基于神经网络的无线通信系统RF电路设计方法

典型的无线通信系统RF电路由大量的线性和非线性元器件组成。建立这些微波电路元器件的模型在现代RF电路的设计中至关重要。采用一种神经网络来学习非线性电路的动态特性,并建立相应的模型。神经网络模型可以对原始电路的模拟特性进行整体预测,可用于高层电路的仿真和优化。以功率放大器为例验证了神经网络模型的实用性,表明神经网络模型可以极大地提高无线通信系统RF电路的建模精度和速度。     

A novel multi-fidelity coupled simulation method for flow systems

For the numerical simulation of flow systems with various complex components, the traditional one-dimensional (1D) network method has its comparative advantage in time consuming and the CFD method has its absolute advantage in the detailed flow capturing. The proper coupling of the advantages of different dimensional methods can strike balance well between time cost and accuracy and then significantly decrease the whole design cycle for the flow systems in modern machines. A novel multi-fidelity coupled simulation method with numerical zooming is developed for flow systems. This method focuses on the integration of one-, two-and three-dimensional codes for various components. Coupled iterative process for the different dimensional simulation cycles of sub-systems is performed until the concerned flow variables of the whole system achieve convergence. Numerical zooming is employed to update boundary data of components with different dimen-sionalities. Based on this method, a highly automatic, multi-discipline computing environment with integrated zooming is developed. The numerical results of Y-Junction and the air system of a jet engine are presented to verify the solution method. They indicate that this type of multi-fidelity simulationmethod can greatly improve the prediction capability for the flow systems.     

A nonlinear equivalent circuit method for analysis of passive intermodulation of mesh reflectors

Passive intermodulation(PIM) has gradually become a serious electromagnetic interference due to the development of high-power and high-sensitivity RF/microwave communication systems, especially large deployable mesh reflector antennas. This paper proposes a field-circuit coupling method to analyze the PIM level of mesh reflectors. With the existence of many metal–metal(MM) contacts in mesh reflectors, the contact nonlinearity becomes the main reason for PIM generation. To analyze these potential PIM sources, an equivalent circuit model including nonlinear components is constructed to model a single MM contact so that the transient current through the MM contact point induced by incident electromagnetic waves can be calculated. Taking the electric current as a new electromagnetic wave source, the far-field scattering can be obtained by the use of electromagnetic numerical methods or the communication link method. Finally, a comparison between simulation and experimental results is illustrated to verify the validity of the proposed method.     

噪声调制连续波雷达信号波形射频隐身特性

雷达信号波形的射频(RF)隐身性能是雷达系统能否适应现代战场环境的重要因素,雷达射频隐身信号波形设计是现代雷达系统设计中的重要课题.首先,在介绍随机噪声信号雷达原理的基础上,基于Schleher截获因子阐述了噪声调制连续波雷达信号波形的射频隐身特性.然后,分析了高斯噪声相位和频率调制连续波雷达输出自相关函数和高斯噪声相...     

Continuous transverse stub technology

Military and civil radar and communication systems utilize phased array antennas that require hundreds or, in some cases, thousands of transmit/receive (T/R) modules. T/R modules, even when low cost, drive the total RF system cost to an undesirable level, resulting in fewer systems being purchased, This paper reviews the application of continuous transverse stub (CTS) antenna technology to reduce the number of T/R modules required and, thus, the overall RF system cost, and military and civil applications and their respective cost savings     

并联混合动力齿轮传动涡扇发动机建模与性能分析

为对比探究未来大推力航空混合动力系统与传统航空发动机的优劣,本文依托某概念型齿轮传动涡扇(Geared turbofan,GTF)发动机,设计了一个并联航空油-电混合动力系统(hybrid GTF,hGTF),在Matlab /Simulink数字仿真软件中建立相匹配的电动力模型以及氮氧化物NOx排放和噪声预测等性能参数计算模型,并在稳态和飞行任务剖面下初步分析了电动力系统的引入对原基线GTF发动机的性能改变状况。稳态仿真结果表明,大推力等级的并联油-电混合动力系统中,至少需要兆瓦级的电动力系统进行匹配;当电动力系统处于电动模式时,可能会带来低压压气机喘振的隐患;当电动力系统处于再生模式时,电能源相当于经过了电能到机械能再到电能的二次效率损失,不建议采用。飞行任务剖面动态仿真结果表明,相比于传统GTF发动机,hGTF推进系统的燃油消耗率最高下降15%,总燃油消耗节省8.3%, NOx总排放量减少18.8%,各部件起飞噪声总声压级减少1.5~3.3dB。分析结果表明采用并联混合动力系统具有显著提升省油、减排效果的能力,同时也具有一定的降噪潜力。     

装备虚拟保障系统的概念及其技术框架

针对传统的装备保障系统仿真存在的不足,在理解保障系统的物理意义的基础上提出了虚拟保障系统的概念,分析了虚拟保障系统的特点和优点,提出了虚拟保障系统的技术框架,其主要包括保障对象建模、系统任务建模、保障系统建模、离散事件仿真和可视化仿真。在建模过程中考虑了实体的三维模型,包括保障对象和保障系统中的资源实体,构建了保障任务的虚拟设计环境。最后讨论了虚拟保障系统的运行与评价方法,可在装备的研制阶段和使用阶段为保障系统的设计、分析和评价提供技术手段。     

Functional models for space power electronic circuits

Presented here is a new approach to model power electronic components so that system level issues of large space power systems can be studied. To demonstrate this approach, the models for two major power electronic components in the space station power system are described. The new models are useful not only in system level studies but also in the design/analysis of particular components     

分布式电推进飞机动力系统评估优化方法

以电推进飞机的动力系统作为研究对象,开展了以下研究工作：采用电力系统潮流计算方法,分析了采用高压直流供电体制的分布式电推进飞机电气系统,模拟了其在稳定运行状态与断路故障状态下的能量流动关系,同时分析了直流电压等级对电气系统的影响。搭建了完整的分布式电推进飞机动力系统仿真模型,依据基于时间和基于高度的飞行剖面,对比分析了纯电推进与涡轮电推进架构在推进功率、推进效率与航程3个评价指标上的优劣。建立了动力系统典型部件的参数化模型,并使用符号规划算法对建立的参数化模型进行了优化计算,比较了传统涡轮推进与涡轮电推进架构下动力系统质量与燃油消耗率间的优化权衡关系。研究结果为分布式电推进飞机混合动力系统的设计提供了有价值的正向设计方法。     

一种基于模型和原型系统仿真的综合模块化航空电子系统开发方法

针对综合模块化航空电子系统的复杂性和传统瀑布式开发方法存在的问题与挑战,在Ⅴ型开发模型的基础上提出了一种基于模型和原型仿真的综合模块化航空电子系统的开发方法.该方法通过在需求捕获、方案设计和工程开发阶段分别构建相应的原型系统进行仿真与验证,实现对系统需求进行早期需求确认与设计验证(V&V)、原型仿真与集成.采用该方法的好处是通过原型仿真,系统设计师可以在开发早期向用户展示他们的设计成果,以满足用户的需求;可以帮助系统开发人员以低成本实现连续的虚拟集成和迭代确认与验证,从而缩短系统研制周期,降低系统开发成本.飞行管理系统开发应用案例表明了该方法有效性.     

残差滤波及其在密集多回波环境下机动多目标跟踪中的应用

 修正概率数据关联滤波（MPDAF）是目前解决密集多回波环境下机动多目标跟踪较为有效的方法,但当回波密度增高时,该方法容易失跟。本文针对此特点,在MPDAF基础上,提出了残差滤波（RF）方法,分别从理论和Monte carlo仿真两方面揭示了RF与数据关联的内在机理,结果表明该方法能大幅度提高跟踪滤波器捕捉目标和剔除关联域内多余回波的能力以及跟踪的性能,是一种解决高密集多回波环境下机动多目标跟踪的有效方法。     

基于RF-SVR的燃油计量装置性能衰退检测和剩余寿命估计方法

为了实现航空发动机燃油系统的安全状态监测和健康管理,开展了燃油系统性能衰退检测和剩余使用寿命估计方面的研究。以燃油系统燃油计量装置为例,分析了其主要的性能衰退模式,设计了基于电流-速度数据的健康指标(HIs)选取方案,并考虑环境及模型参数不确定性,进行模型不确定性仿真,基于健康数据与性能衰退数据间的马氏距离对部件性能衰退进行检测。提出了基于随机森林-支持向量回归(RF-SVR)的剩余使用寿命(RUL)估计方法,利用通过RF特征选择优化的SVR模型实现部件RUL估计。最后基于某型民用涡扇发动机机械液压模型仿真数据对该方法进行了验证,结果表明:该方法的性能衰退检测虚警率及漏报率低于2%,RUL估计误差低于3%,可为航空发动机燃油系统的预测性维护提供参考。      

Dynamic modeling and simulation of a pressurized system used in flight vehicle

For a typical pressurized system with a novel dual-stage gas pressure reducing regulator, a system model is established with modular models of various typical components. The simulation study on the whole working period shows that the general trends and magnitudes of simulation curves are in agreement with experimental measured curves. As the key component in the pressurized system, the regulator is studied by a series of numerical simulations to reveal the influences of various structure parameters on its stability. Furthermore, the variable ranges which can guarantee the stability of regulator and system are obtained to provide guidance for design. The modeling and analysis approach can be applied to other systems and components.     

A Methodology for Computing Link Availability

An efficient and systematic numerical technique is presented for predicting availability of an RF link between a ground station and a communication satellite. This new methodology takes into account the effects of weather and time-varying link geometry caused by satellite motion as well as the customary ground/satellite link parameters. The availability computed under the worst link geometry (5 deg elevation) has been compared with the average availability computed with the new methodology. The results indicate that the traditional worst-case design approach is too pessimistic to provide a realistic design criterion where links operate at K band or above.     

A Survey of Electronic Attitude Measurement Systems

Introducing rectangular coordinates for the reference coordinate system and the space-vehicle fixed-coordinate system, it will be shown that the transformation matrixes between both coordinate systems which describe the attitude of the space vehicle can be easily computed as functions of the rectangular coordinates of two precise directions known in both coordinate systems. In detail, an electronic attitude measurement will be described based on two precise propagation directions of RF waves. In order to measure the propagation direction in the space-vehicle fixed-coordinate system, a very general interferometer is described. This interferometer is characterized by the fact that the antennas of the interferometer are arbitrarily distributed on the surface of the space vehicle and that the electronic computation of the coordinates of the propagation direction of an RF wave is extremely simple. The design and some modifications of this system are discussed     

Flight-critical distributed systems: design considerations [avionics]

With the proliferation of so-called "smart" components and the availability of small, low-cost, and high-speed data networks, avionics that have traditionally been centralized are becoming distributed. A distributed approach offers many potential benefits, such as reduced development time and cost, simplified system installation, increased flexibility for system expansion or modifications, and greater reuse of proven components. The distributed approach can also reduce the risk associated with design errors by splitting complex hardware and software into more manageable components. However, distributed systems also introduce new challenges in meeting real-time deadlines and providing fault tolerance. This paper examines the many design considerations and identifies the strengths and weaknesses of each. Emerging automotive drive-by-wire alternatives are compared for application to aerospace systems. This paper is based on a Draper Laboratory-sponsored effort to look at flight-critical distributed systems and to evaluate emerging hardware and software for building them.     

载人航天器推进系统健康监测的组件技术研究

为了适应载人航天器推进系统多发动机的分布式结构,提高健康监测系统的可靠性,应用组件技术构造了分布式多智能组件集成的健康监测系统,给出了组件之间的协调修正和决策算法。原型系统仿真结果表明,该技术比传统的面向对象（ＯＯＰ）技术更适用于分布式系统,可应用于载人航天器推进系统的健康监测。     

射频离子推力器热特性仿真分析

为了分析射频离子推力器热特性，建立了射频离子推力器整体热模型，基于二维流体模型，对11cm射频离子推力器开展了放电室等离子体仿真，获得了电子温度、电势分布等关键参数；以等离子体仿真结果和实测束电流为输入，获得了各热源的热通量；通过有限元计算获得了关键部组件的温度分布，与实验结果进行了对比分析。研究结果显示：放电室内电子温度约为3.6eV~3.9eV，等离子体电势最高20V，发热损耗主要来自带电粒子轰击放电室壁面和栅极造成的能量沉积、激发原子的热辐射以及射频线圈自身的发热损耗，温度仿真与实测结果一致性良好，最大误差7%，仿真得到的温度分布可以作为输入参数进一步研究栅极受热形变及对束流的影响。     

Formal verification and legacy redesign

Sustaining weapons system hardware and software represents a significant and ever-increasing portion of total system cost. Hardware components are becoming obsolete much sooner while weapons system lifetimes are increasing, We must identify more cost-effective solutions to engineering and reengineering these subsystems. Verifying and validating weapons systems are two of the most costly parts of either engineering process. Traditionally, hardware validation and verification is done by simulation and testing, In the past few years, math- and logic-based formal methods tools have begun to scale up to and be applied successfully to real-world problems. Incorporating formal verification methods into engineering and reengineering processes will cost-effectively and significantly improve the level of trust and the quality of our weapons systems. Formal methods are especially well suited for redesigning current weapon systems which have become unsupportable due to component obsolescence because they help minimize the astronomical costs of rigorously reverifying the reengineered components. We believe that formal methods are an important tool for effective engineering of future weapon systems     

高超声速飞行器俯冲段制导控制一体化设计方法

针对高超声速飞行器高速俯冲飞行段制导控制系统设计问题,建立了俯冲飞行段制导控制一体化低阶设计模型,提出了一种新颖的六自由度(6DoF)制导控制系统设计方法。基于目标-飞行器三维空间相对运动模型和坐标系转移关系建立了三维全耦合俯冲相对运动模型,推导得到了飞行器加速度在弹道坐标系三轴的分量与飞行器三通道角速率间的解析模型,进而结合飞行器绕质心动力学模型建立了以气动舵偏角为控制输入的俯冲飞行段制导控制一体化低阶设计模型。该制导控制一体化低阶设计模型降低了俯冲飞行段制导控制系统的模型阶数,减少了六自由度制导控制系统的设计参数,省略了传统设计方法中根据期望过载反求气动欧拉角的过程;同时利用解析模型替代了传统方法中姿态控制环路的跟踪控制过程,简化了制导控制系统的设计流程,为制导控制一体化设计提供了一种新的分析思路。数值仿真结果验证了本文提出的制导控制一体化设计方法的有效性和鲁棒性。