基于缝隙波导的多频微波加热研究

微波因其高效、绿色无污染等优点在加热领域应用广泛,但加热均匀性差限制了它的进一步发展。本文基于波导缝隙天线理论和磁控管的非线性响应特性,设计了一个以波导缝隙阵列天线为辐射器的加热系统。利用磁控管的非线性响应特性输出多个频率的微波以丰富电磁场的模式,设计了基于横向缝隙波导和纵向缝隙波导的两种辐射器,建立了微波加热的多物理场模型,以模拟多个频率的微波通过缝隙波导加热物体的效果,并分析了不同参数如缝隙、频差等对加热均匀性及效率的影响。     

PIN光电探测器等效电路模型研究

本文给出一个新的PIN光电二极管的等效电路模型，该模型基于速率方程和微波端口特性并在TMS（TsinghuaMicrowaveSpice）中完成，可以进行线性、非线性信号分析和噪声分析。利用该模型对其非线性谐波特性进行了预测，模拟结果表明和文献数值求解结果基本一致，最后讨论了适用于金属－半导体－金属（MSM）光电二极管的修正模型．     

一种915 MHz和2450 MHz双频微波加热分析

微波加热作为一种新型的加热方式在许多领域中得到了广泛的应用,与传统的加热方法相比,微波加热具有高效节能、选择加热、清洁无污染等特点。多源微波加热结构是实现微波均匀高效加热的有效手段,也是微波加热领域未来的发展趋势。在工业应用的多源微波加热腔体中,保证加热效率的同时如何提升加热均匀性始终是该领域的研究重点。本文在现有微波加热模型的基础上,提出了一种新型的双端口双频微波加热模型。本文基于有限元方法的多物理场仿真软件COMSOL Multiphysics 5.4设计了一种915 MHz和2450 MHz的双频微波加热模型,通过端口之间的正交和缝隙滤波器的设计减少了两个端口之间能量的互相耦合,在保证加热效率的同时提高了加热的均匀性。     

微波场效应功率放大器的CAD技术

微波场效应晶体管功率放大器的计算机辅助设计与分析技术关键是微波非线性电路的分析方法和功率场效应管器件模型的建立。本文在概述微波ＧａＡｓ ＦＥＴ ＣＡＤ、ＣＡＡ基本原理基础上，着重阐述了分析微波非线性电路的频域谐波平衡法，接着介绍了一个直接从ＧａＡｓＦＥＴ小信号Ｓ参数建立其大信号模型的新方法，上述技术可望在微波功率场效应放大器的批量研制中得到应用。     

基于缝隙辐射器的腔内四分区定向加热研究

分区定向加热能够实现腔内任意方向的定向加热控制，且可以加热多种食材。本文设计一种耐高温、功率容量大的缝隙辐射器，并根据该缝隙辐射器设计了一个腔内四分区分时定向加热系统。首先设计了一种耐高温、便于生产加工的缝隙辐射器，利用其组成辐射器阵列，并根据波的叠加原理推导出每个辐射器的相位，以实现腔体中的分区指向，从而达到腔内四分区分时定向加热的目的；随后通过耦合电磁场和热传递方程建立了微波加热的多物理场模型，分析了在腔内的微波定向性能，最后搭建实验系统，利用温度计测量实验结果，以验证腔内四分区分时定向加热的效果。     

基于数值仿真的多馈微波加热温度控制系统

针对常用多模腔加热的不均匀性,对多馈口微波加热进行了研究,提出了一种基于数值仿真分析来设计微波加热系统的方法。通过建立1/2 全尺寸有限元模型进行仿真计算,分析了馈口数量对微波加热的影响,在此基础上采用Bang-Bang 控制策略设计了加热系统。其中,圆柱形谐振腔模型的高度为800 mm,半径为395 mm。腔体周围环形布置10个微波源,通过德拜模型仿真温度变化和测量值进行对比,验证了仿真模型的正确性。不同馈口数的COMSOL仿真结果表明,馈口数为4时,温度变异系数(COV)为0.0897,相比于一个馈口的情况,温度的均匀性提高了10.5%。通过实验测试了微波加热系统性能,实验结果表明,媒质温度能得到合理控制。     

基于双通道固态源的腔内三分区加热研究

微波加热在医疗、食品加工等特殊领域应用广泛,但是很难工程上实现对任意方向的定向加热的控制.本文基于线性相控阵天线理论,设计了一个双通道固态源的腔内三分区指向加热系统,该系统通过调节固态源各通道间的相位差以实现腔体内的微波指向从而达到三分区定向加热的效果.同时,本文通过耦合电磁场和热传递方程建立了微波加热的多物理场模型,...     

一种微波辅助的气固耦合模型

针对微波辅助加热情况下气固热耦合及气固反应应用,设计了一种利用微波加热多孔固体介质(碳化硅)来间接加热气体的气固耦合模型,并利用有限元仿真软件进行建模。通过对电磁场、流体传热场、自由和多孔介质这3个物理场的耦合仿真,验证了此气固耦合模型的准确性和可行性;分析了该模型在不同石英管半径、不同多孔介质孔隙率和不同气体流速情况下的S参数和加热情况。结果表明,当碳化硅的孔隙率为0.5,石英管的半径为20 mm时,微波转换效率最高,微波能量利用率达到90%以上。     

微波加热装置打火问题的电磁仿真

以某型号微波加热装置为代表,根据传输线多重反射原理和小反射原理,提出了一种改善微波加热装置打火问题的新方法:首先对微波传播路径上的波导管结构进行优化,研究微波加热装置波导管结构参数对每一阶段反射系数的影响,找到影响每一阶段反射系数的最优参数,组成一个反射最小的波导管结构,再利用凸包对微波加热装置的整体阻抗进行匹配,从而达到改善微波加热装置打火问题的目的。进一步的测试研究证实了该方法对微波加热装置打火问题改善的有效性。     

MPCVD中基片加热材料的温度场摄动模型研究

为改进微波等离子体化学气相沉积（MPCVD）装置中的加热系统，提出了用基片加热材料替代常规加热方式的新的技术路线，建立了基片加热材料的微波轴对称温度场模型并得到了一般解，通过对基片加热材料的微波设计，在MPCVD装置中获得大片基片台直径的均匀温度分布区。     

管道式固体材料微波加热装置的仿真设计*

为了解决工业上固体材料在微波加热过程中普遍存在的能量不集中、效率低、加热不均匀的问题,提 出了一种管道式固体材料微波加热装置的设计方案。利用多物理场仿真对固体材料微波加热均匀性影响因素进行 分析,并优化了微波馈入装置的分布和管道结构,仿真表明该装置具有较好的加热均匀性和较高的效率。基于优化 后的设计,计算了褐煤在微波加热时的温度分布情况,其温度场的变异系数COV 值达到0.166,表明温度分布具有 良好的均匀性。该装置实现了对褐煤的微波均匀加热,对固体材料微波加热的工业应用具有指导意义。     

A survey of the present state of microwave transistor modeling and simulation as applied to circuit design

A comprehensive overview of recent approaches to microwave transistor modeling and simulation is presented. Three basic approaches to semiconductor device modeling are compared: the linear two-port model, the device-physics model, and the equivalent circuit model. Equivalent circuit models are discussed in detail with examples. Good solutions to the problem of linear modeling have been found and several authors have been able to predict the noise and gain of microwave transistors in the linear operating regions. However solutions for nonlinear operation of transistors at microwave frequencies have only recently been implemented and much room for improvement remains.     

Neural-based dynamic modeling of nonlinear microwave circuits

A neural network formulation for modeling nonlinear microwave circuits is achieved in the most desirable format, i.e., continuous time-domain dynamic system format. The proposed dynamic neural network (DNN) model can be developed directly from input-output data without having to rely on internal details of the circuit. An algorithm is developed to train the model with time or frequency domain information. Efficient representations of the model are proposed for convenient incorporation of the DNN into high-level circuit simulation. Compared to existing neural-based methods, the DNN retains or enhances the neural modeling speed and accuracy capabilities, and provides additional flexibility in handling diverse needs of nonlinear microwave simulation, e.g., time- and frequency-domain applications, single-tone and multitone simulations. Examples of dynamic modeling of amplifiers, mixer, and their use in system simulation are presented.     

一种基于神经网络的微波器件快速建模方法北大核心CSCD

随着微波器件结构复杂度的增长和产品性能要求的提高,微波器件建模不仅要能够描述其理想电磁特性,还要能快速准确反映多物理参数对器件性能的影响。虽然神经网络已经被引入到微波器件领域,但是将其应用于器件的多物理特性建模的研究还比较少。文章提出了一种基于人工神经网络的多物理参数建模方法来表示输入输出变量之间的非线性关系。提出了一种高效的神经网络多物理参数模型,并针对该模型引入了一种新的训练算法。所提出的模型可以快速准确地预测微波器件的多物理响应,如滤波器的S参数特性曲线、离子敏感场效应晶体管的输出特性曲线等。与有限元方法相比,此方法可以节省约98%的计算成本与99%的计算时间,为实现快速高效的微波器件行为级建模提供一种可行方法。     

Coupled electromagnetic-thermodynamic simulations of microwave heating problems using the FDTD algorithm

A practical implementation of a hybrid simulation system capable of modeling coupled electromagnetic-thermodynamic problems typical in microwave heating is described. The paper presents two approaches to modeling such problems. Both are based on an FDTD-based commercial electromagnetic solver coupled to an external thermodynamic analysis tool required for calculations of heat diffusion. The first approach utilizes a simple FDTD-based thermal solver while in the second it is replaced by a universal commercial CFD solver. The accuracy of the two modeling systems is verified against the original experimental data as well as the measurement results available in literature.     

TLM simulation of microwave sintering of ceramics using SiC stimulus.

Microwave heating technology is becoming a successful technique used for sintering ceramic materials. However, various aspects of sintering experiments, such as the use of process stimulus and the preparation of sample arrangements, depend mainly on human expertise. The Transmission Line Matrix (TLM) method is first used to solve the combined electromagnetic and thermal equations modeling microwave heating of dielectric materials. It is then used to simulate microwave sintering of a low-loss ceramic material in a multimode microwave cavity. To enhance the microwave sintering process, Silicon Carbid (SiC) was first used as a susceptor and in a picket fence arrangement. As multiple samples may be processed in a microwave oven, the TLM was used to model such a process, and the introduction of SiC as a stimulus was also examined. Results show the importance of the stimulus thickness and configuration on the uniformity and density of the electromagnetic field distribution and, therefore, on the power dissipation within the ceramic load.     

The nonlinear operation of a microwave crossed-field amplifier

A nonlinear, three-dimensional, partial differential equation modeling the operation of a microwave crossed-field amplifier is discussed and analyzed where the nonlinearity is considered weak. Amplification mechanism, amplification range, and phase characteristics are discussed. Predicted results are compared with experimental data.     

Straightforward and accurate nonlinear device model parameter-estimation method based on vectorial large-signal measurements

To model nonlinear device behavior at microwave frequencies, accurate large-signal models are required. However, the standard procedure to estimate model parameters is often cumbersome, as it involves several measurement systems (DC, vector network analyzer, etc.). Therefore, we propose a new nonlinear modeling technique, which reduces the complexity of the model generation tremendously and only requires full two-port vectorial large-signal measurements. This paper reports on the results obtained with this new modeling technique applied to both empirical and artificial-neural-network device models. Experimental results are given for high electron-mobility transistors and MOSFETs. We also show that realistic signal excitations can easily be included in the optimization process.     

Nonlinear statistical modeling and yield estimation technique foruse in Monte Carlo simulations [microwave devices and ICs]

A novel nonlinear statistical modeling technique for microwave devices and a new approach to yield estimation for microwave integrated circuits are presented. The statistical modeling methodology is based on a combination of applied multivariate methods with heuristic techniques. These include principal component analysis and factor analysis in conjunction with maximally flat quadratic interpolation and group method of data handling. The proposed modeling approach, when applied to the database of extracted equivalent circuit parameters (ECPs) for a pseudomorphic high electron mobility transistor device, has proven that it can generate simulated ECPs, S-parameters, that are statistically indistinguishable from measured ones. A new yield estimation technique based on a Latin hypercube sampling (LHS) is also demonstrated. The LHS-based simulation is utilized as an alternative to primitive Monte Carlo (PMC) simulation in yield analysis. An equally confident yield estimate based on the LHS method requires only one-fourth of those simulations needed when the PMC technique is used     

基于多物理场计算的微波加热能量转换分析

近年来,微波能的应用在食品、化工、医疗等方面越来越广泛,特别是微波加热技术在日常生活中充当着重要角色,得到了学者们的广泛关注。然而,关于微波加热机理的基础研究并不多,而且相对较为深奥,难于理解掌握。因此,通过COMSOL multiphysics建立简易微波加热模型,以水为被加热对象,研究了其在微波作用下的电场及温度分布情况,并通过计算分析了其中的能量转换关系,使得对微波加热机理的阐释通俗易懂。