SU1646069A1 - Discrete signal detector in frequency telegraphy - Google Patents

Abstract

Detector of discrete signals of frequency telegraphy. The invention relates to radio engineering and can be used in the construction of receivers of discrete signals of frequency telegraphy. The purpose of the invention 7 is not to improve noise immunity in the presence of intersymbol interference. The detector contains limiting amplifiers 1 and 2, narrow-band filters 3 and 4, amplitude detectors 5 and 6. low-pass filters 7 and 8, subtraction unit 9, additional amplitude detector 10, additional low-pass filter 11, threshold unit 12, keys 13 and 14. The goal is achieved by the fact that in the pauses between pulses the keys 13 and 14 open and shunt narrow-band filters 3 and 4. Due to this, there is no intersymbol interference in the output signal due to transients in the resonant circuits. 2 Il.

Description

with

WITH

The invention relates to radio engineering and can be used in the construction of receivers of discrete signals of frequency telegraphy.

The aim of the invention is to improve noise immunity in the presence of intersymbol interference.

FIG. 1 shows the structural electrical circuit of the detector; in fig. 2 - timing diagrams showing detector operation.

The detector contains limiting amplifiers 1 and 2, narrow-band filters 3 and 4, amplitude detectors 5 and 6, low-pass filters 7 and 8, subtraction unit 9, additional amplitude detector 10, additional low-pass filter 11, threshold unit 12, keys 13 and 14.

The detector works as follows.

The input signal (Fig. 2a) is fed to limiting amplifiers 1 and 2, in which the parasitic amplitude modulation is eliminated, and then through narrowband filters 3 and 4 (Fig. 26) to detectors 5 and 6. where the envelope signal is selected (Fig. 2c), which is filtered by filters 7 and 8 and fed to subtraction unit 9.

The envelope of the input signal (Fig. 2a) is also separated by an additional detector 10 and filter 11 and is fed to the input of the threshold unit 12, where the received signal is compared with the optimal threshold equal to half the amplitude of the signal.

The pulse sequence formed by the threshold unit 12 (Fig. 2d) is fed to the control inputs of the keys 13 and 14. In the absence of a signal at the detector input, the keys 13 and 14 are opened, bypassing

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narrow-band filters 3 and 4 with their low resistance, drastically reducing their Q-factor. Narrowband filters are made in the form of resonant circuits. In the remaining moments, the keys 3 and 4 are open, their resistance is large and does not affect the parameters of the E-band filters 3 and 4. As a result, the output signal (Fig. 2e) has no pulses due to transient and other parasitic processes in the path, as well as noise interference in the pause between pulses.

Claims (1)

DETAILED DESCRIPTION OF THE INVENTION A discrete frequency telegraphy detector comprising two signal path branches, each consisting of a series-connected limiter amplifier, a narrowband filter, an amplitude detector and a low pass filter, and a subtraction unit whose output is the detector output, low pass filter outputs both branches are connected respectively to the first and second inputs of the subtraction unit, and the inputs of the limiting amplifiers o6etft branches are the input of the detector, which also differs in that In order to improve noise immunity in the presence of intersymbol interference, an additional amplitude detector, an additional low-frequency filter and a threshold block are entered in series, and a key is placed in each signal path — the output of which is connected to the amplitude detector input of the corresponding signal path branch; the limiter amplifier is connected to the first input of the corresponding key, the output of the threshold unit is connected to the second inputs of the keys of both signal paths, and the input of the additional amplitude detector is connected to the inputs of the limiting amplifiers of both signal paths. - {that Hhhhih at - ChlögUlg