Kebkal K. Theoretical validation and practical realization in hydro-acoustic communication of signals with continuously spread carrier

The object of study - the processes of formation, distribution and registration of hydroacoustic waves. The purpose of the work was to establish a scientific basis for the construction of technical devices, providing stable and high-speed digital data by hydro-acoustic waves in an environment characterized with time and frequency dispersion of signal power, low propagation velocity and very limited frequency bandwidth. Research methods - methods of mathematical physics, numerical and physical experiments. Apparatus comprising: a digital part - CPU with floating point ADSP21160 SHARC, gate array FPGA Altera APEX 20K300E240, the central processor module DIL / Netpc DNP/1110 with embedded Linux and TCP / IP; analog section - amplifier with automatic gain control (AGC) consisting of the input stage on the basis of low noise AD8605 module technology Digitrim company Analog Devices, and the cascade of AD605 moduls of the technology DSX-AMP (Analog Devices), and power amplifier - bridge PWM technology (Class D) with the output transformer and electronic protection from overloading. In the course of the study, the following new results achieved: 1. First proposed the use of hydro-acoustic waves with a continuous variation of frequency as the carrier of digital hydro-acoustic communication signal and theoretically substantiated the benefits of using the carrier of this type in comparison with a constant frequency carrier. 2. First developed a physical model of a digital hydro-acoustic signal with a continuous variation of the frequency (hereinafter - the sweep carrier), and developed a mathematical model of hydro-acoustic signals with sweep carrier. On the basis of the developed models of received hydro-acoustic signals first formulated and established mechanisms of influence of the effects induced with multipath propagation, and multiplicative (Doppler) shifts. 3. First developed a mathematical model of the methodical error of phase estimation of phase-shift keyed signal with swept carrier. 4. For the first time there was created the analytical evaluation of the distribution of signal amplitude and phase of the signal with swept carrier in the pre-detector of the receiver, as well as evaluated the variances of these distributions, there was investigated (analytically and numerically) the bit error probability for coherent and non-coherent signal reception. 5. First derived theoretically and confirmed experimentally the relationship between the duration of the signal with swept carrier and bit error probability in conditions of multipath propagation and variability of the environment. 6. Analytically expressed the coherence bandwidth of the hydro-acoustic channel for the case when signals with swept carrier used. 7. There was developed a new method for temporal arrangement of swept hydro-acoustic signals, providing a pseudo-random arrangement of the pauses between signals in transmitted sequence, intended to counteract the distortions caused by multiple interactions of the current signal with delayed multipath components of the previous one, as well as there has been further developed the method of digital hydro-acoustic signaling based on the transfer of clusters (groups of data packets). On the basis of quantitative studies of the effect of prolonged signal propagation delay there was established that this method allows to increase the density of the information transfer in channels with large propagation delays. Practical results and the degree of implementation: - created a full-featured the digital hydro-acoustic communication device (experimental samples have successfully passed the departmental tests in marine hydro-acoustic channels); - developed and validated the evidence-based tactical demands to the digital wireless underwater communication devices for the use within underwater sonar systems in the zones of responsibility of the Naval Forces of Ukraine (the requirements approved by the Chief of General Staff of the Armed Forces of Ukraine, March 3, 2008); - developed and approved the tactical and technical requirements for development projects for creation of devices for digital wireless underwater communication devices for the use within underwater sonar systems in the zones of responsibility of the Naval Forces of Ukraine (project of tactical and technical specifications approved by the Commander of Naval Forces of Ukraine, January 9, 2009). - The results of the dissertation are recommended for use in organizations and institutions engaged in sonar development, as well as for use in the educational process of the "KPI".