This section presents technical means designed for detection and direction finding of active radio electronic equipment of control and data transmission channels of modern unmanned aerial vehicles (UAVs) and manned aerial vehicles (MAVs). Main users of such systems are law enforcement, overseeing, security agencies.

The solution of radio monitoring tasks is taking place in the context of a sharply increased volume of operating radio-electronic means, expansion of their range, transition to new technologies of information transmission, and widespread use of UAVs by commercial and security agencies. Along with the requirements for expanding the operating range, increasing productivity, increasing noise immunity and other basic parameters of radio receivers for radio monitoring, the need for early detection and localization of UAVs with radio electronic equipment has become urgent. Another important task is localization of UAV ground control points and active jammers.

Engineers of IRCOS JSC have developed a family of fixed, mobile, portable, and manpack technical means of radio monitoring in airspace. Offered products are based on single-channel and two-channel digital panoramic radio receiver of ARGAMAK family with maximum simultaneous bandwidth of up to 24 MHz (Model 4) and 100 MHz (Model 5).

Evaluation of the direction finder coverage area when radio emission sources are carried by aerial vehicles

The operating frequency ranges of the radio-electronic communication systems, control channels and data transmission of modern UAVs and MAVs are located mainly within the frequency range from 118 to 6 200 MHz. To find the possible direction of arrival of UAV, the direction finder must provide azimuth direction finding in the complete sector of azimuth angles (0° – 360°) and in the widest possible sector of elevation angles, taking into account that the actual flight altitude of a UAV with active redio electronic equipment can be from 10 to 5 000 m, and for MAV up to 11 000 m. Until recently, the parameters of the direction finding sector of ground direction finders by elevation angle were not standardized. This section provides an assessment of the area of loss of azimuth direction finding accuracy for direction finders with different vertical direction finding accuracy in the upper hemisphere.

The limiting elevation angle is the elevation angle of the RES transmitter, upon exceeding the value of which a deterioration in sensitivity and the root mean square error (RMS) of direction finding is observed by 2 times compared to the zero elevation angle.

Fig. 1 shows the direction finding areas schematically using the example of two direction finders with maximum elevation angles α and β, where α is less than β. In the area designated by the number “1”, both direction finders provide the rated accuracy of azimuth direction finding, in the area designated by the number “2”, the direction finder with the maximum elevation angle α loses accuracy, in the area designated by the number “3”, the direction finder with the maximum elevation angle β will also function with a loss of accuracy.

Fig. 1. Areas of loss of direction finding accuracy

The following notations are used in Fig. 1: α and β are the limiting values of the elevation angle, H is the flight altitude of the source, R, r are the areas of the zones of loss of accuracy.

Let us estimate the dependences of the radii of the accuracy loss zones for two direction finders with maximum elevation angles α = 15° and β = 60°.

The prototypes of these direction finders are, for example, ARTIKUL-H1 Manpack Direction Finder with AC-HP2 DF Antenna System (operating frequency range 3000 – 8000 MHz, directional patten width at the elevation angle in the upper hemisphere 15°) and the same direction finder with AC-HP8 DF Antenna System (frequency range 220 – 8 000 MHz, directional patten width at the elevation angle in the upper hemisphere 60°). Both antenna systems provide azimuth direction finding within the sector of 0° – 360°.

Figs 2 and 3 show the dependences of the radii of the accuracy loss areas for these two direction finders. In Fig. 2, the flight altitude of the aerial vehicle varies from 50 m to 5000 m, in Fig. 3, for more accurate assessment at low flight altitudes, from 50 to 500 m.

Fig. 2. Dependences of the radii of the areas of loss of accuracy on the flight altitude up to 5000 m

Fig. 3. Dependences of the radii of the areas of loss of accuracy on the flight altitude up to 500 m

The radius of the area of loss of direction finding accuracy varies from 190 to 18700 m for the first direction finder with a maximum value of the elevation angle α=15° at flight altitude of 50 to 5000 m . For the second direction finder with a maximum value of the elevation angle β=60° it varies from 30 to 2890 m.

For transmitter of aerial vehicle power equal or above 0.4 W, and flight altitude from 50 m to 5 km, the value of the direction finding accuracy loss area is estimated to be from 190 to 18700 m, for a direction finder with a maximum elevation angle in the upper hemisphere of 15°. For a direction finder with a maximum elevation angle of β = 60°, with the same transmitter power and flight altitude, the radius of the direction finding accuracy loss area is estimated to be from 30 to 2890 m.

Thus, direction finder with a maximum elevation angle of 60°, for example, ARTIKUL-H1 Manpack Direction Finder with AS-HP8 DF Antenna System or ARTIKUL-MV Mobile Direction Finder, has more than six times smaller radius of the accuracy loss area compared to direction finder with maximum elevation angle of 15°, for example, ARTIKUL-H1 with AS-HP2 DF Antenna System..

Additional advantage of a direction finder with AS-HP8 (elevation angle in the upper hemisphere up to 60°) is the ability to operate without physically changing the antenna system within the frequency range of 220 – 8 000 MHz, which contains the operating frequency ranges of the radio-electronic means of the UAV control and data transmission channels.

When UAV with active radio electronic equipment enters an area of loss of direction finding accuracy, tracking of the aerial vehicle can be continued based on an assessment of the amplitude level of the radio signal from the radio electronic equipment, however, it should be noted that at elevation angles close to the vertical, both direction finding and assessment of the amplitude of the signal from the radio electronic equipment may in principle be impossible due to the pronounced vertical minimum of the directional patterns of the direction finder antennas and the transmitter on the UAV.

Functions of the radio monitoring means

• Automated spectrum monitoring (within 220 – 8000 MHz range)
• Detection and automatic direction finding (frequency range from 220 to 8 000 MHz, azimuth DF range of 0° – 360°, elevation DF range up to 60° in the upper hemisphere)
• Panoramic analysis
• Radio signal recording and technical analysis of the following transmitters:
  • Ground active radio electronic emitters, including stations of radio communications and jammers
  • Active radio electronic emitters of communication, telemetry and control channels, installed on UAVs and MAVs.

Monitoring means proposed by IRCOS JSC

• ARCHA-RP Fixed Radio Monitoring Station (operation over land, sea and in airspace)
• ARGUMENT-RP Mobile Radio Monitoring Station (operation over land, sea and in airspace)
• ARFA-RP Portable Radio Monitoring Station (operation over land, sea and in airspace)
• ARTIKUL-SV Fixed Direction Finder
• ARTIKUL-TV Transportable Direction Finder
• ARTIKUL-MV Mobile Automatic Direction Finders
• ARTIKUL-D11, ARTIKUL-H1, ARTIKUL-MTPortable Automatic Direction Finders
• ARKAN-O Automatic Detector of Active Radio Electronic Equipment
• AS-HP8 DF Antenna System.

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