Design Theory of a Multimode Rectangular Waveguide Taper with Truncated Gaussian Mode Conversion Distribution Function

Abstract

Rectangular waveguides are mainly single-mode guides because different types of standard waveguides are manufactured /available for the use over a particular frequency band. For example, the WG-16 type of guides are to be used only in the X-band. The guide dimensions are so chosen that they will not support the spurious modes, if generated. Thus, the mode conversion phenomenon in rectangular waveguides particularly that in a tapered section has not been considered by any previous investigator. But, if the tapered section joins two different types of waveguides and/or subjected to the higher of the input frequencies, they will begin to support the higher order modes and in such cases, the losses due to mode conversion will exceed that due to the reflection alone. Thus in such cases, it becomes necessary to design tapers of minimum lengths which will keep the spurious-mode level to a pre-determined low value.

Indexing terms:

• Taper
• Multimode guide