战场沙尘环境中三毫米波通信的研究

本文给出了模拟战场沙尘环境中，沙尘对三毫米波通信产生的衰减和通信误码率的测量结果。推导了正态对数分布的沙径分布状态下沙尘产生的裹减理论公式。根据现场测量的沙径的统计参数和通信信道的信嗓比，从理论上计算得到沙尘产生的衰减及通信误码率。     

我国典型沙区中沙尘的物理特性

针对我国典型沙区的理论研究和实验结果，着重系统地讨论了我国塔克拉玛干沙漠等典型沙区的有关沙尘浓度，粒径分布，形状分布，介电特性等物理特性及其受环境因素的影响。     

沙尘暴多重散射对毫米波衰减影响研究

根据随机介质中电波传播理论,应用等效介电常数法和Mie理论,研究毫米波在沙尘暴中传播的衰减;并应用Monte Carlo方法,研究沙尘暴大气中毫米波多重散射对衰减的影响.分别得到了单次散射和多重散射时沙尘暴引起的毫米波段几个大气窗口频率的特征衰减,及随沙尘大气能见度和沙尘粒子水含量的变化关系.结果表明,当能见度小于1 km时,随着能见度的减小,特征衰减增大很快,多重散射的影响也愈来愈大.衰减随含水量的增加而增加,尤其当沙尘粒子水含量大于1%时增加较为显著.因此,对于预测自然沙尘暴大气对毫米波的衰减,当能见度小于1 km时,必须考虑粒子的多重散射效应.当沙尘粒子的水含量超过1%时,需要考虑水含量的影响.这些研究对民用和军用通信、遥感等系统的开发和应用均具有重要的实际意义.     

毫米波新技术

８０年代以来，世界各国地毫米波的研究进入了一个新的高潮。人们认识到，用红外线和光学系统完成某些任务有许多限制，尤其是在雾、尘埃和夜间观察等条件下，缺点更加突出，而频谱的微波部分又太拥剂因此认为毫米是最佳选择。本文主要介绍当今毫米波的最新技术以及毫米波系统在军事上的一些应用。     

毫米波通信技术及其发展与应用

简单介绍了毫米波的基本概念及相关背景，分析了毫米波的四个传播特性，并由此引出毫米米波通信具有通信容量大，安全保密好，传输质量高及全天候通信四大优点．阐述了毫米波地面通信及毫米波卫星通信的发展情况，以毫米波通信技术在电子对抗中的军事应用为例进行重点探讨，最后展望毫米波通信技术将会开创未来新型应用领域并拥有广阔的发展前景。     

毫米波固态器件及模块技术进展

毫米波固态器件及模块技术由于其体积小、重量轻、可靠性高等优势，已在毫米波技术领域逐步占据了重要地位，本文重点介绍了从雪崩管、耿氏管、隧道管等两端器件到三端器件MESFET，再到新型器件，如PHEMT，HBT等的发展历程，以及毫米波集成电路技术和毫米波模块电路技术的进展情况。     

激光在沙尘暴中的衰减特性研究

复杂环境中激光传输和散射特性是目标与环境光散射特性研究的基础。主要讨论了激光信号在沙尘中的传输衰减特性。根据Mie理论研究了具有一定粒径分布沙尘粒子对于激光信号的单次散射衰减特性，给出了不同分层沙尘粒子的平均散射截面、粒子平均反照率、平均不对称因子和平均相函数。利用四通量法和蒙特卡罗法研究了激光在分层沙尘大气中的多重散射和斜程传输衰减特性，并给出它们与能见度及高度的变化关系。最后，在考虑多重散射时，分别用以上两种方法数值计算了1．06μm激光在斜程沙尘大气中的衰减率，并与单次散射结果进行了比较。结果表明，能见度较低时，不考虑多重散射效应会带来较大的误差；在斜程沙尘大气激光传输时，随分层数增加，数值结果就越精确。     

沙尘天气对无线电测控设备性能的影响研究

针对无线电测控设备系统G/T值测试数据在晴朗天气和沙尘天气下的差异,从沙尘粒子的特性出发,结合干沙与水的复介电常数公式,获得了沙粒的等效介电常数模型,建立了沙尘粒子引起微波衰减的计算模型,对该设备G/T值测试结果受沙尘天气影响的现象进行了分析。结果表明:沙尘天气对设备G/T值测试结果有明显的影响。沙尘粒子密度越小,沙尘衰减越轻微;沙尘粒子密度越大,沙尘衰减越严重。给出了沙尘天气对无线电测控设备性能的影响程度。     

基于偏振激光雷达对远距离传输沙尘在局地混合过程的观测研究

利用国控站点的 PM2:5 和 PM10 含量, 分析了一次蒙古地区沙尘的远距离传输事件; 并结合 532 nm 偏振激光 雷达的观测结果, 研究了沙尘在武汉地区的混合过程。研究表明, 在这次沙尘事件中, 边界层顶的夹卷过程和边界层 内的对流混合对沙尘在局地的分布起到重要的作用。在沙尘输入初始时期, 沙尘高度约为 1 km, 主沙尘层经过边界层 顶的夹卷过程进入边界层内, 并在对流混合作用下在边界层内最终呈现近似均匀的高度分布。在沙尘事件末期, 北方 污染的输入带来约 4300 t 城市气溶胶, 约为军运会期间武汉地区城市气溶胶总含量的十倍。     

利用遥感手段判识沙尘暴的一种新方法——以内蒙古地区为例

利用比辐射率的特征,并根据热辐射理论进行沙尘暴遥感监测是一种全新的研究手段.本文发现,沙尘发生时地表的主要物质沙尘、地面和云的物质性质不同,并且沙尘强度不同时图像像元上的地面和沙尘的比例不同,从而导致像元物质的性质有差别,地物比辐射率不相同.通过理论推导和试验研究得出:云区、地面、弱沙尘和强沙尘区的ε29与ε31接近程度不同,且ε31在0-1整个区间上变化时,ε29的大小顺序永远是云>强沙>弱沙>地面,并在此基础上建立了一个稳定判识沙尘强度的沙尘指数(DSI)模型.经过多次沙尘暴的实例验证,结果表明,该模型能够较精确地监测沙尘发生的范围和强度.     

电磁波在不均匀尘埃等离子体中的衰减特性

基于WKB近似方法, 研究了高频电磁波入射不均匀尘埃等离子体中的衰减特性.对弱电离尘埃等离子体复相对介电常数的分布特征进行了分析, 讨论了电子数密度、尘埃颗粒数密度对复相对介电常数虚部的影响.利用电子密度分布的抛物模型, 数值计算了电磁波以不同角度入射不均匀尘埃等离子体的衰减特性, 对入射角、电子数密度、尘埃颗粒半径和尘埃颗粒数密度对衰减系数的影响进行了分析.结果表明:随着电子数密度、尘埃颗粒数密度和半径增大, 衰减系数也会变大.     

Research on human blockage effect for indoor 26 GHz mm-wave communications

Based on 26 GHz indoor channel measurements, the blockage attenuation of human bodies was investigated. 2-ray and 4-ray human blockage models were proposed by calculation of the Vogler's multiple knife-edge diffraction field. Results show that 4-ray model fits quite well with measurement data. Human block attenuations are slightly bigger with 1 GHz than with 500 MHz bandwidth. In the blockage measurement of one person moving along the connec-tion line between the transmitter (TX) and receiver (RX), the smallest attenuation is found when the person is located at the middle of the connection line, and the biggest attenuation is observed when the person is nearest from the RX position. In the blockage measurements by multiple human bodies, the attenuation is bigger in the cases which the persons cross the TX-RX connection line with their front faces directed to the horn aperture at the RX than the cases with their lat-eral faces directed to the RX horn aperture. The blockage attenuation is larger with the increase of person numbers, about 5～8 dB more attenuation per person. The results can be used for design of mm-wave 26 GHz indoor communi-cations systems.     

毫米波固体器件的研究发展动态

——本文概述了目前国际上毫米波固体器件的发展动态.毫米波固体器件是实现毫米波系统固态化和小型化的关键.文中详细评述了毫米波固体功率器件、接收器件和单片集成电路,并介绍了毫米波超导器件以及某些新原理、新结构的毫米波固体器件.最后简要地报导了国内毫米波固体器件的研制情况.     

Observation of a strong inverse temperature dependence for the opacity of atmospheric water vapor in the MM continuum near 280 GHz

Using atmospheric opacity measurements made at 278 GHz (9.3 cm^?1) at McMurdo Station, Antarctica during the austral springs of 1986 and 1987, combined with measurements of water vapor profile and total column density from near-simultaneous balloon flights, we have determined the attenuation per mm of precipitable water vapor (pwv) at this frequency. Our data were taken at significantly lower temperatures than other measurements in the literature for which accompanying water vapor pressure and temperature data are available. The results show a strong inverse dependence with temperature: measured opacity per mm of pwv is roughly a factor of two times greater at ?35°C than at ?10°C and three times greater than measurements at the same wavelength at +25°C reported by Zammit and Ade. We briefly review various theories proposed to explain excess absorption in continuum regions. Our lowtemperature measurements demonstrate a significantly greater inverse temperature dependence than embodied in several formulations, theoretical or empirical, proposed to represent mm-wave attenuation as a function of temperature and water vapor. The present results are qualitatively similar to observations of strong inverse temperature dependence in the near IR, but if attributed to water vapor dimer formation, imply a greater binding energy for the dimer than generally proposed by others. There is some independent evidence for a local anomaly in temperature dependence as a function of frequency near 280 GHz. It remains to be established whether our own results are strongly frequency dependent or apply generally to the mm-wave continuum.     

Circular Waveguide System for Trunk Communications

9-km waveguides of 70-ram inner diameter (ID) have been inserted from manholes into ducts of polyvinal chloride (PVC). Expansion joints are provided for taking up length variations. Only a slight increase in attenuation was measured for the helix waveguide after the laying works. Phase-shift-keyed (PSK) signals with bit rates of up to 640 Mbit/s have been transmitted via this line. A new approximation method for calculating the attenuation of practical line routes has been developed. Improved design of lined waveguides should, from theory, reduce the H01route and curvature loss to below 1 dB/km. Experimental repeaters work with a double conversion scheme. They have mm-wave branching networks in oversize rectangular waveguide, IMPATT oscillators and p-i-n modulators for two-phase modulation. Printed or folded tape meanderlines serve for delay equalization.     

Microwave attenuation and cross polarization in dust storms

Some of the electrical and mechanical properties of dust are discussed. An expression for optical visibility during storms is given in terms of the relative volume occupied by dust. Expressions for attenuation and phase shift constants for a medium with precipitating dust particles are derived in terms of visibility and wavelength for both vertical and horizontal polarizations. Expressions for the attenuation and cross polarization of circularly polarized waves are also derived. Computations show that linearly polarized waves suffer but little effect. Circularly polarized waves on the other hand are significantly cross polarized.     

Microwave Propagation in Saline Dust Storms

Dielectric constant of sand-powder sampled from saline dust area have been measured at W band by means of wave-guide method. Based on the analysis of the characteristics of saline dust storms, the microwave and millimeter wave attenuation and phase shift in saline dust storms are investigated.     

CMOS mm-wave transceivers for Gbps wireless communication

The challenges in the design of CMOS millimeter-wave (mm-wave) transceiver for Gbps wireless communication are discussed. To support the Gbps data rate, the link bandwidth of the receiver/transmitter must be wide enough, which puts a lot of pressure on the mm-wave front-end as well as on the baseband circuit. This paper discusses the effects of the limited link bandwidth on the transceiver system performance and overviews the bandwidth expansion techniques for mm-wave amplifiers and IF programmable gain amplifier. Furthermore, dual-mode power amplifier (PA) and self-healing technique are introduced to improve the PA''s average efficiency and to deal with the process, voltage, and temperature variation issue, respectively. Several fully-integrated CMOS mm-wave transceivers are also presented to give a short overview on the state-of-the-art mm-wave transceivers.     

太赫兹波在沙尘中衰减特性

为了研究太赫兹波在沙尘大气中的衰减特性,根据Mie散射理论计算了单次散射情况下沙尘粒子不同尺寸参数下的散射效率因子和不同散射角下的散射相函数值。并得到了具有一定尺寸分布的沙尘粒子的单位距离衰减和能见度的关系曲线。还利用Monte Carlo方法对太赫兹波在沙尘中的多次散射特性进行了模拟计算,分析了不同能见度和不同沙尘类型对太赫兹波传输过程中能量损耗的影响。结果表明:单次散射条件下沙尘粒子的散射主要受尺寸参数影响;沙尘能见度较低时必须要考虑多次散射的影响。研究结果对太赫兹技术在大气环境监测和烟尘和风沙的探测等方面的应用具有参考价值。