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...     

基于球谐函数法的气溶胶辐射强迫分析

本文针对气溶胶的辐射强迫效应开展了数值方法研究。建立了基于球谐函数法的多层半透明介质辐射计算模型。并与射线踪迹-节点分析法的计算结果进行了对比验证。最后,我们使用该模型分析了北京地区的大气气溶胶辐射强迫。结果显示,本文计算出的结果与AERONET的气溶胶光学厚度有很好的关联性。     

蒙特卡罗方法对各向异性介质辐射特性的模拟

本文提出一种计算含微粒半透明介质辐射特性的蒙特卡罗方法，考虑了微粒群的独立多次散射，直接用米氏相函数考虑微粒的各向异性性质，计算了含微粒层的双向反射率与双向透射率。与实验数据和离散座标法的计算结果比较，吻合良好。     

非均匀介质红外辐射传输模型

本文建立镜反射不透明表面下,非均匀光学物性纯吸收性介质内的红外辐射传输模型.红外辐射在折射率连续变化的介质内沿曲线传输.将非均匀介质沿厚度方向离散成n个物性均匀的等温微层,每个微层内辐射沿直线传播,光滑曲线传输路径即离散成首尾相连的折线系列.采用多层辐射传输模型,利用射线踪迹法建立非均匀介质内的红外辐射传输模型.在多层模型中,相邻两微层间的界面引入折射/全反射判据,避免了界面处的积分奇异现象和原本不存在的界面反射现象.     

毫米波回旋超辐射的粒子模拟与实验研究

为开发回旋超辐射在毫米波和亚毫米波超辐射高功率微波源中的优势,采用3维PIC粒子模拟对回旋超辐射的工作特性进行了分析,并在此基础上优化设计了器件结构及工作参数范围。模拟表明,微波峰值功率与电子束脉宽在一定范围内成平方关系,符合超辐射的典型特征。初步实验在210 kV, 250 A的电子束参数下获得了6 MW的微波峰值功率输出,工作频率37.2 GHz,模式为TE01,与粒子模拟的结果基本一致。     

毫米波回旋超辐射的粒子模拟与实验研究

 为开发回旋超辐射在毫米波和亚毫米波超辐射高功率微波源中的优势,采用3维PIC粒子模拟对回旋超辐射的工作特性进行了分析,并在此基础上优化设计了器件结构及工作参数范围。模拟表明,微波峰值功率与电子束脉宽在一定范围内成平方关系,符合超辐射的典型特征。初步实验在210 kV, 250 A的电子束参数下获得了6 MW的微波峰值功率输出,工作频率37.2 GHz,模式为TE01,与粒子模拟的结果基本一致。     

基于模糊控制的无人水面艇直线路径跟踪方法

针对直流电机驱动固定双桨的无人水面艇,提出一种基于模糊控制的直线路径跟踪方法;利用无人水面艇到目标路径的垂直距离以及无人水面艇的实际航向与给定路径方向的差值来确定无人水面艇的当前状态,根据模糊推理的方法实时调整左右两侧推进电机的输入电压,进而改变无人水面艇的运动状态,实现无人水面艇自主直线路径跟踪;模糊控制器采用双输入双输出的控制结构,无需建立精确的控制器模型,在无人水面艇初始位置相对于跟踪直线的不同位置关系情况下进行了仿真实验,并与PID控制器的性能进行了比较,仿真结果表明:在初始航向偏差角较大时,如2π/3、π时,该方法克服了采用固定参数PID控制方法时出现的大迴转现象;在初始航向偏差角较小时,如π/4、3π/7、π/2时,该方法在超调量以及调节时间方面的直线跟踪性能优于固定参数PID控制方法。     

灰渣的有效光学常数及辐射特性

灰渣中各种成分对光学常数的影响不可忽略,本文基于电磁场平均的有效介质理论,利用Maxwell-Garnett、Bruggeman理论分别计算了人工合成灰渣的有效光学常数和辐射特性参数.计算结果表明有效介质理论适用于计算多组分合成灰渣的有效光学常数.针对本文所计算的合成灰渣,Bruggeman理论计算的平均辐射特性参数与实验值的相对误差较小.     

8mm波段含水量对砂土辐射特性影响研究

毫米波技术应用的基础是物体在毫米波波段的辐射特性的差异,但现阶段物体在毫米波波段的辐射特性的研究缺乏相关理论和试验验证支撑,因此进行了8mm波段砂土辐射特性和含水量相关关系的建模和仿真研究,通过菲涅尔折射定律及理想介质面波的连续性推导出了理想介质面的反射率计算公式,然后利用该公式进行了8mm波段水面辐射特性和含水量对砂土辐射特性影响的仿真,最后通过测量和计算增加砂土含水量对砂土辐射特性影响的定性试验进行仿真结果的定性验证。试验结果和仿真结果一致,砂土随着含水量的增加发射率在下降,砂土的亮温在下降,通过这一结论可以通过砂土亮温的变化定性反演出砂土含水量的变化,从而为毫米波技术在监测含水量等方面的应用提供一定的理论研究和试验验证支撑。     

基于激光雷达和毫米波云雷达的卷云特性分析

使用美国ARM计划安徽省寿县站2008年的微脉冲激光雷达和毫米波雷达的观测数据对寿县上空卷云的宏观物理特性进行了分析,联合两种雷达观测卷云扩大了卷云的边界轮廓,得到更为全面的卷云信息,结果表明了联合激光雷达和毫米波雷达观测卷云的必要性。在此基础上,对观测期间寿县上空的卷云个例进行统计分析,结果显示：卷云过程的平均云底高度分布在5~10 km,其中6~7 km范围所占的频率最大;平均云厚的分布范围为0.25~5 km,其中90.8%分布在0.5~2.5 km;卷云过程持续时间总体上随着持续时间的增大呈减少的趋势,持续时间最长为35.5 h,平均为3.6 h,持续时间小于5 h的卷云过程占82.5%。     

介质保护膜在表面等离子体波探测器中的应用研究

基于表面等离子体波共振技术的探测器中金属膜通常与被探测物直接接触,在金属膜和被探测物之间增加一层介质膜,可以对金属膜进行保护.为了优化探测器的设计,通过对四层共振结构中表面等离子体波共振吸收峰随保护层厚度及其介电常数变化的计算,得到了对保护层参量的选择条件.     

Millimeter Wave Gunn Diode Oscillator Design Based on FDTD Method*

In this paper, a millimeter wave Gunn diode oscillator is analyzed and designed by the finite-difference time-domain (FDTD) method. The design results indicate that the oscillator has an oscillation frequency of 45.0GHz and a higher oscillation voltage. Based on the circuit equations and an integral transform, an improved matrix method is utilized for the oscillator design. This method is also extended to model the hybrid network which is constructed by the high order linear elements and the nonlinear elements with arbitrary connections. The experience shows that the improved FDTD method is stable with the time step length Δt based on the Courant condition. *This work was supported by the National Natural Science Foundation of China.     

A Multilayer Waveguide Window for Wide-Bandwidth Millimeter Wave Tubes

A multilayer waveguide window is demonstrated to exhibit wide bandwidth and high transmission for applications in high-frequency microwave tubes. A transfer matrix approach is employed to discretize the dielectric function profile of the multilayer heterostructure in a rectangular waveguide. The closed form has been obtained and the corresponding reflection and transmission characteristics have been carried out. The analytical calculation is also compared with the result of numerical simulation via the finite-element code HFSS. The exact calculation agrees with the numerical simulation very well. By comparison, the approach not only enhances the accuracy and efficiency, but also gives a good criterion for the design. The results show that the bandwidth for a transmission of 99%, i.e., S ₁₁ below –20 dB, can be optimized to be about 8.75 GHz at a central frequency of 35 GHz or about 25%. A wide-bandwidth waveguide window can be easily designed for Ka-band and W-band tubes, and even for higher frequency ones.     

Research on Propagation Characteristics of Millimeter Wave in Tunnels

This paper analyzes the propagation characteristics of the millimeter wave in various circular section tunnels. The received power, path loss and delay spread are discussed in detail using the verified software of Wireless InSite. The investigated tunnel models with circular section include the long straight tunnel, the tunnel with train inside and the curved tunnels with different curvature. The simulated results are verified by the experimental value in the actual tunnel. Several valuable conclusions are obtained, which would offer theoretical and practical references for the millimeter wave communication in limited spaces.     

蒙特卡洛法模拟G型辐冷器抛物面屏辐射的新算法

提出了筛选法模拟辐射能束随机发射位置的新算法 ,解决了模拟 G型辐冷器抛物面屏这种立体曲面辐射能束随机发射位置的难题 ,并以切平面为发射基础 ,推导出辐射能束随机发射方向的求解算法。通过上述算法 ,模拟了辐射过程 ,计算了相应的耦合因子 ,并对结果进行了误差分析。计算结果表明 ,基于新算法的蒙特卡洛法准确模拟了 G型辐冷器辐射过程 ,计算精度高、速度快     

Dual-Band Bi-Directional Pattern Reconfigurable Fractal Patch Antenna for Millimeter Wave Application

A novel dual-band bi-directional reconfigurable antenna based on Koch patch is presented in this paper. By controlling the switches in the slots etched on the Koch patch, different far field bi-directional patterns at the dual-band around 60 GHz/80 GHz could be achieved. And full azimuthal coverage at this dual-band is possible by electronically controlling the switches in the slots of the patch. This work was supported by the National Natural Science Foundation of China (No. 60371008, No. 90505001) and the CRT Program of UESTC.     

Transmission Line Model Based CAD of Multilayer Dielectric Filters

A systematical procedure for multilayer dielectric filter design is introduced here based on the transmission line model (TLMBCAD). By this procedure, low-pass, high-pass, and band-pass filters can be designed in the same way. The transmission line model works well and is time efficient not only for normal incidence of linearly polarized wave but also for oblique incidence wave with circular polarization. Design examples are given for low-pass and band-pass filters. Simulation results show that the method developed in this paper is valuable for the engineering design of multilayer dielectric filters.     

Cloud Attenuation in Millimeter Wave and Microwave Frequencies for Satellite Applications over Equatorial Climate

A propagation experiment has been carried out at Penang using the SUPERBIRD-C satellite beacon. Cloud occurrences were observed during different months and it is seen that the low cloud occurrences over Penang is very significant from October to January. The cloud attenuation results that are presented, which include the testing of models, have been obtained from the data gathered over five years. The specific attenuation of radio wave due to clouds at various frequencies 12 GHz, 20 GHz, 75 GHz, 50 GHz and 100 GHz has been estimated whereby the values varies from 0.14 dB/km at 12 GHz to 10.1 dB/km at 100 GHz.     

Fast Stimulation of Millimeter Wave Waveguide Filters by Boundary Marching Method

The boundary marching method is applied for the analysis of the waveguide bandpass filers. The vector finite element method with the perfectly matched layers (PML) as the matching load is given for parameter extraction of millimeter wave filters. The implementation of the fast boundary marching method is described in detail. The reflection and insertion losses of millimeter wave filters are obtained and compared with those obtained from literature.     

European Minor Constituent Radiometer: A New Millimeter Wave Receiver for Atmospheric Research

EMCOR is a heterodyne receiver for the frequency range of 201 to 210 GHz. It has been designed for ground-based measurements of various minor constituents of the stratosphere involved in ozone chemistry. Since the aim was the detection of faint spectral lines, a superconducting tunnel junction has been chosen as mixer element and special care has been taken in developing the calibration unit of the system. The front-end is completed by a quasi-optical system, a solid state local oscillator with electronic tuning and a HEMT pre-amplifier. In the back-end an acousto-optical spectrometer is employed to analyse the signal. A PC controls the whole system. The instrument has been installed at a high mountain site in the Swiss Alps.