  In this work, we present a framework analysis of full-duplex (FD) systems for
Millimeter Wave (mmWave) analog architecture. Given that FD systems can double
the ergodic capacity, such systems experience large losses caused by the
loopback self-interference (SI). In addition, systems with analog architecture
also suffer from other forms of losses mainly incurred by the constant
amplitude (CA) constraint. For this purpose, we propose the projected Gradient
Ascent algorithm to maximize the sum rate under the unit-norm and CA
constraints. Unlike previous works, our approach achieves the best spectral
efficiency while minimizing the losses incurred by the CA constraint. We also
consider an adaptive step size to compensate for the perturbations that may
affect the cost function during the optimization. The results will show that
the proposed algorithm converges to the same optimal value for different
initializations while the number of iterations required for the convergence
changes for each case. In this context, we primarily consider the gradient
search method for a two-nodes FD systems and then we extend the analysis for a
dual-hop FD relaying systems. Finally, we evaluate the robustness of our method
in terms of rate and outage probability and compare with previous approaches.
