An empirical HBT large‐signal model for CAD

A new, simple heterojunction bipolar transistor (HBT) large‐signal model for use in CAD is proposed and experimentally evaluated. The important development in this model is that the main model parameters are derived directly from the measurements taken during typical operating conditions. The model was evaluated with extensive measurements at different temperatures by DC, S, and power‐spectrum measurements. Good correspondence was obtained between the measurement and experimental results. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13, 518–533, 2003.     

Fundamental analysis of harmonic reflection in microwave frequency triplers

Harmonic reflection is a vital technique for microwave frequency multiplier design, including the design of frequency triplers. In this article, principles of frequency tripler design with reflector networks are analyzed via harmonic‐balance simulation of an idealized MESFET/HEMT transistor model. The use of an idealized model allows fundamental mechanisms of 3f0 output power and conversion‐gain improvement via reflector networks to be characterized. Several reflector configurations are analyzed including: a 3f0 input reflector; a f0 output reflector; and a combination of both reflectors. The effects of reflector offset length on tripler performance are analyzed in terms of conversion gain, output power, reflected power, and time‐domain waveforms. As a result of this work, a greater understanding of harmonic‐reflector networks and their importance to tripler design is achieved. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

移动多跳中继网络中的混合式认证延时性能分析

首先分析了在移动多跳中继(Mobile Multihop Relay,MMR)WiMAX网络中,新的移动中继(Relay Station,RS)节点在进入网络之前存在的两种认证方案:集中式和分布式接入认证方案。接着在这两种接入认证方式的基础上,提出了一种新的混合式认证方案。然后使用排队论对集中式和混合式认证方案在不同中继节点分布下的认证延时性能进行了分析。最后数值分析结果表明,混合式认证方案相较于集中式认证方案在认证延时性能方面具有更大的优势。     

A reliable model for global planning of mobile networks

In this paper, we propose a global model for WiMAX networks planning. This model represents the network planning problem and helps to solve it entirely without dividing it into several subproblems. The objective of the model is to minimize the cost of the network while maximizing its survivability. The model has been compared to a sequential model with the same constraints, which consists in solving the subproblems sequentially, and to a global model without reliability constraints. The results show that the proposed model performs on an average 25% better than the other models.     

WiMAX技术中OFDMA上行链路载波频偏补偿算法研究*

在OFDMA上行链路中,由于多个用户的载波频率偏差（CFO）破坏了载波间的正交性,从而在基站接收端产生多用户间干扰（MUI）。针对这个问题提出了一种能够实现载波频偏补偿的低复杂度迭代信号处理算法。仿真结果表明,这种算法能有效消除MUI,改善了WiMAX上行链路的传输性能。     

Investigations of resolution limits for indirect microwave holographic imaging

This work describes how indirect holography which has previously been applied to the determination of antenna radiation patterns can be adapted for the imaging of passive objects. It provides details of how complex scattered field values can be obtained in a simple and inexpensive manner from sampled scalar intensity measurements taken over a single scanning aperture. This work uses indirect holographic techniques to image a number of simple objects including a rectangular metallic plate, a small metal plate covered by a dielectric sheet and a small metallic circular annulus. This work demonstrates that good quality images can be reconstructed from simple scalar intensity patterns. It demonstrates that clear outlines can be obtained in particular from reconstructed phase patterns and that good images can be obtained from objects with dimensions of the order of a half wavelength. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

微波技术在烟支湿度检测中的应用

分析了微波技术的烟支湿度检测原理,并据此设计了一种微波测湿系统.试验结果表明：微波测湿技术具有快速、连续、不与被测物接触、无污染、检测精度高等优点.     

微波水分测量的研究

为了能快速、准确地检测物料中的水分含量,设计了一种微波水分检测系统。该系统的工作原理是基于微波透射过含水物料后,其功率变化、衰减量等与物料水分含量有关。该系统工作的中心频率是10.5 GHz;对温度变化、物体颜色及所含盐分等不敏感;水分测量范围可达5%~30%;测量精度为±1%;微波发射功率为10mW。该系统适合检测纸板、布等有一定厚度物料中的水分含量。     

用于天线罩电厚度测量的小型微带六端口反射计

六端口反射计广泛用于高精度反射系数测量,若采用小型测量网络作为测量探头,它可用于天线罩电厚度的无损检测,本设计为一个用于此目的的六端口反射计,该反射计主要由微带对称五端口双环网络与多分支线微带定向耦合器组成,借助于Microwave Office软件对这两部分进行优化与仿真设计,实际电路测试结果表明,此微带六端口反射计在较宽的频带内具有高的测量精度,且由于体积小,可方便地用于天线罩电厚度测量.     

基于前馈模糊逻辑的微波功率控制设计与分析

描述和设计了一类生产陶瓷载体的大型微波干燥控制系统;针对微波干燥过程中微波功率控制不准确、产品缺陷率高的问题,分析了过程变量与控制变量之间的关系特点,并在现有算法基础上,设计了一种基于前馈模糊逻辑的微波功率控制模型;最后对此控制模型设计算法,并应用于实际进行实验分析,得出了很好的效果。     

用于天线罩电厚度测量的小型微带入端口反射计

六端口反射计广泛用于高精度反射系数测量，若采用小型测量网络作为测量探头，它可用于天线罩电厚度的无损检测，本设计为一个用于此目的的六端口反射计，该反射计主要由微带对称五端口双环网络与多分支线微带定向耦合器组成，借助于Microwave Office软件对这两部分进行优化与仿真设计，实际电路测试结果表明，此微带六端口反射计在较宽的频带内具有高的测量精度，且由于体积小，可方便地用于天线罩电厚度测量。     

基于光子技术的微波频率测量研究进展

微波频率测量及分析在军用、民用领域中有着重要战略地位和重大需求,并随着通信、雷达、电子对抗中工作频率的不断攀升而面临着前所未有的挑战。近年来以微波光子学为基础的光子型微波频率测量技术应运而生,因其在瞬时带宽、抗电磁干扰方面有着显著优势,得到了长足发展,并具有重要的理论意义和实用价值。针对目前主要研究的光子型微波频率测量方案,如微波光子扫频方案、频率 幅度映射方案、频率 空间映射方案、频率 时间映射方案、光子压缩感知方案、以及数字化测频方案等,介绍了其基本原理及实验方案,并对各种方案的研究现状与进展进行了梳理、分析和总结。最后,对光子型微波频率测量的趋势和前景进行了简要探讨和展望。     

A low profile tunable microwave absorber based on graphene sandwich structure and high impedance surface

In this article, a low profile dynamically tunable microwave absorber is proposed, which consists of high impedance surface and graphene sandwiched structure. We theoretically demonstrate and experimentally verify that the proposed absorber can provide a dynamically tunable reflection range from larger than ?3 dB to less than ?30 dB at operating center frequency of 11.2 GHz. The entire thickness of this absorber is only 2.8 mm, nearly one tenth of working wavelength. In addition, a modified equivalent circuit model is proposed to explicate its absorption mechanism. At last, we fabricate a prototype absorber, measure its reflection coefficient in anechoic chamber. The experimental results agree well with the full wave simulation results. This work may provide a reference for design and fabrication of dynamically tunable microwave absorber based on large‐scale graphene and may promote the actual applications of graphene at microwave frequency.     

移动WiMAX网络中跨层快速切换的研究*

针对移动WiMAX网络中,基于FMIPv6和DAD (duplicate address detection)机制的快速切换存在着开销大和检测时延长的问题,提出了一种跨层快速切换的策略。新策略在FMIPv6基础上,使用了mSCTP协议和ODAD (optimistic DAD)机制,成功地消除了FMIPv6协议中建立隧道的开销和减少了DAD地址检测的时延。仿真结果显示,新的切换策略将切换时延和分组丢失分别降低了65%和60%。     

有机薄膜器件的镀膜自动控制系统设计

设计了用于有机薄膜器件的镀膜自动控制系统;整个自动控制系统以单片机为核心,可分为3个功能模块:人机交互、强弱电转换、样品处理。人机交互由单片机来实现;强弱电转换由固体继电器来完成;样品处理包括镀膜速率自动控制和样品保护两个部分。控制系统体现了弱电控制强电的设计思路,系统采用了单片机、继电器、电磁阀和可调变阻器等器件以及程控可调电阻电路。所设计的控制系统能克服目前有机薄膜器件镀膜系统的一些弊端,实现镀膜和镀膜速率的自动控制,并且能够避免有机半导体材料在真空腔内的相互污染。     

干涉式微波辐射计成像算法以及天线阵采样方案分析

对旋转扫描干涉式微波辐射计成像算法进行研究,提出了基于伪极网格傅立叶变换的成像算法,利用一维插值以及一维FFT即可实现图像重建,既提高了成像精度,又保证了成像速度。以3种8单元天线排列方案阵为例,利用本文方法和基于线性插值的笛卡儿网格方法分别进行成像模拟,模拟结果验证了本文方法的优越性,同时表明天线阵排列方案对成像结果影响很大,天线阵基线均匀性越好,数量越多,成像质量就越好。直线阵无法实现基线数量与均匀性的统一,而平面阵可以在较好均匀性情况下实现最多的基线数,是天线阵排列的首选方案。     

用GPM数据进行青藏高原雪水当量监测可行性分析

在二阶积雪散射模型模拟结果的基础上,针对GPM的数据特点,提出一种利用Ku波段不同入射角下积雪散射特征差异进行雪水当量监测的方法,并以TRMM/PR数据为例,对青藏高原部分特征地区进行了分析,证实了该方法在理论上的可行性。     

微梁结构热偶微波功率传感器芯片的制作工艺

在微波技术研究中，微波功率是表征微波信号特性的一个重要参数，微波功率测量已成为电磁测量的重要部分，可应用于很多场合，如发射机输出功率（包括天线系统辐射的功率）和振荡器输出功率的测量，毫瓦计的校准，标准信号发生器的校准等。微波功率传感器是微波功率计探 头中的核心元件。微染结构热偶微波功率传感器芯片选择具有低电阻温度系数的Ta2N和高热电功率塞贝克系数的Si作为热 材料，利用半导体工艺和MEMS工艺制作，并最终研制成合格的芯片，芯片具有尺寸小，功耗低，灵敏度高，频带宽等特点，简要介绍了芯片的结构原理，并详细介绍了芯片的制作工艺。     

土壤中钙键和铁/铝键结合的有机碳差异的比较

为研究矿质元素在有机碳矿化中所起的作用,以棕壤、黄棕壤、红壤为供试土壤,比较了不同利用方式和施肥处理土壤中钙键、铁/铝键结合的有机碳的差异。结果表明,从北至南的地带性土壤(棕壤、黄棕壤和红壤)系列中,全钙及与有机碳结合的钙依次降低,钙键结合的有机碳占有机碳总量的比值依次升高;铁/铝键结合的有机碳及其占全碳的比值依次升高。与自然土壤相比,耕作土壤在不施肥条件下,钙键有机碳、铁/铝键有机碳占有机碳总量的比值增加,且铁/铝键有机碳占有机碳总量比值的增加率始终比钙键有机碳占有机碳总量比值的增加率要高;覆膜比不覆膜时铁/铝键有机碳占有机碳总量比值的增加率比钙键有机碳占有机碳总量比值的增加率高得多。这表明,与全土有机碳相比,有机碳矿化稳定性由高到低依次是铁/铝键有机碳、钙键有机碳、全土有机碳。     

Small signal modeling of GaAs PIN diodes aided by electromagnetic analysis

A systematic procedure is described for determination of GaAs PIN diode equivalent circuit models from measured S‐parameter data combined with an electromagnetic analysis of the feed structure. A new parasitic and intrinsic model topology is proposed, and found to be better suited than prior models for the particular GaAs PIN structures considered in this work. Models were developed for forward bias currents ranging from 0.01 to 100 mA, and example measured and modeled results are included to validate the approach. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 61–68, 2001.