  Printed circuit metasurfaces have attracted significant attention in the
microwave community for their versatile wavefront manipulation capability.
Despite their promising potential in telecommunications and radar applications,
few transmissive metasurfaces have been reported operating at millimeter-wave
frequencies. Several secondary effects including fabrication tolerances,
interlayer near-field coupling and the roughness of conductors are more severe
at such high frequencies and can cause significant performance degradation.
Additionally, very accurate experimental techniques are required in order to
characterise these effects. In this work, we present highly efficient
refracting metasurfaces operating at 83 GHz. We use a synthesis technique that
minimizes performance degradation due to effects such as interlayer near-field
coupling and conductor roughness. Our experimental characterization includes an
accurate determination of the intensity of all forward propagating Floquet
harmonics in a broad frequency range. The experimental data shows very good
agreement with full-wave simulation and verifies our synthesis method.
