SU1425867A1 - Demodulator of frequency-manipulated signals - Google Patents

Abstract

The invention relates to communication technology. The purpose of the invention is to improve noise immunity when exposed to chaotic impulse noise. The demodulator contains amplifier-limiter I, inverters 2, 7, and 8 single-oscillators 3-6, elements AND 9-12, PL-OR. 13 and 14, the counters 15 and 16, and the RS flip-flop 17. From the signal input to the input of the demodulator, pulses are generated, which are counted by the counter 16 (15). When a certain threshold value K is reached, (K2) the overflow pulse from the output of counter 16 (15) enters the input of the short-circuit trigger 7, setting it to the zero (single) state. The use of one-shot 3, 5, and 6 allows to increase the demodulation accuracy, and the use of counters 15 and 16, which perform the function of the drives, allows a significant increase in the output signal-to-noise ratio. The goal is achieved by the introduction of single-shot 4-6, inverter 7, zl-t and P-12, elekt-OR 13 and 14 and counters 15 and 16. 1 Il. about (/

Description

The invention relates to communication technology and can be used in discrete information transfer systems.

The purpose of the invention is to improve the noise immunity when exposed to chaotic impulse noise.

The drawing shows a structural electrical circuit of the proposed demodulator. : The demodulator of a frequency-manipulated signal contains an amplifier - Limiter 1, first inverter 2, Jervy 3, second 4, third 5 and fourth 6 single vibrators, second 7 and third 8 inverters, first 9, second 10, third 11 and fourth 12 And elements, the first 13 and second 14 elements OR, the first 15 and second 16 counters, 8-trigger 17..

The demodulator works as follows.

The input frequency-manipulated signal is converted into square pulses with the help of amplifier-limiter 1. Each pulse of the received sequence triggers the first 3, second 4 third 5 and fourth 6 one vibrators with its front edge. The pulse duration of the first single vibrator 3 is equal to the second single vibrator 4 (-4 third single vibrator of the fourth one vibrator

6c-- f-b In this case, the

vie

} i f

When a signal with a frequency f arrives at the demodulator input, the pulse duration at the output of the amplifier - limiter 1 is 1

Of

2f,

When a signal arrives at the demodulator input with a frequency, the duration of the pulses at the output of amplifier - limiter 1 is equal to

T -. ° 2f

The first 3 and second 4 single vibrators are designed to extract a signal with a frequency fj, the third 5 and fourth 6 single vibrators are used to separate a signal with a frequency f, and the following conditions must be met

o / c t f t f .io2. WITH.- .

Let: a signal with frequency f arrives at the demodulator input. Wherein

only at the output of the second element OR 14, pulses with a repetition frequency f appear (, at the output of the first. element OR 13, the voltage is logical O. These pulses are computed by the second counter 16 and when a certain threshold value K is reached, the overflow pulse from the output The second counter 16 is fed to the first input of the RS flip-flop 17, setting it to the zero state.

When a signal arrives at the input of the amplifier limiter 1 with a frequency fj, the switching pulse is formed at the output of the first counter 15 when the threshold K2 is reached. In this case, the RS flip-flop 17 is set to one.

The threshold values Kj and K are determined from the ratio

Kg „ft

K, f,

The use of the first 3, third 5 and fourth 6 single vibrators in the demodulator circuit improves the demodulation accuracy, while the demodulator responds to the input signal frequencies lying in intervals 1 -. , one

 f

2 (G ,, - ТТ „) bh., 2 ()

1, f 1

. (T ,, + r, j) «г 2 (Г, -Т, з)

where t fj W - -;

(- one .-

 - - w

The value of the thresholds K and K can be varied depending on the duration of the elementary packet (i.e., the data rate).

The use of the first 15 and second 16 counters that serve as accumulators significantly improves the output signal-to-noise ratio

The signal from the output of the amplifier-limiter 1 is also fed to the inputs of the first 9 and third II elements I. From their outputs, the signals go to the inputs of the first 13 and second 14 elements OR, respectively, only if their second inputs contain the enable signals from the outputs of the second 7 and third Inverters. The rectangular pulses from the output of the 15th limiting amplifier are passed through the first inverter 2 and are fed to the inputs of the second 10 and fourth 12 elements. And the outputs of which will have pulses only if present at their second inputs of the enabling signals from the outputs of the second A and fourth 6 one-shot.

Form

. A frequency-manipulated demodulator containing a short-circuit trigger and a limiting amplifier whose output is connected to the first input of the first element I, to the input of the first inverter whose output is connected to the first input of the second element And, and to the input of the one-vibrator, the output through which the second inverter is connected to the second input of the first element I, which is related to the fact that, in order to increase the noise immunity under the influence of chaotic impulse noise, the second, third and fourth one-oscillators, the third inverter, the third and And, two elements OR and the first and second counters, the inputs and outputs of which are connected respectively to the outputs of the first and second elements OR and to the inputs of the RS flip-flop, while the output of the amplifier-limiter is connected to the input of the second one-oscillator, the output of which is connected with the second input of the second element And, to the first input of the third element And, the second input of which is connected to the output of the third inverter, to the input of the third one-oscillator, the output of which is connected to the input of the third inverter, and to the input of the fourth one-oscillator, output d is connected to the second input of the fourth AND gate, to the first input of which is connected to the output of the first inverter, the outputs of the first and second AND gates and outputs of the third and fourth AND gates respectively connected to the inputs of the first and second OR elements.

Claims (1)

Formula from gaining $, a Demodulator of frequency-manipulated signals containing an RS-trigger and an amplifier-limiter, the output jq of which is connected to the first input of the first element And, with the input of the first inverter, the output of which is connected to the first input of the second element And, and with the input of a one-shot, the output of which through the second inverter is connected to the second input of the first element And, characterized in that, in order to increase noise immunity under the influence of chaotic pulsed noise, the second, third and fourth single-vibrators are introduced, t this inverter, the third and fourth AND elements, two, respectively, with the outputs of the first and second OR elements and with the inputs of the RS-trigger, while the output of the limiter amplifier is connected to the input of the second one-shot, the output of which is connected to the second input of the second AND element, to the first the input of the third element And, the second input of which is connected to the output of the third inverter, to the input of the third one-shot, the output of which is connected to the input of the third inverter, and to the input of the fourth one-shot, the output of which is connected to the second input of the fourth The And gate, to the first input of which the output of the first inverter is connected, the outputs of the first and second elements And and the outputs of the third and fourth elements And are connected respectively to the inputs of the first and second elements OR.