RU2230433C2 - Orthogonal-signal space communication system - Google Patents

Abstract

FIELD: space radio communications. SUBSTANCE: space radio communication system has on sending end series-connected switch, analog-to-digital converter, Reed-Muller code generator, pulse train shaping unit incorporating three counters, four NOT gates, two three-input AND gates, OR gate, logic multiplying unit incorporating two NAND gates, OR gate, modulator-transmitter, and transmitting antenna; on receiving end it has receiving antenna, receiver, delay line, synchronous generator, decoding matrix, and maximal signal decoder. Novelty is introduction of pulse train shaping unit incorporating three counters, four NOT gates, two three-input AND gates, two four-input AND gates, OR gate, and logic multiplying unit that has two NAND gates and OR gate. EFFECT: enhanced noise immunity of communication system. 1 cl, 37 dwg

Description

The invention relates to radio engineering and is intended for use in radio communications. A known broadband phase communication system comprising: a message converter, a quantization unit, an analog-to-digital converter, a carrier frequency generator, a switch, a phase modulator, a band amplifier, an input band amplifier, a block of bandpass filters, a block of amplitude detectors, a block, at the receiving side integrators with reset, decision block, phase detector block, signal switch, adder, gating block, synchronization block, digital-to-analog converter, low-pass filter stot (see. USSR Inventor's Certificate № 1,061,271, cl. H 04 B 7/165, 1982).

However, due to the fact that simple harmonic signals selected as a carrier in this system are highly susceptible to various kinds of interference, therefore, the noise immunity of the communication system will be low.

Closest to the technical nature of the proposed application is a space radio communication system containing: in the transmitting part - a series-connected switch, an analog-to-digital converter, a Reed-Muller code generator, a modulator-transmitter, a transmitting antenna; in the receiving part, a receiving antenna connected to the receiver, from the output of the receiver, the signal enters the delay line, which is connected with a synchronous generator with one of its outputs, and other outputs with a decoding matrix. The outputs of the decoding matrix are connected to the inputs of the maximum signal detector. The other input of the maximum signal detector is connected to the output of the synchronous generator. The outputs of the maximum signal detector are connected to the inputs of the digital conversion matrix, the output of which is the input of the indicating and recording equipment (see Sanders R.V. “Digilok” Communication System. - In the book: Digital Information Transmission. - M.: IL., 1963, p. 187-202).

However, there is a drawback in this space communication system in that the Reed-Muller sequences used as carrier signals have significant side peaks of autocorrelation functions. Moreover, in half of the sequences, the magnitude of the side peaks of the autocorrelation function does not exceed 0.3125, and a synchronization signal can be extracted from them. In the second half of the code sequences, the lateral peaks of the autocorrelation function are greater than this value and it is impossible to synchronize the communication system from them. If we characterize the Reed-Muller sequences used in the prototype as a whole, we can conclude that they do not have sufficiently good autocorrelation properties, as a result of which the noise immunity of the space communication system will be reduced (see L. Varakin, Communication Systems with Noise-Like Signals. - M. : Radio and communications, 1985, p.30).

The aim of the invention is to increase the noise immunity of a communication system.

This goal is achieved by the fact that in a space radio communication system containing a switch connected in series, an analog-to-digital converter, a Reed-Muller code generator, a modulator-transmitter, a transmitting antenna, a receiving antenna on the receiving side, a receiver, a delay line, a synchronous generator a decoding matrix, a maximum signal detector, a digital conversion matrix, indicating and recording equipment, the receiving antenna, receiver and delay line connected in series, and p the next one is connected to the input of the synchronous generator by its output, and the other outputs to the inputs of the decoding matrix, the outputs of which are connected to the inputs of the maximum signal detector, the other input of which is connected to the output of the synchronous generator, the output of the maximum signal detector is connected to the input of the digital conversion matrix, the output of which is connected with the input of the indication and registration equipment, a sequence forming unit is introduced containing three counters, four elements NOT, two three-input elements AND, AND elements and an OR logical element, a multiplication block containing two AND-NOT elements and an OR element, the output of the clock generator being connected to the input of the Reed-Muller code generator, the input of the first counter, the input of the first element NOT and the fourth input of the first four-input element AND block of forming a sequence, the output of the first counter is connected to the input of the second counter, the input of the second element NOT, the third input of the first four-input element And, the second input of the second four-input element And, the output of the second the counter is connected to the input of the third counter, the input of the third element NOT, the second input of the second three-input element And, the second input of the first four-input element And, the output of the third counter is connected to the first input of the first four-input element And, the input of the fourth element NOT, the third input of the second four-input element And, the third input of the second three-input element And, the output of the first element is NOT connected to the first input of the first three-input element And and the first input of the second four-input element And, the output is W of the second element is NOT connected to the first input of the second three-input element And, the second input of the first three-input element And, the output of the third element is NOT connected to the third input of the first three-input element And, the output of the fourth element is NOT connected to the fourth input of the second four-input element And, the outputs of the first and second four-input elements And, the first and second three-input elements And are connected respectively with 1-4 inputs of the four-input element OR, the output of which is the output of the sequential block They are connected to the first inputs of the first AND-NOT element and the second input of the OR element of the logical multiplication unit, the second input of the first AND-element and the first input of the OR element are connected to the output of the Reed-Muller code generator, and the outputs of the first AND-NOT element and the element OR connected to the first and second inputs of the second AND-NOT element, the output of which is the output of the logical multiplication unit and connected to the input of the transmitter.

Figure 1 presents the structural diagram of the inventive space radio communication system; figure 2 is a structural diagram of a Reed-Muller code generator and timing diagrams explaining the principle of its operation; figure 3 is a timing diagram explaining the principle of operation of the block forming the sequence; figure 4 is a timing diagram explaining the principle of operation of a space radio communication system when transmitting sequence No. 27; figure 5 - code combination of the main Reed-Muller code; figure 6 - code combinations of the additional Reed-Muller code; 7 is an ensemble of discrete orthogonal signals (DOS) with improved correlation properties; on Fig - aperiodic functions of autocorrelation (FAK) of the modified Reed-Muller code; figure 9 - aperiodic FAK ensemble DOS with improved correlation properties; figure 10 is a typical view of the unnormalized periodic functions of autocorrelation (PFAC) of sequences of the modified Reed-Muller code and the ensemble DOS with improved correlation properties.

The space radio communication system proposed in FIG. 1 contains on the transmitting side a switch 1 of an analog-to-digital converter 2 (ADC), a Reed-Muller 3 code generator, including binary counters 3.1, 3.2, 3.3, elements I 3.4, 3.5, 3.6, 3.7 , 3.8 and half-adders 3.9, 3.10, 3.11, 3.12 shown in Fig. 2, a sequence forming unit 4 (including counters 4.1, 4.2, 4.3, elements NOT 4.4, 4.5, 4.6, 4.7, three-input elements AND 4.9, 4.10, four-input elements AND 4.8, 4.11 and four-input element OR 4.12), the logical unit of multiplication 5 (including two inputs th elements NAND 5.1, 5.3 and a two-input element OR 5.2), a modulator-transmitter 6, a transmitting antenna 7; on the receiving side, a receiving antenna 8, a receiver 9, a delay line 10, a synchronous generator 12, a decoding matrix 11, a maximum signal detector 13, a digital conversion matrix 14, indicating and recording equipment 15.

The space radio communication system operates as follows.

Analog information is fed to the input of switch 1, which serves to switch various sources of analog voltage. The output voltage of the switch is fed to an analog-to-digital converter 2, in which analog information is converted to binary form in the form of 5-bit groups at the ADC output, by means of which the generator 3 of the Reed-Muller codes are controlled. In the case of transmitting information in digital form, it also arrives at switch 1, where it is switched by means of strobe pulses, and in analog-to-digital converter 2 it is also reduced to the form of 5-bit groups. From the five output buses of the analog-to-digital converter 2, the information comes in the form of parallel-transmitted manipulated signals (of the “On - Off” type) that gate the outputs of the binary counters and the additional DC bus of the Reed-Muller code generator 3. Block diagram of the Reed-Muller code generator and timing diagrams explaining the principle of sequence formation No. 27 of the main Reed-Muller code are shown in FIG. 2.

From the output of the Reed-Muller 3 code generator, the generated sequence is fed to the second input of the multiplication logic unit 5. Simultaneously and synchronously with the formation of the sequence in the Reed-Muller 3 code generator, the sequence is formed on the sequence generation unit, by which all sequences are multiplied in the logical multiplication unit 5, coming from the output of generator 3, as a result of which the structure changes and the correlation properties of the sequences arriving at the modulator Occupancy 6. Timing diagrams for explaining the principle of operation sequence generation unit 4, shown in Figure 3. The principle of its work is as follows. Upon receipt of clock pulses at its input with the help of its counters and logic elements, the sequence shown in the time diagram is cyclically formed (Fig. 3, n). In the logical unit of multiplication 5, logical multiplication of the sequences coming from the output of the Reed-Muller code generator with the sequence coming from the output of the sequence forming unit in accordance with the state table shown in Fig. 4 is performed. The timing diagrams shown in FIG. 4 illustrate the multiplication of sequence No. 27 of the main Reed-Muller code, with the sequence coming from the output of sequence forming unit 4. As a result, the sequence acquires improved correlation properties. The principle of operation of the Reed-Muller code generator 3, the sequence generating unit 4, the multiplication logic unit 5 when generating other sequences of the primary and secondary Reed-Muller codes and the ensemble of signals with improved correlation properties is similar to that described above. Their appearance is presented respectively in FIGS. 5, 6, 7. After the logical multiplication of the sequence of the ensemble of signals with improved correlation properties, they are transmitted to the modulator-transmitter 6, where they are modulated by phase modulation and emitted using a transmitting antenna 7. Received using a receiving antenna 8, the signals are fed to the input of the synchronous receiver 9 with a phase detector, where they are demodulated and then fed to the input of the delay line 10 with taps and a low-pass filter. A delay line 10 with sixteen taps and a low-pass filter at the input is used to implement matched filters for the ensemble of signals with improved correlation properties shown in Fig.7. Sixteen taps of the delay line 10 are connected via a linear summing matrix 11 to 32 buses, one bus for each transmitted signal. When, for example, signal No. 27 completely fills the delay line, the voltage on bus No. 27 will have a large positive value. The output voltage of all other buses in the absence of noise will be 0, with the exception of bus No. 26, on which a large negative voltage develops (this is due to the fact that signal No. 27 is an addition to signal 26, i.e., inverse to it). The outputs of the matrix 11 are connected to the detector of the maximum signal 13, in which a large output voltage appears only on one of the 32 conductors in accordance with the received signal, in this case, on the 27th output when receiving sequence No. 27. Next, the signal on the 27th bus from the output the detector of the maximum signal 13 is fed to the input of the digital conversion matrix 14, on which the processes that are inverse to those that were in the analog-to-digital converter 2 during information transmission occur. An analog or discrete signal from the output of the digital conversion matrix is fed to the input of the indication and recording equipment. Consistency in processing the received signal is achieved through the use of a synchronous generator 12, the synchronous input of which is connected to the delay line 10, which receives information about the timing of synchronization after analysis of the autocorrelation function of the received sequence.

It is known that the autocorrelation function (FAC) of a signal is determined by the expression

where τ is the value of the time shift of the signal. It can be seen from expression (1) that R (τ) characterizes the degree of connection (correlation) of the signal S (τ) with its copy shifted by the value of τ along the time axis. It is also seen from (1) that the function R (τ) reaches a maximum at τ = 0, since any signal is correlated with itself. Wherein

That is, from expression (2) it follows that the maximum value of the autocorrelation function of a signal is equal to its energy (see IS Gonorovsky, Radio Engineering Circuits and Signals. - M.: Soviet Radio, 1971, p. 68).

In the event that the signals are normalized by energy, taking into account E = 1, the autocorrelation function (ACF) of the FM NPS consists of a central peak with an amplitude of 1 and side peaks. The amplitudes of the side peaks can take different values, but for signals with good correlation properties they are small, that is, significantly less than the amplitude of the central peak, equal to 1 (see Varakin L.E. Communication systems with noise-like signals. - M .: Radio and communications, 1985, p.30).

Therefore, the value of the side peaks of the ACF, which are usually less than the main one, depend on the actual used code sequence and are the result of a partial correlation of the code sequence with the same code sequence shifted in time. When such side peaks of the ACF occur, the ability of the receiver (a communication system using signals of a certain class) to establish reliable synchronization deteriorates, since in this case it must distinguish between the main (central) and maximum side peaks of the ACF (see Dixon R.K. Broadband systems . - M .: Communication, 1979, p.64). Obviously, signals with lower side peaks of the ACF are more noise-resistant.

Using computers, the authors synthesized an ensemble of orthogonal signals, shown in Fig.7, with improved correlation characteristics, used as carriers of information in the inventive communication system. The synthesized ensemble of signals has an advantage in its correlation properties compared to the modified Reed-Muller code used in the space radio communication system - prototype. Therefore, the use of a synthesized ensemble of orthogonal signals can improve the noise immunity of a space radio communication system. To quantify the gain in noise immunity, we use the following relation (see L.E. Varakin. Detection of complex signals and measurement of their parameters, in the journal "Radio Engineering and Electronics", 1973, No. 8, p. 1594).

where q is the signal-to-noise ratio,

R _max (τ) is the value of the maximum side peak of the ACF of the used code sequence.

According to (3), the maximum lateral peak of the ACF R _max. (τ) practically will not affect the probability of correct detection of the signal P _rights ., if the difference qR _max (τ) is greater than or equal to six.

Hence the value of the maximum side peak of the ACF at the desired signal-to-noise

Let us determine the value of q at various values of R _max (τ) for the modified Reed-Muller code and the synthesized ensemble of discrete orthogonal signals.

According to the ACF values presented in FIG. 9, for a synthesized ensemble, the values of R _max. (τ) = 0.1875 for all 100% of the ensemble sequences. Therefore, when applying an ensemble of signals synthesized by the authors in a communication system, the signal-to-noise ratio for the communication system in accordance with (4) is determined as follows:

From the expression (5) it follows that q≥7.3846.

According to the ACF values shown in Fig. 8, for the modified Reed-Muller code, the values of R _max. (τ) = 0.5. Therefore, the signal-to-noise ratio value for a communication system with Reed-Muller codes in accordance with ratio 4 is defined as

,

,

q≥12.

It can be seen from the obtained calculations that when using a system of discrete orthogonal signals synthesized by the authors in a space radio communication system to ensure the minimum probability of correct reception of P _rights. it is necessary to provide a lower signal to noise ratio than when using the modified Reed-Muller code. The gain in this case with a signal-to-noise ratio is 38%.

Claims (1)

A space radio communication system comprising, on the transmitting side, a switch, an analog-to-digital converter, a Reed-Muller code generator, a modulator-transmitter, a transmitting antenna, a receiving antenna on a receiving side, a delay line, a synchronous generator, a decoding matrix, a maximum signal detector, a digital conversion matrix, indicating and recording equipment, the receiving antenna, receiver and delay line connected in series, and the last one connected with its output to the input of the synchronous generator, and other outputs with the inputs of the decoding matrix, the outputs of which are connected to the inputs of the maximum signal detector, the other input of which is connected to the output of the synchronous generator, the output of the maximum signal detector is connected to the input of the digital conversion matrix, the output of which is connected to the input of the indication and recording equipment characterized in that a sequence forming unit comprising three counters, four elements of NOT, two three-input elements AND, two four-in of an AND element, a four-input OR element, a logical multiplication unit containing two AND-NOT elements, an OR element, the output of the clock being connected to the input of the Reed-Muller code generator, the input of the first counter, the input of the first element NOT and the fourth input of the first four-input element And, the output of the first counter is connected to the input of the second counter, the input of the second element NOT, the third input of the first four-input element And, the second input of the second four-input element And, the output of the second counter is connected with the input of the third counter, the input of the third element NOT, the second input of the second three-input element And, the second input of the first four-input element And, the output of the third counter is connected to the first input of the first four-input element And, the input of the fourth element NOT, the third input of the second four-input element And, the third input the second three-input element AND, the output of the first element is NOT connected to the first input of the first three-input element And and the first input of the second four-input element And, the output of the second element is NOT is connected to the first input of the second three-input element And, the second input of the first three-input element And, the output of the third element is NOT connected to the third input of the first three-input element And, the output of the fourth element is NOT connected to the fourth input of the second four-input element And, the outputs of the first and second three-input elements And, the first and second four-input elements AND are connected respectively with 1-4 inputs of the four-input OR element, the output of which is the output of the sequence forming unit and is connected to the first input of the first AND-NOT element and the second input of the OR element of the logical multiplication block, the second input of the first AND-NOT element and the first input of the OR element are connected to the output of the Reed-Muller code generator, and the outputs of the first AND-NOT element and the OR element are connected to the first and the second inputs of the second AND-NOT element, the output of which is the output of the logical unit of multiplication and connected to the input of the transmitter.

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