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. 2018 Jul 4;18(7):2149.
doi: 10.3390/s18072149.

Acoustic Parametric Signal Generation for Underwater Communication

María Campo-Valera  1 , Miguel Ardid  2 , Dídac D Tortosa  3 , Ivan Felis  4 , Juan A Martínez-Mora  5 , Carlos D Llorens  6 , Pablo Cervantes  7
Affiliations

Acoustic Parametric Signal Generation for Underwater Communication

María Campo-Valera et al. Sensors (Basel). .

Abstract

This paper presents a study of different types of parametric signals with application to underwater acoustic communications. In all the signals, the carrier frequency is 200 kHz, which corresponds to the resonance frequency of the transducer under study and different modulations are presented and compared. In this sense, we study modulations with parametric sine sweeps (4 to 40 kHz) that represent binary codes (zeros and ones), getting closer to the application in acoustic communications. The different properties of the transmitting signals in terms of bit rate reconstruction, directivity, efficiency, and power needed are discussed as well.

Keywords: parametric technique; self-demodulation; underwater acoustic communication.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Pictures of the experimental setup. (a) The lake where the position of transducers is indicated with white circles. (b) Equipment used for the calibrations and measurements.
Figure 2
Figure 2
Airmar P19. (a) Picture; (b) Transmitting Voltage Response (TVR); (c) SPL, highlighting the interesting 200 kHz region for this application.
Figure 3
Figure 3
Signal used in the analysis. (a) Bit 1: Upwards sine sweep signal; (b) Bit 0: Downwards sine sweep signal; (c) 16-bit received signal (black) and filtered at low frequencies (multiplied by a factor of 20, yellow).
Figure 4
Figure 4
Signal analysis using cross-correlation. (a) second time derivative of envelope for bit 1; (b) second time derivative of envelope for bit 0; (c) Cross correlation signal with bit 1; (d) Cross correlation signal with bit 0.
Figure 5
Figure 5
Relative amplitude for string bits.
Figure 6
Figure 6
Normalized amplitude of the received signal for primary (red) and secondary (blue) beam as a function of distance between emitter and receiver. Std means the standard deviation. (a) for bit 1; (b) for bit 0.
Figure 7
Figure 7
Normalized amplitude of the received signal for primary beam (red) and secondary beam (blue) as a function of voltage sent of emitted signal (i.e., feeding voltage before the amplifier). Std. means the standard deviation. (a) for bits 1; (b) for bits 0.
Figure 8
Figure 8
Directivity pattern of the primary and secondary beams.
Figure 9
Figure 9
Influence of the noise in the secondary beam for the string of bits (experimental) and the ones adding some white noise of different amplitude: 2, 5, 7 and 10 mV. (a) Directivity; (b) Relative amplitude; (c) Reconstructed bits.
See this image and copyright information in PMC

References

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