Indian Startup D Cubed Develops Printable Passive Radar Decoy for UAV-Based SEAD Missions

Indian defence startup D Cubed is developing a lightweight passive radar decoy that can be carried by small unmanned aerial vehicles to create a much larger radar return than the aircraft would normally produce.

The concept is aimed at Suppression of Enemy Air Defences, or SEAD, missions, where expendable drones can be used to complicate an adversary’s radar picture, draw attention away from manned aircraft and potentially force air-defence units to reveal their positions.

D Cubed’s published configuration uses a compact radar-reflecting payload designed to fit inside the nose of a UAV. The company describes the device as a roughly 120 mm spherical structure weighing between 350 and 500 grams.

Unlike an active electronic decoy, it does not transmit radio-frequency signals or require its own power supply. Instead, the system reflects incoming radar energy in a controlled manner so that a small drone can generate a stronger radar return.

The company says the current design is optimised for the X-band, covering roughly 8 to 12 GHz, and has been simulated to produce a radar cross-section of about 1.5 square metres.

D Cubed describes this as being in the range of a conventional fighter-sized radar return. That does not mean the UAV can fully reproduce the radar signature of a specific combat aircraft. Radar cross-section changes with frequency, viewing angle, aircraft configuration and several other factors, while modern air-defence systems use more than a single RCS figure to classify targets.

The practical value of the concept lies elsewhere.

A small UAV fitted with such a reflector could appear significantly more important to a radar than its physical size would suggest. Several decoy drones approaching from different directions could therefore increase the number of tracks that an air-defence network has to evaluate.

If a radar begins tracking the decoys, its location and operating characteristics may become easier to detect. If surface-to-air missiles are fired at the drones, the defender may expend costly interceptors against comparatively inexpensive targets.

That is one of the central problems modern SEAD operations attempt to create for an opponent: forcing air-defence units to choose between remaining silent and losing situational awareness, or activating their sensors and making themselves easier to locate.

A Passive Device Rather Than an Electronic Jammer

The D Cubed approach is relatively simple compared with active electronic warfare payloads.

The reflector uses an additively manufactured internal structure with graded dielectric properties. D Cubed says it is experimenting with Gyroid and body-centred cubic lattice geometries that can reduce the weight of the device while retaining the required electromagnetic characteristics.

A conductive backing made from materials such as copper or silver reflects radar energy back through the structure.

Because the device has no transmitter, amplifier or dedicated power source, it can potentially be produced at lower cost and carried by smaller UAVs.

D Cubed estimates a manufacturing cost of around ₹2,500 for the reflector itself, although that figure is a company target rather than an independently verified production cost.

This low-cost approach matters in a decoy role because such aircraft must be treated as expendable. A decoy becomes much less attractive if its payload costs nearly as much as the interceptor it is intended to draw.

How It Could Be Used in Practice

The most straightforward employment would involve launching decoy UAVs ahead of a larger strike package.

The drones could follow routes and altitudes chosen to resemble a credible incoming threat. From the perspective of a defending radar, the stronger reflected signal could make them more difficult to dismiss immediately as small commercial-class UAVs.

Other sensors would still be able to provide clues.

A fighter-sized radar return attached to a slow-moving drone is not automatically convincing. Radar operators can analyse speed, altitude, acceleration and flight path, while infrared and electro-optical sensors may reveal that the target is physically much smaller than its radar return suggests.

That means an effective decoy mission would require more than simply fitting the reflector to an inexpensive quadcopter.

The host UAV would need sufficient speed, endurance and flight-control accuracy to present a tactically credible profile. Multiple vehicles would probably be more useful than a single decoy, particularly if their routes and timing were coordinated.

Used in a swarm, such systems could increase the number of contacts presented to an air-defence network and make target prioritisation more difficult.

A Tool for Exposing Air-Defence Radars

Passive decoys can also support the detection of hostile air-defence systems.

Many surface-to-air missile batteries attempt to limit radar emissions because active radars can be detected and geolocated by electronic-support systems.

Sending radar-enhancing UAVs into defended airspace could encourage an air-defence unit to activate search or fire-control radars.18

Once those emissions are detected, their location can potentially be passed to aircraft, artillery, loitering munitions or anti-radiation weapons.

The decoy therefore does not need to penetrate deeply or survive for long to have value. In some missions, its purpose would simply be to trigger a reaction.

This is one reason inexpensive unmanned aircraft are becoming increasingly relevant to SEAD operations. Losing a small drone is far less costly than exposing a manned combat aircraft to the same threat.

The Concept Worth Watching

The D Cubed programme reflects a broader shift in air warfare towards inexpensive systems designed to complicate expensive defensive networks.

Modern surface-to-air missile systems combine long-range radars, command networks and increasingly sophisticated interceptors. Destroying them directly can be difficult and costly.

One response is to make the defender process more targets than it can comfortably handle.

A passive radar reflector is one of the simplest tools for doing that. It does not attempt to jam a radar or electronically create false tracks. Instead, it changes the physical radar signature of an expendable aircraft.

If D Cubed can demonstrate the claimed performance in flight, the technology could be incorporated into different UAV designs rather than being tied to a single airframe.

Its greatest value may therefore not be in perfectly impersonating a fighter aircraft. A more realistic role would be to make small drones appear important enough that an air-defence network cannot safely ignore them.

That is a much more practical objective — and one that could make low-cost passive decoys useful alongside swarm aircraft, loitering munitions and conventional SEAD platforms.

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