Miniaturisation of Defected Ground Plane Using Complementary Metallodielectric Electromagnetic Band Gap Structures

Abstract

The concept of Complementary Electromagnetic Band-Gap Structures employing dipole elements as conductors and apertures is employed for the miniaturisation of Defected Ground Plane (DGS) structures. Conductor and aperture dipoles are placed in close proximity with a rotation of 90 o between them, in order to produce maximum coupling, which proves to yield maximum miniaturisation in the order of 2.3:1. An efficient numerical method based in Method of Moments (MoM) is used to simulate and predict the surface response of the complementary array. Dispersion curves have been produced to study the modes supported by the array. Simulated and measured surface wave responses are presented for finite size DGSs excited by a transmission line. A substantial decrease of the stop band frequency is observed, as the width of the conducting elements is increased. the incident electric field in this case. The apertures are rotated 90 0 with respect to the conductors, so that both elements will be polarized with the electric field. Floquet modal analysis has been employed for the rigorous full-wave simulation of the unit cell, in the absence of any circuitry. Two coupled Integral Equations are derived upon application of electromagnetic boundary conditions at each interface,. A Magnetic Field Integral Equation (MFIE) is formed for the fields within the apertures and an Electric Field Integral Equation (EFIE) for the currents in the conductors (3). These can be brought into matrix form with application of the Method of Moments (4,5) for the unknown fields and currents. The dispersion characterisation is based on the existence of non-trivial solution when the incidence is assumed zero. In order for the set of homogeneous linear equation to have non trivial solutions, the determinant of the matrix (Z) must be zero (characteristic determinant). By varying the β from zero to the boundary of the irreducible Brillouin zone, all the corresponding characteristic determinants are ploted out for each β. From the plot all the true set minima correspond to each individual propagation mode.