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New signal processing in a passive sonar with gradient antennapp. 129-134, vol. 3, 2000 Roman SalamonTechnical University of Gdansk, Faculty of Electronics, Department of Acoustics, Gdańsk, Poland Jacek MarszalTechnical University of Gdansk, Faculty of Electronics, Department of Acoustics, Gdańsk, Poland Lech KilianTechnical University of Gdansk, Faculty of Electronics, Department of Acoustics, Gdańsk, Poland Andrzej JedelTechnical University of Gdansk, Faculty of Electronics, Department of Acoustics, Gdańsk, Poland Key words: Abstract: The well-known set up of an acoustic source bearing consists of four ultrasonic transducers located in the corners of a square and an additional fifth transducer placed in the centre of the square. The subtractions of the signals from the opposite transducers are proportional to sine and cosine of the angle of the arrival wave. The subtracted signals are modulated by the signal from the central transducer and treated as co-ordinates (X, Y) of the points exposed on the display with the Cartesian co-ordinate system. However such a simple solution has one serious limitation, viz., it gives satisfactory results only when a signal to noise ratio is high enough, because the noise frequency band is large compare with the bandwidth of measured signal. The paper presents an improved version of the system. Received signals are sampled and their discrete Fourier transforms are calculated. Every spectral line in DFT is presented as an individual point on the monitor. The angular position of the point shows the direction of the wave arrival and the distance from the co-ordinate origin is proportional to the power of the spectral line.Download: Fulltext PDF, BibTeX© Polish Acoustical Society - Gdansk Department, Polish Academy of Sciences. This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported. (CC BY-NC-SA 3.0) |