Underwater Acoustic Modem with High Precision Ranging Capability based on Cesium Atomic Clock

Integration of underwater acoustic communication and ranging is extensively needed in practical underwater applications. As the traditional underwater ranging system depends on the time accuracy of the local system, long-term work will unavoidably lead to system clock drift and serious degradation of ranging accuracy. In addition, the adverse characteristic of underwater acoustic channel such as multipath, time variations, and noise also pose severe challenges to the quality of underwater acoustic communication and ranging capability. In this paper, by incorporating the high-precision cesium atomic clock and the robust spread spectrum technology, a spread spectrum acoustic modem with high precision ranging capability is developed. The pool experiment results show that within 60 mins of working hours, the modem is able to achieve an absolute error of 1.0907 m.