Theoretical and experimental study of the characteristics of a thin circular loop antenna above a homogeneous, dissipative half-space

The problem of two parallel, staggered loop antennas of the same radius located in free space was investigated. Current distributions on the two loops were obtained by solving two coupled integral equations simultaneously using the well-known Fourier series expansion technique. It is found that when the separation between the two loops is large compared to the radius of the wire loops, the coupling between the two coaxial resonant loops is generally much stronger than that between two coplanar loops. It is also found that the change in input conductance, which sometimes can be as large as 60 percent of the value of the input conductance of an isolated antenna, occurs usually when the separation of the two coaxial loops are close to integer multiples of wavelength. Proximity effects not only change the overall amplitudes of the currents on the loops, but the distribution of the currents as well.