晶体管/集成运放/仪器仪表的等效输入噪声模型研究

本文从理论上给出了单管前置放大器,集成放大器,仪器仪表的通用等效输入噪声模型,并给出了快速测得该模型参数的方法。有此模型,使得仪器仪表的NF 图等描述噪声性能的参数或图表将变得非常简捷而容易。     

新型伺服电机功率放大器

本文介绍一种由计算机驱动的直流伺服放大器,具有价廉、高效等优点。这种放大器设计在很大程度上克服了交迭畸变和功耗问題。与传统的推挽放大器不同,这种设计要有四路电源,并由四个独立的高阻抗输出级给出电流。     

STM中锁定放大器的研制

介绍STM中应用锁定放大器的原理,并给出销定放大器一种简单的移相电路及其它电路的设计考虑.     

高精度光电耦合放大器及其在8098测控系统中的应用

对一种4路输入高精度高稳定性光电耦合放大器进行分析,给出该放大器与8098单片机的接口电路,并给出利用此电路对生产现场的4路模拟信号进行放大和A/D转换的程度.实验结果与理论分析一致.该放大器有很好的线性度和稳定性,很有工程实用价值.     

声发射检测仪前置放大器设计

现有前置放大器的带宽为100~300kHz,在测量过程中将一些有用的低频信号滤除了。为此本文设计了一套低频声发射前置放大器,给出电路原理图,并对电路进行了分析与验证。结果表明设计的前置放大器低频截止频率可达到30kHz,改善了声发射检测仪的探测性能,满足设计要求。     

航空发动机静电传感器前置放大器设计

分析了静电监测传感器的原理和信号特点,设计了一种适用于发动机气路静电监测的传感器信号前置放大器,此放大器具有高输入阻抗、低输出阻抗、低噪声、高共模抑制比等特点,并给出了该放大器的电路分析与设计要点。发动机气路模拟实验表明：该放大器可以对微弱信号进行无失真放大,有效地实现对气路静电监测信号的调理,为后续的信号采集和处理奠定了基础。     

一种高速低功耗存储读写控制电路

本文提出了一种高速低功耗存储读写控制电路。该电路采用锁存器型敏感放大器,并将敏感放大器输入与存储器位线通过隔离电路互联,通过控制隔离电路和敏感放大器开启时机,可以有效实现存储器读出速度、读数据功耗和读出可靠性之间的折衷。文章给出的模拟分析结果对存储器设计者有很好的参考价值。     

基于ADS线性射频放大器设计与仿真

为了加速射频放大器的设计及产品化过程,用EDA工具软件对放大器先进行仿真是一种有效的方法.提出了一种利用ADS软件对LNA和小信号功率放大器进行设计的方法,并通过实例对1.5GHz频段射频放大器的稳定性、S 参数、功率增益、输入输出匹配等进行了仿真,给出了仿真结果和最终的设计电路.仿真结果表明,放大器匹配电路设计完全满足性能指标要求.这种方法对放大器的设计有着重要的实用价值,可以进行快速的阻抗匹配和优化,从而加速放大器的设计进程.     

VHF波段60W高效率功率放大器的工程实现

介绍了甚高频(VHF)波段基于BLF647/60W高效率放大器的工程设计与实现方案,在满足总体指标要求下对各级功率放大器的增益进行了合理分配,并在设计中对放大器的效率、带宽和输出功率等指标做了合理的处理。针对关键器件,重点分析了直流偏置电路,输入输出匹配电路,并给出了详细的测试数据,最后介绍了该放大器的散热设计以及在调试过程中需要注意的问题。经测试,各项指标满足要求。     

微波放大器噪声系数精确测量方法的研究与实现

给出了一种自行设计组装的微波放大器噪声系数测量系统,并针对由HEMT组成的微波放大器进行噪声系数测量.从测量技术方法上对常规的二倍功率法进行改进,充分考虑了后级噪声的影响并采取相应的措施加以消除,从而提高了在不同源阻抗下对平均噪声系数和点噪声系数测量的准确性.     

The S.A.G.E. Project

ABSTRACT

This paper describes the process and creation of a library resources and services Web page within WebCT, a course authoring program that is being used to deliver complete course content over the Internet in a distance education program at The Ohio State University. A librarian at the Prior Health Sciences Library was asked to join a faculty team to teach and provide library services for a series of three courses. The students are working health professionals who cannot attend regularly scheduled classes. Illustrations are included of the WebCT course page and the library resources and services page. The initial process and planning are described, and recommendations for future research are identified.     

Fuzzy min-max neural networks. I. Classification.

A supervised learning neural network classifier that utilizes fuzzy sets as pattern classes is described. Each fuzzy set is an aggregate (union) of fuzzy set hyperboxes. A fuzzy set hyperbox is an n-dimensional box defined by a min point and a max point with a corresponding membership function. The min-max points are determined using the fuzzy min-max learning algorithm, an expansion-contraction process that can learn nonlinear class boundaries in a single pass through the data and provides the ability to incorporate new and refine existing classes without retraining. The use of a fuzzy set approach to pattern classification inherently provides a degree of membership information that is extremely useful in higher-level decision making. The relationship between fuzzy sets and pattern classification is described. The fuzzy min-max classifier neural network implementation is explained, the learning and recall algorithms are outlined, and several examples of operation demonstrate the strong qualities of this new neural network classifier.     

A.I.K.E.F.: Adaptive hybrid model for space plasma simulations

The interaction between magnetized space plasmas and obstacles like comets, asteroids or planets is determined by a variety of physical processes that occur simultaneously on significantly different length and time scales. Frequently the dynamics of individual ions play a key role for the shape of the interaction region: strong velocity shear between light and heavy plasma constituents, non-Maxwellian particle distributions due to pick up and asymmetries in the magnetic field topology are crucial in determining this type of interaction. Covering these processes is beyond the scope of any Magnetohydrodynamic (MHD) model. In order to account for these effects we have developed a new adaptive hybrid code A.I.K.E.F. (Adaptive Ion-Kinetic Electron-Fluid). The code operates on Cartesian meshes that can adapt to the physical structures in both, space and time. To the authors' knowledge, there is no other adaptive hybrid simulation code in space plasma physics to the present day. Adaptivity is implemented by means of Hybrid-Block-AMR, that is individual octs are refined rather than entire blocks, where an oct is one eighth of a block. In order to account for a reasonable number of particles in each cell, particles are refined via splitting and merging. Both procedures conserve mass, momentum and kinetic energy. The code is implemented in C++ and efficiently parallelized for distributed systems by means of the Message Passing Interface (MPI). In order to demonstrate the validity of our newly developed code we have applied it to a series of fundamental test scenarios. On the one hand we demonstrate that the dispersion relation as well as the propagation characteristics of MHD and whistler mode waves are quantitatively reproduced by our simulation code. Wave propagation remains unaffected when traveling through regions that include different refinement levels. On the other hand we verify that the results obtained on high resolution uniform meshes are identical to the results from adaptive simulations that use coarse base meshes but include various levels of refinement. A remarkable speedup could be observed: the adaptive simulations required 71 times less CPU-hours than the uniform mesh simulations. Finally, we present a first series of global, three-dimensional simulations for the interaction of Mercury with the solar wind and a real time study of Titan's plasma interaction during a magnetosheath excursion.     

Transient heat conduction problems using B.I.E.M.

A method, using boundary elements, is presented as a solution to plane transient heat conduction. The proposed method considers the governing equation to be a Helmholtz's equation and solves the problem of time variation using step by step integration. A numerical procedure is developed and its effectiveness verified. Several examples are provided and their results compared with the theoretical ones.     

Octree creation via C.S.G. definition

The common method for generating the octrees of complex objects, is based upon generating the octrees of several pre-defined primitives and applying Boolean operations on them. Regardless how the octrees representing the primitives are generated (top-down or bottom-up) the octree of a desired object is obtained by performing Boolean operations among the primitives comprising the object according to the object's CSG (constructive solid Geometry) representation. When carrying out this procedure, most of the computing and memory resources are used for generating and storing the octants comprising the primitives. However, the majority of those octants are not required for the representation of the final object. In this paper the extention of the top-down approach to the CSG level (i.e., generating the octree of an object directly from its CSG representation) is proposed. With this method there is no need to generate the octrees of the primitives comprising the object nor to perform Boolean operations on them. Moreover, only these octants which belong to the final object are generated.     

The application of identification methods in the U.S.S.R.—A survey

The paper is an attempt to describe the use of identification methods in the U.S.S.R. where these develop and extend at a rate comparable to that of the rest of the world. Therefore complete coverage seems to be impossible in one article. Furthermore, many of the methods used in the U.S.S.R. were described in surveys presented to preceding IFAC Congresses and Symposia. Therefore attention is focused on methods which have not been adequately covered in those papers. Relatively much attention is given to adaptive, dispersional, ‘standard’ and distributed models. The essence of each method is described in brief and actual plants are listed where these methods are applied. References are made to papers which describe these methods in more detail. The final part of the paper is a very brief account of other kinds of models and their application.     

HU-PACS. 10 months experience.

An outline of the Hokkaido University PACS (HU-PACS) and 10 months experience of its clinical use are reported. It is concluded that HU-PACS is a useful clinical tool, even though some points still remain to be improved.     

An integrated c.a.d. system for an architects department

The development of computers in a production environment in the building industry has so far been slow, but it is suggested that developments have reached the stage where there are real economic benefits. There are now reasonable prospects of a greatly increased use.     

The 68040 processor. 2. Memory design and chip

For pt.1 see ibid., February (1990). The memory subsystem, the external bus, chip and board testing, and design-verification methods for the 68040, a third-generation, full-32-bit microprocessor in the Motorola 68000 family, are discussed. The internal caches and memory management are examined at length. The external bus protocol, arbitration, snooping, and timing specifications are addressed. The MOVE16 instruction, which moves a cache line from one address (which may reside in the data cache) to another address outside the cache is described. User testing, based on dedicated test logic that is fully compliant with the IEEE 1149.1 standard, and factory testing, for which the processor employs structured design techniques for random logic and special test modes for embedded arrays, are examined. The use of top-down design and a hierarchical method of design verification is discussed     

Systems with finite communication bandwidth constraints. I. Stateestimation problems

In this paper, we investigate a state estimation problem involving finite communication capacity constraints. Unlike classical estimation problems where the observation is a continuous process corrupted by additive noises, there is a constraint that the observations must be coded and transmitted over a digital communication channel with finite capacity. This problem is formulated mathematically, and some convergence properties are defined. Moreover, the concept of a finitely recursive coder-estimator sequence is introduced. A new upper bound for the average estimation error is derived for a large class of random variables. Convergence properties of some coder-estimator algorithms are analyzed. Various conditions connecting the communication data rate with the rate of change of the underlying dynamics are established for the existence of stable and asymptotically convergent coder-estimator schemes