An angular symmetric sector structure for the broadband high-power radial rectangular TE10 to axial circular TM01...

A broadband high-power radial rectangular TE10 to axial circular TM01 mode converter (MC) is presented for relativistic traveling wave tubes (RTWTs), which is based on the angular symmetric sector structure. The MC is mainly composed of an input waveguide coupling structure, an M-stage angular symmetric sector structure, a tapered coupling structure, and an output waveguide coupling structure. The tapered matching structure is introduced for the wideband mode conversion and coupling, which can also improve the field distribution to enhance power capacity. The simulated results show that the fractional bandwidth of the radial rectangular TE10 to axial circular TM01 MC is about 9.53%, and its power capacity can reach 28.4 MW. Furthermore, the MCs with different numbers of sectors (N) are also investigated and compared. In addition, to validate the performance, a MC based on a five-stage angular symmetric sector structure (N = 3) was fabricated and tested; the measurement results show good agreement with simulation data. With its combined advantages of broad bandwidth and high power capacity, this MC demonstrates promising application prospects in RTWTs.