Development of VHDL‐AMS neuro‐fuzzy behavioral models for RF/microwave passive components

The new generation of System‐on‐Chip (SoC) incorporates digital, analogue, RF/microwave and mixed‐signal components. Such circuits impose to reconsider the traditional design methods. Mixed‐signal designers need novel design methodologies which will have to include accurate behavioral libraries of devices and processes into hierarchical design flows. Thus, this paper describes a behavioral modeling approach which generates neuro‐fuzzy‐based models for RF/microwave devices. The models, so obtained, can be easily integrated into a VHDL‐AMS simulator. This modeling approach is applied to a microwave tunable phase shifter and it is illustrated by the development of a VHDL‐AMS model library for RF/microwave applications. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Fuzzy neural‐based approaches for efficient RF/microwave transistor modeling

In today's RF and microwave circuits, there is an ever‐increasing demand for higher level of system integration that leads to massive computational tasks during simulation, optimization, and statistical analyses, requiring efficient modeling methods so that the whole process can be achieved reliably. Since active devices such as transistors are the core of modern RF/microwave systems, the way they are modeled in terms of accuracy and flexibility will critically influence the system design, and thus, the overall system performance. In this article, the authors present neural‐ and fuzzy neural‐based computer‐aided design techniques that can efficiently characterize and model RF/microwave transistors such as field‐effect transistors and heterojunction bipolar transistors. The proposed techniques based on multilayer perceptrons neural networks and c‐means clustering algorithms are demonstrated through examples. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Advanced automotive thermal management – Nonlinear radiator fan matrix control

Advanced automotive cooling systems for gasoline and diesel engines can improve the powertrain performance. The replacement of the mechanical driven coolant pump and radiator fans with computer controlled servo-motor actuators, and update of the wax-based thermostat valve with a 3-way variable position smart valve, allow the coolant flow rate and proportion directed through the radiator to be carefully adjusted. A smart thermal management system approach can regulate the forced convection heat transfer process to match the engine׳s cooling needs. This paper presents a Lyapunov based nonlinear control strategy to solely operate the radiator fan matrix for transient engine temperature tracking. A reduced order mathematical model serves as the basis for the closed-loop feedback system. An adaptive backstepping method was implemented to derive the control law. An experimental test bench with multiple radiator fans, heat exchanger, wind tunnel, coolant pump, three way valve, and engine thermal load has been fabricated. Representative numerical and experimental tests demonstrate that the advanced control strategy can regulate the engine temperature tracking error within 0.12 °C and compensate the unknown heat load. The nonlinear controller provided superior performance in terms of power consumption and temperature tracking as evident by the reduced magnitude when compared to a classical PI with lookup table based controller and a bang bang controller.     

一种新型MEMS微波功率传感器的理论模型与优化设计

提出了一种新型的MEMS微波功率传感器.与传统的结构相比,新结构具有测量误差小、设计简单、使用方便等显著优点.然后在全面考虑了热传导、热对流、热辐射三种传热机制的基础上,对传感器的主要部分即热电堆建立了热模型,进而导出了灵敏度、时间常数、噪声的理论解析式.最后根据拉格朗日乘数法原理,以给定的时间常数和噪声大小为约束条件,求得灵敏度达最大时热偶长度和串联数目的最佳值.     

Object oriented microwave circuit simulation

An object‐oriented microwave circuit simulation environment is described. The design of the program is intended to offer flexibility without sacrificing efficiency. Recent developments in object‐oriented techniques and in C++ compilers are used to obtain a flexible and robust system ideally suited to the development of a global modeling strategy for the integration of circuit, field, thermal, and mechanical analyses. The simulation of spatial power combining systems is used as a vehicle to illustrate the architectural developments of the system. © 2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 164–182, 2000.     

Evolutive design assistance tool for microwave circuits

This article deals with the development of a design assistance environment for microwave circuits and, especially, its first module dedicated to microwave power amplifiers. This tool does not intend to simulate nonlinear circuits, since CAD tools are already available and reliable. Our aim is to implement efficient and predictive design processes and design re‐use capabilities based on specialized knowledge databases (devices, circuits, and methods). © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 293–305, 2003.     

Enhancement of time domain analysis and optimization through neural networks

An efficient computational approach to time domain microwave design and optimization is presented. In particular, artificial neural networks are coupled with a full‐wave time domain simulator in order to model and optimize microwave structures. Furthermore, neural networks are used to predict the late time response from the early time response of a structure to accelerate the convergence of time domain simulations, particularly in the case of high‐Q structures such as filters and resonators. The combination of neural networks with a time domain TLM solver is demonstrated by means of a design example of an iris‐coupled band pass filter. The results demonstrate the dramatic gain in speed and numerical efficiency enabled by this approach to optimizing and modeling microwave devices. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Hybrid modeling of microwave devices using multi‐kernel support vector regression with prior knowledge

This article proposes a support‐vector hybrid modeling method of microwave devices when only a small number of measurements are available. In this method, a hybrid model of microwave device has been obtained by combining a coarse model and a support‐vector model, where the coarse model is complemented by a support‐vector model capable of correcting the difference between the measurements and the coarse model. The support‐vector model was developed using a novel algorithm. In the algorithm, multi‐kernel and prior knowledge from a calibrated simulator were incorporated into the framework of the linear programming support vector regression by utilizing multiple feature spaces and modifying the optimization formulation. The experimental results from two microwave devices show that the hybrid modeling can enhance the physical meaning of the support‐vector model and improve the modeling accuracy for a small dataset, and that the proposed algorithm shows great potential in some applications where sufficient experimental data is difficult and costly to obtain, but the prior knowledge from a simulation model is available. The hybrid modeling is suited to a microwave computer‐aided design tool or an automatic tuning robot. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:219–228, 2015.     

开槽波导功率合成技术分析

在毫米波频段实现基于固态微波器件的高功率放大器,功率合成是一项不可或缺的技术。介绍了一种基于开槽波导耦合微带1分8的功率分配合成网络。这种结构的主要优点是具有较好的集成度,较高的功率合成效率,还可以为功率单片微波集成电路（MMIC）提供效率比较高的散热。通过软件仿真分析,该结构具有较好的功率分配能力和隔离度。     

Efficient optimum seismic design of reinforced concrete frames with nonlinear structural analysis procedures

Performance-based seismic design offers enhanced control of structural damage for different levels of earthquake hazard. Nevertheless, the number of studies dealing with the optimum performance-based seismic design of reinforced concrete frames is rather limited. This observation can be attributed to the need for nonlinear structural analysis procedures to calculate seismic demands. Nonlinear analysis of reinforced concrete frames is accompanied by high computational costs and requires a priori knowledge of steel reinforcement. To address this issue, previous studies on optimum performance-based seismic design of reinforced concrete frames use independent design variables to represent steel reinforcement in the optimization problem. This approach drives to a great number of design variables, which magnifies exponentially the search space undermining the ability of the optimization algorithms to reach the optimum solutions. This study presents a computationally efficient procedure tailored to the optimum performance-based seismic design of reinforced concrete frames. The novel feature of the proposed approach is that it employs a deformation-based, iterative procedure for the design of steel reinforcement of reinforced concrete frames to meet their performance objectives given the cross-sectional dimensions of the structural members. In this manner, only the cross-sectional dimensions of structural members need to be addressed by the optimization algorithms as independent design variables. The developed solution strategy is applied to the optimum seismic design of reinforced concrete frames using pushover and nonlinear response-history analysis and it is found that it outperforms previous solution approaches.     

Thermal analysis of microwave GaN‐HEMTs in conventional and flip‐chip assemblies

Temperature rising which originates from self‐heating degrades the electrical characteristics, reliability, and lifetime of high‐power GaN‐HEMTs. In this article, a systematic analytical approach for thermal evaluation of microwave GaN‐HEMTs is constructed through combining and scrutinizing some of the basic static thermal analysis methods to provide a deeper insight into the process of the channel temperature rising and self‐heating with a much lower computational burden. The proposed systematic thermal analysis has been applied to two different assembly methods: conventional mounting and flip‐chip mounting. Although the mathematical and empirical equations used are simple enough to save time, the effects of several phenomena and different conditions on the channel temperature have been taken into account. These include heat crowding phenomenon, the effect of temperature‐dependent thermal conductivity of the transistor constituent materials, transistor geometry, die‐attach material properties, and bump dimensions. To validate the accuracy of the calculations, all the analytical analyses are followed by 3D thermal simulations in ANSYS software. The simulation results confirm the accuracy of the analytical calculations.     

Optimization of Bio-Implantable Power Transmission Efficiency Based on Input Impedance

Recently, the inductive coupling link is the most robust method for powering implanted biomedical devices, such as micro-system stimulators, cochlear implants, and retinal implants. This research provides a novel theoretical and mathematical analysis to optimize the inductive coupling link efficiency driven by efficient proposed class-E power amplifiers using high and optimum input impedance. The design of the coupling link is based on two pairs of aligned, single-layer, planar spiral circular coils with a proposed geometric dimension, operating at a resonant frequency of 13.56 MHz. Both transmitter and receiver coils are small in size. Implanted device resistance varies from 200 Ω to 500 Ω with 50 Ω of stepes. When the conventional load resistance of power amplifiers is 50 Ω, the efficiency is 45%; when the optimum resonant load is 41.89 Ω with a coupling coefficient of 0.087, the efficiency increases to 49%. The efficiency optimization is reached by calculating the matching network for the external LC tank of the transmitter coil. The proposed design may be suitable for active implantable devices.     

Robust model predictive control for a nanofluid based solar thermal power plant

Among the several technologies for solar energy recovery, parabolic solar collectors have emerged as one of the most promising due to their performance, which can be enhanced if nanofluids are employed as heat transfer fluids instead of the traditional alternatives. The inherent time-dependent behavior of solar radiation profiles forces the solar thermal plants to be operated aided with controllers able to reject these strong disturbances. While traditional controllers can be employed for this aim, more advanced techniques such as Model Predictive Control are suggested since this optimal-control based method can be tuned to minimize operating costs, among some other features. The main objective of this work is to implement an MPC controller to a nanofluid-based solar thermal power plant in order to evaluate its performance to reject disturbances on the solar radiation profile in an efficient manner. An off-line nonlinear programming optimization was deployed so we could compare the response of the on-line MPC implementation on a strict enough basis. Furthermore, the performance of MPC controllers is affected by how well does the modeling of the system is able to stick to reality, thus, it is important to test if the controller is robust enough to deal with uncertainty that might be introduced as modeling errors. Results indicate that MPC controllers are suitable for their implementation on these kinds of power plants since they steer the system to achieve desired conditions by smoothly manipulating the decision variable, even in the scenarios where a substantial cascade-effect modeling error was imposed in the parameters of the nanofluid.     

Doherty功放的贝叶斯正则化神经网络逆向建模研究

针对直接逆向建模方法精度低、稳定性差等缺点,提出了一种采用规则化函数为L1/2范数的贝叶斯正则化神经网络逆向建模方法,L1/2正则化使得网络结构具有稀疏性,能够缩小网络的规模、加快网络的训练速度,用贝叶斯正则化方法可以使网络的输出更加平滑,提高网络的稳定性和泛化能力。将此方法应用到Doherty功率放大器的设计中,在已知Doherty主功放效率、输出匹配端的S11和S21的情况下,分别仿真得出相对应的输出功率和f,可以简化设计过程。实验结果表明,此逆向模型求得的输出功率、与S11相对的f、与S21相对的f比直接逆向建模方法的均方误差分别减少了8.83%、9.30%和9.00%,运行时间分别减少了99.34%、99.40%和99.23%,解决了设计中的多解问题,可用于设计射频微波器件。     

电除尘器高压供电优化控制仿真研究

随着我国新颁布的火电厂大气污染物排放标准(GB13223-2003)的实施, 对电除尘器高压电源在节能与优化控制方面提出了更高的要求.根据电除尘器典型运行工况要求, 建立了电除尘器高压供电优化控制数学模型.以这些数学模型为基础, 采用遗传算法进行了电除尘器高压供电优化控制的仿真研究, 最终开发出能指导电除尘高压电源的设计与运行的优化控制仿真软件.分析和数值仿真结果表明, 通过实施从后级电场向前级电场逐级调节供电参数的方法,可使电除尘器高压电源的节能与优化控制性能达到最佳状态.     

一种太阳能集热系统集热量实时预测的混合建模方法

太阳能集热器的集热量受光照度、环境温度、风速等多种因素的影响,其预测模型很难从预测精度和实时性上同时满足用户需求。本文提出一种实时预测太阳能集热系统集热量的混合建模方法。该方法首先从能量守恒出发,根据热管式太阳能集热系统传热机理推导出集热量的理论模型,并把理论模型中的散热系数、透射率、吸收率等经验参数以及采光面积、散热面积等几何参数集总为模型的未知参数,进而提出混合模型的结构。然后,利用TRNSYS仿真软件搭建太阳能集热器模拟仿真系统,对仿真系统不同的运行工况进行仿真实验,获取用于辨识混合模型未知参数的稳态数据。最后,选用粒子群优化算法（PSO）作为模型参数的辨识方法,利用所获得的稳态数据辨识模型的未知参数。模型预测值与仿真实验结果的比较表明,预测模型简单而精确,能够在各种工况下实时地、高精度地预测太阳能集热器的集热量,其平均相对误差可达到2.02%。该模型在太阳能热泵、太阳能热水器等系统的优化控制领域得以广泛应用。     

Bandwidth scavenging for device coexistence in pervasive computing systems

Opportunistic Spectrum Access in a pervasive computing system can enable a set of secondary user devices to access unused spectrum, or whitespace, found between the transmissions of a set of primary user devices. The design objective for an efficient secondary user access strategy is to be able to “scavenge” spatio-temporally fragmented bandwidth while limiting the amount of disruption caused to the primary user devices. In this paper, we propose an access strategy which is based on measurement and modeling of the whitespace as perceived by the secondary user devices. A secondary user device continually monitors and models its surrounding whitespace, and then accesses the available spectrum so that the effective secondary throughput is maximized while the resulting disruption to the primary user devices is limited to a pre-defined bound. We first develop analytical expressions for the secondary throughput and primary disruption, and then perform ns2 based simulation experiments to validate its effectiveness under various topologies, user traffic profiles, and secondary user populations.     

An analytic method of microwave bipolar single‐frequency and voltage‐controlled oscillator design

An analytic method of microwave bipolar oscillator design, allowing one to define explicit expressions for optimum values of feedback elements and load through bipolar transistor Z‐parameters, is developed. A negative resistance concept is utilized to design series feedback microwave bipolar oscillator with optimized feedback elements and maximum output power in terms of the transistor impedance parameters. The design of the wideband common‐base bipolar voltage controlled oscillators (VCOs) is also presented. Numerical and experimental results verify the validity of the design methods described. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 403–414, 1999.     

核电站KIT系统改造中的反应堆热功率监视功能开发

该文主要涉及大亚湾核电站KIT系统升级改造中与反应堆热功率监视功能开发相关的内容。热功率监视模块接收来自反应堆一回路的温度、压力、流量等信号,计算反应堆的实时热功率和滑动平均热功率,对热功率进行实时显示并设置报警功能。该文从改造背景、功能需求、计算原理、功能应用等方面对热功率监视模块的设计开发进行了描述。     

Experimental investigation on a parabolic trough solar collector for thermal power generation

Developing solar thermal power technology in an effective manner is a great challenge in China.In this paper an experiment platform of a parabolic trough solar collector system(PTCS) was developed for thermal power generation,and the performance of the PTCS was experimentally investigated with synthetic oil as the circulate heat transfer fluid(HTF).The solar collector's efficiency with the variation of the solar flux and the flow rate of the HTF was identified.The collector efficiency of the PTCS can be in ...