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A microstrip loop resonator structure is proposed for short range wireless power transmission around 1 GHz. Physical dimensions of the proposed structure are as small as 3 cm by 3 cm. Power transmission efficiency greater than 80% is achieved with power transmission distance smaller than 5 mm via the strong coupling between two loop resonators, as demonstrated by experimental results. Experimental data also show that, the power transmission performance is insensitive to various geometrical misalignments.

In this paper, we propose and investigate the feasibility of a multibeam forming scheme for microwave power transmission to multiple targets. In the proposed scheme, a wireless power transmitter includes an antenna array that is able to generate multiple microwave beams simultaneously. A unique frequency is assigned for each beam that points toward one of the multiple wireless power receivers. Though the wireless power transmitter employs multiple carrier frequencies, it does not call for large bandwidth as the spacing among the multiple carrier frequencies could be very small. The multibeam forming scheme is implemented by first generating the baseband waveform containing multiple frequency components digitally for each antenna element, and then up-converting the waveforms to the microwave range using image-rejection mixers. Each beam can be adjusted independently by modifying the waveforms digitally. Experimental results are provided to demonstrate the effectiveness of the proposed multibeam forming scheme for wireless power transmission to multiple wireless power receivers simultaneously. Specifically, with a 4-element array, two independent power beams at 5.745 GHz and 5.755 GHz are successfully generated.

Fully-enclosed space embodies a range of practical environments enclosed by conducting walls, such as space stations, man-made satellites, submarines, and aircrafts. Wireless communication and/or wireless power transmission are highly desired in some of the fully-enclosed environments. In this paper, semi-analytical modal analysis is conducted for the purpose of char-acterizing wireless channels in fully-enclosed space. The modal analysis is based upon integral equation method. Cavity Green’s function in the spectral domain (that is, expressed in term of cavity modes) is employed in the integral equation. A cubic cavity with side length 1 meter is analyzed as a specific example, and the modal analysis results are verified by experiments. Measurement data agree with the theoretical analysis very well. As predicted by the theoretical analysis, excellent wireless channels associated with TM 220 mode (with bandwidth of 40 MHz), TM 310 mode (with bandwidth of 10 MHz), and TM 311 mode (with bandwidth of 20 MHz) are demonstrated inside a cubic box with side length of 1 meter.

An experimental implementation of retro-reflective beamforming for wireless power transmission based on the heterodyne technique is presented. Retro-reflective beamforming is achieved by mixing the pilot signal broadcasted by a wireless power receiver with its second harmonic that is obtained by frequency doubling. Non-traditional routings of mixers are employed in order to suppress undesired coupling between pilot signal and wireless power. Experimental results demonstrate that retro-reflective beamforming is able to reconfigure the wireless power beam in reaction to the pilot signal.

Mobile self-organizing networks, such as vehicular ad-hoc network (VANET), in most cases rely on infrastructure deployment to provide access to internet services and other resource. Therefore, it is crucial to optimize the deployment of roadside units (RSUs) in vehicle network. In this paper, we propose a RSU optimized deployment scheme based on large vehicle data, which considers the deployment cost and latency performance synthetically. We deploy the RSU problem as a multiobjective optimization problem for mathematical modeling. On this basis, two-step solution is proposed: firstly, the RSU candidate positions can be obtained by considering the road topology and large vehicle data; secondly, the branch and bound algorithm is used to obtain the better RSU deployment based on the mathematical model. The simulation results show that the proposed RSU deployment scheme uses a small amount of RSU can achieve high coverage and greatly reduce the deployment cost. Moreover, the low latency performance of the vehicle access network and the quality of the latency sensitive application service can also be ensured.

A retro-reflective beamforming scheme based on the heterodyne technique is experimentally demonstrated for wireless power transmission applications. Compared with the conventional heterodyne scheme, the wireless power transmitter does not include any local oscillators. It receives 2.9-GHz pilot signal broadcasted by a wireless power receiver, employs a frequency doubler to obtain the second harmonic signal at 5.8 GHz, and subsequently uses the 5.8-GHz signal to achieve phase conjugation. Experimental results clearly indicate that the proposed scheme is able to deliver directive wireless power beam to the wireless power receiver in reaction to the pilot signal.