RU2546331C2 - Method of searching for small-sized mobile objects - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method is implemented by selecting transmitters that are superimposed in space and radiate at multiple frequencies of narrow-band and wide-band radio signals, and applying a new set of operations for combined processing of forward and object-scattered radio signals of the selected transmitters.

EFFECT: higher probability of small-sized mobile objects detection.

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Description

The invention relates to radio engineering and can be used in monitoring systems of land, sea and air space using direct and scattered objects of radio signals emitted by many uncontrolled and monitored transmitters of electronic systems for various purposes.

Achieving high efficiency in the detection, localization and identification of land, sea and air objects is limited by significant a priori uncertainty in size, spatial orientation, reflecting properties and parameters of the movement of objects, as well as the imperfection of known methods for detecting and tracking moving objects.

The technology of covert detection and tracking of moving objects, using natural radio illumination of targets created at a variety of frequencies by radio emissions from transmitters for various purposes in the short, meter, decimeter and centimeter wavelengths: broadcast (commercial FM broadcasting, high-definition television), information (communication) and measuring (control, navigation), has not yet received sufficient distribution, despite the fact that it can significantly increase the secrecy and effectiveness of detection, spatial localization and identification of an ever-increasing number of a wide class of small-sized moving objects.

A known method of searching for small-sized moving objects [1], which consists in selecting a transmitter emitting a spread spectrum radio signal, synchronously receiving an array of multipath radio signals including the direct radio signal of the transmitter and the radio signals of this transmitter scattered from objects, synchronously converting the ensemble of radio signals received by the antennas into digital signals, direct and compressed scattered signals are formed from digital signals, the selected direct and scattered signals are compared and time According to the time delays, Doppler shifts and directions of arrival, they perform the detection and spatial localization of moving objects.

This method does not contain coherent interference suppression in the form of a direct radio signal from the transmitter and, as a result, provides effective detection of only closely spaced and intensely reflecting objects.

More effective is the method of searching for small-sized moving objects [2], free from this drawback and selected as a prototype.

According to this method:

use direct and scattered by mobile objects radio signals emitted by transmitters of various electronic systems with continuous linear-frequency-modulated radio signals;

from time to time, asynchronously and synchronously with the irradiating signal, multipath radio signals are received at a plurality of search frequencies, including direct and scattered objects of the radio signals of the selected transmitter;

the received radio signals are converted to digital signals;

From digital signals by means of electronic compensation of incoherent and coherent interference, useful signals scattered by moving objects are distinguished by which objects are detected and spatially localized.

The prototype method through the selection of transmitters emitting linear frequency-modulated radio signals (LFM), and the use of electronic compensation of a wide class of coherent and incoherent interference provides a high probability of detection and accuracy of spatial localization of large moving objects.

However, the effectiveness of the prototype method in the search for small moving objects is sharply reduced.

резко снижается. В связи с этим при обнаружении малоразмерных подвижных объектов (типичные размеры малоразмерных подвижных объектов равны 0,5-5 м) применение источников подсвета ВЧ диапазона частот (2-30 МГц, длина волны 10-150 м) не эффективно и необходимо использование источников, функционирующих в более высокочастотных ОВЧ-УВЧ диапазонах (30-3000 МГц, длина волны 0,1-10 м). Однако в отличие от ВЧ диапазона частот, в котором независимо от времени суток функционирует множество ЛЧМ передатчиков, осуществляющих диагностику ионосферного канала распространения радиоволн, в ОВЧ-УВЧ диапазонах ЛЧМ передатчики используются не так широко и, как правило, кратковременно. В связи с этим возможность выбора и применения для подсвета малоразмерных целей ЛЧМ передатчиков существенно ограничена и, как следствие, вероятность обнаружения малоразмерных объектов с использованием способа-прототипа крайне низка.There are several reasons for this. The radio visibility of moving objects depends on the ratio of the characteristic dimensions of the object L to the wavelength of the light source λ and at $$\frac{2L}{\lambda }<<\mathrm{one}$$

sharply reduced. In this regard, when detecting small-sized moving objects (typical sizes of small-sized moving objects are 0.5-5 m), the use of high-frequency range illumination sources (2-30 MHz, wavelength 10-150 m) is not effective and it is necessary to use sources that operate in higher frequency VHF-UHF bands (30-3000 MHz, wavelength 0.1-10 m). However, unlike the HF frequency range, in which, irrespective of the time of the day, a lot of LFM transmitters operate that diagnose the ionospheric propagation channel of radio waves, in the VHF-UHF ranges of LFM transmitters are used not so widely and, as a rule, for a short time. In this regard, the possibility of selection and application for highlighting small-sized targets of LFM transmitters is significantly limited and, as a result, the probability of detecting small-sized objects using the prototype method is extremely low.

Thus, the disadvantage of the prototype method is the low probability of searching for small moving objects.

The technical result of the invention is to increase the likelihood of searching for small moving objects.

An increase in the search probability is achieved by choosing instead of transmitters emitting chirp radio signals, transmitters combined in space and emitting narrow-band and broadband radio signals at a variety of frequencies, as well as the use of a new set of operations for adaptive and combined processing of direct and diffused objects of radio signals of selected transmitters.

в сигнал комплексного двумерного изображения $$h_{\ell }^{(i\mathrm{,0})}={\left(A^{(i)H}{A}^{(i)}\right)}^{-1}{A}^{(i)H}{S}_{\ell }^{(i)},$$

где A^(i)H - матрица, эрмитово сопряженная с А⁽ⁱ⁾, сигнал $$h_{\ell }^{(i\mathrm{,0})}$$

запоминают и используют в качестве начального приближения, а также итерационно формируют зависящий от предыдущего решения вспомогательный матричный сигнал $$Л\left(h_{\ell }^{\left(i,k-1\right)}\right)\equiv diag\left\{{\left|h_{{\ell }_z}^{(i,k-1)}\right|}^{-1}/2\right\},$$

$$h_{{\ell }_z}^{\left(i,k-1\right)}$$

- z-й элемент вектора, $$h_{\ell }^{\left(i,k-1\right)}$$

, k=1,2,… - номер итерации, и сигнал очередного приближения двумерного изображения

, где λ - множитель Лагранжа, до тех пор, пока номер текущей итерации не превысит заданный порог, усредняют по частоте модули

элементов текущих двумерных изображений

, определяют по максимумам усредненного двумерного изображения

число рассеянных сигналов и фиксируют значения бистатической дальности d^(p) и бистатической скорости ν^(p) каждого p-го рассеянного сигнала, преобразуют каждый широкополосный опорный сигнал s^(j), j=1, …, K_j - номер частоты широкополосного радиосигнала в матричный сигнал комплексной фазирующей функции

, включающей гипотетические сигналы, рассеиваемые каждым потенциальным объектом с нулевой и найденной бистатической скоростью ν^(p) p-го рассеянного сигнала, запоминают матричные сигналы

, итерационно преобразуют каждый широкополосный разведываемый сигнал

с использованием матричного сигнала комплексной фазирующей функции

в сигнал текущего одномерного изображения

p-го рассеянного сигнала до тех пор, пока номер текущей итерации не превысит заданный порог, усредняют по частоте модули

элементов текущих одномерных изображений p-го рассеянного сигнала

, определяют по максимумам усредненного одномерного изображения

уточненное значение бистатической дальности

p-го рассеянного сигнала, по значениям выбранного азимутально-угломестного направления приема разведываемых сигналов, бистатической скорости ν^(p) и уточненной бистатической дальности

каждого p-го рассеянного сигнала обнаруживают и определяют пространственные координаты малоразмерных подвижных объектов.The technical result is achieved by the fact that in the method of searching for small-sized moving objects, which consists in the use of direct and scattered by moving objects radio signals emitted by transmitters of electronic systems for various purposes, according to the invention, select transmitters that are combined in space and emit narrow-band and broadband at a variety of frequencies radio signals that synchronously receive multipath signals, including direct and scattered radio signals, synchronously receive the received radio signals into digital signals, form and store narrow-band and wideband reference and reconnaissance signals from the digital signals for the given azimuth-elevation directions of reception, convert each narrow-band reference signal s ⁽ⁱ⁾ , i = 1, ..., K _i is the frequency number of the narrowband RF signal to the matrix signal phasing complex function a ^(i), consisting of hypothetical signals scattered by each potential object stored matrix signals a ⁽ⁱ⁾ for each ℓ-th approach elevation directions azimuthally receiving convert each narrowband signal scout $$s_{\ell }^{(i)}$$

into a complex two-dimensional image signal $$h_{\ell }^{(i0)}={\left(A^{(i)H}{A}^{(i)}\right)}^{-\mathrm{one}}{A}^{(i)H}{S}_{\ell }^{(i)},$$

where A ^{(i) H} is the Hermitian conjugate matrix with A ⁽ⁱ⁾ , the signal $$h_{\ell }^{(i0)}$$

remember and use as an initial approximation, and also iteratively form an auxiliary matrix signal depending on the previous solution $$L\left(h_{\ell }^{\left(i,k-\mathrm{one}\right)}\right)\equiv diag\left\{{\left|h_{{\ell }_z}^{(i,k-\mathrm{one})}\right|}^{-\mathrm{one}}/2\right\},$$

$$h_{{\ell }_z}^{\left(i,k-\mathrm{one}\right)}$$

is the zth element of the vector, $$h_{\ell }^{\left(i,k-\mathrm{one}\right)}$$

, k = 1,2, ... is the iteration number, and the signal of the next approximation of the two-dimensional image

, where λ is the Lagrange multiplier, until the current iteration number exceeds a given threshold, the modules are averaged over the frequency

elements of current two-dimensional images

, determined by the maxima of the averaged two-dimensional image

the number of scattered signals and fix the values of the bistatic range d ^(p) and the bistatic speed ν ^{(p) of} each p-th scattered signal, convert each broadband reference signal s ^(j) , j = 1, ..., K _j is the frequency number of the broadband radio signal in matrix signal of a complex phasing function

including hypothetical signals scattered by each potential object with zero and found bistatic velocity ν ^{(p) of the} pth scattered signal, matrix signals are stored

Iteratively Convert Each Broadband Scanned Signal

using a matrix signal of a complex phasing function

into the signal of the current one-dimensional image

p-th scattered signal until the current iteration number exceeds a predetermined threshold, the modules are averaged over the frequency

elements of the current one-dimensional images of the pth scattered signal

, determined by the maxima of the averaged one-dimensional image

adjusted bistatic range

of the p-th scattered signal, according to the values of the selected azimuth-elevation direction of reception of the reconnoitered signals, the bistatic velocity ν ^(p) and the refined bistatic range

each p-th scattered signal is detected and determined by the spatial coordinates of small-sized moving objects.

The operation of the method is illustrated in the drawing.

A device in which the proposed method is implemented comprises a reception system 1 connected in series, a radio transmitter modeling and selection system (RPD) 2, a computer system 3, and a control and indication unit 4.

In turn, the receiving system 1 includes N receiving paths 1-n, each of which consists of an antenna 1, a gain and switching device 2, K filtering and amplification modules 3-k and a multi-channel analog-to-digital converter (ADC) 4.

In this case, system 2 is connected to the input of block 4, and also has an interface for connecting to an external RPD base. In addition, block 4 has an output intended for connection to external systems.

System 1 is an analog-to-digital device and is designed for multichannel reception and analog-to-digital conversion of radio signals received on the set K = K _i + K _j . search frequencies of each of the N spatially separated antennas.

Each antenna 1 of the reception path 1-n is directional. The spatial configuration of the placement of the antennas can be arbitrary: flat rectangular, flat circular or surround, in particular conformal.

The amplification and switching device 2 of the reception path 1-n is designed to amplify and divide the multipath radio signal received by antenna 1 for subsequent filtering by frequency in K 3-k modules. In addition, the device 2 is intended for switching to the inputs of the modules 3-k of the signal of the calibration generator instead of the signal received by the antenna 1 (for simplicity, the calibration generator is not shown in the diagram).

A separate filtering and amplification module 3-k of the 1-n receiving path is built on the basis of a frequency converter and is designed to select the frequency of one of the signals received at the set K = K _i + K _j of search frequencies. The bandwidth of each 3-k module varies according to the spectrum width of the received radio signal.

The multi-channel ADC 4 contains K channels and is synchronized by the signal of the reference oscillator (for simplicity, the reference oscillator is not shown in the diagram). If the resolution and speed of the ADC are sufficient for direct analog-to-digital conversion of the input signals, then in the 3-k module instead of the frequency converter, a frequency-selective band-pass filter and amplifier can be used.

System 2 is a computing device and is designed to identify, select, and periodically update a set of transmitters that irradiate a given region of space with narrow-band and wide-band radio signals, as well as generate model signals of selected transmitters.

Computing system 3 is designed for two-stage iteratively implemented adaptive processing of reference and reconnaissance signals in order to detect and determine the parameters of detected small-sized moving objects.

The device operates as follows.

In system 2, based on the data of the external base of the radio transmitters, as well as data on the detected transmitters coming from the computing system 3, using the modeling software, a set of transmitters emitting narrow-band and wide-band radio signals is identified, selected and periodically updated. During the simulation, possible coverage areas, detection probabilities, and achievable localization accuracy of moving objects of various classes are estimated, which can be provided with various placement options for transmitters relative to a detection-direction finding station. In addition, model 2 transmitter signals are generated in system 2, which can be used instead of real direct transmitter signals with a priori known synchronization parameters. The parameters of the selected set of transmitters (number i = 1, ..., K _i and the carrier frequency of the narrowband signal, number j = 1, ..., K _j and the carrier frequency of the broadband signal, spectrum width, shape and power of the emitted signal, coordinates or distance and the angular position relative to the reception point) are stored in the system 2 and in block 4, and are also used to adjust the frequency of modules 3-k of the reception paths 1-n. In order to simplify the control circuit of the converters are not shown.

At the signal of block 4, the 3-k modules are tuned to the given i-th, i = 1, ..., K _i narrowband reception frequencies and jth, j = 1, ..., K _j broadband radio reception frequencies. Multipath radio signals, including direct transmit signals and scattered by the objects radio signals of these transmitters, are synchronously received by each of the N antennas on the set K = K _i + K _j search frequencies.

или широкополосный $$x_n^{(j)}\left(t\right)$$

радиосигнал после усиления и деления в устройствах 2 поступает на входы идентичных по номеру модулей фильтрации и усиления 3-k, где фильтруется по частоте.Narrowband received by the antennas of all N reception paths, depending on the antenna number n and time t $$x_n^{(i)}\left(t\right)$$

or broadband $$x_n^{(j)}\left(t\right)$$

the radio signal after amplification and division in devices 2 is fed to the inputs of the filter-identical and gain 3-k modules, identical in number, where it is filtered by frequency.

For example, a narrow-band radio signal at a carrier frequency with the number i = 1 goes to module 3-1 of each of the N reception paths 1-n, a narrow-band radio signal at a carrier frequency with the number i = 2 goes to module 3-2, and a broadband radio signal at the carrier frequency with the number j = 1 enters the module 3-3, etc.

и широкополосных $$x_n^{(j)}\left(t\right)$$

радиосигналов синхронно преобразуется с помощью АЦП 4 в ансамбли цифровых сигналов $$x_n^{(i)}\left(z\right)$$

и $$x_n^{(j)}\left(z\right)$$

, где z - номер временного отсчета сигнала. Ансамбли цифровых сигналов $$x_n^{(i)}\left(z\right)$$

и $$x_n^{(j)}\left(z\right)$$

поступают в вычислительную систему 3.Narrow-band ensembles formed in 3-k modules of all 1-n receive paths $$x_n^{(i)}\left(t\right)$$

and broadband $$x_n^{(j)}\left(t\right)$$

of radio signals is synchronously converted using ADC 4 into ensembles of digital signals $$x_n^{(i)}\left(z\right)$$

and $$x_n^{(j)}\left(z\right)$$

where z is the time reference number of the signal. Digital Signal Ensembles $$x_n^{(i)}\left(z\right)$$

and $$x_n^{(j)}\left(z\right)$$

enter the computing system 3.

In computing system 3, the following actions are performed:

и $$x_n^{(j)}\left(z\right)$$

для заданных азимутально-угломестных направлений приема формируются узкополосные s⁽ⁱ⁾  и широкополосные s^(j) опорные сигналы, а также узкополосные $$s_{\ell }^{(i)}$$

и широкополосные $$s_{\ell }^{(j)}$$

разведываемые сигналы.- from digital signals $$x_n^{(i)}\left(z\right)$$

 and $$x_n^{(j)}\left(z\right)$$

 for given azimuthal elevation directions, narrowband s are formed⁽ⁱ⁾ and broadband s^(j)reference signals as well as narrowband $$s_{\ell }^{(i)}$$

 and broadband $$s_{\ell }^{(j)}$$

 reconnaissance signals.

и $$x_n^{(j)}\left(z\right)$$

[3, стр. 7].The formation of reference and reconnoitered signals can be carried out in various ways, for example, by adaptive spatial filtering of digital signals $$x_n^{(i)}\left(z\right)$$

and $$x_n^{(j)}\left(z\right)$$

[3, p. 7].

сигналов выполняются следующие действия:Moreover, for example, to obtain narrow-band reference s ⁽ⁱ⁾ and narrow-band reconnaissance $$s_{\ell }^{(i)}$$

signals the following actions are performed:

преобразуется в матричный цифровой сигнал $$X^{(i)}=\left\{x_1^{(i)}\left(z\right),\dots ,x_n^{(i)}\left(z\right),\dots ,x_N^{(i)}\left(z\right)\right\}$$

и в сигнал пространственной корреляционной матрицы R⁽ⁱ⁾;- ensemble of digital signals $$x_n^{(i)}\left(z\right)$$

converted to matrix digital signal $$X^{(i)}=\left\{x_{\mathrm{one}}^{(i)}\left(z\right),...,x_n^{(i)}\left(z\right),...,x_N^{(i)}\left(z\right)\right\}$$

and into the signal of the spatial correlation matrix R ⁽ⁱ⁾ ;

для формирования разведываемых сигналов, где v⁽ⁱ⁾ - вектор наведения, определяемый азимутально-угломестным направлением приема радиосигнала, его частотой и геометрией решетки, ℓ - номер азимутально-угломестного направления приема разведываемого радиосигнала;- the signal of the correlation matrix R ^{(i) is} converted to the signal of the optimal weight vector w ⁽ⁱ⁾ = (R ⁽ⁱ⁾ ) ^-1 v ⁽ⁱ⁾ to form the reference signal and to the signals of the optimal weight vectors $$w_{\ell }^{(i)}={(R_{\ell }^{(i)})}^{-\mathrm{one}}{v}_{\ell }^{(i)}$$

for the formation of reconnoitered signals, where v ⁽ⁱ⁾ is the guidance vector determined by the azimuthal elevation direction of the reception of the radio signal, its frequency and lattice geometry, ℓ is the number of the azimuthal elevation direction of reception of the prospected radio signal;

сигналы, где (·)^H - символ эрмитова сопряжения.- the matrix digital signal X ^{(i) is} converted to a reference s ⁽ⁱ⁾ = w ^{(i) H} X ⁽ⁱ⁾ and $$s_{\ell }^{(i)}=w_{\ell }^{(i)H}{X}^{(i)}$$

signals, where (·) ^H is the symbol of Hermitian conjugation.

сигналов осуществляется аналогичным способом.The formation of broadband reference s ^(j) and broadband reconnaissance $$s_{\ell }^{(j)}$$

signals is carried out in a similar way.

и широкополосные разведываемые сигналы $$s_{\ell }^{(j)}$$

совместно со значением азимутально-угломестного направления приема запоминаются. Кроме того, опорные сигналы и их параметры (частота, азимутально-угломестное направление прихода и уровень сигнала) поступают в систему 2, где также запоминаются.Formed narrowband reference signals s ⁽ⁱ⁾ , wideband reference signals s ^(j) , as well as narrowband scanned signals $$s_{\ell }^{(i)}$$

and broadband reconnaissance signals $$s_{\ell }^{(j)}$$

together with the value of the azimuthal elevation direction of reception are remembered. In addition, the reference signals and their parameters (frequency, azimuth and elevation direction of arrival and signal level) enter the system 2, where they are also stored.

After that, the following operations are performed in the computing system 3:

- each narrow-band reference signal s ^{(i) is} converted into a matrix signal of a complex phasing function A ⁽ⁱ⁾ , including hypothetical signals scattered by each potential object, matrix signals A ^{(i) are} stored.

где $$s_b^{(i)}={\left[S_{(1-b)}^{(i)},\dots ,S_{(Z-b)}^{(i)}\right]}^T$$

- векторы размером Z×1, являющиеся сдвинутыми по времени на bT_s версиями опорного сигнала s⁽ⁱ⁾, b=0,…,B-1, В - число временных задержек прямого сигнала, T_s - период выборки сигнала;The conversion of the reference signal s ⁽ⁱ⁾ into a matrix signal A ^{(i) is} carried out according to the following formula: $$A^{(i)}=\left[D{s}_0^{(i)},...,D{s}_b^{(i)},...,D{s}_{B-\mathrm{one}}^{(i)}\right],$$

Where $$s_b^{(i)}={\left[S_{(\mathrm{one}-b)}^{(i)},...,S_{(Z-b)}^{(i)}\right]}^T$$

- vectors of size Z × 1, which are time shifted by bT _s versions of the reference signal s ⁽ⁱ⁾ , b = 0, ..., B-1, B is the number of time delays of the direct signal, T _s is the signal sampling period;

are the Doppler shift matrices, ξ = 0, ..., ± L, L is the size of the grid along the Doppler shift.

Thus, the columns of the matrix A ⁽ⁱ⁾ are time-delayed and frequency-shifted Doppler shifts versions of the reference signal s ⁽ⁱ⁾ , and the size of this matrix Z × B (2L + 1) is determined by the number of samples in the reconstructed signal (duration of the observation interval ) and the size of the coordinate grid for the time delay and Doppler frequency shift;

преобразуется в сигнал комплексного двумерного изображения

, где A^(i)H - матрица, эрмитово сопряженная с A⁽ⁱ⁾, сигнал

запоминается и используется в качестве начального приближения, а также итерационно формируются зависящий от предыдущего решения вспомогательный матричный сигнал

,

- z-й элемент вектора

, k=1, 2, … - номер итерации, и сигнал очередного приближения двумерного изображения

, где λ - множитель Лагранжа, до тех пор, пока номер текущей итерации не превысит заданный порог.- for each l-th azimuth-elevation direction of reception, each narrow-band reconnaissance signal

converted to a complex two-dimensional image signal

, where A ^{(i) H} is the Hermitian conjugate matrix with A ⁽ⁱ⁾ , the signal

is stored and used as an initial approximation, and an auxiliary matrix signal depending on the previous solution is iteratively generated

,

is the zth element of the vector

, k = 1, 2, ... is the iteration number, and the signal of the next approximation of the two-dimensional image

, where λ is the Lagrange multiplier, until the current iteration number exceeds a given threshold.

The experimentally set threshold value is 10:

элементов текущих двумерных изображений

.- then the modules are averaged over the frequency

elements of current two-dimensional images

.

This operation is proportional to the root of the number of frequencies N _i increases the signal-to-noise ratio and, as a result, increases the likelihood of detecting small objects in the analyzed l-th azimuth-elevation direction of reception;

число рассеянных сигналов и фиксируются значения бистатической дальности d^(p) и бистатической скорости ν^(p) каждого p-го рассеянного сигнала.- determined by the maxima of the averaged two-dimensional image

the number of scattered signals and the values of the bistatic range d ^(p) and the bistatic speed ν ^{(p) of} each p-th scattered signal are fixed.

This operation completes the two-dimensional processing of narrowband radio signals. The following operations use the bistatic velocity ν ^{(p) of} each p-th scattered signal obtained in the processing of narrow-band radio signals as a target designation for more cost-effective from the point of view of computing one-dimensional processing of broadband signals;

, включающей гипотетические сигналы, рассеиваемые каждым потенциальным объектом с нулевой и найденной бистатической скоростью ν^(p) p-го рассеянного сигнала, матричные сигналы

запоминаются.- each broadband reference signal s ^(j) is converted into a matrix signal of a complex phasing function

including hypothetical signals scattered by each potential object with zero and found bistatic velocity ν ^{(p) of the} pth scattered signal, matrix signals

remembered.

осуществляется по следующей формуле:

, где

- векторы размером Z×1, являющиеся сдвинутыми по времени на bT_s версиями опорного сигнала s^(j), b=0, …, B-1, B - число временных задержек прямого сигнала, T_s - период выборки сигнала;

- матрица доплеровских сдвигов, ξ′ - дискретное значение доплеровского сдвига частоты, соответствующее найденной бистатической скорости ν^(p) p-го рассеянного сигнала;Converting the wideband reference signal s ^(j) to a matrix signal

carried out according to the following formula:

where

- vectors of size Z × 1, which are time shifted by bT _s versions of the reference signal s ^(j) , b = 0, ..., B-1, B is the number of time delays of the direct signal, T _s is the signal sampling period;

is the matrix of Doppler shifts, ξ ′ is the discrete value of the Doppler frequency shift corresponding to the found bistatic velocity ν ^{(p) of the} pth scattered signal;

с использованием матричного сигнала комплексной фазирующей функции

в сигнал текущего одномерного изображения

p-го рассеянного сигнала до тех пор, пока номер текущей итерации не превысит заданный порог.- iteratively converts each broadband reconnaissance signal

using a matrix signal of a complex phasing function

into the signal of the current one-dimensional image

pth scattered signal until the current iteration number exceeds a given threshold.

The following actions are performed:

с использованием матричного сигнала комплексной фазирующей функции

преобразуется в сигнал текущего одномерного изображения p-го рассеянного сигнала

, где

- матрица, эрмитово сопряженная с

, сигнал

запоминается и используется в качестве начального приближения, а такжеevery broadband reconnaissance signal

using a matrix signal of a complex phasing function

converted to the signal of the current one-dimensional image of the pth scattered signal

where

is a Hermitian conjugate matrix

signal

remembered and used as an initial approximation, as well as

,

- z-й элемент вектора

, k=1, 2, … - номер итерации, и сигнал очередного приближения одномерного изображения

, где λ - множитель Лагранжа, до тех пор, пока номер текущей итерации не превысит заданный порог. Значение порога выбирается равным 10.an auxiliary matrix signal depending on the previous solution is iteratively formed

,

is the zth element of the vector

, k = 1, 2, ... is the iteration number, and the signal of the next approximation of the one-dimensional image

, where λ is the Lagrange multiplier, until the current iteration number exceeds a given threshold. The threshold value is selected equal to 10.

After that, the following operations are performed in the computing system 3:

элементов текущих одномерных изображений p-го рассеянного сигнала

;- modules are averaged over frequency

elements of the current one-dimensional images of the pth scattered signal

;

уточненное значение бистатической дальности

p-го рассеянного сигнала.- determined by the maxima of the averaged one-dimensional image

adjusted bistatic range

pth scattered signal.

тем выше, чем больше число частот K_j. Кроме этого, степень уточнения значения бистатической дальности

растет с увеличением отношения ширины спектра широкополосного сигнала к ширине спектра узкополосного сигнала. Это обусловлено тем, что при фиксированном отношении сигнал/шум точность оценки дальности тем выше, чем больше ширина спектра сигнала источника подсвета. Так, если в качестве узкополосных сигналов подсвета выбраны сигналы радиостанций УКВ ЧМ радио (диапазон 88-108 МГц) с шириной спектра 100 кГц, а в качестве широкополосных - сигналы радиостанций цифрового телевизионного вещания (диапазон 450-860 МГц) с шириной спектра 7,6 МГц, выигрыш в точности оценивания бистатической дальности может достигать 7600/100=76 раз. Отметим, что пропорционально увеличению точности оценивания бистатической дальности растет вероятность обнаружения объектов, достигаемая на следующем этапе обработки сигналов;Note that the degree of refinement of the bistatic range value

the higher, the greater the number of frequencies K _j . In addition, the degree of refinement of the value of the bistatic range

grows with increasing ratio of the width of the spectrum of the broadband signal to the spectrum width of the narrowband signal. This is due to the fact that for a fixed signal-to-noise ratio, the accuracy of the range estimation is higher, the greater the width of the spectrum of the signal of the backlight. So, if the signals of VHF FM radio stations (range 88-108 MHz) with a spectrum width of 100 kHz are selected as narrowband backlight signals, and the signals of digital television broadcasting radio stations (range 450-860 MHz) with a spectrum width of 7.6 are selected as broadband signals MHz, the gain in the accuracy of estimating the bistatic range can reach 7600/100 = 76 times. Note that in proportion to the increase in the accuracy of estimating the bistatic range, the probability of detecting objects is increased, which is achieved at the next stage of signal processing;

каждого p-го рассеянного сигнала обнаруживаются и определяются пространственные координаты малоразмерных подвижных объектов.- according to the values of the selected azimuthal elevation direction of reception of reconnaissance signals, bistatic speed ν ^(p) and refined bistatic range

of each p-th scattered signal, spatial coordinates of small-sized moving objects are detected and determined.

The detection and spatial localization of small-sized moving objects is carried out by known methods, for example [4].

The following actions are performed:

1) the values of the bistatic velocity ν ^{(p) of} each p-th scattered signal are compared with the threshold and, when the threshold is exceeded, decisions are made to detect the p-th moving object. The threshold is selected based on minimizing the probability of missing an object;

строится эллипсоид равных бистатических дальностей;2) by the values of the refined bistatic range

an ellipsoid of equal bistatic distances is built;

3) the geographic coordinates of the p-th detected object are determined by the intersection of the ellipsoid of equal bistatic ranges and the azimuth-elevation direction of reception of the pth scattered signal.

The device 4 displays the results of the detection and spatial localization of objects.

From the above description it follows that the proposed method is based on the fact of combining narrow-band radio and broadband television transmitters at one point in the space, for example, placing a combination of such transmitters on the Ostankino television tower. Due to this, the bistatic geometry of all possible transmitter-receiver pairs is aligned and the possibility of performing combined two-stage signal processing operations increases, which increases the likelihood of detecting small-sized moving objects. In this case, at the first stage, due to the small computational costs required when processing narrow-band radio signals, fast detection of target signals, high-precision determination of the bistatic speed, and coarse (due to the narrow width of the spectrum of radio signals) determination of the bistatic range of each target by processing direct and scattered radio signals are carried out. To increase the signal-to-noise ratio and, therefore, increase the probability of detection and the accuracy of estimating the parameters of radio signals scattered by small-sized objects, new iteratively implemented adaptive processing operations are used to increase the resolution and dynamic range of synthesis of the time-frequency image of radio signals scattered by controlled objects, and also averaging information obtained using several narrowband backlight transmitters. The values of the bistatic velocity of the objects obtained at the first stage are used at the second stage to refine their bistatic ranges. In this case, instead of the traditionally performed two-dimensional processing, using the bistatic velocity values obtained at the first stage as target designation, one-dimensional adaptive processing of broadband radio signals scattered by objects is performed. By averaging the obtained specified bistatic ranges, an additional increase in the probability of detection and the accuracy of determining the bistatic ranges of small-sized moving objects is achieved.

Thus, due to the choice of transmitters combined in space and emitting narrow-band and wide-band radio signals at a variety of frequencies, as well as the use of a new set of operations of adaptive and combined processing of direct and diffused objects of the radio signals of the selected transmitters, it is possible to solve the problem with the achievement of the specified technical result.

Information sources

1. US patent 7,012,552 B2, class G08B 21/00, 2006

2. RU, patent, 2,440,588 C1, cl. G01S 13/02, 2012

3. Ratynsky M.V. Adaptation and superresolution in antenna arrays. M: Radio and communications, 2003.

4. RU, patent, 2 444 754, cl. G01S 13/02, 2012

Claims (1)

The method of searching for small-sized moving objects, which consists in the use of direct and scattered by moving objects radio signals emitted by transmitters of electronic systems for various purposes, characterized in that they select transmitters combined in space and emitting narrow-band and wide-band radio signals on a plurality of frequencies, and simultaneously receive on a plurality of search frequencies, multipath signals, including direct and scattered radio signals, synchronously convert the received radio signals into digital signals s from a digital signal form and stored narrowband and broadband support and both exploration signals for given azimuth-elevation direction of reception, convert each narrowband reference signal s ^{(i), i} = 1, ..., K _i - frequency number narrowband RF signal to the matrix signal complex the phasing function A ⁽ⁱ⁾ , including hypothetical signals scattered by each potential object, store matrix signals A ⁽ⁱ⁾ , for each l-th azimuth-elevation direction, each narrow-band transform signal

into a complex two-dimensional image signal

, where A ^{(i) H} is the Hermitian conjugate matrix with A ⁽ⁱ⁾ , the signal

remember and use as an initial approximation, and also iteratively form an auxiliary matrix signal depending on the previous solution

,

is the zth element of the vector

, k = 1, 2, ... is the iteration number, and the signal of the next approximation of the two-dimensional image

, where λ is the Lagrange multiplier, until the current iteration number exceeds a given threshold, the modules are averaged over the frequency

elements of current two-dimensional images

, determined by the maxima of the averaged two-dimensional image

the number of scattered signals and fix the values of the bistatic range d ^(p) and the bistatic speed ν ^{(p) of} each p-th scattered signal, convert each broadband reference signal s ^(j) , j = 1, ..., K _j is the frequency number of the broadband radio signal in matrix signal of a complex phasing function

including hypothetical signals scattered by each potential object with zero and found bistatic velocity ν ^{(p) of the} pth scattered signal, matrix signals are stored

Iteratively Convert Each Broadband Scanned Signal

using a matrix signal of a complex phasing function

into the signal of the current one-dimensional image

p-th scattered signal until the current iteration number exceeds a predetermined threshold, the modules are averaged over the frequency

elements of the current one-dimensional images of the pth scattered signal

, determined by the maxima of the averaged one-dimensional image

adjusted bistatic range

of the p-th scattered signal, according to the values of the selected azimuth-elevation direction of reception of the reconnoitered signals, the bistatic speed ν ^(p) and the adjusted bistatic range

each p-th scattered signal is detected and determined by the spatial coordinates of small-sized moving objects.