交流架空电力线路对中波广播台发射台站的影响研究

基于广播电视发射台受架空电力线路影响的问题频繁提出,广播电视规划院联合多个单位开展《交流架空电力线对中短波发射台干扰的分析研究》专题研究.项目组通过选择电磁计算方法、确定交流架空电力线无源影响的分析模型、特定距离下对中波发射天线无源影响典型情况的系统仿真,总结一般规律,并利用构建的缩比模型,进行了定性验证测试,研究了110kV、220kV、330kV和500kV高压等级的架空电力线路对中波和短波广播发射台天线的无源影响.本文简要介绍500kV架空电力线路对中波广播发射台单塔、双塔、四塔和八塔广播发射天线的典型影响结果.利用本项目的分析方法和模型,结合实际架空电力线路距离、走向、地形地势,已应用于为广播发射台搬迁规划选址提供理论依据.建议在保证广播电视和国家电力网两方面健康发展的基础上进一步研究防护距离和防护原则.     

特高压输电线路对中波导航天线影响的仿真分析

针对航空近程导航系统受到复杂电磁环境干扰的实际问题,研究特高压电力输送设施对中波导航系统造成的无源干扰影响.使用电磁学矩量法仿真分析软件,建立特高压输电设施模型以及中波天线模型.采用控制变量的方法,仿真特高压输电设施无源时,电塔数目、电塔与天线的距离对中波天线方向图的影响.另外仿真了中波天线在不同频率时受特高压输电设施...     

高压输电线路对中波导航台无源干扰的研究

航空中波无线电导航台站的周边建筑和电磁环境均有相关要求,随着城市的发展,中波导航台站周边环境存在着较大的变化,经过前期的调研发现,中波导航台站周边存在的无源干扰中高压输电线路占据其中的主要部分。通过对电磁学计算方法的研究,选用矩量法作为研究的数值方法,建立高压电输电线路的无源干扰模型,通过FEKO软件的仿真,分析高压输电线路的无源干扰影响,为中波无线电导航台站的环境需求提供理论依据。     

中波广播发射天线的原理及其维护研究

随着我国无线广播事业的发展,中波广播发射技术的应用也日趋广泛。中波广播发射天线是用来发射无线电波的一种装置,天线信号容易受到各类因素干扰,因此对中波广播发射天线的维护具有重要价值。在明确中波广播发射天线原理的基础上,阐述其架设高度与地网设计,并提出了中波广播发射天线的维护措施,以期为中波广播发射天线技术的运用提供帮助,减少由于故障干扰引起的信号传输不良等问题。     

中波广播发射天线的原理及场地保护

中波广播发射天线是中波发射台的重要播出设备及广播电视发射系统中重要组成部分,属于广播电视节目播出的关键一环,其对发射系统的正常发射具有决定性作用.因此需要掌握中波广播发射天线的原理,重点关注各项参数,并做好发射天线区域的场地保护工作,有效的保证中波广播天线发射的质量,为中波天线的发展起到了积极的促进作用.     

高压线路干扰中波发射天线的问题解决

我中心所属白银广播转播台自1989年建台以来,高压线路干扰中波发射天线的问题一直没有得到很好解决.2013年我们利用双回路匹配网络和天线加顶技术,先后三次对天调网络和天线塔体进行了技术改造,解决了困扰我台30多年的问题,为复杂电场情况下解决发射机与天线匹配和干扰问题提供了新的办法,达到了满意的效果.     

中波广播发射天线多频共塔天调网络优化设计

中波广播是现代社会中人们获取信息的重要途径之一，具有传输距离远、信号稳定等特点，被广泛应用于各个领域。然而由于中波广播发射天线系统的特殊性，存在信号干扰、传输距离受限等问题，影响广播的质量和效果。针对中波广播发射天线系统存在的问题，设计多频共塔天调网络优化方法。通过对发射天线进行优化设计，可以提高信号的传输质量，延长传输距离，减少信号干扰，扩大广播信号的覆盖范围。此外，该方法还可以提高发射天线系统的效率，降低能耗，减少对环境的影响。     

中波广播发射天线的原理与维护措施研究

中波广播发射天线,是无线广播事业发展的重要基础。在中波广播发射天线研究和发展中,需要对其原理进行全面有效的掌握,从而能够提高广播天线发射能力,确保发射信号质量。在中波广播发射天线工作中,需要重视维护工作的实践。通过有效的维护,可以避免中波广播发射天线运行故障,消除不利影响。     

中波广播发射天线双工匹配网络的设计

信息时代的到来促进了广播技术的发展,中波发射信号优势被人们越来越关注。在台站有限的基础上提升中波天线的地网占有率,是现代中波广播发展面临的全新问题。保证发射天线的数量提升发射频率数量能够解决天线数量不足导致的信号接收状况差的现状。本文对中波广播发射天线双工匹配网络的设计进行分析,希望能够推动中波广播的发展创新,更好的适应社会的需求。     

中波天线地网对发射效果的影响研究

中波天线地网在当代广播电视信号发射中发挥着重要作用,关系着信号发射质量.提升广播电视信号发射效果,理应谨遵中波天线地网运行原理,加强中波天线地网建设,全面优化广播电视无线数字覆盖工程信号传输方案,控制各种电子通信干扰问题.本文将简析中波天线地网对发射效果的影响,希望能为广播信号发射工作提供参考与借鉴.     

Short range active transmitting antenna with very large height reduction

A resistive input impedance transmitting antenna system with a total dipole height oflambda/2000instead of the conventionallambda/2has been built and compared with a passive dipole of equal height. The active network-antenna combination is extremely broadband and is capable of working at frequencies well below those where inductively loaded passive antennas can readily be made.     

Optically fed aperture-coupled microstrip patch antennas

Several techniques are presented for feeding microstrip antennas with RF-modulated lightwave signals via an optical fiber. Lightwave-to-RF conversion is performed in a module containing a photodiode, RF circuitry, and a microstrip antenna element. Three different transmitting configurations at microwave frequencies were designed and tested: passive matching, matching with amplification, and an injection-locked oscillator. In each case, the only connections to the antenna modules were an optical fiber and DC bias lines     

Occupational exposure to RF fields from base station antennas on rooftops

At specific situations, workers need to approach very close to the transmitting base station antennas. In this study, occupational exposure to RF fields from base station antennas was assessed at several rooftops. The measurements were carried out by mapping the power densities around the antennas. The results were compared with the ICNIRP guidelines. The results indicate that the reference levels for workers and the general public may be exceeded in front of the transmitting antenna at distances up to 1 and 2 m, respectively.     

基于延迟自相关双门限的短波天线选择方法

短波固定台站配有多副发信天线,在实际应用时,一般是根据预先方案选择一副天线发射信号,没有充分利用天线的方向性,因而通信效果并不是最佳.针对这一问题,设计了一种能够在收发双方进行天线发送信号质量评估的探测机制,通过基于延迟自相关运算的双门限检测技术,在收接端判决各发信天线探测信号质量,然后根据评估分值,从短波固定台站众多的天线中自动选择通信效果最佳的发信天线发射信号,在不改变现有配置的情况下最大限度地提升通信质量.仿真结果表明,该方法可行有效,能够以较小的代价提高天线选择效率,充分利用天线的方向性,达到提升发射效率和通信效果的目的.     

圆极化和水平极化天线在调频广播的应用对比分析

本文介绍了水平极化和圆极化两种天线的特点和参数,通过当地发射台安装的两副不同极化天线,在相同环境条件下收测其覆盖场强,将收测的数据进行对比,分析了两副天线的覆盖效果,并据此对调频广播发射天线的更新换代提出建议.     

基于天线选择技术的大规模下行MU-MIMO系统能效分析

为了提高大规模多用户多输入多输出(MU-MIMO)下行系统的能效,提出了一种基于发送天线选择技术的能效优化机制。首先建立了同时考虑发送功率与电路功耗的新的系统功耗模型,并基于该模型,分析了基站配置天线数目与所有接收终端用户数目对系统总功耗及能效的影响。然后通过理论推导得到了系统能效最优时的最优天线选择数目,并与使用全部天线时的系统能效进行比较。仿真结果表明,所提出的发送天线选择机制通过优化激活部分基站天线能够明显提高系统能效。在用户数为10、发送功率分别为40 W和10 W时,与使用全部天线相比,天线选择技术能够分别使得系统能效获得大约12%和78%的性能增益。     

FM wide band panel dipole antenna

It is very common that when a broadcaster needs to install an FM transmitting antenna within a large metropolitan area he places it on the tallest structure or building available. When the rooftop is already occupied by a large number of other types of transmitting and receiving antennas, the panel dipole antenna should be chosen. This antenna is secured to the side walls of the upper floors with the panel oriented to obtain full coverage of the most desirable areas of the city. For the Buenos Aires area this orientation avoids radiating toward Uruguay and specifically toward Montevideo, some 140 miles away. A wide band antenna operation permits placing the station on the air and at the same time allows future stations to share it without the installation of new antennas. Details of model and full model impedance and radiation pattern measurements during the antenna development are presented in order to show its technical characteristics. The radiation patterns were measured on a scale model in an anechoic chamber. The full scaled model was measured in an outdoor antenna range. Both E and H plane radiation patterns were measured along the FM band in order to observe pattern variations on both planes. Practically no difference in a panel radiation beamwidth from 88 to 108 MHz was observed and at the same time good input impedance was maintained. A really wide band antenna in pattern and VSWR is obtained. Power division for the antenna system is obtained designing an eight port power divider using the microstrip line technique. In this case, however due to high power operation the ground plane and strip are contained in a sealed metallic box and are separated by high pressure dry air like into the 3" feeding coaxial line.     

Performance of a meandered line as an electrically smalltransmitting antenna

For antennas to radiate at maximum efficiency, their dimensions must be on the same order as the radiated wavelength. At frequencies below 30 MHz, antennas with efficient radiation are often too large for mobile and portable applications. Smaller antennas can be made to radiate efficiently by use of matching networks. For installation convenience and ease of adjustment, these networks are usually placed between the transmitter and the antenna input; but it has been found that for best radiation efficiency, matching network elements should be placed at points on the antenna structure. Unfortunately, such matching networks must be tuned for each transmitting frequency and, when mounted on the antenna, they cannot easily be tuned. A meander element antenna was found to present some electrical and mechanical properties allowing convenient placement of tuning elements when configured as an electrically small transmitting antenna. Some simplified design guidelines were derived from experimental data     

Near-field scanner for the detection of passive intermodulation sources in base station antennas

Passive intermodulation (PIM) distortion is a challenging problem in the design and manufacturing of base station antennas. Small nonlinearities, typically in junctions, may cause a distortion signal that interferes with the receiver even with a level of -155 dBc in a GSM900 system. The PIM level specification of an outdoor base station antenna is difficult to achieve and the sources of PIM generation are laborious to track down. In this paper, a near-field measurement method is presented to localize and investigate passive intermodulation sources in antennas and open transmission lines. The principle of the PIM near-field measurement is otherwise the same as in a common reactive near-field measurement, but instead of measuring the signal at the input frequency, the signal amplitude and phase at the PIM frequency of interest are acquired. The constructed measurement system is capable of measuring PIM signal levels down to -110 dBm with 2/spl times/43 dBm transmit power in the GSM900 frequency band. As demonstration measurements, PIM sources in a two-element base station antenna and in a microstrip line are localized.     

A Time/Frequency Model of Ultrawideband Antennas

A new approach to model ultrawideband (UWB) antennas is proposed. A mathematical analysis of transmission through an UWB system in terms of transfer function and impulse response is proposed. The analysis allows the separation of the transmitting and receiving antenna characteristics, using a consistent treatment with other UWB and earlier narrowband analysis techniques. A parametric modeling is added to provide efficient directional time-frequency models of UWB antennas. The technique is demonstrated through simulation and experiment.