JPH09181778A - Data transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a normal digital value with a simple device with respect to the digital value of multilevel signal data transmitted to a receiver while being attenuated by being passing through a wired transmission line from a transmitter. SOLUTION: Prior to transmission of multilevel signal data, a transmitter 2 sends an analog reference signal with a prescribed amplitude to a receiver 3 via a wired transmission line 1. The receiver 3 reads a digital value with respect to an input voltage of the reference signal, that is, a level and a digital value at a bias point, that is, a bias to obtain a reference level from them and obtains a relation between an attenuation and a digital value in the transmission line based on the reference level and the prescribed amplitude. A digital value conversion table is generated from the relation above. Then communication is started and the digital value of the multilevel signal data is set based on the conversion table.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wired data transmission method such as an intercom and, more particularly, to a data transmission method capable of identifying a data value without using an AGC circuit or the like even when the reception level of data changes. .

[0002]

2. Description of the Related Art Conventionally, a method of transmitting data by wire is used in an intercom, and an OFD is used by using a modulation / demodulation device that does not limit the use of frequency bands.
Data is transmitted by encoding and decoding by the M (Orthogonal Frequency Division Multiplexing) method. Such OFD
In data transmission in the M system, the band of the frequency to be used is severely limited, and it is necessary to be strong against noise and multipath. Therefore, a sine wave or the like is used as a carrier for frequency multiplexing.

Such a conventional data transmission device is shown in FIG.
As shown in FIG. 3, a transmitter 12 and a receiver 13 connected by a transmission line 11 are provided. The transmitter 12 encodes data to be transmitted and sends it to the transmission line 11. Further, the receiver 13 is provided with an amplifier 14 for amplifying an analog signal transmitted from the transmitter 12 via the transmission path 11, and an A / D converter 15 for A / D converting the amplified analog signal, CP that outputs the final data as a digital signal
U16 is provided.

In such a data transmission device, the data received by the receiver 13 is transmitted from the transmitter 12 by the voltage Va.
Is transmitted, the transmission line 11 is attenuated during transmission to become the voltage Vb. Therefore, for example, when A / D conversion is performed by the A / D converter 15 according to the conversion table shown in FIG. 5, the conversion table outputs an integer value converted according to the level of the signal input to the receiver 13 as a digital output. Therefore, the value originally "2" is converted into "1", and the obtained converted value becomes an incorrect value. For this reason, when transmitting data from the transmitter 12, as shown in FIG. 6, a reference level signal, for example, a horizontal synchronizing signal is added to the beginning of the data, and the data is transmitted to the receiver 13 with automatic gain variable ( AGC) circuit 17 is provided, and a level signal is taken out for each data received by AGC circuit 17, whereby the gain of amplifier 14 is changed to voltage Vc (FIG. 5), and data corresponding to the transmission level is obtained. There is.

[0005]

In such a data transmission device, as described above, the amplifier, the AGC circuit, etc. are required, and when transmitting data, the level signal serving as the reference is set for each data. Since it has to be added and transmitted, the device has become large-scale and the number of parts has increased.

The present invention has been made in order to solve such a problem, and it eliminates the need for an AGC circuit, does not transmit a level signal serving as a reference for each data, and receives data received by a receiver. It is an object of the present invention to provide a data transmission method that can correct a change in voltage and obtain normal data.

[0007]

In order to achieve the above object, the data transmission method of the present invention transmits multi-valued signal data having multi-valued amplitude from a transmitter to a receiver via a wired transmission path. At this time, the transmitter transmits a reference signal with a predetermined amplitude before transmitting the multi-level signal data, and the receiver reads the level value and bias value of the attenuated reference signal via the wired transmission line and then outputs the reference level. Is set, and the amplitude of the received multilevel signal data is compared with a reference level for identification.

In the data transmission method of the present invention, first, a reference signal having a predetermined amplitude is transmitted from a transmitter, transmitted through a wire transmission line, and a digital value obtained by digitally converting a voltage of an analog signal received by a receiver. That is, the level value is read, the digital value obtained by digitally converting the voltage at the bias point, that is, the bias value is read, and the reference level is obtained as the level value-the bias value. A digital conversion table is created from the obtained reference level and bias value. When transmitted through the same wired transmission path, the amount of attenuation is considered to be constant. Therefore, the multi-valued signal data transmitted from the transmitter, transmitted through the same wired transmission path, and received by the receiver was A / D converted. Data corresponding to the transmission level can be obtained by converting the digital signal based on the conversion table.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A detailed description will be given below of an embodiment of a data transmission apparatus of a preferred OFDM communication system to which the data transmission method of the present invention is applied, with reference to the drawings. The data transmission device S shown in FIG. 1 includes a transmitter 2 and a receiver 3 connected by a transmission line 1, and the receiver 3 includes a transmitter 2 to a transmission line 1.
An amplifier 4 for amplifying the transmitted analog signal, an A / D converter 5 for A / D converting the amplified analog signal are provided, and a CPU 6 for determining final data based on the digital signal is provided.

In such a data transmission device S,
It can be assumed that the amount of attenuation that the data transmitted from the transmitter 2 is attenuated while being transmitted through the transmission line 1 and received by the receiver 3 is constant in the case of a constant transmission line. Therefore, the amount of attenuation in a certain transmission line is set before starting communication. As shown in FIG. 2, in order to set the attenuation amount, first, the transmitter 2 sends a reference signal having a predetermined amplitude. The reference signal is a signal having an amplitude such that the difference between the digital value obtained by digitally converting the input voltage and the digital value obtained by digitally converting the voltage at the bias point should be 1, for example. As shown in FIG. 3, the reference signal is input to the receiver 3, amplified by the amplifier 4, digitally converted by the A / D converter 5, and input to the CPU 6, which is a digital value with respect to the input voltage Vr, that is, a level value ( Read Dr). Further, the CPU 6 reads the digital value with respect to the voltage Vb at the bias point of the reference signal, that is, the bias value (Db), and the difference (Dr-Db) between the digital value (Dr) with respect to the input voltage and the digital value (Db) at the bias point. )
Is calculated to obtain the reference level (Dw). The difference 1 between the level value and the bias value when there is no attenuation in transmission is compared with the reference level (Dw), and the reference level (Dw) and the level value (Dr) are output from the A / D converter 5. A conversion table showing the relationship between the digital value and the conversion value corresponding to the transmission level is set. The conversion value of the conversion table is
For example, as shown in FIG. 3, the range of the digital output output from the A / D converter 5 is {Db + (2n-1) Dw.
/ 2 + n} to {Db + (2n + 1) Dw / 2 + n} is set as the conversion value n. As described above, the analog input value of the A / D converter 5 only needs to match the dynamic margin of the input range, and does not have to correspond to the digital conversion value.

After such a conversion table is set,
Start communication. From the transmitter 2, it is not necessary to transmit a reference level signal for each data, and only the multilevel signal data itself may be transmitted. The multilevel signal data of the analog signal transmitted through the transmission path 1 is received by the receiver 3, amplified by the amplifier 4, converted into a digital signal by the A / D converter 5, and input to the CPU 6. The converted value is set from the digital value based on the above, and the final data corresponding to the transmission level is obtained.

The above description is about the embodiment applied to the data transmission device of the OFDM communication system. However, the present invention does not use a sine wave as a carrier for frequency multiplexing even in the OFDM communication system, and particularly, the transmitter. From Hadamard matrix based on Hadamard matrix, data is encoded by inverse Hadamard transform, transmitted through a transmission line, and an analog signal received by a receiver is subjected to Hadamard transform based on Hadamard matrix and decoded. Three
No. 11073), data can be transmitted by a circuit having a very small data memory capacity. Further, the present invention can be applied not only to the Hadamard OFDM communication system but also to a device for transmitting data through a wired transmission line using a multi-level modulation system such as ASK or QPSK or a baseband NISC system.

[0013]

As is apparent from the above description, according to the data transmission method of the present invention, before transmitting multi-valued data via the wired transmission line, the data attenuation depending on the attenuation of the data generated in a certain transmission line is performed. Obtain the conversion table that adjusts the fluctuation of the generated digital value, then start communication and obtain the converted value from the digital output value of the multi-valued signal data based on the conversion table to adjust the fluctuation of the digital value due to attenuation. Therefore, it is not necessary to add a reference signal for each data for transmission, and data corresponding to the transmission level can be obtained without using AGC.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a data transmission device to which the present invention is applied.

FIG. 2 is a diagram showing a flowchart of a main part of a data transmission method of the present invention.

FIG. 3 is an explanatory diagram illustrating data conversion by the data transmission method of the present invention.

FIG. 4 is a block diagram showing a conventional data transmission device.

FIG. 5 is an explanatory diagram illustrating data conversion by a conventional data transmission method.

FIG. 6 is an explanatory diagram illustrating conversion of data by a conventional data transmission method.

[Explanation of symbols]

 1 ··· Wired transmission line 2 ·· Transmitter 3 ·· Receiver Dr ··· Level value Db ··· Bias value Dw ·· ... Reference level

Claims (1)

[Claims] 1. When transmitting multivalued signal data having multivalued amplitude from a transmitter to a receiver via a wired transmission line,
The transmitter transmits a reference signal having a predetermined amplitude before transmitting the multilevel signal data, and the receiver receives the level value (Dr) of the reference signal attenuated via the wired transmission path.
And the bias value (Db) are read, and the reference level (Dw =
After setting Dr-Db), the amplitude of the received multilevel signal data is compared with the reference level to identify the data transmission method.