A Miniaturized Dual-Polarized Tri-Band Antenna Based on Multimode and Stacked Scheme for Multiband Aperture-Shared Base-Station Applications

A miniaturized dual-polarized tri-band antenna based on multimode and stacked scheme is proposed for multiband aperture-shared base-station application. The proposed antenna covers the operation frequencies of 1427–1518 MHz (1st band), 1920–2180 MHz (2nd band), and 3300–3800 MHz (3rd band), corresponding to the n1 band, n50–n51 bands, and n78 band for 5G NR. Dual-mode operation is achieved by loading four split rings which are coupled to the folded dipole, thus providing the 1st and 2nd frequency bands. As to the 3rd frequency band, a high-band element is stacked above the dual-band element. The 1st and 2nd frequency bands share one feeding structure, while the 3rd frequency band is fed independently. Due to the above strategies, radiation interference is avoided, and stable broadside gains around 7 dBi with a minor fluctuation of 1.65 dB are realized within the three bands. Meanwhile, good isolation higher than 20 dB between different frequency bands is achieved within a small area of
$0.14^{2}\lambda _{\mathrm {L}}^{2}$
, where
$\lambda _{\mathrm {L}}$
is the wavelength at the lowest frequency of 1427 MHz. Besides, the middle-band-to-low-band (MB-LB) and high-band-to-middle-band (HB-MB) frequency ratio can be adjusted within the range of 1.27–1.61 and 1.64–2.5, respectively. These results indicate that the proposed tri-band antenna is a favorable candidate for multiband aperture-shared base-station applications.