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

支持多媒体业务的5 GHz频段的新一代移动通信系统正在全球范围内得到研究。相应的便携式终端将用于各种情况，例如具有无线调制解调器的膝上型个人计算机(PC)。由于用户在使用时通常将PC放在他们的脸旁边，因此在天线设计中考虑安装在天线上的PC与人体之间的电磁(EM)相互作用是至关重要的。然而，传统的计算工具如时域有限差分法(FDTD)由于计算量大，很难应用于5 GHz频段的天线设计。为了解决这一问题，我们将多网格FDTD方法应用于5 GHz频段天线的设计。在多网格FDTD方法中，创建了粗网格和细网格两个区域。用粗网格模拟整个结构，用细网格模拟天线和Volu…更多的我在人体内，那里发生了最高的EM吸收。这样的安排是基于这样一个事实，即在5 GHz频段皮肤深度很小，因此电磁场只会穿透到浅层组织。利用多网格FDTD方法，对5 GHz频段单极子PC的结构进行了优化设计。结果表明，人体效应主要是阻挡天线向人体一侧的辐射。它对天线输入阻抗的影响不大。另一方面，由于PC也是天线中电流流动的一部分，因此人体对电磁的吸收最高的区域是离天线或PC角最近的部分。为了推导出5 GHz频段天线设计中所需的人体模型的复杂程度，我们研究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，明确了在该频段考虑电磁干扰所需的人体复杂度。这项研究的一部分成果已发表在参考期刊上，并在国际研讨会上发表。较少

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