RU2264044C1 - Method for forming phase-manipulated signal with constant envelope - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: method includes receiving signal in method, which can be used as pilot signal, while digital series, connected to information symbols, is divided on two digital information series, analog-digital transformation of two resulting series is performed, one of received signals is multiplied with cophased component of bearing/sub-bearing oscillation, and other - with quadrature component of bearing/sub-bearing oscillation and produced signals are summed together.

EFFECT: forming of signal with constant envelope and phase manipulation without phase shifts for 180 degrees.

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Description

The invention relates to the field of radio engineering, allows you to generate a signal with a constant envelope and phase shift keying without phase jumps of 180 degrees, provided that an algorithm is implemented to generate an informational digital chaotic sequence of numbers {x _n }

or

where n is the sequence number of the sequence number, and the control information parameter λ _i , for i = 1, 2, 3, 4, can take values 2, 3, 4, 5, respectively.

This method can be used in information transfer systems.

A known method of generating signals with a constant envelope and m-ary phase shift keying ([1], p. 555), having the form:

s _i (t) = A ₀ cos (ω ₀ t + 2πi / m).

In this formula:

A ₀ - constant amplitude,

ω ₀ - carrier frequency (subcarrier),

m is the number of possible discrete values of the manipulated parameter.

The method consists in the direct m-ary phase manipulation of the carrier (subcarrier) oscillation and is implemented by connecting a phase modulator to the generator (subcarrier) generator output, while binary symbols from the generator of modulating sequences are supplied to the control input of the latter through digital-to-analog converters. Such a method, for example, is used in a device whose structural diagram is shown as part of a signal former with amplitude-phase modulation in Fig. 9.11 in [1], p. 555. The advantage of this method is its simplicity. However, in the case of using the previously indicated modulating chaotic sequence of numbers {x _n } when generating the signal, a precision phase modulator is required and the demodulator circuit is significantly complicated, which makes using the method for a chaotic sequence practically impossible.

Another way of generating signals with a constant envelope and m-ary phase-shift keying is to use the switch to form two even {a _i } and odd {b _i } binary characters from a digital information stream of symbols {ν}, each of these streams are subjected to digital-to-analog conversion, and then multiplication (using balanced modulators) with the corresponding quadrature components of the carrier (subcarrier) oscillation and the multiplication results are summarized using an adder at the output of which They receive phase-manipulated oscillations with a continuous envelope ([2], p. 36, 37, 83, Fig. 2.1, a and Fig. 3.3). For the case of a unit energy of a symbol, an oscillation of the form is obtained at the output of the adder (formulas (9.4), (9.5) and Fig. 9.10 on p. 553, 555 in [1]):

where T _c is the duration of the m-ary character,

and _i and b _i are elements of the sequences {a _i } and {b _i }, respectively,

In this method, a more compact spectrum of the resulting signal is formed, but with an increase in the number of phase positions, its noise immunity decreases.

For a chaotic sequence of numbers {x _i } formed by any of the above recurrence algorithms, the application of this method leads to a violation of the envelope constancy.

The separation of the information flow of symbols into in-phase and quadrature flows, the subsequent multiplication of the two flows into the quadrature components of the carrier (subcarrier) oscillation, and the summation of the multiplication results are also used in communication channels of the IS-95 standard ([3], pp. 798-805, Fig. 12.40 on p. 799 and fig. 12.43 on p. 804). However, the implementation of this separation is oriented to Walsh sequences and cannot be used in the case of chaotic sequences.

The closest in technical essence is the method of generating signals with a constant envelope and m-ary phase shift keying ([2], p. 83, Fig. 3.3), which consists in the following. The digital sequence associated with the information symbols is divided into two digital information sequences, each of the obtained sequences is subjected to digital-to-analog conversion in the corresponding digital-to-analog converter. Multiply one of the received signals with the in-phase component of the carrier (subcarrier) oscillation, and the other with the quadrature component of the carrier (subcarrier) oscillation. Adding the multiplication results in the adder, a phase-manipulated signal with a constant envelope is obtained at the output of the adder.

However, in the phase-manipulated signal generated by this method, there may be phase jumps of 180 degrees and the method, in principle, does not allow to obtain a constant envelope during phase manipulation of the above chaotic sequences {x _n }.

The objective of the invention is to obtain a constant envelope of the signal with chaotic phase shift keying, while preventing the occurrence of phase jumps by 180 degrees.

The invention achieves the following technical result:

- the method allows to obtain a signal that can be used as a pilot signal on a subcarrier in the processing of oscillations with chaotic angular modulation;

- the method allows by eliminating phase jumps by 180 degrees to reduce distortion associated with the passage of the pilot signal with phase shift keying on the subcarrier through the bandpass filters of the modulator and demodulator.

The specified technical result is achieved in a method consisting in the fact that the digital sequence associated with information symbols is divided into two digital information sequences, digital-to-analog conversion of the obtained two sequences is carried out, one of the received signals with the in-phase component of the carrier (subcarrier) oscillation is multiplied, and the other - with the quadrature component of the carrier (subcarrier) oscillations and summarize the received signals, due to the fact that they carry out the conversion of of a digital sequence associated with information symbols into the original informational digital chaotic sequence associated with informational symbols by manipulating the control parameter of the generating recursive algorithm, two digital informational chaotic sequences are obtained from the initial informational digital chaotic sequence by quadrature transformation.

According to claim 2, one of two recurrence algorithms is used:

or

where n is the number of the element of the chaotic sequence, λ _i is the manipulated information control parameter that takes values 2, 3, 4, 5 for the position number i = 1, 2, 3, 4, respectively.

In this case, a cosine or sinusoidal initial informational digital chaotic sequence is obtained, respectively:

or

the transformation of which gives two informational digital chaotic sequences {a _{n-1, i} } and {b _{n-1, i} }, the elements of which are of the form:

a _{n-1, i} = cos (ξ _n-1 ) - for the in-phase channel

and

b _{n-1, i} = sin (ξ _n-1 ) - for the quadrature channel

or

a _{n-1, i} = cos (η _n-1 ) - for the in-phase channel

and

b _{n-1, i} = sin (η _n-1 ) - for the quadrature channel.

Further, these two informational digital chaotic sequences are subjected to digital-to-analogue conversion.

Thus, the technical result is achieved in the method by providing the possibility of using special digital processing of numerical sequences converted to chaotic numerical sequences.

Essentially, a common thing between the invention and the prototype is the approach to the problem of generating a phase-manipulated signal with a constant envelope, in which this signal is obtained by adding the components obtained after multiplying the quadrature components of the carrier (subcarrier) oscillation with the streams of the corresponding digital sequences converted into digital-to-analog converters.

The invention is illustrated graphic materials, where:

- figure 1 shows a block diagram of a device with which the claimed method is implemented;

- figure 2 presents a block diagram of an algorithm for modeling processes occurring in the device;

- figure 3. a, b, c presents graphs of processes at the outputs of the device blocks.

The method is as follows.

At the control input of the generator of a chaotic digital sequence 1, an informational digital sequence of numbers of the modulating control parameter is supplied. The digital sequence from the output of the generator of a sequence of random numbers 1 (Figure 1) is fed to the input of the converter 2. The digital sequences generated in the converter 2 (Figure 2) are fed through the blocks of the corresponding digital-to-analog converters 3, 4 to the first inputs of the balanced modulators 5, 6. The signal from the output of the carrier (subcarrier) generator 7, it is fed to the second (reference) input of the balanced modulator 5 of the in-phase channel and through the phase shifter 8 90 degrees to the second (reference) input of the balanced modulator 6 of the quadrature channel la The signals from the outputs of the balanced modulators, resulting from the multiplication of the signals received at their inputs, are fed to the inputs of the adder 9. At the output of the adder, an information signal with a constant envelope and phase shift keying without phase jumps of 180 degrees is received.

где i=1, 2. На Фиг.3.б показана соответствующая информационная последовательность {ξ_n-1}, содержащая 200 элементов.Generator 1 generates a random digital sequence {ξ _n-1 } or {η _n-1 }. The generator can be made based on a microprocessor. In practice, the length of the chaotic sequence depends on the type of processor, and with ten digits held in the mantissa of the number, it exceeds 10,000 [4]. The control input of the generator 1 receives information modulating symbols λ _i . Figure 3.a shows the sequence {x _n } generated in the generator 1 according to the algorithm

where i = 1, 2. Figure 3b shows the corresponding information sequence {ξ _n-1 } containing 200 elements.

In the converter 2 form two digital chaotic information sequences subjected to digital-to-analog conversion. From the output of the generator 1 to the input of the Converter 2 receives one of the sequences {ξ _n-1 } or {η _n-1 }, formed by the algorithms:

or

Figure 3b shows the first of these sequences.

In transducer 2, the sequence {ξ _n-1 } or {η _n-1 } is converted into random chaotic information sequences {a _{n-1, i} }, {b _{n-1, i} } subjected to digital-to-analog conversion.

After digital-to-analog conversion in digital-to-analog converters 3, 4 using balanced modulators 5, 6, a generator of a carrier (subcarrier) oscillation 7, a phase shifter 8 by 90 degrees, and an adder 9, an output signal is generated:

or

where A ₀ is the amplitude of the carrier (subcarrier),

ω ₀ is the frequency of the carrier (subcarrier).

Figure 3c shows a timing diagram of the obtained digital chaotic information signal at λ ₁ = 2 (for m from 2500 to 5000), λ ₂ = 3 (for m from 5000 to 7500).

The ability to implement the method is confirmed by a software product specially designed to verify the operability of the method and study its characteristics.

Thus, using the proposed method, the problem of obtaining chaotic oscillations with a constant envelope without phase jumps of 180 degrees is solved.

Sources of information

1. Information technology in radio engineering systems: Textbook / Vasin VA, Vlasov IB, Egorov Yu.M. et al. Ed. I. B. Fedorova. - M .: Publishing house of MSTU. N.E.Bauman, 2003 .-- 672 p. (Ser. Informatics at a technical university).

2. Banquet V.L., Dorofeev V.M. Digital methods in satellite communications. - M .: Radio and communications, 1988 .-- 240 p.

3. Sklyar B. Digital communication. Theoretical foundations and practical application. 2nd edition. Per. from English - M .: Publishing House "William", 2003. - 1104 p.

4. Perov A.I., Plotnikov P.V., Perov A.A. Some aspects of the optimal estimation of the final sample of a discrete chaotic process // Radio Engineering, 2001, No. 7, - p.9-16.

5. Bespalov E.S. Labeled irregular number sequences. 51st scientific and technical conference MIREA. Collection of works. Part II Physics and mathematics. - M .: MIREA, 2002, - p.23-26.

Claims (2)

1. The method of generating a phase-shifted signal with a constant envelope, which consists in the fact that the digital sequence associated with information symbols is divided into two digital information sequences, digital-to-analog conversion of the obtained two sequences is carried out, one of the received signals is multiplied with the in-phase component of the carrier / subcarrier oscillation, and the other with the quadrature component of the carrier / subcarrier oscillation, and summarize the received signals, characterized in that before by dividing into two sequences, the digital sequence associated with information symbols is converted into the original information digital chaotic sequence by manipulating the control parameter of the generating recursive algorithm with information symbols; separation to obtain two digital information chaotic sequences is carried out by quadrature conversion of the original information digital chaotic sequence. 2. The method according to claim 1, characterized in that one of the two recurrence algorithms is

or

where n is the number of the element of the chaotic sequence, λ _i is the manipulated information control parameter, taking for the position number i = 1, 2, 3, 4 the values 2, 3, 4, 5, respectively, while receiving, respectively, the cosine or sinusoidal initial informational digital chaotic sequence

or

the transformation of which gives two informational digital chaotic sequences {a _{n-1, i} } and {b _{n-1, i} }, the elements of which are of the form a _{n-1, i} = cos (ξ _n-1 ) - for the in-phase channel and b _{n-1, i} = sin (ξ _n-1 ) - for the quadrature channel or a _{n-1, i} = cos (η _n-1 ) - for the in-phase channel and b _{n-1, i} = sin (η _n-1 ) - for the quadrature channel.

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