RU2745658C2 - Method and device for detecting radio-controlled explosive devices usind unmanned aerial vehicle - Google Patents

Abstract

FIELD: radar.

SUBSTANCE: present invention relates to radar, in particular to near-range radar systems (RS) in which non-linear radar (NR) objects containing active radio elements are searched. The method for detecting RED using an unmanned aerial vehicle (UAV) consists in generating and emitting two harmonic signals S1 and S2 in the direction of the RED with frequencies f1 and f2 respectively, and in receiving a reflected signal, synchronous detection of the received signal by means of a reference oscillation S0 of frequency f0 and decision to detect a non-linear-scattering object by comparing the output of the synchronous detector with the threshold. Detection of RED is carried out in two modes: «search» and «listening». In the «search» mode, the search object is irradiated by the NLR, and the response signal is recorded by the operator with the help of the headphones to the ear. In the mode of «listening» NLR emits in the direction of the object of search a modulated signal, the temporal structure of which in the transmitter is formed such that when detecting the useful signal-response the operator hears a characteristic clippy acoustic signal. Furthermore, a shift between the frequency of the received signal and the frequency of the heterodyne of the order of 1 3 kHz is ensured in the receiving part of the NLR, and the response signal acquires an amplitude phase modulation. The response signal is demodulated by means of a linear synchronous detector, preserving the characteristics of the modulated response signal and displaying the amplitude values of the signals on the light signal indicator at a logarithmic scale, by which the operator identifies the search object. The inventive device for carrying out said method consists of hinged UAV equipment consisting of a NLR, a video camera, a GPS module, a data transmission channel and an autonomous information control and display panel. The NLR consists of a transmitter, an antenna system, a duplex filter, a receiver in the second harmonic tract, a third harmonic tract, a reference generator, a switch, a demodulator; a digital module in the two-channel ADC, a processor, a receiver controller, a transmitter controller, a control radio. The NLR uses an antenna system of circular polarization containing three microband antennas for each operating frequency band.

EFFECT: increased range of detection of radar explosive devices (RED).

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Description

The present invention relates to the field of radar, in particular to short-range radar systems (radars), in which nonlinear radars (HPL) search for objects containing active radioelements. Moreover, the reflection from such a search object occurs at the higher harmonics of the probing signal arising during nonlinear transformation in the active elements of the search object.

The relevance of the development of new radar methods and devices is due to the growing threat of "explosive" terrorism throughout the world, as well as the ongoing military conflicts, during which radio-controlled explosive devices (RWD) are becoming more widespread. At the same time, the range of action of the radar determines the distance of the search operator (personnel) from the detected RVD, sufficient for life safety, in contrast to the widely used short-range means of detecting explosive devices - special probes or active induction metal detectors.

It is known that radar devices operating in certain location modes are used to detect RVD hidden in the masking environment [1]. The principle of their operation is based on the irradiation of the examined objects with short radio frequency pulses and the reception of response signals (re-emitted signals) at the frequencies of the second and third harmonics of the probe radiation.

The response signals at the frequencies of the second and third harmonics of the probing radiation appear as a result of the spectral transformation of the probing signal on elements with a nonlinear current-voltage characteristic. This characteristic is possessed by semiconductor elements that are part of electronic devices.

When radioelectronic devices are irradiated, the even harmonic components of the probe radiation (2nd harmonic), as a rule, prevail in the spectrum of the re-emitted signal; on the contrary, when the contacts of metal objects are irradiated, as a rule, odd harmonics (3rd harmonic) prevail in the spectrum of the re-emitted signal.

By registering with the help of the receiver signals at frequencies corresponding to the second and third harmonics, the operator distinguishes objects containing electronic circuits with semiconductor elements from objects containing metal contacts by the ratio of their levels.

The known method of nonlinear location [2], which consists in the generation of 2 harmonic signals S1 and S2 with frequencies ƒ1 and 2, respectively, the radiation in the direction of the RVU of 2 probing signals (ES), the reception of the reflected signal, synchronous detection of the received signal using the reference fluctuations S0 of frequency f0 and making a decision on the detection of a nonlinearly scattering object by comparing in the threshold circuit the power of the output signal of the synchronous detector with the threshold.

This method is implemented in a well-known nonlinear radar - a portable detector of nonlinear transitions "NR-900EK", taken as a prototype [2]. A monoharmonic sounding signal generated by the transmitter is applied to a directional transmitting antenna and is emitted in the direction of the object to be examined. On nonlinear (semiconductor) elements of the object of examination, the probing signal is converted into a polyharmonic one ("enriched" with harmonics) and re-emitted.

The re-emitted signal is received by the receiving antenna and fed to the inputs of the receivers, which select the signals of the 2nd and 3rd harmonics of the sounding frequency. The selected signals from the receivers are sent to the processing unit for further processing. After processing the received signals in the processing unit, their levels are displayed on the LED indicators of the control and display panel (SDI PUI). The decision about the type of the object is made according to the ratio of the levels of the response signals at the frequencies of the 2nd and 3rd harmonics of the sounding frequency.

The disadvantage of the prototype is the limited detection distance of the RVU and, as a consequence, the impossibility of using this NRL in conjunction with an unmanned aerial vehicle.

The technical result of the proposed invention is to increase the detection range of the RVD.

The essence of the proposed method is as follows:

The known prototype includes the "Sound" option (or "Sound" - sound, English), which for the new NRL is designed to increase the detection range of RVD due to the psychophysiological phenomenon associated with the ability of the human operator to detect the smallest (10 or less times) changes in the "structure" or signature of the audible noise. The temporal structure of the transmitter pulse probing signal (TSP) is formed so that when a useful response signal is detected, the operator hears a characteristic clipped acoustic signal.

In the structural diagram of the receiving part of the NRL, a shift is provided between the frequency of the received signal and the frequency of the local oscillator of the order of 1 ... 3 kHz. The gain in NRL sensitivity is due to the following provisions:

-130 dBm: the level of thermal (intrinsic) noise of the receiver (Rx) of the used NRL or the sensitivity level of the Rx;

-120 dBm: threshold +10 dBm in relation to the intrinsic noise of the PRM, - the level of lighting of the first LED of the LED PUI NRL;

-110 dBm: threshold +20 dBm in relation to the intrinsic noise of the PRM, the level of "ignition" of the 4th LED LED PUI NRL - the typical detection threshold of the RVU;

-135 dBm - the level below inherent noise, where the operator by ear already detects the clipped tone signal against the background of "stationary" noise.

Thus, the introduction of the "Sound" option allows increasing the "virtual" NRL sensitivity by approximately 25 dBm. According to preliminary estimates, this should lead to an increase in the detection range of RVD by at least 50%.

NRL has two modes of operation - "Search" and "Listening".

A feature of the NRL operation in the "Search" mode is the recording of the response signal at the frequencies of the 2nd and 3rd harmonics of the ES by ear. This method makes it possible to use the feature of human hearing to distinguish a signal, the level of which is significantly lower than the noise level. The operator, upon detecting a search object, hears tones with a duration of 50 ms with a period of 250 ms, the amplitude of which (sound volume in the headphones) is proportional to the level of the useful signal at the receiver input. The change in the frequency of tone bursts arising from the movement of the NRL relative to the search object (Doppler effect) is perceived by the operator as an alarm signal and does not lead to missing the target.

The Listening mode is mainly used for post-tracking. When moving the object of the search, the work of its moving parts, and functioning electronic circuits, the signal-response from it acquires amplitude-phase modulation. Demodulation of such a response signal with a linear synchronous detector preserves the characteristic features of the baseband signal. A trained operator using these features can identify the detected object, for example, a clock mechanism, a cell phone, etc. In the "Listening" mode, the NLR emits an unmodulated ES.

The claimed method is implemented in the device of a mobile complex based on an unmanned aerial vehicle (UAV) and consists of attachments consisting of: NRL, video camera, GPS module, data transmission channel and an autonomous control panel and information display.

The block diagram of the NRL for the UAV is shown in Fig. one:

The receiver (PRM) of the NLR consists of the following main functional units: receiving antenna system 1; duplex filter 2; second harmonic path 3, 4, 5, 6, 7; third harmonic path 0, 11, 12, 13, 14; reference generator 8; switch 9; demodulator 15, 16, 17, 18, 19, 20.

The duplex filter provides suppression of the ES and separation of the response signal into the frequencies of its second and third harmonics. The paths of the 2nd and 3rd harmonics are practically identical and have no peculiarities.

At the output of the paths, the IF signals S2pch (t) and S3pch (t) are generated, corresponding to the second and third harmonics, which are fed to the switch 9. When the RVU is detected, as a rule, the 2nd harmonic of the ES is recorded, therefore, by default, when the power is turned on, to the output of the 2nd harmonic path is connected to the demodulator. If necessary, the operator can change the connection using the radio control panel.

The block diagram of the digital part of the NRL on the UAV (power circuits are not shown) is shown in Fig. 2, where:

28 - two-channel analog-to-digital converter (ADC); 29 - processor; 30 - receiver controller; 31 - transmitter controller; 32 - radio control panel.

Also, the signals of the intermediate frequency S2pch (t) and S3pch (t) are fed to the input of the two-channel ADC 28 of the digital part of the NRL for the UAV. In the processor 29, they are demodulated and the values of the signal amplitudes are displayed on the light-signal indicator in a logarithmic scale. The amplitude S2pch (t) corresponds to the amplitude of the 2nd harmonic of the SW, S3pch (t) - the 3rd harmonic of the SW. IF signal demodulation is carried out in a quadrature synchronous detector (QSD) 17.

To explain the demodulation process, consider the frequency plan of the NRL receiver for a UAV. In the "Search" mode in the ZS shaper (26) from the signal of the reference generator 8, a pulse-modulated ZS with the frequency Fzs is synthesized:

where F_1 = 848 MHz.

The frequency value ΔF is selected in the range of kHz units. Frequencies of the response signal for the 2nd and 3rd harmonics of the ES:

After the first frequency conversion at the output of converters 5 and 12, IF signals with a frequency of F_FC2 = 2⋅ΔF (2nd harmonic path) and F_FC3 = 3⋅ΔF (3rd harmonic path) are generated.

The demodulation process is shown in FIG. 3. For the selected signal (2nd or 3rd harmonic of the ES), the local oscillator of the synchronous detector 16, which is a direct digital synthesis (DDS) generator, generates reference signals:

when demodulating the 2nd harmonics of the ES:

when demodulating the 3rd harmonic of the ES:

Thus, the useful signal at the output of the KSD 17 is a sinusoid with the frequency: 2Δf when receiving the 2nd harmonic of the SW, 3Δf when receiving the 3rd harmonic of the SW, modulated according to the law of the change in the SW. Typical value Δf is chosen to be 500 Hz.

In the "Listening" mode, the frequency of the ES is the same as in the "Search" mode. The differences are as follows:

- ЗС is not modulated (NG mode);

- value Δf = 0.

. На выходе синхронного детектора формируется сигнал, обусловленный модуляцией сигнала отклика от цели. Квадратурные составляющие I и Q с выхода КСД поступают на сумматор 18, выходной сигнал, которого фильтруется и усиливается в устройстве 19 и поступает на вход ПРД радиоканала звука 20.In this case, the identities hold

... At the output of the synchronous detector, a signal is generated due to the modulation of the target response signal. The quadrature components I and Q from the output of the KSD are fed to the adder 18, the output signal of which is filtered and amplified in the device 19 and is fed to the input of the PRD of the sound radio channel 20.

The NLR transmitter for UAVs consists of the following main units: the ZS shaper (26); controlled transmitter attenuator (25); preliminary and output power amplifier (24), (23); LPF (22); transmitting antenna (21). The SZ generator consists of a signal synthesizer with a frequency of F_1 = 848 MHz, a direct digital synthesis (DDS) generator of a signal with a frequency of ΔF and a quadrature modulator, which forms an SZ with a frequency of F_zs = F_1 + ΔF. The controllable attenuator (25) provides the ability to adjust the power of the probing signal. There are 3 values - maximum, average and minimum output power (step of change is 6 dB).

Amplifiers (24) and (23) provide a predetermined transmitter output power. Modulation of the ES in the "Search" mode is carried out by switching the power supply circuits of the amplifiers. A step-up voltage converter (27) is used to power the output power amplifier. LPF (22) provides spectral "purity" of the ZP.

A feature of the proposed mobile complex is the developed antenna system of circular polarization of two types.

First type. Three microstrip antennas (for each operating frequency range), located coaxially. Below is a lower frequency emitter, above it are the emitters of the second and third harmonics, respectively. A model of this type of antenna with overall dimensions is shown in Fig. four.

FIG. 5 shows the directional diagram (DP) of the NRL antenna gain (in dB) in the azimuthal plane for 3 frequency ranges (F1, F2, F3), the main beam of the gain directivity pattern in the azimuthal plane for 3 frequency ranges of the prototype is shown antennas. It follows from it that the gain of a microstrip antenna is lower than the gain of an array of 2 linear folded dipoles by 1 dB in transmission and 1 ... 2 dB in reception.

As part of a full-scale experiment, various antennas in an anechoic chamber were alternately connected to one NRL transceiver device using probes of the 2nd and 3rd harmonics. The results are shown in the table. Within the framework of the problem being solved, the difference is at least 3 dB, which is illustrated in the table.

The advantage of this type of antenna over a linear dipole antenna is that the product does not need to be rotated during operation, since waves with any polarization are emitted and received. Another advantage is the use of 2 separate filters in front of the RX, and not a diplexer, as is the case with a linear type of antenna. Structurally, the assembly of this type of antenna is simpler than that of a linear dipole antenna, and the height is almost three times lower.

Second type. In the process of developing a new type of NRL, a variant (type) of an antenna with circular polarization, but with a high gain of the transmitting antenna, was proposed. The design of this antenna consists of two mutually orthogonal pairs of folded dipoles. This antenna is shown in FIG. 6.

This mutual arrangement ensures the presence of orthogonal modes, and with quadrature addition of signals from these antennas, an antenna with circular polarization and with a gain not less than that of a linear type of radiator can be obtained. The radiation pattern (gain) of this antenna is shown in FIG. 7.

The addition of 2 arranged orthogonally folded dipoles does not add amplification to the linear type of the emitter, however, it is possible to obtain circular polarization with an ellipticity coefficient, as in a microstrip antenna.

The given design characteristics of the proposed invention increase the visibility and the detection range of the missile launcher, which makes it possible to effectively search for the missile launcher at a sufficient safe distance using UAVs.

Literature:

1. Dikarev V.I. Methods and means of detecting objects in covering environments / V.I. Dikarev, V.A. Zarenkov, D.V. Zarenkov. - SPb .: Nauka i Tekhnika, 2004 .-- 280 p.

2. Portable detector of nonlinear transitions "NR-900EK" / Operation manual. UTDN 268 165 003 RE. - M .: ZAO "Group of protection - YUTTA".

Claims (3)

1. A method for detecting radio-controlled explosive devices (RED) using an unmanned aerial vehicle, which consists in generating 2-harmonic signals S1 and S2 with frequencies f1 and f2, respectively, radiation in the direction of the RWU of 2 probing signals, receiving a reflected signal, synchronous detection of the received signal using the reference oscillation S0 of the frequency f0 and making a decision on the detection of a nonlinear scattering object by comparing in the threshold circuit the power of the output signal of the synchronous detector with a threshold, characterized in that the detection of the RVD is carried out in two modes of "search" and "listening", in in the "search" mode, the object of study is irradiated by a nonlinear radar (NRL) with a probing signal, and the signal-response is recorded by the operator using headphones by ear, while using the feature of human hearing to distinguish a signal whose level is significantly lower than the noise level, and which is perceived by the operator as tonal prompts l, the amplitude of which is proportional to the level of the useful signal at the input of the receiver, and the frequency of the tone sends depends on the movement of the NRL relative to the search object; in the "listening" mode, the NRL emits a modulated signal towards the search object, the temporal structure of which in the transmitter (TX) is formed so that when a useful response signal is detected, the operator hears a characteristic clipped acoustic signal, while in the receiving part of the NRL a shift between the frequency of the received signal and frequency of the local oscillator of the order of 1 ... 3 kHz, and the signal-response acquires amplitude-phase modulation due to the modulation of the signal from the target of the search, using a linear synchronous detector, demodulation of such a signal-response is carried out, while maintaining the characteristic features of the modulated signal-response and displaying the values signal amplitudes on the light-signal indicator in a logarithmic scale, by which the operator identifies the search object. 2. A device for implementing the method according to claim 1, consisting of attachments installed on an unmanned aerial vehicle (UAV), consisting of an NRL, a video camera, a GPS module, a data transmission channel and an autonomous control panel and information display; NLR consists of a transmitter, antenna system, duplex filter, receiver as part of the second harmonic path, third harmonic path, reference generator, switch, demodulator; digital module as part of a two-channel ADC, processor, receiver controller, transmitter controller, radio control panel, characterized in that the NRL uses a circular polarization antenna system containing three microstrip antennas for each operating frequency range, located coaxially - a lower frequency emitter is located below them are emitters of the second and third harmonics, respectively. 3. The device according to claim 2, characterized in that the circularly polarized antenna system consists of two mutually orthogonal pairs of folded dipoles.

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