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Code signals transmission using MFSK modulation in shallow waters

100%

Zachariasz K. , Schmidt J. , Salamon R.

tom Vol. 4

261--264

The paper presents an acoustic system for the transmission of digital data in shallow coastal waters of which multi-path propagation and intense reverberations are characteristic. To ensure a small error probability of moderate speed transmission, the system uses corrective codes and a technique of incoherent modulation MFSK (Mufti Frequency Shift Keying). To synthesise the transmission signal, estimate the spectrum of the signal received and code and decode the channels, a DSP processor was used. The paper includes the results of a computer simulation in which the system was put to work in the presence of Gaussian noise. The system was tested in shallow coastal waters and the results are discussed in the paper.

The estimation ot virial coefficients via the third harmonics measurements

100%

Leble S. B. , Zachariasz K. , Vereshchagina I. S.

tom Vol. 1

83--88

The derivation of the next nonlinear term of the KZK equation is done within original perturbation scheme on the base of the virial expansion for thermic equation of state. We also derived equations for second and third harmonic components in the nearfield of the sound wave generated by a piston transducer. Calculation scheme for a numerical estimation of the integrals for the fundamental and second harmonics is proposed as well as for the averaged third harmonic component. Some results of performed calculations are given for the illustration of the method possibility and comparison with direct finite difference solutions of the KZK equation.

Hydroakustyczny system transmisji danych w wodach płytkich z zastosowaniem modulacji MFSK

100%

Schmidt J. , Zachariasz K. , Salamon R. , Kilian L.

tom Vol. 83, nr 27

289-292

The paper presents a hydroacoustic system for the transmission of digital data in shallow coastal waters of which multi-path propagation and intense reverberations are characteristic. To ensure a small error probability of moderate speed transmission, the system uses Corrective Hamming's codes and a technique of incoherent modulation MFSK (Multi Frequency Shift Keying). To synthesise the transmission signal, estimate the spectrum of the signal received and code and decode the channels, a DSP processors are used. The paper includes the results of a simulation in which the system was put to work in the presence of Gaussian noise. The system was tested in shallow lake waters and the first results are discussed in the paper.

Method for improving multibeam sonar bearing accuracy

88%

Leśniak W. , Marszal J. , Salamon R. , Zachariasz K. , Schmidt J.

tom Vol. 12

98-108

The paper presents a simple method for improving multibeam sonar bearing accuracy. The principle proposed here is similar to the monopulse method, a solution commonly used in radars and sonars. With no manual or automatic beam rotation, the method offers a substantial reduction in the demand for sonar computational effort. It significantly reduces bearing error for a relatively high signal to noise ratio. The paper gives a boundary value of the output signal to noise ratio which when exceeded satisfactorily improves bearing accuracy.

Multibeam sonar with hexagonal array

63%

Salamon R. , Marszal J. , Kilian L. , Jedel A. , Ostrowski Z. , Raganowicz A. , Rudnicki M. , Wofan Z. , Zachariasz K.

tom Vol. 2

133--138

The paper presents a multi-beam digital sonar that was designed for monitoring and fish stock assessment in in/and waters. The sonar can also be used as a bottom profiler in lakes, rivers and shallow sea areas. The hexagonal piezoelectric transducer array co-operates with a commutator set. The 32 -channel digital beamformer creates 30 narrow receiving beams in every 60o sector of simultaneous observation. The six sectors cover the whole 360o angle range of the sonar. The beamformer digital signal processing is based on second order sampling of echo signals and the phase-shifting principle of beam deflection. The sonar block diagram, beamformer algorithms, as well as transducers designs are discussed.