the capacitor C5, X is configured to be biased to a predetermined voltage level with a time constant of a certain value or more. That is, the comparator circuit 27c
The level of the input signal V _X on the − input side of the resistors R2 and R3 is
Is configured so that it is biased to a voltage lower than the comparison reference voltage V _R on the + input side by an appropriate level, and therefore there is no transmission from the access device side (the amplitude of the output carrier wave from the antenna 5 is amplitude). When the condition without modulation continues, the output signal of the comparator circuit 27c (that is, the reception data RD) is maintained at the data "1" level. When the state shifts from this state to the modulation state, the voltage level of the detection signal RX rises, and accordingly the input signal V
_{For X} levels even up to more than the comparison reference voltage V _R, the reception de - data RD is inverted to "0" level. When the state returns to the non-modulated state again, the level of the input signal V _X also decreases in accordance with the fall of the detection signal RX, and becomes lower than the comparison reference voltage V _R , and the reception data RD is also returned to the “1” level. By the way, FIG. 6 is a diagram showing a state of change in the envelope of the received signal RW when the distance between the antenna 5 on the access device side and the data carrier changes, and N1 and N2 are:
The non-modulation state and the modulation state when the data carrier approaches the antenna 5 on the access device side are shown respectively, and M1 and M2 show the non-modulation state and the modulation state when the data carrier moves away, respectively. Show. Further, FIG. 7 is a waveform diagram showing how the state of the detection signal RX changes when the received signal RW changes as shown in FIG. As described above, the amplitude of the modulated signal N2 and the voltage level of the detection signal RX when the data carrier is close to the antenna 5 on the access device side are the same as the amplitude and the detection signal of the unmodulated M1 when they are separated. Since the voltage level is higher than the RX voltage level, the received data cannot be demodulated by simply comparing the voltage level itself of the detection signal RX. However, if the amplifier circuit 27b of the present embodiment, in order the input signal V _X is biased to a suitable voltage level, the access device side of the antenna 5 and the de - when the distance between the data carrier are different in various But
It is possible to reliably demodulate the received data. However, in this case, the time constant formed by the capacitor C5 and the resistors R2 and R3 is the length of one unit of data transmitted from the antenna 5 on the access device side, in other words, the modulation state continues during communication. Maximum possible time width (for example, when transmitting in 8-bit 1 unit in asynchronous mode,
It is necessary to set the value larger than the time required to send one unit of 8 bits. That is, if the above time constant is set shorter than the length of the data of 1 unit, the comparator circuit 27c will eventually be provided when the modulation state continues for a length of the data of 1 unit. The voltage level on the − input side is biased to the same level as that at the time of non-modulation, so that demodulation of received data becomes impossible. On the other hand, even when the distance of the data carrier changes momentarily, when the distance changes relatively slowly as compared with the above time constant, for example, due to human movement, the input signal V _X is always generated. The received data is easily demodulated because the bias of 1 is continuously tracked to an appropriate level.

Next, the communication operation when transmitting (replying) from the data carrier side to the access device side will be described. On the side of the access device, once the transmission to the data carrier is completed, this time it waits for a reply from the data carrier side, but it tries to receive the reply from this data carrier side. In the state, of course, the output carrier wave from the antenna 5 is controlled in an unmodulated state. Here, when the transmission from the data carrier side is started and the transmission data TD from the data processing control circuit 28 is in the state of "0", the NAND circuit 31 is in the ON state, so that the modulation The switching action of the transistor 32 is triggered in response to the frequency signal f _m , which results in
A periodic change occurs in the AC impedance of the antenna coil 21 and the transmission modulation state is brought about by the transmission operation from the data carrier side. FIG. 8 is a waveform diagram showing a signal waveform in the antenna coil 21 in the transmission modulation state on the data carrier side. In this embodiment, the frequency dividing circuit 26
Since the frequency signal f _m for modulation output from is frequency-divided to ⅛ the frequency of the clock signal f _c having the same frequency as the carrier wave, in the above transmission modulation state,
The transistor 32 turns on and turns off every four cycles of the carrier wave.
The FF state is repeated. That is, in the section where the transistor 32 is in the ON state, the antenna coil 2
1 and the capacitor C1 are connected in parallel with the modulation capacitor C3, the original parallel resonance condition is destroyed and the AC impedance of the antenna coil 21 is reduced. Is high,
As a result, the signal waveform in the antenna coil 21 is
The amplitude is reduced as compared with the case of no modulation. Further, in the section where the transistor 32 returns to the OFF state, the parallel resonance state is restored, so that the amplitude of the signal waveform in the antenna coil 21 also returns to the original state. As a result, in the above-described transmission modulation state, the signal waveform in the antenna coil 21 alternates between the state in which the amplitude is small and the original state alternately every four cycles of the carrier wave, as shown in FIG. It will be. Note that the antenna coil 21 during the above modulation
Since the amplitude change that occurs in 1) requires a certain time width in comparison with the carrier wave period, a sufficient amplitude change occurs when the frequency of the modulation frequency signal f _m is too close to the original carrier wave frequency. As a result, the transmission capability to the access device side is also insufficient. Further, in order to surely and easily perform reception demodulation on the access device side, it is necessary to secure a certain number or more of the above-mentioned amplitude modulation alternating repetitions per bit length which is a data unit at the time of transmission. As a result, when the frequency of the modulation frequency signal f _m is too lower than the original carrier frequency, the bit length becomes large, which causes a drawback that communication required time becomes long. Considering these, the frequency of the modulation frequency signal f _m is preferably in the range of ⅛ to 1/16 of the original carrier frequency, and the data at the time of transmission from the data carrier to the access device side. The bit length of the data is 4 to 16 times the period of the modulation frequency signal f _m.
A double range is appropriate.

On the other hand, as a result of the transmission modulation operation on the data carrier side, the antenna 5 on the access device side is obtained.
A change also occurs in the waveform of the current flowing through. FIG. 9 is a waveform diagram showing a received waveform in the receiver 6, and a section affected by transmission modulation on the data carrier side (that is, transmission data TD from the data carrier side is “0”). In the period (in which the signal is in the area), a periodic amplitude change corresponding to the modulation frequency signal also appears in this received waveform. That is, the frequency component of the reception signal at this stage is the frequency component of the carrier wave itself, and the envelope has a shape corresponding to the modulation frequency signal, although it has a slight amplitude change. The received signal is amplified by the amplifier circuit 7 to an appropriate level if necessary, and then input to the absolute value circuit 8 to be full-wave rectified. FIG. 10 is a waveform diagram showing an output signal from the absolute value circuit 8. This output signal also corresponds to the modulation frequency signal in the section where the transmission modulation is performed on the data carrier side. A periodic amplitude change appears. According to the configuration in which full-wave rectification is performed by the absolute value circuit 8 as described above, the shape itself of the envelope P appearing corresponding to the modulation frequency signal is the amplification circuit 7 of the preceding stage.
Even if it is the same as the output from, the signal is substantially doubled in frequency, so a more precise signal can be obtained as the reception signal to be demodulated, and the reception demodulation in the subsequent stage also
It will be more reliable and easier.

The output signal from the absolute value circuit 8 is input to the BPF 10 of the reception signal component extraction circuit 9, where the envelope component corresponding to the modulation frequency signal is extracted, and then the amplification circuit 11. , Its AC component is extracted and amplified. FIG. 11 is a waveform diagram showing an output signal from the amplifier circuit 11. The received signal component extraction circuit 9 including the BPF 10 and the amplifier circuit 11 removes a frequency component of a carrier wave and an AC component based on the frequency signal for modulation. Is extracted and amplified. By the way, when a device or a person who may move has a data carrier, the distance of the data carrier to the antenna 5 on the access device side may change according to the movement. The influence of the change in the distance also appears as a change in the amplitude of the received signal in the wave receiver 6. However, in the reception signal component extraction circuit 9 described above, the BPF 10 extracts the signal in the band near the frequency of the modulation frequency signal, and the amplification circuit 11 extracts the AC component. Therefore, for a relatively slow signal change (that is, a low frequency signal component) due to the above distance change, that component is removed,
After all, the influence of the above-mentioned distance change, which is an obstacle to the demodulation of the reception data, is eliminated here.

The output signal of the amplifier circuit 11 is input to the absolute value circuit 13 of the data demodulation circuit 12. Figure 12
It is a wave form diagram which shows the output signal from the absolute value circuit 13, and the signal which has the positive / negative both polarities output from the amplifier circuit 11 is full-wave rectified here. FIG. 12 is a waveform diagram showing the output signal of the absolute value circuit 13. According to such a configuration, the signal to be demodulated has a signal density which is substantially doubled. Data demodulation can be performed more easily. The output signal from the absolute value circuit 13 is further demodulated as reception data RA by the diode detection circuit 14 and the comparator circuit 15.
FIG. 13 is a waveform diagram showing the detection signal R _s output from the detection circuit 14, and the output signal from the absolute value circuit 13 is waveform-shaped here. The detection signal R _s output from the detection circuit 14 is a signal substantially similar to the final reception data, and is further input to the comparator circuit 15 provided as an amplification circuit, where Demodulated as received data RA. FIG. 14 is a waveform diagram showing the reception data RA output from the comparator circuit 15. The comparator circuit 15 inverts the reception data RA to "0" level when the level of the detection signal R _s becomes lower than the comparison reference voltage V _r on the -input side,
On the contrary, when the level of the detected signal R _s returns to a level higher than the comparison reference voltage V _r on the minus input side, the reception data RA returns to "1" level.

Assuming that a plurality of access devices are installed side by side and data is transmitted from a certain access device to a data carrier, the antenna 5 of the access device is used for the transmission. The effect of the modulation applied to the emitted carrier will of course appear on the receiver 6 of the other access device. However, since the transmission modulation on the side of the access device is a simple amplitude modulation, the above influence is canceled at the stage of the output signal from the reception signal component extraction circuit 9 in the affected access device. In addition, there is no obstacle to the demodulation of the received data in the data demodulation circuit 13. That is, since the reception signal component extraction circuit 9 functions to eliminate frequency components other than the frequency band of the transmission modulation frequency signal on the data carrier side, the carrier wave associated with transmission from another access device is eliminated. The signal component due to the modulation is also removed before being input to the data demodulation circuit 13,
Normal reception data RA is obtained without affecting the data demodulation result in the data demodulation circuit 13.

In the above embodiment, the received signal from the wave receiver 6 is directly input to the amplifier circuit 7. However, the amplitude of the received signal is an envelope corresponding to the modulation frequency signal. If the amplitude of the line component is too large, a subtraction circuit removes a constant amplitude component substantially equivalent to the amplitude at the time of non-modulation from the received signal, so that It is also possible to increase the ratio of the modulation component of. Regarding the reception signal component extraction circuit 9, before inputting the reception signal to the BPF 10, the frequency signal component of the carrier is removed to some extent through the diode detection circuit, and then the BP is extracted.
It is also possible to configure to input to F10. In addition, amplifier circuits and voltage
With a follower circuit and various filter circuits,
It is also possible to support a function for receiving and demodulating. Further, in the above embodiment, the data demodulation circuit is composed of an analog circuit system, but the demodulation of the reception data by a simple digital circuit is also possible. For example, a counting circuit for counting the number of pulses of the AC signal corresponding to the component of the transmission modulation frequency signal is provided, and the reception data is received in accordance with the number of pulses within a predetermined time width related to the bit length of the reception data. It is also possible to demodulate the data. In that case, the data processing control circuit may control the start bit detection in the asynchronous reception and the periodic reset processing of the counting means for demodulating the subsequent bits. .

[0017]

As described above, in the present invention,
Since the receiver on the access device side is configured to receive the signal having the same frequency component as the carrier wave, the reception signal can be captured without difficulty, and then the data carrier side When it is subjected to the transmission modulation, the receiving signal component extracting means is configured to extract the AC component according to the modulation frequency signal, so that the transmission from the certain access device to the data carrier is performed. Even if this happens, it is possible to prevent a malfunction from occurring in reception at another access device provided side by side. That is, the reception signal component extraction means in the affected access device functions to cancel the influence of the transmission modulation by the other access device even in the above-mentioned situation, so that erroneous reception is not caused. Absent. Therefore, in the data carrier system according to the present invention, in order to reduce mutual interference between the access devices provided side by side, it is possible to eliminate the need to connect all the access devices with a synchronization cable. By interposing a synchronization cable as described above in the data carrier system according to the invention, it is possible to suppress communication interference between adjacent access devices to the maximum extent. Is.
Further, according to the present invention, it is possible to realize an access device that is less likely to cause a malfunction due to reception not only in the case of interference from another co-located access device but also against the influence of other noise sources. That is, for other general noise, the effect is removed by the reception signal component extraction means unless the noise is in the same frequency band as the transmission modulation frequency signal on the data carrier side. The occurrence of reception malfunction is suppressed.

Regarding the transmission modulation on the data carrier side, while performing the modulation using the frequency signal for modulation as in the case of the present invention, the access device side removes the carrier component from the beginning and only the signal component is obtained. , That is, a signal in which the waveform of the carrier frequency and the modulation frequency is synthesized (when the carrier frequency is F and the frequency of the modulation frequency signal is f, the sum of the two is F + f or the difference is F−f. (A signal with a frequency of 1) is directly extracted exclusively by a bandpass filter, but in that case, if the carrier frequency and the frequency of the frequency signal for modulation are close to each other, the modulation itself will occur. Since it occurs only at a very shallow level, the signal component required for data demodulation becomes too weak, and reception at the access device side is extremely weak. It becomes difficult. (However, this point also applies to the case of the present invention.) On the contrary, the frequency of the carrier frequency and the frequency signal for modulation are separated (that is, f is smaller than F).
Since the frequency (F + f or F−f) of the above waveform-synthesized signal is relatively close to the frequency (F) of the carrier wave, the frequency of the carrier wave is changed from the carrier wave by means of a bandpass filter or the like. Separation of signal components becomes very difficult, and in any case, reception demodulation suffers, and the communication distance becomes insufficient. On the other hand, in the configuration of the present invention, the signal itself of the carrier frequency F is first taken in and the envelope is extracted, so that even if the carrier frequency and the frequency signal for modulation are separated from each other. , It is easy to separate the signal components.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an access device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a structure of a data carrier according to an embodiment of the present invention.

FIG. 3 is a waveform diagram showing a received signal on the data carrier side in the embodiment of the present invention.

FIG. 4 is a waveform diagram showing a received signal after level shifting on the data carrier side in the embodiment of the present invention.

FIG. 5 is a waveform diagram showing a reception signal to be a reception demodulation target on the data carrier side in the embodiment of the present invention.

FIG. 6 is a waveform diagram showing an envelope curve of a received signal to be received and demodulated on the data carrier side in the embodiment of the present invention.

FIG. 7 is a waveform diagram showing a detection signal on the data carrier side in the embodiment of the present invention.

FIG. 8 is a waveform diagram showing a transmission signal on the data carrier side in the embodiment of the present invention.

FIG. 9 is a waveform diagram showing a received signal of the wave receiver on the access device side in the embodiment of the present invention.

FIG. 10 is a waveform chart showing a signal to be received and demodulated on the access device side in the embodiment of the present invention.

FIG. 11 is a waveform diagram showing an output signal from the received signal component extraction circuit on the access device side in the embodiment of the present invention.

FIG. 12 is a waveform diagram showing an output signal from an absolute value circuit which constitutes a data demodulation circuit on the access device side in the embodiment of the present invention.

FIG. 13 is a waveform diagram showing an output signal from the detection circuit which constitutes the data demodulation circuit on the access device side in the embodiment of the present invention.

FIG. 14 is a waveform diagram showing reception data on the access device side in the embodiment of the present invention.

[Explanation of symbols]

 5 Antenna 9 Received Signal Component Extraction Circuit 12 Data Demodulation Circuit 13 Absolute Value Circuit 14 Diode Detection Circuit 15 Comparator Circuit 21 Antenna Coil 22 Rectifier Circuit 24 Clock Signal Generation Circuit 26 Dividing Circuit 27 Reception Demodulation Circuit 30 Transmission modulation transistor

Claims (6)

[Claims] 1. A data carrier system comprising a data carrier having a non-volatile semiconductor memory as data storage means and an access device for accessing the data carrier. The device receives an antenna for radiating a predetermined carrier wave, a modulation means for modulating the carrier wave according to serial transmission data at the time of data transmission, and a transmission signal returned from the data carrier side. Receiving demodulation means for demodulating received data by means of an antenna coil for receiving the carrier wave, and rectifying the carrier wave received through the antenna coil. Rectifying means for generating a direct current power supply for driving the data carrier itself, and a clock signal having the same frequency as the carrier frequency based on the received carrier wave. Clock signal generating means for generating a signal, reception demodulating means for receiving the received carrier wave and demodulating serial transmission data from the access device, and for returning data to the access device. In a two-way communication type data carrier system comprising a transmission modulation means, the transmission modulation means on the data carrier side divides the clock signal to form a frequency signal for modulation. Means and switching means for changing the AC impedance of the antenna coil based on the content of the serial transmission data transmitted to the access device and the modulation frequency signal, and on the access device side. The receiving and demodulating means includes a wave receiver that takes in a received signal in the frequency band of the carrier wave, and an envelope curve corresponding to the modulating frequency signal in the received signal of the wave receiver. On the basis of the received signal component extraction means for extracting the AC component of the envelope component and the data demodulation means for receiving the output from the received signal component extraction means and demodulating the received data. Characteristic data carrier system. 2. On the access device side, the received signal component extracting means includes a filter circuit for extracting an envelope component corresponding to the modulation frequency signal in the received signal of the receiver. The data carrier system according to claim 1. 3. On the access device side, the data demodulation means includes an absolute value circuit for forming an absolute value signal of an output signal from the received signal component extraction means. Data carrier according to the first item of the range
system. 4. On the access device side, the modulation means comprises means for amplitude-modulating the carrier wave in accordance with transmission data to the data carrier side. The described data carrier system. 5. On the data carrier side, the frequency dividing means forms a modulation frequency signal having a frequency in the range of ⅛ to 1/16 of the frequency of the carrier wave. A data carrier system according to claim 1. 6. On the data carrier side, the bit length of the serial transmission data transmitted to the access device side is 4 to 1 times the cycle of the modulation frequency signal.
The data carrier system according to claim 4, wherein the length is set to be six times as long.