  Reflecting intelligent surface (RIS) has emerged as a promising technology
for enhancing wireless communication performance and enabling new applications
in 6G networks with potentially low energy consumption and hardware complexity
thanks to their passive nature. Despite the significant growth of the
literature on RIS in recent years, covering various aspects of this technology,
challenges and issues regarding the practical implementation of RIS have been
less addressed. This issue is even more severe at D-band frequencies due to the
inherent challenges. This paper aims to connect the requirements and
aspirations from the link-level side to the actually achievable RIS hardware
with the focus on the various models for RIS. In order to obtain a realistic
hardware scenario while maintaining a manageable parameter set, a static
reflect array with similar reflection behavior as the reconfigurable one is
employed. The results of the study enable an improved RIS design process due to
more realistic models. The special focus of this paper is on the hardware
impairments, in particular, (i) the effect of specular reflection, and (ii) the
beam squint effect.
