JPH01226230A - Data transmission equipment - Google Patents

Abstract

PURPOSE:To attain high speed and stable data transmission by setting the difference frequency f3 of a mark frequency f1 and a space frequency f2 and the baud frequency of a second channel to the relation of n:m in a transmission side and extracting f1 and f2 from an FSK demodulation circuit and m- multiplying and n-dividing both frequencies in a reception side. CONSTITUTION:A frequency generation circuit 1 on the transmission side has a liquid crystal oscillator. With frequency-dividing it, the difference frequency of the frequencies f1 and f2, and f3 are set to the relation of 7:240. An addition circuit 4 adds the transmission signals of transmission circuits 2 and 3 and transmits them to a transmission line 10. A receiver 7 has the FSD demodulation circuit and it outputs f1 and f2 with digital data. A multiplication/frequency- devision circuit 9 outputs the frequency f3 by multiplying the difference frequency of f1 and f2 by 240 and frequency-dividing it by seven. The baud clock required for the action of the receiver 8 is supplied from the multiplication/ frequency-division circuit 9. Consequently, the baud clock of the channels can precisely be extracted at high speed and stable data transmission can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data transmission device, and particularly to a data transmission device having a two-channel data transmission/reception function.

[Conventional technology]

For example, a data transmission device having a two-channel data transmission/reception function performs low-speed data transmission using FSK modulation for network monitoring on the first channel when transmitting data using a telephone line, and performs low-speed data transmission on the second channel for network monitoring. It is used to perform original data transmission at high speed using QAM modulation. At this time, the first channel and the second channel are used completely independently, and F S
Mark and space frequencies used for K modulation and QA
The Ho frequencies used for M modulation are created by dividing each frequency from an independent crystal oscillation source, for example, and apart from the nominal value, the actual frequency is not related.

[Problem to be solved by the invention]

In order to increase the amount of information that can be transmitted per unit time,
The second channel must provide the fastest possible data transmission. In order to perform high-speed data transmission, it is necessary to increase the baud frequency or increase the number of data points.

Normally, there is a band limit in a transmission path, so when the baud frequency is increased, the roll-off rate is made smaller in order to alleviate the expansion of the occupied bandwidth as much as possible. However, this increases the required accuracy of baud clock extraction necessary for data determination. Similarly, when the number of multivalued data points is increased, the accuracy required for poke lock extraction also increases.

However, actual baud clock extraction becomes more difficult as the roll-off rate decreases and the number of multivalued data points increases, so as a final measure, the second channel is used solely to stably perform high-speed data transmission. The disadvantage is that it is not easy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a data transmission device that eliminates the above-mentioned drawbacks, performs poke lock extraction of a second channel with high accuracy, and realizes high-speed and stable data transmission.

[Means to solve the problem]

The data transmission device of the present invention provides a relationship between a first frequency, a second frequency, a difference frequency between the first frequency and the second frequency, and n:m (n and m are integers) on the transmitting side. and a first transmitting circuit that performs FSK modulation using the first frequency generated from the frequency generating circuit as a mark frequency and the second frequency as a space frequency. a second transmitting circuit that uses the third frequency generated from the frequency generating circuit as a baud frequency; and an adding circuit that adds the output of the first transmitting circuit and the output of the second transmitting circuit. a separation circuit which outputs an input signal as a signal from the first transmission circuit as a first signal and a signal from the second transmission circuit as a second signal on the receiving side; and the separation circuit. A first receiver inputs a first signal from the first receiver, and inputs a first frequency and a second frequency output from the first receiver, and multiplies the difference frequency by m and divides by n. and a second receiver which inputs the second signal from the separation circuit and uses the output of the frequency divider as a baud clock.

[Effect]

On the transmitting side, the difference frequency between the mark frequency and the space frequency and the baud frequency of the second channel are set as n:m(n
, m is an integer).

On the receiving side, it is possible to extract mark frequencies and space frequencies from the FSK demodulation circuit in an extremely stable manner. Therefore, by multiplying the difference frequency by m and dividing by n, a stable baud clock for the second channel can be obtained. By using this relatively stable baud clock, high-speed and stable data transmission can be performed through the second channel.

Offset frequencies may exist in the transmission path, but
Even in this case, since the mark frequency and the space frequency receive the same amount of offset, the influence of the offset can be removed by focusing on the difference frequency.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

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

The frequency generating circuit on the transmitting side has a crystal oscillator, and by dividing it, the frequencies fl (20Hz) and f2 are generated.
(90Hz), f3 (2400Hz). f
There is a relationship of 6-7:240 between the difference frequency between l and f2 and f3.

The transmitting circuit 2 generates an FSX modulated transmission signal with frequency f1 as a mark frequency and f2 as a space frequency, thereby performing low-speed data transmission.

The transmitting circuit 3 has a poke lock on the frequency f3, a carrier frequency of 1600 Hz, a roll-off rate of 10%, and a 16-value Q.
It generates an AM modulated transmission signal and performs data transmission at 9600 bits per second.

Adder circuit 4 adds the transmission signals of transmission circuits 2 and 3 and sends the result to transmission line 10 .

The bandpass filter 5 on the reception side has a center frequency of 100Hz.
, the bandwidth is 180 Hz, and only the output of the transmitting circuit 2 is extracted from the added transmitting signals.

The bandpass filter 6 has a center frequency of 1600H1 and a bandwidth of 2640Hz, and extracts only the output of the transmission circuit 3 from the added transmission signals.

The receiver 7 is a receiver having an FSK demodulation circuit, and outputs a mark frequency fl (20 Hz) and a space frequency f2 (90 Hz) together with digital data. This is achieved, for example, by using tank circuits that are resonant at fl and f2, respectively.

The frequency multiplying/dividing circuit 9 outputs a frequency f3 (2400 Hz>) by multiplying the difference frequency (70 Hz) between fl and f2 output from the receiver 7 by 240 and dividing the frequency by 7.

The receiver 8 is a normal QAM receiver without the poke lock extraction circuit, and the poke lock (24,00 Hz) necessary for the operation of the receiver 8 is supplied from the frequency/multiplier circuit 8.

〔Effect of the invention〕

As explained above, the present invention enables high-speed poke lock extraction of channels, which has been difficult in the past, to be performed with high precision.
This has the effect of enabling a data transmission device that realizes stable data transmission.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a data transmission device of the present invention. 1... Frequency generation circuit, 2.3... Transmission circuit, 4...
・Addition circuit, 5, 6...Band pass filter, 7, 8
. . . Receiver, 9 . . . Multiplying frequency dividing circuit, 10 . . . Transmission line.

Claims (1)

[Claims] On the transmitting side, a first frequency, a second frequency, a difference frequency between the first frequency and the second frequency, and n:m(n
, m is an integer), and FSK modulation using a first frequency generated from the frequency generating circuit as a mark frequency and a second frequency as a space frequency. a second transmitting circuit that uses a third frequency generated from the frequency generating circuit as a baud frequency; and an output of the first transmitting circuit and an output of the second transmitting circuit. and an adder circuit that adds the input signal from the first transmitting circuit to the second signal on the receiving side.
a separation circuit that outputs the signal from the transmission circuit as a second signal, a first receiver that receives the first signal from the separation circuit, and a first signal output from the first receiver. 1 frequency and a second frequency and divides the difference frequency by m and by n; A data transmission device comprising: a second receiver used as a baud clock.