LOOP ANTENNAS WITH UNIFORM CURRENT IN CLOSE PROXIMITY TO THE EARTH: CANONICAL SOLUTION TO THE SURFACE-TO-SURFACE PROPAGATION PROBLEM

In a recent study, the classical problem of a large circular loop antenna carrying uniform current and situated at the Earth's surface has been revisited, with the scope to derive a totally analytical explicit expression for the radial distribution of the generated magnetic field. Yet, the solution arising from the study exhibits two major drawbacks. First, it describes the vertical magnetic field component only. Second, it is a valid subject to the quasi-static field assumption, which limits its applicability to the low-frequency range. The purpose of the present work is to provide the exact canonical solution to the problem, describing all the generated electromagnetic field components and valid in both the quasi-static and non-quasi-static frequency regions. These two features constitute an improvement with respect to the preceding solution. The canonical solution, which is obtained by reducing the field integrals to combinations of known Sommerfeld integrals, is seen to be also advantageous over the previous numerical and analytical-numerical approaches, since its usage takes negligible computation time. Numerical simulations are performed to show the accuracy of the obtained field expressions and to investigate the behavior of the above surface ground- and lateral-wave contributions to the fields in a wide frequency range. It is shown that in the near-zone the two waves do not predominate over each other, while the effect of the lateral wave becomes negligible only when the source-receiver distance is far greater than the skin depth in the Earth.