Abstract
For years, in the field of underwater acoustics, a line of research with special relevance for applications of environmental monitoring and maritime security has been developed that explores the possibilities of non-linear phenomena of sound propagation, especially referring to the so-called parametric effect or self-modulation. This article shows the results of using a new modulation technique based on sine-sweep signals, compared to classical modulations (FSK and PSK). For each of these modulations, a series of 16-bit strings of information with different frequencies and durations have been performed, with the same 200 kHz carrier wave. All of them have been tested in the Hydroacoustic Laboratory of the CTN and, through the application of cross-correlation processing, the limitations and improvements of this novel processing technique have been evaluated. This allows reaching better limits in discrimination of bits and signal-to-noise ratio used in underwater parametric acoustic communications.
Highlights
The study of parametric generation has generated great interest since Westervelt published his article in 1963 [1]
Parametric underwater acoustic communications use the non-linear effects that are generated in the underwater channel, for data transmission
The theory of the emission of a parametric broadband signal assuming that the acoustic signal propagates in flat waves deduced by Berktay, which corresponds to the pressure of a wave that travels along the x axis in time t and distance r, is represented as follows: h r
Summary
The study of parametric generation has generated great interest since Westervelt published his article in 1963 [1] It has become popular in the field of underwater acoustics as regards the processing of parametric array signals [2,3,4]. The medium that by non-linear effects is responsible for demodulating the emitted wave gives rise to new frequencies, among them the difference frequency. This theory has been widely used in the design of parametric sonars.
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