What is mode Suppressor | Circular Waveguide mode suppressor

This page describes waveguide mode suppressor basics. It mentions circular waveguide mode suppressors.

What is mode suppressor:
The modes other than the desired ones are undesirable which cause power dissipation. The dissipation of higher order is greater than the dominant mode. The devices used to suppress undesired modes are known as mode suppressors. The one used in a waveguide are referred as waveguide mode suppressors.

Waveguide is constructed to cutoff undesired modes and pass the one interested to be retained. Ideal mode filter performs this operation which totally transmits the desired mode. It is difficult to achieve this type of filter practically.

Circular waveguide mode suppressors

circular waveguide mode suppressors

Conducting elements (e.g. wires or sheets) are mounted in parallel to E field of undesired modes. This will cause large reflection to these modes. At the same time, if conducting elements are mounted normal to E-field of desired mode, the mode gets transmitted without any amount of reflection at all. Figure-1 depicts two mode suppressors of the circular waveguide.

A slot longitudinal in nature in the middle of top and bottom walls of rectangular waveguide acts as mode suppressor. A slot of such orientation does not affect TE10 mode. It prevents propagation od any mode which would require current to cross the slot axis e.g. TE01 mode.

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