Evolution of Partial Arc Sampling Receiving Theory for Orbital Angular Momentum-Based Communications

In this letter, we propose a general partial arc orthogonal receiving (GPAOR) theory based on the electromagnetic information theory for orbital angular momentum (OAM) orthogonal communication systems. Firstly, the concept of orthogonal receiving for multi-mode OAM set is defined based on antennas’ effective degree of freedom (EDoF). Subsequently, the necessary and sufficient conditions for maintaining the orthogonality between OAM modes using partial arc sampling method are derived. This work completes the existing OAM partial arc sampling receiving (PASR) theory, and the proposed orthogonal receiving condition is valid for both continuous and discrete spatial sampling receiving.