利用FDTD方法比较手提电话天线的方向图,输入阻抗及人头部的？…

本文给出了利用ＦＤＴＤ电磁模拟方法对常用的五种个人通信手提电话的天线和人头部组织相互作用的比较研究。在研究中考虑的蜂窝通信手提电话常用的天线种类为单极子，偶极子和倒Ｆ天线。不均匀的实际人头模型被用于预测天线特性 对操作作者耦合的电磁效应，天线在人头部的潜在危险影响是用１Ｗ辐射功率在人组织产生的比吸收率来评估。     

红外端口窜红近距离通信

红外端口窜红近距离通信从通信的观点看,利用ＩｒＤＡ（红外数据采集）端口,便携式计算机可以连接手提电话并用作为传真机和调制解调器。ＰＣ和手提电话的地址本可以同步更新。当然还有ＰＤＡ,数字相机也可以同样的方式连接在这一环路中。这样数字相机就可利用ＩｒＤＡ...     

新型天线技术与电波传播特性研究

本文介绍了我们近年来在电磁带隙结构、多（单）天线系统、多（单）天线信道特性方面的研究工作和主要研究结果．主要包括：电磁带隙结构小型化、宽带化技术，小型化、多频带／宽频带天线单元，适用于多输入多输出通信系统的手机多天线系统，室内外环境下的多（单）天线系统的信道特性等方面的主要研究结果。     

电磁计算在雷达设计中的应用及需求分析

随着计算电磁学和计算机技术的迅速发展,电磁计算在雷达设计中扮演着举足轻重的角色.本文分析了电磁计算在雷达设计中的应用,包括雷达天线设计、馈线及微波网络设计、天线罩设计以及复杂电磁环境雷达天线性能评估,并介绍了有限元法（finite element method,FEM）、矩量法（method of moment,MoM）和时域有限差分（finite-difference time-domain,FDTD）法三种常用的全波电磁仿真计算方法以及高频近似算法,最后讨论了雷达技术发展对电磁计算的新需求.     

水下拖曳天线横向振动诱发的电磁噪声研究

水下磁场与电场天线横向振动诱发的电磁噪声在长波通信电磁噪声中占主导地位,直接影响收信深度和通信质量.针对此问题,建立了天线的横向振动模型,导出了天线的随机振动响应,分析了磁场与电场天线横向振动诱发电磁噪声的产生机理及特性,并给出电磁噪声的仿真结果和分析.研究结果为拖曳天线设计和水下电磁噪声深入研究提供了理论基础.     

能降低辐射的超材料天线

超材料是采用传统材料（如电路板和铜箔）制成的复合结构，具有市场亟需的独特磁特性。超材料天线有别于传统的”物理”天线，能够减弱天线结构附近的电磁场和电流，从而使手机大大减少对人头部附近的射频能源辐射，并且提供高性能，免受用户手部和头部干扰的影响。此外，手机制造商可以通过一份CAD文件直接在传统的印刷电路板（PCB）上“印刷”出超材料天线。     

一种近场调制型芯片天线特性的研究

近场直接天线调制（NFDAM）技术是新近出现的一种高安全性宽频带调制技术,它改善了传统调制技术中系统结构复杂、通信的安全性差等特点。应用NFDAM 技术所设计的近场调制型芯片天线能够发射一种与方向相关的信号,所辐射的远场信号由于天线近场电磁边界条件的改变而进行调制,本论文通过在主天线附近放置具有开关的反射器的方式实现改变天线辐射特性,开关的闭合和断开的控制改变反射器的反射特性,从而形成不同组合的天线形式。本文设计完成了一个工作在60GHz 的最简化近场调制型芯片天线,利用CST 电磁仿真软件和MATLAB 软件对天线远场的辐射特性进行了仿真和分析,对近场调制型芯片天线的调制作用及通信的安全性进行了验证。     

手机的耳机辐射到底有多大

４月５日,中央电视台报道英国某组织一测试表明：手机附加耳机在通话过程中的电磁波辐射量,比手机天线处大３倍。究竟情况如何？作为多年从事通信标准研究与测试的专业实验室,我们对此进行了认真测试。我们对市场上销售的十几个型号的手机,处在最大发射功率（２Ｗ）时天线处的近场电磁辐射量和在加耳机后耳机处的近场电磁辐射量,进行了详细测试。采用高精度适应ＧＳＭ手机脉冲辐射方式的仪表,并采用峰值保持测试方法,以搜取最大辐射值。测试结果表明：耳机处的电磁辐射量,比手机天线处的辐射量小两个数量级（小１００倍以上）。也就是说,使用耳机通话比直接使用手机通话,头部受到的辐射要小得多。手机通信是通过电磁波的辐射来实现的。手机天线及天线与射频电路的连接,包括天线的尺寸,阻抗特性和材料在设计上肯定是为获得最佳辐射。应该说天线处无疑是最大辐射点。而耳机在手机的电路连接上处于音频电路部分,与射频电路在设计和工艺组织安排上有很好的隔离措施（不然手机无法正常工作）,而且耳机线的长度和材料也不适宜取得高效辐射量。因此耳机处辐射量比手机天线处辐射量更大的说法没有道理,也不符合实际情况。目前国际上通行的手机辐射对人体的影响是以“比吸收率”来定义的,主要表现...     

无线通信智能天线技术的未来发展趋势

1、引言 智能天线原名自适应天线阵列（AAA，Adaptive Antenna Array）。最初的智能天线技术主要用于雷达、抗干扰通信、定位及军事通信方面等，完成空间滤波和定位功能。近年来，随着移动通信的发展以及对移动通信电波传播、组网技术、天线理论等方面的研究逐渐深入，智能天线开始用于具有复杂电波传播环境下的移动通信。为此，移动通信研究者给应用于移动通信的自适应天线阵起了一个较吸引人的名字——智能天线（英文名为Smart Antenna或Intelligent Antenna）。     

人体受到电磁辐射的仿真研究

基于可变网络的时域有限差分法,仿真了暴露于900MHz移动通信基站天线远区场中的人体和移动电话天线近区场中的人体头部电磁模型中产生的比吸收率分布,分析了基站天线和手机天线辐射对人体的影响。以理想点源天线作为基站天线,在人体正前方入射频率为900MHz的正弦平面波,仿真结果显示,人体在基站天线照射下的平均SAR值符合国际卫生部标准;以900MHz单频PIAF天线作为手机天线置于高仿真人体头部1cm处,仿真结果与环保标准比较,人体头部受到的照射剂量远低于安全标准。     

Experimental and FDTD-computed radiation patterns of cellulartelephones held in slanted operational conditions

The objective of this paper is to investigate, numerically and experimentally, the radiation patterns of various commercial cellular telephones held in a realistically slanted position relative to the head, to understand the performance of such devices for normal use conditions. The investigation has been performed with and without the human head model at an angle of 30° with respect to the vertical. To avoid the stair-step modeling of the cellular telephone for the finite-difference time-domain (FDTD) formulation, the head has instead been tilted forward by 30° and a transformation of coordinates in the FDTD calculation has been used to obtain the desired vertical and horizontal polarizations. We show that the FDTD method gives results that are in good agreement with measurements, both for shape and gain of the radiation patterns, for all of the considered mobile telephones that use several types of antennas. Generally, a decrease of the cellular telephone gain for the vertical component of the field has been observed as compared to the vertical configuration of the telephone and also a decrease in gain is obtained when the phone is held against the human head. Furthermore, it is shown that the FDTD method is capable of providing fairly accurate results even for radiation patterns at a slanted angle and modeling of realistic cellular telephones     

Spherical outdoor to indoor power spectrum model at the mobile terminal

Mobile terminals are often used indoor with the base station outdoors. At the mobile terminal the major part of the signal energy comes through openings in the building such as windows. Typically, only one of the sides in a room has windows, and seldom does a room have windows on all sides. Hence, the dominating signal can be expected to arrive at the mobile terminal from a narrow range of angles. Mobile terminal antennas used next to the head in the speaking position will be directional due to the fact that part of the radiation pattern facing the head will be attenuated and reflected. Having a directive antenna in a directive environment, the performance will depend on the orientation of the antenna in the radio environment. A new statistical spherical outdoor to indoor power spectrum model has been proposed to be able to calculate the directional performance of mobile terminals with a single or multiple antennas. The model consists of a major scattering area in one direction and more uniformly distributed minor scatterers in the other directions. A verification of the proposed model was performed and 60 data sets of spherical power spectrum measurements were collected in a typical urban environment. Using the new model, the directional performance of mobile terminal antennas including a human operator has been investigated through directional mean effective gain, branch power ratio, and correlation calculations using spherical radiation pattern measurements of a mobile terminal including the effect of 42 different persons. The accuracy of the calculated values was verified by directly measured values using 200 persons walking with the mobile terminal in the same office-like environments as where the spherical power spectrum measurements were performed.     

EM interaction of handset antennas and a human in personalcommunications

In personal communications, the electromagnetic interaction between handset-mounted antennas and the nearby biological tissue is a key consideration. This paper presents a thorough investigation of this antenna-tissue interaction using the finite-difference time-domain (FDTD) electromagnetic simulation approach with detailed models of real-life antennas on a transceiver handset. The monopole, side-mounted planar inverted F, top-mounted bent inverted F, and back-mounted planar inverted F antennas are selected as representative examples of external and internal configurations. Detailed models of the human head and hand are implemented to investigate the effects of the tissue location and physical model on the antenna performance. Experimental results are provided which support the computationally obtained conclusions. The specific absorption rate (SAR) in the tissue is examined for several different antenna/handset configurations. It is found that for a head-handset separation of 2 cm, the SAR in the head has a peak value between 0.9 and 3.8 mW/g and an average value between 0.06 and 0.10 mW/g for 1 W of power delivered to the antenna. Additionally, the head and hand absorb between 48 and 68% of the power delivered to the antenna     

Numerical analysis of bodyworn UHF antenna systems

Bodyworn antennas are found in a wide range of medical, military and personal communication applications, yet reliable communication from the surface of the human body still presents a range of engineering challenges. At UHF and microwave frequencies, bodyworn antennas can suffer from reduced efficiency due to electromagnetic absorption in tissue, radiation pattern fragmentation and variations in feed-point impedance. The significance and nature of these effects are system specific and depend on the operating frequency, propagation environment and physical constraints on the antenna itself. This paper describes how numerical electromagnetic modelling techniques such as FDTD (finite-difference time-domain) can be used in the design of bodyworn antennas. Examples are presented for 418 MHz, 916·5 MHz and 2·45 GHz, in the context of both biomedical signalling and wireless personal-area networking applications such as the Bluetooth^TM wireless technology     

Performance of shorted microstrip patch antennas for mobilecommunications handsets at 1800 MHz

We have investigated the application of two different types of novel shorted-patch antennas for mobile communications handsets at 1800 MHz. A single shorted-patch and a stacked shorted-patch antenna offering improved bandwidth are compared with data for a λ/4 monopole. The finite-difference time-domain (FDTD) technique was used to calculate antenna characteristics such as impedance and radiation patterns for two cases: on a handset and on a handset near a (2.5-mm voxel) heterogeneous head model in an actual position of phone use. We also obtained specific absorption rate (SAR) distributions and calculated the spatial peak 1-g SAR values. In addition, the effect on SAR and antenna characteristics of including a block model of the hand was assessed. Similar performance is achieved from the single or stacked shorted-patch antenna with the latter providing greater bandwidth, 8.2% versus 9.4% with the head and hand included. Both antennas reduce the l-g spatial peak SAR value in the head by 70% relative to the monopole. The presence of the hand reduces the efficiency of all three antenna types by approximately 10%     

Electromagnetic absorption in the human head from experimental6-GHz handheld transceivers

We have used a new millimeter-resolution MRI-based model of the human body to calculate the electromagnetic absorption in the head and neck for three experimental Yagi antennas suggested for handheld transceivers of a proposed 6-GHz personal communication network (PCN) system. The SAR distributions are obtained with a resolution of 1.974×1.974×1.5 mm for transceivers that are held against the ears and tilted forward by 33°. The finite-difference time-domain technique is used to calculate the EM fields and SARs for the transceiver, antenna, and head and neck coupled region that is divided into 158×84×188 or nearly 2.5 million cells. The highlights of the numerical calculations are verified by means of a head-shaped experimental model made of tissue-equivalent materials simulating the electrical properties (ϵ_r,σ) of the skull, brain, muscle, eyes, and ears developed for use at 6 GHz. Because of the proximity to the antenna, the highest SARs are obtained for the upper part of the ear. For a planned radiated power of 0.6 W, the peak SARs averaged over any 1 g of tissue defined as a tissue volume in the shape of a cube are on the order of 0.5-1.0 W/kg for two of the proposed antennas and considerably higher (2.06 W/kg) for the third antenna using a narrower off-axis reflector. Low SARs for the first two antennas are likely due to the shielding provided by the relatively wider strip reflector plates used for these antennas     

Cellular-Phone and Hearing-Aid Interaction: An Antenna Solution

With the introduction of digital cellular phones, hearing-aid users have experienced a severe buzzing noise caused by the interaction between digital cellular phones and hearing aids. The cellular-phone industry, the hearing-aid industry, and consumers have been seeking a solution for the interference issue. Efforts reported in the literature have focused on measurements, modeling, and evaluation of interference and RF emission, but not on methods to solve the problem. In this paper, we focus on the causes of the interference and an understanding of the problem. We also present a method to reduce near-field electromagnetic energy around a cellular phone, mitigating the interference between cellular phones and hearing aids. The theoretical investigation of both the radiation mechanisms and fundamental limits on antennas suggested that a low-g antenna, such as an ultra-wideband antenna, could reduce the near-field intensity. Simulations and measurements were performed at 900 and 1880 MHz, using both low- and high-Q test antennas mounted on a mock cellular phone. The results showed that the peak electric and magnetic near-field strengths of the low-g test antenna were lower than those of a high-Q test antenna by at least 5 dBV/m and 4 dBA/m, respectively. The improvement in the near-field performance for the low-g antenna was without any sacrifice in far-field performance. Furthermore, in the presence of a human head, the simulation results showed that the radiation efficiency of the low-Q test antenna was better than that of the high-Q test antenna.     

The cellular phone scare

The scare about cellular phones causing brain cancer is examined in the light of what is known about: effects of RF radiation on human beings. The concern focused on the portable cellular phones that can be slipped into a pocket or purse, because their antennas lie right alongside a user's head. Standards for electromagnetic (EM) radiation exposure are discussed, and research results to date on the effects of EM radiation is summarized. Changes to phones that might reduce exposure and the potential impact of public fear on the market for cellular phones are considered     

介质覆盖矩形微带天线的理论与实验

本文研究了介质覆盖矩形微带天线的特性，精确的谱域全波分析方法被扩展到这类天线的分析中，给出了理论计算公式，探讨了介质覆盖层和对矩形微带天线的驻波比的影响，实验结果证实了理论计算的正确性。     

Radiation Pattern of Wearable Antennas: A Statistical Analysis of the Influence of the Human Body

This paper explores a statistical approach for modelling antennas?? behaviour in the vicinity of the human body. The statistics of radiation patterns, i.e., average and standard deviation, have been calculated for Uniform and Rayleigh distance Distributions of the antenna to the body. The coupling between the body and the antenna, and the reduction of antenna efficiency, lead to a distortion of the radiation pattern, which depends on the distance as well as on the location on the body. A patch antenna operating at 2.45?GHz, on the head, chest, arm, and leg was simulated in computer simulation technology (CST), using a voxel model. Results show that the relative change of the average radiation pattern for an antenna located on the chest can reach 24?%. The study was complemented with measurements, showing that, in the area of interest for on-body communications, an average difference between CST and measurements of 0.9?dB is found which can be considered very good.