A Compact Tri-Band Filtering Antenna System for 5G Sub-6 GHz Applications

This communication presents a novel compact tri-band filtering antenna for 5G Sub-6 GHz n41 (2.515–2.675 GHz), n78 (3.4–3.6 GHz), and n79 (4.8–5 GHz) applications. The antenna consists of a central dual-band element and four single-band elements placed around. Simulated results show that the tri-band filtering antenna has an impedance bandwidth (
$\vert S_{11}\vert < -10$
dB) of 6.6% (2.51–2.68 GHz), 6.3% (3.39–3.61 GHz), and 5.5% (4.73–5 GHz), covering Chinese 5G Sub-6 GHz band. The distance between single-band elements along both the x-axis and y-axis is
$0.31\lambda _{0}$
(
$\lambda _{0}$
is the free-space wavelength of the center frequency at the lowest band), realizing a compact structure of
$0.95\lambda _{0} \times 0.95\lambda _{0} \times 0.2\lambda _{0}$
. Since this tightly spaced structure will easily cause strong coupling, additional filtering structure is added, achieving high isolation over 47 dB between the central and the peripheral elements. The final antenna realizes stable gain in all three frequency bands, showing satisfactory in-band average radiation efficiency and high out-of-band gain-suppression level, making it suitable for 5G Sub-6 GHz wireless communication applications.