Ring Dipolar Array for an Efficient Frequency-Selective Energy Harvesting

This paper presents the design, implementation, and performance evaluation of a Ring Dipolar Array (RDA) structure optimized for efficient, frequency-selective RF energy harvesting. The proposed RDA utilizes engineered electromagnetic interactions within its array arrangement to enhance energy capture at targeted frequency bands while preserving a compact design. The resonant characteristics of the ring dipolar elements of the system are utilized to achieve enhanced frequency selectivity and improved RF-to-DC power conversion efficiency. The energy harvesting performance is systematically investigated under varying load conditions and different network configurations, including series and parallel connections, to determine the optimal operating parameters of the system. Both simulation and experimental validations confirm the effectiveness of the proposed structure. The RDA successfully harvests ambient RF energy at 2.6 GHz (S band), to achieve a practical microwave-to-DC conversion under different load conditions. Under series and parallel topologies, the conversion efficiency reaches 31% and 22%, respectively for input power of -4 dBm. The reconfiguration between series and parallel arrangements is entirely passive, involving no switches or control power, and relies on the intrinsic electrical connections of the array. The proposed design provides reconfigurable operation adaptable to varying load conditions, allowing flexible series–parallel arrangements to deliver high voltage or high current. These findings underscore the potential of the RDA as an efficient and practical approach to frequency-selective ambient RF energy harvesting in modern wireless power transfer applications.