A Compact Dual-Band Triple-Mode Antenna With Pattern and Polarization Diversities Enabled by Shielded Mushroom Structures

In this article, a compact triple-port dual-band triple-mode antenna enabled by a shielded mushroom structure with operational bands centered at 2.4 and 5.8 GHz is proposed possessing both pattern and polarization diversities. By tailoring the dispersive properties of the artificial transmission line (ATL) cells and structuring them into a multilayer architecture, the integrated antenna is capable of generating vertically polarized,
$y$
-horizontally polarized, and
$x$
-horizontally polarized radiation patterns simultaneously at two predefined bands with good port isolations and field orthogonality. The design concept and the analysis of the ATL cells in the form of shielded mushrooms are described, illustrating the dual-band operating principle of the antenna. A proof-of-concept antenna is designed with a footprint of
$0.48\lambda _{0}^{2}$
and a profile of
$0.07\lambda _{0}$
, where
$\lambda _{0}$
is the free space wavelength at 2.4 GHz. The proposed antenna was fabricated and characterized, achieving measured
$S_{11} < - 10$
dB bandwidths of 35 and 85 MHz in the two targeted bands, respectively, with mutual coupling smaller than −15 dB and envelope correlation coefficients below 0.01 for all three ports. Moreover, it is shown that the two operational bands of the antenna can be independently controlled, which reveals the unprecedented degrees-of-freedom in its design. The demonstrated dual-band triple-mode antenna is highly useful for dual-band multimode wireless devices and dual-band multiple-input multiple-out communication systems.