A Study on Antenna Design Method for 5 GHz Band Portable Terminals

新一代的移动的通信系统正在全世界范围内研究在5 GHz频带上支持多媒体业务。相应的便携式终端将被用在诸如具有无线调制解调器的膝上型个人计算机（PC）的各种各样的情况中。由于用户在使用时通常将PC靠近他们的脸，因此在天线设计中必须考虑天线安装的PC和人体之间的电磁（EM）相互作用。然而，传统的计算机工具，如时域有限差分法（FDTD）是很难适用于在5 GHz频段的天线设计，因为它的计算负担很重。为了解决这个问题，我们已经应用了多重网格FDTD方法的5 GHz频段的天线设计。在多重网格FDTD方法中，建立了由粗网格和细网格组成的两个区域。粗网格用于模拟整个结构，细网格用于模拟天线和体积。 ...更多信息 在人体内，电磁波吸收最高的地方。这样的布置是基于以下事实：在5GHz频带处趋肤深度非常小，使得EM场将仅穿透到浅表组织中。利用多重网格FDTD方法，我们优化了一个安装在PC机上的5 GHz频段的结构。结果表明，人体效应主要是阻挡天线向体侧的辐射。它对天线输入阻抗的影响是微不足道的。另一方面，由于PC也是天线中电流流动的一部分，因此人体中最高的EM吸收区域位于最靠近天线或PC角落的部分。为了得到一个标准的复杂性，在5 GHz频段的天线设计中所需的人体模型，我们已经调查了一个基于解剖学的人体模型和几个高度简化的人体模型。通过比较多重网格FDTD计算的天线输入阻抗，辐射方向图和人体吸收的功率，我们已经澄清了所需的人体复杂性，考虑在该频段的电磁相互作用。本研究的一部分结果已发表在一份参考期刊上，并在国际研讨会上发表。少

A new generation of mobile communication systems is being worldwide investigated at 5 GHz band for supporting multimedia services. The corresponding portable terminals will be used in a great variety of situations such as a laptop personal computer (PC) with a wireless modem. Since users generally have the PC next to their face in use, it is essential to consider electromagnetic (EM) interaction between the antenna mounted PC and human body in the antenna design. However, conventional computer tools such as the finite-difference time-domain (FDTD) method are difficult to apply for the antenna design at 5 GHz band because of its heavy computation burden. To cope with this problem, we have applied a multi-grid FDTD method for the 5 GHz band antenna design. In the multi-grid FDTD method, two regions consisting of the coarse-grid region and fine-grid region were created. The coarse grids were used to model the entire structure, and the fine grids were used to model the antenna and the volu … More me in the human body where the highest EM absorption occurs. Such an arrangement was based on the fact that the skin depth is very small at 5 GHz band so that the EM fields will only penetrate into the superficial tissue. Using the multi-grid FDTD method, we have optimized the structure of a monopole mounted PC at 5 GHz band. The results indicated that the human body effect was mainly blocking the antenna radiation towards the body side. Its influence on the antenna input impedance was insignificant. On the other hand, since the PC was also a part of the antenna where currents flow, the highest EM absorption area in the human body was in the part closest to the antenna or the PC corner. To derive a criterion for the complexity of human body model required in the antenna design at 5 GHz band, we have investigated an anatomically based human body model and several highly simplified human body models. Via comparing the multi-grid FDTD calculated antenna input impedance, radiation pattern and power absorbed by the human body we have clarified the required human body complexity for considering the EM interaction at this frequency band. One part of the results in this study has been published on a referred journal and presented at international symposiums. Less