Accurate low-cost measurement technique for occupational exposure assessment of base station antennas

A new technique for near field measurements around wireless base station antennas is presented. Using these safety measurements the compliance boundaries of a base station are determined and compared with FDTD simulations. Excellent agreement is reported. The measurements are performed in a non-anechoic measurement site which results in a low-cost method.     

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.     

Comparison of simple models for predicting radiofrequency fields invicinity of base station antennas

Two simple approximate models for evaluating exposure to RF emissions from BS antennas are compared. The results are referred to those derived from a full-wave numerical modelling approach to investigate the accuracy and range of applicability of simple models     

A low-cost electrical beam tilting base station antennas for wireless communication system

A multifunctional feeding network is presented in this paper. It contains a one-to-eight Wilkinson-based power divider and eight microstrip lines backed with slot array. In addition, the moveable card printed with seven metal strips serves as a novel phase shifter. By dynamically moving the card, we can adjust the number and shielding area of the slot array and then alter the distribution of phase angle at each port of the feeding network accordingly. For example, in our application, we can have a progressive phase difference between the ports of feeding network and dynamically adjust them by changing the degree of perturbation on the slots array. The characteristic of beam tilting has been carefully examined by measuring the phase angle at each port and also by the far-field radiation pattern of the patch antenna array integrated with this novel phase shifter, in various perturbation conditions. The reliable, easily fabricated, and low-cost characteristics show its potential applications in the base-station antenna design.     

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.     

Effects of directional antennas at the base station on the Dopplerspectrum

We analyze the effect of directional antennas at the base station on the Doppler spectrum. It is well known that the Doppler spectrum is dependent on the probability density function (pdf) of the angle-of-arrival (AOA) of the multipath components at the mobile unit and the direction of the motion of the mobile. The Doppler spectrum is U-shaped, when the pdf of the AOA of the multipath components at the mobile is uniform. Here, however, we study the Doppler fading at the base station and assume that the scatterers are uniformly located around the mobile within a circle and derive the pdf of the AOA of the multipath components at the mobile when directional antennas are used at the base station     

一种微蜂窝室内吸顶式基站天线的研究

介绍了一种新型的圆环形微带天线,它不同于一般的圆环形微带天线,它的内表面镀了一层金属,通过选择馈电点的位置可以轻易实现匹配,克服了一般圆环形微带天线输入阻抗太大不易匹配的缺点。最后,做出了一些实验天线进行测试,发现上下壁间距较小时,理论和实践能很好地吻合;当上下壁间距过大时不容易做到匹配。文中分析了上下壁间距过大不易匹配的原因,并且提出了下一步工作的思路。本文提出的设计这一类天线的方法和理论,对实际设计应具有一定的指导意义。     

MF digital AM station antennas

It is very important having the proper antenna, specially in the MF AM band where achieving the necessary bandwidth in the antenna impedance is a difficult task. This problem is critical in the lower frequencies were the antenna matching to the transmission line generally is very sharp and the best match is obtained only at the carrier frequency with an appreciable power reflection in the lateral frequency bands. This problem is not very important in the classical AM transmissions were the maximum transmitted power is located at the carrier frequency and only a fraction in the upper and lower lateral bands. Of course this produces some distortion in the AM transmission but in this case the quality of the audio is not really of high fidelity, like in an FM transmission, due to a lot of factors, one of them the lack of the full audio spectrum. This problem can be corrected with high fidelity audio transmitters and specially with digital transmission in order to achieve CD quality audio and here the transmitting antenna plays an important role. In this paper MF AM antenna systems are analyzed not only from the input impedance point of view, but with consideration of all the factors in order to determine the best system in bandwidth and radiation properties in different parts of the standard AM band. Cylindrical, type A, and Cantilever classical monopoles and the modern dipole type antenna systems are compared, to provide the criteria for choosing an optimum antenna for the future digital AM service. Examples of measured field strength as a function of distance in a flat region are presented in order to show the interesting MF AM possibilities for a digital service     

Missile base mounted microstrip antennas

Proof of the feasibility of aft mounting low-profile antennas on reentry vehicles is presented. This is an application of state of the art antenna hardware. Aft mounting presents the best reentry environment to antenna hardware, and its practicality has been demonstrated. Microstrip antenna principles can be used to produce very rugged antennas. Their low profile reduces many interface, mechanical, and survival problems. The pattern coverage for these vehicles must be toward the fore direction. This type of pattern requires an interaction between the vehicle and the antenna when the antenna is effectively shadowed from that direction. This paper describes the results obtained by actual experimental hardware. Contoured elements were used, as were foreshortened elements. These elements demonstrated ability to be fit around other aft equipment. The versatility of these elements were further demonstrated by tailoring them for two different types of coverage to accommodate different vehicle operational requirements.     

Estimation of the peak power density in the vicinity of cellular and radio base station antennas

Prediction formulae for estimating the peak equivalent power density in the near-field of cellular base-station array antennas are demonstrated. Theoretical justification stemming from a uniform asymptotic expansion of the field radiated by collinear arrays is described, and verification is carried out by means of an extensive computational analysis of different classes of base station antennas. The formulae, which depend on a few, readily available parameters, can be conveniently employed for the estimation of compliance distances with respect to RF safety guidelines issued by the International Committee on Non-Ionizing Radiation Protection (ICNIRP), which have been adopted in many countries throughout the world, without requiring necessarily extensive and expensive nearfield measurements campaigns.     

Advanced base station technologies for UTRAN

To achieve high capacity and to support high-data-rate services in the terrestrial access network (UTRAN) of the third generation Universal Mobile Telecommunications System (UMTS), it is essential to employ some advanced transceiver techniques at the base stations. Three such techniques are presented: adaptive antennas, multistage parallel interference cancellers and a new hybrid scheme. The operation principles and some simulation results of the techniques are given and some challenging implementation issues are discussed     

基站建设及基站天线的设计与分析

移动基站建设是为人们提供良好通信基础的重要途径,在移动基站建设过程中必须要选择合适的位置,提高基站的维修和运行成本,同时提高运行可靠性和稳定性。文章对通信基站建设以及基站的天线分布进行设计,旨在提高基站的工作效率。     

快速计算套筒单极子天线

利用矩量法分析计算套筒单极子天线的电性能参数。采用与实际天线较为接近的矩量法分析模型和一种新的粗圆柱线天线快速精确计算模型,大大提高了分析计算的精度;引入「Ｚ」矩阵插值法,提高了分析计算的速度。将该方法与最优化技术相结合,设计出一付工作在２００～７００ＭＨｚ频段、ＶＳＷＲ〈２．６、增益Ｇ〉５．１ｄｂ的实用套筒单极子天线,理论分析与实验测试吻合良好,从而说明了该方法的有效性和实用性。     

快速计算通信天线宽频带内的电特性

在分析通信天线宽频事内的特性时，一般需要选取许多频点采用矩量法逐点求解天线上的电流分布，计算时间长。研究了一种对电流系统矩阵[I]进行频域插值的方法来快速分析天线宽频带内的电特性。该方法先利用矩量法直接求出少数较大间隔的频率点上的电流展开系数矩阵[I]，然后利用这些采样频点上的[I]矩阵来插值计算其它频点上的电流展开系数矩阵的元素。采用该方法分析了几个不同天线，与直接采用矩量法计算相比，该方法计算时间显著减少，计算误差很小。     

Feed models for coax-driven monopole and dipole antennas

A method is presented for accurately modeling a monopole or dipole antenna fed by a coaxial line. The base of the monopole is attached to a conducting plane through which the coaxial feed line extends to the feed. The feed structures considered are easily adaptable to physically rugged forms and are simple to construct. Equivalent models for the three regions of the structure are devised and coupled integral equations for aperture fields and surface currents are formulated to enforce the boundary conditions. Three variations of the feed configuration are discussed and the reflection coefficient of the antenna feed is determined from the data obtained from the solutions of the coupled integral equations. Computed reflection coefficient values are shown to agree well with values measured on laboratory models.     

GSM系统基站安装测试

本文简介了ＧＳＭ系统的基站构成和工作原理以及基站的安装测试，包括：平均载波功率、相位和频率误差、功率与时间关系、输出ＲＦ频谱、互调抑制、杂散幅射和合路器测试。     

Advanced base station technology

The authors present an overview of advances in three areas including software radio, adaptive antenna technology, and high-temperature superconductivity as currently envisioned for use in advanced cellular base stations. The conclusion broadly drawn is that the advancement in DSP and ASIC technologies will provide the major contribution in making these technologies technically and commercially realistic     

Planning UMTS base station location: optimization models with power control and algorithms

Classical coverage models, adopted for second-generation cellular systems, are not suited for planning Universal Mobile Telecommunication System (UMTS) base station (BS) location because they are only based on signal predictions and do not consider the traffic distribution, the signal quality requirements, and the power control (PC) mechanism. We propose discrete optimization models and algorithms aimed at supporting the decisions in the process of planning where to locate new BSs. These models consider the signal-to-interference ratio as quality measure and capture at different levels of detail the signal quality requirements and the specific PC mechanism of the wideband CDMA air interface. Given that these UMTS BS location models are nonpolynomial (NP)-hard, we propose two randomized greedy procedures and a tabu search algorithm for the uplink (mobile to BS) direction which is the most stringent one from the traffic point of view in the presence of balanced connections such as voice calls. The different models, which take into account installation costs, signal quality and traffic coverage, and the corresponding algorithms, are compared on families of small to large-size instances generated by using classical propagation models.