Resonant Reflection From Dipole Arrays Located Very Near To Conducting Planes

Abstract

Abstract-Plane-wave reflection from regular arrays of small particles positioned very near to an ideally conducting plane is theoretically studied. It is found that extremely thin (in wavelength) coverings with resonant properties can be realized if the array particles are small dipole antennas loaded by bulk inductances. This offers a possibility to realize an artificial magnetic conductor as a thin covering over conducting bodies. Dependencies of the resonance frequency and the resonant curve width on geometrical parameters are given. The theory is supported by numerical examples.

Artificial magnetic conductors realized by planar array of loaded loop for antenna applications

“…k 0 is the wave vector, Į is the polarizability coefficient of scatterers and C is so-called interaction constant and the formulation can be found in [17], [18]. The real part of quantity C is positive.…”

“…The real part of quantity C is positive. The real part of the inverse polarizability Į í1 for small conducting particles is also positive, so in principle Re{C} can match the positive real part of Į í1 [17]. The problem is that if the polarizability value is small, its inverse value is large, and it cannot be compensated by the interaction constant.…”

“…For higher polarizabilities the resonance is possible when Re{Į í1 íC} = 0. The reflection coefficient becomes equal to +1 which corresponds to a magnetic surface [17].…”

“…This can be made possible by loading particles by some loads. For example for short strip dipoles with capacitive input impedance if the load impedance is inductive, the particle polarizability near the particle resonance becomes large, which makes it possible to fulfill the resonance condition for a grid over conducting plane [17].…”

Theory of ferromagnetic wires resonating in the proximity of a ground plane: Application to artificial impedance surfaces

“…28 Most state-of-the-art artificial impedance surfaces are designed based on grids of conductive elements resonating in the proximity of a ground plane. Typically, a transmission line approach 20,29 is employed to design arrays of conductive patches, 23 dipoles, 30 or more complex shapes, in which a strong electric current is excited under certain resonant conditions. The novel approach of using ferromagnetic wires is advantageous, since not only can an electric current resonance be excited through the MI effect, but also a magnetic resonance is possible through the excitation of magnetic dipoles in the wires.…”