RU2801873C1 - Method for forming noise-like signals - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: two carrier frequency signals are formed, shifted between themselves in phase by ninety degrees, and a clock frequency signal. Binary quasi-orthogonal pseudo-random sequences, synchronizing (SP) and informational (IP), are formed from the clock frequency signal. At each repetition period of the SP, a modulated sequence (MP) is formed by cyclic shifting of the IP relative to the SP. A compositional sequence is formed by switching the MP and SP elements with a clock frequency signal. One of the carrier frequency signals is manipulated in the phase of the composite sequence, and the second one is manipulated by the sequence obtained by modulo two addition of the clock frequency signals with the elements of the composite sequence, and they are summed.

EFFECT: reduction up to ninety degrees of signal phase jumps occurring on simultaneous change in sequence values, which are phase-manipulated by carrier frequency signals.

1 cl, 2 dwg

Description

The invention relates to the field of radio engineering and can be used in radio communication systems with noise-like signals and non-linear transmitter power amplifiers to reduce the level of out-of-band radiation.

The disadvantage of noise-like phase-shift keying signals generated by classical methods [1, pp. 16-20] is the presence of phase jumps by one hundred and eighty degrees. When filtering such signals, in order to suppress out-of-band spectral components, deep amplitude modulation occurs, up to the envelope turning to zero. If further the signal passes through the transmitter's non-linear power amplifier, the envelope is restored, and with it the suppressed spectral components [2, p. 580].

The aim of the invention is to develop a method for generating noise-like signals, in which phase jumps do not exceed ninety degrees. When filtering such signals, a slight drop in the envelope occurs in the region of phase jumps, and with further limiting, the envelope is restored, and the spectral components are not amplified [2, p. 580]. The achieved result is the possibility of using transmitters in systems with non-linear power amplifiers.

The closest in terms of the number of matching features to the claimed method is the method of generating noise-like signals, described in [3].

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 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 in a time equal to the period of pseudo-random sequences. The cyclically shifted IP sequence is summed modulo two with an additional bit of information, and the phase of the carrier signal is manipulated. A second carrier frequency signal is formed, shifted relative to the first one in phase by ninety degrees, which is manipulated in phase by the SP sequence and summed with the manipulated first carrier frequency signal.

The disadvantage of the prototype method is the presence of jumps in the phase of the signal one hundred and eighty degrees that occur at the time of simultaneous changes in the values of the sequences that are manipulated in phase by the carrier frequency signals.

To solve the problem posed in the invention in the method of generating noise-like signals, which consists in the fact that a clock frequency signal is formed in the form of a meander and two carrier frequency signals shifted between themselves in phase by ninety degrees, binary quasi-orthogonal pseudo-random sequences (PSR) are formed from the clock signal ), phased with each other, synchronizing and informational, at each repetition period of the synchronizing SRP, a modulated SRP is formed by cyclically shifting the information SRP relative to the synchronizing SRP by the number of elements determined by the transmitted information symbol, and additional modulo two addition with one more bit of information, according to the invention a composite SRP is formed by switching the elements of the modulated SRP and the synchronizing SRP with a clock frequency signal, one of the carrier frequency signals is manipulated in phase by one hundred and eighty degrees of the composite SRP, and the second carrier frequency signal is manipulated in phase by one hundred and eighty degrees by a sequence that is formed by modulo two addition clock signal with elements of the composite PSP, and sum both phase-shift keyed signals.

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

- Form a clock signal having the shape of a meander.

- Form two signals of the carrier frequency, shifted between themselves in phase by ninety degrees.

- From the clock signal, binary quasi-orthogonal pseudo-random sequences (RRP) are formed, in phase with each other, synchronizing and informational.

- At each repetition period of the synchronizing PRP, a modulated PRP is formed by cyclically shifting the information PRP relative to the synchronizing PRP by the number of elements determined by the transmitted information symbol, and additional modulo two addition with one more bit of information.

- A composite PSP is formed by switching the elements of the modulated PSP and the synchronizing PSP with a clock frequency signal.

- One of the carrier signals is manipulated in phase by one hundred and eighty degrees of the compositional SRP.

- The clock signal is summed modulo two with the elements of the composite SRP and the resulting sequence is manipulated in phase by one hundred and eighty degrees of the second carrier signal.

- Summarize both phase-shift keyed signals.

Consider the mathematical representation of the generated signal. Let us denote the values of the synchronizing SRP and the modulated SRP on the time interval corresponding to -th period of the clock frequency, as And (figure 1, II and figure 1, III). We assume that the clock frequency signal takes the value of a logical unit in the time interval and logical zero on the time interval (figure 1, I). We will also assume that the element of the composite SRP is equal to the element of the synchronizing SRP, when the level of the clock signal is equal to a logical unit (figure 1, IV).

On the time interval the element of the composition sequence is equal to , and on the interval it is equal (figure 1, IV). The elements of the sequence formed by modulo addition of two clock signals with the elements of the composite sequence at these time intervals are equal to And respectively (figure 1, V).

The generated signal on the time interval
has the form

,

and on the interval -

.

By enumerating the values of binary numbers And it is possible to prove the identity

It follows from it that

Thus, the initial phase of the generated signal on the time interval is equal to

and on the interval

Difference of initial phases up to is equal to

Similarly, the difference between the initial phases of the signal at time intervals And up to is equal to

Thus, the phase jumps of the generated signal are ±90 degrees, that is, they do not exceed ninety degrees.

It can be seen from expressions (1) that the synchronizing PRS is transmitted at the time intervals , and the modulated PRS on time intervals . Thus, the transmission time of each PR is halved. However, the amplitude of the signals increases with times, so the energy of the signals used to synchronize and receive information remains the same as in the prototype method.

The signal processing algorithm in the receiving device changes slightly. If you use algorithms that are optimal for signals generated by the prototype method, then the noise immunity will decrease by 3 dB. This is due to the fact that noise is added at those time intervals when the corresponding SRPs are not transmitted. Noise immunity will not change if the correlations of the input signal with the reference SRPs are calculated only at the time intervals of their transmission. For example, when receiving information, it is sufficient to reset the input signal (counts of the quadrature envelopes of the input signal) at time intervals .

Note that the generated signals have a spectrum width twice that of the signals generated by the prototype method. The signal base is doubled and, accordingly, noise immunity is increased by 3 dB in relation to barrage and narrow-band interference.

An example of a technical implementation of a device for generating a noise-like signal according to the claimed method is shown in Fig.2.

The device contains:

1 - parallel register;

2 is an adder modulo N, where N-the number of PSP elements;

3, 6 - Read Only Memory (ROM)

4 – clock frequency signal generator (FSFC);

5 - counter modulo N ,

7, 14 – modulo two adder;

8 - phase shifter;

9 – carrier frequency signal conditioner (FSLF);

10 - switch;

11, 15 – level converter;

12, 16 - multiplier;

13 - adder.

The device works as follows. The clock signal generated by the FSFC 4 is fed to the clock input of the counter modulo N 5. At the outputs of the counter 5, a periodic sequence of multi-bit binary numbers [0, 1, ..., N-1] is formed, which is fed to the address inputs of the ROM 6 and one of multi-bit inputs of the adder modulo N 2. The ROM 6 contains elements of the synchronizing PSP, therefore, a periodic synchronizing PSP is formed at its output. The signal from the output of the transfer of the counter modulo N 5 is fed to the clock input of the parallel register 1 and an external data transmission device (EDD). On this signal, the UPD issues a multi-bit code of the next transmitted information symbol and an additional bit of information to the inputs of the parallel register 1.

The code of the information symbol from the outputs of register 1 is fed to the second input of the adder modulo N 2, at the output of which a cyclically shifted sequence [0, 1, ... , N-1] is formed. The binary representation of the shift value is equal to the information symbol code. Modulo N adder outputs 2 are fed to the address inputs of the ROM 3. The ROM 3 contains the elements of the information PSP, so the information PSP is formed at its output, cyclically shifted by the number of elements, the binary representation of which is equal to the code of the information symbol.

The output signal of the ROM 3 is fed to one of the inputs of the adder modulo two 7, the second input of which receives a signal from the output of the register 1 corresponding to an additional bit of information. At the output of the adder modulo two 7, a modulated PSP is formed, which is fed to one of the inputs of the switch 10. The synchronizing PSP from the output of the ROM 6 is sent to the second input of the switch 10, and the clock signal from the output of the FSFC 4 is sent to the control input.

At the output of the switch 10, a composite SRP is formed, which is fed to the input of the level converter 11 and one of the inputs of the modulo two adder 14. The second input of the modulo two adder 14 receives a clock signal and at its output a sequence of sums modulo two of the clock signal is generated. frequencies with elements of compositional memory bandwidth.

The output signals of the switch 10 and modulo two adder 14 are bipolar in the level converters 11 and 15 and fed to the inputs of the multipliers 12 and 16, respectively. The second input of the multiplier 16 receives a carrier frequency signal from the output of the FSLF 9, and the second input of the multiplier 12 receives a carrier frequency signal shifted in phase by ninety degrees in the phase shifter 8.

At the output of the multiplier 16, a carrier frequency signal is generated, manipulated in phase by one hundred and eighty degrees by the sum modulo two of the clock signal with the elements of the composite SRP. At the output of the multiplier 12, a carrier frequency signal is generated, shifted in phase by ninety degrees and manipulated in phase by one hundred and eighty degrees by the elements of the compositional sequence.

In the adder 13 both phase-shift keyed signals are summed.

SOURCES OF INFORMATION

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

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

3. Patent RU 2279 183 C2. A method for transmitting information in a communication system with broadband signals. Published on 06/27/2006. Bull. No. 18.

Claims (1)

A method for generating noise-like signals, which consists in the fact that a clock frequency signal is formed in the form of a meander and two carrier frequency signals shifted between themselves in phase by ninety degrees; and informational, at each repetition period of the synchronizing PRP, a modulated PRP is formed by cyclically shifting the information PRP relative to the synchronizing PRP by the number of elements determined by the transmitted information symbol, and additional modulo two addition with one more bit of information, characterized in that a composite PRP is formed by switching signal of the clock frequency of the elements of the modulated SRP and the synchronizing SRP, one of the carrier frequency signals is manipulated in phase by one hundred and eighty degrees of the composite SRP, and the second carrier frequency signal is manipulated in phase by one hundred and eighty degrees by the sequence, which is formed by modulo addition of two clock signals with elements composite PSP, and sum both phase-shift keyed signals.

Images