RU2439603C1 - Method of detecting and recognising source of electromagnetic radiation - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: method involves receiving in low-frequency (LF) and high-frequency (HF) ranges the magnetic field component on several unit vectors, determining, for the received signal, the amplitude, carrier frequency, the type and parameters of modulation, presence of harmonic components of the carrier frequency, the time for the beginning and end of existence of the signal, the type of the time function and bearing to its source; the time for the beginning and end of existence of signals in the HF range for which two or more harmonic components of the carrier frequency have been detected is compared with the time for the beginning and end of existence of signals in the LF range; those pairs of signals from the radiation source for which the difference between the arrival time is constant, the type of modulation of the HF signal and the type of the time function of the LF signal are identical and the direction of bearing to signals in the LF and HF ranges coincide are selected. If these conditions are met, the signal is identified as belonging to the recognised source of electromagnetic radiation. ^ EFFECT: high reliability of detecting and identifying a source of electromagnetic radiation by using information of ionospheric reflection of a signal in low- and high-frequency ranges. ^ 8 dwg

Description

The invention relates to radio engineering and can be used to determine the location of a priori unknown sources of radio emission from the radiations of their transmitters, to detect ionospheric channels providing ultra-long-range radar, analyze the effects of powerful electromagnetic radiation on the ionosphere in order to assess the negative impact on the ionosphere and biological objects.

The problems of determining with high accuracy the location and recognition of sources of electromagnetic radiation (transmitters, "heating stands", radio heating complexes) are associated with the improvement of communication systems and radio engineering, using complex signals with a low spectral power density. Due to the energy secrecy of complex signals, it is necessary to minimize the number of receiving positions (US patent 5719584, IPC G01S 3/02, 1998), and to preserve the ambiguity of the results, an increase in the number of receiving positions is required (FR, patent 2688892, IPC G01S 3/40 , 1989).

A known method for multi-position location of decameter wave transmitters according to patent RU No. 2285935, IPC G01S 5/04, 2005, in which to improve the accuracy of determining the location of transmitters from a wide class of signals, including complex signals with a low spectral power density, eliminate anomalous measurement errors based on a combination of one-position and multi-position methods for determining coordinates, this takes into account additional information about the laws of ionospheric propagation of signals Occupancy.

A known method of recognizing signals of communication systems according to patent RU No. 2340910, IPC G01R 23/16, 2008, in which adaptive multi-stage settings of the reception system and digital signal processing are performed: Fourier transform, obtaining signal spectra and measuring its frequency parameters (average frequency spectrum, the width of its frequency band).

Since the proposed technical solution is based on the effect of electromagnetic radiation on the ionosphere, a single-point range measurement of electromagnetic radiation sources according to patent RU No. 2118836, IPC G01S 5/02, 1998, in which the range is determined by the delay time of ionospheric reflection relative to the signal of the earth wave, the height of the reflecting layer of the ionosphere and take into account the characteristics of the signal, for which they determine the reference frequency of electromagnetic radiation corresponding to the maximum amplitude signal spectrum.

Almost all of the above methods for detecting and determining the source of electromagnetic radiation in one way or another solve the problem of increasing the accuracy of determining the location (coordinates, range, direction of radiation) of sources, which is the most important characteristic of such measurements, and its improvement is an urgent task.

The technical task of the proposed method is to increase the reliability of detection and recognition (identification) of the source of electromagnetic radiation (heating stand) by using information of the ionospheric reflection of the signal of the heating stand in the low-frequency (LF) and high-frequency (HF) ranges.

To achieve a technical result, a method for on-line detection and recognition of an electromagnetic radiation source is proposed, which includes receiving in the high-frequency range the magnetic component of the electromagnetic field by several orts, determining the amplitude and carrier frequency corresponding to the maximum amplitude spectrum of the signal to determine the bearing (direction of arrival of electromagnetic radiation) to the radiation source when the set detection threshold is exceeded, in which it is additionally determined t in the high-frequency range, the type and modulation parameters (index, deviation, deviation time, etc.) of the received signal, the presence of harmonic components of the carrier frequency, the start and end time of the existence of the signal, additionally receive the signal in the low-frequency range, determine the amplitude, frequency, the form of the time function and the bearing on its source, compare the start and end time of the existence of signals in the high frequency range, in which two or more harmonic components of the carrier frequency are detected, with time the beginning and end of the existence of signals in the low-frequency range, the type of modulation of the high-frequency range signals and the type of time function of the low-frequency range signals, and those pairs of radiation source signals are distinguished for which the difference in the arrival time of the signals is constant, the type of modulation of the high-frequency signal and the type of temporal function of the low-frequency signal are the same , and the directions of the bearings to the signals in the low-frequency and high-frequency ranges coincide. When these conditions are met, the signal is identified as belonging to a recognizable source of electromagnetic radiation (heating stand).

Figure 1 shows a block diagram explaining the principle of construction of a signal recognition algorithm of the proposed method; figure 2 is an example of a spectral distribution in the HF frequency range with the exception of constantly operating radio facilities (frequencies of 2.8 and 6.5 MHz); figure 3 - exclusion of signals not exceeding the set detection threshold; figure 4 is a panoramic overview of the signal with a frequency of 4.3 MHz, exceeding the detection threshold for determining the modulation frequency (the marker in the drawing corresponds to a modulation frequency of 6.8-7.0 kHz); figure 5 - determination of the law of modulation of the signal with a frequency of 4.3 MHz (harmonic); figure 6 - search in the low frequency range of signals with frequencies equal to the modulation frequencies of the signals in the high frequency range (a frequency of 7 kHz is present and coincides with the modulation frequency of the signal 4.3 MHz in the high frequency range); Fig.7 is a view of a time diagram of a signal of the low frequency range (comparison of the signal’s lifetime, the coincidence of the view with the law of modulation of the signal with a frequency of 4.3 MHz indicates that the 4.3 MHz signal belongs to the signal of the heating stand); on Fig - structural diagram of a device for implementing the method.

The implementation of the method is based on the determination and comparison of key parameters of high-frequency (in the range from 2 to 12 MHz) and low-frequency (in the range from 0.8 Hz to 100 kHz) electromagnetic radiation. Parameters are determined using digital signal processing performed on data arrays obtained from three receiving channels (the magnetic component of the X / Y / Z unit of the geomagnetic field) of each magnetic field transducer.

In particular, algorithms for multipoint fast Fourier transform, convolution calculations, and statistical processing are used. The determination of the bearing of the sources of electromagnetic radiation is carried out by pairwise mutual correlation signal processing at the outputs of the receiving-amplifying paths of the device for implementing the method.

The operationally proposed method is as follows:

- the signal detection threshold is set (signal-to-noise ratio is about 13 dB);

- a 5 kHz analysis band is set for scanning the frequency range;

- an analysis of the radio-electronic situation is carried out with the formation of a data bank of constantly operating radio equipment (radio stations, beacons, radar, etc.) according to the criterion for exceeding the average harmonic level of the established detection threshold (initial analysis is given 1 day);

- excluded from the analysis of frequencies included in the data bank (figure 2);

- a 200 Hz analysis band is set for scanning the frequency range and searching for signals from IRI radio sources (heating stands);

- a signal search and analysis is performed according to the criterion for exceeding the average harmonic level of the set detection threshold (Fig. 3);

- their parameters are determined (carrier frequency, type and frequency of modulation, the presence of the 2nd and 3rd harmonics of the carrier frequency (Figs. 4-5));

- identification of the radiation source: an unambiguous criterion for belonging to the heating stand is the presence of harmonics of the carrier frequency (two or more), as this confirms the nonlinearity of the source of electromagnetic radiation (inhomogeneity of the reflecting medium in the ionosphere);

- the bearing is determined to the RF source when the signal of the radiation source is 10 dB higher than the set detection threshold;

- search for modulation frequencies in the low frequency range (Fig.6);

- determination of signal parameters in the low-frequency range;

- determination of the bearing to the source of low-frequency radiation when the signal of the radiation source is exceeded by 10 dB of the established detection threshold;

- comparison of these parameters of HF and LF emissions and determining the possible purpose of the heating stand during this period with these modes (Fig.7).

Data transmission to the device output: center frequency, type of modulation, bearing, time.

The device for implementing this method (Fig. 8) consists of two parts: low-frequency and high-frequency.

The low-frequency part includes a magnetic field converter 1 (three rod antennas) for measuring in the subband of 0.8-40 Hz, a magnetic field converter 2 (three rod antennas) for measuring in the subband of 60-10000 Hz, a magnetic isotropic loop antenna 3 for measuring in the subband 10-100 kHz. Each of the three channels of converters 1-3 is connected to the processing unit 4, the inputs and outputs of which are connected via a fiber optic communication line (FOCL) to the interface unit 5, the inputs and outputs of which are connected via a USB port to a personal computer 6.

The synchronization of the blocks is carried out through sources of highly stable clock frequencies 7 and 11, which are used as a GPS receiver.

The high-frequency part of the complex includes a magnetic isotropic antenna 8 for measurement in the range of 2-12 MHz, from three channels of which the signals are sent to the processing unit 9, the inputs and outputs of which are connected to a personal computer 10 via a USB port.

The network hub (HUB) 12 combines both parts of the complex, the inputs and outputs of which via an Ethernet port are connected respectively to the inputs and outputs of personal computers (PCs) 6 and 10 and are the output of the device.

Reception of signals is carried out by magnetic converters (antennas) 1-3, 8, each of which has three independent identical channels for receiving the magnetic component of the electromagnetic field along the X / Y / Z orts located in one receiving system. The low-frequency signals are fed to the pre-amplifier module of processing unit 4, where a broadband amplifier with a programmable gain and high common-mode rejection, as well as an low-pass filter, bring the signals to the required level. Next, the signals in the processing unit 4 are fed to an analog-to-digital converter (ADC) and to the central signal preprocessing processor. The multiplexed signal is transmitted via the data bus to the controller of the optical transceiver and through the fiber-optic communication line to the interface unit 5.

For the coordinate-time reference of signals, a GPS receiver is used with the ability to transmit a precise second-time signal (latitude, longitude, time, date) and solving the direction finding problem to a source that satisfies the registration conditions. Reception, conversion of the optical signal into an electrical signal, its demultiplexing and transmission to the USB port controller is performed in the interface unit 5 (low frequency range) and in block 9 (high frequency range). Transmission and reception of PC data 6 and 10 between the HF and LF parts of the device via Ethernet communication channels.

The proposed set of features makes it possible to use information on the patterns and characteristics of ionospheric signal propagation in the high-frequency and low-frequency ranges of radiation when detecting and determining the radiation source, when the ionosphere acts as a detector, the mechanism of action of which has not yet been studied. As a result of using this method, the number of possible signals to be analyzed is reduced, increasing the reliability of identification of the radiation source.

Claims (1)

A method for detecting and recognizing an electromagnetic radiation source, including receiving in the high-frequency range the magnetic component of the electromagnetic field in several unit vectors, determining the amplitude and carrier frequency corresponding to the maximum amplitude spectrum of the signal to determine the bearing to the radiation source when the set detection threshold is exceeded, characterized in that it is determined in high-frequency range type and modulation parameters of the received signal, the presence of harmonic components of the carrier part you, the time of the beginning and end of the existence of the signal, additionally receive the signal in the low-frequency range, determine the amplitude, frequency, type of the time function and the bearing to its source, compare the time of beginning and end of the existence of signals in the high-frequency range, in which two or more harmonic components are detected carrier frequency, with the start and end time of the existence of signals in the low-frequency range, the type of modulation of the high-frequency range signals and the type of time function of the low-frequency signals -frequency band and emit signals those pairs of radiation sources, in which the signal arrival time difference is constant, the form of high-frequency modulation signal and a baseband signal form the temporary functions are identical, and directions of bearings to signals in the low and high frequency ranges are identical.

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