A relativistic backward wave oscillator for directly generating circularly polarized TE11 mode

A relativistic backward wave oscillator for directly generating circularly polarized TE11 mode is proposed. In the device, the electrodynamics structures are divided into two groups in azimuth, each group consisting of two opposite 90 degrees sectors, to produce two orthogonal TE11 modes. The axial position of the two groups is shifted to each other with a quarter of slow wave structure period to achieve a 90 degrees phase difference between the two orthogonal TE11 modes. In particle-in-cell simulation, a circularly polarized TE11 mode with 1.5 GW power has been demonstrated. The amplitude ratio between the two orthogonal TE11 modes is smaller than 0.5 dB, and the phase difference is close to 90 degrees. (C) 2016 AIP Publishing LLC.