Analysis Of Thick Cylindrical Wire Antennas And Wire Antennas Near An Interface By The Method Of Moments

An ideal analysis of antennas is often assumed that antennas are located in infinite free space. However, because of ground existence, the ground influence must be considered if the antenna is near the ground. With the study of boundary condition of vector potentials and the application of Image Method and Sommerfeld Integrals, This thesis deduces the vector potentials of vertical and horizontal dipoles near an interface (both above and below the interface). Based on the deduced vector potentials, the expressions of the electric fields are derived. Also the numerical evaluation method of Sommerfeld Integrals appeared in the expressions is discussed. Finally, applying the current basis function of three-term sinusoidal expansion, the radiation characteristic and input impedance of the vertical and horizontal antennas above lossy ground are analyzed by the method of moments with the variation of frequency, height from the ground and ground parameters.This thesis introduces a moment-method formulation, which is capable of accurately modeling moderately thick cylindrical wire antennas. New algorithms are presented for the efficient computation of the cylindrical wire kernel, thereby making it possible to achieve solution convergence for a wider class of wire antenna structures. This thesis also make a research on the current distribution and input impedance of half-wavelength antennas with different radii, as well as the radiation pattern of vertical thick antenna above lossy ground.