In satellite-assisted IoT communications, circularly polarized (CP) phased array antennas enable devices to directly connect with the satellites. This paper proposes a shared-aperture dual-CP antenna where low-band and high-band antennas are coaxially arranged for miniaturization. The low-band antenna is a dual-feed shorted ring patch loaded with small circles, whereas the high-band antenna is a compact single-probe-fed patch loaded with an oval parasitic patch. Both low-band and high-band antennas have broadband characteristics. Cross-band decoupling in the high-band is achieved by exciting the TM21mode of the low-band antenna and loading a parasitic ring. Additionally, the shorted metallic vias of the low-band antenna form a metallic back-cavity for the high-band antenna to further suppress interference from the low-band, and a pair of stubs is loaded on the feed of the high-band antenna to improve the port isolation in the low-band. Four prototypes, each consisting of 2×8 dual-band antennas, are fabricated and measured. Broad overlapped impedance and axial ratio bandwidths from 12.2 to 14 GHz and from 16.1 to 17.8 GHz are achieved for the low-band and high-band operations. A small frequency ratio of 1.29 is realized while the cross-band isolation exceeds 38 dB in the low-band and 26 dB in the high-band. The proposed dual circularly polarized antenna can achieve a scanning range of ±50° in both bands. As a result, the proposed compact dual-CP phased array antenna supports integration with small IoT terminals, while enabling stable connections for mobile devices or satellite terminals.

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.

Non-orthogonal multiple access (NOMA) is one of the most significant technologies to meet the demand of high spectral efficiency (SE) in the fifth generation (5G) cellular networks. The utilization of simultaneous wireless information and power transfer (SWIPT) contributes to prolonging the battery life of the mobile users (MUs) and enhancing the system energy efficiency (EE), especially in the NOMA scenario where the inter-user interference can be reused for energy harvesting (EH). In this paper, we study the achievable data rate maximization problem for the downlink multi-carrier NOMA (MC-NOMA) network with power splitting (PS)-based SWIPT, in which power allocation and PS control are jointly optimized with the limitation of available power budget as well as the requirement for EH. The considered non-convex optimization problem is arduous to tackle, resulting from the presence of the coupled variables and the inter-user interference. To cope with the problem, a decoupled approach is developed, in which the power allocation and PS control are separated and the corresponding sub-problems are respectively solved through Lagrangian duality method. Furthermore, an alternative approach based on deep learning is proposed, which is capable of effectively obtaining the approximate optimal solution according to the empirical data. Simulation results confirm the effectiveness of the proposed schemes, and demonstrate the superiority of the combination of PS-based SWIPT with MC-NOMA over SWIPT-aided single-carrier NOMA (SC-NOMA) and SWIPT-aided orthogonal multiple access (OMA).