Velocity measurement by symbiotic combination of conventional and coherent Doppler sonars

Pulse-to-Pulse coherent Doppler sonar has the advantages of quick-response and high accuracy when compared with the conventional Doppler sonar and has become widely used in laboratories and for commercial products. However, this system has the limited range and ambiguity velocity, which limits more general applications. Multi-frequency and dual time intervals have been proposed to enlarge the ambiguity velocity, but it is still in adequate. Conventional Doppler sonar has no ambiguity velocity and its velocity range is virtually unlimited as we had expected, but the accuracy of conventional Doppler sonar is not good with short time lags. In this paper, the symbiotic combination method is introduced to take advantage of both conventional and coherent Doppler sonar. The symbiotic combination method can provide accurate velocity without ambiguity velocity and has a much shorter time lag compared to the conventional method. A simulation using symbiotic combination method was carried out with different SNR, and the results indicate that this method can be used to provide highly accurate velocity information with a short time lag.