  We introduce the concept and practical design of broadband, ultrathin cloaks
based on non-Foster, negatively capacitive metasurfaces. By using properly
tailored, active frequency-selective screens conformal to an object, within the
realm of practical realization, is shown to enable drastically reduced
scattering over a wide frequency range in the microwave regime, orders of
magnitude broader than any available passive cloaking technology. The proposed
active cloak may impact not only invisibility and camouflaging, but also
practical antenna and sensing applications.
