3rd French conference on acoustics
J. Phys. IV France 04 (1994) C5-1137-C5-1140
Utilisation de signaux Doppler tolérants en trajectographie active ; essais en merM.E. ZAKHARIA1 and F. JOLY2
1 CPE-ICPI Lyon, LASSSO Laboratoire d'Acoustique, Systèmes, Signaux et SOnar, 25 rue du Plat, 69288 Lyon cedex 02, France
2 CPE-ICPI Lyon, LTS Laboratoire de Traitement du Signal, 25 rue du Plat, 69288 Lyon cedex 02, France
The precision and the range of currently used trajectography system is mainly noise-limited. Increasing system performance has to go through the use of matched filtering. As, aside ambient noise and multipath, the Doppler effect is the most important disturbance encountered in the case of trajectography, the signals used have thus to be Doppler tolerant ones and any processing scheme has to take into account this phenomena at every step. In this paper, we describe a new system using a special type of linear period modulated chirps well known for their performance in the case of constant speed. As there is no optimal solution, in the case of constant acceleration, the same signals, although sub-optimal, have been used and the performance loss remains acceptable. The paper describes sea experiment using this type of signals associated to real-time digital filters. The results obtained with the improved acoustical system are compared to the data issued from surface positioning systems (radar, optics, DGPS) associated to a short baseline and a ship positioning. The results of both trajectography are coherent within a range of few metres.
© EDP Sciences 1994