The paper proposes a hybrid RF and wind energy harvester. It is constructed by structural and functional integration of the two dissimilar energy harvesting techniques, constituting a conformal design. The rectifying efficiency can be boosted by the hybrid power source excitation, thereby increasing DC output power compared to standalone power source. A fan-shaped omnidirectional antenna and a hybrid single shunt-diode rectifier are designed to realize energy receiving and rectifying, respectively. A prototype is implemented and measured. The receiving part can achieve 2.29-dBi peak gain and 0.92-dB non-roundness at 1.85 GHz. It can also work smoothly when the wind speed varies from 0 to 12 m/s. The RF-DC conversion efficiency at -20 dBm and AC-DC output voltage at 12 m/s are measured as 20% and 79 mV, respectively. When both RF and wind power sources are accessible, the hybrid DC output power of 1.0 uW can be obtained with -30-dBm RF power and 10m/s wind speed. Moreover, the output power at hybrid rectifying mode is higher than that of simply superimposed RF and wind energy. Efficiency gain of up to 182% can be achieved. The hybrid energy harvester is a good candidate to power the sensors in battery-free IoTs.

A highly integrated RF power and information receiving system is proposed in this paper. The system consists of an antenna, a rectifier, and an information receiving module. The information receiving module acts as part of the dc load. To realize high integration, a dual-band, dual-circular-polarized shared- aperture antenna is implemented. The antenna consists of a left-circular-polarized element operating at 2.4-GHz band, and a high-gain, right-circular-polarized$2\times 2$array operating at 5.8-GHz band. The lower-frequency antenna is for communication, while the higher-frequency one is for power transmission. All the elements share the same aperture, and the radiator of lower- frequency antenna acts as the reflector of higher-frequency elements. Accordingly, a class-F rectifier that matches the higher- frequency array is designed and verified, and a system-level demonstration is implemented. Owing to the high isolation on frequency splitting and polarization diversity, the baseband signal can be successfully demodulated under a 30-dB input-power-level difference at two frequency bands. The base-band information can be displayed by an ink screen. The received RF power can be effectively rectified and power the data-processing modules.