RU2735923C1 - Coherent radio link - Google Patents

Abstract

FIELD: wireless communications.

SUBSTANCE: invention relates to radio communication, to systems using artificially created radio interference in their operation. Result is achieved by using complex signals with phase manipulation and pseudorandom tuning of operating frequency. Coherent radio link comprises a discrete message source, a coding device, two modulators, two transmitters, two transmitting antennae, two pseudorandom sequence generators, high-frequency generator, a receiving antenna, a receiver, three synchronous detectors, a frequency search unit, a reference voltage selection unit, phase shifters for -30°, by +30°, two subtractors, phase shifter by +90°, a decoding device, a unit for recording and analysing messages, a digital scrambler, a digital descrambler, a synchroniser and a carrier frequency synthesizer.

EFFECT: technical result is high reliability of protecting confidential discrete information from unauthorized access.

1 cl, 4 dwg

Description

The proposed coherent radio link belongs to the field of radio communication, namely to the construction of radio communication systems using artificially created radio interference in their operation, and can be used to transmit confidential information using complex signals with phase-shift keying (PSK) with pseudo-random frequency tuning (PFC) and cryptographic methods of its protection.

Known radio links and systems for the transmission of analog and discrete information (ed. USSR certificates No. 1.267.257, 1.291.984, 1.626.428, 1.798.738; RF patents No. 2.001.531, 2.013.018, 2.019.052, 2.108 .257, 2.156.551, 2.214.691, 2.215.370, 2.278.047, 2.286.026, 2.329.608, 2.348.560, 2.447.598; US Patents Nos. 4.328.581, 5.058.136, 5.077.538 , 5.459.760, 5.856.027, 6.128.476; EP patents No. 0.465.512, 0.486.839; patents WO No. 96 / 10.309, 97 / 20.438; Dikarev V.I., Zarenkov V.A., Zarenkov DV, Koinash BV Protection of objects and information from unauthorized access. Publishing house Stroyizdat SPb, 2004, 318s and others).

Of the known radio lines and systems, the closest to the proposed one is "Coherent radio line" (RF patent No. 2.447.598, HO 4 L 27/18, 2010), which was chosen as a prototype.

The specified radio link provides protection of transmitted discrete information from unauthorized access by unauthorized persons by creating a noise curtain of noise-like signals and using cryptographic methods.

However, the potential capabilities of the known coherent radio link to protect transmitted discrete information from unauthorized access by unauthorized persons are not fully exploited.

The technical objective of the invention is to expand the functionality of a coherent radio link and increase the reliability of protecting confidential discrete information from unauthorized access by unauthorized persons by using complex signals with phase shift keying and pseudo-random frequency tuning.

The problem is solved by the fact that a coherent radio link containing, in accordance with the closest analogue, on the transmitting side sequentially connected source of discrete messages, an encoder, a digital scrambler, the first modulator, the first transmitter and the first transmitting antenna, the first pseudo-random sequence generator connected in series, the second a modulator, the second input of which is connected to the output of the second high frequency generator, the second transmitter and the second transmitting antenna, and on the receiving side a receiving antenna, a receiver, a frequency search unit, a reference voltage extraction unit, the second input of which is connected to the output of the receiver, a synchronous detector, the second input of which is connected to the output of the receiver, a second subtractor, a digital descrambler, a decoding device and a block for recording and analyzing messages, connected in series to the output of the reference voltage extraction unit; a phase shifter by - 30 °, the second sync a chronic detector, the second input of which is connected to the output of the receiver, the first subtractor and a phase shifter by - 90 °, the output of which is connected to the second input of the second subtractor, a phase shifter by + 30 ° connected in series to the output of the reference voltage extraction unit, and a third synchronous detector, the second input which is connected to the output of the receiver, and the output is connected to the second input of the first subtractor, differs from the closest analogue in that it is equipped with a synchronizer, a second pseudo-random sequence generator and a carrier frequency synthesizer, and a second pseudo-random sequence generator and a carrier frequency synthesizer are connected to the synchronizer output, the output of which is connected to the second input of the first modulator.

The block diagram of the transmitting part of the coherent radio link is shown in Fig. 1 and 2. The block diagram of the receiving part of the coherent radio link is shown in FIG. 3. A fragment of the time-frequency matrix of the used PSK signals with frequency hopping is shown in FIG. 4.

The transmitting part of the coherent radio link contains serially connected source 1 of discrete messages, encoder 2, digital scrambler 26, first modulator 3, first transmitter 5 (power amplifier) and first transmitting antenna 6, serially connected synchronizer 28, second generator 29 of a pseudo-random sequence (PSP) and a carrier frequency synthesizer 30, the output of which is connected to the second input of the first modulator 3, the first pseudo-random sequence generator 7, the second modulator 8, the second input of which is connected to the output of the second high frequency generator 9, the second transmitter 10 and the second transmitting antenna 11 are connected in series.

The receiving part of the coherent radio link contains a serially connected receiving antenna 12, a receiver 13 (high frequency amplifier), a first synchronous detector 14, a second subtractor 23, a digital descrambler 27, a decoding device 24 and a block 25 for recording and analyzing messages, which are serially connected to the output of the reference extraction unit 16. voltage phase shifter 17 by - 30 °, the second synchronous detector 19, the second input of which is connected to the output of the receiver 13, the first subtractor 21 and the phase shifter 22 by + 90 °, the output of which is connected to the second input of the second subtractor 23, connected in series to the output of the selection unit 16 reference voltage phase shifter 18 by + 30 ° and the third synchronous detector 20, the second input of which is connected to the output of the receiver 13, and the output is connected to the second input of the first subtractor 21, serially connected to the output of the receiver 13, a frequency search unit 15 and a reference voltage extraction unit 16 , the second input of which is connected to the output of the receiver 13, and the output is connected to the second input of the first synchronous detector 14.

Coherent radio link works as follows.

Discrete messages from the output of source 1 through the encoder 2 are fed to the input of the digital scrambler 26, which implements a cryptographic method for protecting discrete messages from unauthorized access by unauthorized persons. This method includes encryption, encoding and transformation of messages, as a result of which their content becomes inaccessible without presenting the cryptogram key and reverse transformation.

With the digital method of closing consecutive messages, four main groups are conditionally distinguished:

1) substitution - symbols of discrete messages are replaced by other symbols in accordance with a predefined rule;

2) permutation - symbols of discrete messages are permuted according to a certain rule within a given block of transmitted discrete messages;

3) analytical transformation - encrypted messages are transformed according to some analytical rule;

4) combined transformation - the original discrete messages are encrypted with two or more encryption methods.

Scrambled discrete messages in the form of a modulating code M (t) from the output of the digital scrambler 26 are fed to the first input of the modulator, the synchronizer 28 turns on the second generator 29 of the pseudo-random sequence, which, in turn, controls the operation of the synthesizer 30 of carrier frequencies, at the output of which sequentially in time, a grid of high-frequency oscillations of various carrier frequencies is formed:

u ₁ (t) = U ₁ cos (ω ₁ t + ϕ ₁ ),

u ₂ (t) = U ₂ cos (ω ₂ t + ϕ ₂ ),

……………………….

u _i (t) = U _i cos (ω _i t + ϕ _i ),

……………………….

T_c=M*t_c,u _m (t) = U _m cos (ω _m t + ϕ _m ), 0

T _c = M * t _c ,

where U _i. , ω _i , ϕ _i , T _c - amplitudes, carrier frequencies, initial phases and duration of high-frequency oscillations;

i = 1,2,…, M, M = ∆ω _c / ∆ω ₁ ,

M - the number of used carrier frequencies (number of frequency channels),

∆ω _c is the bandwidth of the spread spectrum of the signal used (Fig. 4);

∆ω ₁ - bandwidth of one frequency channel;

t _c - time interval between frequency switching, characterizes the operating time at one carrier frequency.

Depending on the ratio of the operating time at one frequency t _c and the duration of information symbols (messages) τ _{e, the} frequency hopping can be divided: into intersymbol, per-symbol and intra-symbol.

With an intersymbol frequency hopping, n information symbols (n≥2) are transmitted at one frequency, while t _c = n * τ _e .

As an example, Fig. 4 shows a fragment of the time-frequency matrix of a complex PSK signal with frequency hopping. In this case, n was chosen equal to 4

(t _c = 4τ _e ), squares with different oblique shading denote different information symbols (messages) with different phases (0, π).

The generated high-frequency oscillations are sequentially in time fed to the second input of the first modulator 3.

At the output of the first modulator 3, a complex phase-shift keying (PSK) signal with a frequency hopping is generated

u _ci (t) = U _i cos [ω _i t + ϕ _k (t) + ϕ _i ], 0≤t≤ t _c ,

where ϕ _k (t) = {0, π} is the manipulated phase component reflecting the phase manipulation law in accordance with the modulating code M (t), and ϕ _k (t) = const for kτ _e <t <(k + 1 ) τ _e and can change abruptly at

t = kτ _e , i.e. at the boundaries between elementary symbols (parcels) (k = 1, 2, ... N-1);

τ _e , N - the duration and the number of elementary messages, from which the signal with the duration T _c is composed (T _c = Nτ _e ).

This signal, after being amplified in the transmitter 5 (power amplifier), is emitted by the transmitting antenna 6 with a directional radiation pattern towards the receiving part of the coherent radio link.

The pseudo-random sequence (PSP) from the output of the generator 7 is fed to the first input of the modulator 8, to the second input of which a high-frequency oscillation is supplied from the output of the high-frequency generator 9.

u _w (t) = U _w cos (ω _w t + ϕ _w ), 0

where ω _w - ω _c = ∆ω ≤ ∆ω _d , ∆ω _d is the passband of synchronous detectors 14, 19 and 20.

A noise-like signal (NLS) is formed at the output of the modulator 8

u ₂ (t) = U _w cos [ω _w t + ϕ _w (t) + ϕ _w ], 0

where ϕ _w (t) = {0, π} is the manipulated phase component that reflects the phase manipulation law in accordance with the PSP.

The specified signal after amplification in the transmitter 10 (power amplifier) is emitted by the transmitting antenna 11 with a directional radiation pattern towards the receiving part of the coherent radio link. The power of this signal is much greater than the power of the information signal, for which it creates a noise blanket.

Mixture of PSK signal with frequency hopping u _ci (t) and NLS signal u ₂ (t)

u _∑ (t) = u _ci (t) + u ₂ (t)

from the output of the receiving antenna 12 through the receiver 13 (high frequency amplifier) is simultaneously fed to the first (information) inputs of the synchronous detectors 14, 19 and 20, to the second inputs of which reference voltages are supplied, respectively, from the output of the block 16 for selecting the reference voltage directly and through the phase shifter 17 and 18 at - 30 ° and + 30 °:

u ₀₁ (t) = U ₀ cos (ω _i t + ϕ _i ),

u ₀₂ (t) = U ₀ cos (ω _i t + ϕ _i - 30 °),

u ₀₃ (t) = U ₀ cos (ω _i t + ϕ _i + 30 °).

At the output of synchronous detectors 14, 19 and 20, the following low-frequency voltages are allocated, respectively:

u _n1 (t) = U _n1 cosϕ _k (t) + U _n2. cos [(ω _w - ω _i ) t + ϕ _w (t) + ϕ _w - ϕ _i ],

u _n2 (t) = U _n1 cos [ϕ _to (t) + 30 °] + U _n2. cos [(ω _w - ω _i ) t + ϕ _w (t) + ϕ _w - ϕ _i + 30 °],

u _n3 (t) = U _n1 cos [ϕ _to (t) - 30 °] + U _n2. cos [(ω _w - ω _i ) t + ϕ _w (t) + ϕ _w - ϕ _i - 30 °],

U_i U₀; U_н2 =

U_ш U₀.where U _n1 =

U _i U ₀ ; U _n2 =

U _w U ₀ .

A difference voltage is generated at the output of the subtractor 21

∆ u _n1 (t) = u _n2 (t) - u _n3 (t) = U _n2 sin [(ω _w - ω _i ) t + ϕ _w (t) + ϕ _w - ϕ _i ],

which is the NLS signal and differs from the NLS signal at the output of the synchronous detector 14 by phase rotation by + 90 ° _.

The difference voltage ∆ u _h1 (t) from the output of the subtractor 21 is fed to the input of the phase shifter 22 by + 90 °, at the output of which a difference voltage is formed

∆u _n2 (t) = U _n2 sin [(ω _w -ω _i ) t + ϕ _w (t) + ϕ _w -ϕ _i + 90 °] = U _n2 cos [(ω _w -ω _i ) t + ϕ _w (t) + ϕ _w -ϕ _i ].

This voltage is fed to the second input of the subtractor 23, at the output of which a difference voltage is formed

∆ u _n3 (t) = ∆u _n2 (t) - ∆u _n3 (t) = U _n1 cosϕ _k (t),

which is an analogue of the transmitted message. Voltage

∆ u _n3 (t) from the output of the subtractor 23 is fed to the input of the digital descrambler 27, the principle of operation of which corresponds to the principle of operation of the digital scrambler 26, but has the opposite character. At the output of the descrambler 27, code information is formed, which is fed to the input of the decoding device 24, at the output of which the initial information of the source 1 of discrete messages is formed, which is fed to the input of the unit 25 for registration and analysis of messages.

A coherent radio link under the cover of a powerful noise curtain can successfully perform its functions. At the same time, the possibility of unauthorized access by unauthorized persons to confidential information, which is transmitted over a coherent radio link, is significantly reduced, since the noise curtain signal hides the information signal due to the energy excess of this signal by the noise-like curtain signal in a given frequency range.

In addition, complex phase modulated signals have high energy and structural secrecy in terms of detection.

Energy secrecy of these signals is due to their high compressibility in time and in the spectrum with optimal processing, which makes it possible to reduce the instantaneous radiated power. As a result, the complex PSK signal at the receiving point is masked not only by noise-like signals, but also by noise and interference. Moreover, the energy of a complex information signal is by no means small, it is simply distributed over the time-frequency domain so that at each point of this area the signal power is less than the power of noise and interference.

Structural secrecy of complex PSK signals is due to a wide variety of their shapes and significant ranges of parameter changes, which makes it difficult to optimally or albeit quasi-optimal processing of complex PSK signals of an a priori unknown structure in order to increase the receiver sensitivity. Complex PSK signals make it possible to apply a new type of selection - structural selection.

Cryptographic protection of confidential discrete information from unauthorized access by unauthorized persons is provided by special methods of encryption, encoding and transformation of confidential discrete information, as a result of which its content becomes inaccessible without the presentation of the cryptogram key and reverse transformation.

Thus, the proposed coherent radio link, in comparison with the prototype and other technical solutions for a similar purpose, provides not only noise, energy, structural and cryptographic protection, but also the protection of confidential discrete information from unauthorized access by unauthorized persons through the use of complex signals with phase shift keying (PSK) and PPRCH.

The strategy of protection against unauthorized access by unauthorized persons is to "escape" signals of a coherent radio link by tuning the operating frequency according to a pseudo-random law. Therefore, in the proposed coherent radio link, an important characteristic is the actual operating time at one frequency t _c . The shorter this time, the higher the likelihood that complex PSK signals with frequency hopping will not be affected by unauthorized persons.

Consequently, the functionality of the known coherent radio link is expanded, and the reliability of protecting confidential discrete information from unauthorized access by unauthorized persons is increased.

Authors: Dikarev Viktor Ivanovich

Parfenov Nikolay Petrovich

Alekseev Sergey Alekseevich

Stakhno Roman Evgenievich

Claims (1)

A coherent radio link containing on the transmitting side a sequentially connected source of discrete messages, an encoder, a digital scrambler, a first modulator, a first transmitter and a first transmitting antenna connected in series with a first pseudo-random sequence generator, a second modulator, the second input of which is connected to the output of the second high frequency generator, a second transmitter and a second transmitting antenna, and on the receiving side a receiving antenna, a receiver, a first synchronous detector, a second subtractor, a digital descrambler, a decoding device and a message registration and analysis unit, connected in series to the receiver output, a frequency search unit and a reference selection unit voltage, the second input of which is connected to the output of the receiver, and the output is connected to the second input of the first synchronous detector, serially connected to the output of the reference voltage extraction unit, a phase shifter by - 30 °, a second synchronous detector a torus, the second input of which is connected to the output of the receiver, the first subtractor and a + 90 ° phase shifter, the output of which is connected to the second output of the second subtractor, connected in series to the output of the reference voltage extraction unit, a phase shifter by + 30 ° and a third synchronous detector, the second input of which is connected with the output of the receiver, and the output is connected to the second input of the first subtractor, characterized in that it is equipped with a synchronizer, a second pseudo-random sequence generator and a carrier frequency synthesizer, and a second pseudo-random sequence generator and a carrier frequency synthesizer are connected to the synchronizer output, the output of which is connected to the second the input of the first modulator.

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