RU2731681C1 - Method of forming noise-like phase-shift keyed signals - Google Patents

Abstract

FIELD: radio engineering and communication.

SUBSTANCE: method of generating noise-like phase-shift keyed signals involves generation of two binary quasi-orthogonal pseudo-random sequences of maximum length: synchronizing (SS) and information (IS). At each repetition period of IS, modulated PRS (MS) is formed by cyclic shift of IS of initial length by number of elements, determined by transmitted information symbol, and additionally modulo two addition with another bit of information. IS and MS are shortened or elongated by one element. MS and delayed by several cycles SS are summed by modulo two. Result of addition is summed majority with SS and IS, and phase shift keying of the carrier frequency signal carry out by received signal. Phase-shift keyed signal is additionally shifted in phase by 0 degrees or 90 degrees with a signal generated by modulo two addition of SS and IS. SS periodically phased with IS. MS and IS are preferably M-sequences which form a Gold sequence.

EFFECT: invention can be used in radio communication systems with noise-like signals to increase their noise immunity and reconnaissance immunity.

1 cl, 1 dwg

Description

The invention relates to the field of radio engineering and can be used in radio communication systems with noise-like signals to increase their noise immunity and intelligence protection.

The use of noise-like signals ensures high noise immunity of radio communication systems to the effects of a number of interference created by means of electronic suppression (REP). These include, for example, sighting and barrage interference [1, p.16]. To disrupt radio communications, the power of such interference should be one to two orders of magnitude higher than the power of the transmitted signal.

At the same time, imitating interference, used by means of electronic warfare [1, p. 14], can disrupt radio communication with the power of the interference signal, commensurate with the power of the transmitted signal.

Consider the impact of simulated interference on radio communication systems using noise-like signals. To synchronize the receiver with the transmitter, as a rule, continuously transmitted synchronizing noise-like signals are used [2]. They represent a carrier signal phase-keyed with a periodic binary pseudo-random sequence (PS). Simulated interference contains the same timing signal, but with a time-varying delay relative to the transmitted signal. As a result, the SP noise and signal periodically coincide. The scheme for tracking the delay of the SP in the receiving device (SS3), also called the automatic time control (APT) scheme [3, p.302], at such moments of time can switch to tracking the delay of the SP of the interference and become out of sync with the transmitter. The probability of such an event is the lower, the lower the frequency of coincidences of the SP of the interference and the signal, which, in turn, decreases with an increase in the duration of the repetition period of the SP.

Hence, it follows that in order to increase the noise immunity of the radio communication system to simulating interference, it is necessary to increase the repetition period of the SP. But since the SP is also used for signal detection [2], an increase in the repetition period, and, consequently, the number of SP elements, inevitably leads to an increase in the signal search time. In turn, the signal search time is limited by the requirement for information transmission delay.

The object of the invention is to reduce the likelihood of loss of synchronization when exposed to imitating interference without significantly increasing the signal search time. The result achieved when using the invention is an increase in noise immunity and intelligence protection of the radio communication system.

The closest in terms of the number of coinciding features to the claimed method is the method of forming noise-like phase-shift keyed signals, described in [4].

According to this method, carrier and clock signals are generated, quasi-orthogonal or orthogonal pseudo-random sequences are formed from the clock signal, one of which is intended for synchronization (SP), and the second is for information transmission (IP). The sequences are phased with each other, after which the IP is cyclically shifted relative to the SP by the number of elements determined by the digital data coming from the information source for a time equal to the period of the pseudo-random sequences. The cyclically shifted IP sequence is added modulo two with an additional bit of information and the carrier signal is phase-keyed. A second carrier signal is generated, which is phase-shifted by 90 degrees relative to the first, which is phase-keyed by the SP sequence and added to the keyed first carrier signal.

The disadvantage of the prototype method is that the generated signals do not provide high noise immunity of the radio communication system when exposed to imitating interference.

To solve the problem posed in the invention in the method of forming noise-like phase-shift keyed signals, which consists in the fact that signals of the carrier and clock frequencies are generated, binary quasi-orthogonal pseudo-random sequences (PSP) of the maximum length are formed from the clock signal, phased among themselves, synchronizing and informational, on each the repetition period of the information PSP, modulated PSP is formed by cyclically shifting the information PSP by the number of elements determined by the transmitted information symbol, and additional addition modulo two with one more bit of information, according to the invention, the modulated PSP is summed modulo two with a clock frequency delayed by an integer number of periods synchronizing PSP, and the result is majority-summed with the synchronizing PSP and information PSP, the received binary sequence is phase-shift keyed of the carrier signal, and the phase-shift keyed signal of the complementary but are shifted in phase by zero or ninety degrees by a sequence, which is formed by adding modulo two synchronizing PSP and information PSP, while the information PSP and modulated PSP are shortened or lengthened by one element, and phasing of the synchronizing PSP with information PSP is carried out periodically with a period equal to the product of the number of elements of the synchronizing PSP, the number of elements of the information PSP and the duration of the clock frequency period.

The method for generating noise-like signals consists in sequentially performing the following operations:

- Generate carrier and clock signals.

- From the clock signal, binary quasi-orthogonal PSPs are formed, synchronizing and informational, and the synchronizing PSP is an M-sequence, and the information PSP is also an M-sequence, but shortened or lengthened by one element.

- Periodically, with a period equal to the product of the number of elements of the synchronizing PSP, the number of elements of the information PSP and the duration of the clock frequency period, the synchronizing PSP is phased with the information PSP, that is, the PSP generators are set to the initial fixed states.

- At each repetition period of the information PSP, a modulated PSP is formed by cyclic shifting the information PSP with an unchanged length by the number of elements determined by the transmitted information symbol, and additionally adding modulo two with one more bit of information.

- The modulated PSP and the synchronizing PSP delayed by an integer number of clock periods are summed modulo two, and the result is majority-summed with the synchronizing PSP and the information PSP. Majority addition of logical signals is understood as the operation of calculating the majority function "two out of three".

- The received binary sequence is phase-manipulated carrier signal.

- The synchronizing PSP and the information PSP are summed modulo two, and an additional phase shift of the phase-shift keyed signal by zero or ninety degrees is carried out with the resulting binary sequence.

An example of the technical implementation of a signal conditioning device according to the claimed method is shown in FIG. 1. The device contains:

1 - carrier and clock frequency signal generator (LPTCH);

;2 - frequency divider by

;

3, 4 - generator of information PSP (generator of IP);

5 - parallel register;

;6 - frequency divider

;

7 - adder modulo two;

8 - generator of synchronizing PSP (SP generator);

9, 10 - adder modulo two;

11 - majority element;

12 - multiplier;

13 - switch;

14 - 90 ° phase shifter.

2, генератора СП 8, генераторов ИП 3 и 4. Делитель частоты на

2 формирует импульсы длительностью, равной одному периоду

тактовой частоты, и с периодом повторения

равным

периодам тактовой частоты. Эти импульсы поступают на входы разрешения начальной установки генератора ИП 3 и генератора ИП 4, а также тактовые входы параллельного регистра 5 и делителя частоты на

6. В результате генератор ИП 3 формирует периодически повторяющуюся информационную ПСП с количеством элементов равным

. Делитель частоты на

6, где

равно

или

, формирует импульсы длительностью

и с периодом повторения

которые поступают на вход разрешения начальной установки генератора СП 8.The device works as follows. The clock signal generated by the LPTF 1 is fed to the clock inputs of the frequency divider at

2, generator SP 8, generators IP 3 and 4. Frequency divider on

2 generates pulses with a duration equal to one period

clock frequency, and with a repetition period

equal

clock periods. These pulses are fed to the enable inputs of the initial setting of the IP generator 3 and the generator IP 4, as well as the clock inputs of the parallel register 5 and the frequency divider by

6. As a result, the IP generator 3 generates a periodically repeating information PSP with the number of elements equal to

... Frequency divider by

6 where

equally

or

, generates pulses with a duration

and with a repetition period

which go to the permission input of the initial setting of the SP 8 generator.

очередным фронтом тактовых импульсов происходит запись кода начальной установки в регистр. В дальнейшем, работая в режиме регистра сдвига, он формирует линейную рекуррентную последовательность.As generators of PSP 3, 4 and 8, generators of linear recurrent sequences are used, made on the basis of universal registers with an adder modulo two in the feedback loop of the output with the input. The inputs of the initial setting of the generators are the inputs of parallel register writing. The generator clock input is the register clock input, and the initial setting enable input is the parallel register write mode selection input. Upon arrival at the enable input of the initial setting of a pulse with a duration

the next edge of clock pulses writes the initial setting code to the register. Later, working in the shift register mode, it forms a linear recurrent sequence.

At the inputs of the initial setting of the generator SP 3 and the generator SP 8 fixed binary codes are installed, which are not shown in Fig. 1. At the inputs of the initial setting of the generator IP 4, the code of the transmitted information symbol is received from the outputs of the parallel register 5. Thus, different information symbols correspond to different cyclic shifts of the information PSP generated by the PS generator 4 relative to the information PSP generated by the PS generator 3. The transmitted information in the form of multi-bit binary words are fed to the inputs of the parallel register 5, where it is recorded by the pulses of permission of the initial setting of the generator IP 3 and generator 4. One bit of information from the output of register 5 is fed to the input of the adder modulo two 7, in which it is added to the cyclically shifted information PSP generated by the generator SP 4. The modulated PSP from the output of the adder modulo two 7 is fed to the input of the adder modulo two 9, in which it is added to the synchronizing PSP coming from the output of one of the bits of the SP generator register 8. The output signal of the adder modulo two 9 is fed to one of the inputs in major element 11, the other two inputs of which are fed: synchronizing PSP from the output of the generator SP 8 and information PSP from the output of the generator IP 3. At the output of the majority element 11, a signal with a logic-one level is generated only if there are two or three signals at its input with a level logical unit. The output signal of the majority element is fed to one of the inputs of the multiplier 12, to the second input of which the carrier signal is fed from the output of the low-pass filter 1. At the output of the multiplier, a phase-shift keyed signal is formed, which is fed to one of the inputs of the switch 13 directly, and to the second input after phase shift by 90 degrees in the phase shifter 14. The switch 13 is controlled by the signal obtained as a result of the addition in the modulo two adder 10 of the information PSP from the output of the PS generator 3 and the synchronizing PSP from the output of the SP generator 8. At the output of the switch 13, the output signal of the shaper is formed, which is noise-like signal with quadrature phase shift keying.

In order to ensure a low level of cross-correlation of the synchronizing bandwidth and information bandwidth for their formation, it is advisable to choose M-sequences that form the Gold sequence [3, p. 119].

6 обеспечивает начальную установку генератора СП 8 каждые

периодов формируемой ПСП. В тот же момент времени происходит начальная установка генератора ИП 3, тем самым осуществляется фазирование информационной ПСП и синхронизирующей ПСП. Так как число элементов информационной ПСП на единицу больше или меньше числа элементов синхронизирующей ПСП, формируемой генератором СП 8, через каждый период синхронизирующей ПСП происходит сдвиг на один элемент информационной ПСП относительно синхронизирующей ПСП и меняется их сумма по модулю два. Поэтому последовательность на выходе сумматора по модулю два 10 является периодической с числом элементов, равным

It should be noted that the PS generator 8, which forms a sequence of maximum length, does not require an initial setting in each period of the formation of the PSP. Output signal of the frequency divider

6 provides the initial installation of the SP 8 generator every

periods of the generated bandwidth. At the same moment in time, the initial installation of the IP generator 3 occurs, thereby phasing the information PSP and synchronizing PSP. Since the number of elements of the information PSP is by one more or less than the number of elements of the synchronizing PSP generated by the SP generator 8, after each period of the synchronizing PSP there is a shift by one element of the information PSP relative to the synchronizing PSP and their sum modulo two changes. Therefore, the sequence at the output of the adder modulo two 10 is periodic with the number of elements equal to

To prove the achieved positive result in the claimed method, consider the mathematical representation of the generated signal:

– амплитуда сигнала;Where

- signal amplitude;

– несущая частота;

- carrier frequency;

– синхронизирующая ПСП;

- synchronizing bandwidth;

– информационная ПСП;

- informational PSP;

– модулированная ПСП;

- modulated PSP;

– модулированная ПСП, сложенная по модулю два с задержанной на n тактов синхронизирующей ПСП;

- modulated PSP, added modulo two with a synchronizing PSP delayed by n clock cycles;

– мажоритарная сумма трех логических переменных.

- the majority sum of three logical variables.

можно доказать тождествоBy iterating over the values of variables

one can prove the identity

Using this ratio, the generated signal can be represented as

Thus, it is the sum of the following signals:

- carrier signal, phase-keyed by the synchronizing PSP;

- carrier signal, keyed by the phase of the information PSP;

- carrier signal, phase-shifted by 90 degrees and keyed in phase of modulated PSP and delayed synchronizing PSP;

- a carrier signal, phase-shifted by 90 degrees and phase-keyed by the synchronizing PSP, the information PSP, modulated PSP and the delayed synchronizing PSP.

Due to the quasi-orthogonality of the synchronizing PSP and information PSP, all four signals are weakly correlated with each other and can be processed separately by correlation methods.

Thus, in the receiving device, a separate search for the synchronizing PSP and information PSP can be implemented, after detecting which, the carrier and clock frequencies are automatically tuned and information is received. Since the information bandwidth has practically the same number of elements as the synchronizing bandwidth, the search time is only doubled.

To protect against imitating interference, tracking the delay of the received signal in the receiver (automatic time control) [3, p. 302] should be based on the estimates of the delays of both the received synchronizing bandwidth and the received information bandwidth relative to the bandwidth generated in the receiver. At the same time, of these two estimates, it is necessary to choose the minimum in absolute value. If the delay of the simulating interference is such that the delay of the synchronizing PRP coincided with the delay of the synchronizing PRP of the received signal, then after they begin to differ by some part of the duration of the PRP element, the delay tracking circuit will automatically switch to work with an estimate of the informational PRP delay of the received signal having smaller value in absolute value.

Similarly, if the delay of the informational PRP of the simulating interference coincides with the delay of the informational PRP of the received signal, after some time the delay tracking circuit will switch to work with the estimation of the delay of the synchronizing PRP of the received signal.

выходной последовательности сумматора по модулю два 10. Вероятность такого события, а следовательно и вероятность срыва синхронизации, обратно пропорциональна

. По сравнению со способом-прототипом, при одинаковой длительности периода повторения синхронизирующей ПСП вероятность срыва синхронизации уменьшается в число раз, равное отношению

к длительности периода повторения синхронизирующей ПСП

, то есть в

раз. Например, при

вероятность уменьшается более чем в тысячу раз. Only in the case when the delays of the synchronizing PSP and information PSP of the simulating interference and the received signal coincide, errors in the reception of information and synchronization may occur. This occurs when the delay of the simulated interference relative to the received signal is an integer number of periods

the output sequence of the adder modulo two 10. The probability of such an event, and hence the probability of synchronization failure, is inversely proportional to

... Compared with the prototype method, with the same duration of the repetition period of the synchronizing PSP, the probability of synchronization failure decreases by a number of times equal to the ratio

to the duration of the repetition period of the synchronizing PSP

, that is in

time. For example, for

the probability decreases more than a thousand times.

с последовательностями, образованными всеми возможными циклическими сдвигами информационной ПСП, и определения циклического сдвига с максимальным по абсолютной величине значением взаимной корреляции. По значению циклического сдвига определяют передаваемый информационный символ, а по знаку соответствующего значения взаимной корреляции определяют значение еще одного бита информации. Можно показать, что для получения наибольшего отношения сигнал/шум принимаемый сигнал необходимо предварительно обнулить на интервалах времени совпадений значений синхронизирующей ПСП и информационной ПСП, то есть умножить на сигнал

, так как в эти моменты времени фаза сигнала зависит только от значения синхронизирующей ПСП. При одинаковой мощности принимаемого сигнала соотношение сигнал/шум для максимального по абсолютной величине значения взаимной корреляции такое же, как в способе-прототипе. Кроме того, применение при формировании сигнала нелинейной мажоритарной функции значительно повышает криптостойкость сигнала, а следовательно – разведзащищенности системы радиосвязи.Reception of information with the claimed method of signal shaping can be carried out in the same way as in the prototype method. Namely, by calculating the cross-correlation value of the received signal multiplied by

with the sequences formed by all possible cyclic shifts of the information PRS, and determining the cyclic shift with the maximum value of cross-correlation in absolute value. The transmitted information symbol is determined from the cyclic shift value, and the value of one more bit of information is determined from the sign of the corresponding cross-correlation value. It can be shown that in order to obtain the highest signal-to-noise ratio, the received signal must first be zeroed at time intervals of coincidence of the values of the synchronizing bandwidth and information bandwidth, that is, multiply by the signal

, since at these moments of time the phase of the signal depends only on the value of the synchronizing PSP. With the same power of the received signal, the signal-to-noise ratio for the maximum absolute value of the cross-correlation is the same as in the prototype method. In addition, the use of a nonlinear majority function in signal generation significantly increases the cryptographic strength of the signal, and, consequently, the intelligence protection of the radio communication system.

SOURCES OF INFORMATION

1. Military-technical training. Military-technical foundations of building electronic means and complexes: textbook / A.S. Osipov; under scientific. ed. E.N. Garina. - Krasnoyarsk: Sib. Feder. un-t, 2013 .-- 344p.

2. Patent RU 2115 236 C1. Communication system with broadband signals. Published on July 10, 1998.

3. Varakin L.E. Communication systems with noise-like signals. - M .: Radio and communication, 1985. - 384p.

4. Patent RU 2279 183 C2. A method for transmitting information in a communication system with broadband signals. Published on June 27, 2006. Bul. No. 18.

Claims (2)

1. A method of generating noise-like phase-shift keyed signals, which consists in the fact that signals of the carrier and clock frequencies are generated, binary quasi-orthogonal pseudo-random sequences (PSP) of the maximum length are formed from the clock signal, phase-phased among themselves, synchronizing and informational, at each repetition period of the information PSP, modulated PSP by cyclically shifting the information PSP by the number of elements determined by the transmitted information symbol, and additional addition modulo two with one more bit of information, characterized in that the modulated PSP is summed modulo two with a clock frequency delayed by an integer number of periods of the synchronizing PSP, and the result is majority-summed with the synchronizing PSP and the information PSP, the resulting binary sequence is phase-shift keyed on the carrier signal, and the phase-shift keyed signal is additionally shifted in phase by zero or ninety gram dus sequence, which is formed by adding modulo two synchronizing PSP and information PSP, while the information PSP and the modulated PSP are shortened or lengthened by one element, and the synchronizing PSP is phased with the information PSP periodically with a period equal to the product of the number of elements of the synchronizing PSP, the number of elements informational bandwidth and duration of the clock frequency period. 2. The method according to claim 1, characterized in that the maximum length sequences forming the Gold sequence are selected as the information PRS and the synchronizing PRS.

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