  We present a dual cut-off, dc-tunable low-pass microwave filter on a
superconducting Nb microstrip with uniaxial asymmetric nanogrooves. The
frequency response of the device was measured in the range $300$\,KHz to
$14$\,GHz at different temperatures, magnetic fields, and dc current values.
The microwave loss is most effectively reduced when the Abrikosov vortex
lattice spatially matches the underlying washboard pinning landscape. The
forward transmission coefficient $S_{21}(f)$ of the microstrip has a dc-tunable
cut-off frequency $f_d$ which notably changes under dc bias reversal, due to
the two different slope steepnesses of the pinning landscape. The device's
operation principle relies upon a crossover from the weakly dissipative
response of vortices at low frequencies when they are driven over the grooves,
to the strongly dissipative response at high frequencies when the vortices are
oscillating within one groove. The filter's cut-off frequency is the vortex
depinning frequency tunable by the dc bias as it diminishes the pinning effect
induced by the nanopattern. The reported results unveil an advanced microwave
functionality of superconducting films with asymmetric (ratchet) pinning
landscapes and are relevant for tuning the microwave loss in superconducting
planar transmission lines.
