Characterization of antennas for personal wireless communications applications

The advancement of antenna technology in personal wireless communication systems has been encouraged by the increasingly stringent demands placed upon these systems to provide low-power and highly reliable information transfer. The antenna designer must not only consider the cost, manufacturability, compactness, and system integrability of the radiator but also generate a product which satisfies rigid specifications concerning return loss, bandwidth, and gain while operating in a complex radiating environment. Successful, cost-effective approaches to the design of antennas for communication devices rely upon the implementation of sophisticated analysis tools, such as the finite-difference time-domain (FDTD) method, capable of predicting the electromagnetic behavior of complicated topologies. In this work, the behavior of planar inverted F, monopole, and loop antennas is investigated using tools based upon the FDTD approach. Such factors as the effects of the conducting chassis, plastic casing, and biological tissue on the antenna performance are investigated. Experimental measurements are used to validate the results obtained from computations and to provide further insight into the behavior of the different geometries. The use of antenna diversity to reduce the effects of multipath fading is discussed, and several examples of antenna diversity configurations are provided.     

背腔式微带天线电磁散射分析的FEM/PO-PTD方法

将一种新的混合方法-FEM/PO-PTD方法，应用于分析计算背腔式微带天线的电磁散射特性。通过无穷大接地导体平面上矩形背腔式微带天线的RCS计算，验证了该方法的正确性。在此基础上，计算了两组有限尺寸金属载体上背腔式微带天线的RCS曲线，理论分析与计算结果表明，该混合方法具有计算机内存需求少、计算时间短等优点。     

具有和不具有空气隙的圆环微带天线输入阻抗的理论分析

提供了圆秆微带无线（具有和不具有空气隙）在同轴线馈电情况下输入阻抗的理论分析。推导出未知贴片电流的积分方程。整个推导过程是在汉克尔变换域内进行，对于地片电流引人一套基函数，应用伽略金法及Ｐａｒｓｅｖａｌ关系，推导出矩阵方程，由此可以解出贴片电流，推导出输入阻抗的表达式，并包括了表面波的影响。给出了当空气隙宽度为不同数值时输入阻抗的计算结果。由计算结果表明：当空气隙宽度增加时，谐振频率和带宽均增加。     

Improved formulae for the resonant frequencies of triangular microstrip patch antennas

In this article, an improved formula for the effective side length (a _eff) of the equilateral triangular patch antenna is presented. The computed resonant frequencies for the first five modes, using this formula, are compared with the available experimental and theoretical results in the literature. It is shown that the proposed formula has better accuracy than other available expressions. Moreover, the 30°–60°–90° and 30°–30°–120° triangular patch antennas are studied. Specifically, improved formulae for the effective dielectric constant of these patches are derived.     

世博特殊场景下小型化智能天线的应用

智能天线是TD-SCDMA系统中使用的一项关键技术,但是由于体积大,线缆多,使用中具有很大的局限性。本文结合世博实际应用,提出了一种小型化智能天线解决方案,并通过实际测试结果证明其实用性。     

Microstrip dipoles on electrically thick substrates

Certain basic radiation properties of microstrip dipoles on electrically thick substrates are investigated, and a comparison is made with the case of dipoles printed on a dielectric half-space. It is concluded that the microstrip dipole radiation properties become sensitive to substrate loss as the substrate thickness increases, with the half-space properties obtained for an adequate amount of loss. Asymptotic formulas for radiated power and efficiency are given for both the thick substrate and half-space problems, showing the behavior with increasing dielectric constant. The method of moments is used to extend the analysis to center-fed strip dipoles, and a method of improving both the efficiency and gain of a printed antenna by using a superstrate layer is discussed.This research was supported by NSF Research Grant ESC 82-15408 and U.S. Army Research Grant DAAG-29-83-K-0067.     

毛细管气相色谱分流进样技术研究

研究出一种改进的毛细管分流进样器，设计了一种新型螺旋进样内衬管。使分流进样的重复精度有显著提高，沸点歧视效应减小，色谱峰尾尖锐，使毛细管色谱柱的高分离效能得以充分发挥。对４种常用的进样内衬进行了考察，得到了有重要实用意义的结果，并从理论上解释了与传统观点相悖的实验现象，深化了对分流进样动态过程的理解。     

Efficiency of quasi-optical couplers

Millimeter-wave devices are often coupled to radiation by means of a feed antenna placed at the focus of a primary lens or mirror, a technique known as quasioptical coupling. A general expression for the efficiency of such a coupler is derived.The efficiency of such a coupler depends on the relationship of the feed antenna pattern to the numerical aperture of the primary lens. An approximate general rule for coupler design is obtained. This rule is as follows. Let _o be the angle between the direction in which the feed pattern is maximum and the direction in which the pattern intensity has one-half its maximum value. Then the optimum numerical aperture of the primary lens is approximately sin (1.67 _o). The effects of focussing errors and lens aberrations can also be calculated by this technique.     

一种分析微带贴片天线的辛时域有限差分方法

文中研究了在时间上采用5级4阶差分、空间上采用4阶差分的高阶辛时域有限差9（SFDTD）数值方法。给出其三维差分公式．将吸收边界条件应用于微带天线的计算中，计算了微带贴片天线的回波损耗及输入阻抗等．计算结果证明，该方法的精确性和正确性．     

一种能产生针状波束和扇形波束的面天线

本文设计出了一种既能产生针状波束又能产生扇形波束的新型面天线,该天线的增益和方向图通过理论计算计算出来。本文设计实例中的面天线的针状波束的E、H平面的半功率宽度分别为2.320、2.240,而扇形波束的E、H平面的半功率宽度分别为2.010,6.40。