Dual band circular polarization selector using asymmetric SRR mirrors

In this work we aim to design circularly polarized flat mirror/reflectarray to work at a dual frequency. The design approach uses a unit cell made by four assymetrical split-ring resonators with an opposite rotation plus an element size variation, a seen in Fig.1 Fig. 1. Proposed structure (unit cell). The SRRs are made on copper on a FR4 substrate. There is a metallic (copper) plane mirror behind the structure. The inner rings have a radius of 5.8 mm (1st and 3rd quadrant) and 5mm (2nd and 4th quadrant). The outer rings have a radius of 10.2mm and 10mm, respectively. As we may see in Fig.2, the proposed structure presents a dual-band circular polarization selection: in the band around 2.97 GHz it absorbs LHCP incident waves while reflecting LHCP incident waves, doing the opposite around 3.28 GHz Fig. 2. Reflection coefficient for a circularly polarized wave normally incident on a structure as shown in Fig.1. The superindexes +/- stand for right-handed/left-handed circular polarized waves

Analysis of chiral effects in non-planar metamaterials with oblique incidence

One of the main research lines of the Grupo de Electromagnetismo of the Universidad de Cantabria is focused on the study and characterization of planar chiral metamaterial (CMM) structures implemented on printed circuit board technology. The objective of this communication is to analyze the influence of the angle of incidence on the chiral behavior of metamaterial structures. A variation of the split ring resonator (SRR) particle has been used as unit cell of the periodic metamaterials analyzed. From this structure, the effect of the angle of incidence on the chiral response is analyzed, evaluating variations in the geometry that provide different types of interaction between unit cells or between the incident wave and the structure. The SRRs are printed only on one side of the printed circuit board. Fig.1. This way, with normal incidence the structure is achiral. The obtained results show that the angle of incidence is a key parameter for the structure in order to present a chiral behavior. In this case, the chiral behavior is shown as a high difference between the transmission levels of the two eigenwaves (left handed and right handed circular polarized waves), i.e., circular dichroism