Printed Decoupled Dual-Antenna Array On-Package for Small Wirelessly Powered Battery-Less Device

A printed compact antenna array for small wirelessly powered device operating at 900 MHz is proposed. The prototype is developed by printing antenna pattern on a 0.1-mm-thick flexible substrate and folding the printed sheet into a rectangular volume measuring 35
$\,\times\,$
56
$\,\times\,$
12 mm
$^3$
. The edge-to-edge distance between array elements is only
$0.078~\lambda$
. An isolation structure is added to minimize the coupling between the elements. Measurement results show a
$-$
27-dB minimum coupling between the elements, which yields significant gain improvement up to 3.6 dB and radiation efficiency improvement up to 28% over the design without isolation structure. When integrated with rectifier circuits, the proposed design also demonstrates superior performance by generating more dc power. The results have shown the proposed work to be a feasible solution of implementing antenna array for small device to enhance of RF power receiving capability with high compactness.