A device for detecting and/or tracking a projectile has a receiving antenna, for receiving at least an electromagnetic signal emitted by at least one radar, at least one amplifier configured to amplify the electromagnetic signal received by the receiving antenna, and at least one emitting antenna. The emitting antenna is configured to return, at an output of the device, an amplified electromagnetic signal for calculating data indicative of the trajectory of the projectile based at least on the amplified electromagnetic signal. A system for detecting a projectile has a transmitting device mounted on the projectile, a radar configured to sense an electromagnetic signal produced and sent by the transmitting device. The signals emitted from the projectile are limited to the electromagnetic signal sent by the transmitting device, and a processing unit, configured to calculate data indicative of the trajectory of the projectile, based on the sensing of the electromagnetic signal.