RU2734230C1 - Method of forming noise-like phase-shift keyed signals - Google Patents

Abstract

FIELD: radio equipment.

SUBSTANCE: invention relates to radio engineering and can be used in radio systems with noise-like signals. This method consists in generating binary quasi-orthogonal pseudo-random sequences, synchronizing, additional and information sequences. Number of information PRS elements is selected as product of mutually prime numbers, one of which is equal to number of synchronizing PRS elements, and second – to number of additional PRS elements. All three PRSs are phased to each other by one information PRS period. At each synchronizing PRS period, modulated PRS is formed by shifting the information PRS by the number of elements determined by the transmitted information symbol, and additionally addition modulo two with another bit of information. Synchronizing, additional and modulated PRS are summed up in a majority manner, and the obtained binary sequence is followed by phase shift keying of the carrier frequency signal.

EFFECT: high noise-immunity and reconnaissance protection when exposed to imitating interference.

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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 (CC3), 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 desynchronize 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 follows the obvious conclusion: 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 frequency 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 frequency 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) are formed from the clock signal, phased among themselves, synchronizing and information, form modulated PSP by the shift of 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, an additional PSP, quasi-orthogonal synchronizing PSP and information PSP are formed from the clock signal, the additional PSP, which synchronizes the PSP, is majority-summed modulated PSP, and the obtained binary sequence is phase-shift keyed of the carrier signal, while the number of additional PSP elements is chosen to be mutually prime with the number of elements of the synchronizing PSP, and the number of elements of the information PSP is selected equal to the product of the number of elements of the synchronizing PSP and the number of elements of the additional PSP, the modulated PSP is formed at each repetition period of the synchronizing PSP, and the phasing of the additional PSP, the synchronizing PSP and the information PSP is performed once at each repetition period of the information PSP.

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

- Generate carrier and clock signals.

- Synchronizing PSP, additional PSP and information PSP are formed from the clock frequency signal, and the number of elements of the synchronizing PSP and additional PSP are mutually prime numbers, and the number of elements of information PSP is equal to the product of these numbers.

- Once at each repetition period of the information PSP, all three PSPs are phased, that is, the PSP generators are set to the initial fixed states.

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

- Perform the operation of the majority addition of the synchronizing PSP, additional PSP and modulated 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.

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 - generator of synchronizing PSP (SP generator);

4 - adder modulo two;

5 - shift register;

;6 - frequency divider

;

7 - multiplexer;

8 - parallel register;

;9 - frequency divider

;

10 - additional PSP generator (DP generator);

11 - adder modulo two;

12 - majority element;

13 is a multiplier.

2, делителя частоты на

9, генератора синхронизирующей ПСП 3, генератора дополнительной ПСП 10 и регистра сдвига 5. Делитель частоты на

2 формирует импульсы длительностью, равной одному периоду

тактовой частоты

и с периодом повторения

, равным

периодам тактовой частоты (фиг. 2а). Эти импульсы подаются на тактовые входы делителя частоты на

6 и параллельного регистра 8, а также осуществляют фазирование (установку в начальное состояние) генератора СП 3. В результате генератор СП 3 формирует периодически повторяющуюся синхронизирующую ПСП с количеством элементов, равным

.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, frequency divider by

9, generator of synchronizing PSP 3, generator of additional PSP 10 and shift register 5. Frequency divider by

2 generates pulses with a duration equal to one period

clock frequency

and with a repetition period

equal to

periods of the clock frequency (Fig. 2a). These pulses are fed to the clock inputs of the frequency divider at

6 and parallel register 8, and also carry out phasing (setting to the initial state) of the SP generator 3. As a result, the SP 3 generator forms a periodically repeating synchronizing PSP with the number of elements equal to

...

9, где число

взаимно простое с числом

, формирует импульсы длительностью

и с периодом повторения

(фиг.2б). Эти импульсы осуществляют фазирование (установку в начальное состояние) генератора ДП 10. В результате генератор ДП 10 формирует периодически повторяющуюся дополнительную ПСП с количеством элементов, равным

. Для фазирования дополнительной ПСП с синхронизирующей ПСП выходные импульсы делителя частоты на

2 делятся по частоте в

раз в делителе частоты на

6. Полученные импульсы длительностью

и периодом повторения

(фиг. 2в) устанавливают делитель частоты на

9 в состояние, соответствующее появлению на его выходе импульса. Поскольку в этот же момент времени присутствует импульс на выходе делителя частоты на

2, происходит одновременное фазирование генератора СП 3 и генератора ДП 10. Этот процесс повторяется с периодом

.Frequency divider by

9, where the number

coprime with a number

, generates pulses with a duration

and with a repetition period

(Fig. 2b). These pulses carry out phasing (setting in the initial state) of the DP generator 10. As a result, the DP 10 generator generates a periodically repeating additional PSP with the number of elements equal to

... For phasing the additional PSP with the synchronizing PSP, the output pulses of the frequency divider by

2 divided by frequency in

times in the frequency divider by

6. Received pulses with duration

and the repetition period

(Fig.2c) set the frequency divider to

9 to the state corresponding to the appearance of a pulse at its output. Since at the same time there is a pulse at the output of the frequency divider by

2, there is a simultaneous phasing of the generator SP 3 and the generator DP 10. This process is repeated with a period

...

и

взаимно простые числа, последовательность, формируемая на выходе сумматора по модулю два 4, является периодической с периодом

и количеством элементов

.As the information PSP in this device, the PSP is used, obtained as a result of addition in the adder modulo two 4 additional PSP and delayed by a certain number of clock cycles of the synchronizing PSP. Because

and

coprime numbers, the sequence formed at the output of the adder modulo two 4 is periodic with a period

and the number of elements

...

2. Тем самым осуществляется привязка передачи информационных слов к периодам повторения синхронизирующей ПСП. С выходов параллельного регистра 8 одноразрядный символ информационного слова поступает на вход сумматора по модулю два 11, а многоразрядный символ поступает на управляющие входы мультиплексора 7, который подключает к своему выходу один из выходных сигналов регистра сдвига 5. Выходной сигнал мультиплексора 7 суммируется в сумматоре по модулю два 11 с одноразрядным информационным символом, образуя модулированную ПСП.The formation of the modulated PSP is carried out as follows. The information PSP from the output of the adder modulo two 4 is fed to the input of the shift register 5, at the outputs of which its shifted copies are formed. The transmitted information in the form of multi-bit binary words is fed to the inputs of the parallel register 8, where it is written in pulses from the output of the frequency divider to

2. Thus, the transmission of information words is linked to the repetition periods of the synchronizing PRS. From the outputs of the parallel register 8, the one-bit symbol of the information word is fed to the input of the adder modulo two 11, and the multi-bit symbol is fed to the control inputs of the multiplexer 7, which connects to its output one of the output signals of the shift register 5. The output signal of the multiplexer 7 is summed in the adder modulo two 11 with a one-bit information symbol, forming a modulated PSP.

The inputs of the majority element 12 receive: a synchronizing PSP from the output of the SP 3 generator, an additional PSP from the output of the DP 10 generator and modulated PSP from the output of the adder modulo two 11. At the output of the majority element 12, a signal with a logic-one level is generated only if it is present at its inputs two or three signals with a logic-one level. The output signal of the majority element 12 in the multiplier 13 is multiplied by the carrier frequency signal supplied to the second input of the multiplier 13 from the second output of the low-pass filter 1. As a result of the multiplication, a noise-like phase-shift keyed signal is formed.

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

where u is the signal amplitude;

ƒ - carrier frequency of the signal.

C (t) - synchronizing bandwidth;

A (t) - additional memory bandwidth;

M (t) - modulated PSP;

MS [a, b, c] is the majority sum of three logical variables.

By enumerating the values of the variables a, b, c, one can prove the identity

Using this ratio, the generated signal can be represented as

It can be seen from the obtained expression that the generated signal is the sum of three carrier frequency signals, phase-keyed by the synchronizing PSP, additional PSP, and modulated PSP. In addition, there is a fourth signal, which is the carrier signal, keyed in phase with each of these PRPs. Due to the quasi-orthogonality of the PSP, all four signals are weakly correlated with each other and can be processed separately by correlation methods.

Thus, a separate search for the sync PRP and the additional PRP can be implemented in the receiver. After detecting these signals, the informational memory bandwidth is automatically determined as the sum modulo two additional memory bandwidth and the synchronizing memory bandwidth delayed by an integer number of clock periods.

Thus, the signal search time is approximately doubled, and the repetition period of the information PSP is increased by K times.

However, if, in the prototype method, the repetition period of the information PSP is increased by a factor of K, the signal search time will increase significantly more than twice.

Let us compare the search time for the signal generated by the inventive method and the signal in the prototype method with the same period of the information PSP in terms of the number of operations required to calculate the convolutions of signals. If we consider modern methods for calculating convolutions of signals (correlation functions) based on the direct and inverse fast Fourier transform, then the number of multiplication operations required to implement the algorithm for searching for a signal generated by the claimed method is

and in the prototype method

If N and K differ insignificantly, then

For example, with K = 1023, the number of operations for a signal generated by the claimed method is reduced by more than a thousand times.

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 additional 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 delay of the additional PRP of the received signal, which has smaller value in absolute value.

Similarly, if the delay of the additional PRP of the simulating interference coincides with the delay of the additional PRP of the received signal, after a while the delay tracking circuit will switch to work with the estimation of the delay of the synchronizing PRP of the received signal.

раз. Например, при

вероятность уменьшается более чем в тысячу раз.Only in the case when the delays of the synchronizing bandwidths and additional bandwidths of the simulating interference and the received signal coincide, errors in the reception of information and a loss of synchronization are possible. This occurs when the delay of the simulated interference relative to the received signal is an integer number of data bandwidth periods. The probability of such an event, and hence the likelihood of a synchronization failure, is inversely proportional to the duration of the repetition period of the informational bandwidth. 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 of the durations of the repetition periods of the information PSP and the synchronizing PSP, that is, in

time. For example, for

the probability decreases more than a thousand times.

, так как в эти моменты времени фаза сигнала зависит только от 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 value of the cross-correlation of the received signal with the sequences formed by all possible cyclic shifts of the information PRS, and determining the cyclic shift with the maximum absolute value of the cross-correlation. 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 additional bandwidth, that is, multiply by the signal

, since at these moments of time the phase of the signal depends only on the synchronizing PRP. 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 for 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 (1)

A method for generating noise-like phase-shift keyed signals, which consists in generating signals of the carrier and clock frequencies, forming binary quasi-orthogonal pseudo-random sequences (PSP) from the clock signal, phased among themselves, synchronizing and informational, form modulated PSP by 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 an additional PSP is formed from the clock signal, a quasi-orthogonal synchronizing PSP and information PSP, the additional PSP, synchronizing the PSP and modulated PSP, is majority-summed, and the received binary sequence, phase shift keying of the carrier frequency signal is carried out, while the number of elements of the additional PSP is chosen to be mutually prime with the number of elements of the synchronizing PSP, and the number of elements of the information PSP is chosen equal to The th product of the number of elements of the synchronizing PSP and the number of elements of the additional PSP, the modulated PSP is formed at each repetition period of the synchronizing PSP, and the phasing of the additional PSP, the synchronizing PSP and the information PSP is performed once at each repetition period of the information PSP.

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