Analytic Specific Attenuation Model for Rain for Use in Prediction Methods

Based on the values of k and given by ITU-R for the power-law relationship of specific rain attenuation _R=kR , the analytic expressions for k and are regressed as a function of frequency and are in high agreement with the values tabulated. The specific rain attenuation calculated by the analytic expressions are also in high agreement with those by the values of k and tabulated. Comparisons with other analytic expressions show that the ones in this paper are more accuracy and simple.     

雨介质的等效介电常量模型

利用系统辨识法研究了雨介质的介电常量,分别得到了毫米波段雨介质的雨强等效介电常量模型和频率等效介电常量模型,利用模型计算雨衰减的结果与有关文献完全一致,表明所得模型实用有效;利用雨强等效介电常量模型得到的电磁波的交叉去极化与文献基本一致.     

New Measuring Apparatus for Complex Permittivity at Millimeter-Wave Frequencies

A dielectric rod resonator excited by a nonradiative dielectric waveguide is used for measuring complex permittivity of low loss dielectric materials. The complex permittivties of single crystal sapphire, polycrystalline Ba (Mg_1/2 W_1/2) O₃ and Mg₂ Al₄ Si₅ O₁₈ (cordierite) have been obtained at 60 and 77 GHz by the new apparatus. The first time the measurement results of complex permittivity of brain grey and white matters from 15 to 50GHz utilizing a two-port microstrip test fixture is presented. S-parameters of Test fixture are simulated employing the finite-element method. A new spectrometer for the precision measurement of dielectric permittivity and loss tangent, which is capable of providing high resolution data for the first time over an extended W-band (68-118 GHz) frequency for specimens with a large range of absorption values, including highly absorbing specimens that otherwise would not be possible.     

The Study of Depolarization Effects due to Rain Media in MM Wave Band by System Identification

We use an equivalent random system for the discrete rain medium. A serial model of computing cross-polar discrimination (XPD) is given by system model with propagation experiment data in Xi'an, China. The calculated results show this method is effective and straightforward.     

Modelling of Drop Size Distribution of Rain from Rain Rate and Attenuation Measurements at Millimeter and Optical Wavelengths

This paper describes a technique for modelling of rain drop size distributions at Calcutta in terms of negative exponential function, from the measurements of rain rate and attenuation over a dual wavelength LOS link at millimeter and optical frequencies. The DSD model obtained is then used to determine the attenuation at 94 GHz, for comparison with experimentally obtained attenuation at 94 GHz. This is also compared with the attenuation calculated by considering other experimentally obtained DSD models. The best fit negative exponential distribution function (modified M-P model) is presented along with some other experimentally obtained and reference models.     

Measurements of cloud contribution to rain millimeter wave attenuation by using a radar and radiometers

The measurement technique of cloud contribution to rain attenuation and the equipment consisted of the coherent pulse Doppler radar at wavelength =3.2 cm, the radiometers at=0.4; 0.8 and 1.35 cm and apparatus for signal recording and processing is described. The results of such measurements are given. The Doppler spectrum of the rain backscattered radar signal was used for determination of rain drop size distribution height profile then rain attenuation was calculated and cloud attenuation was determined as the difference between the total attenuation measured by using the radiometers and rain attenuation. The results of this work gave possibility to improve the known rain model of P.Misme for prediction of rain attenuation statistics for Earth-satellite links at millimeter wave.     

Rain induced attenuation for 3mm wave band and its measurement system

In this paper, the effect of rain induced attenuation for millimeter wave is discussed. The theory of multiple scattering is used to obtain the solution for the plane wave propagation through a plane parallel medium of thickness L containing randomly distributed nonspherial particles. The coherent field and the total field are studied, respectively. The numerical results are good agreement with experimental data and the multiple scattering effects must be included. A 3mm wave propagation measurement system was made on a 0.8km terrestrial link.     

Scattering of Millimeter Waves from Acid Rain

A theoretical investigation of scattering characteristics of millimeter waves from acid rain is conducted using the method of vector spherical function expansion. The particles of acid rain are considered as the double-layered spheroid. The method is used to derive an analytical solution to the problem of scattering of millimeter waves by a coated dielectric spheroid. The normalized bistatic cross section versus scattering angle for the acid raindrop is calculated at frequencies of 35 GHz and 94 GHz. This is the first part of our study scattering characteristics of millimeter waves from acid rain.     

The Prediction of Rain-Induced Attenuation in MM Wave Band by Rain Medium System Model

While the millimeter radio wave propagates through rainfall, it will be attenuated heavily due to assimilation and scattering of rain. It is imperative to establish a simple and effective model to predict the rain-induced attenuation. In this paper, the rainfall is taken as a random system that can attenuate the radio wave. The transfer function matrix model is selected to be the random system model. Using experiment rain attenuation data at different rain rate, the correlation entropy and residue error of the system is obtained by system identification method. On the basis of correlation entropy and residue error, we can determine the order of the predication system. At last, the predication model that can forecast heavy rain attenuation by small rain attenuation is gotten by applying the least square method. The comparison shows that the discrepancy between the predication result of the obtained model and the experiment rain attenuation data is relatively minor.     

Statistical Prediction Modeling of Rain Induced Attenuation and Depolarization

Millimeter wave rain co-polarization attenuation, CPA, and cross polarization discrimination, XPD, measurements have been made at 35GHz and 94GHz over a line-of-sight link. On the basis of these experimental results, a study of this rain medium has been made with the method of link measurements. In this paper, we presented a statistical prediction modeling of rain-induced attenuation and depolarization from the statistical distribution of the rain intensity, and the size, and canting angle of raindrops. Our computational results are in good agreement with data of measurements.     

Matrix of Light Reflection from a Crystal with an Arbitrary Permittivity Tensor

Exact and approximate procedures of calculating the matrix of light reflection from a homogeneous medium with an arbitrary permittivity tensor are described. It is shown that in practice, in connection with the smallness of anisotropic additions, errors of calculation by approximate formulas are within the experimental accuracy of ellipsometric measurements. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 560–562, July–August, 2005.     

Radiometric Measurements of Rain Attenuation at 22.2 and 31.4 GHz Over Calcutta

Measurements of rain attenuation over Calcutta have been made using radiometers operating at frequencies of 22.235 and 31.4 GHz. The results have been correlated with observations of rainfall rates made with a fast-response rain gauge. The distributions of peak rain rates over Calcutta for two different years and the cumulative occurrences of rainfall rates and attenuations at the two frequencies are presented.     

Measurement of permittivity of aqueous solutions at 44 GHz by FM receiver

An instrument using a variable-thickness waveguide cell has been developed for measurement of absolute complex permittivity at 44 GHz. The superheterodyne is used to rise the sensitivity. The results of measurements of water and saccharose aqueous solutions in the range of 15–27 °C are presented.     

The main results of cloud and rain remote sensing by multichannel microwave radiometry

The basic results have been considered for multiwave remote sounding of the troposphere with clouds and rain from ground-based station in the zenith direction. The radio wave scattering by rain drops as well as variation of vapour content in the atmosphere during measurements are taken into account when processing of the experimental data. A separation of the complete attenuation in clouds with rain has been made over three components: due to vapour, cloud and rain. A relation is considered of millimeter and centimeter wave attenuation in clouds with rain between each other and with the rain intensity. A behaviour of the relation of attenuation structural functions is explained. The Diagnostic problems of millimeter wave attenuation are considered.     

A New Formula of Specific Rain Attenuation for Use in Prediction Methods

A new formula of specific rain attenuation aR ^b has been studied, the analytic expressions for a and b are regressed as function of operating frequency and polarization of microwave and millimeter wave system, which are based on the values given by International Telecommunication Union-Radio communication. The results of a and b calculated by this formula are in good agreement with that of tabulated by ITU-R for the power-law relationship of specific attenuation for rain for use in prediction methods.     

Knowledge-Based Artificial Neural Network Models for Finline

Finline plays an important role in millimeter-wave integrated-circuit design. In this paper, a knowledge-based artifcial neural network is used to model the finline. Using prior knowledge input method and Bayesian regularization technique make the neural network models for finline reduce the amount of training data needed and prevent overfitting in neural network training. The neural network is electromagnetically developed with a set of training data that are produced by the fnite element method, which is robust both from the angle of time of computation and accuracy.     

毫米波在等离子体中的衰减特性研究

为了研究毫米波与等离子体的相互作用,采用时域积分法对毫米波在等离子体中传输时的衰减特性进行了仿真,初步研究了毫米波在等离子体中传输时的衰减值与等离子体密度、碰撞频率及其工作频率之间的关系.通过理论结果和仿真结果的分析比较,验证了仿真可以为理论研究提供数据支撑的可行性. 关键词： 毫米波 等离子体 时域积分法 衰减     

频率相关材料的计算模型分析

系统地介绍了Debye、Drude、Lorentz模型相对介电常量的推导过程,并给出了其相应结果;再用有损耗的Drude模型讨论了当前引起广泛关注的左手介质的性质;最后通过推导和举例,进一步揭示了各种模型在实际研究中的重要作用.     

An approximate analytical solution of the radiative transfer equation in hydrometeors accounting for scattering effects

An iterative method for the radiative transfer equation solution is suggested for the scattering hydrometeors. The method allows to find the layer scattering indicatrix. The method is shown to be more general as compared with the four-flux theory or the perturbation method and differs strongly from these ones because even in the case of the first iteration it gives the results which are very close to ones obtained by numerical methods for all rain scattering angles.     

典型光谱吸收模型对静止轨道毫米波辐射分析

为分析我国未来拟发展的高轨静止卫星毫米波大气辐射特征,选择最佳模拟其毫米波辐射的光谱吸收线库方案,选取了三种基于典型光谱吸收线库逐线吸收模型(毫米波传播模型(M PM)、罗氏模型(ROS)和高分辨率分子吸收传输模型(HITRAN)),针对拟新增的静止轨道毫米波探测频率424 GHz,分析了三种大气吸收模型模拟该频率大气...