A quasi-optical mode converter for a W-band gyrotron traveling wave amplifier

A W-band corrugated horn has been designed, manufactured, and experimentally measured at the University of Strathclyde, for integration into a gyro-device as a quasi-optical launcher. This horn converts a cylindrical TE₁₁ mode into a free space TEM₀₀ mode in a frequency band of 84-104 GHz with a reflection better than -30 dB and a Gaussian coupling efficiency of ~98% and directivity of 26.6 dB at 95 GHz. The small beam waist makes such a horn ideal for use with a depressed collector system. The measured results are in excellent agreement with the numerical simulations.