The reduction of embedded portable devices involves a magnetic field interference problem when it integrates near field communication (NFC) due to the presence of conductive surfaces, such as ground planes, batteries, or metallic enclosures. Flexible sintered ferrite sheets (FSFS) represent an interesting shielding solution to prevent electromagnetic interferences problems related to NFC, thanks to their ability to control the magnetic flux. The characterization of FSFS effectiveness is analyzed as a function of the sheet thickness in this contribution. This is performed with the aim of determining which is the optimum thickness value to retune an NFC antenna to its original operation frequency value (13.56 MHz) when it is affected by a near conductive surface. A finite element method simulation model is designed and corroborated with the experimental results to evaluate the performance of different FSFS thicknesses in terms of resonant frequency shift, magnetic field strength, and communication distance. An electromagnetic scanner is also used to determine the ability of the best FSFS thickness to shield an NFC transmitter antenna when a battery is set under it, emulating a usual problem. The results obtained show that the magnetic field strength is significantly attenuated and the communication distance is highly shorted. Therefore, besides selecting a material that provides high reflection and low losses at 13.56 MHz, thickness must be considered to ensure the greatest communication effectiveness. Consequently, the use of a wrong FSFS thickness could lead to shifting the resonance frequency to lower values than expected, detuning the communication.

中文翻译：

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通过优化烧结铁氧体片厚度选择提高 NFC 系统的效率

由于存在导电表面（例如接地层、电池或金属外壳），嵌入式便携式设备在集成近场通信 (NFC) 时会出现磁场干扰问题。柔性烧结铁氧体片 (FSFS) 是一种有趣的屏蔽解决方案，可防止与 NFC 相关的电磁干扰问题，这要归功于它们控制磁通量的能力。在此贡献中，FSFS 有效性的特征被分析为板材厚度的函数。执行此操作的目的是确定当 NFC 天线受到近导电表面的影响时，将 NFC 天线重新调谐到其原始工作频率值 (13.56 MHz) 的最佳厚度值。设计了有限元方法仿真模型并与实验结果进行了验证，以评估不同 FSFS 厚度在谐振频移、磁场强度和通信距离方面的性能。电磁扫描仪还用于确定当电池放置在 NFC 发射器天线下方时，最佳 FSFS 厚度能够屏蔽 NFC 发射器天线，模拟常见问题。结果表明，磁场强度显着衰减，通信距离大大缩短。因此，除了选择在 13.56 MHz 下提供高反射和低损耗的材料外，还必须考虑厚度以确保最大的通信效率。最后，