RU2285936C2 - Method for detecting sources of radio radiations with leap-like frequency alternation - Google Patents

Abstract

FIELD: radio engineering, possible use in passive radio control systems for detecting and determining parameters of a set of transmitters with leap-like frequency alternation, simultaneously present in current receipt frequencies band.

SUBSTANCE: in accordance to method, additional signs are used for identification of signals with leap-like frequency autocorrelation function and selective functions of durations distribution and value of frequency leaps of elements of signal frequency-time matrix, preliminarily selected from input flow of signals with use of spatial mutual correlation connections between separate frequency-time signal components.

EFFECT: increased efficiency of detection of determining of parameters frequency-time matrix, describing rule of leap-like frequency alternation; average signal energy; most likely value of durations of separate radiations; speed of leap-like frequency alternation, azimuth and elevation of transmitter.

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Description

The invention relates to radio engineering and can be used in passive radio monitoring systems for detecting and determining parameters (time-frequency matrix, signal energy, rate of frequency hopping, azimuth and elevation angle) of a plurality of frequency hopping transmitters (SICH) simultaneously falling into the current reception frequency band.

With the advent and improvement of communication systems, locations, control, and others, using signals with WMS, the radiated power of which is pseudo-randomly distributed in the time-frequency domain, problems arise of their effective radio monitoring.

A known method of detecting radio frequency sources with WMS [1], including receiving a signal with a broadband radio receiver, transferring to an intermediate frequency and dividing the signal into L adjacent frequency channels using a “comb” of bandpass filters, estimating the received signal power in each frequency channel, comparing the received value power with a predetermined threshold for generating a binary signal, the pulse of which corresponds to exceeding the threshold, and the pause between pulses when not exceeding, total formation of the generated binary signals in each of two adjacent groups by L / 2 channels and comparing the total signals of these two groups to determine the presence of a signal with WMS by means of low-pass filtering in a band that is consistent with the expected switching frequency of the signal from WMS.

This method, as a sign of the presence of a signal with a WMS, uses the intensity of the flow of moments of a change in signal states (radiation and the pause between emissions) in the analyzed frequency band and provides detection of a signal with a WMS only if the a priori knowledge of the frequency switching frequency. In addition, from the maximum possible spatial-frequency-time information about the signal in this method, only the time-frequency information is used, which leads to a decrease in the detection efficiency of radio frequency sources with WMS. Moreover, this method does not provide a determination of the number of transmitters with WMS operating simultaneously in the reception band and their parameters.

A better method for detecting sources of radio waves with a frequency change [2], adopted as a prototype and including:

1. Reception of temporary signals x _n (t) by the reference antenna and all antennas included in the N-element array, where n = 0, 1 ... N is the antenna number;

2. Synchronous conversion of the received signals x _n (f) into digital signals x _n (z), where z is the number of time reference signal;

сигнала каждой антенны, где q - номер временного отрезка преобразования, 1≤q≤Q, a l - номер частотного канала, 1≤l≤L.3. Time-shifting conversion of digital signals x _n (z) for reconstruction with a given discreteness in time and frequency of complex spectral density

the signal of each antenna, where q is the number of the conversion time interval, 1≤q≤Q, al is the number of the frequency channel, 1≤l≤L.

In other words, the input signals at each time interval are divided into frequency channels.

(N+1)-мерных векторов спектральных плотностей

с элементами

;As a result of this operation, a time-frequency matrix (FMM) is formed

(N + 1) -dimensional spectral density vectors

with elements

;

и спектральных плотностей остальных антенн

для определения комплексной дискретной радиоголограммы

сигнала, зарегистрированного в q-м временном интервале.4. Multiplication at each discrete frequency l of the complex conjugate spectral density of the reference antenna

and spectral densities of the remaining antennas

for determining a complex discrete radio hologram

signal recorded in the qth time interval.

комплексных дискретных радиоголограмм

, представляющих собой N-мерные векторы с элементами

;This operation can be considered as restoration

complex discrete radio holograms

representing N-dimensional vectors with elements

;

5. Determination of the complex coefficients of spatial mutual correlation of the radio hologram obtained in each frequency channel with the radio holograms obtained in the remaining frequency channels of the reception band in the qth time interval.

, элементы которой описываются

, где

- нормированные элементы вектор-строки

с элементами

, а

- номер частотного канала, 1≤

≤L,

≠

. При этом использовано обозначение скалярного произведения и нормы N-мерных комплексных векторов в виде

As a result of this operation, a block vector row is formed of complex cross-correlation coefficients

whose elements are described

where

- normalized elements of a row vector

with elements

, but

- number of the frequency channel, 1≤

≤L

≠

. In this case, the notation of the scalar product and the norm of N-dimensional complex vectors is used in the form

с порогом и объединение сигналов с частотами, на которых превышен порог, i-й сигнал, который идентифицируется как обнаруженный одночастотный сигнал с полосой частот δƒ_i, если полоса δƒ_i, непрерывна, или как многочастотный сигнал с полосой частот δƒ_i, если полоса δƒ_i дискретно непрерывна, принадлежащий одному передатчику с полосой частот δƒ_i, где i=1...Р, а Р - число обнаруженных передатчиков, из числа одновременно попадающих в текущую полосу приема на отдельном временном интервале;6. Comparison of the modules of the correlation coefficients

with a threshold and combining signals with frequencies at which the threshold is exceeded, the i-th signal, which is identified as a detected single-frequency signal with a frequency band δƒ _i , if the band δƒ _i , is continuous, or as a multi-frequency signal with a frequency band δƒ _i , if the band δƒ _{i is} discrete continuous, belonging to one transmitter with a frequency band δƒ _i , where i = 1 ... P, and P is the number of transmitters detected, from the number simultaneously falling into the current reception band in a separate time interval;

где а_l - двоичные числа (0, 1), отличные от нуля в полосе частот δƒ_i,

- индекс, соответствующий средней частоте сигнала с шириной спектра δƒ_i;7. Averaging the radio hologram of the _ith signal in the frequency band δƒ _i and obtaining the averaged radio hologram

where a _l are binary numbers (0, 1) other than zero in the frequency band δƒ _i ,

- the index corresponding to the average frequency of the signal with the width of the spectrum δƒ _i ;

i-го сигнала для определения реальной части его двумерного комплексного углового спектра

где d_n(m, k) - диаграмма направленности n-й антенны, m=0...М-1 - текущий номер узла сетки по азимуту, М - число узлов по азимуту, k=0...К-1 - текущий номер узла сетки наведения решетки по углу места, К - число узлов по углу места, а

- модельная фазирующая функция, зависящая от конфигурации антенной решетки;8. Using the averaged radio hologram

ith signal to determine the real part of its two-dimensional complex angular spectrum

where d _n (m, k) is the radiation pattern of the nth antenna, m = 0 ... M-1 is the current number of the grid node in azimuth, M is the number of nodes in azimuth, k = 0 ... K-1 - the current node number of the grid pointing the lattice in elevation, K is the number of nodes in elevation, and

- model phasing function, depending on the configuration of the antenna array;

двумерного комплексного углового спектра.9. Determination of azimuthal and elevation bearings of the i-th signal detected in the reception band, to the maximum of the real part

two-dimensional complex angular spectrum.

The disadvantages of the prototype method include:

- low detection efficiency of signals with WMS, simultaneously falling into the current frequency band of reception;

- low efficiency of identifying the signal from the WMS and measuring its address parameters (bearing and time-frequency matrix of the frequency switching), providing selection of its signal on the receiving side.

The low detection efficiency is due to the fact that the prototype method provides the localization of a priori unknown signals only in the frequency domain. At the same time, a signal transmitter with WMS distributes the radiated power in a two-dimensional, time-frequency, region. In this regard, due to inconsistency in reception, signal power losses are observed when signals with WMS are detected.

The low efficiency of identifying the signal from the WMS and measuring its parameters is due to the fact that the time-frequency frequency switching matrix is not determined. Localization of unknown signals only in the frequency domain leads to identification errors of signals with WMS, since the sign of the presence of frequency-distributed maxima is inherent in any multi-frequency signal. In addition, as a result of cross-correlation operations of single-frequency radio holograms, all frequency components of the reception band having close amplitude-phase distributions or, equivalently, having close angles of arrival, are identified as a signal belonging to one transmitter. If there are several transmitters with the same angle of arrival, identification errors also occur.

Improving the efficiency of detection and determination of parameters of sources of radio emissions from WMS when using the prototype method can be achieved in several well-known ways [2]:

1. An increase in the base of the antenna array.

2. An increase in the duration of the signal registration interval to increase the signal-to-noise ratio due to the accumulation and separation of the signal against the background of noise.

However, these paths do not radically solve the problem, since they only partially increase the efficiency of detection and identification of signals with WMS due to improved resolution in the correlation detection of several signals and increase the signal-to-noise ratio of only that part of the signal with WMS that falls within one transformation time interval .

The technical result of the invention is to increase the efficiency of detection and determination of parameters (time-frequency matrix describing the law of frequency hopping; average signal energy; the most probable value of the duration of individual emissions; speed of the frequency hopping, azimuth and elevation of the transmitter) of radio emissions from multiple transmitters with WMS, simultaneously falling into the current reception frequency band.

An increase in the efficiency of detection and determination of parameters of sources of radio waves with WMS is achieved by using instead of one-dimensional (frequency) two-dimensional (time-frequency) correlation localization of signals, as well as by using additional signs of identification of signals from WMS: invariance of the duration and repetition period of individual emissions and the pseudorandom law of frequency jumps . Additional features of signals with WMS are extracted by reconstructing a two-dimensional autocorrelation function (ACF) and selective duration distribution functions (DFD) and frequency jumps (FRF) of the elements of the signal time-frequency matrix previously extracted from the input signal stream using spatial cross-correlation relationships between the individual frequency -time components of the signal.

The technical result is achieved by the fact that in the method of detecting radio frequency sources with frequency-hopping (SICH), which includes receiving and synchronizing digitally the signals received by the reference antenna and all antennas included in the N-element array, time-shifting conversion of digital signals for restoration with a given discreteness in time and frequency of the complex spectral density of the signal of each antenna, the multiplication of the complex conjugate spectral density of the reference ant data and spectral densities of the remaining antennas for reconstructing the time-frequency matrix (FWM) of complex discrete radio holograms, according to the invention form a block FWM of the complex correlation coefficients of the reconstructed radio holograms, compare the modules of the correlation coefficients with a threshold, combine the signals of the FWM elements at which the threshold is exceeded, in i- the detected signal and form a binary time-frequency matrix (BCHM) of its localization, restore the two-dimensional autocorrelation function (ACF) and selective The functions of the distribution of durations (DFD) and frequency jumps (DFPS) of the HFM elements of each i-th signal are determined by the degree of concentration of the ACF and HFD near their maximum values, as well as by the degree of fuzziness of the FFD in frequency, the presence of a source with MIS in the i-th signal , which is preliminarily identified as a single source with WMS or that is part of a group of sources of other classes, and also find the maximum probable value of the duration of its emissions from the maximum RDF, statistically related electrons are extracted from the I-th signal of the ith signal measures of the measured duration to obtain a BHFM localization and identification of radiation from a single source with WMS, average the single-frequency radio holograms in the selected region of localization of a single source with WMS, convert the resulting multi-frequency radio hologram according to the well-known algorithm for reconstructing the image of the two-dimensional angular spectrum, from which the source and azimuth coordinates of the source are determined from SICH.

The operation of the method is illustrated by drawings:

Figure 1. Block diagram of a device for detecting radio frequency sources with frequency hopping.

Figure 2. An example of a time-moving reconstruction of the complex spectral density of signals.

Figure 3. The structure of the block matrix of correlation coefficients.

Figure 4. Binary time-frequency matrices describing time-frequency regions of signal localization:

a) transmitter with WMS;

b) a transmitter with WMS against the background of a continuously operating transmitter with a fixed radiation frequency.

Figure 5. Autocorrelation functions of binary time-frequency matrices and their cross sections:

a), b), c) - a transmitter with WMS;

d), e), f) - transmitter with WMS against the background of a constantly operating transmitter with a fixed radiation frequency.

6. Selective functions of the distribution of duration and frequency jumps of radiation:

a), b) - transmitter with WMS;

c), d) - a transmitter with WMS against the background of a constantly operating transmitter.

According to the proposed method:

1. Receive temporary signals x _n (t) by the reference antenna and all antennas included in the N-element array, where n = 0, 1 ... N is the antenna number;

2. Synchronously convert the received signals x _n (t) into digital signals x _n (z), where z is the number of time reference signal;

сигнала каждой антенны, где q - номер временного отрезка преобразования, 1≤q≤Q, a l - номер частотного отсчета, 1≤l≤L.3. Restore the digital spectral signals x _n (z), moving in time, with a given discreteness in time and frequency, the complex spectral density

the signal of each antenna, where q is the number of the conversion time interval, 1≤q≤Q, al is the number of the frequency reference, 1≤l≤L.

(N+1)-мерных векторов спектральных плотностей

с элементами

.As a result of this operation, a time-frequency matrix (FMM) is formed

(N + 1) -dimensional spectral density vectors

with elements

.

возможно применением гребенки цифровых фильтров или, что, как правило, более эффективно с вычислительной точки зрения, алгоритма БПФ, реализующего дискретное Фурье-преобразование q-го временного отрезка сигнала каждой антенны

, где F_t{...} - оператор прямого дискретного Фурье-преобразования по времени.Spectral Density Recovery

it is possible to use a comb of digital filters or, which, as a rule, is more efficient from a computational point of view, an FFT algorithm that implements a discrete Fourier transform of the qth time segment of the signal of each antenna

, where F _t {...} is the direct discrete Fourier transform operator in time.

In other words, at this stage, the input signals are divided with a given discreteness in time and frequency into frequency and time channels. To ensure the required detail in the reconstruction of the spectral density from time, the qth and (q + 1) th segments of the signal conversion are selected with the necessary overlap.

Figure 2 presents a diagram of a time-moving reconstruction of the complex spectral density of the signal;

и спектральных плотностей остальных антенн

восстанавливают ЧВМ

комплексных дискретных радиоголограмм

представляющих собой N-мерные векторы с элементами

4. Multiplication of the complex conjugate spectral density of the reference antenna

and spectral densities of the remaining antennas

restore hvm

complex discrete radio holograms

representing N-dimensional vectors with elements

размерностью Q²×L². Для этого нормируют радиоголограммы

используя которые формируют частотно-временную матрицу нормированных радиоголограмм

и элементы блочной матрицы

в виде скалярного произведения

которое в развернутой форме имеет вид

где 1≤q'≤Q, 1≤l'≤L, l≠l', q≠q'.5. Form a block computer frequency complex complex correlation coefficients of reconstructed radio holograms

dimension Q ² × L ² . For this, radio holograms are normalized

using which form the time-frequency matrix of normalized radio holograms

and block matrix elements

as a scalar product

which in expanded form has the form

where 1≤q'≤Q, 1≤l'≤L, l ≠ l ', q ≠ q'.

The structure of the block matrix of correlation coefficients is presented in figa, and the structure of its elements is shown in figb;

) с порогом объединяют сигналы элементов ЧВМ, на которых превышен порог, в i-й сигнал, где i=1...P, P - число обнаруженных сигналов, отличающихся угловыми координатами, и формируют бинарную (двоичные числа а_q,l: 1 - соответствует наличию излучения, а 0 - соответствует отсутствию излучения) частотно-временную матрицу (БЧВМ) B_i(q, l) его локализации, описывающую закон изменения частоты сигнала во времени.6. Comparison of the modules of the correlation coefficients (matrix elements

) the threshold combines the signals of the elements of the HFM, at which the threshold is exceeded, into the i-th signal, where i = 1 ... P, P is the number of detected signals that differ in angular coordinates, and form a binary (binary numbers a _{q, l} : 1 - corresponds to the presence of radiation, and 0 - corresponds to the absence of radiation) the time-frequency matrix (MFW) B _i (q, l) of its localization, which describes the law of the frequency of the signal in time.

фактически сводится к корреляции пространственных амплитудно-фазовых распределений восстановленных спектральных плотностей, однозначно связанных с угловыми координатами приходящих сигналов, БЧВМ i-го сигнала может описывать частотно-временную область, занимаемую спектром сигнала одиночного передатчика или спектрами сигналов нескольких передатчиков с совпадающими угловыми координатами. Отсюда следует, что i-й сигнал в общем случае может быть групповым сигналом и содержать сигналы нескольких передатчиков, например, входящих в узел связи и функционирующих в различных режимах (режим СИЧ, непрерывное излучение на фиксированной частоте с различными видами узкополосной и широкополосной модуляции, импульсное излучение с ЛЧМ и т.д.).Given that the formation of correlation coefficients

in fact, it comes down to correlation of spatial amplitude-phase distributions of the reconstructed spectral densities, which are uniquely associated with the angular coordinates of the incoming signals, the I-signal MFD can describe the time-frequency domain occupied by the signal spectrum of a single transmitter or the signal spectra of several transmitters with matching angular coordinates. It follows that the i-th signal in the general case can be a group signal and contain the signals of several transmitters, for example, entering a communication node and operating in various modes (WMS mode, continuous radiation at a fixed frequency with various types of narrowband and broadband modulation, pulse radiation with chirp, etc.).

Examples of a single-transmitter BCHM with a WICH and a BCHM of several transmitters with matching angular coordinates (a transmitter with a WMS and a transmitter emitting a signal at a fixed frequency) are shown in FIGS. 4a and 4b, respectively.

Thus, at this stage, the input signal stream is separated by a spatial attribute. In the analyzed time-frequency domain, all signals differing in angular coordinates will be detected and highlighted. In addition, the time-frequency regions occupied by each ith, generally group, signal combining the signals of one or more transmitters with the same angular coordinates will be restored.

To identify the transmitter signals from the WMS, which are part of the i-th detected signal, subsequent processing is necessary to identify signs characterizing the radiation from the WMS.

The operations of the subsequent signal processing are based on the fact that the individual frequency elements of the WMS signal are of equal duration and are emitted at equally spaced time instants at different frequencies distributed in a pseudo-random manner.

In this regard, for an ideal signal with WMS, the two-dimensional autocorrelation function (ACF) of the BFM elements should have the form close to the two-dimensional δ-function, the selective distribution function of the durations (FRE) of the BFM elements should have the form close to the one-dimensional δ-function, and the selective the distribution function of frequency jumps (PSF) of the elements of the HFM should be close to the function of uniform distribution;

7. Restore the two-dimensional autocorrelation function (ACF) and the sample distribution function of the durations (DFD) and frequency jumps (FERF) of the elements of the HFMB _i (q, l) of the i-th signal.

или, что более эффективно, с применением быстрого алгоритма на основе БПФ.The autocorrelation function can be restored by direct calculations by the formula

or, more efficiently, using a fast FFT algorithm.

Examples of two-dimensional ACF and selective FRD and FFCH of the HFM of the transmitter signal from the WMS and HFM of the group signal of several transmitters are presented in FIG. 5 and 6, respectively;

8. Determine by the degree of concentration of ACF and RDF near their maximum values and by the degree of fuzziness of the PSF by the frequency of the presence of a source with WMS, which is previously identified as a single source or as part of a group of sources of other classes.

The degree of ACF concentration near its maximum value or, which is the same, the proximity of the ACF form to the shape of a two-dimensional δ-function, can be established by various algorithms. For example, the following algorithm may be used:

- get a slice of two-dimensional ACF at a given threshold level from the maximum of the ACF (see fig.5b and fig.5d). Modeling established that the threshold level should be chosen equal to 0.25-0.3;

- analyze the shape of the slice, and if there is a slice in the form of a single ellipse, the dimensions of which satisfy the conditions Δτ≤δ _τ and Δρ≤δ _ρ , a decision is made on the presence of a signal with WMS, where Δτ is the width of the ellipse in the time domain, Δρ is the width of the ellipse in frequency domain, δ _τ and δ _ρ are threshold values selected on the basis of the characteristic parameters of individual emissions of the signal with WMS (see Fig.5B and Fig.5E).

The proximity of the selective FRD to the one-dimensional δ-function can be determined by the presence of a single maximum exceeding the threshold (see Fig. 6a and Fig. 6c). The threshold value is selected by the probability level equal to 0.5.

The proximity of the sample PSF to a uniform distribution can be determined by the presence of several (for example, three or more) maxima that exceed the threshold (see Fig.6b and Fig.6d). The threshold value is selected at the level of 0.5 of the maximum value of the PSF;

9. Find the most probable value of the duration of the radiation of the i-th signal corresponding to the local maximum of the selective FRD;

10. Statistically related elements of measured duration are extracted from the I-signal signal of the ith signal, which automatically generates the B-frequency computer (binary numbers b _{q, l} ) of radiation localization of the j-th transmitter with WMS, where j = 1 ... J, J is the number of detected transmitters operating in the WMS mode.

In order to extract statistically related elements from the I-signal of the ith signal, it is possible to form a time gate along the trailing edge of pulses and select those pulses whose leading edge will fall into the strobe. It is also possible to form the total radiation flux by projecting the BFM onto the time axis, and select adjacent pulses of equal duration.

Temporary gating or the formation of a total stream of states provides the allocation of time-frequency characteristics of the signal with WMS. This is due to the fact that the individual elements of the signal with WMS have a fixed duration and are transmitted at different frequencies at consecutive times. In this regard, the projection of a BFM onto the time axis in the absence of noise and interference leads to the formation of a total pulse stream with fixed durations and a repetition period. The duration of pauses between pulses is also the same and, as a rule, does not exceed 10% of the pulse duration.

Given the short duration of pauses between time-adjacent emissions at individual frequencies, the duration of the emissions is used to obtain an estimate of the period and, accordingly, an estimate of the rate of the frequency-hopping transmitter with WMS.

At this stage, they also get an estimate of the average signal energy of the j-th transmitter with WMS according to the formula

;11. Averaged single-frequency radio holograms in the selected area of localization of radiation of the j-th transmitter with WMS and get the averaged multi-frequency radio hologram

;

по известному алгоритму для восстановления изображения двумерного углового спектра, по которому определяют угломестные и азимутальные координаты j-го передатчика с СИЧ.12. Transform the resulting multi-frequency radio hologram

according to the well-known algorithm for reconstructing an image of a two-dimensional angular spectrum, which determines the elevation and azimuth coordinates of the j-th transmitter with WMS.

The image can be reconstructed using the classical beamforming algorithm described in [2], or algorithms providing increased resolution, for example, algorithms based on the analysis of eigenvalues, MUSIC (multiple signal classification) and EV (eigenvector) [3], or algorithms based on the principles of regularization [4].

Thus, after repeating the signal processing operations in clauses 7-12, of all the signals (i = 1 ... P) detected at stages 1-6, all (j = 1 ... J) transmitters with WMS will be identified, and they will also be their energy and address parameters were restored. In other words, for each j-th transmitter with WMS, the following will be determined: the time-frequency matrix (binary numbers b _{q, l} ), which describes the law of frequency hopping; average signal energy; the most probable duration of individual emissions; frequency hopping rate, azimuth and elevation angle of the transmitter.

The device in which the proposed method is implemented includes a series-connected antenna system 1, (N + 1) -channel frequency converter 2, (N + 1) -channel analog-to-digital converter (ADC) 3, calculator 4, correlation block 5, block detection 6, identification unit 7, coordinate measurement unit 8 and display unit 9. The second input of block 8 is connected to the output of block 5.

The antenna system 1 contains a reference antenna with the number n = 0 and N antennas with the numbers n = 1 ... N, combined in a grid. The antenna array can be of any spatial configuration: flat rectangular, flat annular or three-dimensional, in particular conformal.

Frequency converter 2 is made with a common local oscillator and with a bandwidth of each channel many times greater than the spectrum width of a single transmitter signal. The common local oscillator provides multi-channel coherent signal reception, which is the main condition for interferometric (holographic) registration of complex transmitter signals.

If the resolution and speed of the ADC are sufficient for direct analog-to-digital conversion of the input signals, such as, for example, when constructing a radio image in the KB range, then a frequency-selective bandpass filter and amplifier can be used instead of converter 2. In other words, the analog part of the device that implements the proposed method can be built on the principle of direct amplification.

In addition, the transducer 2 provides calibration according to the internal signal source. In this case, a noise generator can be used, the output of which can also be connected instead of all antennas for periodic calibration of channels. This is necessary due to the fact that the restoration of discrete radio holograms, complex correlation coefficients of reconstructed radio holograms and radio images requires the fulfillment of two conditions typical for interferometric processing:

- the exact (with accuracy to small fractions of the minimum wavelength of the working frequency range) coordinates of the antenna elements of the array relative to the reference element must be known;

- phase incursions in feeders should be taken into account, if they differ in electric length, and the non-identity and time variation of the frequency characteristics of the complex transmission coefficients of the receiving paths.

The first of these conditions is easily satisfied by simple measurements of the geometry of the lattice. The second condition can be fulfilled by aligning the characteristics of the feeders and paths at the stage of manufacturing the device or by special calibration procedures for a special internal or external source of the signal during its operation, which is implemented in the proposed device.

Blocks 7 and 8 can be made in single-channel or multi-channel versions. The multichannel version provides maximum performance due to parallel processing of all signals detected in the reception band (i = 1 ... P) and identified as WMS (n = 1 ... J).

The device operates as follows.

Multi-frequency time signals x _n (t) from the output of the antenna system 1 from the reference antenna element with the number n = 0 and from all the antennas with the numbers n = 1 ... N included in the array are fed to the inputs of the converter 2 in the reception band many times the spectrum width of a single transmitter signal, and coherently transferred to a lower frequency.

Using ADC 3, the frequency-converted signals x _n (t) are synchronously converted to digital signals x _n (z), where n is the number of the antenna element, az is the time reference number of the signal.

сигнала каждой антенны, где q - номер временного отрезка преобразования, 1≤q≤Q, a l - номер частотного канала, 1≤l≤L. Для обеспечения требуемой детальности восстановления спектральной плотности по времени q-й и (q+1)-й отрезки преобразования сигнала выбираются с необходимым перекрытием. Восстановление спектральной плотности

выполняется с применением алгоритма БПФ, реализующего дискретное Фурье-преобразование q-го временного отрезка сигнала каждой антенны.In the calculator 4, the complex spectral density is reconstructed by a time-shifting conversion of digital signals x _n (z) with a given discreteness in time and frequency

the signal of each antenna, where q is the number of the conversion time interval, 1≤q≤Q, al is the number of the frequency channel, 1≤l≤L. To ensure the required detail in the reconstruction of the spectral density from time, the qth and (q + 1) th segments of the signal conversion are selected with the necessary overlap. Spectral Density Recovery

performed using the FFT algorithm that implements the discrete Fourier transform of the qth time segment of the signal of each antenna.

As a result of this operation, a time-frequency matrix (FWM) of (N + 1) -dimensional spectral density vectors is formed. The spectral densities obtained in calculator 4 are transmitted to block 5.

In correlation block 5, by multiplying the complex conjugate spectral density of the reference antenna and the spectral densities of the remaining antennas, the FM of single-frequency complex discrete radio holograms is reconstructed. Radio holograms are transmitted to block 8.

In addition, the radio holograms are normalized, after which the time-frequency matrix of normalized radio holograms and the elements of the block frequency modular complex correlation coefficients of the reconstructed radio holograms, which enter block 6, are formed.

In block 6, by comparing the modules of the correlation coefficients with the threshold, the signals of the HFM elements, at which the threshold is exceeded, are combined into the i-th detected signal, and a binary time-frequency matrix is formed (binary numbers _{q, l} ), which describes the law of the frequency signal in time, where i = 1 ... P, P is the number of detected signals that differ in angular coordinates.

In block 7, parallel processing of all i = 1 ... P detected signals is performed. Moreover, using the binary time-frequency matrices obtained in block 6 for each i-th signal:

- the two-dimensional autocorrelation function and selective distribution functions of the durations and frequency jumps of the elements of the binary time-frequency matrix are restored;

- a decision is made about the presence of a signal with WMS if three conditions are simultaneously met:

a slice shape of a two-dimensional autocorrelation function at a given threshold level has an ellipse shape with dimensions satisfying the conditions Δτ≤δ _τ and Δρ≤δ _ρ ;

in the sampling function of the distribution of durations, there is a single maximum exceeding the threshold;

in the selective distribution function of the frequency jumps, there are more than three maxima that exceed the threshold;

- the most probable value of the radiation duration of the i-th signal is found, corresponding to the local maximum of the sample duration distribution function;

- statistically related elements of measured duration are extracted from the binary time-frequency matrix of the ith signal, that is, a binary time-frequency matrix is formed (binary numbers b _{q, l} ), which describes the law of the frequency-hopping transmitter of the j-th transmitter with WMS, where j = 1 ... J, J is the number of detected transmitters operating in the WMS mode. By analyzing the obtained binary matrix, estimates of the period and rate of the frequency-hopping transmitter of the jth transmitter with WMS are found.

, полученные в блоке 5, и бинарная частотно-временная матрица (двоичные числа b_{q, l}) j-го передатчика с СИЧ, полученная в блоке 7. Для каждого j-го передатчика с СИЧ:In block 8, parallel processing of all j = 1 ... J detected transmitters operating in the WMS mode is performed. In this case, single-frequency radio holograms are used

obtained in block 5 and the binary time-frequency matrix (binary numbers b _{q, l} ) of the j-th transmitter with WMS, obtained in block 7. For each j-th transmitter with WMS:

- get an estimate of the average energy E _j signal;

;- single-frequency radio holograms are averaged in the selected localization region of the transmitter signal to obtain an averaged multi-frequency radio hologram

;

по известному алгоритму для восстановления изображения двумерного углового спектра, по которому определяются угломестные и азимутальные координаты j-го передатчика.- the radio hologram is converted

according to the well-known algorithm for reconstructing an image of a two-dimensional angular spectrum, according to which the elevation and azimuth coordinates of the jth transmitter are determined.

In block 9, to increase the information content, the parameters of the detected transmitters with WMS are displayed, including the time-frequency matrix of the emitted signal and its energy, the frequency hopping rate, as well as the azimuth and elevation angle of the transmitter using a geographical map of the area.

Thus, the method for detecting sources of radio waves with WMS through the use of additional features of signals from WMS extracted due to the restoration of the two-dimensional autocorrelation function and selective distribution functions of the durations and frequency jumps of the elements of the time-frequency matrix of the signal previously extracted from the input signal stream using mutual correlation relationships between the individual time-frequency elements of the signal, allows to increase:

- the efficiency of detection and discrimination of multiple signals simultaneously falling into the current frequency band of reception;

- the efficiency of identifying signal sources from WMS and measuring their address and energy parameters (frequency-time matrix of the emitted signal and its energy, frequency hopping rate, transmission duration, azimuth and transmitter elevation angle).

Information sources

1. US patent, 4956644, cl. G 01 S 3/02, 1990

2. RU, patent, 2190236, cl. G 01 S 5/04, 2002

3. Johnson D.H. Application of spectral estimation methods to problems of determining the angular coordinates of radiation sources // TIIER. - 1982. - T. 70. No. 9. - S.126.

4. Shevchenko V.N. Estimation of the angular position of sources of coherent signals based on regularization methods // Radio Engineering. - 2003. - No. 9. - C.3-10.

Claims (1)

A method for detecting radio frequency sources with frequency hopping (SICH), including receiving and synchronizing digitally the signals received by the reference antenna and all antennas included in the N-element array, time-shifting conversion of digital signals to obtain with a given discreteness in time and frequency the complex spectral signal density of each antenna, multiplying the complex conjugate spectral density of the reference antenna and the spectral densities of the remaining antennas for generating a time-frequency matrix (FWM) of complex discrete radio holograms, characterized in that a block FWM of complex correlation coefficients of the generated complex discrete radio holograms is formed, the modules of the correlation coefficients with a threshold are compared, the signals of the elements of the block FMS at which the threshold is exceeded are combined into the i-th detected signal and form a binary time-frequency matrix (MFM) of localization of the detected signal, calculate the two-dimensional autocorrelation function (ACF) and sample functions of The determination of the duration (PSF) and frequency jumps (PSF) of the BHF elements of each i-th signal is determined by the degree of concentration of the ACF and PSF near their maximum values, as well as by the degree of blur of the PSF in terms of frequency, the presence of a source with an SIC in the i-th signal, which are preliminarily identified as a single source with WMS or which is part of a group of sources of other classes, and also find the maximum probable value of the duration of its radiation from the maximum RDF, statistically related elements of the i-th signal are extracted duration to obtain a BHFM localization and identification of radiation from a single source with WMS, averaging single-frequency radio holograms in the selected region of localization of a single source with WMS to obtain an averaged multi-frequency radio hologram, transform the resulting multi-frequency radio hologram to obtain an image of a two-dimensional angular spectrum, from which the angular coordinates and azimuth are determined with SICH.

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