A 2-D FFT-Based Transceiver Architecture for OAM-OFDM Systems With UCA Antennas

Radio orbital angular momentum (OAM) provides another perspective of spatial multiplexing to improve the spectrum efficiency. However, multipath induces severe intra- and interchannel crosstalk. To solve the problem in a uniform circular array (UCA)-based OAM system, we first incorporate the effect of sign changing of OAM reflection in modeling the multipath OAM channel. Then, we propose a transceiver architecture for broadband OAM orthogonal frequency-division multiplexing (OFDM) wireless communication systems, which uses baseband digital 2-D fast Fourier transform (FFT) rather than existing radio frequency analog phase shifters to generate and receive the OAM-OFDM signal, thus reducing energy consumption and hardware cost. At last, a flexible 2-D FFT algorithm is developed. Analysis and simulation results show that compared with the traditional row–column FFT algorithm, the proposed 2-D FFT algorithm could reduce the multiplication complexity by $\frac{1}{4}MN\log _2N$ , where $N$ and $M$ are the number of UCA antenna elements and the number of subcarriers, respectively.