Effect of Symmetry on Insertion Loss in SRR and CSRR Transmitarray Unit Cells Implementing the Element Rotation Method

Insertion loss variation with respect to rotation angle is examined for geometrically symmetrical and unsymmetrical split ring resonators (SRR) and complementary split ring resonators (CSRR) transmitarray unit cells implementing the element rotation method. Generalized design conditions for the implementation of the method on transmitarrays are derived. Based on the S-parameters obtained by full-wave electromagnetic simulations and field analysis, it is shown that the symmetry of CSRR unit cells has an important effect on decreasing insertion loss variation with respect to rotation angle. Up to 3 dB improvement in insertion loss is achieved for the symmetrical single ring double split CSRR type unit cell. It is also shown for two nested non symmetric SRR unit cells that, insertion loss is almost independent of the element rotation when the transmission is mainly provided by the symmetrical part of the unit cell.