RU2319976C1 - Method for search of composite signal transmitters - Google Patents

Abstract

FIELD: radio engineering, applicable in passive radio monitoring systems with multielement antenna arrays for search of transmitters using signals with a large base.

SUBSTANCE: the search efficiency is attained on the basis of complex two-dimensional mutual correlation functions used for space-frequency-time localization and identification of three principal classes of composite signals.

EFFECT: enhanced efficiency of search of composite signals with a priori unknown wave-form and frequency-time structure simultaneously emitted in the analyzed space-frequency-time region of reception by a great number of transmitters.

2 cl, 37 dwg

Description

The invention relates to radio engineering and can be used in radio monitoring systems with multi-element antenna arrays to search for transmitters using signals with a large base.

The solution to the problem of continuously increasing the number and types of complex signals (multifrequency signals with frequency hopping (WMS), single-frequency noise-like signals (SHPS), signals with linear frequency modulation (LFM) and their combinations), which have a low power spectral density and are designed to provide the operation of several transmitters in the same frequency band is an essential condition for ensuring the effectiveness of a wide fleet of existing and promising radio systems.

A known method of searching for transmitters of complex signals [1], including:

1) coherent radio signal reception by two spatially separated receiving channels;

2) the formation of a signal that describes the mutual correlation function, depending on the time shift of the signals received by a pair of receiving channels;

3) the allocation of the Central part of the mutual correlation function, depending on the time shift of the received radio signals;

4) the conversion of the selected central part of the mutual correlation function into a complex function of the mutual spectral density of the received radio signal;

5) comparing the module of the complex function of the mutual spectral density with a threshold for detecting a radio signal and localizing the frequency region occupied by its power spectrum (determining the width of the spectrum and its position on the frequency axis);

6) measuring the angle of the phase slope of the mutual complex spectral density in the localized frequency region to determine the direction of arrival of the received radio signal;

7) an indication of the results of detection and direction finding of the radio signal. This method is based on the formation of a one-dimensional cross-correlation function, which depends on the time shift of signals coherently received by two spatially separated channels, and when searching for complex signals has the following disadvantages:

- a narrow working sector of signal search angles limited by angles near the normal to the position line of the receiving channel antennas;

- limited search sensitivity due to the impossibility of separating simultaneously acting signals with overlapping spectra and the presence of only two coherent reception channels.

There is a better way to search for transmitters of complex signals [2], adopted as a prototype. The method includes:

1) coherent reception of signals by spatially separated receiving channels. As a result, an ensemble of signals x _n (t) is formed, depending on time z and on the antenna number n = 0, ..., N-1;

где z - номер временного отсчета сигнала;2) synchronous conversion of received signals x _n (t) into complex digital signals

where z is the number of time reference signal;

3) synchronous registration of digital signals

в комплексные временные спектры сигнала каждой антенны, например, дискретным преобразованием Фурье (ДПФ) по времени

где F_z{...} - оператор ДПФ по времени, a k=0, ..., K-1 - номер частотного отсчета;4) digital signal conversion

into complex time spectra of the signal of each antenna, for example, discrete Fourier transform (DFT) in time

where F _z {...} - the operator of the DFT time, ak = 0, ..., K-1 - the number of frequency reference;

размером N×K с элементами

As a result of this operation, a matrix of time spectra of the received signal is formed

size N × K with elements

5) storing the matrix of spectra of the received signal

6) calculation of the signal power spectrum of each antenna

7) summation of power spectra of antennas

с порогом и выбор частот, на которых обнаружен сигнал передатчика;8) comparison of the total power spectrum

with a threshold and the choice of frequencies at which a transmitter signal is detected;

сигнала, принятого антеннами решетки, путем вычисления нулевой составляющей свертки комплексно-сопряженного спектра опорной

и спектров остальных

антенн на выбранных частотах, где

- вектор-столбец с элементами

9) obtaining the amplitude-phase distribution (AFR)

the signal received by the array antennas by calculating the zero convolution component of the complex conjugate reference spectrum

and the spectra of the rest

antennas at selected frequencies, where

- column vector with elements

на комплексную фазирующую функцию, зависящую от конфигурации антенной решетки, и суммирование полученных произведений;10) calculation of the angular spectrum by multiplying the obtained AFR

on the complex phasing function, depending on the configuration of the antenna array, and the summation of the obtained products;

11) determination of the bearing of the transmitter by the maximum square of the module of the complex angular spectrum.

сигналов, принимаемых каждой парой пространственно разнесенных каналов. Нулевая составляющая свертки спектров сигналов, как известно, является эквивалентом, получаемым в частотной области, нулевой составляющей одномерной временной функции взаимной корреляции принимаемых сигналов, содержащей только часть полезной энергии коррелируемых сигналов. В связи с этим данный способ эффективно решает задачу обнаружения-пеленгования сложных сигналов одиночных передатчиков при достаточно высоких входных отношениях сигнал/шум-помеха. Однако при обнаружении и пеленговании множества одновременно действующих сложных сигналов с различной частотно-временной структурой (сигналы СИЧ, ШПС, ЛЧМ и их комбинации) в реальной помеховой обстановке данный способ теряет свою эффективность. Это обусловлено тем, что в условиях априорной неопределенности относительно формы и параметров сигналов с низкой спектральной плотностью мощности способ-прототип обладает следующими основными недостатками:The prototype method uses many spatially separated channels of coherent reception and provides a search in a wide working sector of angles. At the same time, the prototype is based on the formation of only the zero component of the convolution of the spectra

signals received by each pair of spatially separated channels. The zero component of the convolution of the signal spectra, as is known, is the equivalent obtained in the frequency domain, the zero component of the one-dimensional time function of the mutual correlation of the received signals, containing only part of the useful energy of the correlated signals. In this regard, this method effectively solves the problem of detection-direction finding of complex signals of single transmitters with a sufficiently high input signal-to-noise-noise ratio. However, when detecting and direction finding a multitude of simultaneously acting complex signals with different time-frequency structure (signals WMS, ShPS, LFM and their combinations) in a real interference environment, this method loses its effectiveness. This is due to the fact that under conditions of a priori uncertainty regarding the shape and parameters of signals with a low spectral power density, the prototype method has the following main disadvantages:

- low noise immunity during detection, due to the absence of spatial filtering operations of the signals at the detection stage, ensuring their separation in the direction of arrival;

- low noise immunity during direction finding, due to mutual interference of signals overlapping in frequency due to the lack of time localization operations (separation of simultaneously acting signals with overlapping spectra);

- low sensitivity during direction-finding, due to energy loss during the formation of complex envelopes of signals due to the calculation of only one component of the convolution of their spectra.

The technical result of the invention is to increase the efficiency of searching for complex signals with an a priori unknown shape and time-frequency structure, simultaneously emitted in the analyzed spatial-frequency-temporal region of the reception of multiple transmitters.

Improving the search efficiency was achieved on the basis of additional information extracted due to the transition from two-dimensional signal processing to more informative three-dimensional processing based on the formation of complex generalized mutual correlation functions depending on the time and frequency shifts of signals coherently received by all possible pairs of spatially separated channels, and its conversion into complex functions of the mutual spectral density for each expected direction of arrival of the signal fishing This opened up the possibility of:

- a more informative three-dimensional spatial-frequency-time search of signals instead of a two-dimensional spatial-frequency search;

- additionally increasing the information content of the identification identification of the three main classes (WMS, ShPS, LFM) of complex signals.

To achieve the technical result, a method is proposed for searching for transmitters of complex signals, including coherent reception of signals by spatially separated receiving channels, synchronous conversion of received signals into complex digital signals, storing digital signals, according to the invention

from digital signals of pairs of channels form complex two-dimensional mutual correlation functions (DCF), depending on the time and frequency shifts of the received signals,

shift in time the complex DCF of each pair by a value corresponding to each expected direction of arrival of the received signals,

for each expected direction of arrival, the central two-dimensional parts of the correspondingly shifted TWF are distinguished, which are averaged and converted into a complex function of mutual spectral density (FSPP),

use the obtained complex FVSP for frequency-time localization and identification of many complex signals simultaneously falling into the time-frequency domain of reception, and determine bearings of their transmitters,

indicate search results.

Particular cases of the method are possible:

1. The time-frequency localization and identification of many complex signals and the determination of the bearings of their transmitters is carried out by comparing the module of each complex high-pass filter with a threshold, identifying the closed time-frequency regions of each high-frequency filter, in which the threshold is exceeded, as the time-frequency localization regions of the detected radiation, comparing the overlapping in the time-frequency domain radiation of different FSPPs and the identification of radiation with maximum mutual energy as single-element transmission signals sensors with bearings determined by the angular direction of formation of the corresponding EHF, combining single-element signals with matching bearings into a multi-element signal of a separate transmitter, converting the integrated EHF of each localized signal into a complex two-dimensional autocorrelation function (DACF) and using the modules of the integrated EHF and DACF to decide on the signal to one of the classes: multi-frequency signals with frequency hopping (SICH), single-frequency noise-like with chasing (PNS) signal with linear frequency modulation (LFM).

This increases the efficiency of detection and localization in frequency, time and direction of arrival of many simultaneously operating complex signals with different time-frequency structure under conditions of a priori uncertainty regarding the shape and spatial-frequency-time parameters of the signals. In addition, this provides the identification of localized signals with the aim of dividing them into two groups (single-element and multi-element signals) and into three main classes (signals WMS, SHPS, chirp).

2. The determination of bearings of multiple transmitters is also carried out by weighting averaging bearings of single-element signals combined into a multi-element signal of a single transmitter.

This improves the direction finding accuracy of transmitters at low signal-to-noise ratios.

The operation of the method is illustrated by drawings:

Figure 1. Block diagram of a complex signal search device.

Figure 2. Features of the mutual spectral density function in the localization of two complex signals (LFM and WMS) with matching angles of arrival.

Figure 3, 4. Features of localization and identification of the chirp signal.

5, 6. Features of localization and identification of a narrowband signal.

Fig.7, 8. Features of the localization and identification of the signal with WMS.

Fig.9, 10. Features of the localization and identification of the SHPS signal.

A method of searching for transmitters of complex signals is as follows.

1. Coherently receive spatially spaced receiving channels signals emitted by multiple transmitters. As a result, an ensemble of signals x _n (t) is formed, depending on time t, where n = 1, ..., N is the number of the antenna of the receiving channel.

где z - номер временного отсчета сигнала.2. Synchronously transform the ensemble of received signals x _n (t) into complex digital signals

where z is the time reference number of the signal.

может быть выполнено различными способами, например аналогово-цифровым или полностью цифровым способами, основанными на преобразовании Гильберта [3, стр.65] или квадратурной дискретизации [3, стр.169]. Значение периода дискретизации T_d должно быть много меньше минимального значения задержки между моментами прихода сигналов на две антенны, то есть

где d - расстояние между антеннами, Δ - шаг по углу, с - скорость света. Так при d=1000 м и Δ=0,1 градуса получаем

что соответствует частоте дискретизации 200 МГц. Отметим, что на современной элементной базе реализуемы частоты дискретизации, превышающие значение 1 ГГц;Converting received signals x _n (t) to complex digital signals

can be performed in various ways, for example, analog-digital or fully digital methods based on the Hilbert transform [3, p. 65] or quadrature sampling [3, p. 169]. The value of the sampling period T _d should be much less than the minimum delay between the moments of arrival of the signals at two antennas, i.e.

where d is the distance between the antennas, Δ is the step along the angle, and s is the speed of light. So at d = 1000 m and Δ = 0.1 degrees we get

which corresponds to a sampling frequency of 200 MHz. Note that, on a modern elemental base, sampling frequencies exceeding 1 GHz are realized;

3. Synchronously register complex digital signals

зависящие как от временного τ, так и от частотного F сдвигов принятых сигналов.4. Of the digital signals of the pairs of channels form a complex DCF

depending both on the time τ and on the frequency F of the shifts of the received signals.

не несет дополнительной информации по сравнению с

формирование выполняют только для пар каналов, номера которых удовлетворяют условию n<n', n=1,...,N, n'=1, ..., N. Так, если n=1, то n'=2,3,..., а если n=2, то n'=3,4,... и т.д.Moreover, due to the fact that, for example,

does not carry additional information compared to

The formation is performed only for pairs of channels whose numbers satisfy the condition n <n ', n = 1, ..., N, n' = 1, ..., N. So, if n = 1, then n '= 2, 3, ..., and if n = 2, then n '= 3,4, ... etc.

The formation of complex DCF is performed in the time or in the frequency domain by known methods [4, p. 95].

In the first case, the formation of complex DCF is performed according to the following formula:

where () ^* denotes complex conjugation.

получают комплексные временные спектры

где F_z{...} - оператор дискретного преобразования Фурье (ДПФ) по времени, как известно, эффективно вычисляемого на основе алгоритма быстрого преобразования Фурье, k=0,...,K-1 - номер частотного отсчета, а формирование комплексных ДВКФ выполняют по следующей формуле:In the second case, from the signals

receive complex time spectra

where F _z {...} is the discrete Fourier transform (DFT) operator in time, as you know, effectively calculated on the basis of the fast Fourier transform algorithm, k = 0, ..., K-1 is the frequency reference number, and the formation of complex DVKF perform the following formula:

where ω _k is the frequency corresponding to the k-th frequency sample.

As a result of this operation, N (N-1) / 2 complex DVKF are obtained.

на величину

соответствующую каждому ожидаемому направлению m=1,...,М прихода принимаемых сигналов.5. The time-shifted complex DCF of each channel pair is shifted

by the amount

corresponding to each expected direction m = 1, ..., M of the arrival of the received signals.

The shift is performed according to the following formulas:

The values of time shifts corresponding to each expected direction of arrival of signals, for example, for an annular antenna array, are calculated by the following formula:

where R is the radius of the lattice, c is the speed of light, h = 0 ... H-1 is the current number of the grid node of the guidance of the lattice in elevation.

As a result of the performance of the described operations, MN (N-1) / 2 shifted complex DVKFs are obtained

6. For each expected direction of arrival m = 1, ..., M perform the following actions:

сдвинутых ДВКФ- highlight the central two-dimensional parts

shifted DCF

The parameters Δ and Θ are selected based on the need to suppress noise and determining the level of mutual interference side peaks of the DCF, as well as on the basis of the permissible level of distortion of the fronts of the pulses of the useful signal.

Применение двухмерного окна к комплексной ДВКФ

эквивалентно двухмерной фильтрации комплексной функции взаимной спектральной плотности, формируемой на последующем этапе. Эту фильтрацию можно также рассматривать как двухмерную фильтрацию комплексной функции взаимной спектральной плотности в корреляционной области;This operation can be considered as the operation of applying a two-dimensional window having a square or rectangular support region to a complex DCF

Application of a two-dimensional window to a complex DCF

equivalent to two-dimensional filtration of the complex function of the mutual spectral density formed in the next step. This filtration can also be considered as two-dimensional filtration of the complex function of the mutual spectral density in the correlation region;

- average the central two-dimensional parts of the shifted complex DCFFs allocated for the mth direction of arrival

в комплексную ФВСП для m-го направления прихода сигналов- convert the average DCF

into the integrated high-pass filter for the mth direction of signal arrival

As a result of the performance of the described operations get M complex FVSP

комплексной ФВСП

представляет собой спектрограмму, то есть зависимость мгновенного амплитудного спектра принятого суммарного сигнала от времени или, другими словами, "изображение" частотно-временного распределения энергии излучений в анализируемой частотно-временной области приема, полученное для m-го направления прихода сигналов. Понятно, что информации, содержащейся в одном таком "изображении", недостаточно для идентификации принадлежности этих излучений к одному из сложных сигналов и нахождения их пеленга. Недостающая информация извлекается на последующих этапах совместной обработкой совокупности М полученных комплексных ФВСП

с целью поиска трехмерных (пространственно-частотно-временных) областей, содержащих максимальную энергию принятых сигналов.Module

integrated FSPP

represents a spectrogram, that is, the dependence of the instantaneous amplitude spectrum of the received total signal on time or, in other words, an “image” of the time-frequency distribution of the radiation energy in the analyzed time-frequency reception region obtained for the m-th direction of arrival of the signals. It is clear that the information contained in one such "image" is not enough to identify whether these emissions belong to one of the complex signals and to find their bearing. The missing information is extracted at subsequent stages by joint processing of the set M of the obtained complex FVSP

in order to search for three-dimensional (space-frequency-time) regions containing the maximum energy of the received signals.

для частотно-временной локализации и идентификации множества сложных сигналов, одновременно попадающих в частотно-временную область приема, и определения пеленгов их передатчиков.7. Use obtained for all expected directions m = 1, ..., M of the arrival of the received signals complex FVSP

for the time-frequency localization and identification of many complex signals simultaneously falling into the time-frequency domain of reception, and the determination of bearings of their transmitters.

To do this, perform the following steps:

каждой m-й комплексной ФВСП

с порогом С₀;- compare the module

every mth complex

with a threshold of C ₀ ;

в которых превышен порог С₀, в качестве частотно-временных областей локализации обнаруженных излучений.- identify closed time-frequency areas of each complex FVSP

in which the threshold C ₀ is exceeded, as the time-frequency regions of localization of the detected radiation.

At this stage, radiation will be detected and localized by the frequency and time of radiation that fall into the time-frequency domain of reception. Detected and localized radiation can be signals from different transmitters or can be elements of a complex signal of one of the transmitters, for example, a transmitter of a signal from WMS;

- compare the overlapping in the time-frequency region of the radiation of different complex high-pass spectroscopy.

This operation can be considered as a generalization of the operation traditionally used in the one-dimensional case to search for the direction of arrival of the signal from the maximum radiation pattern of the antenna array;

- identify radiation with a maximum mutual energy as single-element signals of transmitters with bearings, determined by the angular direction of formation of the corresponding FVSP, that is, FVSP, which contains the selected radiation with maximum mutual energy.

с ожидаемыми угловыми направлениями прихода m=1,...,М принятых сигналов, которые, в свою очередь, как отмечалось ранее, являются направлениями наведения антенной решетки;In this case, an unambiguous connection of the number m of the complex FSPP

with the expected angular directions of arrival m = 1, ..., M of the received signals, which, in turn, as noted earlier, are the directions of pointing the antenna array;

- combine single-element signals with matching bearings in a multi-element signal of a separate transmitter.

The coincidence of bearings of single-element signals is fixed, for example, as a result of their falling into the confidence angular interval, the value of which is selected based on the required probability of correct identification.

As follows from the described operations, at this stage, the direction of arrival and the time-frequency region of each received signal are simultaneously determined. In other words, at this stage, the spatial-frequency-time localization of all transmitter signals that simultaneously fall into the time-frequency receiving region is realized. As a result of spatial-frequency-time localization, signal separation is automatically ensured and the signal-to-noise-noise ratio is maximized for each signal;

The effectiveness of the described operations, as well as the justification and selection of signs for the subsequent identification of the three main classes of complex signals (LFM, WAV, SHPS [5, p. 10]) against the background of noise and interference (in particular, narrow-band signals) are confirmed by simulation using the mathematical package MathCAD 2001 Professional.

комплексной ФВСП, сформированной для углового направления, совпадающего с направлением прихода двух сигналов: сигнала с СИЧ и сигнала с ЛЧМ. Из фиг.2а и фиг.2б видно, что в случае одномерной обработки, характерной для прототипа, сигналы не разделяются, так как ЛЧМ сигнал перекрывается по времени со всеми четырьмя импульсами, а по частоте с двумя импульсами сигнала СИЧ. В то же время, как следует из фиг.2в и фиг.2г, предложенный способ обеспечивает полное разделение по частоте и времени СИЧ и ЛЧМ сигналов с совпадающими углами прихода.As an example, Fig. 2 shows the projection of the spectrogram onto the time (Fig. 2a) and frequency (Fig. 2b) axes, on the time-frequency coordinate plane (Fig. 2c) and the spectrogram itself (Fig. 2d), that is, the module

integrated high-pass filter, formed for the angular direction that coincides with the direction of arrival of two signals: the signal with WMS and the signal with chirp. From figa and fig.2b it is seen that in the case of one-dimensional processing, characteristic of the prototype, the signals are not separated, since the LFM signal overlaps in time with all four pulses, and in frequency with two pulses of the WMS signal. At the same time, as follows from figv and fig.2d, the proposed method provides a complete separation of the frequency and time of the MF and LFM signals with matching angles of arrival.

On figa - fig.3g presents the projection of the spectrogram on the time (figa) and frequency (fig.3b) axis, the time-frequency coordinate plane (figv) and the spectrogram (fig.3d) of the localized chirp signal and in Fig. 4a - Fig. 4g - projections onto the time (Fig. 4a) and frequency (Fig. 4b) axes, on the time-frequency coordinate plane (Fig. 4c) and the actual module of the complex DACF (Fig. 4d) of this signal .

For comparison, figa - fig.5g presents the projection of the spectrogram on the temporal (figa) and frequency (fig.5b) axis, on the time-frequency coordinate plane (fig.5c) and the spectrogram itself (fig.5g), and on figa - fig.6g, respectively, the projection on the time (fig.6a) and frequency (fig.6b) axis, on the time-frequency coordinate plane (fig.6c) and actually the complex module DAKF (fig.6d) narrowband signal, when identifying the class of a complex signal that is a nuisance.

Similar images for a localized signal with WMS are presented in Fig. 7 and Fig. 8, and for a localized SHPS signal (a pseudo-random signal with four-position phase shift keying was used in the simulation) - in Fig. 9 and Fig. 10.

From figure 3, 5, 7, 9 it follows that the proposed method provides a separation by the angle of arrival of several simple and complex signals that simultaneously fall in the time-frequency domain of reception.

From Figs. 4, 6, 8, 10 it follows that the complex DACF module can be used as a sign of identification of simple (narrow-band) signals, in this case being an obstacle, and the three main classes (LFM, SICH, ShPS) of complex signals. In this case, the shape of the DACF module of the narrowband signal (Fig. 6) is radically different from the form of the DACF modules of the LFM signals (Fig. 4), WMS (Fig. 8) and SHPS (Fig. 10). In turn, the shape of the module DACF chirp signal (figure 4) is also radically different from the shape of the signal modules WMS (Fig. 8) and BPS (Fig. 10). At the same time, as follows from Fig. 8 and Fig. 10, the DACF modules of the NICH and SHPS signals are close in shape and have the form of two-dimensional δ-functions with different pedestals. However, the shape of the pedestal of the DACF modules of the SICH and SHPS signals is most affected by noise, and, as a result, this feature does not provide an effective separation of the SICH and ShPS signals in a wide range of input signal-to-noise ratios. In this regard, there is a need to attract an additional sign of identification.

As an additional sign of identification of the class of complex signals of NICH and SHPS according to the simulation results, the shape of the module of the integrated FVSP is selected (see Fig. 7 and Fig. 9). At the same time, the fact was used that, due to the regularity of the pulse propagation of the WMS signal in time, the degree of overlap in time of the elements of the module of its integrated EHF is close to zero (see Fig. 7c). In contrast, the degree of overlapping in time of the elements of the module of the integrated FWSP SHPS signal is significantly different from zero (see Fig. 9c).

In this regard, to identify the class (WMS, NPS, LFM) of detected and localized signals, the following operations are performed:

- convert the integrated EHF of each localized signal into a complex DACF;

- they use modules of integrated FVSP and DAKF to decide on whether the signal belongs to one of the classes: multi-frequency signals with WMS, single-frequency BSS signals, signals with chirp.

The use of modules of complex FVSP and DAKF to decide on whether a signal belongs to one of the classes is possible in various ways. For example, they decide that the signal belongs to the class:

- WMS signals, if the DACF module is concentrated near its maximum value, and the degree of overlap of the elements of the integrated EHF module in time is close to zero;

- SHPS signals, if the DAKF module is concentrated near its maximum value, and the degree of overlap of the elements of the integrated EHF module in time differs from zero;

- chirp signals if the DACF module is concentrated near a plane whose projection onto the time-frequency plane varies linearly with frequency.

At the same time, the degree of overlap of the elements of the module of the integrated EHFH signals of WMS and SHPS in time can also be determined in various ways based on the features of the time-frequency structure of these signals. For example, by comparing the EHF module with a threshold, it is possible to form a binary EHF, in which two-dimensional pulses of unit amplitude will correspond to the presence of a signal, and the pause between pulses to its absence. After that, by projecting the binary high-pass filter on the time axis, a pulse coincidence flow can be formed. In this case, for the WMS signal, the degree of overlap in time of the pulses of the binary high-pass filter and, consequently, the intensity of the coincidence stream, as follows from Fig. 7c, will be close to zero. In contrast, the intensity of the coincidence stream in the presence of a BSS signal (see Fig. 9c) will be significantly different from zero.

As follows from the described operations, as a result of this stage of signal processing, identification of a class of complex signals that simultaneously fall in the time-frequency domain of reception is provided.

Note that at low input signal-to-noise ratios, bearings of elementary signals identified as components of a complex multi-element signal of an individual transmitter may have slightly different values. In this regard, to obtain a single bearing value of a multi-element signal, an operation is used according to which weight averaging of bearings of single-element signals combined into a multi-element signal of a separate transmitter is performed.

The weight of an individual bearing can be determined in various ways, for example, it can depend on the signal-to-noise ratio at which it is obtained, or determined by the degree of proximity to other bearings.

8. Display the class (WMS, or SHPS, or LFM) and the time-frequency region of localization of each detected signal, as well as the bearings of their transmitters. To analyze the total load of the analyzed time-frequency receiving region, an “image” of the time-frequency energy distribution of the entire set of detected signals can be displayed. In addition, it is possible to display the entire set of bearings obtained on a cartographic background.

From the above description of the proposed method, it follows that increasing the search efficiency of several complex signals with an a priori unknown shape and time-frequency structure in a wide sector of angles is achieved by introducing the following operations:

- the formation of two-dimensional VKF instead of one-dimensional VKF, which increases the information content of the search;

- shift of two-dimensional VKF in time, which ensures the pointing of the antenna array in each of the expected directions of the arrival of signals and, as a result, increases the sensitivity and resolution of the search;

- two-dimensional filtering in the correlation region and the formation of the VSP function ("image" of the time-frequency distribution of signal energy) instead of VSP ("image" of the frequency distribution of signal energy), which also increases the information content, sensitivity and resolution of the search;

- identification of time-frequency areas of localization of complex signals instead of frequency areas, which also increases the information content and quality of the search;

- identification of single-element and multi-element signals, as well as the three main classes (WMS, ShPS, LFM) of complex signals, which also increases the information content of the search.

In addition, it should be noted that the proposed method provides improved search efficiency in the presence of only one input implementation of the useful signal. This is of particular value in the detection-direction finding of short signals with an extended spectrum, that is, signals that have both temporary and energy secrecy. Moreover, the proposed method, unlike the prototype, has no restrictions on the wave distance between the elements of the antenna array, which makes it possible to use very large antenna bases with a fixed number of antenna elements, providing unambiguous angular measurements.

The device (figure 1), which implements the proposed method, includes a series-connected antenna system 1, an N-channel frequency converter (NRF) 2, an N-channel quadrature sampling device 3, a shaper of complex DVKF 4, a shifter 5, a shaper of the FSPP 6 , a detection device 7, an identification device 8, and a display device 9. In turn, a complex driver of DVKF 4, a shift device 5, a shaper of the FVSP 6, a detection device 7, an identification device 8 can be performed in a single channel flax or multichannel options. Consider a multi-channel option that provides the highest possible speed for searching complex signals.

Antenna system 1 contains N antennas with numbers n = 1 ... N, combined in an array. The antenna array can be of any spatial configuration: flat rectangular, flat annular or three-dimensional, in particular conformal.

The bandwidth of each channel of the multi-channel RFI 2 provides the simultaneous reception of many complex signals. In addition, multi-channel RFR 2 and device 3 are made with a common local oscillator, which provides coherent reception of radio signals. For periodic calibration of channels using an external signal source in order to eliminate their amplitude-phase non-identity, the RFI 2 provides the connection of one of the antennas, instead of all the antennas of the array. Calibration by internal signal source is possible. 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. If the resolution and speed of the ADCs that are part of device 3 are sufficient for direct analog-to-digital conversion of the input signals, such as, for example, when constructing an image in the KB range, then a frequency selective bandpass filter and amplifier can be used instead of the RFI 2. In other words, the analog part of the device that implements the proposed method can be built on the principle of direct amplification.

A device that implements a method for searching for complex signals, operates as follows.

The radio signals of the transmitters are received by the antennas of the array 1. The total radio signal x _n (t) received by each antenna element of the array 1, depending on time t, is coherently transferred to a lower frequency in the RFI 2.

Комплексные цифровые сигналы

синхронно регистрируются на заданном временном интервале в формирователе ДВКФ 4. Кроме того, в формирователе 4 из цифровых сигналов независимых пар каналов одновременно формируются

комплексных ДВКФ

The ensemble of signals x _n (t) formed in RFI 2 is synchronously converted in device 3 into an ensemble of complex digital signals

Integrated Digital Signals

synchronously recorded at a given time interval in the shaper DVKF 4. In addition, in the shaper 4 of the digital signals of independent pairs of channels are simultaneously generated

integrated FEC

поступают в устройство сдвига 5.Received complex DVKF

enter the shear device 5.

сдвигаются по времени на величины

соответствующие всем ожидаемым направлениям m=1, ..., М прихода принимаемых сигналов. Полученные

сдвинутых комплексных ДВКФ

поступают в формирователь ФВСП 6.In device 5, integrated DCF of each channel pair

are shifted in time by

corresponding to all expected directions m = 1, ..., M of arrival of received signals. Received

shifted complex DCF

come in shaper FVSP 6.

всех сдвинутых функций

Для каждого ожидаемого направления прихода m=1, ..., М усредняются соответствующие центральные части

Полученное для m-го направления среднее значение

преобразуется в комплексную функцию взаимной спектральной плотности

для m-го направления прихода сигналов.In the shaper 6, the central parts are simultaneously distinguished

all shifted functions

For each expected direction of arrival m = 1, ..., M, the corresponding central parts are averaged

The average value obtained for the mth direction

transforms into a complex function of mutual spectral density

for the m-th direction of arrival of signals.

поступают в устройство обнаружения 7.Simultaneously obtained M complex functions of mutual spectral density

arrive at the detection device 7.

всех М функций взаимной спектральной плотности

с порогом С₀ и для каждой функции

идентифицируются замкнутые частотно-временные области, в которых превышен порог С₀, в качестве частотно-временных областей локализации обнаруженных излучений.The device 7 simultaneously compares the modules

all M functions of mutual spectral density

with threshold С ₀ and for each function

closed-time-frequency regions in which the threshold C ₀ is exceeded are identified as time-frequency regions of localization of the detected emissions.

обнаруженных излучений поступают в устройство идентификации 8.The time-frequency localization regions obtained for all M expected arrival directions and the corresponding values of the mutual spectral density functions

the detected radiation enter the identification device 8.

In the device 8, emissions with maximum mutual energy are identified as single-element transmitter signals and their bearings are determined. Single-element signals with matching bearings are combined into a multi-element signal of a separate transmitter, and weighting of bearings of single-element signals combined into a multi-element signal of a separate transmitter is also performed. In addition, the device 8 makes a decision that the detected signal belongs to one of the classes: multi-frequency signal with WMS, single-frequency SHPS signal, signal with LFM.

The device 9 displays the search results.

Thus, due to additional information extracted from one implementation of the received signals by introducing operations:

- the formation for each expected direction of arrival of signals averaged over space of complex two-dimensional mutual correlation functions and their conversion into complex functions of mutual spectral density;

- spatial-frequency-time localization, as well as the identification of single-element and multi-element signals and the three main classes (SICH, ShPS, LFM) of complex signals of several radio transmitters that simultaneously fall into the space-time-frequency region of reception, it is possible to solve the problem with the achievement of the technical result .

INFORMATION SOURCES

1. US, patent, 5955993, CL. G01S 3/02, 1999

2. RU, patent, 2158002, cl. 7 G01S 3/14, 5/04, 2000

3. Sergienko A.B. Digital Signal Processing: A Textbook for High Schools. 2nd ed. - St. Petersburg: Peter, 2006.

4. Lezin Yu.S. Introduction to the theory and technique of radio systems: Textbook. manual for universities. - M.: Radio and Communications, 1986.

5. Dickson R.K. Broadband systems. - M.: Communication, 1979.

Claims (3)

1. A method for searching for transmitters of complex signals, including coherent reception of signals by spatially separated receiving channels, synchronous conversion of received signals into complex digital signals, storing digital signals, characterized in that complex two-dimensional mutual correlation functions (DCF) are formed from digital signals of channel pairs, depending from the time and from the frequency shifts of the received signals, the time-shifted complex DVKF of each pair is shifted to the corresponding each expected direction On the basis of the arrival of the received signals, the value, for each expected direction of arrival, the central two-dimensional parts of the respectively shifted DCFGs are selected, which are averaged and converted into a complex function of mutual spectral density (FSPP), the obtained complex FSPFs are used for time-frequency localization and identification of many complex signals simultaneously in the time-frequency domain of reception, and the determination of the bearings of their transmitters, indicate the search results. 2. The method according to claim 1, characterized in that the time-frequency localization and identification of many complex signals and the determination of bearings of their transmitters is carried out by comparing the module of each complex high-pass filter with a threshold, identifying closed frequency-time regions of each high-frequency filter, in which the threshold is exceeded, as the time-frequency regions of localization of the detected radiation, the comparison of the levels of the overlapping in the time-frequency region of the radiation of different high-pass spectra and the identification of radiation with the maximum mutual energy as single-element signals of transmitters with bearings, determined by the angular direction of formation of the corresponding EHF, combining single-element signals with matching bearings into a multi-element signal of a separate transmitter, converting the complex EHF of each localized signal into a complex two-dimensional autocorrelation function (DACF) and using the modules of complex EHFs for acceptance and DACF decisions on whether a signal belongs to one of the classes: multi-frequency signals with step change pilots at, single-frequency noise-like signals, linear frequency modulation. 3. The method according to claim 2, characterized in that the determination of bearings of multiple transmitters is also carried out by weighting averaging bearings of single-element signals combined into a multi-element signal of a separate transmitter.

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