A Multiband Compact Flexible Energy Collector for Wearable or Portable IoT Devices

A multiband compact flexible energy harvester which consists of a novel slotted broadband antenna and a miniaturized broadband rectifying circuit is proposed for the primary communication (GSM-900, GSM-1800) and industrial/scientific/medical (ISM-2450, ISM-5800) band applications. It is found that the newly designed antenna which combines a coplanar waveguide-based feed structure with a symmetrical sickle groove to obtain the best matching performance and radiation performance. A broadband matching network based on a cross-shaped bent short-cut wire is proposed to maximize the transmission of power and minimize the size of rectifier. At an input power of 5 dBm, the proposed multiband energy harvester obtains 34%-50% efficiency(RF-DC) at 0.9, 1.8, 2.45, and 5.8 GHz. The measurement results proved that for different bent states, the proposed flexible harvester does not display large variations in harvesting efficiency. Therefore, this energy harvester with flexibility, compactness and stability is ideal for wireless power supply to wearable and portable Internet of Things (IoT) devices.