An 8x8 Butler Matrix for Generation of Waves Carrying Orbital Angular Momentum (OAM)

This paper presents the design of an 8x8 Butler matrix in microstrip technology used to superimpose Orbital Angular Momentum (OAM) states. By associating an 8 element circular antenna array to this matrix, one can generate simultaneously and independently waves carrying 8 different OAM and thus multiplex signals at the same frequency and polarization. Each element of the matrix is described and its performance is illustrated. The complete performance of the matrix is then computed using two different methods. Finally, the layout of this matrix having about 8% bandwidth is presented.