Effect of Ground Conductivity on Radiation Pattern of a Dipole Antenna

Abstract

This paper aims firstly to develop a theoretical formulation of electromagnet ic fields above the earth surface taking into account the finite and infinite conductivity of the ground- which has the advantages of being reasonably fast to compute, secondly to investigate the effect of ground properties on the electric field intensity. For this purpose we have analyzed radiation pattern for finite and infinite ground conductivity, frequencies and different antenna lengths. The monopole is fed to its base. The current distribution along the portion below ground is the image of the current distribution along the original monopole.The image source for calculating electric field, above the infinitely conducting ground surface is just opposite to that of the original source. The image source for calculating electric field above the finitely conducting ground surface is not just opposite to that of the original source. It is affected by the ground properties. For same frequency and identical antenna length but at different ground conductivity, there exists variation in radiation field. It is observed that at small value of ground conductivity the radiation field is small also the direction of radiation field changes. Furthermore it is obtained that rise of frequency increases the radiation field sharply in a particular direction. Finally we can say that at a fixed antenna length, there exists a minimum frequency for measurable radiation field.