To determine the orientation of an antenna with respect to the MS element, the surface current distribution on the element is studied. The resulting surface current densities on the MS element for the corresponding TE and TM reflection (i.e., |S11|→0) and transmission (i.e., |S21|→0) resonances for normal incidence are shown in Fig. 3. For the TE reflection and transmission resonance cases, the MS is only weakly excited. For the TM reflection resonance case on the other hand, the MS is strongly excited with opposite sense circulating current loops. The circulating surface currents flow in equal and opposite directions in adjacent regions of the MS indicating that the magnetic fields created cancel out each other leaving no net magnetic response. Current flow is maximum along the y-direction suggesting that the optimum radiator-MS coupling is achieved when a radiator’s E-plane is aligned with the y-axis of the MS.Figure 3The surface current densities on the MS for normal incidence showing circulating current loops. (a) TM reflection resonance at 15.8 GHz. (b) TE reflection resonance at 19.5 GHz. (c) TE transmission resonance at 19.7 GHz.