  Metasurfaces, the two-dimensional counterpart of metamaterials, have caught
great attention thanks to their powerful control over electromagnetic waves.
Recent times have seen the emergence of a variety of metasurfaces exhibiting
not only countless functionalities, but also a reconfigurable or even
programmable response. Reconfigurability, however, entails the integration of
tuning and control circuits within the metasurface structure and, as this new
paradigm moves forward, new reliability challenges may arise. This paper
examines, for the first time, the reliability problem in programmable
metamaterials by proposing an error model and a general methodology for error
analysis. To derive the error model, the causes and potential impact of faults
are identified and discussed qualitatively. The methodology is presented and
instantiated for beam steering, which constitutes a relevant example for
programmable metasurfaces. Results show that performance degradation depends on
the type of error and its spatial distribution and that, in beam steering,
error rates over 10% can still be considered acceptable.
