Radiation characteristics of the lossy traveling-wave circular antenna

Generating orbital angular momentum (OAM) beams at radio frequency by the traveling-wave circular loop antenna (CLA) has been proved recently, where the analysis are based on an ideal condition. However, antenna loss is unavoidable in practice and sometimes cannot be ignored. In this paper, the radiation characteristics of different lossy traveling-wave circular antennas are studied carefully by both numerical calculation and CST simulation. Results demonstrate that the loss will affect the radiated OAM beams, including both the phase and amplitude; however, it may still work for communication when the loss is within a certain range. In addition, the performance of this lossy traveling-wave CLA can be improved by adopting multi-feed ports at the transmitting end.