The Anglet: An E/H-plane Bent, 90-Degree Twisted, TE₁₀₁/TM₁₁₀-Mode Singlet Building Block

Abstract

In this work, a subclass of the singlet building block is defined. Termed the anglet, a waveguide cavity-based structure is demonstrated that combines a bend, a 90-degree polarization rotation, and produces one pole and one transmission zero. The anglet is defined due to its unique ability to be viewed as either a TE101-mode singlet or a TM110-mode singlet based on the users coordinate point of view together with the requirements for the bend direction and polarization rotation. Two types of anglets are demonstrated by simulation and a third-order filter is demonstrated for the incorporation of an anglet in a practical design. Emphasis on its unique capabilities are highlighted due to its nature as a fundamental-mode resonator with evanescent bypass coupling. Furthermore, an accurate approximation for the source-load coupling is described and a prototype filter is fabricated and measured in order to validate the concept.

The Anglet: A Novel Singlet Building Block Subclass and Alternatives for E-Plane Cross-Coupled Filter Design

“…In light of these challenges, the versatile and unique physical profile of the anglet allows designers to overcome three fundamental challenges at once, that being: a 90-degree bend, a 90-degree polarization rotation, and the generation of a pole/transmission-zero pair. This structure is a first-order building block and as demonstrated in [13], can be readily applied in higher-order filter designs to achieve complex characteristics. Fig.…”

“…As described in [13] and Fig. 1, the topology diagram of the anglet includes a half-window symbol in order to communicate the angular (E-plane or H-plane) change and intrinsic polarization rotation.…”

“…The characteristic response of an anglet can be described by a 3x3 coupling matrix using equations (1) through (3), from [7], [13], [20], [21] as:…”

“…In light of the drawbacks of this type of structure, the authors have proposed an alternative approach and define a special case of the singlet which is able to not only create the necessary passband pole and functional transmission zero, but also integrate an E/H-plane bend and 90-degree polarization rotation into an ultra-compact structure. The introduction of this novel singlet building block has been defined and termed the anglet [13].…”

“…The following article is provided to the microwave community as an extended version of the award winning paper of the 2023 IEEE Radio & Wireless Week Student Paper Contest [13] and expands the concept in order to demonstrate novel topologies for advanced and compact filter design. Specifically, the use of multiple anglets are demonstrated as a unique alternative to typical E-plane cross-coupled filter designs, with and without the use of source/load coupling.…”