Maaß Matthias, Griessner Andreas, Steixner Viktor, Zierhofer Clemens
Institute of Mechatronics, University of Innsbruck, Technikerstrasse 13, 6020, Innsbruck, Austria.
Biomed Eng Online. 2017 Jan 5;16(1):3. doi: 10.1186/s12938-016-0297-4.
Improvements in eddy current suppression are necessary to meet the demand for increasing miniaturization of inductively driven transmission systems in industrial and biomedical applications. The high magnetic permeability and the simultaneously low electrical conductivity of ferrite materials make them ideal candidates for shielding metallic surfaces. For systems like cochlear implants the transmission of data as well as energy over an inductive link is conducted within a well-defined parameter set. For these systems, the shielding can be of particular importance if the properties of the link can be preserved.
In this work, we investigate the effect of single and double-layered substrates consisting of ferrite and/or copper on the inductance and coupling of planar spiral coils. The examined link systems represent realistic configurations for active implantable systems such as cochlear implants. Experimental measurements are complemented with analytical calculations and finite element simulations, which are in good agreement for all measured parameters. The results are then used to study the transfer efficiency of an inductive link in a series-parallel resonant topology as a function of substrate size, the number of coil turns and coil separation.
We find that ferrite sheets can be used to shield the system from unwanted metallic surfaces and to retain the inductive link parameters of the unperturbed system, particularly its transfer efficiency. The required size of the ferrite plates is comparable to the size of the coils, which makes the setup suitable for practical implementations. Since the sizes and geometries chosen for the studied inductive links are comparable to those of cochlear implants, our conclusions apply in particular to these systems.
为满足工业和生物医学应用中感应驱动传输系统日益小型化的需求，必须改进涡电流抑制。铁氧体材料的高磁导率和同时具有的低电导率使其成为屏蔽金属表面的理想选择。对于像人工耳蜗这样的系统，数据以及能量通过感应链路的传输是在一组明确的参数范围内进行的。对于这些系统，如果能保持链路的特性，屏蔽就尤为重要。
在这项工作中，我们研究了由铁氧体和/或铜组成的单层和双层基板对平面螺旋线圈电感和耦合的影响。所研究的链路系统代表了有源植入式系统（如人工耳蜗）的实际配置。实验测量辅以解析计算和有限元模拟，所有测量参数的结果吻合良好。然后将这些结果用于研究串联 - 并联谐振拓扑中感应链路的传输效率与基板尺寸、线圈匝数和线圈间距的函数关系。
我们发现铁氧体片可用于使系统免受不需要的金属表面影响，并保持未受干扰系统的感应链路参数，特别是其传输效率。所需铁氧体板的尺寸与线圈尺寸相当，这使得该设置适用于实际应用。由于所研究的感应链路选择的尺寸和几何形状与人工耳蜗的相当，我们的结论尤其适用于这些系统。
