Cylindrical TE011 /TM111 Mode Control by Cavity Shaping

An appropriate modification of the shape of a cylindrical filter cavity has been used to separate the degenerate TM₁₁₁ (doublet) modes while at the same time providing a slight increase in the already high unloaded Q of the desired TE₀₁₁ mode. Experimental results of mode frequencies and unloaded Q´s are tabulated for a family of shaped cavities. Two low-loss filters utilizing these cavities are discussed. The general correspondence between modes of spherical, cylindrical and rectangular cavities and waveguides is described in order to place the performance of intermediate shapes in perspective.