RU2778439C1 - Method for transmission of radio control commands with spread spectrum signals - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to the field of radio engineering. To achieve the effect, in the method for transmitting radio control commands by spread spectrum signals, at the beginning of the transmission of each control command, a clock signal generated by quadrature modulation of the carrier frequency signal with two binary pseudo-random sequences (PRS) is transmitted. The first PRS is an M-sequence, and the second PRS is formed from the M-sequence by adding one constant element. The duration of the clock signal is chosen as a multiple of the repetition period of the second PRS. When transmitting a radio control command, the value of the carrier frequency is changed according to a pseudo-random law at time intervals that are multiples of the repetition period of the second PRS. At each new value of the carrier frequency, the carrier frequency signal is first manipulated in phase of the first PR for one or more repetition periods of the second PR. For manipulation, a sequence is used that is the modulo two sum of the first PRS and the PRS obtained by cyclically shifting the M-sequence from which the second PRS is formed by the number of elements determined by the next transmitted information symbol of the radio control command, and adding one constant element.

EFFECT: increasing the noise immunity of the radio control system.

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Description

The invention relates to the field of radio engineering and can be used in radio control systems to improve their noise immunity.

The main task that has to be solved in the design of such systems is to reduce the transmission time of radio control commands while ensuring high reliability of their reception under the influence of both natural interference and interference from electronic countermeasures.

Among the known methods for improving the noise immunity of communication systems by expanding the spectrum of signals, the frequency hopping (FH) method and the direct sequence (DS) method are most widely used [1]. In the domestic literature, the signals generated by the DS method are called noise-like (broadband) phase-shift keyed signals (NPS). The methods of their formation and reception are well researched. They are the subject of a large number of scientific publications, for example [2], and patents [3, 4].

A comparison between the two methods of spreading the spectrum of signals (FH and DS) shows that the advantage of each of them in terms of noise immunity depends on the type of interference. For example, the DS method is more effective for impulse, narrowband and relay interference, and the FH method is more effective for barrage interference. Obviously, the combination of these methods makes it possible to increase the noise immunity in general.

Unlike the FH method, the information transfer rate when using the DS method can be significantly increased by using large ensembles of signals [5].

The aim of the invention is to increase the noise immunity of the radio control system with a short delivery time of commands through the use of noise-like phase-shift keyed signals with a program-tunable carrier frequency. The result achieved by using the invention is an increase in the noise immunity of the radio control system.

The closest in the number of matching features to the claimed method is the method of generating noise-like phase-shift keyed signals, described in [5].

According to this method, the following operations are performed in the transmitter:

- form carrier and clock signals;

- binary quasi-orthogonal PRS, synchronizing and informational, are formed from the clock signal, moreover, the synchronizing PRS is an M-sequence, and the informational PRS is also an M-sequence, but shortened or extended by one element;

- periodically (with a period equal to the product of the number of elements of the synchronizing SRP, the number of elements of the information SRP and the duration of the clock frequency period), the synchronizing SRP is phasing with the information SRP, that is, the SRP generators are set to the initial fixed states;

- at each repetition period of the information PSP, a modulated PSP is formed by cyclically shifting the information PSP with an unchanged length by the number of elements determined by the transmitted information symbol, and additional modulo two addition with one more bit of information, the resulting sequence, as well as the information PSP, shorten or lengthen by one element;

- Modulo two modulated SRP and synchronizing SRP delayed by an integer number of periods of the clock frequency are summed, and the result is majority summed with synchronizing SRP and information SRP (the majority addition of logical signals is understood as the operation of calculating the majority function two out of three);

- the received binary sequence is manipulated in phase by the carrier frequency signal;

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

The disadvantage of the prototype method is that in the generated signal, only half of its power is used for data transmission, which reduces the noise immunity of the radio communication system.

To solve the problem posed in the invention in the method of transmitting radio control commands with spread spectrum signals, which consists in the fact that carrier and clock signals are generated, binary pseudo-random sequences (PRS) of maximum length are formed from the clock signal, the synchronizing and information, information PSP is extended by one constant element and at each repetition period of the information PRP, a modulated PRP is formed by cyclically shifting the non-extended information PRP by the number of elements determined by the transmitted information symbol, and by adding one constant element, according to the invention, at the beginning of the transmission of each radio control command, the synchronizing PRP and the information PRP are phased with each other , and also transmit a sync signal, for the formation of which the synchronizing SRP and the information SRP are converted into bipolar signals, which perform quadrature modulation of the carrier frequency signal, and for a long time The frequency of the sync signal is selected as a multiple of the information PRP repetition period, and when transmitting a radio control command, the carrier frequency value is changed according to a pseudo-random law at time intervals that are multiples of the information PRP repetition period, with each new value of the carrier frequency, the carrier frequency signal is first manipulated in the phase of the synchronizing PRP for one or several repetition periods of the information SRP, and then for the manipulation use the sequence, which is obtained by modulo two addition of the synchronizing SRP and the modulated SRP.

The method of transmitting radio control commands with spread spectrum signals consists in sequentially performing the following operations:

- form carrier and clock signals;

- binary pseudo-random sequences (RRP) of maximum length are formed from the clock signal, the synchronizing and informational, informational RRP is extended by one constant element;

- at each repetition period of the information SRP, a modulated SRP is formed by cyclically shifting the non-extended information SRP by the number of elements determined by the transmitted information symbol, and adding one constant element .;

- before the transmission of each radio control command, the synchronizing PSP is phasing with the information PSP, that is, the generators (shapers) of the PSP are set to the initial fixed states;

- form a clock signal: for this, the synchronizing PSP and the information PSP are converted into bipolar signals, which carry out quadrature modulation of the carrier frequency signal;

- the clock signal is transmitted for a time equal to an integer number of repetition periods of the information PRP;

- when transmitting a radio control command, the value of the carrier frequency is changed according to a pseudo-random law at time intervals that are multiples of the repetition period of the information SRP, while the duration of the intervals can also change;

- at each new value of the carrier frequency for one or more repetition periods of the information SRP, the carrier frequency signal is manipulated in the phase of the synchronizing SRP; the need for such an operation is explained by the fact that in the transmitting and receiving devices, when the carrier frequency of the signal changes, transient processes occur during which reliable transmission of information is impossible; transmit synchronizing PSP;

- when transmitting information symbols of the radio control command, the carrier frequency signal is manipulated in phase by a sequence that is the modulo two sum of the synchronizing SRP and the modulated SRP. The modulo two addition of the modulated SRP and the synchronizing SRP makes it possible to obtain an ensemble of information signals that are weakly correlated with time shifts. In the absence of this operation, that is, the keying of the signal of the carrier frequency of the modulated SRP, in radio channels with multipath propagation of radio waves, the signals of different beams correspond to different transmitted information symbols. This leads to a decrease in the noise immunity of reception, since it becomes possible to select an information symbol corresponding not to the main receiving beam, but to one of the additional ones.

Consider the mathematical representation of the clock signal:

– амплитуда сигнала;where

is the signal amplitude;

– несущая частота;

– carrier frequency;

– синхронизирующая ПСП;

– synchronizing PSP;

– информационная ПСП.

- information PSP.

As can be seen, the clock signal is the sum of two carrier frequency signals shifted in phase by ninety degrees, one of which is manipulated in phase by a periodically repeating synchronizing PRP, and the second by a periodically repeating information PRP.

The receiver can implement a simultaneous search for the synchronizing PSP and the information PSP. In this case, if we use a detection algorithm based on a comparison with the threshold of the sum of squares of the maximum values of the cross-correlation functions of the received signal with the synchronizing PRP and the information PRP, the noise immunity of detection will be slightly lower than the noise immunity of detection when transmitting one synchronizing PRP.

After detecting the clock signal and autotuning the clock frequency of the PSP, the receiving device switches to the mode of searching for the end of the transmission of the clock signal.

Let's consider the algorithm of this search. At the beginning of the transmission of the clock signal, the synchronizing SRP and the information SRP are phased with each other. This means that the generators (shapers) of the synchronizing SRP and the information SRP are set to certain initial states. For example, if the generators are based on shift registers with modulo two adders in the feedback loop, the initial states are the binary codes written in the registers. If the shapers are made on the basis of counters and read-only memories, the initial states are the zero states of the counters. Let's consider this method of PSP formation. If the number of elements of the synchronizing PRS is N, then the counter of the generator of the synchronizing PRS counts clock pulses modulo the number N.The number of information PSP elements is N + 1, therefore, the counter of the information PSP shaper counts clock pulses modulo the number N + 1.

At the beginning of the formation of the clock signal, both counters are in the zero state, that is, at the outputs of their bits, there are binary codes for the number zero. In the future, each time when the counter of the information PSP shaper is set to zero (Fig. 1a), the number whose binary code is set at the outputs of bits of the counter of the synchronizing PSP shaper increases by one (Fig. 1b). If the duration of the clock signal is equal to M repetition periods of the information PSP, then the end of the clock signal corresponds to the moment when the code of the number zero is set at the outputs of the bits of the counter of the information PSP shaper, and the code of the number M is set at the outputs of the bits of the counter of the synchronizing PSP shaper.That's why the sign can be determined by the end of the clock signal in the receiving device.

In the future, the operation of the receiving device is carried out in accordance with the program, the commands of which change at times corresponding to the zero state of the counter of the information PSP generator. This program rebuilds the frequency synthesizer (local oscillator) in accordance with the law of changing the carrier frequency of the signal in the transmitter.

At each transition to a new frequency during the first repetition period of the information SRP, only the automatic signal level control circuit and the narrowband interference protection circuit operate. If, in the next few repetition periods of the information SRP, in accordance with the program, a carrier frequency signal is transmitted, manipulated in the phase of the synchronizing SRP, the auto-tuning of the clock frequency is turned on in the receiving device. The rest of the time, incoherent reception of information symbols is carried out.

In this mode, the transmitted signal has the form

– модулированная ПСП.where

– modulated PSP.

, то есть на синхронизирующую ПСП, приведенную к биполярному виду. После этого вычисляют корреляцию квадратурных огибающих с каждым из сигналов вида

(i = 1…Q), где

соответствует i-му из Q возможных передаваемых информационных символов, а также сумму их квадратов. Выбирают максимальное из Q значений суммы квадратов и соответствующую ему модулированную ПСП, по которой определяют передаваемый информационный символ.Optimal non-coherent reception of such signals involves premultiplying the quadrature envelopes of the input signal by

, that is, to the synchronizing PSS reduced to the bipolar form. After that, the correlation of the quadrature envelopes with each of the signals of the form

(i = 1…Q), where

corresponds to the i-th of the Q possible transmitted information symbols, as well as the sum of their squares. The maximum of the Q values of the sum of squares and the corresponding modulated PRP are selected, according to which the transmitted information symbol is determined.

Note that for large Q, that is, a large number of different transmitted information symbols, the noise immunity of incoherent reception differs slightly from the noise immunity of coherent information reception. Given that the full power of the signal is used to transmit information, the noise immunity of receiving information is increased by almost 3 dB compared to the prototype.

An example of a technical implementation of a device for generating a transmitted signal is shown in Fig. 2.

The device contains:

1 – generator of clock frequency signals (FCF);

2 – frequency divider by N+1;

3 - parallel register;

4 – counter modulo N;

5 – counter modulo N+1;

6 – modulo N adder;

7, 8, 9 - read only memory (ROM);

10 – modulo two adder;

11 - scheme 2OR;

12 – command counter;

13 - switch;

14 - scheme 2I;

15 – ROM for the carrier frequency tuning program (ROM for the carrier frequency);

16, 17 - level converter (PU);

18 – carrier frequency synthesizer;

19, 20 - multiplier;

21 - adder.

The device works as follows. The clock signal generated by the FTF 1 is fed to the clock inputs of the frequency divider by ( N + 1 ) 2, the modulo counter N 4 and the modulo counter ( N + 1 ) 5. The external transmission enable signal (RP) is fed to the counter reset inputs 4, 5, the input for the initial setting of the frequency divider 2 and the input for resetting the command counter 12.

In the absence of the RP signal, the counters 4, 5, 12 are in the zero state, and the frequency divider 2 is in the initial state. Upon arrival of the RP signal, counters 4, 5 and frequency divider 2 begin to work. Frequency divider 2 generates pulses with a duration equal to one period τ of the clock frequency, and with a repetition period (N + 1) τ equal to the repetition period of the information SRP. These pulses are fed to the clock inputs of the parallel register 3 and the program counter 12, as well as to one of the inputs of the circuit 2OR 11.

The signals from the outputs of the digits of the command counter 12 are fed to the address inputs of the ROM PPCH 15, which generates control signals that specify the modes of operation of the device. The choice of such a control method is explained by the fact that all changes in the signal formation occur at times that are multiples of the repetition period of the information PRP.

The formation of pseudo-random sequences occurs as follows. At the outputs of counters 4 and 5 with a frequency of clock pulses, periodic sequences of multi-digit binary numbers [0, …, N - 1] and [0, …, N] are formed, respectively. The output signals of the counter 4 are fed to the address inputs of the ROM 7, which contains the synchronizing PSP. At the output of the ROM 7 is formed periodically repeating synchronizing PSP.

Similarly, the output signals of the counter 5 are fed to the address inputs of the ROM 8, which contains the information PSP, supplemented by one element. At the output of the ROM 8 is formed periodically repeating information PSP, supplemented by one element.

и

⁾, которые поступают на первые входы перемножителей 19 и 20 соответственно. На вторые входы перемножителей 19, 20 поступают сдвинутые между собой по фазе на девяносто градусов сигналы несущей частоты, формируемые синтезатором несущей частоты 18.The clock signal is formed during the first M ₀ periods of the information SRP. At this time, at the outputs of the command counter 12, a sequence of multi-bit binary numbers [0, ..., M ₀ - 1] is formed. At these addresses in the ROM PPNCH 15 recorded code of the carrier frequency, which transmits the clock signal. From the multi-bit output of the ROM 15, this code is fed to the input of the carrier frequency synthesizer 18. At the output connected to one of the inputs of the 2I circuit 14, as well as at the output connected to the control input of the switch 13, the ROM 15 generates signals with a logic zero level. At the same time, a synchronizing PRS (SP(t)) is supplied to the input of level converter 16, and an information PRS (IP(t)) is supplied to the input of level converter 17. In level converters 16, 17, binary sequences are converted into bipolar signals of the form

and

⁾ , which are fed to the first inputs of the multipliers 19 and 20, respectively. The second inputs of the multipliers 19, 20 receive carrier frequency signals shifted in phase by ninety degrees, which are generated by the carrier frequency synthesizer 18.

, а на выходе перемножителя 20 –

), где f – значение несущей частоты. В результате суммирования в сумматоре 21 формируется выходной сигнал вида At the output of multiplier 19, the signal has the form

, and at the output of the multiplier 20 -

) , where f is the value of the carrier frequency. As a result of summation in adder 21, an output signal of the form

Starting from the M ₀ -th state of the command counter 12, software tuning of the carrier frequency of the signal is carried out. With the sequential passage of certain numbers of commands M ₀ , M ₁ , M ₂ , M ₃ ... the code of the carrier frequency at the outputs of the ROM PPFC 15, controlling the carrier frequency synthesizer 18, changes according to a pseudo-random law. These numbers can be unevenly distributed along the number axis, in which case the transmission time at each frequency will also change according to a pseudo-random law.

Starting from the M ₀ state of the command counter 12, at the output of the ROM PPCH 15, connected to the control input of the switch 13, a signal with the level of a logical unit is generated. At the same time, the same signal CM(t) is supplied to the inputs of the level converters 16, 17 from the output of the adder modulo two 10, and at the output of the adder 21 a signal of the form

Thus, when transmitting a radio control command, the carrier frequency signal is manipulated in phase by a binary sequence from the output of the adder modulo two 10.

Consider the output signal of the ROM PPFC 15, coming to one of the inputs of the circuit 2I 14. With the command numbers M ₀ , M ₁ , M ₂ , M ₃ ... it has a logic zero level. In addition, for some values of M _i its level can save the value of logical zero at M _i +1, M _i +2,..., M _i +k . In this case, a logical zero is formed at the output of the 2I circuit 14, and a synchronizing PSP is formed at the output of the adder modulo two 10. Thus, at each value of the carrier frequency, during one or more periods of the information PR, the carrier signal is keyed in the phase of the synchronizing PR. The rest of the time, information symbols of the control command are transmitted as follows.

The external data transmission device (EDD) receives the RD enable signal from one of the ROM ROM outputs and the TI clock pulses from the output of the frequency divider to (N + 1) 2. character to the input of parallel register 3. This code is written to register 3 on the trailing edge of the TI. From the output of register 3, the binary code of the new transmitted information symbol is fed to one of the inputs of the adder modulo N 6, the second input of which receives a multi-bit signal from the output of the counter modulo (N + 1) 5. At the output of the adder modulo N 6, a sequence is formed, which is a cyclic shift of the sequence [0, …, N - 1]. The shift value is equal to the number whose binary code is stored in register 3.

The output signals of the adder modulo N 6 are fed to the address inputs of the ROM 9, which contains the information PSP. At the output of the ROM 9, a modulated PSP is formed, which is a non-extended cyclically shifted information PSP. In the 2OR 11 circuit, a constant element equal to a logical unit is added to it at the moment the pulse arrives from the output of the frequency divider to (N + 1) 2.

The output signal of the 2OR circuit 11 passes to one of the inputs of the modulo two adder 10, the second input of which receives the synchronizing SRP, and the sum modulo two of the synchronizing SRP and the modulated SRP is formed at the output, which manipulates the carrier frequency signal in phase.

SOURCES OF INFORMATION

1. Sklyar B. Digital communications. Theoretical foundations and practical application. Ed. 2nd, corrected: Per. from English. - M .: Williams Publishing House, 2004. - 1104 p., p. 733-819.

1. Borisov V. I. et al. Noise immunity of radio communication systems with the expansion of the spectrum of signals by modulation of the carrier pseudo-random sequence - M .: Radio and communication, 2003. - 641 p.

2. Patent RU 2646 353 C1. Transmitter of increased structural and energy secrecy. Published on 02.03.2018. Bull. No. 7.

3. Patent RU 2127 486 C1. Method and device for transmitting messages by broadband signals. Published 03/10/1999.

5. Patent RU 2731 681 C1. Method for generating noise-like phase-shift keyed signals. Published on 07.09.2020. Bull. No. 25.

Claims (1)

A method for transmitting radio control commands with spread spectrum signals, which consists in the fact that carrier and clock signals are generated, binary pseudo-random sequences (PRS) of maximum length are formed from the clock frequency signal, synchronizing and informational, informational PRS are extended by one constant element and at each period repetitions of the information SRP form a modulated SRP by cyclically shifting the non-extended information SRP by the number of elements determined by the transmitted information symbol, and adding one constant element, characterized in that at the beginning of the transmission of each radio control command, the synchronizing SRP and the information SRP are phased together, and a clock signal is transmitted , for the formation of which the synchronizing SRP and the information SRP are converted into bipolar signals, which carry out quadrature modulation of the carrier frequency signal, and the duration of the sync signal is chosen as a multiple of the repetition period when transmitting a radio control command, the value of the carrier frequency is changed according to a pseudo-random law at time intervals that are multiples of the repetition period of the information PRP, with each new value of the carrier frequency, the carrier frequency signal is first manipulated in the phase of the synchronizing PRP over one or more repetition periods of the information PRP , and in the future, for manipulation, a sequence is used, which is obtained by modulo two addition of the synchronizing PRS and the modulated PRS.

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