  In this correspondence, we present a reconfigurable intelligent surface (RIS)
that reflects an incident signal to the desired direction, depending on the
pulse width. This unique reconfigurability emerges by virtue of the transient
response of the embedded nonlinear circuits within the RIS unit cells. The RIS
does not need any control lines connected to the unit cells or precise
synchronization with the base station, leading to reduced complexity of the RIS
system yet allowing automated beamforming characteristics in accordance with
the incident pulse width. To verify this scheme, an RIS system model using
binary phase shift keying is considered, in which the RIS wireless link is
connected to a single transmitter at the input and two receivers at the output.
Numerical demonstrations show that modulated signals are received with
contrasting bit-error rates in the two receivers, consistent with the
aforementioned pulse-width-based beam control.
