A wide band low profile linear cross polarizer for millimeter wave applications

In this article, two wide band high-efficiency metasurface structures as a linear-cross polarizer in transmission mode based on asymmetric split-ring resonators (ASRR) are proposed and tested to indicate that this is not a purely theoretical work. A unit cell of the first structure consists of double polarization-sensitive S-shape resonators (SRs) on the bottom side of the dielectric layer. The superiority of this proposed structure is its filtering property and high conversion efficiency at its resonant frequency, 100 GHz, where its cross-polarized transmission coefficient reaches 0.87. The simulation results show that the polarization conversion ratio (PCR) exceeds 85% in the frequency range of 86 to 139 GHz. Additionally, the second structure consistsed of a wire-grid array as the bottom layer. This structure has extremely low co-polarized transmission amplitude which represents a good polarization transformer in cross-direction. Furthermore, this structure has a polarization conversion ration more than 95% in frequency range of 50 to 200GHz, having wider relative bandwidth compared to the first proposed polarizer. The performance of both polarizers has very weak angular dependence under the oblique incident of x-polarized EM wave with from to .A prototype of these proposed polarizers has been fabricated and a good agreement between experimental and simulation results has been observed. These proposed structures can find application in mm-wave and THz sensing and imaging systems which benefit from polarimetric measurements.