Printed Dual-Layer Three-Way Directional Coupler Utilized as 3$\,\times\,$ 3 Beamforming Network for Orthogonal Three-Beam Antenna Array

We present a novel printed dual-layer three-way directional coupler, which can be utilized as 3
$\,\times\,$
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
$-$
120
$^{\circ}$
, 0
$^{\circ}$
, or
$+$
120
$^{\circ}$
. 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
$\,\times\,$
3 BFN, an orthogonal three-beam antenna array for 5.8-GHz application has been designed, fabricated, and tested to verify its capability experimentally.