A Channel-Dropping Filter in the Millimeter Region Using Circular Electric Modes

A. channel-dropping filter in the millimeter region that transfers TE°₀₁ to TE□₁₀ is described and analyzed. The important features are the use of TE⊙₀₁₁ mode in the resonant cavities combined with a mode-selective coupling between circular symmetric and rectangular waveguides which make both heat loss and mode conversion low. Design formulas and experimental results on a model filter centered at 56 kMc are included. Finally, several possible mode transducers and filters based on the idea of mode-selective coupling are described.