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1

One more conception of an embedded acoustic chirp modem for underwater communication

Kurowski A., Solarska P., Dąbrowski D., Loch M.

Hydroacoustics

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2015

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Vol. 18

103-112

EN

In this paper we present a conception of an embedded acoustic modem dedicated to the underwater communication. The Raspberry Pi is used as a low cost hardware platform. The solution of the physical layer consists in modulation, synchronisation, frames forming, symbol mapping, etc. Specifically, the modulation is based upon linear and hyperbolic chirp signal generation. The synchronisation is based upon the correlation of received and transmitted signals. The performance of the communication is tested by the computer simulation. The simulation is realized by USB sound cards and a wire. In the simulation, transmitted signals are intentionally degradated by the additive white gaussian noise.

2

Vibrator Data Denoising Based on Fractional Wavelet Transform

Zheng J., Zhu G., Liu M.

Acta Geophysica

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2015

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Vol. 63, no. 3

776--788

EN

In this paper, a novel data denoising method is proposed for seismic exploration with a vibrator which produces a chirp-like signal. The method is based on fractional wavelet transform (FRWT), which is similar to the fractional Fourier transform (FRFT). It can represent signals in the fractional domain, and has the advantages of multi-resolution analysis as the wavelet transform (WT). The fractional wavelet transform can process the reflective chirp signal as pulse seismic signal and decompose it into multi-resolution domain to denoise. Compared with other methods, FRWT can offer wavelet transform for signal analysis in the timefractional- frequency plane which is suitable for processing vibratory seismic data. It can not only achieve better denoising performance, but also improve the quality and continuity of the reflection syncphase axis.

3

Modelling multistatic of target detection

Klusek Z., Elminowicz A., Tęgowski J., Szczucka J., Dragan A.

Hydroacoustics

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2008

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Vol. 11

131-138

EN

The paper presents a numerical approach to modelling the detection of underwater targets with a bi- or multistatic active sonar systems in the shallow water areas using different waveform signals. The results of the numerical modelling of surface, bubble clouds and bottom reverberation for CW and using up and down time-varying instantaneous frequency of chirp signals are presented. Some suggestions are made on the basis of the development and practicality for the shallow sea modeling techniques and approaches to existing sonar models. The paper reports the literature of the model components required for active sonar modelling for different propagation conditions. Some examples of scattering of CW and chirp source signals at bubble clouds and corrugated surfaces, and coherence are given. Active propagation and the system performance are surveyed and modelled adaptable to the specific environmental condition of the shallow sea area of the Gdansk Gulf.

4

The method of amplitude weighting of linear frequency modulated chirp signals for radar application

Milewski A., Sędek E., Gawor S.

Elektronika : konstrukcje, technologie, zastosowania

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2008

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Vol. 49, nr 4

165-168

EN

Linear frequency modulated chirp signals are used in radar system. The signals may by easily compressed to increase range of the system. To obtain compressed signal with small sidelobes, weighting function must be implemented. The paper describes some methods of chirp signals weighting that may by useful especially for signals with low compression ratio.

PL

Sygnały z liniową modulacją częstotliwości tzw. chirp są stosowane we współczesnych radarach. Sygnały te, po zastosowaniu tzw. kompresji, zapewniają zwiększenie zasięgu radaru. Zaproponowana w artykule metoda ważenia amplitudowego zapewnia po kompresji niski poziom listków bocznych przetwarzanego sygnału. Aby to osiągnąć, zaproponowano kilka metod ważenia, które mogą być użyteczne dla pewnej klasy sygnałów o małym współczynniku kompresji TB<100 (T - czas trwania impulsu, B - szerokość pasma).