RU2232475C1 - Method for enhancing security of narrow-band signal group transmission - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: method includes radiation of useful and masking signals, their addition, conversion of masking signal and its further rejection. Proposed method is characterized in that group of useful signals is radiated irrespective of masking signal and the latter is radiated in frequency band of entire group of useful signals; masking signal is shaped from narrow-band signal by expanding its spectrum using frequency or phase modulation whose mechanism is familiar for home receiver; all input signals including marking one are converted so that masking signal spectrum is contracted and spectrums of other input signals are expanded; then masking signal is rejected and remaining input signals are recovered.

EFFECT: enhanced security of narrow-band signal group transmission.

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Description

The present invention relates to the field of radio engineering and can be used in equipment designed to operate in electronic warfare (EW), when the transmission of signals is accompanied by their reconnaissance and suppression by the enemy.

Reliability of information transmission in EW conditions significantly depends on the energy and structural secrecy of the applied signals. Currently, narrow-band systems, whose signals have low stealth, are most widespread.

Known methods for increasing signal stealth are based on the transition to complex phase-manipulated signals, coherent frequency-manipulated signals, to incoherent signals with pseudo-random tuning of the operating frequency (Interference immunity of radio systems with complex signals. Edited by G.I. Tuzov. M.: Radio and communication, 1985).

However, this way requires a radical modernization of the equipment and cannot ensure the secrecy of the transmission of narrow-band signals of existing radio facilities.

The well-known "Method for masking a transmitted message" (Application Germany (DE) No.OS 3605350, Н 04 К 1/02, 1987), according to which a masking signal is synchronously superimposed on the useful signal on the transmitting side, which does not carry information, the formation law of which is known, therefore on the receiving side, it can be separated from the desired signal. But at the same time only one useful signal is masked, which is a drawback of this method.

Closest to the proposed method is a method for transmitting a masked signal (E.V. Kalyanov. Information transfer when using coding of masking chaotic oscillations. - Radio engineering and electronics, 2002, v. 47, No. 4, Fig. 1, p. 469), adopted as a prototype.

Method - prototype is as follows.

In the transmitter, the formation of the useful and masking signals is combined, and two-channel transmission is used: only the masking signal is transmitted on the second channel, and the same signal, converted in amplitude and phase, summed with the useful signal, is transmitted on the first channel. At the input of "their" receiver, an interference suppression unit is included in which the masking signal transmitted on the second channel is subjected to a conversion similar to that in the transmitter and subtracted from the total signal transmitted on the first channel. As a result of eliminating the masking signal, only the useful signal remains. At the input of a “foreign” receiver, the sum of the useful and masking signals, i.e. the structure of the desired signal will be hidden.

The disadvantage of the prototype method is that it allows you to mask the signal of only one transmitter, although often masking a group of "their" transmitters.

To eliminate this drawback in the method, which consists in emitting a useful and masking signals, summing them, converting the masking signal and its subsequent elimination according to the invention emit a group of useful signals regardless of the masking, and the radiation of the masking signal is carried out in the frequency range of the entire group of hidden signals, masking signal formed from a narrow-band signal by expanding its spectrum due to frequency or phase modulation, the law of which is known to "their" receiver m, convert all input, including masking signals so that the spectrum of the masking signal is narrow, and the spectra of the remaining input signals extend further masking signal are rejected, and then reduced the remaining input signals.

Graphic materials illustrate the invention.

FIG. 1 is a functional diagram of a communication system that implements the proposed method.

FIG. 2 is a functional diagram of a spectrum spreading unit.

FIG. 3 - waveforms at various points in a communication system that implements the proposed method:

a) is the shape of the useful signal (in this case, amplitude-modulated) at the output of the useful signal generator 1;

b), c) is the shape of the masking signal (in this case, phase-shifted) at the output of the spectrum expansion unit 2 ¹ ;

g) - the waveform at the input of "their" receiver 10 ¹ ;

d) - the waveform at the input of the "alien" receiver 10 ² .

A functional diagram of a communication system in which the proposed method is implemented is shown in FIG. 1, where it is indicated: I - a masking signal transmitter; II - noise suppressing unit; III - notch filter; 1 - useful signal generator (radio link transmitter); 2 ¹ , 2 ² - spectrum expansion units; 3 - narrowband signal generator; 4 ¹ , 4 ² - communication lines (channels); 5 ¹ , 5 ² - receiving antennas playing the role of signal adders; 6 - block convolution spectrum of the masking signal; 7 - band-pass filter; 8 - block synchronization; 9 is a subtractive circuit; 10 ¹ - receiver of "their" radio link; 10 ² - receiver of the "alien" radio line.

In this system, as an example, one "own" radio line is presented, which may be several, consisting of a useful signal generator 1, a communication line (radio) 4 ¹ , a receiving antenna 5 ¹ , an interference suppression unit II, and "own" receiver 10 ¹ .

The masking signal transmitter I contains a narrowband signal generator 3 and a spectrum spreading unit 2 ¹ and, in fact, is a transmitter of obstruction, which, in addition to masking signals in its frequency band, can suppress "alien" receivers.

The power amplifier and transmitting antenna are not of fundamental importance, therefore, are not shown in Fig. 1.

The masking signal enters the receiving antennas of "their" 5 ¹ and "alien" 5 ² radio lines through the communication line 4 ² (over the air). The receiving antenna 5 ^{2 is} connected to the input of a "foreign" receiver 10 ² .

The operation of this radio system is as follows.

In the transmitter I, the masking signal is formed from a narrow-band signal generated by the generator 3 by expanding its spectrum in block 2 ¹ due to frequency or phase modulation.

In the receiving antennas 5 ¹ , 5 ^{2, the} masking signal is summed up with the useful generated by the generator 1, as a result of which, for "foreign" receivers, all signals in the frequency band of the masking signal are hidden. At the input of "their" receivers included stand-alone noise suppressing units II, eliminating the masking signal.

In the convolution unit of spectrum 6, the modulation superimposed in the expansion unit of spectrum 2 ¹ is removed from the masking signal, as a result of which it narrows and again turns into a narrow-band signal, which is notched (cut out) by notch filter III, which is represented as a combination of a band-pass filter 7 and subtracting circuit 9. In this case, all other input signals in the convolution unit of spectrum 6 are superimposed with frequency or phase modulation, similar to the modulation of the masking signal, as a result of which they turn into wideband signals. The notch filter III cuts out only a small fraction of their spectrum. The output of the subtracting circuit 9 contains all the input signals modulated in block 6, except for the masking one. The restoration of the remaining input signals is carried out in the expansion unit of the spectrum 2 ² by removing from them the modulation imposed in block 6.

The combination of the modulating signals in time occurs in the synchronization unit 8.

As a result, at the output of the noise suppressing unit II, all but the masking input signals are restored, one of which receives its “own” receiver 10 ¹ .

At the input of a “foreign” receiver 10 ^2, all signals are suppressed by a powerful masking signal and their reception and processing become impossible.

Examples of the execution of the synchronization unit 8 are given, for example, in the book (Varakin L.E. Communication systems with noise-like signals. - M .: Radio and communications, 1985, pp. 297-303).

The expansion units of the spectrum 2 ¹ and 2 ² can be performed, for example, on the basis of a shaper of multiphase phase-shifted signals (Fig. 2), where it is indicated: 1 - delay line; 2 ¹ - 2 ⁴ - descriptors; 3 ¹ - 3 ⁴ - keys; 4 - reading unit; 5 - memory block; 6 - adder.

На отводах линии задержки 1 формируются синусоидальные колебания с начальными фазами 0°, 90°, 180°, 270°. Очевидно, линию задержки 1 можно заменить набором соответствующих фазовращателей. В блоке памяти 5 записан закон фазовой манипуляции в виде последовательности чисел, соответствующих определенному значению фазы (например, 00, 01, 10, 11). Блок считывания 4 последовательно выводит эти числа из памяти. Каждый из дешифраторов 2¹-2⁴ настроен на соответствующее число и при его появлении вырабатывает импульс, отпирающий соответствующий ключ 3¹-3⁴. В результате на выходе сумматора 6 из синусоидального напряжения с частотой f₀ формируется 4-фазный фазоманипулированный сигнал, ширина спектра которого определяется тактовой частотой считывания.This device can generate a 4-phase phase-shift keyed signal. The input of the delay line 1 receives a sinusoidal signal with a frequency f ₀ . Period of this oscillation

Sinusoidal oscillations with initial phases of 0 °, 90 °, 180 °, 270 ° are formed at the taps of the delay line 1. Obviously, delay line 1 can be replaced with a set of appropriate phase shifters. In the memory block 5, the law of phase manipulation is recorded in the form of a sequence of numbers corresponding to a certain phase value (for example, 00, 01, 10, 11). The reading unit 4 sequentially displays these numbers from memory. Each of the decoders 2 ¹ -2 ^{4 is} set to the corresponding number and, when it appears, it generates a pulse that unlocks the corresponding key 3 ¹ -3 ⁴ . As a result, at the output of adder 6 from a sinusoidal voltage with a frequency f ₀ , a 4-phase phase-shifted signal is formed, the spectrum width of which is determined by the read clock frequency.

To avoid deep amplitude modulation while limiting the spectrum of this signal, it is necessary that the phase difference between adjacent elements of the signal does not take values of ± 180 °, i.e. manipulation similar to 4-phase phase shift manipulation should be used. With this manipulation, the phase changes by 0 °, + 90 °, -90 ° (Spilker D.Zh. Digital satellite communications. Transl. From English under the editorship of V.V. Markov. - M.: Communication, 1979, p. 284-287).

The convolution unit of spectrum 6 can be performed in the same way, but the keys must be opened in a different sequence: if an element with a phase of 0 ° arrives, the key 3 ¹ opens in the 0 ° tap, if + 90 °, the key 3 ⁴ in the + 270 ° tap (-90 °), if + 180 °, key 3 ³ in the bend + 180 ° (-180 °), if + 270 °, -key 3 ² in the bend + 90 ° (-270 °).

Since the law of phase shift keying is known to "its" receiver, the convolution unit of spectrum 6 restores the sinusoidal oscillation from the input masking 4-phase phase-shifted signal.

Schemes of transmitters and receivers of complex phase-manipulated signals and their blocks are given, for example, in the book (L. Varakin, Communication Systems with Noise-Like Signals. - M.: Radio and Communication, 1985).

Claims (1)

A method of increasing the secrecy of the transmission of a group of narrow-band signals, which consists in emitting a useful and masking signals, summing them up, converting a masking signal and its subsequent elimination, characterized in that they emit a group of useful signals regardless of the masking, and the radiation of the masking signal is carried out in the frequency range of the entire group of useful of signals, a masking signal is formed from a narrow-band signal by expanding its spectrum due to frequency or phase modulation, the law of which WEST "his" receivers convert all input, including masking signals so that the spectrum of the masking signal is narrow, and the spectra of the remaining input signals extend further masking signal are rejected, and then reduced the remaining input signals.

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