RU2440588C1 - Passive radio monitoring method of air objects - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: method is implemented by means of selection of illumination transmitters of objects radiating linear-frequency-modulated radio signals, application of operations of radio electronic compensation of incoherent interference from many parasitic transmitters and operations of radio electronic compensation of strong multi-beam forward radio signal of illumination transmitter being the additional coherent interference masking weak dissipated signals.

EFFECT: increasing detection sensitivity and accuracy of spatial localisation of wide range of air objects in conditions of multi-beam propagation of radio waves.

5 dwg

Description

The invention relates to radio engineering and can be used in airspace control systems using direct and scattered signals from airborne objects emitted by many uncontrolled and monitored 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.

The technology of passive detection and tracking of airborne objects, using natural illumination of airborne targets, created at multiple frequencies by radio emissions from transmitters for various purposes (connected, measuring, navigation, etc.) in the ranges of short, meter, decimeter and centimeter waves has not yet received sufficient distribution, despite the fact that it can significantly increase the stealth and effectiveness of the detection and spatial localization of a wide class of moving objects.

A known method of passive radio monitoring of airborne objects [1], which consists in the fact that:

receive multi-frequency radio signals in the reception band by the antenna array many times greater than the spectrum width of a single radio signal of the transmitter,

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 of passive radio monitoring of airborne objects [2], free from this drawback and selected as a prototype. According to this method:

choose transmitters that emit spread-spectrum radio signals,

synchronously receive an array of antennas at a plurality of search frequencies multi-beam radio signals, including direct radio signals of the transmitters and the radio signals scattered by the objects of these transmitters,

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

At each search frequency, digital direct and compressed scattered signals are generated from digital signals, which are used for search and spatial localization of airborne objects.

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 is the geometric arrangement of the radiation sources, their power and the effective scattering area of the target, as well as the effectiveness of noise reduction operations that mask weak signals scattered by the targets.

The received multipath radio signal, as a rule, includes powerful direct signals and the signal components of the selected transmitter reflected 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), it is necessary to select high-quality weak signals scattered by objects against the background of a powerful direct signal from the selected transmitter, as well as against the background of signals other unwanted sources. In most typical situations, the noise level is 40-60 dB higher than the level of reflected signals.

The disadvantage of this method is the low noise immunity, and, as a consequence, low detection sensitivity and insufficient accuracy of spatial localization of airborne objects in the conditions of multipath propagation of radio waves.

The prototype method of the known methods for combating interference uses only a spatial selection method based on the directional properties of the antenna and a standard correlation processing method that compresses the broadband signals and filters them against the background of interference by delay and Doppler frequency.

The technical result of the invention is to increase the detection sensitivity and accuracy of spatial localization of a wide class of airborne objects in the conditions of multipath propagation of radio waves.

Increasing the sensitivity of detection and the accuracy of localization of airborne objects in the conditions of multipath propagation of radio waves is achieved by:

- selection of backlight transmitters for objects emitting linear frequency-modulated (LFM) radio signals;

- the use of electronic compensation of incoherent interference from a variety of interfering transmitters;

- the use of electronic compensation of the powerful multi-beam direct radio signal of the backlight transmitter, which is an additional coherent interference, masking weak scattered signals.

и синхронно

принятые комплексные цифровые сигналы, где

- номер антенны, a z - номер временного отсчета сигнала, которые запоминают, формируют комплексный опорный сигнал

,The technical result is achieved by the fact that in the method of passive radio monitoring of airborne objects, which consists in selecting transmitters emitting spread-spectrum radio signals, synchronously receiving an array of antennas at a plurality of search frequencies, multi-beam radio signals, including direct radio signals of transmitters and scattered objects from these transmitters, synchronously transform the ensemble of radio signals received by the antennas into digital signals, at each search frequency from digital signals form digital direct and compressed scattered signals, which are used for searching and spatial localization of airborne objects, according to the invention, choose a transmitter emitting a continuous linear frequency-modulated radio signal with a spread spectrum, periodically unsynchronously and synchronously with the irradiating signal receive multi-beam radio signals received separately of an antenna array at a frequency f _{k of a} discrete reception frequency grid, multipath radio signals are converted to non-synchronous

and synchronously

received complex digital signals, where

- antenna number, az - time reference number of the signal that remember, form a complex reference signal

,

в модифицированные несинхронно принятые сигналы

, которые запоминают, формируют комплексный опорный сигнал

, синхронизированный с облучающим радиосигналом, преобразуют синхронно принятые отдельными антеннами решетки комплексные цифровые сигналы

в модифицированные синхронно принятые сигналы

которые запоминают, формируют комплексные коэффициенты корреляции

между модифицированными несинхронно

и синхронно

принятыми сигналами, сравнивают модуль каждого комплексного коэффициента корреляции

с порогом, при превышении порога вычисляют разностный цифровой сигнал отдельной антенны

разностные цифровые сигналы

запоминают, формируют и запоминают временной спектр

каждого разностного цифрового сигнала

, определяют значения максимумов модуля

каждого временного спектра

и сравнивают их с порогом, при превышении порога фиксируют номер m превысившего порог максимума и находят значение амплитуды, частоты и фазы соответствующей максимуму составляющей временного спектра

, а также фиксируют число М превысивших порог максимумов, генерируют М гармонических сигналов

с соответствующими найденными значениями амплитуды, частоты и фазы, вычисляют модифицированный разностный сигнал каждой антенны

, формируют и запоминают временной спектр

unsynchronized with the irradiating radio signal, convert complex digital signals unsynchronously received by individual lattice antennas

into modified unsynchronously received signals

that remember form a complex reference signal

synchronized with the irradiating radio signal, complex digital signals synchronously received by individual antenna arrays are converted

into modified synchronously received signals

which remember form complex correlation coefficients

between modified asynchronously

and synchronously

received signals, compare the module of each complex correlation coefficient

with a threshold, when the threshold is exceeded, a differential digital signal of an individual antenna is calculated

differential digital signals

remember, form and remember the time spectrum

each differential digital signal

, determine the values of the maxima of the module

each time spectrum

and compare them with the threshold, when the threshold is exceeded, fix the number m of the maximum that has exceeded the threshold and find the amplitude, frequency and phase corresponding to the maximum component of the time spectrum

, and also fix the number of M exceeded the maximum threshold, generate M harmonic signals

with the corresponding found values of the amplitude, frequency and phase, calculate the modified differential signal of each antenna

form and memorize the time spectrum

усредняют по антеннам модули

комплексных временных спектров

, определяют по максимумам усредненного модуля

число сжатых рассеянных сигналов в принятом на частоте f_k многолучевом радиосигнале и фиксируют значения частотного сдвига ω_kp каждого p-го сжатого рассеянного сигнала, идентифицируют соответствующие отдельному максимуму усредненного модуля

составляющие комплексного временного спектра

как сжатый по спектру рассеянный сигнал

, выделяют каждый сжатый сигнал

, вычисляют временную задержку τ_kp=ω_kp/2πν, где ν - скорость изменения частоты ЛЧМ радиосигнала, и абсолютный доплеровский сдвиг

, а также определяют азимутально-угломестные направления прихода каждого сжатого сигнала, выполняют обнаружение и формируют пространственные координаты воздушных объектов по значениям задержки τ_kp, абсолютного доплеровского сдвига F_kp и азимутально-угломестного направления (α, β) приема сжатых рассеянных сигналов.each modified differential signal

modules averaged over antennas

complex time spectra

, determined by the maxima of the averaged module

the number of compressed scattered signals in the multipath radio signal received at the frequency f _k and fix the frequency shift values ω _{kp of} each p-th compressed scattered signal, identify the corresponding individual maximum of the averaged module

components of the complex time spectrum

as a spectrum-scattered signal

emit every compressed signal

, calculate the time delay τ _kp = ω _kp / 2πν, where ν is the rate of change of the frequency of the LFM radio signal, and the absolute Doppler shift

, and also determine the azimuthal elevation directions of arrival of each compressed signal, perform detection and form the spatial coordinates of airborne objects by the values of delay τ _kp , absolute Doppler shift F _kp and azimuthal elevation direction (α, β) of receiving the compressed scattered signals.

Thus, due to the choice of transmitters emitting chirp radio signals, and the use of electronic compensation of a wide class of coherent and incoherent interference of objects in the conditions of multipath propagation of radio waves, it is possible to solve the problem with the achievement of the specified technical result.

The operation of the method is illustrated by drawings:

Figure 1. Structural diagram of a device that implements the proposed method of passive radio monitoring of air objects;

Figure 2. Functional diagram of a device that implements the proposed method of passive radio monitoring of air objects;

Figure 3. An example of compensation for incoherent interference from multiple interfering transmitters;

Figure 4. An example of compensation for coherent interference from a direct signal from a backlight transmitter.

Figure 5. The scheme for determining the coordinates of an air object.

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 preprocessing 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 reflected signals, including a frequency converter 1 -7, ADC 1-6 and interference compensation device 1-5.

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

In this case, the system 2 is connected to the input of the device 3-2, 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 chirp radio signals, as well as for receiving reflected radio signals and compensating for interference in received radio signals.

Note that after the synchronization parameters of the direct LFM radio signal of the transmitter are measured or when they are a priori known, the direct LFM 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.Antenna array 1-1 consists of N antennas with numbers

. The spatial configuration of the antenna array should provide measurements of the azimuthal elevation direction of arrival of the radio signals and may be of any spatial configuration.

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 interference compensation device 1-5 are computing devices.

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

Computing system 3 is intended for the formation of compressed scattered signals (device 3-1), detection and localization of objects (device 3-2).

An enlarged diagram of the functioning of the device that implements the proposed method of passive radio monitoring of airborne objects is presented in figure 2. The circuit includes an RPD transmitter with a known location emitting a spread spectrum LFM radio signal, as well as a detection-direction finding (SOP) station. The radio signals of the RPD transmitter are distributed by an earth or spatial wave, which is received by the detection-direction finding station in the form of direct radio signals, 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 by the airborne objects.

In the detection-direction finding station, search, detection and measurement of the LFM synchronization parameters of radio signals are used, which are used in simulation system 2 for modeling the reference signal for the subsequent separation of the multipath reflected signal received by the station into separate beams, i.e. when forming compressed signals reflected 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 frequency bands of the LFM radio signals with extended spectrum and satisfying the following requirements can be selected: the spatial position should provide direct visibility between the transmitter and the detection system (if the radio signal parameters are accurate before 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 LFM transmitters of connected, informational 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 the data on the detected backlight transmitters coming from the device 1-4, using the simulation software, a set of transmitters emitting continuous chirp spread 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, model continuous chirp signals of transmitters with the required synchronization parameters are generated.

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

According to the signals of system 2, the frequency converter 1-2 begins to be tuned at a given pace in a given frequency range of the search for chirp radio signals, for example, in the range of 10-25 MHz. In this case, the search path searches and measures the synchronization parameters of the backlight transmitters emitting LFM radio signals at frequencies f _{k of a} discrete grid of search frequencies. 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 functioning of the detection device 1-4 is based on widely known methods and radio monitoring devices implementing them, for example [3].

After detecting and measuring the synchronization parameters of the selected illumination transmitter emitting a continuous spread spectrum LFM, a control signal is sent from system 2 to the frequency converter 1-7.

The frequency converter 1-7 periodically asynchronously and synchronously with the irradiating signal is tuned in a given frequency range. This provides periodic non-synchronous and synchronous with the irradiating signal, the reception of multipath radio signals at multiple search frequencies.

The time-dependent radio signals received by each antenna with the number n of the array 1-1 at a frequency f _{k of a} discrete reception frequency grid are filtered by frequency and transferred to a lower frequency in converter 1-7.

и синхронно

принятые комплексные цифровые сигналы, где z - номер временного отсчета сигнала, которые поступают в устройство 1-5, где запоминаются.The ensemble of radio signals x _kn (t) formed in the converter 1-7 is converted by means of the 1-6 ADC to non-synchronous

and synchronously

received complex digital signals, where z is the number of time samples of the signal that enter the device 1-5, where they are stored.

In the device 1-5 at each frequency f _{k of a} discrete grid of reception frequencies, the following actions are performed:

, несинхронизированный с облучающим радиосигналом;- a complex reference signal is formed

unsynchronized with the irradiating radio signal;

, в модифицированные несинхронно принятые сигналы

, которые запоминаются.- complex digital signals received asynchronously received by individual antenna arrays are converted

into modified asynchronously received signals

that are remembered.

;As a result of this operation, N modified nonsynchronously received signals are generated at each frequency f _k

;

, синхронизированный с облучающим радиосигналом;- a complex reference signal is formed

synchronized with the irradiating radio signal;

в модифицированные синхронно принятые сигналы

, которые запоминаются.- complex digital signals synchronously received by individual array antennas are converted

into modified synchronously received signals

that are remembered.

;As a result of this operation, N modified synchronously received signals are generated at each frequency f _k

;

между модифицированными несинхронно

и синхронно

принятыми сигналами.- complex correlation coefficients are formed

between modified asynchronously

and synchronously

received signals.

могут быть более эффективно вычислены с применением быстрого алгоритма на основе быстрого преобразования Фурье (БПФ);Complex correlation coefficients

can be more efficiently calculated using a fast algorithm based on the fast Fourier transform (FFT);

с порогом.- compares the module of each complex correlation coefficient

with a threshold.

The threshold is selected based on minimizing false alarm;

.- when the threshold is exceeded, the differential digital signal of an individual antenna is calculated

.

Physically, this operation provides the subtraction from the signals received by each antenna of the incoherent interference signals created by interfering radio stations. An example of compensation for real incoherent interference is presented in FIG. 3. From figa and figb it follows that due to the compensation of incoherent interference, it is possible to increase the signal-to-noise ratio by more than 10 dB.

;As a result of this operation, at each frequency f _k N differential digital signals are generated

;

запоминаются;- differential digital signals

memorized;

каждого разностного цифрового сигнала

.- the time spectrum is formed and stored

each differential digital signal

.

формируется путем преобразования разностного цифрового сигнала

с использованием алгоритма БПФ;Time spectrum

formed by converting a differential digital signal

using the FFT algorithm;

каждого временного спектра

и сравниваются их с порогом;- the values of the maxima of the module are determined

each time spectrum

and compare them with the threshold;

, a также фиксируется число М превысивших порог максимумов;- when the threshold is exceeded, the number m of the maximum threshold is fixed and the value of the amplitude, frequency and phase corresponding to the maximum of the time spectrum component is found

, a also fixes the number of M exceeded the maximum threshold;

с соответствующими найденным значениями амплитуды, частоты и фазы;- M harmonic signals are generated

with the corresponding found values of the amplitude, frequency and phase;

.- a modified differential signal of each antenna is calculated

.

This operation is key in the task of increasing the detection sensitivity and accuracy of determining the spatial coordinates of airborne objects in the conditions of multipath propagation of radio waves. Physically, this operation provides the subtraction from the signals received by each antenna of the multipath coherent interference signal arising from the leakage of the multipath direct radio signal of the backlight transmitter.

An example of the compensation of real coherent interference from the backlight transmitter is presented in Fig.4. From figure 4 it follows that due to compensation, it is possible to reduce the level of real coherent interference by 30-40 dB.

, которые поступают в вычислительную систему 3, где запоминаются в устройстве 3-1.As a result of this operation, N modified differential digital signals are generated at each frequency f _k

that enter the computing system 3, where they are stored in the device 3-1.

In addition, in the device 3-1, at each receiving frequency f _k , the following actions are performed:

каждого модифицированного разностного сигнала

;- the time spectrum is formed and stored

each modified differential signal

;

комплексных временных спектров

,- modules are averaged over antennas

complex time spectra

,

число сжатых рассеянных сигналов в принятом на частоте f_k многолучевом радиосигнале, и фиксируются значения частотного сдвига ω_kp каждого p-го сжатого рассеянного сигнала;- determined by the maxima of the averaged module

the number of compressed scattered signals in the multipath radio signal received at a frequency f _k , and the frequency shift ω _{kp of} each pth compressed scattered signal is fixed;

составляющие комплексного временного спектра

как сжатый по спектру рассеянный сигнал

;- identified corresponding to the individual maximum averaged module

components of the complex time spectrum

as a spectrum-scattered signal

;

;- each compressed signal is highlighted

;

, где

- номер антенны, а также определяются азимутально-угломестные направления прихода каждого сжатого сигнала.- the time delay τ _kp = ω _kp / 2πν is calculated, where ν is the rate of change of the LFM frequency of the radio signal, and the absolute Doppler shift

where

- the antenna number, and the azimuthal elevation directions of arrival of each compressed signal are also determined.

синтезируется комплексный двумерный угловой спектр, по максимумам модуля которого определяется азимутально-угломестное направление прихода (α_kp, β_kp) p-го сжатого сигнала.When determining the device 3-1 azimuthal elevation directions of arrival of compressed signals, for example, using the method [3], according to the selected values of each compressed signal

a complex two-dimensional angular spectrum is synthesized, the maximum modulus of which determines the azimuthal elevation direction of arrival (α _kp , β _kp ) of the pth compressed signal.

The found values of the delay τ _kp and the absolute Doppler shift F _kp , as well as the azimuthal elevation direction (α, β) of receiving the compressed signals are sent to the device 3-2, where they are stored.

In addition, in device 3-2, a detection is performed at each receiving frequency f _k and spatial coordinates of airborne objects are formed from the values of delay τ _kp , absolute Doppler shift F _kp and azimuth-elevation direction (α, β) of receiving the compressed scattered signals.

The following actions are performed:

- the absolute Doppler shift F _kp and the elevation angle β of the pth scattered compressed 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 a detected object, device 3-2 performs the following actions:

- the absolute distance of the signal τ _kp determines the apparent distance to the object D = τ _kp c, where c is the speed of light;

- the spatial coordinates of the detected object are determined by the apparent range D and the azimuth α and elevation angle β of receiving the compressed scattered signals, for example, in accordance with [4].

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.

Figure 5 shows a diagram for determining the coordinates of an airborne object when using one transmitter.

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 the accuracy of spatial localization of a wide class of air objects by one detection-direction finding station under conditions of a priori uncertainty due to:

- the choice of transmitters emitting chirp radio signals.

LFM radio signals can have a long duration and, therefore, a large energy, which increases the ultimate sensitivity (range) of detection and spatial localization of airborne objects. In addition, LFM compression of radio signals provides high resolution in range and speed. Moreover, the chirp radio signal provides the ability to obtain information about airborne objects at any frequency due to the continuity of the irradiating signal in frequency and time, which eliminates the spatial frequency sectors in which sensitivity may be lost when a wide class of airborne objects are detected, and reduces the number of transmitters, used in detection;

- the use of electronic compensation for incoherent interference created by a variety of interfering radio transmitters;

- the use of electronic compensation of coherent interference created by powerful multi-beam direct LFM radio signal of the selected backlight transmitter.

This together increases the quality of detection and the accuracy of measuring the spatial coordinates 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, due to the choice of transmitters emitting chirp radio signals, and the use of electronic compensation of a wide class of coherent and incoherent interference, an increase in the detection sensitivity and accuracy of spatial localization of a wide class of airborne objects under conditions of multipath propagation of radio waves is achieved.

Information sources

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

2. US patent 7012552 B2, class. G08B 21/00, 2006

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

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

Claims (1)

The method of passive radio monitoring of airborne objects, which consists in the use of direct and scattered by airborne objects signals emitted by many uncontrolled and monitored transmitters of electronic systems for various purposes, characterized in that a transmitter emitting a continuous linear frequency-modulated (LFM) is selected from a plurality of radiating transmitters ) a spread-spectrum radio signal periodically unsynchronously and synchronously with the irradiating signal is received at a plurality of search frequencies goluchevye signals received separate antenna array at frequency f _k the discrete frequency grid receiving multipath radio signals are converted into asynchronous

and synchronously

received complex digital signals, where

- antenna number, az - time reference number of the signal that remember, form a complex reference signal

, unsynchronized with the irradiating radio signal, convert complex digital signals unsynchronously received by individual lattice antennas

into modified unsynchronously received signals

that remember form a complex reference signal

synchronized with the irradiating radio signal, complex digital signals synchronously received by individual antenna arrays are converted

into modified synchronously received signals

that remember form complex correlation coefficients

between modified asynchronously

and synchronously

received signals, compare the module of each complex correlation coefficient

with a threshold, when the threshold is exceeded, a differential digital signal of an individual antenna is calculated

differential digital signals

remember, form and remember the time spectrum

each differential digital signal

, determine the values of the maxima of the module

each time spectrum

and compare them with the threshold, when the threshold is exceeded, fix the number m of the maximum that has exceeded the threshold and find the amplitude, frequency and phase corresponding to the maximum component of the time spectrum

, and also fix the number of M exceeded the maximum threshold, generate M harmonic signals

with the corresponding found values of the amplitude, frequency and phase, calculate the modified difference signal of each antenna

form and memorize the time spectrum

each modified differential signal

, average the modules over the antennas

complex time spectra

, determined by the maxima of the averaged module

the number of compressed scattered signals in the multipath radio signal received at the frequency f _k and fix the frequency shift values ω _{kp of} each p-th compressed scattered signal, identify the corresponding individual maximum of the averaged module

components of the complex time spectrum

as a spectrum-scattered signal

emit every compressed signal

, calculate the time delay τ _kp = ω _kp / 2πν, where ν is the rate of change of the frequency of the LFM radio signal, and the absolute Doppler shift

, and also determine the azimuthal elevation directions of arrival of each compressed signal, perform detection and form the spatial coordinates of airborne objects by the values of delay τ _kp , absolute Doppler shift F _kp and azimuthal elevation direction (α, β) of receiving the compressed scattered signals.

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