Collision avoidance radar system for the bullet train: Implementation and first results

The collision avoidance (CA)-radar system is designed to be mounted on the head of the bullet train, can provide the driver with real-time information about the track ahead, and can allow that driver to detect obstacles on the track. It will work well under all weather conditions day and night, at distances of several kilometers, ensuring a final line of defense for the bullet train against collision events. When designing a CA radar, several principles need to be followed. The system should be active at a range larger than the maximum breaking distance of the bullet train. Antennas installed on the train should not increase the aerodynamic drag for the high-speed bullet train. There are three main functional components in this system, the antenna arrays, the radar analog front end, and the digital section. The antenna arrays consist of a transmit antenna and a receive array, which are used to transmit the radio frequency (RF) signal into the space and receive the echoes reflected off targets simultaneously. The multichannel receiver in the CA radar is composed of eight independent linear channels. Each receiving channel is connected to an antenna, which permits the use of array processing techniques with the linear channel in the direction-of-arrival (DOA) estimation of the targets. The bandwidth and the pulse repetition frequency of waveform can be properly tuned so as to achieve the required range resolution and the unambiguous velocity, which suit the application better. The maximum monitoring distance of the proposed CA radar is 1 km, which is limited by the transmitting power and the complicated environment.