Printed Dual-Layer Three-Way Directional Coupler Utilized as 3<formula formulatype="inline"><tex Notation="TeX">$\,\times\,$</tex> </formula>3 Beamforming Network for Orthogonal Three-Beam Antenna Array

Abstract

We present a novel printed dual-layer three-way directional coupler, which can be utilized as 3 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\,\times\,$</tex> </formula> 3 beamforming network (BFN) to provide orthogonal three-beam switching capability. The three-way directional coupler is a passive component with six input/output ports. The signal injected into the input port is equally distributed into the three output ports, with a constant phase difference of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$-$</tex></formula> 120 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}$</tex></formula> , 0 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}$</tex></formula> , or <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$+$</tex></formula> 120 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$^{\circ}$</tex></formula> . Simulation and measurement results show that within 7% relative bandwidth, good matching, high isolation, equal power division, and constant phase difference have been achieved simultaneously. Utilizing the three-way directional coupler as a 3 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\,\times\,$</tex></formula> 3 BFN, an orthogonal three-beam antenna array for 5.8-GHz application has been designed, fabricated, and tested to verify its capability experimentally.