Optimal horn antenna design to excite high-order Gaussian beam modes from TE/sub 0m/ smooth circular waveguide modes

The availability of medium-power gyrotron tubes (10-30 kW, CW) at millimeter-wave frequencies (30-100 GHz) allows applications such as advanced ceramic sintering, surface coating, radar, remote sensing, deep-space communications, etc. The concept of high-order Gaussian beam modes, which, under some conditions, can be assumed to be free-space modes, is applied to transport efficiently the power generated by a gyrotron for technological applications. A family of optimized nonlinear horn antennas is investigated in order to get the maximum coupling between the guided output mode of the gyrotron and the Gaussian beam modes. The numerical simulations show very favorable coupling with a conversion efficiency of about 99.8%.