  In practice, residual transceiver hardware impairments inevitably lead to
distortion noise which causes the performance loss. In this paper, we study the
robust transmission design for a reconfigurable intelligent surface (RIS)-aided
secure communication system in the presence of transceiver hardware
impairments. We aim for maximizing the secrecy rate while ensuring the transmit
power constraint on the active beamforming at the base station and the
unit-modulus constraint on the passive beamforming at the RIS. To address this
problem, we adopt the alternate optimization method to iteratively optimize one
set of variables while keeping the other set fixed. Specifically, the
successive convex approximation (SCA) method is used to solve the active
beamforming optimization subproblem, while the passive beamforming is obtained
by using the semidefinite program (SDP) method. Numerical results illustrate
that the proposed transmission design scheme is more robust to the hardware
impairments than the conventional non-robust scheme that ignores the impact of
the hardware impairments.
