  This paper presents the experimental demonstration of a
dual-input/dual-output reflective impedance metasurface. The design of the
metasurface relies on the Method of Moments and leverages auxiliary surface
waves to achieve anomalous reflection of two impinging plane waves with
controlled sidelobe levels. The two beams are chosen independently compared to
those in a conventional phase-gradient metasurface where the design presents a
single slope to achieve a certain reflection and all other incident beams would
depend on that slope. A prototype that ensures maximum directivity at two
prescribed reflection angles for the two input waves is then fabricated on a
Rogers RO3003 printed-circuit board using 42 metawires loaded with printed
capacitors. The proposed metasurface is capable of reflecting an incident beam
from $-20^\circ$ to $-55^\circ$ and a second from $+10^\circ$ to $50^\circ$ at
9.93 GHz. The metasurface is experimentally characterized and an illumination
efficiency of at least 89% is calculated for each of the reflected waves,
indicating a high multiplexing efficacy.
