RU2732504C1 - Method for adaptive spatial-multichannel detection and direction finding of two frequency-inseparable radio-frequency sources - Google Patents

Abstract

FIELD: radio equipment.SUBSTANCE: invention relates to radio engineering and can be used in multichannel monopulse detectors-direction finders when receiving two frequency-inseparable signals with unknown noise intensity of receiving channels, which is typical for operation of data transmission networks, for example, 3G standard. Method comprises synchronous reception of time realizations from antenna system (AS) antenna outputs in spatial channels of direction-finding detector, simultaneously falling into current reception band, synchronous conversion of temporal realizations into digital form, fast Fourier transform. Based on the received time matrices of mutual energy matrices, the first decision statistics is calculated, comparing it with the lower threshold and the upper threshold, calculated in accordance with the Neyman–Pearson criterion and providing the required constant false alarm probability; if the second threshold is exceeded, making a decision that the spectral reading corresponds to the signal from one radio-frequency source and calculating the estimate of the azimuth and elevation angle, in case the first threshold is not exceeded – the decision that the spectral reading is noise, if the spectral reading falls between the lower and upper thresholds, additional processing is performed, calculation of the second decision statistics and its comparison with the third threshold, when it is exceeded – formation and calculation of the global maximum of the direction-finding relief, formation of the third decisive statistics and its comparison with the fourth threshold, in case of exceeding the threshold, making a decision that the spectral reading corresponds to signals from two radio-frequency sources and calculation of estimates of directions and levels of the received signals.EFFECT: high efficiency of adaptive spatial-multichannel detection and direction finding of two frequency-inseparable radio signal sources, quantitatively manifesting in high probability of correct detection at a fixed probability of false alarm, high reliability of determining the number of frequency-inseparable radio signal sources, accuracy and reliability of determining directions of arrival and ratio of energy levels of received radio signals under conditions of additive Gaussian noise of unknown intensity.1 cl, 8 dwg

Description

The invention relates to radio engineering and can be used in multi-channel monopulse detectors-direction finders when receiving radio signals from one or two inseparable frequency sources of radio emission in conditions of unknown noise intensity of the receiving channels, which is typical for the operation of data transmission networks, for example, the 3G standard.

The known method of multichannel detection and estimation of the number of radiation sources with adaptive equalization of the noise power in the channel [Tarasov GA, Kabakov IV, Nezvanov A.Yu. Method for multichannel detection and estimation of the number of radiation sources with adaptive equalization of the noise powers in the channel. RF patent No. 2204840, G01S 3/00].

The method includes the following steps:

, умножают на соответствующий весовой коэффициент

, где

- номер шага итерационной процедуры, вычисляют выборочную корреляционную матрицу сигналов

и минимальное собственное значение упомянутой выборочной корреляционной матрицы

.1. Signals of radiation sources are received by N sensors of the antenna array

, multiplied by the appropriate weighting factor

where

is the step number of the iterative procedure, the sample correlation matrix of signals is calculated

and the minimum eigenvalue of the mentioned sample correlation matrix

...

итерационной процедуры адаптивного выравнивания мощностей шумов в каналах всем весовым коэффициентам

присваивают единичные значения

, вычисляют выборочную корреляционную матрицу сигналов

, минимальное собственное значение, диагональные значения

и след

выборочной корреляционной матрицы, на последующих шагах упомянутой процедуры осуществляют оптимизацию значений весовых коэффициентов

по критерию максимума минимального собственного значения выборочной корреляционной матрицы при ограничениях в виде равенства следу корреляционной матрицы2. In the first step

an iterative procedure for adaptive equalization of the noise powers in the channels to all weight coefficients

assign single values

, calculate the sample correlation matrix of signals

, minimum eigenvalue, diagonal values

and trace

the sample correlation matrix, at the subsequent steps of the mentioned procedure, the values of the weighting coefficients are optimized

by the criterion of the maximum minimum eigenvalue of the sample correlation matrix under constraints in the form of equality to the trace of the correlation matrix

,

,

Where

- номер последнего шага итерационной процедуры адаптивного выравнивания мощностей шумов в каналах.

is the number of the last step of the iterative procedure for the adaptive equalization of the noise powers in the channels.

, полученных на последнем

-ом итерационном шаге.3. The decision on the detection of radiation sources and the estimation of the number of radiation sources is carried out after the completion of all steps of the iterative procedure for adaptive equalization of the noise powers in the channel of the multichannel detector with the values of the weight coefficients

received at the last

th iteration step.

However, one of the drawbacks of methods based on the calculation and analysis of eigenvalues is the fact that with small amounts of accumulations, the stability of these methods deteriorates greatly, since in the general case, the correspondence between the number of eigenvalues that have exceeded the threshold and the number of received signals is not ensured. At the same time, in radio monitoring systems, in order to ensure the required scanning speed, there is a limitation on increasing the number of accumulations, due to which, in these systems, the above method is unstable.

Another disadvantage of the above method is the fact that the multidimensional eigenvalue distribution function is used to calculate the normalized threshold values. This approach is incorrect, since there is a nonlinear dependence (the sample correlation matrix is a non-negative definite quadratic form), which does not allow applying the approximation by a normal distribution.

Known methods of detecting and determining the two-dimensional bearing and frequency of radio sources, presented, for example, in [Shevchenko VN, Emelyanov GS, Vertogradov GG. Method for detecting and determining two-dimensional bearing and frequency of radio emission sources. RF patent No. 2190236, G01S 5/04].

The method includes the following steps:

1. Coherent reception of signals simultaneously falling into the current reception band, coherent transfer to a lower frequency, synchronous conversion of time realizations into digital form.

2. Synchronous registration of the received single-frequency and multifrequency signals for all bases, Fourier transform and calculation of the complex cross-correlation coefficients of the spectral density at each frequency of the received signals. After that, the data module of the complex cross-correlation coefficients is calculated and its value is compared with a fixed correlation threshold, selected in accordance with the Neumann-Pearson criterion. Signals with frequencies at which the threshold is exceeded are combined into the i-th signal and identified as a detected signal belonging to the same transmitter with a frequency band δf _i formed by spectral samples identified for this signal. Direction finding is carried out according to the real part of the formed two-dimensional angular spectrum: the azimuthal and elevation bearings of the i-th transmitter signals detected in the receiving band are determined from the maxima of this angular spectrum.

However, this method has the following disadvantages.

1. The method is based on the use of a "reference antenna", as a result of which it is not taken into account that the mutual spectrum of the signal in the receiving channels must be determined for all possible combinations of antenna pairs. In the case of receiving signals using a multichannel monopulse detector-direction finder (OP), this circumstance is a significant drawback of this method, unjustifiably not using the available technical capabilities of the electronic equipment of the OP and reducing the efficiency indicators of both solving the problem of identifying spectral readings by belonging to a signal of one IRI, and direction finding IRI. In addition, the presence of a reference channel can lead to a deterioration in the accuracy and reliability of direction finding, depending on which of the channels of the antenna system (AS) is selected as the reference channel, which in real operating conditions of the OP when placed on carriers of various types is due to the presence of the “shading” effect of the reference channel depending on its relative position relative to the other antennas of the speaker, as well as objects located in close proximity to the speaker (for example, a mast device).

2. The method involves calculating the real part of the two-dimensional complex angular spectrum of signals, which does not fully correspond to the results of solving the problem of direction finding within the framework of the theory of statistical radio engineering. The maximum of the modulus of the angular spectrum characterizes the largest amplitude response from a phased multichannel speaker in the direction to the IRI, while phasing is provided only when calculating the modulus of the angular spectrum.

3. The expression for the decisive statistics is inapplicable in the case of receiving two frequency inseparable signals with close energies, which, under conditions of a priori uncertainty about the levels of received signals, noise intensity, directions of arrival and the number of radio emission sources typical for radio monitoring, leads to an increase in the probability of missing signals received from two sources.

The closest in technical essence to the proposed is a method of two-signal detection and direction finding of frequency-inseparable radio signals with an unknown dispersion of the noise of the receiving channels using non-directional antennas forming an N-element antenna array [Ufaev V.A., Ufaev D.V., Khripushin V. D., Khripushin D.V., Shaidulin I.I., Kuznetsov A.I. Method of detecting and direction finding radio signals. RF patent No. 2289146, G01S 5/04], taken as a prototype.

The prototype method includes the following procedures.

1. Synchronous reception of time realizations from the outputs of all N identical antennas, such as a vertical vibrator, AS in the spatial channels of the direction finder.

2. Synchronous measurement at the antenna outputs of the complex amplitudes of radio signals by a multichannel radio receiver of a digital type with the number of channels equal to the number of antennas by applying the fast Fourier transform (FFT)

Where

- мнимая единица,

- imaginary unit,

k is the serial number of the radio signal with a total number of K <3,

- комплексная амплитуда k-го радиосигнала при приеме его в центре решетки,

is the complex amplitude of the k-th radio signal when it is received at the center of the array,

n is the serial number of the AC element (n = 1 ... N),

θ _0k , β _0k - true azimuth and elevation angle of arrival of the k-th radio signal,

- шумы n-го приемного канала, включающие шум мирового фона, шумы антенны и радиоприемного устройства,

- noises of the n-th receiving channel, including the noise of the world background, the noise of the antenna and the radio receiver,

- набег фаз радиосигналов в местах расположения антенн,

- phase incursion of radio signals at the antenna locations,

λ - radiation wavelength,

R is the radius of the speaker,

θ, β - angles of arrival of radio waves in the horizontal (azimuth) and vertical (elevation) planes;

Azimuth reading is carried out clockwise from the north direction. Readout of the elevation angle from the surface of the Earth. The values of the quantities are calculated with a predetermined (for example, 1 °) discreteness, determined by the required direction finding accuracy, and are entered into a memory device before starting work. Thus, with a bearing within 360 ° in azimuth and 90 ° in elevation, the total storage capacity is 360⋅90⋅N complex numbers.

The obtained values are stored in the buffer memory for the time of subsequent processing, which includes two stages.

3. At the first stage, the complex amplitudes of the radio signals are sequentially read and averaged, as a result of which the average power of the received radio signals is found over the set of antennas

,

,

4. Based on the complex amplitudes of radio signals read from the memory device, an angular spectrum of the first order is formed

.

...

Further, according to the following rule, coordinates are determined (an estimate of the azimuth and elevation of the radio emission source with the maximum amplitude of the radio signal) and the value of its maximum, which is normalized to the power value P calculated in the averager

,

,

, соответствующие точке максимума поворачивающие векторы

и значение углового спектра первого порядка

, значение нормированного максимума квадрата модуля углового спектра первого порядка L1, координаты максимума углового спектра первого порядка

.Thus, after the first stage, the following parameters are written into the memory: the average power of the received radio signals P, the angular spectrum of the first order

, the rotation vectors corresponding to the maximum point

and the value of the angular spectrum of the first order

, the value of the normalized maximum of the squared modulus of the first-order angular spectrum L1, coordinates of the maximum of the first-order angular spectrum

...

максимума углового спектра первого порядка5. The second stage of processing consists in reading the output parameters described in paragraph 4, determining the value of the normalized radiation pattern of the antenna array when orienting it in the direction of coordinates

the maximum of the angular spectrum of the first order

, которое в умножителе умножают на значение нормированной диаграммы направленности антенной решетки (1). Полученный результат вычитают в вычитателе из углового спектра первого порядка

, который поступает с выхода запоминающего устройства на первый вход вычитателя и в делителе делят на результат функционального преобразования нормированной диаграммы направленности решетки

. Таким образом, определяют угловой спектр второго порядкаSimultaneously with this, the maximum value of the angular spectrum of the first order is read from the random access memory

, which in the multiplier is multiplied by the value of the normalized radiation pattern of the antenna array (1). The result obtained is subtracted in a subtractor from the angular spectrum of the first order

, which comes from the output of the memory device to the first input of the subtractor and is divided in the divider by the result of the functional transformation of the normalized radiation pattern of the grating

... Thus, the angular spectrum of the second order is determined

.

...

и по следующим соотношениям находятся координаты максимума и его значение, нормированное на среднюю мощность PNext, the square of the modulus of the second-order angular spectrum is calculated

and the following relations are used to find the coordinates of the maximum and its value normalized to the average power P

,

,

.

...

соответствуют азимуту и углу места источника излучения с меньшей амплитудой радиосигнала.Maximum coordinates

correspond to the azimuth and elevation of the radiation source with a lower amplitude of the radio signal.

6. The final decision on the presence of radio signals and their number is made in the deciding device, where the statistics

compared with the first C1 threshold, selected in accordance with the Neumann-Pearson criterion, based on the given false alarm probability

If the threshold is not exceeded, a decision is made about the absence of signals; otherwise, the ratio of the form is determined and compared with the second threshold C2

.

...

The C2 threshold is also selected based on the Neumann-Pearson criterion, providing a given false alarm probability.

, в противном случае – решение о наличии радиосигналов двух источников с углами прихода

и

.7. When the second threshold C2 is exceeded, a decision is made on the presence of a radio signal from one source with angles of arrival

, otherwise - the decision on the presence of radio signals from two sources with angles of arrival

and

...

In accordance with the above description, the prototype method has the following disadvantages:

.1. The decisive rule (clauses 5-6) of the prototype method is valid when the antennas of the detector-direction finder are identical and non-directional, and their radiation patterns have a unit amplitude, independent of the direction of arrival of radio waves from radio sources, and are described by functions of the form

...

In the general case, in the presence of mutual influences in the AS of the detector-direction finder, as well as in the case of using amplitude-directed antenna elements for the decisive statistics described in clauses 5-6, they become invalid, which leads to a deterioration in the efficiency indicators of the specified method and determines the limitation its applicability.

2. The problem of detection and direction finding is solved for each spectral count independently, the prototype method does not imply the implementation of the procedure for identifying and accumulating spectral counts in the event that a decision is made about the belonging of radio emissions to the same source. This leads to an increase in computational costs when implementing this method for each spectral sample of a radio signal, and does not allow, due to an increase in the amount of information used when accumulating spectral samples of radio signals, to increase the efficiency of their subsequent digital processing, including the procedure for direction finding of radio emission sources.

3. The prototype method does not allow evaluating the ratio of the signal levels received from various frequency inseparable sources. This assessment, together with the assessment of directions to sources, provides an increase in the efficiency of solving a number of important practical problems of radio monitoring, for example, the problems of monitoring radiation from sources in conditions of deliberate interference.

4. In a number of practical situations when receiving radio signals from two frequency-inseparable sources, depending on the ratio of the received signal levels and their directions of arrival, as well as the structure and directivity characteristics of the AS detector-direction finder elements, the use of single-signal detection and direction finding (in particular, used in the method -prototype, the formation of a first-order angular spectrum and finding, by the position of its maximum, the azimuth and elevation estimates corresponding to the source with the maximum amplitude) can lead to missing signals or false alarms. Therefore, the use of the result of one-dimensional global maximization in the presence of two sources of radio signals is generally not advisable, since the azimuth and elevation estimate obtained as a result of maximizing the angular spectrum of the first order is a random variable that depends on many factors, including the ratio of the received signal levels , the center frequency of the received signals and their spatial diversity.

These disadvantages determine the limitations of the scope of application of the prototype method, which, under conditions of a priori uncertainty about the levels of received signals, their directions of arrival, noise intensity and the number of radio signal sources, which are characteristic for radio monitoring, and their presence does not allow the use of the prototype method in modern (promising) multichannel radio monitoring systems.

The problem to be solved by the proposed method is to increase the efficiency indicators of the adaptive spatial-multichannel detection and direction finding of two frequency-inseparable sources of radio signals under conditions of a priori uncertainty about the levels of received signals, their directions of arrival, the noise intensity and the number of radio signal sources typical for radio monitoring, including at close energies of received radio signals.

To solve this problem in the method of adaptive spatial-multichannel detection and direction finding of two frequency-inseparable sources of radio emission, including the synchronous reception of time realizations from the outputs of all antennas of the antenna system (AS) in the spatial channels of the detector-direction finder, simultaneously falling into the current reception (analysis) band , synchronous transformation of temporal realizations into digital form, calculation of fast Fourier transform samples of each digitized implementation in each spatial channel of the detector-direction finder, according to the invention , the accumulation of mutual energy matrices formed according to the accepted temporal realizations is realized, the computation of the first decision statistics

,

,

Where

,

,

- матрица коэффициентов межканальной корреляции аддитивного шума (при отсутствии корреляции шума матрица является диагональной единичной),

- matrix of coefficients of interchannel correlation of additive noise (in the absence of correlation of noise, the matrix is a diagonal unit),

(•) ^-1 - inverse matrix,

nb - serial number of the spectral sample (nb = 1, ... Nb),

Tr (•) - matrix trace operator (sum of diagonal elements),

(•) ^H is the Hermitian conjugation operator;

h, m = 1 ... N - indices of spatial channels;

comparison of the decision statistics with the lower threshold C1 and the upper threshold C2, calculated in accordance with the Neumann-Pearson criterion and providing the required constant false alarm probability; if the second threshold C2 is exceeded, a decision is made that the spectral readout corresponds to the signal of one radio emission source and the estimation of the azimuth and elevation angle is calculated using the formula:

,

,

Where

- пеленгационный рельеф,

- direction finding relief,

- векторная комплексная диаграмма направленности АС с произвольной структурой и характеристиками направленности антенных элементов;

- vector complex directivity diagram of an AU with an arbitrary structure and directivity characteristics of antenna elements;

if the first threshold C1 is not exceeded, a decision is made that the spectral sample is noisy; the corresponding readings are accumulated and averaged according to the formula

,

,

where b is the index of summation over "noise" spectral readings (b = 1, ..., B);

B is the number of spectral samples classified as noise;

- диагональные элементы матрицы взаимных энергий

- diagonal elements of the matrix of mutual energies

noise spectral samples;

n is the ordinal number of the AC element (n = 1 ... N);

N is the number of antenna elements;

P is an estimate of the average noise power;

if the spectral sample falls into the "uncertainty zone" - (between the lower C1 and the upper C2 thresholds, additional processing is implemented, which includes a block for processing spectral samples referred to the "uncertainty zone" at the stage of selection: calculation of the second decisive statistics

and comparing it with the third threshold C3, in case of exceeding the threshold - grouping and accumulation of spectral readings, formation and calculation of the global maximum of the direction finding relief; formation of the third decisive statistics

and comparing it with the fourth threshold C4; in case of exceeding the threshold - making a decision that the spectral readout corresponds to signals from two sources of radio emission and calculating estimates of directions and levels of received signals.

The claimed method is as follows.

Each FFT sample of temporal realizations is a complex amplitude in an elementary frequency channel (ECH), the bandwidth of which is inversely proportional to the duration of the temporal realization. The set of spectral readings in all N spatial channels of the detector-direction finder, belonging to the same ECH, characterizes the distribution of the radio wave incident on the speaker at the frequency of this ECH.

Spectral representation of temporal realizations provides the ability to determine the spectral composition of radio signals (that is, a set of FFT readings belonging to radio signals of one, in the case of one-signal detection, or two, in the case of two-signal detection, radio signal sources) with a priori uncertainty available in real conditions.

Among the set of spectral samples in the current reception (analysis) band, "single-signal" samples, noise samples and samples that fall into the "uncertainty zone" are determined, which can refer to both "single-signal" and "two-signal" samples. Spectral readings that have fallen into the "zone of uncertainty" are subject to additional processing, as a result of which a decision is made whether the readings belong to "one-signal" or "two-signal" readings.

Thus, as a result of solving the problem, the proposed method of adaptive spatial-multichannel detection and direction finding of two frequency-inseparable sources of radio emission involves the following procedures:

1. Synchronous reception of time realizations from the outputs of all N (N≥2) AC antennas in the spatial channels of the detector-direction finder, simultaneously falling into the current reception (analysis) band, synchronous transformation of time realizations into digital form, calculation of the Fourier transform counts of the digitized implementation in each spatial channel OP.

2. Synchronous measurement at the antenna outputs of the complex amplitudes of radio signals by a multichannel digital radio receiver with the number of channels equal to the number of antennas by using the FFT

,

,

Where

- векторная комплексная диаграмма направленности АС с произвольной структурой и характеристиками направленности антенных элементов;

- vector complex directivity diagram of an AU with an arbitrary structure and directivity characteristics of antenna elements;

The azimuth reading is carried out clockwise from the northern direction, the elevation angle is measured from the Earth's surface. The values of the quantities are calculated with a predetermined (for example, 1 °) discreteness, determined by the required direction finding accuracy, and are entered into a memory device before starting work. Thus, with a bearing within 360 ° in azimuth and 90 ° in elevation, the total storage capacity is 360⋅90⋅N complex numbers.

The obtained values are stored in a buffer memory for the duration of subsequent processing, which, in contrast to the prototype, includes three stages.

односигнального корреляционного обнаружения3. At the first stage, the complex amplitudes of the radio signals are read sequentially. Further, in contrast to the prototype, to calculate the average power P, primary two-threshold correlation detection is performed for all spectral samples, according to the results of which the spectral samples of the reception (analysis) band are divided into three groups: noise (not containing information about radio signal sources) containing information about signal from one source and samples that contain information about two sources of radio signals. The channel and mutual energies of spectral samples are calculated, which are accumulated over time realizations, and the proposed in [Artemov ML, Afanasyev OV, Abramova EL, Slichenko MP is calculated. A method for adaptive spatial-multichannel detection of spectral components of signals from radio sources. RF patent No. 2696022, G01S 5/04] statistics

single signal correlation detection

, (2)

, (2)

Where

,

,

- матрица коэффициентов межканальной корреляции аддитивного шума (при отсутствии корреляции шума матрица является диагональной единичной),

- matrix of coefficients of interchannel correlation of additive noise (in the absence of correlation of noise, the matrix is a diagonal unit),

(•) ^-1 - inverse matrix,

nb - serial number of the spectral sample (nb = 1, ... Nb),

Tr (•) - matrix trace operator (sum of diagonal elements),

(•) ^H is the Hermitian conjugation operator;

h, m = 1 ... N - indices of spatial channels;

which is compared with the lower threshold C1 and the upper threshold C2 (C1≤ρ≤C2).

If the lower threshold C1 is not exceeded, then a decision is made that this spectral sample is noisy. Spectral readings, referred to as noise, are subsequently averaged.

,

,

where b is the index of summation over "noise" spectral readings (b = 1, ..., B);

B is the number of spectral samples classified as noise;

- диагональные элементы матрицы взаимных энергий шумовых спектральных отсчетов.

- diagonal elements of the matrix of mutual energies of noise spectral samples.

The result of averaging (3) is an estimate of the average noise power, which is calculated not for all spectral samples, but only for those that are classified as noise. If the upper threshold C2 is exceeded, then the decision is made that the spectral sample contains information about the signal from one source of radio emission and the number of the corresponding spectral sample is written into the memory device.

In the case when the value of the statistics is within the "zone of uncertainty" within the interval from C1 to C2, the spectral sample can belong both to the signal of one SIR, and to signals from two SIR. In this case, the number of the corresponding spectral sample is recorded in the memory device for its subsequent processing.

Thus, the following parameters are recorded in the memory device: average power of noise samples (estimate of noise variance), numbers of spectral samples assigned to a signal from one source, and numbers of spectral samples that fall into the "uncertainty zone".

4. Unlike the prototype (item 4 of the description of the prototype), in the proposed method at the second stage of detection and direction finding of spectral readings, statistics of energy detection are generated.

For spectral samples that have exceeded the upper threshold of C2, one-signal two-dimensional direction finding is used, described in detail in the article [ML Artemov, MP Slichenko. Modern approach to the development of methods for direction finding radio waves of radio emission sources // Antenny. 2018. No. 5. S. 31-37.]

,

,

Where

- пеленгационный рельеф,

- direction finding relief,

- векторная комплексная диаграмма направленности АС с произвольной структурой и характеристиками направленности антенных элементов,

- vector complex directivity diagram of an AU with an arbitrary structure and directivity characteristics of antenna elements,

and the procedure for identifying spectral readings by belonging to one source of radio emission according to [Artemov ML, Afanasyev OV, Abramova EL, Konenkov EA, Slichenko MP is performed]. A method for adaptive identification of spectral samples by belonging to the signal of one radio emission source. RF patent No. 2696093, G01S 5/04].

For each spectral report assigned at stage 1 (clause 3) to the "zone of uncertainty", the following statistics are calculated

,

,

and is compared to the C3 threshold. If the threshold is not exceeded (γ≤C3), then a decision is made that the spectral sample belongs to a signal with a low level of received energy emitted by one radio signal source. If the statistics turns out to be greater than the threshold (γ> C3), then a decision is made about the presence of a signal from one or two sources and a direction finding relief is formed.

Thus, at the end of the second stage, the following output parameters are stored: an estimate of the average noise power, the numbers of spectral samples that fell into the "zone of uncertainty" at the first stage, and the mutual energy matrix for the corresponding numbers of spectral samples.

5. To resolve the uncertainty about the number of sources, a two-beacle acquisition and direction finding procedure is applied. For this, a direction finding relief M (θ ₁ , β ₁ , θ ₂ , β ₂ ) is formed, which is a function of the direction angles to two radio signal sources, that is, a joint estimate of azimuths and elevation angles is found by global maximization of the direction finding relief

следующей статистики6. The decisive rule for deciding whether to receive signals from one or two sources is in comparison with the threshold

following statistics

.

...

), выносится решение о наличии сигнала от одного источника.If the threshold is not exceeded (

), a decision is made on the presence of a signal from one source.

), то принимается решение о наличии сигналов от двух источников. Оценка направления

на каждый источник определяется как аргументы глобального максимума пеленгационного рельефа

, а соотношение принимаемых уровней сигналов находятся по формулам:If the threshold is exceeded (

), then a decision is made on the presence of signals from two sources. Direction assessment

for each source is defined as arguments of the global maximum of the direction finding relief

, and the ratio of the received signal levels are found by the formulas:

,

,

Where

,

,

- десятичный логарифм.

- decimal logarithm.

The parameters (C1, C2, C3, C4), which are the detection thresholds and specified in points 3, 4, 6, are selected in accordance with the Neumann-Pearson criterion and provide the required constant false alarm probability.

The proposed method of adaptive spatial-multichannel detection and direction finding of two frequency-inseparable sources of radio emission is devoid of the listed disadvantages of the prototype, namely:

1. The rules for making decisions on the number of radio signal sources (clauses 3, 4, 6) of the proposed method are valid in the case of AS with an arbitrary structure and directivity characteristics of antenna elements, and in particular, under the assumption that the antennas of the detector-direction finder are identical and undirected. This allows the proposed method to be used in real operating conditions of detectors-direction finders, when there are mutual influences of antennas on each other.

2. The proposed method implements the accumulation procedure for each spectral sample of the mutual energy matrices, which allows, in the case of monopulse reception of time realizations, to provide an increase in the identification efficiency indicators by increasing the output signal-to-noise ratio, in turn, the procedure for forming the angular spectrum proposed in the prototype, does not imply the accumulation of spectral components of signals, which does not allow, due to the accumulation of information, to increase the efficiency indicators of the subsequent direction finding of IRI.

3. In the described method, direction finding is carried out not for each spectral sample, but for a set of samples identified by belonging to the same source, which significantly reduces the computational costs when implementing the method in the equipment of radio monitoring systems.

4. The proposed method evaluates the received signal levels from various frequency inseparable sources. This information provides additional knowledge about radio signal sources and, as a result, improves the efficiency of estimating the number of radio signal sources and their direction finding.

, что уменьшает вероятность пропуска сигналов или ложных срабатываний. Использование результата глобальной максимизации пеленгационного рельефа и вычисление совместных оценок направлений прихода радиоволн, позволяет повысить точность соответствующих оценок и тем самым уменьшить вероятность пропуска сигналов и вероятность ложного обнаружения.5. In the proposed method for assessing the azimuths and elevation angles from both sources, they are found together according to the positions of the global maximum of the direction finding relief

, which reduces the likelihood of missing signals or false alarms. The use of the result of global maximization of the direction finding relief and the calculation of joint estimates of the directions of arrival of radio waves makes it possible to increase the accuracy of the corresponding estimates and thereby reduce the probability of missing signals and the probability of false detection.

The proposed method provides the possibility of adaptive spatial-multichannel detection and direction finding of two frequency-inseparable sources of radio signals with close energy levels of received signals under conditions of a priori uncertainty about the levels of received signals, their directions of arrival, noise intensity, and the number of radio signal sources typical for radio monitoring.

A block diagram of a device for implementing the proposed method (detector-direction finder), shown in Fig. 1 and FIG. 2

FIG. 1 the following designations are adopted:

1 - N-channel (N> 3) antenna system (AS);

2 - N-channel radio receiving device (RPU), providing multiple N-channel reception of temporary realizations;

3 - block for digitizing temporary realizations;

4 - block for calculating the fast Fourier transform (FFT) of time implementations;

5 - the first memory device, which stores the spectral samples of the received signals;

6 - block for selection of all spectral samples, which includes the following sub-blocks:

6.1 - block of formation of matrices of mutual energies;

6.2 - the second memory containing the matrix of mutual energies;

6.3 - block for calculating the first decisive statistics;

6.4 - the first two-threshold solver;

6.5 - the third storage device containing the numbers of spectral samples that fell into the "zone of uncertainty";

6.6 - the fourth memory containing the numbers of spectral samples exceeded the second threshold C2;

6.7 - block for identification and grouping of spectral samples according to their belonging to one radio signal source;

6.8 - unit of one-signal direction finding;

;6.9 - block for estimating the average noise power from a count that does not exceed the first threshold

;

6.10 - the fifth memory device containing the result calculated in block 6.9.

FIG. 2 indicates:

7 - block for processing spectral readings referred at the stage of selection (clauses 6.1 - 6.10) to the "zone of uncertainty", which includes the following blocks:

7.1 - block for calculating the second decisive statistics;

7.2 - the second solver;

7.3 - sixth memory containing the numbers of spectral samples exceeding the third threshold C3;

7.4 - block of clustering of spectral samples (threshold grouping by frequency proximity);

7.5 - block for calculating the weighted average frequency for each cluster and accumulating mutual energies by belonging to one cluster;

7.6 - seventh storage device (accumulated mutual energies of each cluster);

;7.7 - block for storing an array of values of a vector complex radiation pattern

;

7.8 - block for the formation of direction finding relief;

7.9 - block for calculating the global maximum of the directional relief;

7.10 - block for calculating the third decisive statistics;

7.11 - the third deciding device;

7.12 - block for searching for the position of the global direction finding relief;

7.13 - block for evaluating the ratio of the received signal levels.

The device contains a series-connected N-channel AC, N-channel RPU 2, a block for digitizing time realizations 3, an FFT 4 and a first memory device 5, the output of which is connected to the input of the selection unit of all spectral samples 6, which is the input of the block for generating mutual energies 6.1, output which, through the series-connected second memory 6.2, the first decision statistics calculator 6.3, the first two-threshold solver 6.4 is connected to the input of the third memory 6.5, the output of which is the first output of the selection unit of all spectral samples 6. In addition, the second output of the first two-threshold solver 6.4 through the unit for estimating the average noise power 6.9 is connected to the input of the fifth storage device 6.10, the output of which is the second output of the selection unit of all spectral samples 6. The third output of the first two-threshold solver 6.4 through serially connected fourth storage device 6.6 and the block for identification and grouping of spectral samples according to belonging to one radio signal source 6.7 is connected to the input of the single-signal direction finding block 6.8. The second output of the second memory 6.2 is the third output of the selection unit for all spectral samples 6. The first, second and third outputs of the selection unit for all spectral samples 6 are connected to the corresponding inputs of the spectral samples processing unit 7, which are inputs of the calculation unit for the second decisive statistics 7.1, the output of which is through connected in series the second solver 7.2, the sixth memory device 7.3, the clustering unit for spectral counts 7.4, the unit for calculating the weighted average frequency for each cluster and accumulating mutual energies by belonging to one cluster 7.5, the seventh memory device 7.6, the unit for forming the direction finding relief 7.8, the unit for calculating the global the maximum of the direction finding relief 7.9 and the block for calculating the third decisive statistics 7.10 is connected to the input of the third decider 7.11, the output of which is connected to the inputs of the block for searching the position of the global maximum of the direction finding relief 7.12 and the block how to assess the ratio of the levels of received signals 7.13, the outputs of which are the outputs of the device. The first input of the block for calculating the second decision statistics 7.1 is connected to the second input of the block for calculating the third decision statistics 7.10. The third input of the block for calculating the second decisive statistics 7.1 is connected to the second input of the block for calculating the weighted average frequency for each cluster and accumulating mutual energies by belonging to one cluster 7.5. The output of the block for storing the array of values of the vector complex directional pattern is connected to the second input of the block for forming the direction finding relief 7.8.

The device works as follows.

принимает временные реализации, поступающие затем в блок 2, который осуществляет многократный последовательный во времени синхронный (когерентный) прием временных реализаций с выходов всех антенн АС в пространственных каналах обнаружителя-пеленгатора. Затем блок 3 синхронно преобразует принятые временные реализации в цифровую форму. В блоке 4 для каждой оцифрованной реализации в каждом пространственном канале обнаружителя-пеленгатора происходит вычисление отсчетов преобразования ФурьеN-channel speaker with complex vector pattern

receives time realizations, which then arrive at block 2, which carries out multiple time-sequential synchronous (coherent) reception of time realizations from the outputs of all AC antennas in the spatial channels of the detector-direction finder. Then block 3 synchronously converts the received temporary realizations into digital form. In block 4, for each digitized implementation in each spatial channel of the detector-direction finder, the Fourier transform counts are calculated

,

,

where n = 1 ... N - spatial channel indices;

nb is the serial number of the spectral sample.

Block 5 provides registration of complex amplitudes of radio signals for the time of subsequent processing.

In block 6, which consists of a set of blocks 6.1 - 6.10, the selection of all spectral samples is realized according to the belonging of the spectral sample to a signal from one source, to noise, or to a "zone of uncertainty". In this case, in block 6.1, a matrix of mutual energies is formed for each spectral sample

,

,

where (•) ^* operator of complex conjugation;

and is stored for the duration of processing in block 6.2.

In block 6.3, the first decision statistics of the correlation detection for each spectral sample is calculated according to the formula (2).

сравнивается с двумя порогами. In block 6.4 decisive statistics

is compared to two thresholds.

If the first threshold is not exceeded (ρ <C1), the corresponding spectral samples in block 6.9 are accumulated, averaged and give an estimate of the average noise power

.

...

The fifth memory of block 6.10 is designed to store the average noise power value calculated in block 6.9.

If, in block 6.4, a decision is made that the spectral sample has fallen into the "uncertainty zone" (C1≤ρ≤C2), then the corresponding spectral sample is stored in block 6.5.

If the correlation statistics generated in block 6.3 exceeds the upper threshold (ρ> C2), the number of the corresponding spectral sample goes to the input of block 6.6, then to the block for identification and grouping of spectral samples 6.7 and from its output goes to the input of the single-signal direction finding block 6.8, in which the bearing and received signal level are estimated.

Thus, after the selection of all spectral samples, block 6.10 stores the value of the average noise power, which is then fed to the input of blocks 7.1 and 7.10. Block 6.5 stores the numbers of spectral samples referred to the "zone of uncertainty" arriving at the input of block 7.1. Block 6.2 provides storage of mutual energies of each spectral sample entering the input of blocks 7.1 and 7.5.

When calculating the second decision statistics in block 7.1, data is read from blocks 6.2, 6.5, 6.10

. Если в блоке 7.2 принимается решение о превышении порога (

), то номер соответствующего спектрального отсчета запоминается в блоке 7.3, обеспечивающем хранение всех спектральных отчетов, для которых энергетический порог оказался превышен. At the same time, block 7.2 compares the energy detection statistics calculated in block 7.1 for the corresponding spectral sample with the third threshold

... If in block 7.2 a decision is made to exceed the threshold (

), then the number of the corresponding spectral sample is stored in block 7.3, which provides storage of all spectral reports for which the energy threshold was exceeded.

From side 7.3, numbers of spectral samples that have exceeded the energy threshold are sent to the input of the threshold grouping block of spectral samples by belonging to one cluster 7.4, from the output of which the mutual energies of each cluster enter block 7.5, which calculates the weighted average frequency for each cluster and accumulates mutual energies by belonging to one cluster. The second input of block 7.5 receives data from the second storage device 6.2. The mutual energies accumulated in block 7.5 and the array of complex coefficients of the antenna system's directional pattern, stored in block 7.7, are fed to the input of the unit for forming the directional relief 7.8

The output parameter of block 7.9 and the estimate of the average noise power stored in block 6.10 are fed to the corresponding inputs of block 7.10, in which the third decision statistic is calculated, which is compared with the threshold in block 7.11. If the threshold is exceeded, then in blocks 7.12 and 7.13 estimates of azimuths and elevation angles are calculated, as well as estimates of the levels of received signals, respectively.

При моделировании аддитивные канальные шумы считались гауссовскими. To evaluate the technical result of the proposed method (to increase the efficiency of detection and direction finding when receiving frequency inseparable radio signals from two sources of radio emission with a priori uncertainty about the noise intensity, levels of received signals, their directions of arrival and the number of received signals characteristic of the radio monitoring task), a mathematical model was developed and modeling was carried out in the Matlab R2017b package. Simulation was performed for the reception of radio signals from two sources of radio emission by an antenna system with a vector complex directional pattern

In the simulation, the additive channel noise was assumed to be Gaussian.

The results of comparing the characteristics of the proposed method with the prototype [Ufaev VA, Ufaev DV, Khripushin VD, Khripushin DV, Shaidulin II, Kuznetsov AI. Method of detecting and direction finding radio signals. RF patent No. 2289146, G 01 S 5/04] are shown in Fig. 3, fig. 5 and FIG. 7.

The prototype method corresponds to the cross-sections of the angular spectra of the first and second order in Cartesian and polar coordinates shown in the indicated figures, constructed with the following parameter values: for FIG. 3 - the number of elements of the antenna system is equal to N = 15, the ratio of the radius of the antenna array to the wavelength of the received signals r / λ = 3.25, for Fig. 5 - N = 11, r / λ = 2, for Fig. 7 - N = 7, r / λ = 1.

The proposed method corresponds to the sections of the direction finding relief shown in the indicated figures in Cartesian and polar coordinates, constructed with the following parameter values:

for Fig. 4 - for parameters: N = 15, r / λ = 3.25, for Fig. 6 - N = 11, r / λ = 2,

for Fig. 8 - N = 7, r / λ = 1.

и

соответственно.In this case, the true directions of arrival of radio waves in Figures 3 - 8 are marked with dots and are equal to (θ ₀₁ , β ₀₁ , θ ₀₂ , β ₀₂ ) = (180 °, 45 °, 170 °, 35 °). The signal-to-noise ratio of the first and second sources are equal

and

respectively.

The graphs show that the prototype has a limited area of applicability. So, with a decrease in the number of antenna elements N and the value of r / λ, the estimate obtained by the method of global maximization of the first-order angular spectrum is unstable. It can be seen that in FIG. 3, the estimate is close to the true value, however, as the parameters N and r / λ decrease (Fig. 5), the estimate bias increases, and in Fig. 7 it can be seen that the direction estimate is located between the two sources. This leads to an error in the formation of the angular spectrum of the second order and the calculation by the position of its maximum of the direction estimates corresponding to a source with a lower received signal level, an increase in the probability of skipping and false reception of radio signals. From those shown in FIG. 4, 6, 8 graphs show that the proposed method provides a stable assessment of the direction of radiation received from two frequency inseparable SIR.

The achieved technical result is an increase in the efficiency of adaptive spatial-multichannel detection and direction finding of two frequency-inseparable sources of radio signals, which is quantitatively manifested in an increase in the probability of correct detection with a fixed probability of a false alarm, an increase in the reliability of determining the number of frequency-inseparable sources of radio signals, the accuracy and reliability of determining the directions of arrival and the ratio of the energy levels of the received radio signals under conditions of additive Gaussian noise of unknown intensity.

List of sources of information.

1. Tarasov G.A., Kabakov I.V., Nezvanov A.Yu. Method for multichannel detection and estimation of the number of radiation sources with adaptive equalization of the noise powers in the channel. RF patent No. 2204840,
G 01 S 3/00.

2. Shevchenko V.N., Emelyanov G. S., Vertogradov G. G. Method for detecting and determining two-dimensional bearing and frequency of radio emission sources. RF patent No. 2190236, G 01 S 5/04.

3. Ufaev V.A., Ufaev D.V., Khripushin V.D., Khripushin D.V., Shaidulin I.I., Kuznetsov A.I. Method of detecting and direction finding radio signals. RF patent No. 2289146, G 01 S 5/04.

4. Artemov M.L., Afanasyev O.V., Abramova E.L., Slichenko M.P. A method for adaptive spatial-multichannel detection of spectral components of signals from radio sources. RF patent No. 2696022, G 01 S 5/04.

5. Artemov M.L., Slichenko M.P. Modern approach to the development of methods for direction finding radio waves of radio emission sources // Antenny. 2018. No. 5. S. 31-37.

6. Artemov M.L., Afanasyev O.V., Abramova E.L., Konenkov E.A., Slichenko M.P. A method for adaptive identification of spectral samples by belonging to the signal of one radio emission source. RF patent No. 2696093, G 01 S 5/04.

Claims (29)

A method of adaptive spatially-multichannel detection and direction finding of two frequency-inseparable sources of radio emission, including the synchronous reception of time realizations from the outputs of all antennas of the antenna system (AS) in the spatial channels of the detector-direction finder, simultaneously falling into the current reception (analysis) band, synchronous transformation of time realizations into digital form, the calculation of the fast Fourier transform samples of each digitized implementation in each spatial channel of the detector-direction finder, characterized in that the accumulation of the mutual energy matrices formed according to the accepted time realizations is realized, the calculation of the first decisive statistics

, Where

,

- matrix of coefficients of interchannel correlation of additive noise (in the absence of correlation of noise, the matrix is diagonal unit), (•) ^-1 - inverse matrix, nb - serial number of the spectral sample (nb = 1, ... Nb), Tr (•) - matrix trace operator (sum of diagonal elements), (•) ^H is the Hermitian conjugation operator; h, m = 1 ... N - indices of spatial channels; comparing the decision statistics with the lower threshold C1 and the upper threshold C2, calculated in accordance with the Neumann-Pearson criterion and providing the required constant false alarm probability; if the second threshold C2 is exceeded, a decision is made that the spectral readout corresponds to the signal of one radio emission source and the estimation of the azimuth and elevation angle is calculated using the formula:

, Where

- direction finding relief,

- vector complex directivity diagram of an AU with an arbitrary structure and directivity characteristics of antenna elements; if the first threshold C1 is not exceeded, a decision is made that the spectral sample is noisy; the corresponding readings are accumulated and averaged according to the formula

, where b is the index of summation over "noise" spectral readings (b = 1, ..., B); B is the number of spectral samples classified as noise;

- diagonal elements of the matrix of mutual energies of noise spectral samples; n - serial number of the AC element (n = 1 ... N); N is the number of antenna elements; P is an estimate of the average noise power; if the spectral sample falls into the "uncertainty zone" - (between the lower C1 and the upper C2 thresholds, additional processing is implemented, which includes a block for processing spectral samples referred to the "uncertainty zone" at the stage of selection: calculation of the second decisive statistics

and comparing it with the third threshold C3, in case of exceeding the threshold - grouping and accumulation of spectral readings, formation and calculation of the global maximum of the direction finding relief; formation of the third decisive statistics

and comparing it with the fourth threshold C4; in case of exceeding the threshold - making a decision that the spectral readout corresponds to signals from two sources of radio emission and calculating estimates of directions and levels of received signals.

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