JPH10294684A - Data transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize satisfactory data communication even in an environment where noise is discontinuous by receiving a signal from outside for a period when transmission is not executed, discriminating the presence or absence of noise through a noise level and transmitting data when noise is not detected. SOLUTION: When a reader/writer 1 receives a communication command from a host computer 12, a noise level detection means 2a discriminates the noise level through a reception part constituted of a reception antenna coil 8, an amplifier part 9, a detection part 10, an A/D converter 11. When the noise level is lower than a threshold, a data transmission control means 2b controls a transmission part constituted of a transmission pulse generation circuit 4, an amplifier part 6 and a transmission antenna coil 7 and issues a response request command to a data carrier. The data carrier controls reverberation in accordance with transmission data. A read/write control part 2 detects a reception signal from reverberation received through the reception part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission device used in a contactless identification system and the like, and more particularly to a data transmission device for preventing the influence of noise.

[0002]

2. Description of the Related Art Conventionally, in order to identify parts and products on an assembly and transportation line and to mechanize transportation and entrance / exit at a gate of a ski resort, an automatic ticket gate, etc., a system for identifying a product and a passing person is required. Becomes Therefore, as shown in Japanese Patent Application Laid-Open No. 1-151831, a memory unit (data carrier) having a memory for an object to be identified is provided, and necessary information is written in such a memory by external data transmission. An identification system has been proposed in which the information is read as needed.

[0003] Such a conventional non-contact identification system, etc.
In a data transmission device that transmits and receives data by wireless transmission, good communication cannot be performed when noise is present outside, and a state in which a communication distance is reduced or communication becomes impossible occurs. There are various types of external noises that hinder such communication. For example, there are impulsive noise having a shorter time width than the data communication time, and noise that constantly occurs in a certain environment. In addition, there is noise which occurs when another electronic device or the like operates for a certain period of time. The non-contact data transmission device has a disadvantage that communication may be affected by such noise.

[0004]

In such an environment where continuous noise can occur, normal data communication can be performed in a state where no noise is generated, but good communication is performed during a period in which noise is generated. Cannot be performed. Therefore, there is a disadvantage that the communication condition changes depending on the timing.

The present invention has been made in view of such a conventional problem, and has as its object to enable good data communication even in an environment where external noise is intermittent.

[0006]

According to a first aspect of the present invention, there is provided a transmitting section, a receiving section for receiving an external signal when the transmitting section is not transmitting, and transmitting a transmitting signal from the transmitting section. A noise level detecting means for judging the presence or absence of noise based on a noise level received by the receiving unit while the signal is not transmitted, and data transmission is performed by the transmitting unit and the receiving unit when the noise is not detected by the noise level detecting means. Data transmission control means.

[0007] The invention of claim 2 of the present application is characterized in that data transmission is started when noise is continuously detected for a predetermined time or more by the noise level detecting means.

[0008]

FIG. 1 is a block diagram showing a configuration of a reader / writer which is a data transmission device of an identification system according to an embodiment of the present invention. In this figure, a reader / writer 1 includes a read / write control unit 2, a clock generator 3, a transmission pulse generation circuit 4, a reception pulse generation circuit 5, an amplification unit 6, a transmission antenna coil 7, a reception antenna coil 8, an amplification unit 9, It has a detector 10 and an A / D converter 11. The clock generator 3 is a clock generator that generates a high frequency to be a carrier of a reader / writer. The transmission pulse generation circuit 4 outputs a transmission modulation signal by intermittently transmitting a clock signal based on transmission data, and the output is supplied to a transmission antenna coil 7 via an amplification unit 6. The transmission pulse generating circuit 4, the amplifying unit 6, and the transmitting antenna coil 7 constitute a transmitting unit. The reception pulse generation circuit 5, the reception antenna coil 8, the amplification unit 9, and the detection unit 10 amplify and detect the signal obtained by the reception antenna coil 8 based on the reception gate signal obtained from the reception pulse generation circuit 5. , A / D converter 11 performs A / D conversion on the basis of the sampling signal.
These are converted, and these constitute a receiving unit.
The read / write control unit 2 has a noise level detection unit 2a and a data transmission control unit 2b. The noise level detecting means 2a detects a noise level before data communication, and starts communication when the noise level is equal to or less than a predetermined value.
After a certain period of time while the noise level is high,
It starts communication. Data transmission control means 2b
Controls the transmission / reception unit to transmit commands and data to the data carrier, and also determines the level of the A / D converter 11 to receive a signal from the data carrier. The read / write control unit 2 is connected to an upper host computer 12.

On the other hand, the data carrier 20 has a resonance circuit 21 composed of a coil and a capacitor as shown in FIG. 2, and the resonance circuit 21 includes a power generation unit 22, a demodulation unit 23, a modulation unit 24, and a clock generation unit 25. Connected. The power generation unit 22 rectifies a signal obtained by the resonance circuit 21, converts the signal into a constant voltage, and supplies power to each unit. Resonant circuit 21
Is supplied to the demodulation unit 23, and the signal superimposed on the power is demodulated and supplied to the control unit 26. The control unit 26 receives a clock signal from the clock generation unit 25 and writes or reads data in or from the memory 27 based on the transmitted command or data. The signal read from the control unit 26 is provided to the coil of the resonance circuit 21 via the modulation unit 24. The modulation unit 24 modulates a signal and transmits the signal to the reader / writer via the coil of the resonance circuit 21. Here, the demodulation unit 23, the modulation unit 24, the clock generation unit 25, and the control unit 26 constitute a data transmission unit that demodulates an externally applied command and data and transmits data read from the memory.

Next, the operation of the reader / writer according to the present embodiment will be described with reference to the flowchart of FIG. 3 and the time chart of FIG. First, when a communication command is sent from the host computer 12 to the read / write control unit 2, the reader / writer 1 proceeds from step S1 to S2 to start a timer. Then, in step S3, a noise detection mode is entered. In step S4, the noise level obtained from the A / D converter 11 is acquired.
Then, in a step S5, it is determined whether or not the noise level is higher than a threshold. If the noise level is the threshold value or less lower as shown at time t ₀ in FIG. 4 (c), the step S
At step 6, a response request command is issued to the data carrier. Then, in step S7, it is determined whether or not there is a response from the data carrier. If there is no response, the process returns to step S2 to restart the timer, and the same processing is repeated. In this way, as shown in FIGS. 4A and 4B, when the noise level is low, a response request to the data carrier can be made while monitoring the noise level.

FIG. 4 shows a state where there is no data carrier in the communication area and the response request and the monitoring of the noise level are continued.
Noise level rises as shown in (c), when the time t ₁ exceeds a threshold value, identifies whether the timer value Twait less advanced from step S5 to step S8. If the timer value is within this range, the process returns to step S3 to detect the noise level. Thus, steps S3, S4, S5, S
8 is repeated until the noise level decreases. Timer time the noise level is reduced below Twait, if equal to or less than the threshold value to the time t _2, the issues a response request command to the data carrier as described above proceeds from step S5 to step S6. Step S if no response
2, the same processing is repeated, and if there is a response from the data carrier, the process proceeds to the routine S9 to proceed to the data carrier 20.
Enter the communication state with. In this state, noise monitoring is not performed as shown in FIG. 4B, and only communication with the data carrier 20 is performed.

FIG. 5 is a waveform diagram showing waveforms of various parts when transmitting a command or data to a data carrier. When transmitting data to the data carrier, the reception gate signal and the sampling signal are turned off as shown in FIG. %, 50%. This signal is amplified by the amplifying unit 6 and the signal shown in FIG. In this way, the signal shown in FIG. 5C is obtained in the receiving antenna coil 8, but the same signal is obtained in the resonance circuit 21 of the data carrier 20, so that data and commands can be transmitted to the data carrier 20. it can.

On the other hand, when a signal from the data carrier 20 is received, the transmission modulation signal is intermittently transmitted at a constant duty ratio at a constant period, in this case, a duty ratio of 50% as shown in FIG. I do. In this case, FIG.
As shown in (c), the intermittent carrier is transmitted from the transmitting antenna coil 7. Data carrier 2
0 controls the reverberation according to the transmission data.
The signal shown in (c) is obtained in the receiving antenna coil 8.
When the transmission output is stopped, the reception pulse generation circuit 5
As shown in (d), a reception gate signal for opening the gate is output. As shown in FIGS. 6E to 6G, the reverberation is amplified and detected while the reception gate signal is being obtained.
The reception signal is detected based on the level at the sampling timing immediately before the end of the reception gate signal.

When a new communication command is received at time t ₃ , a response request and noise detection are performed. And time t
_When the noise level increases to ₄ , similar processing is repeated in the noise level detection mode. Then, the loop of steps S4 to S5 and S8 is repeated to detect the noise level. If the noise continues in this state, the time t
_{At 5} , the timer value exceeds Twait. In this case, the process proceeds from step S8 to step S6 to transmit a response request command to the data carrier. As described above, when noise is continuously generated for a predetermined time or more, communication is started even in a state of poor quality in order to prevent communication from being stopped for a long time. In such a case, it is conceivable to perform a process of confirming the data transmitted to the data carrier or a process of retransmitting the transmission data when a transmission completion signal cannot be obtained.

Although the present embodiment shows an example in which the present invention is applied to a contactless identification system, the present invention can be applied to various data transmission apparatuses for transmitting data using a wireless transmission path.

In the present embodiment, when data is transmitted from the reader / writer to the data carrier, the carrier is intermittently transmitted from the reader / writer at a constant period and the duty ratio is changed, and the data is transmitted from the data carrier by controlling reverberation. However, it goes without saying that the data transmission apparatus according to the present invention can be configured using other communication methods such as ASK and FSK.

[0017]

As described above in detail, according to the present invention, since the noise level is monitored before data transmission, communication is started when the noise level is sufficiently reduced.
Therefore, it is effective against intermittent noise, and stable communication can be performed while noise does not occur. Claim 2
According to the invention, in the case of stationary noise, an effect is obtained that communication can be performed in a state corresponding to the environment.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a reader / writer of an identification system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a data carrier of the identification system according to the present embodiment.

FIG. 3 is a flowchart showing an operation of the reader / writer according to the embodiment.

FIG. 4 is a time chart showing changes in the operation mode and noise of the reader / writer.

FIG. 5 is a waveform chart showing waveforms of respective units when a command is transmitted from a reader / writer to a data carrier.

FIG. 6 is a waveform chart showing waveforms of respective units when receiving a signal from a data carrier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reader / writer 2 Read / write control part 2a Noise level detection means 2b Data transmission control means 3 Clock generator 4 Transmission pulse generation circuit 5 Reception pulse generation circuit 6,9 Amplification part 7 Transmission antenna coil 8 Reception antenna coil 10 Detection part Reference Signs List 11 A / D converter 12 Host computer 20 Data carrier 22 Power generation unit 23 Demodulation unit 25 Clock generation unit 26 Control unit 27 Memory

Claims (2)

[Claims] A transmitting unit, a receiving unit that receives an external signal when the transmitting unit is not transmitting, and a noise that is received by the receiving unit while a transmitting signal is not transmitted from the transmitting unit. Noise level detection means for determining the presence or absence of noise based on a level; and data transmission control means for performing data transmission by the transmission unit and the reception unit when the noise is not detected by the noise level detection means. Data transmission device. 2. The data transmission apparatus according to claim 1, wherein data transmission is started when noise is continuously detected for a predetermined time or more by said noise level detection means.