【作者】 孙璐；

【导师】 王家礼；

【作者基本信息】 西安电子科技大学 ， 测试计量技术及仪器， 2010， 博士

【摘要】 本论文课题来源于“微波毫米波测试仪器基础研究”项目,作为其中的一个子课题,子课题题目为“微波非线性电路建模方法的研究”。随着微波半导体电路在通信、雷达、电子和仪器仪表等方面的广泛应用,如何准确和高性能的设计和分析微波电路是非常关键的。半导体器件模型是影响电路设计精度的最主要因素,电路规模越大、指标和频段越高、对器件模型的要求也越高。因而准确的器件模型对提高射频和微波毫米波电路设计的成功率、缩短电路研制周期是非常重要的。根据微波电路的工作条件,它常常工作于高功率大信号条件下,电路状态处于强非线性情况,传统的小信号S参数等表征和建模方法已经不能准确表征其模型,而器件大信号模型不易获取。伏特拉级数、幂级数及等效电路方式常常表征电路的弱非线性状态,强非线性电路状态也不能准确表示。论文在总结传统大信号电路的表征、测量方法和建模方法的基础上,分析了各种测量和建模方法的适用条件、特征和优缺点,并分析了对于微波电路建模的一般步骤。针对以往大信号模型的一些问题,引入了非线性散射函数这一表征微波大信号电路的频域黑箱模型。论文研究了非线性散射函数模型的线性化,上下标标注方式的引入,各个非线性散射函数元素物理含义的分析和描述,散射函数与传统小信号S参数的相互推广。对其它非线性网络函数的定义,非线性散射函数与其它非线性网络函数的相互关系,网络连接的非线性网络函数和子网络的非线性网络函数的关系进行了研究和探讨,研究结果为这一模型的正确使用奠定了理论基础。此外,开发了基于数字示波器的非线性散射函数提取系统及系统误差的校准方法,为准确提取功率器件的非线性散射函数模型提供了实验条件,并经过测试得到了功率场效应管和二极管的非线性散射函数变化趋势,测试结果正确反映出功率器件随激励信号功率增大的非线性输出变化规律。研究了非线性散射函数模型与近年来美国Agilent公司提出的X参数模型从定义、性质、提取方法和使用等方面的联系和区别,为散射函数模型的研究和应用提供了有益的参考和比较。在功率器件的非线性散射函数测量数据基础上,采用支持向量机这一新的机器学习方法对散射函数模型做预测建模,得到了较好的预测精度,分析了支持向量机形式选择、核函数选择、参数选择对建模精度的影响。最后采用场效应管和肖特基势垒二极管的散射函数模型来设计微波功率放大器和倍频器,验证了模型的适用性。与传统大信号模型相比,这一模型的优点主要在于易于与小信号S参数相兼容,通过这一模型可以建立起大信号和小信号工作条件下的微波电路的统一模型;与目前国外的非线性网络测量系统不同,测量方法采用数字示波器为基础的时域测量方法,测试简单方便,采用通用测试夹具可以对各种微波半导体电路用统一的方法来测量提取散射函数模型;这一模型是频域黑箱模型,不需要预知微波半导体器件和电路的电路结构就可以提取出散射函数模型,模型不止包含本征模型部分,对于寄生参数的影响也被包含在了这一黑箱模型中,并可以将其用于微波电路的设计中,方法通用,精确度高。实践证明,非线性散射函数这一新的微波器件大信号模型,对有效提高微波非线性电路的设计效率、提高设计准确度和性能具有重要的意义。为微波大信号电路的高效设计和研发提供了一种新的思路。此外,对于散射函数提取中相位一致性不好问题的改善;夹具去嵌问题的研究和实现;支持向量机对部分非线性散射函数建模精度不高以及如何将散射函数模型设计为可供通用CAD软件调用的统一微波电路大信号模型等问题,仍是需要深入研究和探讨的问题。更多还原

【Abstract】 As a sub-topic named“Research of microwave nonlinear circuit modeling method”, this paper is derived from the project of“Basic research of microwave and millimeter wave test equipment”.With the wide use in communication, radar, electronics and instrumentation,how to accurately design and high-performance analyze microwave semiconductor circuits is very important. Models of semiconductor devices are the main factor to affect the accuracy of the circuit design. Larger the circuit , higher the frequency, to the higher requirements of the device models. It is critical of the accurate device models to improve the design of RF and microwave millimeter-wave circuit and shorten the development cycle. According to the working conditions of microwave circuits, which are often working in high-power and large-signal, the circuit is in a strongly nonlinear. Traditional characterization and modeling methods of S parameters at small-signal can not represent them accurately, while the large-signal device model is not easy to obtain. Volterra series, power series and the equivalent circuit approach is often used in a weak non-linear state of the circuit, to the strong non-linear circuits it can not be an accurate representation.Based on the traditional large-signal circuit characterization, measurement and modeling methods, it is analyzed that the application, characteristics, advantages and disadvantages of a variety of methods. General steps of microwave circuits modeling are summarized. As some problems of traditional modeling methods, the frequency domain black-box model of nonlinear scattering function is introduced.First, the research is focused on the linearization of nonlinear scattering function model, introduction of the upper and lower standard labeling methods, analysis and description of the physical meaning to the element of nonlinear scattering function and the interchangeable of the traditional S parameters. Secondly, it is concluded that other description of the nonlinear network functions, the relationship between nonlinear scattering function and other nonlinear network function and the relationship between nonlinear network function of the network link and the sub-network. The results of them have laid a theoretical basis for the proper use of this model.Then, it is developed the extraction system of nonlinear scattering function based on the digital oscilloscope and the calibration methods of system errors. This system provided the experiment conditions to the extraction of nonlinear scattering function model of power devices. Nonlinear scattering function of power FETs and diodes can be tested and the results accurately reflected the nonlinear variation with the increase of input power to the power devices.Links and differences of the model of nonlinear scattering function and the model of parameters X are proposed by Agilent recently are analyzed. Through the comparison of the description、characteristic、extraction methods and the applications between them, it provides a useful reference and comparison to the study and application of nonlinear scattering function.Based on the test data of nonlinear scattering function of power devices, the new machine learning method of support vector machine is used to predict the model of nonlinear scattering function and the good predict accuracy is got. Then, it is summarized that the affection to the modeling accuracy from the selection of the support vector machine, kernel function and other parameters.Last, the model of nonlinear scattering function of FETs and Schottky barrier diodes are used to design the microwave power amplifier and frequency multiplier. It is verified that the applicability of the large-signal model.Compare with the traditional large-signal model, the advantages of this black-box model can be generalized. The first is the compatibility with the parameters S at small signal. Through this, the unified microwave circuit model can be established between the working conditions of large-signal and small-signal. Different from the foreign NNMS(Nonlinear network measurement system), the second is the time domain measurement method based on the digital oscilloscope. This method is simple and convenient. Adopting the common test fixture, a unified method can be used to exact the nonlinear scattering function model. The last, the model is frequency-domain black-box model, it can be extracted which is not needed to know the structure of microwave semiconductor devices and circuits in advance. The model not only contains some of the intrinsic part, and the affection of parasitic parameters is included in this model. It can be used in the design of microwave circuits conveniently and accurately.It can be proved that this new large-signal model of microwave devices can improve the design efficiency, improve design accuracy and performance effectively.In addition ,some problems, such as how to improve the consistency problem to the phase of nonlinear scattering function; modeling accuracy is not high to the part of nonlinear scattering function using support vector machine and how to design a unified large signal CAD(Computer aided design) model with the model of nonlinear scattering function, still requires in-depth study and explore.更多还原