Antenna performance improvement by utilizing a small parasitic slot in stacked PCBs for IoT devices

This paper proposes a simple and efficient technique to improve the antenna radiation performance in stacked printed circuit boards (PCBs) for Internet-of-Things (IoT) applications. In the proposed design, a planner loop-type ground radiation antenna with compact size is implemented at the upper PCB for 2.4 GHz applications, while the lower PCB overlaps with the upper PCB, inducing out-of-phase current distributions over the lower PCB, thereby resulting in a narrow bandwidth and low efficiency. Therefore, a small parasitic resonator is utilized on the lower PCB to diminish the undesired out-of-phase current. Higher efficiency and wider bandwidth are thus achieved by tuning the impedance characteristic of the parasitic slot, indicating the proposed technique is effective in improving antenna performance for devices with stacked PCBs.