How to bring down cheap, low-flying drones

Jun 1st 2026|5 min read

Listen to this story

AI Narrated

SMALL DRONES are everywhere. Not just in Ukraine, but flying over air bases in mainland America and Britain, and hitting targets across the Middle East. The technology is cheap, easy to use and accessible, with groups like Hizbullah enthusiastically deploying small quadcopters to hit Israeli tanks. To make matters worse, existing air-defence sensors have been mostly designed to spot bigger threats like manned aircraft and missiles.

The challenge, then, is to develop systems that can spot small, low-flying drones that, like birds, may be skimming treetops and weaving amid other clutter. One approach is to redesign radar systems. Another involves the clever use of acoustics.

Radars emit pulses of radio waves and detect the reflections that come back. They work equally well at night and in bad weather and will spot anything in the air. But, says Thomas Withington, an electronic-warfare expert at RUSI, a think-tank, radar typically filters out small, low-flying objects, which are assumed to be birds.

Echodyne, a firm based in Kirkland, Washington, is developing a smarter alternative. Eben Frankenberg, the company’s boss, says its radar uses three distinctive innovations to identify “smaller, slower, lower” threats.

Most modern radar systems generate their beams with arrays of solid-state emitters (LED-like devices that emit radio waves instead of light) rather than the moving dishes that were once the norm. These are effective but expensive. Echodyne’s workaround is to use a small number of emitters with specialised antennas that adjust the waves they transmit. This is ideal for a low-power, low-cost system for short-range work. Mr Frankenberg claims their radar is an order of magnitude less expensive than traditional systems.

Echodyne’s radar also rapidly shifts the “waveform” of its pulses, meaning their length, intensity and frequency. This allows the beam to switch between modes as it sweeps across the sky. Different waveforms, says Mr Frankenberg, are available for detecting targets in, say, open spaces or against clutter like buildings. Some waveforms have been designed to spot spinning rotor blades, a good way to distinguish a drone from a bird.

Finally, the system classifies the objects it tracks using a machine-learning model. It learns the patterns that correspond to each type of aerial track, from birds to balloons to quadcopters to fixed-wing, improving reliability. This is especially useful for picking out weak signals embedded in clutter, such as a drone flying against vegetation blowing in the wind.

These technologies allow Echodyne’s EchoShield radar, a device the size of a laptop, to spot, track and classify even tiny drones out to a range of around five kilometres. The tracking is accurate enough to direct a camera, or a weapon, at the moving drone.

Another way to hunt for drones is to use sound, an approach pioneered by Ukraine. Fields and forests there are dotted with microphones that can listen for the buzz of Russian drones. Prandtl Dynamics, a startup based in Toronto, has been working on ways to develop acoustic technology further and claims its kit can reveal the presence of a hidden drone nearby even before it is powered on.

It is a remarkable trick. Prandtl’s system, called Dome, blasts out pulses of inaudible ultrasound. If a drone is in the area, this “acoustic interrogation” makes its electronic and mechanical assemblies vibrate, producing telltale squeaks. (The different componentry in a mobile phone, by contrast, would remain silent.) The idea, says Parth Mahendru, Prandtl’s boss, is to turn a concealed drone into “a tiny speaker broadcasting its position”. The firm says Dome has been able to find drones in a backpack, behind a rooftop ledge, and even, in some cases, inside a vehicle.

For now, these detections have been of stationary drones located a few tens of metres away. That is enough, though, to hand a security detail “a huge operational advantage”, says Dan Stanek, chief operating officer at OTTO Engineering, an Illinois firm that supplies communications gear to defence, intelligence and security agencies including America’s Secret Service. OTTO plans to partner with Prandtl on production. Joe Dai, Prandtl’s chief technologist, says a small battery-powered model branded Dome-C, wielded like “a hand-held bug-hunting device”, should be ready for market this summer.

Prandtl is also developing a bigger, plug-in version mounted on a tripod. Ultrasound emitted by Dome-O, as this larger model is called, also makes drones squeak. But Dome-O can be operated in conjunction with microphone systems, like those deployed in Ukraine, that detect drones in flight. Dome-O’s pulses of ultrasound, broader than the narrow beams produced by Dome-C, flood a swath of sky. These pulses augment the acoustic signature already produced by a drone’s motors, rotors and passage through the air, helping microphones pick it up at longer range.

In a noisy city, Prandtl’s 16-microphone array, called Oscura, can spot and track incoming drones as light as 250 grammes out to about 200 metres. With Dome-O switched on, Mr Mahendru says, Oscura’s range can reach 75m farther.

The set-up was put to the test in a counter-drone competition hosted by Canada’s Department of National Defence in downtown Ottawa in November. Christian Labbé, a lieutenant colonel involved in the five-day trials, says Prandtl’s technology was able to track drones amid construction noise, even when out of view. The kit is not yet ready for military use, he adds, citing false positives and the system’s relative fragility. But it was deemed promising enough for Prandtl to tie for second place, bagging a C$375,000 ($270,000) “Diamond in the Rough” prize.

Echodyne, for its part, has already sold its radar devices to America’s air force. The company’s kit is now fitted to warships and set up to defend military bases. A vehicle-mounted version is in service, and the air force and others plan to deploy many more such systems. Such innovations are not about to end the reign of small drones, but the blind spots they exploit are, it seems, beginning to close. ■

Curious about the world? To enjoy our mind-expanding science coverage, sign up to Simply Science, our weekly subscriber-only newsletter.