RU1789996C - Device for identificating information signals - Google Patents

Abstract

The invention relates to automation and computer engineering. Its use for visual analysis of the amplitude spectrum of signals and determining the type of their modulation allows to increase the accuracy of signal recognition. The device comprises a signal receiving and amplification unit 26, a radiation source 8, a collimator 9, a radiation modulator 10, a lens 14 and a photodetector 18. The goal is achieved by introducing signal phase doublers 5-7, radiation modulators 11-13, lenses 15-17 and photodetectors 19-21.4 ill.

Description

Xi 00

Yu

Yu ON

Figure 1

The invention relates to automation and computer engineering and can be used to visually analyze the amplitude spectrum of information signals and determine the type of modulation thereof.

Known information signal recognition devices are based on: converting the received signal into a digital code and using a covariance matrix; using as a sign the recognition of the Hermetic spectrum of transformations of the received signal; on the other hand of the recognition of the broadband uncertainty function; frequency and amplitude detection of the received signal, followed by comparison of the detection results with each other on determining the shape of the change in the received signal over a discrete time interval.

Of the known devices, the closest to the proposed is a device that implements a method of recognition of information signals. In the indicated device, a broadband uncertainty function is used as a sign of recognition of information signals with a large base.

However, the broadband uncertainty functions of some large-base information signals are not significantly different from each other. Therefore, this device does not provide reliable recognition of information signals with a large base. In addition, it does not allow one to evaluate the main parameters of the recognized information signal.

 An object of the invention is to increase the accuracy of signal recognition. This goal is achieved by the fact that the first-third signal phase doublers, as well as the second-fourth radiation modulators, the second-fourth lenses, and the second-fourth photodetectors, the input of the first phase doubler are connected to the output of the unit signal reception and amplification, a collimator, the i-th radiation modulator (I-2, ..., 4), the 1st lens and the i-th photodetectors are sequentially optically coupled, and the input of the 1st radiation modulator is connected to the output of the (I) -th signal phase doubler, and the output of the 1st photodetector It is 1-m data output device.

Structural diagram of the proposed device is presented in FIG. 1; possible waveforms are shown in FIG. 2; relative positioning of symbol frequencies of signals with multiple frequency manipulation is shown in FIG. 3; the law of phase change of the FSK signal is shown in FIG. 4.

The information signal recognition device comprises an antenna 1 connected in series, a mixer 3, the second input of which is connected to the output of the local oscillator 2, an intermediate frequency amplifier 4, a phase two multiplier 5, phase two multiplier b and phase two multiplier 7. In the path of propagation of the optical signal of the source 8, collimated by the collimator 9, radiation modulators 10-13 are installed in series. A lens 14 (15, 16, 17} is installed in the path of each diffracted light beam, and a photodetector 18 (19, 20, 21) is located in its focal plane. Antenna 1, local oscillator 2, mixer 3, and an intermediate frequency amplifier form a reception and amplification unit 26 A laser is used as the radiation source 8. Bragg cells are used as the radiation modulators 10-13.

. Recognition of information signals with a large base is based on the receipt and analysis of their amplitude spectra. Moreover, deformations of the amplitude spectrum of the received information signal when multiplying its phase by two, four and eight are used as recognition signs.

The device operates as follows: If an information signal with phase manipulation of the PSK is received at the input of the device, then it can be analytically written as follows;

Uc (t) Uc fct + p k (t) + pc, 0 t TC. where Uc, fc. pc, Tc - amplitude, carrier frequency, initial phase and signal duration:

p k (t) is the manipulated phase component that displays the law of phase manipulation, and pb (t) const at (k + 1) tn and can change abruptly at, i.e. at the borders between elementary premises (, 2, ..., N-1);

ty, N - the duration and number of chips that make up the signal duration TC (Tu).

If discrete information is transmitted from a single message source on a single carrier frequency, then it is advisable to use a single (binary) phase shift keying FMN-2, y (t.) 0d. For transmitting messages from two sources, the two-time phase manipulation of FMN-4, pk (t) TJ, is used. 7Я3

Moreover, from one source the phase is manipulated according to the 0- law, and from another - according to

the law of TJ - To send messages

from four sources, three-fold phase manipulation of FMN-8 is used,

(t) -0, f, generally, on one carrier frequency, messages from n sources can be transmitted simultaneously using n-fold phase shift keying. However, one-, two- and three-fold phase manipulations are expedient, which have found wide application in practice. A further increase in the phase-shift multiplicity is limited by the fact that the distance between the elementary signals is reduced and the noise immunity of the communication channel is substantially reduced.

The received FMN-2 signal from the antenna output is fed to the first input of the mixer 3, the second input of which supplies the voltage of the local oscillator 2:

Ur {thUr .cos (2L: fr t +), where Ur. fr. the amplitude, frequency and initial phase of the local oscillator voltage.

At the output of the mixer 3, voltages of combination frequencies are generated. Amplifier 4 isolates the voltage of only the intermediate (difference) frequency UnP (t) Unp fnpt + fb (t) + UEPR, 0t TC,

where Unp TJ- K Uc.Ur, (t) O.jr,

K is the transfer coefficient of the mixer;

.-fr - intermediate frequency;

9 ° np fa - fir - intermediate initial phase,

which sequentially arrives at the inputs of phase multipliers 5, 6 and 7 by two. At the approaches of the latter, stresses are formed

Unpi (t) UnP cos (4 n fnPt + 2 /) np),

UnP2 (t) Unp cos (8ttfnpt + 4 pnp),

Unp3 (COS (1 b; 7rfnpt + 8 Opr), 0 t TS

Since 2 pk (t 0, 2 n 4 (f (t) 0, 4l :; pk (t) 0,8 Jt,

ro is already absent in the indicated oscillations.

The optical signal is generated with the assistance of the laser 8 and the collimator 9. The spatial modulation of the optical signal by the information signal Unp (t) and its harmonics Unpi (t), Unp2 (t), b przM is carried out using Bragg cells 10-13, respectively. Each Bragg cell consists of a sound duct and hypersonic exciting piezoelectric plate of a piezoelectric transducer) made of a lithium niobate crystal, respectively, X and U-35 ° cut. This provides automatic Bragg angle adjustment and cell operation over a wide frequency range.

The voltages Unp (t), Unpi (t), Unp2 (t), and Unp3 (t) from the output of the intermediate-frequency amplifier 4 and phase multipliers 5, b, and 7 are supplied to the piezoelectric transducers of the Bragg cells 10-13. The Bragg cells are positioned so that the collimated optical signal passes through all the Bragg cells. Piezoelectric transducers transform the information signal Unp (t) and its harmonics Unpi (t), Unp2 (t) and Unp3 (t) into ultrasonic oscillations. (t) and its harmonics Unpi (t), Unp2 (t), Unp3 (t). It should be noted that only about 1/10 of the collimated optical signal is diffracted. On the propagation path of each diffracted beam of light, 71in for 14 (15, 16,

5 17), in the focal plane of which there is a photodetector 18 (19, 20, 21) to the output of which an indicator 22 (23, 24, 25) is connected as an oscilloscope indicator.

0 The spectrum width Afc of the QPSK-2 signal is determined by the duration rn of its elementary premises (). Whereas the spectrum width of the second Af2, fourth Afci and eighth harmonic of the signal Afe determines 5C the signal duration Tc (Af2-A). Therefore, when the phase is multiplied by two, four, and eight, the spectrum of the PSK-2 signal is collapsed N times, Afc Afc Afc. 1N

0 ZTFJ Ala and tRansF ° RmIRs into single spectral components. This circumstance is a sign of recognition of the FMn-2 signal. Amplitude spectra of the received FMN-2 signal

$ and its harmonic components are observed on the screens of indicators 22-25 (Fig. 2a).

If the input signal of the device receives an information signal with a two-phase phase ma0l: 3

nipulation FMn-4, y (t) 0, y, A, - l, then

at the output of the phase 5 multiplier by two, an FMN-2 signal y (t) 0, l, 2 Jt, 3 l is generated, and at the output of the phase 6 and 7 multipliers by two, the corresponding harmonic oscillations Unp2 (t) and Unp3 (t) are formed. In this case, the amplitude spectra of FMN-4 and FMN-2 signals are observed on the screens of indicators 22 and 23, and single spectral components are observed on the screens of indicators 24 and 25 (Fig. 26).

If the device receives FMN-8

g / h. 5 37t signal (pk (t) U, 2p tu- 3 D 2 3

then at the outputs of the multipliers of phase 5 and b phase two FMN-4 and FMN-2 signals are generated, and at the output of the multiplier 7 phase two forms harmonic oscillation Unp3 (t). In this case, the amplitude spectra of FMn-8, FMn-4 and FMn-2 signals are observed on the screens of indicators 22, 23 and 24, and a single spectral component is observed on the screen of indicator 25 (Fig. 2c). This is precisely the situation characteristic of the PSK-8 signal.

Among the information signals with frequency manipulation (FMN), signals with minimal frequency manipulation (FMN-2), with binary frequency manipulation (FMN-3) and with twisted frequency manipulation FMN-5 (Fig. 3) are widely used.

The complex FSK-2 signal is analytically described by the expression

Uc (t). Uc to fcp t + p (t) + pc, 0 t Tc where p (t) is the time-varying phase function (Fig. 4) ;.

, f 1 -f f2 fcp A average signal frequency;

f 1 tsr-1/4 gp - signal frequency corresponding to the symbol

f2 fcp + 1/4 gp - signal frequency corresponding to the + G symbol.

The phase function p (t) can be represented by the expression

p (t) 2tth / Y bkg (r-kr) dr,

-ooT where bk is a sequence of information symbols {-1, + 1}; .

h-x - frequency deviation index;

1

9 (t) f

1 About

gp, t Ј 0, gp

t & 0, gp.

The phase function at each symbol interval rn varies linearly in time. During one symbol interval, the phase incursion is +/2.

If an FMN-2 signal is input to the device, then an FMN signal with an index of frequency deviation is generated at the output of a phase 5 multiplier by two. In this case, its amplitude spectrum is transformed into two spectral components at frequencies 2fi and 2f2. At the outputs of multipliers of phase 6 and 7 into two, two spectral

components at frequencies 4ft, 4f2 and 8fi, 8f2, respectively (Fig. 2d).

If an FMN-3 signal is input to the device, then three spectral components at the frequencies 4fi, 4fcp, 4fa and 8fi, 8fcp, 8f2 are formed at the outputs of phase 6 and 7 multipliers the solid spectrum is transformed into three spectral components (Fig. 2e). At the output of the phase 5 multiplier by two amplitude spectrum, the FSK-3 signal is transformed into another continuous spectrum since.

Thus, continuous amplitude spectra will be observed on the screens of the indicators 22 and 23 (Fig. 2e).

If an FMN-5 signal is input to the device, then at the output of the phase 7 multiplier by its two continuous spectrum it is transformed into five spectral lobes with peak values at frequencies 8fi, 8f3, 8fcp, 8f4 and 8f2. At the outputs of multipliers of phases 5 and 6,

two continuous spectrum of the FMN-5 signal is transformed into other continuous amplitude spectra, as in this case. Thus, on the screens of indicators 22, 23 and 24, continuous amplitude spectra will be observed, and on the screen of indicator 25, five solid petals (Fig. 2e). It is this situation that is a sign of recognition of the FSK-5 signal.

If the input of the device receives an information signal with linear frequency modulation (LFM)

Uc (t) Uc COS (2 7G fc t -f H-pc),

About t TCv

where fc is the initial signal frequency; A fa

Y - rate of change frequency

inside the pulse

A fa - frequency deviation: then it transfers the frequency converter to the intermediate frequency

Unp (t)

Unp С08 (2л: fnp t -f Л у t2 + рпр), 0 t Тс,

The voltage Unp (t) is extracted by the intermediate frequency amplifier 4 and fed to the Bragg cell 10 and to the input of the phase 5 multiplier by two, at the output of which an LFM

Unpi (t

Unp cos (4 L fnp t -f 2 L y t2 4--2 0f, p), 0 t Tc

which arrives at the Bragg cell 11. Since the duration Tc of the LFM signals at the fundamental and doubled intermediate frequencies is the same, a 2-fold increase in y occurs due to a 2-fold increase in deviation

frequency A fd. It follows that the spectrum width of the LFM signal at twice the intermediate frequency is 2 times greater than its spectrum width at the fundamental intermediate frequency Afc (A f2 2 Afc).

Similarly, at the outputs of phase 6 and 7 multipliers by two, the width of the spectrum of the LFM signal increases by 4 and 8 times. Therefore, on the screen of the indicator 22, the amplitude spectrum of the LFM signal is visually observed and analyzed, and on the screens of the indicators 23,24 and 25, the amplitude spectra of the LFM signals are observed whose spectrum widths are 2, 4 and 8 times the width

Claims (1)

The formula is invented. A device for recognizing information signals, comprising a signal reception and amplification unit and serially optically coupled radiation source, a collimator, a first radiation modulator, the control input of which is connected to the output of the signal reception and amplification unit, a first lens and a first photodetector, the output of which is the first information output of the device, characterized in that, in order to increase the accuracy of signal recognition, 7000 mWj) tgsthgl) (Yiddish) Igoyma) st.2 0 5 the initial LFM signal (Af2 2 Afc, Afy - 4 Afc, Afc) (Fig. 2g). This is a sign of the recognition of the LFM signal. Thus, the proposed device in comparison with the prototype provides an increase in the reliability of visual recognition and evaluation of the received information signal with a large base. This is achieved by using the amplitude spectrum and its deformations as indicators of recognition by multiplying the phase of the received signal by two, four and eight. The first and third signal phase doublers, as well as the second and fourth radiation modulators, the second and fourth lenses, and the second and fourth photodetectors are introduced in series; the input of the first phase doubler is connected to the output of the signal reception and amplification unit, collimator, and the 1st modulator radiation (, ..., 4), the 1st lens and the f-th photodetector are optically connected in series, the input of the 1st radiation modulator is connected to the output of the (1-1) -th signal phase doubler, and the output of 1- The first photodetector is the 1st information output of devices. x4 and. K and) ; AND ± 4TI S. & f jL 4Tu. ChMn-5 -f J