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Description of the radar set, tactical-technical characteristics

Figure 1: Some transmitting and receiving masts of RIAS on the island of Levant.

frequency: VHF-band
pulse repetition time (PRT):
pulse repetition frequency (PRF):
pulsewidth (τ):
receiving time:
dead time:
peak power:
average power:
instrumented range:
range resolution:
hits per scan:
antenna rotation:


The research radar RIAS (Radar à Impulsion et Antenne Synthétique) is a coherent >MIMO-Radar operating in the VHF-band, the concept of which was described as early as 1973 by Jacques Dorey of the French research institute ONERA (Office national d’études et de recherches aérospatiales). The practical installation took place from 1974 at the Centre d'Essais de la Méditerranée on the French island of Levant (43°02'24.8" N   6°28'50.4" W).

The field of transmitting antennas forms a circle of a diameter of 400 m. The transmitting masts are distributed at intervals of about 15 m, each with a ground plane dipole at the top. The receiving antennas are distributed in a smaller concentric circle. Each transmitting antenna uses an individually coded transmitting signal.

The challenge was the necessary computing power, which must be in real-time. This computing power wasn't available in 1975, so the calculation of the coordinates of a target took the period of a week. However, the results impressively confirmed the function of a MIMO radar. The power of the computer (called TRIAS) got a necessary level now. An operational prototype was developed in collaboration between ONERA and Thomson-CSF. It was installed by Thomson-CSF (now THALES) in the Rouen region in 1984.