Extremely Low-Profile Dual-Band Microstrip Patch Antenna Using Electric Coupling for 5G Mobile Terminal Applications

Abstract

For modern mobile terminals, the shrinking antenna space on terminal frames and the increasing number of 5G antennas motivate engineers to seek new space for antennas. The terminal back cover can provide a large area to accommodate planar antennas; thus, mobile planar antennas are becoming a hotspot recently. This communication proposes a novel approach to develop a dual-band planar antenna with an extremely low profile, which is an urgent need for modern ultra-thin terminals. The first two modes (TM0.5, 0 and TM0.5, 1) of the half-mode patch are adopted to cover the two target bands and a parasitic half-mode patch excited through electric coupling is added to expand the impedance and efficiency bandwidths. The realized dual-band patch antenna operating at partial 5G band N78 (3.40–3.60 GHz) and N79 (4.80–4.97 GHz) is with a profile of only 0.5 mm, about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.006~\lambda _{{\text {L}}}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{\text {L}}$ </tex-math></inline-formula> refers to the lowest frequencies of the operation band). Measured results show that the −6 dB impedance bandwidths are 3.19–3.42 GHz (230 MHz, 6.9%) and 4.77–5.03 GHz (260 MHz, 5.3%) with average efficiencies of −4.2 dB (39.0%) and −3.7 dB (42.6%) at the lower and higher bands, respectively. As far as the authors know, the proposed antenna is with the lowest profile and highest bandwidth-to-volume ratio (BVR) compared to other reported planar dual-band antennas.