  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.
