A Low-Profile and Stacked Patch Antenna for Pattern-Reconfigurable Applications

A low-profile stacked patch antenna is proposed for pattern-reconfigurable (PR) applications. A referential circular radiation patch with desired conical beams and broadside beams operation is analyzed. However, due to bad port isolation, slant radiation patterns with high cross-polarization levels occur. Suspended pin loading and gap-coupled feeding techniques are introduced to achieve better port isolation, which leads to stable radiation patterns and low cross-polarization levels. Meanwhile, in order to broaden the operation bandwidth, two stacked square patches integrated with a T-shaped feeding branch are utilized and analyzed for exciting low-frequency resonances at the broadside mode. By controlling the p-i-n diodes implanted in the feeding network, reconfigurable conical and broadside beams are obtained. The measured results show that the proposed antenna yields a 10 dB operation impedance bandwidth of 11%, ranging from 2.41 to 2.69 GHz. The peak gains operating at the conical state and broadside state are 4.5 and 7.7 dBi, respectively. The overall profile of the proposed antenna is only 0.07λ
₀
, where λ
₀
is the free space wavelength at 2.55 GHz.