Compact 3-D-Printed 4 × 4 Butler Matrix Based on Low-Cost and Curing-Free Additive Manufacturing
Valentina Palazzi, Arianna Cicioni, Federico Alimenti, Paolo Mezzanotte, Manos M. Tentzeris, L. Roselli
Abstract
This letter presents a 4 × 4 Butler matrix realized using stereolithography 3-D printing technology and liquid metal filling. The matrix is in coaxial technology and relies on circular branch lines and curved 50 Ω lines. Input and output ports are aligned and placed on the same plane, while branch lines are organized using all three dimensions to minimize the length of the connecting lines. A prototype, designed at an operating frequency of 12 GHz, is manufactured and tested, showing a footprint of only 1.7 × 1.3 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . A good agreement between simulated and measured transmission coefficients is observed regardless of the selected input port. These encouraging results open the door to the realization of compact low-cost and high-performing RF beam-steering networks in coaxial technology, based on curing-free additive manufacturing processes.