An improved corrugated waveguide mode purifier for TEM output in a V-band overmoded coaxial millimeter-wave oscillator

Abstract

In the overmoded microwave sources, there inevitably exist multi-modes in the output microwave, so it needs to be purified to obtain the single mode output. However, due to the large longitudinal size, the traditional concave-type purifier is not suitable for coaxial devices with large overmoded ratio. The present paper proposes an improved convex-type purifier based on the coupled wave equations. With this purifier, 99.98% TEM mode can be gained effectively under the conditions of diode voltage 355 kV and beam current 3.0 kA. Compared with the traditional concave-type converter, the improved purifier has the higher coupling coefficient and its longitudinal size can be reduced by 40%.