Reconfigurable Phase-Difference Characteristics of Compact 4×4 Butler Matrix Structures

This paper presents the reconfigurable phase-difference characteristics of compact Butler matrix (BM) structures. The reconfigurable phase-difference characteristics are achieved by altering the phase-differences of couplers contained in the BM structure. For this case, capacitances are placed at the intersection of horizontal and vertical coupler arms. To implement the purpose, a 2.4 GHz 4×4 BM with reconfigurable phase-difference is simulated, fabricated, and measured. A Rogers RO4003C dielectric substrate is used for the design and realization. The proposed BM can produce reconfigurable phase-difference characteristics with the phase-difference range from −154°to 157°obtained by varying capacitances from 0.2 pF to 2.3 pF. Moreover, it has a compact size of 54.1 mm × 54.1 mm (0.43λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>× 0.43λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>).