Supplementing a network-centric system of sound receivers with active illumination of observation objects

Rhetorical question: if the extreme side carries out its plan and sends an armada of drones at us, how will we defend ourselves?

The troops mainly use technical means of detecting drones based on active radars. These means have proven themselves to be highly reliable and accurate in determining the azimuth and range of the target.

We propose a battalion-level reconnaissance system based on a network-centric system of sound receivers that establishes 3-dimensional target coordinates.

As noted in the previous article “The use of stationary smart sound receivers as part of a network-centric system» Smart sound receivers operate in a passive mode of listening, filtering and identifying sounds. Receivers react to sharp sounds with a certain frequency passport and practically do not indicate themselves in any way on the ground.

Therefore, at the next step in the development of the idea of ​​a network-centric system, a proposal was born to equip the system with a device for forced sound illumination of targets. All previously obtained theoretical conclusions on passive receivers are preserved.

1 Accuracy of determining target coordinates and choosing the type of sound waves for location

Let's choose the ultrasound range as the echolocation frequency range. We believe that this is advisable for many reasons, since there are many examples of the use of ultrasound in nature.

The dolphin's echolocator, weighing 200 g and producing a signal of 0.1 W, allows the dolphin to act accurately in any environment and exchange information with partners in the school.

Another example of the use of sonar is bats, which have the ability to ultrasonic direction finding of obstacles and hunt midges in the dark. Bats modulate ultrasound from 150 to 30 kHz. Pulse duration 0.2–100ms [1]. Using technical means, frequencies up to 104 kHz can be obtained using the electrostriction method.

In the air, a source with a power of 100 kW can be heard at a distance of 15 km [2].

Since ultrasonic waves have a short wavelength, they can form strictly directed beams, and with the help of a concave mirror reflector, ultrasonic waves can be focused and directed from the source in a strictly defined direction. Ultrasound hardly diffracts and travels straight.

Let us consider the factors influencing the error in the value of Δρ_i in terms of N. Benoit’s method of sampling a separate sound receiver, i.e. With_i — the speed of wave propagation in the medium and Δτ_i — accuracy of time determination using the internal frequency generator of the receiver.

The speed of wave propagation in a medium mainly depends on temperature. Because We plan to send an ultrasound packet over a relatively short range, we will assume that ultrasound propagates in a uniform temperature field.

c_i = const

About the time factor: modern microprocessors have a frequency of 1 MHz, i.e. The timing accuracy is 0.5 µs.

For simplicity, we assume the speed of sound is ~331 m/s. Error Δρ_i will be ~ 331×0.5 10^-6m or ~0.165 mm. Therefore, it is not surprising why bats hunt so confidently in complete darkness, being practically blind.

2 Construction of a network-centric system of sound receivers to cover the territory of the positional zone

Let's consider the layout of stationary smart receivers with an ultrasound emitter to cover the territory of the positional zone in Fig. 1 The signal repository and the computer as part of the system are not shown in the diagram. Then they go through the text with a single term – center.

Smart sound receivers are located on the periphery of the positional area. The number of receivers is determined by the requirement for reliable sound coverage of the perimeter of the position area.

The requirement is taken into account that three receivers from the sample should not be on the same straight line. If you still need to place more than 2 NPs along the long side of the perimeter, then you can shift them in height. The total number of receivers must be at least 5.

The emitter is located in the middle of the zone in standby condition or rare radiation.

The emitter power must be sufficient to cover the positional area and can be estimated based on a 6 dB drop in sound intensity per doubling of the distance from the emitter:

ΔL = -20log(R)

where L – sound intensity in dB;
R – distance from the ultrasound emitter to the calculated point, m.

For a reflected wave from a target object, the formula remains valid, and we will assume that the target reflects the wave without loss.

When an airborne penetration is attempted, some receiver picks up the faint sound of the target object and signals this to the center. The center switches the emitter into the operating mode of emitting ultrasonic pulses.

Receivers record time τ_i the arrival of the reflected wave and transmit it and their current coordinates to the center. Based on the sent data, the center analyzer determines the current coordinates of the sound source by solving a system of equations. The calculations are repeated for each packet of emitter pulses in order to track the trajectory of a dynamic target and its destruction, we assume, by shrapnel.

It should be noted that the presented diagram completely repeats the previously discussed scheme for constructing receivers during combat guarding of a ship at anchorage. In the previous article, we did not indicate the possibility of using a sound emitter in water. We are now correcting this omission.

3 Construction of a network-centric system of sound receivers to accompany a column on the march.

Let's consider the airspace control scheme along the convoy route. The included ultrasound emitter is located in the center of the column.

The receivers move with the column. They can be placed on ground vehicles of the convoy itself, but there is a risk of the formation of dead elimination zones on straight sections of the road. Therefore, it is proposed to consider installing sound receivers on drones.

A group of drones forms a cover squadron. The number of drones must be >= 5. In Fig. Figure 3 shows the combat formation of a squadron of observation posts above a column in the form of a pentagram.

The radius of the control zone sphere is determined by the confident reception of the reflected emitter pulse by receivers on drones. Please note that the receivers on the escort squadron drones will also receive:

– direct emitter wave and

– false reflected waves of their “combat partners” from the squadron.

It is best to filter these signals at the level of the receivers themselves.

With filtering the direct wave of the emitter, everything is quite simple – this signal will always arrive first.

A mechanism for recognizing “friend or foe” in the air is needed. It can be proposed that the receiver, when a direct pulse wave arrives, mixes a secret signal “into the air.” By this superimposed signal, “combat partners” will recognize it and filter out the false signal.

Drones that do not know and do not emit a secret signal will be destroyed by fire from the ground using shells with remote fuses or radio fuses.

results

In contrast to the previously considered cases of using a network-centric system with passive sound receivers for counter-battery warfare, it is proposed to supplement the network-centric system with an active ultrasound emitter for use as part of an air defense system.

Supplementing a network-centric system with a target object illumination device will make it possible to establish the coordinates of objects that produce not only a sharp characteristic sound, but also low-noise objects, for example, quadrocopters, as well as silent objects, for example, observation balloons.

The modified system can be used to cover the territory of a positional zone and to accompany columns on the march.

The cost of the system is very low compared to existing air defense reconnaissance systems.

In the next article we will try to cover the issues of vertical and horizontal interaction between clusters of a network-centric system.

Literature

1. Pocket encyclopedia “The Hutchinson”.

2. V.N. Khmelev, A.N. Slivin, R.V. Barsukov, S.N. Tsyganok, A.V. Shalunov “Application of high-intensity ultrasound in industry”, Ed. AltSTU, Biysk, 2010.