A Low Profile Beamforming Microstrip Antenna Array for 5G Applications Using Butler Matrix

This paper presents a low-profile beamforming antenna array fed by
$1\times 4$
Butler matrix and printed on two layers homogeneous stackup substrates for 5G applications in ka-band. The homogeneous stackup substrate is composed of two layers with the same electrical properties. Indeed, the Butler matrix is printed on the lower layer whereas the
$4\mathrm{x}4$
Chebyshev tapered microstrip antenna array, is printed on the top one. The overall dimensions are
$20\times 27\times 0.63\ mm^{3}$
. A switched beam pointing toward four different angles
$\pm 4^{\circ}$
and
$\pm 29^{\circ}$
is achieved. The corresponding values of the gain are respectively 14.5 dB, 13 dB, 13 dB and 14.5 dB at 28 GHz.