Compact Tri-Band Shared-Aperture Antenna With Large Frequency Ratio for 5G Mobile Terminals

In this letter, a compact tri-band shared-aperture antenna with large frequency ratio is proposed for 5G mobile terminals. The antenna consists of a multiple-input-multiple-output (MIMO) antenna pair formed by two symmetrically mirrored shared-aperture inverted-F antenna (SIFA) elements and five dual-layer split ring resonator antenna (DSRRA) elements integrated with substrate integrated waveguide (SIW). The DSRRAs not only form the millimeter wave (mmW) antenna array but also improve the isolation between the two SIFA elements at 3.5 GHz. The proposed antenna has a compact size of 0.46
$\boldsymbol{\times }0.07\boldsymbol{\times }$
0.01
$\boldsymbol{\lambda _{01}^{3}}$
, where
$\boldsymbol{\lambda _{01}}$
is the wavelength in the vacuum at 3.5 GHz. A prototype is fabricated and tested. The measured results show that the antenna can cover tri-band of 3.34-4.04 (19%), 4.78-4.94 (3.3%) and 24.32-29.76 GHz (20%). The measured peak gains are 4.52, 3.72 and 8.52 dBi, respectively. The compact tri-band antenna with large frequency ratio provides a hopeful solution for 5G mobile terminals.