JP3518330B2 - Data communication method and receiving device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication method and a receiving device for communicating digital data.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram showing an example of a conventional receiver for receiving and demodulating an ASK-modulated signal. As shown in the figure, in the receiving device, the ASK modulated signal is received by the receiving unit 101, envelope detection is performed by the envelope detection unit 102, and the detection output is given to the comparison unit 103 and the reference level generation unit 104. The reference level generator 104 integrates the envelope detection output over a long time constant to obtain A
The intermediate value of the SK-modulated signal is generated as a reference level and the reference level is given to the comparison unit 103. The comparison unit 103 discriminates the envelope output based on the reference level thus obtained, demodulates the data signal, and outputs the demodulated data signal.

However, in such a conventional receiving apparatus, since the reference level is sequentially determined by the envelope detection output, as shown in FIGS. 9 (a) and 9 (c), a predetermined logical level " If "0" or "1" continues, the reference level changes, and it becomes impossible to set an appropriate reference level. Therefore, in the conventional ASK modulation method, encoding is performed. For example, as shown in FIGS. 9B and 9D, Manchester encoding is performed so that the logical "0" of the NRZ is "01" and the logical "1" is "10", and the "0" and The occurrence probability of "1" was the same. In this way, the reference level generator 104 can set an appropriate reference level, and the original signal can be accurately demodulated.

[0004]

However, when such a Manchester-coded signal is used, an accurate reference level can be obtained, but the amount of transmitted data is less than that of the original NRZ. There has been a problem that the data transmission speed is reduced to 1/2.

The present invention has been made in view of the above-mentioned conventional problems, and makes it possible to accurately demodulate a signal without Manchester encoding the data to be transmitted and without lowering the data transmission rate. The purpose is to

[0006]

According to a first aspect of the present invention, there is provided a data communication method for transmitting digital data, wherein a transmission device follows a level detection pattern in which logic 0's and 1's are alternately consecutive to each other. A signal modulated according to a column is transmitted, a receiving device receives the level detection pattern to calculate an average value of 0 level and 1 level , and the average value of each of the 0 level and 1 level is calculated according to a predetermined condition. A threshold level is set, and a data string following the level detection pattern is discriminated based on the set threshold. Here, the threshold level
Set the bell to the receiving device to receive the level detection pattern.
Calculate the average value of 0 level and 1 level respectively
Then, set the intermediate value of the two average values as the threshold level.
You may

A third aspect of the present invention is a data communication method for transmitting digital data, which is modulated by a transmitter according to a transmission data string following a level detection pattern in which logic 0s and 1s are alternately continuous. Signal is transmitted, the receiving device calculates the average value of 0 level and 1 level by receiving the level detection pattern, and sets the threshold level according to a predetermined condition from the average value of each of the 0 level and 1 level, The data string following the level detection pattern is discriminated based on the set threshold value, and the threshold level is sequentially changed based on the discriminated data sequence. Here, the setting of the threshold level,
The receiving device receives 0 level by receiving the level detection pattern.
Calculate the average value of the bell and 1 level respectively, and
The mean value of the average values may be set as the threshold level.

According to the invention of claim 5 of the present application, 0 level and 1
In a receiving device that receives a signal from a transmitting device that transmits a data string following a level detection pattern in which levels are alternately continuous, a receiving unit that receives the signal from the transmitting device and a signal obtained from the receiving unit are provided. An envelope detecting section for performing envelope detection, an average value calculating means for calculating an average value of 0 level and 1 level obtained at the time of transmitting the level detection pattern, and a threshold value from the average value of 0 level and 1 level. It is characterized by comprising a threshold value calculating means and a comparing means for discriminating the envelope detection output by the threshold value calculated by the threshold value calculating means.

According to a sixth aspect of the present invention, in the receiving device according to the fifth aspect , the receiving device has threshold changing means for continuously changing the threshold according to a reception level when receiving a data string. It is characterized by.

[0010]

1 is a block diagram showing the overall configuration of a data communication apparatus according to a first embodiment of the present invention. As shown in the figure, the transmitting device 1 is a transmitting device that performs ASK modulation and transmits a signal. Before transmitting the NRZ data string, “01” is repeated a plurality of times, for example, “0101”.
0101 ”level detection pattern and then NR
It is assumed that an ASK-modulated data string according to Z is transmitted. The receiver 2A has a receiver 11 that receives this signal, and an envelope detector 12 that performs envelope detection of the received signal. The envelope detection output is a sample hold circuit (S).
/ H circuit) 13 to the A / D converter 14. The A / D converter 14 converts an input signal into a digital value and gives it to the microcomputer 15. The microcomputer 15 uses the average value calculating means 15a for calculating the average value of the 0 level and the 1 level when receiving the level detection pattern, the threshold calculating means 15b for calculating the threshold value based on the average value, and the calculated threshold value. It has a function of a comparison means 15c for comparing the data in the data string. The output compared by the comparison means 15c is output to the outside as a data string.

Next, the operation of the data communication apparatus of this embodiment will be described with reference to the time chart of FIG. 2 and the flowchart of FIG. FIG. 2A shows a transmission data sequence transmitted from the transmission device 1. The above-described level detection pattern is transmitted at the beginning of the data frame, and then the NRZ data sequence is subsequently transmitted. FIG. 2B shows the level detection pattern portion of the detection output of the receiving device 2 which receives this signal in an enlarged manner on the time axis. When reception is started, first, 0 is set in step S1 shown in FIG.
The level and the value of the first level are reset, and the data is received in S2. Since "01010101" is sent out in the level detection pattern as described above, the received signal is discriminated at the level of a predetermined preset value, and if it is "0", the process proceeds to step S4 and is added to the 0 level. If the received signal is 1, the process proceeds to step S5 and is added to 1 level. Then, in step S6, it is awaited whether or not the detection period of the level detection pattern has ended, and if not ended, the process returns to step S2 and the same processing is repeated. In this way, by making the detection period coincide with the transmission period of the level detection pattern, the added value of 0 level and 1 level can be obtained within the detection period. If it is outside the detection period, the process proceeds from step S6 to step S7 to calculate the average value of 0 level and the average value of 1 level based on the added value of 0 level and 1 level and the number of times of reception, respectively, and For example, the intermediate value is calculated as the threshold level. Then, the process proceeds to step S8, and thereafter A /
The detection level sent from the D converter 14 is compared with the determined threshold and demodulated. Then, it is checked whether or not the reception is completed, and this process is repeated until it is completed.

In this way, the accurate reference level in the communication state can be determined only by adding the level detection pattern before sending the NRZ, and the communication time can be shortened without using the Manchester code. it can. Further, since the threshold level can be set accurately, communication can be performed even when the transmission device 1 and the reception device 2 are separated from each other, such as when the reception level is low. Therefore, the effect that the communication distance can be extended can be obtained.

FIG. 4 is a block diagram showing the configuration of a data communication apparatus according to the second embodiment of the present invention. In this embodiment, the main part of the demodulation section is configured by hardware. The receiver 2B has a receiver 11 and an envelope detector 12 as in the first embodiment, and the envelope detection output is as shown in the figure.
1,22. Sample and hold circuits 21 and 2
A hold signal for giving a sample hold timing is input to the microcomputer 2 from the microcomputer 23, and the detection output is held at the timing when the 0 level and the 1 level are received by the hold signal, and the output is input to the integrating circuits 24 and 25. Given. Integrating circuits 24, 25
Is for integrating the held output, and its output is given to the sample hold circuits 26 and 27.
The sample-and-hold circuits 26 and 27 output a hold signal from the CPU 23 at the end of reception of the level detection pattern, hold the integrated output at this point, and the output is given to the voltage dividing circuit composed of the resistors R1 and R2. . The resistors R1 and R2 have the same resistance value,
The midpoint is given to the comparator 28 as a threshold value. The comparator 28 uses this threshold value to discriminate the envelope detection output.

Next, the operation of this embodiment will be described. The transmission data string sent from the transmitter 1 is shown in FIG.
Similar to (a), the level detection pattern and the subsequent NRZ data string are used. When transmission is started, in the receiving device 2B, the integrating circuits 24 and 25 are first reset by the reset signal from the CPU 23, and then the sample hold circuits 21 and 22 are alternately held at each transmission timing of 0 and 1. Therefore, the sample hold circuit 2
The detection output is held for each transmission of 1 level at 0 level and the sample hold circuit 22 at 1 level. This output is integrated by integrating circuits 24 and 25, respectively. After the level detection pattern has been transmitted, the CPU 23 outputs a hold signal to the sample hold circuits 26 and 27, so that the integrated output is held. In this state, the calculation of the average value of the 0 level and the 1 level is completed, and the intermediate value of each average value is held as the threshold value by the resistance voltage dividing circuit. Since this threshold value is given to the comparator 28, the subsequent NRZ data string can be demodulated. In this case as well, as in the first embodiment described above, since an accurate threshold level can be set, the communication speed can be improved and the communication distance can be lengthened without using Manchester encoding.

In this embodiment, the sample hold circuits 21 and 22, the CPU 23 and the integrating circuits 24 and 25.
Constitutes an average value calculating means, and the resistance voltage dividing circuit comprising the sample and hold circuits 26 and 27 and the resistors R1 and R2 constitutes a threshold value calculating means.

FIG. 5 is a block diagram showing the configuration of a data communication apparatus according to the third embodiment of the present invention. In this embodiment, the receiving device 2C is similar to that of the first embodiment,
In addition to the average value calculation means 15a, the threshold value calculation means 15b, and the comparison circuit 15c, it has a threshold value change means 15d. The threshold changing means 15d corrects the threshold level according to the fluctuation of the reception level when the NRZ data string is received, and sets it to an appropriate threshold.

Next, the operation of this embodiment will be described with reference to a time chart and a flow chart. The process of calculating the threshold value at the time of transmitting the level detection pattern is the same as that of the first embodiment.
When the Z data string is transmitted, the data is received in step S11. Then, 0 or 1 is determined according to the threshold value set in step S12. If the received data is 0, the process proceeds to step S13 to change the 0 level average value. This change is based on the 0 level data that has already been detected and is the source of the 0 level average calculation.
The oldest one is replaced with the latest detection level determined to be the 0 level, and the 0 level average value is calculated again to change the level. When it is determined that the level is 1 level in step S12, the process proceeds to step S14 to similarly change the average value of 1 level. Then, in step S15, the threshold value is recalculated from the new average values of 0 level and 1 level. In FIG. 7, A indicates the average value level of 1 thus changed, B indicates the average value level of 0, and C indicates the changed threshold level set during the period.
Then, in step S16, it is determined whether or not the reception data has ended. If not, the new threshold value is used to discriminate the reception data. This way, 0 level and 1
Even when the level changes depending on the distance between the transmitting device and the receiving device, an optimum threshold value can always be set, and reliability can be secured even when the level changes.

Although each of the above embodiments describes a general data communication device, the present invention is applied to a data communication method between a read / write head and a data carrier holding data in a contactless identification system. be able to. In this case, the fluctuation of the reception level is large even within the communicable area depending on the position of the data carrier, so that stable communication can be performed by setting a threshold value according to the communication state. Further, when the position of the data carrier changes within the communication area, stable communication can be secured regardless of changes in the reception level by sequentially changing the threshold value as in the third embodiment.

[0019]

As described above in detail, according to the inventions of claims 1 to 6 of the present application, by adding the level detection pattern at the beginning of the data transmission, the data communication can be performed with almost no decrease in the data transmission rate. It can be performed. Therefore, not only improve the data communication speed,
It enables data communication over a long distance. Further claim 3,
According to the inventions 4 and 6 , it is possible to set an appropriate threshold value even when the reception level changes, and it is possible to improve the reliability of communication.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a data communication device according to a first embodiment of the present invention.

FIG. 2 is a time chart showing a transmission data string and a reception level of a reception level detection pattern of the data communication device according to the present embodiment.

FIG. 3 is a flowchart showing an operation of the receiving device according to the present embodiment.

FIG. 4 is a block diagram showing a configuration of a data communication device according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a data communication device according to a third embodiment of the present invention.

FIG. 6 is a flowchart showing an operation of the data communication device according to the third embodiment.

FIG. 7 is a time chart showing changes in reception level and thresholds of the data communication apparatus according to the present embodiment.

FIG. 8 is a block diagram showing an example of a conventional receiving device.

FIG. 9 is a time chart showing a change in a signal transmitted by a conventional data communication device and a reference value.

[Explanation of symbols]

1 transmitter 2A, 2B, 2C receiver 11 Receiver 12 Envelope detector 13, 21, 22, 26, 27 Sample and hold circuit 14 A / D converter 15,23 Microcomputer 15a Average value calculation means 15b Threshold calculation means 15c Comparison means 15d threshold changing means 24,25 integrating circuit 28 Comparator

Claims (6)

(57) [Claims] 1. A data communication method for transmitting digital data, wherein a signal modulated according to a transmission data string is transmitted and received from a transmitter following a level detection pattern in which logic 0s and 1s are alternately continuous. The device calculates an average value of 0 level and 1 level by receiving the level detection pattern, sets a threshold level based on a predetermined condition from the average value of each of the 0 level and 1 level , and based on the set threshold value. And a data string following the level detection pattern is discriminated. 2. The setting of the threshold level is The receiving device receives 0 level by receiving the level detection pattern.
Calculate the average value of the bell and 1 level respectively, and
Claims characterized in that the median of the average values is used as the threshold level
The data communication method according to item 1. 3. A data communication method for transmitting digital data, wherein a signal modulated according to a transmission data string is transmitted and received from a transmitter following a level detection pattern in which logic 0 and 1 are alternately continuous. The device calculates an average value of 0 level and 1 level by receiving the level detection pattern, sets a threshold level based on a predetermined condition from the average value of each of the 0 level and 1 level , and based on the set threshold value. A data string following the level detection pattern is discriminated, and the threshold level is sequentially changed based on the discriminated data string. 4. The setting of the threshold level is set to 0 when the receiving device receives the level detection pattern.
Calculate the average value of the bell and 1 level respectively, and
The data communication method according to claim 3, wherein an intermediate value of the average values is set as the threshold level . 5. A receiving device that receives a signal from a transmitting device that transmits a data sequence following a level detection pattern in which 0 level and 1 level are alternately continuous, and a receiving unit that receives the signal from the transmitting device. An envelope detection unit that performs envelope detection of a signal obtained from the reception unit; an average value calculation unit that calculates an average value of 0 level and 1 level obtained during transmission of the level detection pattern; A receiving device, comprising: a threshold value calculating means for calculating a threshold value from an average value of the levels; and a comparing means for discriminating the envelope detection output by the threshold value calculated by the threshold value calculating means. Wherein said receiving apparatus, receiving apparatus according to claim 5, wherein the one having the threshold value changing means for changing continuously the threshold value according to the reception level during reception of the data sequence.