Nagoya Institute of Technology, Department of Computer Science and Engineering, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
Phys Med Biol. 2013 Sep 7;58(17):N241-9. doi: 10.1088/0031-9155/58/17/N241. Epub 2013 Aug 13.
The present study discusses the applicability of the magneto-quasi-static approximation to the calculation of the specific absorption rate (SAR) in a cylindrical model for a wireless power transfer system. Resonant coils with different parameters were considered in the 10 MHz band. A two-step quasi-static method that is comprised of the method of moments and the scalar-potential finite-difference methods is applied, which can consider the effects of electric and magnetic fields on the induced SAR separately. From our computational results, the SARs obtained from our quasi-static method are found to be in good agreement with full-wave analysis for different positions of the cylindrical model relative to the wireless power transfer system, confirming the applicability of the quasi-static approximation in the 10 MHz band. The SAR induced by the external electric field is found to be marginal as compared to that induced by the magnetic field. Thus, the dosimetry for the external magnetic field, which may be marginally perturbed by the presence of biological tissue, is confirmed to be essential for SAR compliance in the 10 MHz band or lower. This confirmation also suggests that the current in the coil rather than the transferred power is essential for SAR compliance.
本研究讨论了在无线功率传输系统的圆柱形模型中，磁准静态近似法在计算特定吸收率（SAR）方面的适用性。在 10MHz 频段内考虑了具有不同参数的谐振线圈。应用了一种由矩量法和标量位有限差分法组成的两步准静态方法，该方法可以分别考虑电场和磁场对感应 SAR 的影响。从我们的计算结果可以看出，我们的准静态方法得到的 SAR 与相对于无线功率传输系统的圆柱形模型的不同位置的全波分析结果吻合良好，这证实了准静态近似在 10MHz 频段内的适用性。与磁场感应的 SAR 相比，外部电场感应的 SAR 可以忽略不计。因此，对于在 10MHz 频段或更低频段下可能会受到生物组织干扰的外部磁场剂量学，确认其对于 SAR 合规性是至关重要的。这一确认也表明，对于 SAR 合规性来说，关键是线圈中的电流，而不是传输的功率。
