The TE201 Waveguide Singlet: A Design Approach Based on Charts

Abstract

In this work, we analyze the behavior of TE201 waveguide singlets, proposing dimensioning criteria applicable in the portion of the single-mode bandwidth of the input waveguide comprised between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.4f_{c}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.6f_{c}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{c}$ </tex-math></inline-formula> is the dominant mode cut-off frequency. We address the relationship between the physical features of the singlet and the equivalent circuit parameters, by proposing a method to build ad hoc charts from full-wave simulations based on mode-matching. In the framework of an extracted pole waveguide filter design procedure, the initial dimensioning of the singlets is completed quickly through the charts and the final filter optimization is extremely fast, the initial design being accurate enough. The validation of this procedure is shown with a suitable design example of a filter with zeros both above and below the passband.