The monopole antenna was inserted into the structure until the tip of the antenna reaches the center of the structural height in the y- direction. Keeping in mind that the monopole antenna should be parallel to the polarization axis of the injected electric field, the fact that the electric field is localized mostly between the rods that are perpendicular to the polarization axis inhibits the monopole antenna to be inserted parallel to the polarization axis. Therefore, as shown in Fig. 8(a) the monopole antenna was inserted from the neighboring layer inside and was tilted towards the region of interest with an angle of 16°. The measured electric field intensity was then normalized by the intensity measured with the same tilt angle at the center of the aperture of the transmitter horn antenna.