人體組織與天線間遠場電磁輻射效應之研究

Study of Interaction Effect between Antenna Far-field Electromagnetic Radiation and Human Similar Tissue

黃勝義(Sheng-Yi Huang)

指導教授 ： 孫卓勳

國立臺北科技大學/電資學院/電腦與通訊研究所/博士(2012年)

https://doi.org/10.6841/NTUT.2012.00602

摘要

現今，對於SAR(Specific Absorption Rate)的評估皆以近場方式量測：利用電場探針，量測在人體組織內的電場強度；或是利用熱攝像儀，量測人體組織表面熱溫度。然而，以遠場量測方式評估，亦是值得研究的方式，其所測量的是電磁輻射能量的吸收。
本研究論文提出一種新的量測方式，以評估遠場whole-body SAR，其量測方式為：把輻射源(即天線)置於(1)自由空間；與(2)人體組織附近。由能量不滅定律可知：其輻射源的電磁輻射能量損失，大部分損失是由人體組織所吸收，少部分損失是在電磁傳播時損失。利用Wheeler Cap方法，量測得之電磁輻射能量的差以求出whole-body SAR。
本論文提出之遠場量測方式，經實際量測與模擬比較，其天線效率之相對誤差介於13 %至3 %間；而遠場whole-body SAR量測結果與ref. [4.9]相比較，其量測相對誤差為14 %。藉由實際量測評估電磁輻射能量對人體組織干擾之影響結果顯示，當輻射源-天線與人體頭部組織相距於170 mm，可減少70 %之電磁輻射能量對人體組織之影響程度。本論文提出之量測方式，具有以下優點：快速，省時，簡單。利用遠場量測系統與向量網路分析儀，快速收集所需的量測數據，減少量測時間的花費以評估遠場電磁輻射能量對人體組織之影響。

關鍵字

SAR ； 近場 ； 遠場 ； 天線 ； 電磁傳播

並列摘要

The Specific Absorption Rate (SAR) is generally evaluated by using the near-field measurement method, which is to measure the E-field strength deposited into the human similar tissue with the E-probe and/or to measure the thermal energy deposited on the surface of the human similar tissue with the thermal camera. Furthermore, it is worthy of studying the absorption of EM radiation energy deposited into the human similar tissue by using the far-field measurement system. Therefore, we propose a new measurement method to evaluate the far-field whole-body SAR, which is different from the near-field measurement method.
The far-field measurement method is considering the absorption limit of the EM radiation power absorbed by the human similar tissue. There are two process steps to evaluate the absorption limit: (1) Taking the far-field measurement system measures the EM radiation powers of a radiation source such as antenna placed in free space and in neighbor of phantom respectively. (2) Taking the Wheeler Cap method evaluates the lost EM radiation power. According to the law of conservation of energy, most of the lost EM radiation power is absorbed by the human similar tissue and a little portion is losing in the stage of EM propagation. Therefore, the far-field whole-body SAR can be calculated while the total radiated power and the input power of a radiation source are known.
The evaluated far-field whole-body SAR is compared to the ref. [4.9], which the relative error is within 14 %. According to the measured results, the EM radiation interaction effect can be greatly reduced approximately by 70 % when the separation distance of the EM radiation source and the human similar tissue is more than 170 mm. The measured results of the antenna efficiency are compared to the simulated results, which the relative errors are between 13 % and 3 %.
The proposed new method has the good advantages of simplicity, rapidity, and saving time, which means that a small quantity number of data collection is necessary to evaluate the interaction effect between antenna far-field EM radiation and human similar tissue. The measured results have the good agreement with the simulated results.

並列關鍵字

SAR ； Near-field ； Far-field ； Antenna ； and EM Propagation

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