Method for Identification of Modes in Oversized Waveguide of High-Power 150 GHz Gyrotron

High power gyrotrons using oversized cylindrical resonators, tapers and waveguides are subject to provide a multi tude of modes. For characterisation of the gyrotrons under development a measuring system is required to identify the individual modes in an arbitrary TEmn mode mixture and to determine fractional power contributions. The new method uses four sensors spatially distributed in the far-field radiation of the open-ended waveguide. The measurement is based on the processing of linear combinations of the four high frequency signals.