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HYDROACOUSTICS
ANNUAL JOURNAL |
START | NEW VOL 20 | SEARCH | STATISTICS | PAS - GDANSK DIVISION |
pp. 141-152, vol. 18, 2015 Zawisza Jacek Ostrowski Gdansk University of Technology, Faculty of Electronics, Telecommunications and Informatics, Department of Marine Electronic Systems, GdaĆsk, Poland Key words: positioning system; Doppler shift; homodyne detection Abstract: The article presents a method for solving major structural problems that occur in the
receiver used in the multistatic Doppler system, aimed at determination of the trajectory and
velocity of a moving target. In the system two transmitters emit acoustic continuous sinusoidal
waves at different frequencies. The signals, scattered from a moving target are received by
four hydrophones. Beside of the echoes, much larger signals coming directly from
transmitters are recorded. It has been proved that in the presence of the direct high-amplitude
signal, using currently available A/D converters, there is no possibility to detect the Doppler
shift of small signals. The proposed approach is based on the homodyne frequency conversion
of the received signals. Subsequently, the constant component and other unwanted products of
the frequency conversion are filtered. The results of computer simulation have shown the
effectiveness of the adopted design solution.
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