SU1283993A1 - Telegraph signal transmission system - Google Patents

Abstract

Invention m. used to transmit discrete information with reduced bandwidth. The purpose of the invention is to reduce distortion, narrowing the spectrum of transmitted signals and simplify the system. The system comprises on the transmitting side a low-pass filter 1, a differentiation unit 10; on the receiving side - local oscillator 2, AGC block 3, filters, 4 and 8, divider 5 level, balanced modulator 6, notch filter 7, adder 9, integrator 11. Transmitting only the lower frequency band narrows the spectrum of the emitted signal in case of using the transmitted signal as modulating, for example, in FM. Due to the differentiation, the upper and lower frequency bands are symmetrical, thus avoiding the occurrence of irreversible distortions of the signal being restored on the receiving side. 1 il. i

Description

N9

00 WITH

with f

oo

The invention relates to telecommunications and can be used to transmit discrete information with a reduced frequency band.

The purpose of the invention is to reduce distortion, narrowing the spectrum of transmitted signals and simplify the system. .

The drawing shows a structural electrical circuit of a telegraph signal transmission system.

The telegraph transmission system contains a low-pass filter 1 on the transmitting side, and a local oscillator 2, an automatic gain control unit 3, a first filter 4, a divider level 5, a balanced modulator 6, a notch filter 7, a second filter 8, and an adder 9 on the receiving side. and also contains on the transmitting side a differentiation unit 10, and on the receiving side an integrator P.

The telegraph transmission system operates as follows.

The telegraph signal a (t) on the transmitting side, having a spectrum limited by the O-F band, the senses of which have a duration C r.avnuyu n / F (n 1,2,3 ...), goes to differentiation unit 10, as a result which means that the output of this block makes the spectrum of the transmitted signal symmetrical about the frequency F / 2. The low-pass filter 1, which has a cut-off frequency equal to F / 2, allocates the lower band of the spectrum of the signal transmitted to the communication channel.

The received signal is fed to the automatic gain control unit 3 and to the first filter 4, made in the form of a low-pass filter with a limiting frequency F / 2, which serves to eliminate interference with frequencies above F / 2 occurring in the communication channel.

From the output of the first filter 4, the signal through a divider 5 of the level arrives: to the first input of the balanced modulator 6, to the second input of which a reference signal is fed from the local oscillator 2 generating frequency F.

The balance modulator 6 serves to restore the upper frequency band of the signal, filtered on the transmitting side, to the received lower band.

The spectrum of the signal at the output of the balanced modulator consists of

 U

useful F / 2-F and harmful F --- ps

F los, with a useful strip - - F

symmetric to the received lower band O - F / 2 relative to the frequency F / 2. From the output of the balanced modulator 6, the signal goes to a notch filter 7, tuned to the local oscillator frequency, and to the second filter 8, made in the form of a bandpass filter,

F excreting useful band -t- - F.

The components of the upper frequency band thus reconstructed from the output of the second filter 8 are fed to the first input of the adder 9, the second input of which from the divider level 5 is supplied to the components of the received lower band. In the adder 9, the bands are combined. A divider level 5 provides for combining the bands with the necessary levels. From the output of the adder 9, the signal goes to the integrator 11, with which the original signal a (t) is restored.

In the practical implementation of the system, the differentiation unit 10 can be performed on the operational units of the first order, and the low-pass filters 1 and 4 and the band-pass filter 8 in the form of digital filters based on the frequency sampling.

The use of a preparative ()) system, as compared with the prototype, makes it possible to significantly simplify the equipment of the transmitting side, and the transmission of only the lower frequency band leads to a narrowing of the spectrum of the emitted signal if the transmitted signal is used as a modulating signal, for example, with frequency modulation. In addition, the transmission in the prototype only the upper frequency band leads to distortions

recoverable on the receiving side of the signal, since the upper and lower frequency bands do not have symmetry. In the proposed system, due to differentiation, both bands become symmetrical, thus avoiding the occurrence of irreversible distortions of the signal being restored on the receiving side.

Claims (1)

Formula invented A telegraphic transmission system comprising on the transmitter side a low-frequency converter, and on the receiver side — a local oscillator and a series-connected automatic gain control unit, a first filter, a level divider, a balanced modulator, a notch filter, a second filter and an adder, whose second input is connected to the second output of the level divider, while the output of the local oscillator is connected to the second input of the balanced modulator, the input of the automatic gain control unit is a linear input of the system, characterized by m that, in order to reduce distortion SRI, narrowing the spectrum of transmitted signals and simplifying the system by eliminating the local oscillator, balanced modulator, notch filter, adder and high-pass filter on the transmitting side, a differentiation unit is inserted on the transmitting side, the output of which is connected to the low-pass filter input, whose output is the linear output of the system, the information input of which is the input of the differentiation unit, and on the receiving side an integrator is introduced through which the output of the adder is connected with the information output of the system themes, with the first filter made in the form of a low-pass filter, and the second filter is in the form of a bandpass filter.