  We introduce a fluxonic metamaterial on the basis of nanopatterned
superconducting Nb microstrips and employ it for modulation and synthesis of
quantized loss levels in the lower GHz range by a sine-wave quasistatic ac
drive. The nanopatterns are uniaxial nanogrooves with identical and different
slope steepness, which induce a pinning potential of the washboard type for
Abrikosov vortices. For the fundamental matching field, when the location of
vortex rows geometrically matches the nanogrooves, the following effects are
observed: The forward transmission coefficient $S_{21}(f)$ of the microstrips
can be controllably modulated within a range of about $3$\,dB by the ac
current. For the sample with symmetric grooves, depending on the choice of the
operation point in the current-voltage curve, the shape and the duty cycle of
the output signal can be tuned. For the sample with asymmetric grooves,
depending on the ac amplitude, a sine-to-triangular or a sine-to-rectangular
pulse shape conversion is observed. The possibility of synthesizing quantized
loss levels by a serial connection of the two samples with different
nanopatterns is exemplified and can be used for the development of multilevel
excess-loss-based fluxonic devices.
