超长波气球天线

本文根据我国超长波电台建设和运行的经验，对超长波气球天线的电气参数作简明的表述，为超长波电台工程设计和技术管理人员提供了一个实用的计算方法。     

倒锥型长波发射天线研究

长波发射天线一般可以看作是顶加载单极天线，常见的天线形式有伞形天线及倒锥型天线。本文以倒锥型天线中最常见的四塔倒锥天线为例，分析了其组成及设计过程中的关键参数选取，并通过数值计算方法给出了一个具体方案；在该方案的基础上，进行了缩比模型试验， 验证了天线设计的准确性，掌握了该型天线的特点和设计方法。     

基于中波发射系统的多业务同播技术应用

本文利用中波自立塔、中波拉线塔等不同中波发射天线作为调频广播、电视天线的架设载体,依托中波转播台现有完善的基础设施和技术体系,发挥中波发射塔坚固的机械性能和相对海拔高度的电气性能两个优势,在不影响中波覆盖效果,同时确保调频、数字电视发射质量的前提下,进行了中波、调频、数字电视的共塔发射,为调频广播和数字电视的全省覆盖提供了有力支撑,为传统中波发射的继承与转型更好地步入融媒体时代奠定基础。     

BPL授时发播系统天线物理特性的研究

从能量传递和输出波形形成的角度,讨论了长波授时天线-四塔顶荷倒锥天线同电子管发射机和固态发射机的关系。在长波电子管发射机的设计和使用中,合理地选择发射机末级输出网络元件和天线电气参数,保证输出波形符合要求,天线获得最大输出功率。在使用固态发射机时,使天线网络满足能量从半周发生器到天线的最佳传递,并获得所需要的电流波形。进一步讨论了长波授时天线的不足和固态发射机对天线的要求,将天线有效高度与天线几何高度的比值提高到0.7,可使效率带宽积达到最大值。     

战损对雷达天线作战性能的影响

现代电子战中,电磁权的争夺是决定战争胜负的关键因素。通过仿真分析天线在不同战损模式下电气性能的变化情况,讨论了天线受损后对作战性能的影响,对战场抢修具有一定的参考价值。     

毫米波同轴连接器低反射绝缘支撑的设计

绝缘支撑的结构对毫米波同轴连接器的电压驻波比性能有很大影响,介绍了利用介质界面上能量全折射原理设计的绝缘支撑结构,这种绝缘支撑结构可以减少介质界面上的能量反射。毫米波同轴电缆组件的测试结果表明,该绝缘支撑结构可以提高毫米波同轴电缆组件的电压驻波比性能。     

MEMS开关供电线及过孔对微带贴片天线性能的影响

采用数值分析研究了微电子机械系统(MEMS)开关直流供电线及接地过孔对微带贴片天线性能的影响.研究表明,当MEMS开关应用于天线辐射部分时,MEMS开关的直流供电线和接地过孔对天线的匹配频带有较大影响,而且金属过孔的影响较直流供电线的影响更大.因此若采用金属条等效MEMS开关研究可重构天线时,应适当调整微带贴片天线的电...     

改进加顶结构的甚低频发信天线阻抗特性分析

针对甚低频发射天线输入电抗高、输入电阻小而导致的天线Q值高、带宽窄、输入功率受限、天线系统效率低等问题,研究了伞型和T型甚低频发射天线的顶负载在不同电气连接方式下的天线输入阻抗,提出在不改变天线总体结构的情况下,改变顶负载电气连接方式可优化天线的输入阻抗的方法.计算结果和理论分析均表明,优化后的天线顶负载连接方式可降低甚低频发射天线的输入容抗、提高天线的输入电阻,从而可提高天线系统效率和功率容量、增加天线带宽,对改善甚低频发射天线性能和提高天线电气工作安全性具有重要意义.     

甚低频十三塔天线电气性能的研究

为了研究影响甚低频天线辐射效率的辐射电阻和地损耗电阻,采用数值仿真与差值相结合的方法,对某双副十三塔甚低频伞形天线中的一副天线进行了数值建模,通过与天线实际测量值对比,验证了天线建模的正确性,研究了天线边塔接地前后天线辐射电阻的变化。在简化该模型的基础上,探讨了天线工作在不同频率下,辐射状地网单圈汇流环位置和汇流环数目对地损耗电阻的影响。     

机械结构对阵列天线交叉极化特性影响的研究

以全球微波接入互操作系统（WiMax）增补频段上的四单元宽带贴片天线阵列为研究对象,通过分析计算和实验测量,详细研究了机械支撑结构对宽带微带贴片天线阵列的交叉极化性能影响。分析及测试结果表明,介质支撑结构的阵列天线具有更好的交叉极化特性。文章的结论对改善贴片阵列天线的极化纯度、优化天线单元的机械支撑结构具有实际意义。     

MF AM folded monopole characteristics

Folded monopole antennas have been used for many years in medium frequency amplitude modulation broadcast applications. These antennas offer a grounded radiating structure with a height approximating a quarter wavelength. Folded monopoles have been studied exhaustively during a previous effort in an attempt to characterize the input impedance and directivity characteristics as a function of monopole height. As a result it was observed that several impedance regions can be achieved as a function of antenna height and cage diameter: Some of these regions permit a bandwidth operation sufficiently broad to support a high fidelity response for analog or digital transmissions. This type of antenna can be useful at different heights including a self matching region at the standard 50 ohms impedance. By choosing the appropriate antenna physical dimensions, antenna tuners can be avoided and thus it increases efficiency. Measurements have been made on a full scale 72 meter tower with a 6 wire cage in order to validate the calculated antenna input impedance and directivity. The cage and supporting mast make up the equivalent of a transmission line. For this reason different standard triangular towers were analyzed in order to determine their effect on the input impedance. Tower effective radius is determined taking into account the tower width and the tower leg diameter. At the same time, a minimum antenna height with maximum efficiency has been analyzed to solve the hard problem for installations at places where antenna height is a challenge for the designer.     

一种多塔中波天线的设计与仿真

占地面积大、征地成本高、场地限制不好布设等问题一直严重制约中波天线的建设。 为了减少中波天线占地面积,提高铁塔的利用率,对天线布局和天馈网络进行优化设计,研究双频共塔匹配网络、阻塞网络和共址多塔天线辐射特性,给出三塔六频率的解决方案。最后,通过仿真论证,给出对应的网络、天线几何结构和辐射性能参数。     

卫星地面站天线塔不均匀沉降影响及数据分析

通过对多个全动卫星地面站天线塔不均匀沉降的长期连续测量,得出了其不均匀沉降的大小及变化趋势。分析了不均匀沉降对天线测角精度的影响,研究了不均匀沉降的补偿方法。中小型天线一般自身设置有机械调平装置,可进行一定量的调整补偿。更为普遍的补偿方法是用数学模型来修正不均匀沉降带来的测量误差,大天线和中小天线都适用。工程中这些方法都已应用,效果良好,对提高天线塔建设效费比有重要意义。     

Measured properties of bare and insulated antennas in sand

An experimental system for measuring the electrical properties of antennas embedded in moist sand is described. Measured antenna input admittances for bare linear and circular-loop antennas in sand are compared with theory. Insulated linear and circular-loop antennas with the dielectric constant of the insulation comparable to that of the surrounding medium are considered. Measured input admittances of linear antennas with different insulation sizes and dielectric constants are used to illustrate the effect of the insulation on the admittance. Measured input admittances for the spherically insulated circular-loop antenna are compared with theory and are found to be in good agreement.     

Ultra-Wideband Electrostrictive Mechanical Antenna

Mechanical antennas based on piezoelectric materials can effectively reduce the size of long wave antennas down to 1/1000 of the wavelength (from km scale to mm level). However, the narrow bandwidth and weak field intensity seriously restrict its practical applications in transmission distance and channel capacity. Here, a mechanical antenna-based electrostrictive effect of relaxor ferroelectric ceramic (PMN-PT) is proposed to improve radiation capacity and achieve ultra-wideband characteristics (10 kHz–1 MHz). Due to the ultra-high dielectric constant at working temperature and the relationship between the strain and applied field intensity, the proposed antenna gets rid of the dependence on the poled materials and exhibits excellent communication properties beyond traditional mechanical antennas, which are experimentally demonstrated by a practical wireless communication system. Only using a single proposed mechanical antenna with 8 mm diameter and 3 mm thickness, the effective communication with a transmission distance of 200 m can be realized. This design offers a promising way of constructing mechanical antennas for long-wave communication.     

Controversy over cellular mobile-telecommunication base-station-antenna installations

The two most compelling issues that cause cellular-telephone towers to be so controversial are the public health and aesthetic concerns. People love the wireless convenience and instant connectivity, but no one likes the antenna tower that enables it. The siting of the cellular mobile telephone towers remains a divisive issue, worldwide. Some concerns stem from a lack of personal freedom of choice, in being subjected to the radio-frequency radiation emitted by the tower antennas and its potential health effects. Others have raised concerns about aesthetics and property devaluation. Cell-phone towers with graceful and artistic designs that are tastefully constructed would go a long way toward calming the fears of those who abhor the presence of ugly-cell phone towers looming over homes and businesses. It would be propitious both for the wireless telecommunications industry and the local planning and zoning commissions to collaborate in creating innovative solutions to the design, siting, and installation of cellular telecommunication base-station towers.     

Design optimization of interstitial antennas

To improve the performance of interstitial antennas for microwave hyperthermia, parameters such as the uniformity of the heating pattern, the depth of penetration, and the impedance matching properties must be optimized. We examined analytically and experimentally the radiation characteristics of multisection insulated antennas in conductive tissue. The effects of varying the diameters and lengths of the center conductors in the various sections of the antenna and the diameter and type of the insulation on the electromagnetic power deposition pattern and input impedance characteristics were examined. A new approximate numerical model which calculates the current distribution and the radiation characteristics of multisection insulated antennas was developed. The numerical predictions were verified in a qualitative way experimentally by mapping the various near- and far-field components of these antennas. Based on the obtained results, design tradeoffs are identified and quantified, and guidelines for optimum designs are specified. In particular, it is shown that an insulation-to-center-conductor diameter ratio between 1.5 to 2.0 is optimum for a uniform Teflon insulation, and that a multisection arrangement with the thinnest insulation near the antenna tip has superior performance compared with the uniform insulation or other multisection designs.     

The Millimeter Wave Radiation of a Traveling Wave Sinusoidal Wire Antenna

In this paper, investigation of radiation properties of the traveling-wave sinusoidal wire antennas is extended to the millimeter-wave frequencies (Ka-band) for the antennas whose geometrical dimensions vary in a wide range. Far-field patterns and S-parameters of composed three antenna sets were measured. A mathematical model was constructed for the structure and a MATLAB code based on this theoretical approach was written to calculate patterns, phase and attenuation constants of all investigated antennas. Frequency characteristics and the relation of antenna dimensions with wave parameters were investigated. Measured and calculated patterns were also compared with the constructed far-field patterns obtained by MoM (method of moments) and the MoM current distributions were used to explain the loss mechanisms of antennas. A directive, undistorted and smooth radiation can be achieved only choosing small undulated antennas whose peak-to-peak amplitude to period ratio κ is smaller than 0.4 (κ?<?0.4). It is shown that wavelength of broadside radiation is not equal to antenna period for all antennas, except for very small undulated antennas (κ?<?0.2). This antenna type can be used as a frequency-scan antenna for millimeter wave radars.     

An antenna coupling model for cross-polarized antennas for radarelectromagnetic compatibility analysis

A statistically based antenna coupling model for linearly polarized, cross-polarized antennas is presented. The antenna gains are defined as random variables. It is assumed that the probability density functions of the gains can be estimated from the antenna patterns. From the density functions, a method is developed to calculate the combined density function. This method accounts for angular motion that the antennas would experience if they were mounted on ships subject to roll. The probability of interference is defined, and a method is developed to calculate it based on the combined density function. The results of this analysis for two selected antennas are presented, and the limits of applicability, are discussed