Akhmedov R. Field of Impulse Radiating Antennas in Linear and Nonlinear Medium

Dissertation for the degree of a candidate of physical and mathematical sciences in specialty 01.04.03 Radiophysics. V. N. Karazin Kharkiv National University of the Ministry of Education and Science of Ukraine, Kharkiv, 2020. The manuscript is a theoretical investigation of impulse ultrawideband electromagnetic field properties in near and far radiation zones. The whole thesis topic is united by the same approach of radiation and reception problems solving with an attention to near zone effects. The idea of the approach is to avoid furrier transform and provide a solution in time domain. As the result the solution will not carry near radiation zone as a spatial case of radiation. Most of problems considered in the manuscript have impulse radiating antenna as a source of electromagnetic filed. The attention to near radiation zone is caused by energy concentration with nonlinear interactions and impulse shape distortion. The analytical solution for the nanosecond electromagnetic pulse radiation into nonlinear medium with near zone accounting was obtained for the first time. The circular aperture is considered as a source of a single nonstationary electromagnetic pulse with Heaviside like time dependency. The obtained analytical statement for e- filed intensity contains multiple integral over fast oscillation function with Bessel function core. The integral was numerically calculated with explicit accuracy by multidimensional quadrature rules of Simpson-Runge. The obtained statement of nonlinear filed intensity contains integral coefficient, but the dependency from azimuthal angle and maximum magnitude are presented in closed form. The statement allowed to observe time domain analogs of known nonlinear effects. Also, graphical analysis of the statement performed. Moreover, the cubic nonlinearity was generalized to the case of weak polynomial nonlinearity. The nonlinear propagation modeling does not include the influence of medium dispersion. The obtained liner solution in closed form was applied to information transmitting and reception modeling. The analysis and literature review faces out the near-far communication problem. The manuscript contains the patented methodic of information extraction with near zone accounting. The methodic is based on usage of topolectal separated on encoder and decoder physical neural network with long-short term memory as a structural unit. Keywords: time domain, electromagnetic pulse, ultrawideband, Kerr nonlinearity, weak nonlinearity, evolutionary approach, machine learning, recurrent neural networks, long-short term memory.