An Analytical Model for Fields Radiated from a Resonant Circular Loop Antenna over a Homogeneous Earth

Abstract

This paper presents an analytical model for electromagnetic fields radiated from a circular loop (CL) antenna with an arbitrary current and dimensions placed horizontally over a homogeneous lossy half-space. The analysis is based on the application of the image theory and the reflection coefficient (RC) approximation approach. This method makes it much easier to evaluate the field components radiated from the antenna with quite adequate precision than the Sommerfeld integral technique, which involves the evaluation of improper integrals by numerical methods. The generic field formulas presented in the study are used to derive the axial fields, far fields, and the fields of a uniform current CL antenna over a lossy half-space as special cases. The results obtained with the proposed model for dry earth, moist earth and sea water are in good agreement with the corresponding results from FEKO simulation software, provided that the loop is operating at or near its resonant frequency and that its height above the lossy half space is greater than a tenth of the resonant wavelength.