Directional polarization modulation for secure transmission in dual-polarized satellite MIMO systems

In this paper, a directional polarization modulation (DPM) scheme is proposed to enhance the secure transmission performance of the dual-polarized satellite multi-input multi-output (MIMO) system. Indeed, the signal's polarization state (PS) is determined by its two components and two orthogonally polarized arrays are designed to transmit these two components in the proposed scheme. In this way, the transmitted signal maintains its PS in the desired direction but changes in other directions because of the signal's PS is affected by the designed array gain and the nature of the array pattern causes the PS to appear scrambled in undesired directions. Besides, in order to further improve the secure transmission performance, a compensation method is introduced to mitigate the depolarization effect. Theoretical analysis and simulation results demonstrate the proposed scheme offers a better secure transmission performance in dual-polarized satellite MIMO systems.