Yiqiang Yu

Efficient Modeling of Open Structures Using Nonuniform Leapfrog ADI-FDTD

The perfectly matched layer (PML) using the split-field formulation has been implemented in a recently developed leapfrog alternating-direction-implicit finite-difference time-domain method (leapfrog ADI-FDTD) for efficient modeling of open structures. To further enhance computational efficiency and modeling accuracy, a nonuniform numerical grid is incorporated in the proposed formulations. Numerical simulations of a 2-D TE wave in an open region and an electromagnetic band-gap Y-power splitter are performed to verify the implementation with the PML. The results show that with the proposed method, CPU time savings can be up to 50% of that of a conventional ADI-FDTD.

A planar magnetically-coupled resonant wireless power transfer using array of resonators for efficiency enhancement

A novel magnetically-coupled resonant wireless power transfer (MCR-WPT) system using an array of printed spiral resonators is presented. By replacing the single transmitting resonator in a conventional MCR-WPT with an array of smaller resonators, the transfer efficiency of the planar WPT system in both the over-coupled and under-coupled regions are significantly enhanced. Furthermore, with a proper design of the driving loop, the proposed WPT is able to provide consistent transfer efficiency even when the receiver is axially misaligned with the transmitter. Two WPT systems of the size of 10×21 mm2 and 21×21 mm2 for the transmitter, and 10×10 mm2 for the receiver are proposed. The results are compared with the conventional planar WPT of the same size. The measurement results show that with the proposed design, the transfer efficiency of the planar WPT system can be increased from 5% to 66% in the over-coupled region and from 0.75% to 40.67% in misalignment region.

A planar positioning-free magnetically-coupled resonant wireless power transfer

A novel magnetically-coupled resonant wireless power transfer (MCR-WPT) system using an array of printed spiral coil (PSC) resonators is presented to expand the receiving area. The resonator array is excited with a single planar driving loop to yield uniform magnetic field distribution at the receiver plane. First, the performance of a conventional transmitter coil array consisting of one transmitting resonator and multiple repeaters without frequency tracking is investigated. Then the performance of the proposed PSC resonator array with novel feed strategy is demonstrated. The results show the proposed MCR-WPT array system is able to provide consistent transfer efficiency when the receiver is axially misaligned with the transmitter. The measurement results are compared with the conventional planar MCR-WPT array and reveal that that with the proposed design, the transfer efficiency of the planar MCR-WPT system can be increased from 2.1% to 65.8% in the misalignment region.

DESIGN OF WIRELESS POWER TRANSFER SYSTEMS USING MAGNETIC RESONANCE COUPLING FOR IMPLANTABLE MEDICAL DEVICES

E-cient and compact wireless power transfer (WPT) systems are proposed and designed for recharging small implantable medical devices. They use the magnetic resonance coupling scheme to transfer power over a relatively large distance. The receiver resonator coil and the load loop are designed in correspondence to size restriction of implantable devices. The dimensions of the coils are optimized and efiective values of the lumped capacitors are investigated and flne-tuned for e-ciency enhancement. Three design conflgurations of the WPT system, each consisting of two coils at the transmitter and two coils at the receiver, are designed and fabricated. The transfer e-ciency is measured over difierent transmission distances and with difierent orientation angles of the receiver coils. The measurement results show good agreements with the simulations and illustrate that the proposed WPT systems exhibit nearly omnidirectional radiation performance. Furthermore, the receiver coils are implanted inside of a biological object to show the power can be transferred efiectively.

A broadband E-plane omnidirectional antenna for 4G LTE applications with MIMO

A broadband E-plane omnidirectional antenna for use in 4G Long-time-evolution (LTE) wireless systems and networks is presented. The proposed antenna operates at a frequency range of 1.8 to 2.5 GHz with a VSWR lower than 1.6:1, covering PCS, UMTS/LTE, Bluetooth, ISM, and WLAN bands; its planar structure and compact design, along with the omnidirectional radiation pattern, makes it very suitable for ceiling or surface mounted 4G indoor and automobile applications.

A hybrid FDTD and leapfrog ADI-FDTD method with PML implementation

In this paper, a hybrid FDTD and leapfrog alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method is presented. The perfectly matched layer (PML) absorbing boundary conditions are also incorporated in the method and non-uniform grids are deployed to efficiently model electromagnetic radiation and scattering in open domains. In the proposed hybridization method, the leapfrog ADI-FDTD is applied to regions of fine grids, while the FDTD is applied to regions of coarse grids. As a result, a single relatively large time step can be used uniformly over a complete solution domain; this yields a significant CPU time reduction in comparison with the conventional FDTD while maintaining accuracy with fine grid regions. The effectiveness and efficiency of the proposed hybrid method are validated and evaluated with numerical results.

Electromagnetic modeling and optimization of magnetic resonant coupling wireless power transfer using coil array

A novel planar wireless power transfer system via magnetically-coupled resonance (MCR-WPT) is presented. It utilizes a transmitter coil array to generate provides consistent power transfer efficiency when the receiver is axially misaligned with the transmitter. In this paper, an optimization scheme is derived by combined use of HFSS/Q3D, Designer/ADS and MATLAB to improve the transfer efficiency of the WPT design. With the proposed optimization strategy, both the memory requirement and CPU cost in computer aided designs and simulations are significantly reduced in comparison with the conventional full-wave electromagnetic modeling. The resultant optimized design of MCR-WPT system is validated with the measurement results.