Adaptive transmitter for seasonal variations of the underwater acoustic channel in the Black Sea

摘要

It is known that a slight change in the speed of sound underwater will modify the properties of the underwater acoustic channel (UAC). The diurnal and nocturnal changes of the sound speed profile (SSP) will determine the UAC to be highly variable. This variability has a negative impact on the performance of an underwater acoustic modem (UAM). Therefore we must take into account the daily changes of the sound speed profile when we design an UAM. Developed in this way an underwater communication device will transmit efficiently and reliably to the surface the acquired scientific data. In this article we present diurnal and nocturnal mean sound speed profiles for each season computed using conductivity, temperature and depth (CTD) data acquired in the north-western region of the Black Sea from 1889 to 1998. The CTD information was obtained from the NOAA's oceanographic and atmospheric database. Then AcTUP simulation software was used to create the model of the underwater acoustic medium and to obtain the daily frequency response changes of the UAC for each season, for the region of interest. Based on these results we propose an adaptive architecture for an analog transmitter which could be used in the analog front-end of an UAM.