Overview

Countering enemy drones requires two tools: something to find them, and something to take them down. There are several commercial tools available, but the least expensive cost more than $10,000 each, and can only serve an area of one platoon, so this becomes very expensive very quickly. We’re working to greatly reduce that cost. As of summer 2022, we bought a few commercial jammers using donated funds, for the lucky cases when our soldiers spot enemy drones visually, which is difficult in wooded areas. We currently have nothing but their eyes and ears to find the drones, so our first task is low cost detection and tracking systems. Low cost jammers will come later, so we can equip more platoons with complete systems.

What are the threats in the field?

The Russians are using two different classes of drones. The first is small quadcopters used mainly as eyes in the sky for artillery targeting. This includes commercial drones, mainly from DJI, and DIY drones. The second class is the Iranian fixed wing drones that made the news in October, essentially mini cruise missiles, which the Russians are using to destroy critical energy infrastructure in an attempt to commit genocide against Ukrainian civilians again, this time via winter freezing, instead of via starvation as in the Holodomor that the Russians perpetrated 90 years ago. The purpose of all this murder now is the same as it was then: punishment for seeking independence from Russia.

Which threat are we focusing on, and why?

The Iranian drones are causing massively more death and destruction. However, we’re focusing on the quadcopters, for three reasons.

1. Our engineering skills, available time, and financial resources are inadequate to defeat the Iranian drones.
2. The Iranian drones received political attention, so state-level resources were allocated to solve the problem, including Israel’s Smart Shooter.
3. Russia can continue raining Iranian terror from the sky for years, the same way Hamas does to Israel. Experience with the latter shows that merely defending against the attacks is futile. The evil must be rooted out at the source. In Ukraine’s case, this means forcing out the Russian military, which first requires defeating the Russian units on the front lines — which requires disabling the Russians’ eyes in the sky so that the Ukrainians can safely advance through artillery range.

What technologies can accomplish detection and tracking?

The two classes of drones require different techniques.

Tracking Iranian mini cruise missiles

These weapons are fully autonomous after launch. They aren’t remote controlled. They also have no need to transmit information back to their operators, which means they can operate in radio silence. Therefore, passive RDF (radio direction finding) is impossible; they can only be tracked visually, thermally, acoustically, or by radar. We would love to produce automated tracking systems with those techniques, but we lack time and the engineering experience necessary, so we’re deferring those potential projects until later, to focus on passive RDF for quadcopters as our immediate task. And the mini cruise missiles might soon be thwarted anyway, if Smart Shooter is able to send enough systems, as explained above.

Tracking surveillance quadcopters

These eyes in the sky broadcast real-time video feeds back to their operators, which enables their victims to detect and track them via passive RF monitoring. General techniques for such monitoring include:

• Directional antennas. Automated systems using this technique spin the antenna to scan the sky, and correlate received signal strength with the antenna’s angular position to determine direction to the target drone.
• Doppler shift. This is a spinning system with a non-directional antenna mounted at an offset from the center of spin. The received signal’s Doppler shift induced by the spin is correlated with the angular position to determine direction to the target drone.
• Phased arrays. This compares phases of the received signal at multiple antennas to determine direction to the target drone. This requires not only multiple antennas, but also multiple receivers, making this technique difficult to achieve at low cost.

Enhancement to general techniques

The most obvious way for automated directional antenna and Doppler shift systems to work is with physical rotation. However, moving parts increase fragility, which is bad for battlefield use. In addition, the high rotation speed required for practical Doppler shift systems makes physical rotation impractical. The alternative is virtual rotation, by electronically switching at high speed among multiple stationary antennas physically arranged in a circle.

Triangulation

Any of the techniques above can provide the most critical information: alerts to drone presence, and which way a soldier needs to run with his portable jammer. But another piece of information is highly useful: how far to run? Without knowing this, the soldier must search the entire path of his run. The solution to this problem is triangulation, which requires at least two RDF systems, which further increases the importance of making these systems as low cost as possible.

Transponder receivers

There’s an alternative to RDF for tracking unmodified commercial drones. Major markets, including the USA and Europe, require commercial drones to have transponders, like commercial manned aircraft have, that broadcast their position and velocity. Because of this requirement, major manufacturers, including DJI, include these transponders in their drones. In the common case that these drones are used without modification on the battlefield, the opponent can monitor these broadcasts to track the drones — no RDF necessary. However, the information necessary to receive and understand the broadcasts has historically been a trade secret of the drone manufacturers, to enable them to sell their own receivers, such as DJI’s Aeroscope, at extremely high prices, without competition. But university research successfully reverse engineered this information in the summer of 2022, and we’re working now to commoditize receivers for use by the Ukrainian Armed Forces, including their International Legion.

So, what’s our strategy?

In addition to transponder receivers, we’re working on RDF triangulation via Doppler shift using virtual rotation. We previously prototyped crude RDF using a physically rotating directional antenna. However, besides the fragility of moving parts, the directional antenna is large and unwieldy. For particular types of directional antennas, panel antennas are the least bad, but still awkward, and Yagis and parabolic dishes are even worse. Virtual rotation of directional antennas would require multiples of them, which would further compound the impracticality. Phased arrays are difficult to produce at low cost, as mentioned above. This leaves Doppler shift with virtual rotation as the most practical option, since cheap, compact, robust, non-directional, stationary antennas can be used.

How can we produce useful systems for a fraction of the cost of commercial ones?

For some products, such as highly competitive, mass produced phones, laptops, and other commercial electronics, the profit margin is razor thin. But for anti drone systems, there are few customers over whom the R&D costs can be amortized, so the companies making the systems have no choice but to charge prices many times higher than the cost of manufacture. To make this acceptable to customers, the companies are further incentivized to make sophisticated systems, not the bare minimum necessary for practical utility. Think of it as a market of Lamborghinis, not Hondas. We have two advantages. First, a pair of engineers who can donate some of their time, instead of requiring competitive pay. Second, our target is bare minimum systems, just enough to inform soldiers in the field the approximate direction and distance of incoming drones, so they know where to run with their portable jammers.

What’s our status?

We have no tracking systems in the field yet. We made the switch from directional antennas to Doppler shift only at the end of October, and we’re reusing hardware from our prototype accordingly. Our current progress bottleneck is the demoralizing slog through the swamp of mediocre SDR software necessary for further R&D; when that’s done, our bottleneck will be funding. We have only one microwave engineer, who recently joined us as an advisor. We have one other electronics engineer, responsible for hardware prototyping and writing the necessary firmware, who has limited time available, due to needing to work his paid job now after expending his savings while volunteering in Ukraine and Poland. Our only funding has come from him and from a soldier who served in Ukraine’s International Legion. With current funds, we will only be able to produce one RDF prototype. This is the minimum necessary for practical utility, but at least two would be necessary for triangulation capability. Besides that, the single prototype won’t be adequately robust for field use, and sending it into the field anyway would leave insufficient remaining hardware for further R&D. This is why we’re seeking donations.