Amplitude-Frequency Shift Affecting the Accuracy of Velocity Lag Measurements

Purpose of research of this work is to develop a mathematical model to study the effect of amplitude-frequency offset on the absorption coefficient when using velocity lags with Doppler effect, different parameters such as aperture size, absorption coefficient, height and angle of directivity.

Methods. In this work, methods were used to model the amplitude-frequency signal shift with the Doppler effect: 1)Signal spectrum analysis method: used to study the frequency characteristics of signals, including the determination of frequency, amplitude and other parameters.2)Numerical simulation method: include the use of numerical algorithms and computer programs such as Matlab/Simulink, to simulate the physical phenomena associated with the Doppler effect and absorption. 3)Signal processing method in time and frequency domains: include various techniques for filtering, decomposition of signals and analyzing their characteristics in time and frequency, help to identify the characteristics of signals. 4)Method of mathematical modeling: include the development of mathematical models describing the motion of objects and their interaction with the environment.

Result. In this research, a mathematical model was developed to investigate the effect of various parameters on the amplitude-frequency displacement in an active acoustic system. The modeling showed how aperture size, tilt angle, absorption coefficient and bottom distance have a significant effect, and also revealed a linear relationship between the error coefficients affecting the displacement.

Conclusion. Amplitude-frequency offset studies showed that this phenomenon has a significant impact on the accuracy of Doppler lag measurements. Phased array instruments showed advantages within the long term accuracy framework. Comparison of the amplitude-frequency offset with experimental data revealed good agreement, which confirms the adequacy of the developed model. However, additional modeling is required to verify the influence of other error sources, such as territorial, side lobe coupling, beam alignment, etc., and to study in more detail the influence of roll on measurement accuracy.

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