Strongly Coupled Magnetic Resonance Systems Research Articles

Compact Broadband Planar Resonator With a Viaed Double Spiral for Robust Wireless Power Transfer

A common problem for most strongly coupled magnetic resonance (SCMR) wireless power transfer (WPT) systems is the dramatic efficiency drops by surrounding high-dielectric objects, e.g., people, caused by the narrow bandwidth of the systems due to a high quality factor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> ). In this paper, a compact broadband planar double-spiral resonator with a via is proposed to obtain a robust SCMR system with a stable efficiency where interference from high-dielectric surrounding objects is mitigated. The increased bandwidth is obtained without compromising power transfer efficiency by introducing coupling enhancement to the structure while <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> is reduced. The bandwidth of the system is increased by over 15% compared to a conventional system with single-sided resonators, and the efficiency is comparable. In this paper, it is found that the location of the via affects both the efficiency and bandwidth of the SCMR system. Meanwhile, this paper reports an experiment with human hand phantom and a simulation study with multi-layered tissue model, both of which mimic a real human-involved environment, and successfully demonstrate the stability and high efficiency of power transfer of the proposed broadband resonators in a WPT system. Moreover, the proposed structure is tested to be less sensitive to misalignment between the transmitter and the receiver, and the proposed method is compared to the systems proposed for similar human-involved environments. This proposed viaed double-spiral resonator is a promising candidate for a robust WPT system for human-involved environments.

Miniaturization of SCMR Systems Using Multilayer Resonators

Multilayer elements are used to miniaturize the size of highly efficient wireless power transfer systems based on the Strongly Coupled Magnetic Resonance (SCMR). Specifically, inspired by miniaturization techniques used in antennas, multilayer resonators in conformal SCMR systems (instead of single-layer resonators traditionally used) are tightly stacked to significantly shrink the size of CSCMR systems. An analytical methodology is developed, based on Kirchhoff's law and Maxwell's mutual inductance formula using elliptic integrals, which can predict the system's resonance. Excellent agreement is shown between analytical, simulated and measured results. Based on our results the proposed multilayer CSCMR systems can operate at significantly lower frequencies than traditional CSCMR systems, while maintaining significantly smaller size as well as providing significantly higher efficiency and transmission range than traditional CSCMR systems.

Cylindrical Misalignment Insensitive Wireless Power Transfer Systems

The widely used wireless power transfer method known as inductive coupling, suffers from dramatic efficiency drops; even over short distances. Strongly coupled magnetic resonance (SCMR) was introduced recently, and can achieve high efficiency at larger distances when compared to inductive coupling. However, standard SCMR systems are highly sensitive to the alignment between the transmitter and receiver, which is an issue that has limited their application in practical wireless powering systems. This paper proposes a new SCMR-based topology that can maintain a constant high efficiency through 360° of misalignment. Specifically, a cylindrical geometry is proposed for the SCMR transmitter instead of using planar loops. Two types of materials are used: copper wire and flexible PCB, and their performances are compared and studied. This new system is able to achieve efficiency above 40% for the entire 360° misalignment without null points, and for the majority of angles the efficiencies stay at 70%. In addition, this new system is wearable and can be used as a portable wireless powering device.

Misalignment Sensitivity of Strongly Coupled Wireless Power Transfer Systems

A traditional strongly coupled magnetic resonance (SCMR) system is highly sensitive to the alignment between the transmitter and receiver elements, which is an issue that has limited their applicability in practical wireless power transfer systems. This paper proposes, for the first time, a novel set of SCMR-based topologies that are less sensitive to misalignment while providing large wireless powering efficiencies. Specifically, instead of using planar coils for the transmitter and the receiver, we connect two orthogonal coils together into a 3-D model to provide misalignment insensitivity. Three SCMR systems (standard SCMR, conformal SCMR, and hybrid SCMR systems) are studied and compared to the proposed 3-D SCMR system in terms of angular azimuth, angular elevation, and lateral misalignment. Also, the ranges of these SCMR systems are compared. It is shown that the proposed misalignment system achieves above 40% efficiency for the entire range of 360° of angular misalignment. Also, our results show that the proposed misalignment system provides longer range.

Spiral resonators for optimally efficient strongly coupled magnetic resonant systems

The wireless efficiency of the strongly coupled magnetic resonance (SCMR) method greatly depends on the Q-factors of the TX and RX resonators, which in turn are strongly dependent on the geometrical parameters of the resonators. This paper analytically derives the equations that can be used to design optimal spiral resonators for SCMR systems. In addition, our analysis illustrates that under certain conditions globally maximum efficiency can be achieved.

Optimal Design Parameters for Wireless Power Transfer by Resonance Magnetic

The wireless power transfer (WPT) efficiency of systems based on strongly coupled magnetic resonance (SCMR) depends on the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -factor of the system elements, which is a function of the geometrical parameters. This letter analytically derives the equations that can be used to design optimal loop and helical elements for SCMR systems. Also, for loops and helices, a global maximum condition is derived in order to design SCMR systems with maximal efficiency.