RU2444755C1 - Method for detection and spatial localisation of air objects - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: effect is achieved owing to using adaptive spatial filtration operations providing directional reception of useful straight radio signal of illumination transmitter and useful dissipated signal with simultaneous suppression of interference of wide class, which come from other directions, as well as operations of radio electronic compensation of coherent interference from strong straight radio signal of illumination transmitter screening weak dissipated signals.

EFFECT: increasing the sensitivity of detection and accuracy of spatial localisation of air objects of wide range.

2 dwg

Description

The invention relates to radio engineering and can be used in airspace control systems using direct and diffused signals from airborne objects emitted by many uncontrolled and controlled transmitters of electronic systems for various purposes.

Achieving high efficiency in the detection, localization and identification of airborne 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 airborne objects.

A technology for passive detection and tracking of airborne objects using natural illumination of airborne targets created at a variety of frequencies by radio emissions from various transmitters 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 stealth and effectively detection, spatial localization and identification of a wide class of moving objects.

A known method for the detection and spatial localization of airborne objects [1], which consists in the fact that

receive multi-frequency radio signals in the reception band many times greater than the spectrum width of a single radio signal of the transmitter by the array of antennas, form the complex time spectra of the radio signals of each antenna and the power spectrum of the radio signal of the reference antenna,

the power spectrum of the radio signal of the reference antenna detect the signals of the transmitters,

the complex time spectra form the two-dimensional complex angular spectra of the detected transmitters,

azimuthal and elevation bearings of the transmitters are determined from the angular spectra,

and after comparing elevation bearings β with a threshold, the transmitters are divided into ground and air and the oblique range R to the air target transmitters is determined by the formula R = H / sinβ, where H is the known target altitude.

This method provides effective detection of airborne objects equipped with radio signal transmitters. However, in conditions of radio silence, this method loses its effectiveness.

More effective is the method for the detection and spatial localization of airborne objects [2], free from this drawback and selected as a prototype. According to this method:

choose a transmitter emitting a spread spectrum radio signal,

synchronously receive an array of N antennas a multipath radio signal, including a direct radio signal of the transmitter and scattered objects of the radio signals of this transmitter,

synchronously transform the ensemble of radio signals received by the antennas into digital signals,

direct and compressed scattered signals are formed from digital signals,

direct and scattered signals are compared and time delays, Doppler shifts and directions of arrival of scattered signals are determined, based on time delays, Doppler shifts and directions of arrival, air objects are detected and spatially localized.

The prototype method does not require a transmitter emitting radio signals on board a detectable airborne object, since it provides detection and tracking of airborne objects using natural illumination of airborne objects created at multiple frequencies by radio emissions from various transmitters. The effectiveness of the prototype method depends on a number of factors. Of which the most important are the geometric arrangement of the radiation sources, their power and the effective scattering area of the target, as well as the effectiveness of interference suppression operations, masking weak signals scattered from the targets.

The received multipath radio signal, as a rule, includes powerful direct signals and the signal components of the selected transmitter scattered from the terrestrial infrastructure. In addition, it contains signals delayed in time and shifted by the frequency of the Doppler shift, scattered by air objects, as well as signals of other uncontrolled sources operating at a frequency that coincides with the frequency of reception. For the effective detection and accurate spatial localization of a wide class of airborne objects (large, medium, small planes and unmanned aerial vehicles, helicopters, rockets, descent vehicles), high-quality separation of weak signals scattered from objects against the background of a powerful direct signal of the selected transmitter, as well as in the background signals from other unwanted sources. In most typical situations, the noise level is 40-60 dB higher than the level of scattered signals.

The disadvantages of this method are low noise immunity and, as a consequence, low detection sensitivity and insufficient accuracy of spatial localization of air objects.

The technical result of the invention is to increase the detection sensitivity and accuracy of spatial localization of a wide class of airborne objects.

Increasing the sensitivity of detection and accuracy of localization of airborne objects is achieved by:

- the use of adaptive spatial filtering operations that provide directional reception of a useful direct radio signal from the backlight transmitter while simultaneously suppressing a wide class of interference coming from other directions;

- the use of adaptive spatial filtering operations that provide directional reception of a useful scattered signal while suppressing a wide class of interference coming from other directions;

- the use of electronic compensation of coherent interference from a powerful direct radio signal of the backlight transmitter, masking weak scattered signals.

, который запоминают, из матричного цифрового сигнала

формируют сигнал пространственной корреляционной матрицы входных сигналов

, сигнал корреляционной матрицы

преобразуют в сигналы оптимальных весовых векторов для формирования прямого

и рассеянных

радиосигналов, где

- вектор наведения, определяемый азимутально-угломестным направлением приема радиосигнала, длиной волны и геометрией решетки, преобразуют матричный цифровой сигнал

в прямой

и рассеянные

цифровые сигналы для выбранных азимутально-угломестных направлений приема, которые совместно со значением азимутально-угломестного направления приема запоминают, для каждого выбранного азимутально-угломестного направления приема формируют и запоминают зависящую от временного сдвига τ комплексную взаимно корреляционную функцию (ВКФ)

между прямым цифровым сигналом

и рассеянным цифровым сигналом

, определяют максимальное значение модуля

комплексной ВКФ и фиксируют соответствующее этому максимуму значение комплексной ВКФ

, вычисляют разностный рассеянный цифровой сигнал

, формируют зависящую от временного τ и частотного F сдвигов комплексную двумерную взаимно корреляционную функцию (ДВКФ)

между разностным рассеянным цифровым сигналом

и цифровым прямым сигналом

, по модулю комплексной ДВКФ

определяют число сжатых рассеянных сигналов, а также значения задержки по времени τ_ξ и абсолютного доплеровского сдвига F_ξ каждого ξ-го сжатого рассеянного сигнала, по значениям задержки τ_ξ и абсолютного доплеровского сдвига F_ξ и азимутально-угломестного направления приема сжатых рассеянных сигналов обнаруживают и определяют пространственные координаты воздушного объекта.The technical result is achieved by the fact that in the method for detecting and spatial localization of objects, which consists in choosing a transmitter emitting a spread-spectrum radio signal, a multipath radio signal from N antennas is synchronously received, including a direct radio signal of the transmitter and scattered objects from this transmitter according to the invention synchronously transform the ensemble of radio signals received by the antennas into a matrix digital signal

stored from a matrix digital signal

form the signal of the spatial correlation matrix of input signals

signal of the correlation matrix

convert into signals of optimal weight vectors to form a direct

and scattered

radio signals where

- the guidance vector, determined by the azimuthal elevation direction of the radio signal reception, wavelength and lattice geometry, transform the matrix digital signal

in direct

and scattered

digital signals for the selected azimuthal elevation directions of reception, which together with the value of the azimuthal elevation direction of reception are stored, for each selected azimuthal elevation direction of reception form and store the time-dependent shift τ complex cross-correlation function (CCF)

between direct digital signal

and scattered digital signal

determine the maximum value of the module

complex VKF and fix the value of complex VKF corresponding to this maximum

calculate the differential scattered digital signal

form a complex two-dimensional cross-correlation function (DCF) depending on the time τ and frequency F shifts

between differential scattered digital signal

and digital direct signal

modulo integrated DCF

determine the number of compressed scattered signals, as well as the values of the time delay τ _ξ and the absolute Doppler shift F _{ξ of} each ξ-th compressed scattered signal, from the values of the delay τ _ξ and the absolute Doppler shift F _ξ and the azimuthal elevation direction of the reception of the compressed scattered signals are detected and determine the spatial coordinates of the air object.

The operation of the method is illustrated by drawings:

Figure 1 - structural diagram of a device that implements the proposed method for the detection and localization of airborne objects;

Figure 2 - operation diagram of a device that implements the proposed method.

The device (figure 1), which implements the proposed method, contains a series-connected reception and preprocessing system 1, a system for modeling and selection of radio transmitters (RPD) 2 and a computer system 3.

In turn, the reception and pre-processing system 1 includes an antenna array 1-1, a path for searching for illumination sources, including a frequency converter 1-2, ADC 1-3 and a detection device 1-4, as well as a path for receiving direct and scattered signals, including frequency converter 1-7, ADC 1-6 and adaptive spatial filtering device 1-5.

Computing system 3 includes a device for compensating coherent interference 3-1, a device for generating compressed scattered signals 3-2, a device for detecting and localizing objects 3-3.

In this case, the system 2 is connected to the input of the device 3-3, and also has an interface for connecting to the external base of the RPD. In addition, the device 3 has an output intended for connection to external systems.

Subsystem 1 is an analog-to-digital device and is designed to search and measure the synchronization parameters of backlight transmitters for objects emitting spread-spectrum radio signals, as well as for adaptive spatial filtering of useful direct and scattered radio signals.

Note that after the synchronization parameters of the direct radio signal of the selected backlight transmitter are measured or when they are a priori known, the direct radio signal of the transmitter can be generated by modeling in system 2.

. Пространственная конфигурация антенной решетки должна обеспечивать измерение азимутально-угломестного направления прихода радиосигналов и может быть произвольной пространственной конфигурации: плоской прямоугольной, плоской кольцевой или объемной, в частности конформной. Для улучшения различения сигналов не только по пространству, но и по поляризации требуется существенное различие поляризационных откликов антенн решетки, то есть антенная решетка должна быть неоднородной (гетерогенной), то есть иметь антенные элементы с отличающимися векторными диаграммами направленности.Antenna array 1-1 consists of N antennas with numbers

. The spatial configuration of the antenna array should provide the measurement of the azimuthal elevation direction of arrival of radio signals and can be of any spatial configuration: flat rectangular, flat circular or three-dimensional, in particular conformal. To improve the distinction of signals not only in space but also in polarization, a significant difference in the polarization responses of the array antennas is required, i.e. the antenna array must be heterogeneous (heterogeneous), that is, have antenna elements with different vector radiation patterns.

Frequency converters 1-2 and 1-7 are N-channels, made with a common local oscillator and with the bandwidth of each channel, which is changed in accordance with the width of the spectrum of the received radio signal. A common local oscillator provides multi-channel coherent signal reception.

The ADC 1-3 and 1-6 is also N-channel and is synchronized by the signal of one 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, as, for example, in the KB range, then frequency selective bandpass filters and amplifiers can be used instead of frequency converters 1-2 and 1-7. In addition, frequency converters 1-2 and 1-7 provide the connection of one of the antennas instead of all the antennas of the array for periodic calibration of the receiving channels using an external signal source. Calibration is possible using an internal generator, the output of which is also connected instead of all antennas for periodic calibration of channels.

The detection device 1-4 and the adaptive spatial filtering device 1-5 are computing devices.

Subsystem 2 is a computing device and is designed to identify, select, and periodically update spread spectrum radio transmitters used to illuminate a given area of airspace, as well as to generate model signals of selected transmitters.

Computing system 3 is designed to compensate for coherent interference from the direct radio signal of the selected backlight transmitter (device 3-1), the correlation formation of compressed scattered signals (device 3-2), and the detection and formation of spatial coordinates of airborne objects (device 3-3).

An enlarged diagram of the functioning of the device that implements the proposed method for the detection and localization of airborne objects is presented in figure 2. The circuit includes an RPD transmitter with a known location, emitting a spread spectrum radio signal, and also a detection-direction finding (SOP) station. The radio signal of the RPD transmitter is distributed by an earth or surface wave, which is received by the detection-direction-finding station in the form of a direct radio signal, and also by the wave irradiating a given area of the airspace, received by the detection-direction-finding station in the form of radio signals scattered from the airborne object.

In the detection-direction finding station, the search, detection and measurement of synchronization parameters of spread-spectrum radio signals are used, which are used in simulation system 2 when regenerating or modeling the reference signal for the subsequent separation of the multipath scattered signal received by the station into separate beams, i.e. when forming compressed signals scattered from air objects.

The RPD transmitter can conditionally be assigned to one of the classes: uncontrolled (uncontrolled) and controlled (managed). For example, if the RPD transmitter was not specifically created for collaboration with a detection-direction finding station and does not have communication lines with a detection-direction finding station, it can be considered as uncontrolled (uncontrolled). As uncontrolled transmitters, any systems or devices emitting in the short, meter, decimeter, and centimeter wavelength ranges can be selected radio signals with an extended spectrum and satisfying the following requirements: the spatial position should provide direct visibility between the transmitter and the detection system (if the parameters of the radio signal accurate to synchronization is a priori known, then direct visibility between the transmitter and the detection system is not required); the frequency and power of the emitted radio signal should provide effective detection of a wide class of airborne objects. An example of uncontrolled transmitters can be transmitters of communication, information and measuring radio systems for various purposes. If the RPD transmitter is specially designed to solve the problem of detecting airborne objects together with a detection-direction finding station, then this transmitter can be classified as controlled (managed). Moreover, to control the operating modes of the RPD transmitter, a communication line is provided (see Fig. 2) with a detection-direction finding station.

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 backlight transmitters coming from the device 1-4, using the modeling software, a set of transmitters emitting spread-spectrum radio signals is identified, selected and periodically updated. During the simulation, possible coverage areas, detection probabilities, and achievable localization and identification accuracy of airborne objects of various classes are estimated, which can be provided with different types of placement of transmitters relative to a detection-direction finding station. In addition, in system 2, received direct radio signals are regenerated or model transmitter signals are generated with the required synchronization parameters.

The parameters of the selected set of transmitters (number, carrier frequency, spectrum width, shape, synchronization parameters and emitted signal power, coordinates or distance and angular position relative to the SOP) are stored in subsystem 2, fed to device 3-3, and also used to configure converters 1 -2 and 1-7. In order to simplify the control circuit of the converter are not shown.

According to the signals of system 2, the frequency converter 1-2 begins to be tuned at a given rate in a given frequency range of the search for radio signals, for example in the range of 10-1000 MHz. At the same time, the search path searches and measures the synchronization parameters of the backlight transmitters emitting spread-spectrum radio signals at frequencies f _{k of the} discrete search frequency grid. In this case, the time-dependent radio signal x _kn (t) received by each antenna element with the number n of the antenna array 1-1 is filtered by frequency and transferred to a lower frequency in converter 1-2. The ensemble of radio signals x _kn (t) formed in the converter 1-2 is converted using ADC 1-3 into digital signals that enter the detection device 1-4, in which synchronization parameters are detected and measured at each frequency f _{k of the} discrete search frequency grid backlight transmitters. The operation of the detection device 1-4 is based on well-known methods of radio monitoring, for example [3].

At the same time, according to the signals of system 2, the frequency converter 1-7 is tuned to a given reception frequency f _k . The receiving path synchronously receives at a frequency f _{k a} multipath radio signal including the direct radio signal of the selected spread spectrum transmitter and the radio signals of this transmitter scattered by the objects.

The time-dependent radio signal x _n (t) received by each antenna element with the number n of the antenna array 1-1 is filtered by frequency and transferred to a lower frequency in the converter 1-7.

, The ensemble of radio signals x _n (t) formed in the transducer 1-7 is synchronously converted by an ADC 1-6 into a matrix digital signal

,

where z is the time reference number of the signal that enters the device 1-5, where it is stored.

In addition, in the device 1-5, the following actions are performed:

формируется сигнал пространственной корреляционной матрицы входных сигналов

;- from matrix digital signal

the signal of the spatial correlation matrix of the input signals is formed

;

преобразуется в сигналы оптимальных весовых векторов для формирования прямого

и рассеянных

радиосигналов, где

- вектор наведения, определяемый азимутально-угломестным направлением приема радиосигнала, длиной волны (частотой f_k) и геометрией решетки;- signal of the correlation matrix

converted into signals of optimal weight vectors to form a direct

and scattered

radio signals where

- guidance vector, determined by the azimuthal elevation direction of the radio signal reception, wavelength (frequency f _k ) and the geometry of the lattice;

в прямой

и рассеянные

цифровые сигналы для выбранных азимутально-угломестных направлений приема (α, β).- converted matrix digital signal

in direct

and scattered

digital signals for selected azimuthal elevation directions of reception (α, β).

The physically described adaptive spatial filtering operations provide simultaneous directional reception from a given direction of the useful direct signal of the selected backlight transmitter and the useful scattered signal while suppressing a wide class of interference coming from other directions. Note that the technically feasible interference suppression depth reaches 40 dB [4].

This provides a gain in sensitivity in the formation of weak scattered signals in subsequent processing steps.

и

совместно со значением азимутально-угломестного направления приема (α, β) рассеянного цифрового сигнала

поступают в устройство 3-1, где запоминаются.Digital signals

and

together with the value of the azimuthal elevation direction of reception (α, β) of the scattered digital signal

enter the device 3-1, where they are remembered.

In addition, in the device 3-1, for each selected azimuthal elevation direction of reception, the following actions are performed:

между прямым цифровым сигналом

и рассеянным цифровым сигналом

, которая запоминается;- a complex VKF dependent on the time shift τ is formed

between direct digital signal

and scattered digital signal

which is remembered;

комплексной ВКФ и фиксируется соответствующее этому максимуму значение комплексной ВКФ

;- the maximum value of the module is determined

complex VKF and the corresponding value of complex VKF is fixed

;

.- calculates the differential scattered digital signal

.

когерентной помехи

, возникающей за счет просачивания прямого радиосигнала передатчика подсвета.This operation is key in the task of increasing the sensitivity of detection and the accuracy of determining the spatial coordinates of airborne objects. Physically, this operation subtracts from the scattered digital signal

coherent interference

arising due to leakage of the direct radio signal of the backlight transmitter.

совместно с прямым цифровым сигналом

и значением азимутально-угломестного направления приема (α, β) рассеянного цифрового сигнала поступают в устройство 3-2.Differential scattered digital signal

in conjunction with a direct digital signal

and the value of the azimuthal elevation direction of reception (α, β) of the scattered digital signal is received in the device 3-2.

In the device 3-2, the value of the azimuthal elevation direction of reception (α, β) of the scattered digital signal is stored, and the following actions are also performed:

между разностным рассеянным цифровым сигналом

и цифровым прямым сигналом

.- a complex DKVF depending on the time τ and frequency F shifts is formed

between differential scattered digital signal

and digital direct signal

.

или в частотной

,

,

областях, где F_z{…} - оператор дискретного преобразования Фурье;The formation of a comprehensive DCF is carried out in a temporary

or in frequency

,

,

areas where F _z {...} is the discrete Fourier transform operator;

определяют число сжатых рассеянных сигналов, а также значения задержки по времени τ_ξ и абсолютного доплеровского сдвига F_ξ каждого ξ-го сжатого рассеянного сигнала.- modulo integrated DCF

determine the number of compressed scattered signals, as well as the time delay τ _ξ and the absolute Doppler shift F _{ξ of} each ξ-th compressed scattered signal.

The values of the time delay τ _ξ , the absolute Doppler shift F _{ξ of} each ξ-th compressed scattered signal and the value of the azimuth-elevation direction of reception (α, β) of the scattered signals are received in the device 3-3.

In the device 3-3, the detection and spatial coordinates of airborne objects are performed by the values of the delay τ _ξ , the absolute Doppler shift F _ξ and the azimuthal elevation direction (α, β) of receiving the compressed scattered signals.

The following actions are performed:

- the absolute Doppler shift F _ξ and the elevation angle β of the ξth compressed scattered signal are compared with the threshold and, when the threshold is exceeded, a decision is made to detect an air object in the azimuthal elevation direction (α, β).

The threshold is selected based on minimizing the probability of missing an object.

When determining the geographical coordinates of the detected object in the device 3-3, the following actions are performed:

- from the value of the absolute signal delay τ _ξ , the apparent distance to the object is determined D = τ _ξ s, where c is the speed of light;

- the spatial coordinates of the detected object are determined by the apparent range D and azimuth α and elevation angle β of the reception of scattered signals, for example, in accordance with [5].

In this case, an ellipsoid of equal apparent distances corresponding to the geometrical place of points in space is constructed for the “SOP - transmitter” pair, the sum of the distances to which (from the transmitter to the object and from the object to the SOP) is equal to the found value of the apparent distance D. At the intersection of the ellipsoid of equal apparent distances and the direction values (azimuth α and elevation angle β) of the scattered signals reception are determined by the geographical coordinates of the detected object.

The results of the detection and spatial localization of airborne objects are displayed to increase information content.

From the above description it follows that the device that implements the proposed method provides an increase in the detection sensitivity and accuracy of spatial localization of a wide class of air objects due to:

- the use of adaptive spatial filtering operations that provide directional reception of a useful direct radio signal from a backlight transmitter and a useful scattered signal while suppressing a wide class of interference coming from other directions;

- the use of electronic compensation of coherent interference from a powerful direct radio signal of the backlight transmitter, masking weak scattered signals.

This together increases the sensitivity of detection and the accuracy of measuring the spatial coordinates of a wide class of airborne objects.

The proposed method can be attributed to the class of methods that implement the technology of passive detection and tracking of air objects based on the natural "radio illumination" of air targets without increasing the size of the receiving antennas, radiated power and the number of transmitters used.

Thus, through the use of adaptive spatial filtering operations that provide directional reception of a useful direct radio signal from a backlight transmitter and a useful scattered radio signal while simultaneously suppressing a wide class of interference coming from other directions, as well as radio-electronic compensation of a powerful direct radio signal from a backlight transmitter, which is an additional coherent interference masking weak scattered radio signals, it is possible to solve the problem with achieving decree technical result.

Information sources

1. RU, patent 2158002, cl. G01S 13/14, 2000

2. US patent 6703968 B2, cl. G01S 13/87, 2004

3. RU, patent 2190236, cl. G01S 5/04, 2002

4. Ratynsky M.V. Adaptation and superresolution in antenna arrays. M .: Radio and communication. 2003 year

5. US Patent, 5,719,584 B2, class. G01S 003/02, 1998

Claims (1)

The method for detecting and spatial localization of airborne objects, which consists in selecting a transmitter emitting a spread spectrum radio signal, synchronously receiving a multipath radio signal from N antennas, including a direct radio signal of the transmitter and scattered objects from this transmitter, characterized in that they synchronously transform the ensemble of received radio signal antennas into a matrix digital signal

stored from a matrix digital signal

form the signal of the spatial correlation matrix of input signals

signal of the correlation matrix

convert into signals of optimal weight vectors to form a direct

and scattered

radio signals where

- the guidance vector, determined by the azimuthal elevation direction of the radio signal reception, wavelength and lattice geometry, transform the matrix digital signal

in direct

and scattered

digital signals for the selected azimuth-elevation directions of reception, which together with the value of the azimuth-elevation direction of reception remember, where z is the number of time reference signal, (·) ^H is the symbol of the Hermitian pairing, for each selected azimuth-elevation direction of formation form and remember the dependent from the time shift τ complex cross-correlation function (VKF)

between direct digital signal

and scattered digital signal

determine the maximum value of the module

complex VKF and fix the value of complex VKF corresponding to this maximum

calculate the differential scattered digital signal

form a complex two-dimensional cross-correlation function (DCF) depending on the time τ and frequency F shifts

between differential scattered digital signal

and digital direct signal

modulo integrated DCF

determine the number of compressed scattered signals, as well as the values of the time delay τ _ξ and the absolute Doppler shift F _{ξ of} each ξ-th compressed scattered signal, from the values of the delay τ _ξ and the absolute Doppler shift F _ξ and the azimuthal elevation direction of the reception of the compressed scattered signals are detected and determine the spatial coordinates of the air object.

Images