It is difficult to effectively rectify or convert low power in the circuit stage of harvesters. The high-gain antenna can offer a higher level of power and is beneficial to RF power harvesting in a low power density environment. To extend the narrow beam of the conventional high-gain rectenna, the multiport and multibeam antenna is promising. To pursue a simple configuration and avoid extra beamforming networks, a traveling-wave grid-array antenna (GAA) with two isolated ports and two symmetrically tilted beams is proposed. A prototype is designed and fabricated after a detailed analysis of the GAA with tilted beams and the coplanar stripline-based rectifier. The measured results show that the proposed rectenna is sensitive and effective in a wide-angle range. The harvesting angle range is extended by combining two tilted beams and can be greater than 70$°, where the level of dc power exceeds 100 μW when the power density is as low as 1 μW/cm². A maximum dc output of 3.6-203.8 μW and a maximum RF-to-dc conversion efficiency of 16.3%-45.3% are available at 2.45 GHz, under the condition that the power density ranges from 0.052 to 1 μW/cm².

This letter presents two 2×2 polarization-insensitive dual-polarized rectenna arrays with different power combining strategies for wireless power transmission applications. With a dual-polarized antenna array, the incident wave can be received and decomposed into the horizontally- and vertically-polarized components, which are equally redistributed by a hybrid coupler. By this means, the efficiency of the rectenna, in which the power is equally input to the two rectifiers in parallel, is independent of the incident wave's polarization. Based on the equal power routing mechanism, two rectenna arrays using the RF and DC combining strategies are designed and analyzed. Measurement results show that both rectenna arrays are insensitive to the incident wave's polarization, and have their own advantages and disadvantages.

This letter presents two designs of pattern-reconfigurable wearable antennas for body centric wireless communications (BCWC). The reconfigurabilities of these two designs are realized utilizing two totally different mechanisms. In the first design, two sub-antennas with different radiation patterns are integrated. With a reconfigurable feeding network, the design can switch between the two sub-antennas. In the second design, the antenna's internal structure can be reconfigured to perform different radiation patterns. Measured results verify that both antenna designs provide reconfigurable omni-directional and directional radiation patterns.

The wireless power transmission (WPT) systems consisting of two microstrip patch antenna arrays at 5.8 GHz are investigated. By maximizing the power transmission efficiency between the two arrays, the optimized phases and amplitudes of the excitations for both the transmitting and the receiving antenna elements can be obtained and then realized by feeding networks. As a demonstration, two WPT systems have been designed and fabricated. One uses a 6 × 6 array as the transmitting and a 4 × 4 array as the receiving, and the measured transmission efficiency reaches 39.4% when the two arrays are separated by a distance of 40 cm. Another one uses 8 × 8 arrays as the transmitting and the receiving, and the measured power transmission efficiency reaches 46.9% when the two arrays are separated by a distance of 100 cm.

This communication presents an omnidirectional rectenna array with an enhanced RF power distributing strategy. The proposed rectenna array consists of three bidirectional subarray antennas, a $3\times $ 3 RF power distributing network, and a three-element rectifier array. Utilizing the $3\times $ 3 network to redistribute the varying RF power received by the three antennas, the RF-to-dc power conversion efficiency of the rectenna array can be enhanced under the illumination of electromagnetic (EM) waves with arbitrary incident angles. Measurement results reveal that the proposed rectenna array has an improved omnidirectional-harvesting capability compared with the design without RF power distributing strategy, thus can be readily used for RF energy-harvesting applications.

We present a 3D printed metallic K-band (18-26.5 GHz) passive frontend for satellite communication. It is intended to be used as a unit cell in a large antenna array. The proposed frontend is composed of a two-stage one-by-four power divider, rectangular-to-circular waveguide tapers, and a linear four-element conical antenna array, which are too complex to be fabricated by traditional machining process in a whole piece. Taking the advantage of the 3D printing technology in realizing complex structures, we achieve a highly-integrated passive module. Good agreement is achieved between simulation and measurement. The proposed frontend has impedance bandwidth 19 $\times$ 21 GHz, the maximum gain of 15.5 dBi at 21 GHz, and desirable radiation patterns on both E- and H-planes. The influence of fabrication tolerance like the surface roughness and dimensional tolerance are observed and analyzed. Compared with traditionally fabricated metallic microwave passive devices, the proposed work has a shorter turn-around time and a lower cost. Compared with dielectric 3D printed microwave devices, it features more simplicity in terms of process and better physical robustness. It opens up new possibilities for microwave device fabrication.