基于GIS技术的两个无线电监测应用系统(下)

(接上期)2.2场强覆盖预测测量系统的主要功能场强覆盖预测测量系统的主要功能有以下几项:(1)场强覆盖预测区域图的显示是场强覆盖预测测量系统最主要的功能。预测区域图分二维图和三维     

无线电监测系统的组成与应用

描述了我国无线电监测系统的发展现状和背景,分析了无线电监测系统的原理和结构,说明了其在自动监测模式和手动监测模式下的运行机制。最后针对场强覆盖预测系统,从电波传播模型的选取、系统主要功能、以及GIS技术在场强覆盖预测系统中的应用等方面进行了说明。通过采用GIS中的空间分析和三维分析技术,就能对场强预测系统进行二次开发,提升其性能。     

专用网移动通信系统参数的预测

介绍了移动通信的场强特性和传播模型；城市汽车、铁路移动通信灵敏度及其恶化量等的测试；移动通信的系统方程和系统参数的预测；最后，举例计算预测了某专用网移动通信系统的一些参数。     

调频广播及航空导航业务干扰评估中的场强预测方法研究

本文介绍了米波段调频广播场强和航空导航仪表着陆系统ILS场强预测方法,以ITUR SM.1009-1建议书为基础,根据干扰的特点和产生机理,给出了调频广播场强和仪表着陆系统ILS场强预测详细计算方法。     

移动通信工程中覆盖半径的预测

以城市环境中场强预测模式（Ｏｋｕｍｕｒａ模式）为基础，给出了在移动通信工程设计中市区、郊区移动通信系统覆盖半径预测的具体步骤，并举例说明。     

移动网无线信号场强预测软件的研发

介绍了移动网无线信号场强预测软件研发的目的、目标、方法及其应用。研发的目的主要是开发出适用于900MHz移动通信网无线信号场强预测的算法及用于实际网络优化的应用软件。在研发的过程中，借鉴了神经网络的原理，形成了基于路测的自适应场强预测算法，并以GIS为手段，面向应用开发软件平台，总结出了无线信号场强预测的算法，研发出了用于无线网络优化的应用软件。     

三维射线跟踪传播模型在移动通信中的应用

随着移动通信的发展，为了充分利用频谱、提高系统容量，“蜂窝”（cell）的面积变得越来越小，例如从大蜂窝制到小蜂窝制，现在又出现了微蜂窝和微微蜂窝。蜂窝面积越小，在网络设计、场强预测、干扰分析时，就越要更多地考虑基站周围建筑物对计算结果的影响。实际上．移动通信场强覆盖预测计算的模型可分为两大类：一类是统计模型；另一类是确定模型。     

移动通信场强预测软件设计研究

移动通信网络规划中，电磁波传播特性是其通信系统设计的依据，介绍了移动通信系统中场强分布预测软件设计的原理和实施步骤，利用基于电波的传播模型，采用计算机模拟比较和评估设计方法，筛选出最佳通信网络规划配置方案。     

移动通信场强预测软件设计研究

移动通信网络规划中，电磁波传播特性是其通信系统设计的依据，介绍了移动通信系统中场强分布预测软件设计的原理和实施步骤，利用基于电波的传播模型，采用计算机模拟比较和评估设计方法，筛选出最佳通信网络规划配置方案。     

移动通信系统的场强预测模型与计算机模拟

应用计算机模拟技术来预测移动通信系统电波传播的场强,对于提高移动通信系统的设计质量及加速设计进程,经济效益明显,具有重要的现实意义。本文在研究典型的传播模型基础上,提出了较适合我国情况的实用模型及用计算机模拟进行场强预测的方法、软件流程和几个主要技术问题,具有实用价值。     

Electric-field and magnetic-field sensors

Analysis of double-loaded loop antennas and their properties has led to the design of new measuring sensors which enable determination of both electric field strength and magnetic field strength. Sensors of the design proposed are applicable to a quasipoint measurement providing independent determination of the electric and magnetic component of the field.<>     

Influences of structure around gate-edge on high electric field strength in MISFETs with high-k gate dielectrics

In this paper, dependences of electric field strength around gate-edge in gate dielectrics of MISFETs with high-k gate dielectrics on design parameters are studied. It is newly found that locations of sidewall/gate dielectric interfaces relative to gate electrode edges are critical to electric field strength of high-k MISFETs. Electric field can be as high as 4 MV/cm, which could have large influences on the yield of large scale integrated circuits (LSIs) with high-k gate dielectrics. An explanation of this phenomenon is given by considering discontinuity in electric field at interfaces between two materials with different dielectric constants. It is clarified that an electrical potential of side and top surfaces of gate dielectrics is strongly affected by the discontinuity of electric field strength at interfaces. As a result, electric field strength around gate electrode edges critically depends on locations of sidewall/gate dielectrics interfaces relative to gate electrode edges. Based on the physical considerations, a structure, in which gate sidewalls are also made of high-k materials, is studied from the viewpoint of electric field strength around gate electrode edges. It is shown that this structure effectively suppresses electric field strength around gate edges.     

Miniaturized Flexible Electronic Systems with Wireless Power and Near‐Field Communication Capabilities

A class of thin, lightweight, flexible, near‐field communication (NFC) devices with ultraminiaturized format is introduced, and systematic investigations of the mechanics, radio frequency characteristics, and materials aspects associated with their optimized construction are presented. These systems allow advantages in mechanical strength, placement versatility, and minimized interfacial stresses compared to other NFC technologies and wearable electronics. Detailed experimental studies and theoretical modeling of the mechanical and electromagnetic properties of these systems establish understanding of the key design considerations. These concepts can apply to many other types of wireless communication systems including biosensors and electronic implants.     

Simulation and design of field emitter array

Some simulation results about potential, field strength, and emitting current density of cone-shaped emitter arrays are presented. Several important design features about the field emitter array are discussed. The most striking feature is that if one wants to obtain more current from the field emitter array in a given device area, there is a limit to the density of the emitter array due to the emitter tip field strength lowering effect, which is a result of the interaction from nearby surrounding tips. If one reduces the tip radius to increase the field strength a higher current density is compensated by a reduced effective emitting area; therefore, to obtain the highest emitter current for a certain set of designed emitter array geometric parameters a corresponding optimal tip radius needs to be determined     

Microstrip patch designs that do not excite surface waves

Two variations of a circular microstrip patch design are presented which excite very little surface wave power. Both of the designs are based on the principle that a ring of magnetic current in a substrate (which models the patches) will not excite the dominant TM₀ surface wave if the radius of the ring is a particular critical value. Numerical results for radiation efficiency and radiated field strength from a ring of magnetic current are shown to verify this basic design principle. The proposed patch designs are chosen to have a radius equal to this critical value, while maintaining resonance at the design frequency. The designs excite very little surface-wave power, and thus have smoother radiation patterns when mounted on finite-size ground planes, due to reduced surface-wave diffraction. They also have reduced mutual coupling, due to the reduced surface-wave excitation. Measured results for radiation patterns and field strength within the substrate are presented to verify the theoretical concepts     

缩小倍率型永磁聚焦天文成像探测器系统的研究

本文从当代天文光电成像探测器的发展现状与实际需要出发，着重探讨寻求允许输入像面不是平面、放大倍率不等于１的永磁聚焦磁场系统的设计途径，用约束变尺度法来设计在电磁聚焦成像系统中实现给定的不均匀磁场分布的实际永磁环磁路系统。     

A Dynamic Optimal Pilot Design Method for OFDM Systems

Wireless communication systems are increasingly adopting orthogonal frequency division multiplexing to enable high data rate transmission. Such systems employ pilot symbols to estimate wireless channels. While pilot symbols facilitate channel acquisition, they consume part of bandwidth, which in turn reduces spectral efficiency. In this paper, a new pilot design method with virtual subcarriers is proposed. The pilots can be dynamic designed with the previous bit error rate (BER) and signal-to-noise ratio (SNR). The BER sectioned is utilized as the performance metric for the optimization of the total number of pilots. And then the proposed scheme maximizes a simple function relevant to SNR strategy based on the allocation of pilot locations. So the dynamic pilot design will optimize the total number and locations jointly and offer the potential of enhancing data rate while maintaining the quality of service in time-varying wireless channels. Comparing with the conventional pilot design which is commonly used in many protocols, the proposed scheme is more robust to the channel state, which could make good trade-off between data transmission efficiency and channel estimate accuracy.     

一种基于压缩感知的同频多辐射源数量估计及定位方法

本文提出了一种基于压缩感知的多辐射源数量估计及定位方法,能够较为准确地对未知的多个无线电辐射源的数量估计并定位.方法通过移动监测,在区域内部分位置上获取场强值.在对场强值进行预处理后,利用目标源的空间稀疏性,结合传播模型及压缩感知方法进行粗定位,用较少场强值重构计算出区域内未知同频辐射源数量.在此基础上进行二次定位确定辐射源的位置,提高了定位的准确度.通过对算法进行仿真与实验验证,证明了本文方法的有效性.     

Analysis of timing and amplitude jitter due to intrachanneldispersion-managed pulse interactions

Transmission impairments due to nonlinear intrachannel crosstalk in strongly dispersion-managed systems are investigated. Analytical expressions to estimate timing and amplitude jitter due to intrachannel pulse interactions are provided. Timing jitter is found to be a dominant limiting factor for small values of map strength, whereas amplitude jitter is responsible for system performance degradation especially for large map strength. The analysis agrees with direct numerical simulations of the full system     

Approximations useful for the prediction of electrostaticdischarges for electrode geometries

This paper provides approximations for estimating the capacitance and the ratio of electric field strength to potential for a certain class of electrode geometries. The geometry consists of an electrode near a grounded plane, with the electrode being a surface of revolution about the perpendicular to the plane. Some examples that show the accuracy of the capacitance estimate and the accuracy of the estimate of electric field over potential can be found in the appendix. When it is possible to estimate the potential of the electrode, knowing the ratio of electric field to potential will help to determine if an electrostatic discharge is likely to occur. Knowing the capacitance will help to determine the strength of the discharge (the energy released by it) if it does occur. The medium between the electrode and the grounded plane may be a neutral gas, a vacuum, or an uncharged homogeneous isotropic dielectric