  In recent years, metasurfaces composed of lumped circuit components,
including nonlinear Schottky diodes, have been reported to be capable of
sensing particular electromagnetic waves even at the same frequency depending
on their waveforms, or more specifically, their pulse widths. In this study, we
report analogous waveform-selective phenomena using only linear circuits and
linear media. Although such linear metasurfaces are analytically and
numerically demonstrated to exhibit variable absorption performance, it cannot
strictly be categorized as waveform-selective absorption. It is due to the fact
that the waveform-selective responses in the linear metasurfaces are originated
from the dispersion behaviors of the structures rather than the
frequency-conversion seen in nonlinear waveform-selective metasurfaces. We thus
refer to these linear structures as pseudo-waveform-selective metasurfaces.
Additionally, we show that the pseudo-waveform-selective metasurfaces have
limited performance unless nonlinearity is introduced. These results and
findings confirm the advantages of nonlinear waveform-selective metasurfaces,
which can be exploited to provide an additional degree of freedom to address
existing electromagnetic problems/challenges involving even waves at the same
frequency.
