<title>Analysis of characteristics of slot and dipole antennas of georadar</title>

Abstract

Slot antennas and shielded dipole antennas, including resistive material or resistive elements, are considered. Numerical modeling has been carried out by finite difference method in time domain and by integral equation method in frequency domain. The following characteristics has been studied: `front to back' ratio, near field patterns for pulse radiation, far field patterns and energy flux distribution in frequency domain, gain to the ground and the air, input impedance, transient response. An influence of the spacing between the antennas and the ground was studied. Several ways of using of resistive elements and covering were considered: placing of the resistive material into the spacing and around slot antennas, between the dipole and it's screen, including of resistive elements to the bottom surface of the slot antenna, resistive screen of slot antennas. Some optimal antennas have been found. Influence of antenna's design to characteristics is shown. Dipole antenna with a resistive material between the dipole and the screen may provide greater front to back ratio, then the slot antennas, having the same size. Slot antenna with resistive covering on lateral sides ensures high front to back ratio when it is placed on the ground. Optimal conductivity of resistive covering around slot antennas have been found depending of type of the covering and conductivity of the ground.