Mode Filters for Oversized Rectangular Waveguides

In order to suppress trapped-mode resonances and other disturbing phenomena related to the existence of higher-order modes in oversized waveguides, suitable mode filters are required. In this paper such filters are described for rectangular waveguides in which only the dominant H₁₀ mode is wanted. The unwanted modes to be suppressed by the mode filters are classified as 1) E_mn and H_mn modes with n ≠ 0, and 2) H_m0 modes with m ≠ 1. These two types of modes must be treated separately and require different approaches to the mode-filtering problem. For both classes several constructions of mode filters are described and analyzed.