Characteristics Analysis Of A Fan-shaped Array Of Log-periodic Dipole Antennas And Implementation Of Software

In this dissertation, the characteristics of a fan-shaped array of log-periodic dipole antennas in the free space or over an imperfectly conducting ground plane are analyzed and calculated in detail. Based on the method introduced by the author and the formulae in the dissertation, the software for analyzing the characteristics of the fan-shaped array is programmed .1. The essential theory and major methods for analyzing log-periodic dipole antennas and wire antennas are summarized. Based on the need of engineering, for the first time , an iterating method for analyzing the log-periodic dipole antenna excited by voltage is introduced. The method of moments and equivalence transmission matrix of the antenna are suitably integrated. The electrical characteristics (radiation pattern, gain, input impedance, voltage standing wave ratio, etc.) and the variable phase centers of the log-periodic dipole antenna in the free space are analyzed and calculated in detail, taking into account all mutual coupling effect. The results of comparison are presented which show that the method and software are precise.2. The characteristics of a fan-shaped array of log-periodic dipole antennas in the free space are analyzed and calculated in detail. All the antenna symmetries and the reciprocity character of the Z matrix are carefully taken into account in order to calculate only the elements of the Z matrix which are different from all others. Making use of the principle of a log-periodic dipole antenna, the long elements in the unexcited long dipole region can be truncated at certain conditions. After the optimizing for the algorithm, the calculating time can be decreased evidently. The relation between the electrical characteristics of the fan-shaped array and the parameters (the number of log-periodic dipole antenna, the angle between the two adjacent antenna, etc.)of the fan-shaped array construction is discussed.3. During calculating the radiation pattern of a large circular array of log-periodic dipole antennas, a simple and applied method is introduced.4.The method for solving the Electric Field Integral Equation of horizontal and vertical electric dipoles over an imperfectly conducting ground plane is discussed. A discrete image method to evaluate the Sdmmerfeld integral in the near field and amethod to evaluate the Sommerfeld integral rapidly in the far field are reviewed.5. The electrical characteristics of a fan-shaped array of log-periodic dipole antennas over an imperfectly conducting ground plane are calculated in detail and tested. The broadband characteristics and the relation between the electrical characteristics of the fan-shaped array and the parameters (highs above a natural ground, a conductivity ,a dielectric constant, etc.) of the log-periodic dipole antennas position is discussed.6.The function and usage of the software for analyzing the fan-shaped array of log-periodic dipole antennas are introduced.