A fast and accurate microstrip array model for the analysis of integrated passive components of complex topology

The paper describes a fast and easy to implement approximate model lor coupled rrsicrostrip arrays of arbitrary cross sections. The model is based on the extension of quasi-static computational concepts to the dynamic case, via the introduction of frequency-dependent capacitance models. The results obtained are in good agreement with those provided by more complex computational methods such as the spectral-domain approach

Coupling-Independent Wireless Power Transfer

It is well known that mid-range wireless power transfer can be realized by a link consisting of mutually coupled series resonant circuits operating at the common resonant frequency. However, in such conditions, the link load which maximizes the output power or the transfer efficiency is coupling dependent. This letter provides an analytical solution to this problem by exploiting the frequency bifurcation phenomenon, which occurs after a certain threshold value of the coupling. When the system is operated at one of the secondary resonances, it behaves as an ideal transformer; thus, it is able to deliver to a prescribed load constant output power with constant efficiency. This is true for variable coil distances or coil misalignment, that is, for variable coupling coefficient

Harmonic balance design of wireless resonant-type power transfer links

none4noHarmonic-balance (HB) based nonlinear techniques are exploited for the design of a high-efficiency and medium-power switching mode oscillator, used as continuous power source in a wireless power transmission system. The oscillator power is transmitted through resonant coils over variable distances. To account for the resonant frequency variations, which also tune oscillation frequency, a broadband design of the system is carried out with the oscillator load including the resonant coupling and the rectifier. The oscillator efficiency, the RF-to-DC system efficiency and the DC power are then directly optimized for any coupling distance of interest. A Royer-type oscillator is designed and prototyped using the proposed technique. The oscillator exhibits 40 W at 223 kHz with 75% conversion efficiency while the WPT system efficiency, DC-to-DC, is better than 60% for coupling distances of the order of 10 cmmixedF. Mastri; A. Costanzo; M. Dionigi; M. MongiardoF. Mastri; A. Costanzo; M. Dionigi; M. Mongiard

Criticality mitigation in a quasi-constant coupling position independent resonant IPT network

This paper discusses some significant design issues that are faced in resonant inductive system for wireless power transfer \u2018on the move\u2019. The targeted system adopts a single AC source to power a sequence of transmitting (Tx) coils, placed along the Rx path, whose geometry is optimized to minimize the variations of coupling for every possible Rx position. To retain a constant coupling coefficient, two nearby Tx coils are series-connected and simultaneously activated, establishing a path without any theoretical bound on its length, by a suitable switching network. This work analyzes the effects of asynchronous switching times, which are rigorously accounted for and minimized by a proper design of the compensating circuit elements, minimizing both the voltage spikes and the over currents on the coils, while keeping the system at resonance. A prototype operating at 6.78 MHz is built and experimental validations are carried out to verify the feasibility of a constant coupling link without experiencing the mentioned effects, but the adopted procedure is general and independent on its size or frequency

Maximum Efficiency Solution for Capacitive Wireless Power Transfer with N Receivers

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Optimal design of a wireless power transfer link using parallel and series resonators

The optimal design problem for a wireless power transfer link based on a resonant inductive coupling is addressed in this paper. It is assumed that the magnetic coupling coefficient and the inductor quality factors are known. By employing the conjugate image impedances, the values of the inductances realizing the optimal design with respect to given values of the network input and load impedances are derived. It is demonstrated that there is just one optimal design maximizing both the power delivered to the load and the power transfer efficiency of the link. The four possible schemes corresponding to the use of a parallel or a series arrangement for the two coupled resonators (Parallel-Parallel, Series-Series, Parallel-Series, and Series-Parallel) are considered and discussed. Closed form analytical formulas are derived and validated by circuital simulations

Harmonic-balance simulation of strongly nonlinear very large-size microwave circuits by inexact Newton methods

The paper introduces a new approach to harmonic-balance simulation, based on inexact Newton methods and iterative system-solving techniques. Storage and factorization of the Jacobian matrix are avoided, resulting in a dramatic drop of execution time and memory occupation. HB analyses with several tens of thousands unknowns become possible on ordinary workstations

Image impedances of magnetic resonant wireless power transfer links

In magnetic resonant wireless power transfer the free-space part of the link is realized by using coupled inductances and by adding appropriate series capacitances (so as to obtain resonance). By introducing appropriate reactive matching networks, we remain with a two port lossy network. In this work it is shown that, by taking as reference impedance the image impedances of the two port lossy network, we realize a system with the maximum efficiency. Such a system, in addition, does not suffer from frequency shifts of resonances and similar phenomena. An experimental verification of the proposed approach is also presented

Characterization of wireless power transfer links by network invariants

Networks for wireless power transfer are currently receiving considerable interest. However, it is important to have a common set of parameters in order to describe the performance of these networks. These parameters are the gains and the conjugate image immittances. The conjugate image immittances play a fundamental role and, in this contribution, they are all described in terms of the Rollett stability factor invariant. In addition to the conjugate image immittances three other gains values are necessary to describe a wireless power transfer network: they are the power gain, the available gain and the transducer gain and they also share a common immittance representation