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毫米波测云雷达探测云目标时,电磁波除了受到云目标衰减之外,还受到大气传输中氧气以及水汽的衰减,电磁波的衰减导致雷达观测到的回波强度小于云目标的实际回波强度,这种误差将影响云内结构的反演。因此,为了使毫米波测云雷达的探测数据正确地反演出云目标的宏观物理特征,必须对进行毫米波测云雷达工作频率下气象目标物的衰减进行订正。主要利用逐库衰减订正算法以及分级逐库衰减订正算法对英国Chilbolton 观测场94GHz 毫米波测云雷达的一次降水云观测结果进行了垂直方向的大气衰减订正研究,并比较逐库衰减订正算法以及分级逐库衰减订正算法间的反演差异。同时,利用国际电信联盟ITU-RP. 676-10 建议书中氧气以及水汽衰减订正公式进行了毫米波测云雷达探测数据的二次订正。分析和对比结果表明,衰减系数的变化对于云目标的宏观物理特征反演有着明显的影响,并且分级逐库衰减订正法的订正效果强于逐库衰减订正法。 相似文献
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雨衰减严重影响第5代(the 5th Generation,5G)移动通信系统性能.在路径长度小于1 km的短距离链路情况下,现有雨衰减预测模型调整因子大于1,导致预测雨衰减随路径变短而增大,无法支撑毫米波短距离链路系统设计.通过分析国际电信联盟无线电通信部(Radiocommunication Sector of International Telecommunication Union,ITU-R)短距离链路雨衰减试验数据,发现湿天线衰减与路径雨衰减相当,得到毫米波短距离链路必须考虑湿天线衰减的结论.建立了湿天线衰减与降雨率的关系模型,分频段对模型参数进行了拟合,拟合结果与实测数据吻合得较好.提出了考虑湿天线衰减的短距离雨衰减建模新思路,可解决短距离雨衰减预测问题.研究结果有助于提高5G毫米波系统余量设计的可靠性. 相似文献
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通过对ONU弱光的ODN链路衰耗进行分析,发现ODN链路的下行衰耗严重超标的现象,在用OTDR进行故障定位、并测试光纤在相应波长的宏弯损耗后,得出光纤的宏弯损耗是导致ODN链路下行衰耗超标的原因;进一步对ODN链路的入户段光缆进行衰耗测试,从而验证了宏弯损耗是引起ONU弱光的主要原因。 相似文献
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雾衰减经验模型的计算是预测雾衰减的一种重要方法。为了将雾衰减经验模型应用到实际中进行适用性分析, 从米氏散射理论出发, 采用理论推导和仿真分析的方法, 计算了Kruse模型、Kim模型和Ijaz模型中激光在不同能见度下的衰减, 分析了3个模型在计算衰减系数时的差异, 并通过搭建自由空间光通信实验平台, 将实验结果与仿真结果对比分析。结果表明, 650nm波长的激光在雾衰减信道下的衰减结果与Kim衰减模型更接近。此研究结论为西安地区自由空间光通信系统雾衰减系数分析提供了参考依据。 相似文献
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The radiowave attenuation due to oxygen and water vapour has been computed over the frequency range 3–350 GHz making use of the mean surface air pressure, temperature and water vapour at Ile-Ife (geog. lat 7.5°N, long 4.5°E) in Southern Nigeria. It is observed that the attenuation at this tropical location is generally higher than at temperate climates. A similar analysis was performed for rainfall attenuation using rainfall intensity measurements. The results obtained with three different expressions for the rain height showed that a rain height of 3 km is a reasonable assumption for estimating earth-space rainfall attenuation at this location. It is found that for frequencies above 200 GHz, the polarization dependence of the specific attenuation due to rainfal becomes negligible. The computed attenuation is lower that that predicted using the corresponding CCIR rain climate data. The results show that whilst the contribution of oxygen and water vapour to the total atmospheric attenuation could be neglected when compared with rainfall attenuation up to about 150 GHz, the contribution becomes significant for frequencies above 190 GHz. 相似文献
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非致命激光武器实际应用中会受到大气环境影响,造成激光能量衰减,严重影响其作战效果。为精确了解激光在雨中传输的衰减,本文建立了激光在雨中传输的衰减模型,分析研究了激光在雨中的透过率,搭建了激光在雨中传输的衰减实验平台,实验研究了激光透过率与降雨强度和传输距离的关系。结果表明,激光在雨中传输衰减很大程度上取决于降雨强度和传输距离,雨量越大,传输距离越远,衰减越严重,当雨量为60 mm/h,激光传输200 m距离时,透过率已不到40%。仿真和实验结果吻合较好,说明所建立的衰减模型基本符合实际情况,同时也表明搭建的激光雨中传输衰减系统可以用于研究非致命激光武器雨中传输衰减,具有结构简单、易于操作、灵活性较好等优点。 相似文献
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Manabe T. Ihara T. Awaka J. Furuhama Y. 《Antennas and Propagation, IEEE Transactions on》1987,35(11):1326-1330
Millimeter-wave rain attenuation measurements have been made at 50.4, 81.8, 140.7, and 245.5 GHz on a terrestrial path of 0.81 km. On the basis of these experimental results, a comparison between the model of specific attenuation currently adopted by the International Radio Consultative Committee (CCIR) and that based on the raindrop-size distribution derived from our previous propagation experiments at 11.5, 34.5, and 81.8 GHz is made. For the Japanese climate, it is found that the CCIR model underestimates the rain attenuation at frequencies above 80 GHz and that our specific attenuation model is effective for the prediction of rain attenuation in the whole millimeter-wave region. 相似文献
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《AEUE-International Journal of Electronics and Communications》2014,68(1):33-36
A comparison of measured attenuation series with the attenuation series obtained from rain rate measurement by using synthetic storm technique is made for Ku band signal at a tropical location. Validity of the model is tested for the long-term statistics in terms of the cumulative distribution of attenuation occurrence and fade duration. Applicability of the model is also shown to be valid event-wise. It has been demonstrated that the long term statistics of predicted rain attenuation are insensitive to storm translation speed. No significant differences are found when cumulative distributions of predicted attenuation values are compared for different data sampling intervals. It has been observed that there exists a good correlation between the predicted and measured values of attenuation for at least 80% of the events. 相似文献
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探讨超声对肌肉组织超声传输特性。采用脉冲反射法,对肌肉组织沿纤维不同方向传播速度及其衰减规律进行研究。结果表明,对于肌肉组织,超声在顺纤维方向传播时,声速较大;在横纤维方向传播时,声衰减系数较大;水分含量多少对肌肉组织声速影响不大,而对衰减系数影响较大,其变化是影响组织声衰减的主要因素。这表明肌肉组织超声传输衰减特性具有随纤维方向结构变化特征,对研究生物软组织声学特性及其临床应用具有参考价值。 相似文献
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《Antennas and Propagation, IEEE Transactions on》1995,43(11):1207-1216
One year of copolarized signal data from the OLYMPUS satellite's 12, 20, and 30 GHz beacons were examined for frequency scaling of attenuation. The statistics of the ratios of attenuation in dB for the frequency pairs 30/20, 20/12, and 30/12 GHz computed at each 0.1 s-sample instant were found to be nearly independent of fade depth. It was found that attenuation in dB scales with frequency to the 1.9 power. Also, attenuation ratios computed from the separate statistics of attenuation at each frequency for the same level of occurrence are very close to those found from instantaneous attenuation ratios 相似文献
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Q. F. Dong J. D. Xu Y. L. Li H. Zhang M. J. Wang 《Journal of Infrared, Millimeter and Terahertz Waves》2011,32(1):55-63
Based on the forward scattering amplitude function for charged sand particles under the Rayleigh approximation and the effective
permittivity method, a calculation model for microwave attenuation due to charged sand particles is given in terms of equal
sized distribution and lognormal size distribution, and the attenuation is calculated and analyzed. The results show that
the attenuation with charged sand is greater than the case of no charge, and the more concentrative the surface charges on
sand particles are, the greater are the influences on microwave attenuation. When the frequency is not too high, natural sand
and vehicular sand have little effect on microwave attenuation, whereas the attenuation of explosive sand need be considered. 相似文献
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The knowledge of the ratio of rain attenuation at one frequency to that at another on slant paths is useful for the design of satellite-to-Earth communication links and up-link power control systems. It is well known that the rain attenuation is influenced by parameters of precipitation along the slant path such as DSD (raindrop size distribution), raindrop temperature, rainfall rate, and so on. In this paper, based on several DSDs applied to various climate zones, at short microwave and long millimeter wave bands, the attenuation ratios are estimated on Earth-space paths. A comparison of the prediction results with the experiment data in Boston and Kashima areas is carried out. It is shown that the M-P and Weibull DSD applied to rain attenuation ratios estimation are better DSD at higher latitude regions. The Guangzhou DSD applied to rain attenuation ratios prediction is better in tropical and subtropical areas in China. The lognormal DSD may be a appropriate DSD applied to predict rain attenuation ratios in tropical areas at Adown>1dB or R>15mm/h. However, the attenuation ratios predicted by the Guangzhou DSD disagree with by the lognormal DSD, it requires that the DSD applied to predict rain attenuation ratios are further studied in tropical areas. 相似文献
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主要讨论了微波信号大气传播中降雨衰减的估算方法。基于我国部分地区降雨强度长期累计分布 ,计算了部分地区X波段信号传输的降雨衰耗。针对星载SAR的特点 ,分析了雨衰对SAR的影响 ,提出了星载SAR设计时雨衰的指标 相似文献