RU2231924C1 - Method for shaping noise-like radio pulses for transmitting binary data characters by composite signals - Google Patents

Abstract

FIELD: radio engineering; data transfer systems.

SUBSTANCE: proposed method is characterized in that minimal code-frequency modulation of carrier frequency is effected by adding amplitude- and phase-modulated waves of quadrature channels whose modulating code sequences are obtained by re-coding code sequence of noise-like radio pulse, sum obtained is gated by video pulse equal to length of code sequence, opposing signal is shaped by code inversion with aid of modulating code sequence of one of quadrature channels.

EFFECT: enhanced noise immunity of data transfer system.

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Description

The invention relates to radio engineering and can find application in information transmission systems, in the field of radar, radio navigation, ionosphere remote sensing systems and other radio engineering systems and devices that require reliable signal isolation, high noise immunity and resolution.

There is a method of generating noise-like signals by phase modulating the carrier frequency with a code sequence, and when the code symbol is +1, the carrier frequency itself is transmitted, if the code symbol is -1, the phase of the carrier changes by 180 ° [R. Dixon Broadband systems / Translated from English by V.I.Zhuravlev. M .: “Communication”, 1979. 304 p.].

The disadvantages of the method are that the phase shift keying used to obtain the encoded radio pulse has the property of ambiguity of the decision, which leads to negative work, namely, that the transmitted “unit” can be accepted as “zero”, and “zero” - as “ unit". This drawback is fundamentally unrecoverable for phase manipulation, as a result of which code-manipulated radio pulses cannot be used as opposite signals for transmitting binary information symbols.

A known method of transmitting binary symbols of information by complex signals, in which the phase modulation of the carrier frequency with a code sequence is used to form a binary “unit”, and the carrier is modulated by another code sequence to generate a “zero”, the code of which differs from the previous one [N. Petrovich, Razmakhnin M.K. Communication systems with noise-like signals. - M .: “Soviet Radio”, 1969, p.122], close in technical essence and the achieved result and adopted as a prototype. In this method, the transition from “one” to “zero” and vice versa is done by switching the feedback circuits of the shift register that generates the code sequence.

The disadvantage of this method is that the correlation functions of codes displaying binary “one” and “zero” have a significant difference in the structure of the side lobes, which leads to a difference in the probability of the presence of “zero” or “unity” at the input of the receiving device.

It is known from the theory of noise-tolerance reception that opposite signals have the greatest noise immunity. Noise-like radio pulses possessing such properties have correlation functions that are identical in structure but differ in polarity. Such radio pulses can be obtained using intrapulse frequency shift keying, which eliminates the uncertainty in the initial phase of the received radio pulse and enables the direct code to be used to transmit the binary “unit” symbol, and the inverse code can be used to transmit the binary “zero” or vice versa.

The invention is aimed at improving the noise immunity of an information transmission system through the use of complex noise-like radio pulses having the properties of opposite signals.

The problem is solved in that in the method for generating noise-like radio pulses for transmitting binary information symbols with complex signals, including modulating the carrier frequency with a code sequence, the minimum frequency-frequency modulation of the carrier frequency is carried out by summing the quadrature channels modulated in amplitude and phase of oscillation, the modulating code sequences of which are obtained by code-code conversion a noise-like radio pulse sequence, then gating the resulting amount of video pulse equal to the duration of the code sequence, the formation of the opposite signal is carried out by inverting the code of the modulating code sequence of one of the quadrature channels.

The code structure of the modulating code sequence of each channel as a result of transcoding should be such that the result of bitwise multiplication of the codes of the quadrature and in-phase channels is the required code of the noise-like radio pulse. In addition, a video pulse is generated, the duration of which is equal to the duration of the code sequence, intended for use as a gating pulse. In each channel, the modulating code sequence is multiplied with the quadrature components of the low-frequency harmonic oscillation, the period of which is equal to four times the duration of the elementary pulse of the code, the spectrum of the obtained oscillation is transferred to the high-frequency region, as a result of which the oscillations modulated in amplitude and phase are obtained.

After summing the amplitude and phase oscillations of the quadrature channels, a noise-like radio pulse is generated by gating.

To form the opposite signal, it is enough to invert the code sequence of one of the quadrature channels.

The distinguishing features of the invention are that they carry out the minimum frequency-frequency modulation of the carrier frequency by summing the quadrature channels modulated by the amplitude and phase of oscillations, the modulating code sequences of which are obtained by re-encoding the code sequence of a noise-like radio pulse, by gating the resulting amount with a video pulse equal to the length of the code sequence, generating the opposite signal carry out code inversion modulating code new sequence of one of the quadrature channels.

The presence of distinctive features allows us to conclude that the claimed invention meets the criterion of "novelty."

The analysis of patent and scientific and technical information did not allow to identify sources containing information about the fame of the distinguishing features of the claimed invention, which indicates the compliance of the claimed invention with the criterion of “inventive step”.

The implementation of the proposed method will be considered on the example of the formation of a noise-like radio pulse with an internal pulse minimum frequency manipulation, encoded in accordance with the Barker code with a duration of N = 7, the code of which is presented in the form

shown in figure 1, where a) a Barker code with a duration of N = 7.

To generate a noise-like radio pulse with an internal pulse minimum frequency manipulation in accordance with this code, transcoding is necessary, for this:

1) generate an in-phase component, I, whose code is of the form

1,1,1, -1, -1,1,1,

a view of the in-phase component of the code is shown in FIG. 1, where b) the code of the modulating code sequence of the in-phase channel;

2) generate a quadrature component, Q, in the form

1,1,1,1,1,1, -1,

shown in figure 1, where c) the code of the modulating code sequence of the quadrature channel;

3) generate a gating pulse of duration Nτ, which in the example under consideration is 7τ, where τ is the duration of the elementary discrete of the Barker code

1111111,

figure 1, where d) a strobe video pulse.

It is easy to verify that the bitwise product of codes I and Q gives the Barker code (1), indeed, having performed bitwise multiplication, we obtain

. На фиг.2 показаны осцилограммы: а) - модулирующей кодовой последовательности синфазного канала, b) - гармонической функции с периодом, равным 4τ, и с) - результата их перемножения. Полученное произведение умножается на косинус несущей частоты, Cosωt, в результате этих операций получают модулированную по амплитуде и фазе составляющую4) the in-phase component, I, is multiplied by the cosine of the harmonic function,

. Figure 2 shows the oscillograms of: a) the modulating code sequence of the in-phase channel, b) the harmonic function with a period equal to 4τ, and c) the result of their multiplication. The resulting product is multiplied by the cosine of the carrier frequency, Cosωt, as a result of these operations, a component modulated in amplitude and phase is obtained

, а полученное произведение умножается на синус несущей частоты, Sinωt, в результате чего получают модулированную по амплитуде и фазе составляющую5) the quadrature component, Q, is multiplied by the sine of the harmonic function,

, and the resulting product is multiplied by the sine of the carrier frequency, Sinωt, resulting in a component modulated in amplitude and phase

6) summarize the resulting products (2) and (3)

7) oscillation (4) is isolated by a gating pulse, as a result of which a noise-like radio pulse with intrapulse frequency shift keying is obtained, encoded according to the law of changing the sign of the product (IQ) (in the example considered, the Barker code). The result obtained is demonstrated by the oscillogram shown in figure 2 d).

, а при отличающихся знаках

. Переход с одной частоты на другую происходит без разрыва фазы.From (4) it can be seen that when the signs of codes I and Q coincide, the frequency of the resulting oscillation is

, and with different signs

. The transition from one frequency to another occurs without phase disruption.

If you invert the code in one of the quadrature channels, we get the opposite noise-like radio pulse, the steps of which are shown in Fig. 3, which shows: a) the inverted modulating code sequence of the in-phase channel, b) the cosine of the harmonic function, whose period is 4τ, c) the result multiplying the harmonic function and the inverted modulating code sequence, d) the generated opposite noise-like radio pulse with intrapulse minimal frequency manipulation.

Comparing noise-like radio pulses in figure 2 d) and 3 d). it can be noted that noise-like radio pulses have the same amplitudes and durations, therefore, have the same energy. In the signal in FIG. 2 d) a positive code symbol is transmitted by a lower frequency ω ₁ , and a negative symbol is transmitted by a higher frequency ω ₂ . The signal shown in figure 3 d), on the contrary. Thus, encoding the transmitted binary information symbols using opposite signals of the proposed type, after appropriate processing at the receiving end of the radio line, we obtain a correlation function, the main maximum of which takes a positive or negative value depending on the transmitted symbol, and its polarity does not depend on the phase ratio received and reference oscillations, which leads to an increase in noise immunity of the transmission system.

Claims (1)

A method for generating noise-like radio pulses for transmitting binary information symbols with complex signals, including modulating the carrier frequency with a code sequence, characterized in that the minimum frequency-frequency modulation of the carrier frequency is carried out by summing the amplitude and phase oscillations of the quadrature channels, the modulating code sequences of which are obtained by recoding the code sequence of the noise-like radio pulse , carry out the gating of the received video amount pulse equal to the duration of the code sequence of the opposite inversion signal generation performed code modulation code sequence of one of the quadrature channels.

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