SU1327315A1 - Frequency-keyed signals detector - Google Patents

Abstract

The invention can be used to demodulate binary frequency-manipulated signals. The purpose of the invention is to increase noise immunity with respect to time-concentrated interference. The device contains an amplitude limiter 1, a delay line 2. An adder 3 modulo two is entered into the detector, a pulse width selector 4 is trigger 5. Because trigger 5 is triggered by the first pulse of the sequence; pulses of longer duration and reset from the first pulse of a sequence of pulses of shorter duration, then a change in the level of the pulses, besides the first ones in the corresponding sequences as a result of interference, does not distort the output signal, 2 or less. with (L with Fig. g with tsD CO ate

Description

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The invention relates to radio engineering and can be used to demodulate binary frequency-shifted signals.

The purpose of the invention is to improve the noise immunity with respect to time-concentrated interference.

Figure 1 shows the structural electrical circuit of the proposed detector; figure 2 - timing diagram.

The detector of frequency-manipulated signals contains amplitude limiter 1, delay line 2, modulo-2 adder 3, pulse width selector 4, trigger 5.

The device works as follows.

The FSK signal U (t) (Fig.26) corresponding to the transmitted code sequence UjjCt) arrives at the amplitude input, the limiter (Fig.2a). At the output of the amplitude limiter 1, a signal UjXt is generated (Fig. 2c), which is fed modulo two to the first input of the summer 3 and to the input of the delay line 2. At the output of the delay line 2 generates / signal Uj (t) (fig.2g), delayed relative to the signal Ui (t) for the time t3-T (, / 2. Signal signal and (t) is fed to the second input of modulator 3 modulo two. At the output of modulator 3 modulo two, a signal U (t) is generated (Fig. 2e), which is a sequence of pulses of different duration: long pulses correspond to positive positives of the transmitted code sequence, and short pulses correspond to negative messages of the transmitted code sequence. This signal is sent to course selector 4 pulse duration at the output of the selector 4 first isolated pulse duration pulses are of longer duration) (2e) and at the second output of the selector -. shorter duration pulses U {(t) (2g). Since

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The difference in the pulse durations of the sequence U (t) is determined by the difference in the carrier frequencies of the signal corresponding to different symbols of information. This necessitates the existence of the minimum allowable difference in the carrier frequencies determined by the possibility of the selector of the duration of pulses by the difference of pulses differing slightly in duration. The pulses Uj (t) are fed to the first (triggering) input of the trigger 5, and the pulses U (t) to the second (resetting) input of the trigger 5. At the output of this trigger 5, the signal U -, (t) is regenerated (Figure 2h), corresponding to the transmitted code sequence.

Since the trigger is triggered from the first pulse of a sequence of pulses of longer duration and is reset from the first pulse of a sequence of pulses of shorter duration, the change in the level of the pulses, besides the first, in the corresponding sequences as a result of interference, does not distort the output signal.

Claims (1)

Invention Formula The detector of frequency-manipulated signals, containing an amplitude limiter, the output of which is connected to the input of the delay line, has been triggered by the fact that, in order to increase the noise immunity with respect to time-concentrated interference, a pulse duration selector and modulo two, the first input of which is connected to the input of the delay line, the output of which is connected to the second input of the modulo two adder, the output of which is connected to the input of the pulse width selector, the first and second outputs of which on are connected to nepBor iy and second inputs of the flip-flop.  fjTJlJTnj one, IJUTJlJlJlJlJinJir U, (t} Ufyft i . Well fijd Tonn s f-y