Radiation Characteristics of Linear Log-Periodic Dipole Array Antennas Placed Near a Lossy Ground

Abstract

The radiation properties of linear log-periodic dipole array antennas placed near a finite conductivity earth is investigated analytically. A method of moment solution is developed to solve the integral equation associated with the log periodic antenna array. The effect of finite ground conductivity is taken into account by using the appropriate Green's function which is derived from the well known Sommerfeld solution of the finite conductivity semi-infinite space. Piecewise sinusoidal pulse functions are employed as describing and testing functions. In computing the mutual impedance matrix elements, Sommerfeld type integrals are encountered which are computed by applying a numerically efficient technique. After computing the current distributions on the dipole elements of the log-periodic array the far field of the antenna is computed by employing the stationary phase integration technique. Several type log-periodic dipole arrays placed near a finite conductivity ground are computed. The effects of conductivity variations on the radiation patterns, antenna efficiency and input impedance are investigated.