  With the aim of boosting the security of the conventional directional
modulation (DM) network, a secure DM network assisted by intelligent reflecting
surface (IRS) is investigated in this paper. To maximize the secrecy rate (SR),
we jointly optimize the power allocation (PA) factor, confidential message (CM)
beamforming, artificial noise (AN) beamforming, and IRS reflected beamforming.
To tackle the formulated problem, a maximizing SR with high-performance
(Max-SR-HP) scheme is proposed, where the PA factor, CM beamforming, AN
beamforming, and IRS phase shift matrix are derived by the derivative
operation, generalized Rayleigh-Ritz, generalized power iteration, and
semidefinite relaxation criteria, respectively. Given that the high complexity
of the above scheme, a maximizing SR with low-complexity (Max-SR-LC) scheme is
proposed, which employs the generalized leakage and successive convex
approximation algorithms to derive the variables. Simulation results show that
both the proposed schemes can significantly boost the SR performance, and are
better than the equal PA, no IRS and random phase shift IRS schemes.
