A circuit reduction technique for finding the steady-state solutionof nonlinear circuits

Computing the steady-state response of large nonlinear circuits is becoming a key simulation requirement due to the rapid market growth of RF silicon integrated circuits. In this paper, we describe a nonlinear circuit reduction algorithm for finding the steady-state response. The proposed algorithm uses a congruent transformation-based technique to reduce the harmonic-balance equations into a much smaller set of equations. The main feature of the reduced circuit is that it shares with the original one a certain number of the derivatives with respect to the RF input power, steady-state analysis is then carried out on the reduced circuit instead of the original circuit     

An efficient method for finding DC solutions for Josephson circuits

The formulation of Josephson circuit equations in the DC state is discussed and a mixed-mode approach that combines the nonlinear solution method of source-stepping and time-domain method of numerical integration is proposed. Since Josephson circuit equations are often multivalued, the mixed-mode algorithm follows the paths of the independent sources, detects ill-conditioned points, and converges to stable points on the characteristic curves of the simulated circuit. The algorithm uses a combination of source stepping and transient calculation with resistive damping. An adaption of method to superconducting quantum interference device (SQUID) threshold curve calculation is also discussed. The techniques are suitable and presented in sufficient detail, so that a reader may implement them as part of a general simulation program such as JSIM or SPICE     

On a method for determining limit cycles in nonlinear circuits

A theory for determining the existence, number and position of limit cycles in perturbed Hamiltonian systems, that depends on a small parameter, is presented. The limit cycle emerges from the periodic trajectories surrounding a centre of the unperturbed system. By means of this theory a sinusoidal oscillator with a nonlinear element has been analysed. It is shown that only the terms with odd degrees in the approximation polynomial of the nonlinear element's characteristic exert an influence on the initiation of limit cycles.     

A 4K CMOS gate array with automatically generated test circuits

A 2-/spl mu/m CMOS 4K-gate array using a newly devised scan bus method has been developed. This method is applied to the array by using a double-latch structure, parallel scanning, and normal-test common pin techniques. The gate array can be tested for 95-100% of all DC faults using computer-generated test circuits and test data, without placing restrictions on the logic design. Due to an access-to-output flip-flop structure and a gate-isolated three-input type basic cell, including embedded transistors, the area increase and operating speed degradation due to test circuits are considerably reduced. Furthermore, besides the flip-flop blocks, a built-in RAM macroblock is available. Degradation of operating speed is evaluated as 10%. The scan operation is done at a clock cycle of 120 ns, and the access time of the RAM macroblock is 34 ns. The gate array includes 4032 three-input gates on a 7.2/spl times/7.02-mm chip.     

A dynamic specification to automatically debug and correct various divider circuits

This paper presents a formal technique to verify and debug division circuits on fixed point numbers. The proposed technique is based on a reverse-engineering mechanism of obtaining a high level model of the gate level implementation and also introducing an intermediate representation of the specification that makes equivalence checking between two models possible. The main advantage of this representation is the fact that the specification is dynamically updated according to the information obtained from the implementation. At the end, if two updated models are not equivalent, possible bugs can be localized and then corrected automatically by analyzing the difference, if possible. Experimental results show the robustness of the proposed technique in comparison with other contemporary methods in terms of the run time and also show that two orders of magnitude average speedup is obtained.     

Accurate Fourier transform method for almost-periodic response simulation of microwave nonlinear circuits

A generalised Fourier transform, in which an orthogonal sample selection algorithm is used, is presented for accurate simulation of the almost-periodic responses of microwave nonlinear circuits. The measured and simulated results of a MESFET amplifier show the significant improvement in accuracy.<>     

Fault location for nonlinear resistive circuits

The letter deals with fault location in nonlinear resistive circuits taking the design tolerances of the nonfaulty circuit parameters into consideration. The method described is based on measurements of node voltages at a single test. It belongs to the class of topological methods, and two-terminal as well as m-terminal elements are permitted.     

非线性电路的信号流图分析法

将传统的线性系统的信号流图分析法推广应用于非线性电路，可以获得非线性电路的“通解”及“特解”。该方法使非线性电路有了类似于线性电路的解析解，为非线性电路的分析与设计提供了新的理论和方法。     

A novel method for measurement points selection in access points localization

Precise localization of access points (APs) has become more and more important with the booming of diverse location based services. AP localization accuracy heavily relies on the locations of measurement points. However, collecting abundant information from the APs usually requires tremendous manual efforts, which greatly compromise the efficiency and accuracy of the localization of the APs. Thus, the selection of appropriate measurement points becomes an important issue to achieve a high localization accuracy with a low-cost method, which has not been fully explored in existing research. To this end, we propose a novel approach to select measurement points for AP localization under the assumption that the number of APs to be located is known in advance. Specifically, an initial point is selected randomly and the locations of APs are estimated according to the measured information. Then, subsequent measurement points are determined by locating the intersection of the coverage areas of APs in real time, so that as many APs as possible can be detected at each measurement point. Both simulation and experimental results show that our approach can reduce the number of measurement points while improving the AP localization accuracy.     

汉字签名自动辨识的一种结构描述方法

在充分分析了签名图像的基础上提出了一种针对汉字签名利用结构描述来进行签名自动辨识的方法。其基本思想是在汉字骨架基础上提取构成汉字的各个基本笔段并同时提取表征各笔段的特征值，从而形成带有属性的模式串，以便进行串的比较并根据一定的判断准则给出判断结果。     

A simple method for automatically locating the nipple on mammograms

This paper outlines a simple, fast, and accurate method for automatically locating the nipple on digitized mammograms that have been segmented to reveal the skin-air interface. If the average gradient of the intensity is computed in the direction normal to the interface and directed inside the breast, it is found that there is a sudden and distinct change in this parameter close to the nipple. A nipple in profile is located between two successive maxima of this parameter; otherwise, it is near the global maximum. Specifically, the nipple is located midway between a successive maximum and minimum of the derivative of the average intensity gradient; these being local turning points for a nipple in profile and global otherwise. The method has been tested on 24 images, including both oblique and cranio-caudal views, from two digital mammogram databases. For 23 of the images (96%), the rms error was less than 1 mm at image resolutions of 400 μm and 420 μm per pixel. Because of its simplicity, and because it is based both on the observed behavior of mammographic tissue intensities and on geometry, this method has the potential to become a generic method for locating the nipple on mammograms     

Current-mode digital circuits operating in mixed analogue-digitalsystems

Novel current-mode gates are presented. The current-mode circuits operate with an almost constant current drawn from the power supply, significantly reducing interference with other circuits located on the same silicon die     

A unified approach for teaching basic nonlinear electronic circuits to sophomores

The philosophy, mechanics, and syllabus of a unified sophomore course in nonlinear electronic circuits are offered as a possible solution to the dilemma, long faced by teachers of electronic circuit theory, of a decreasing amount of time in which to present circuits containing an increasing variety of nonlinear electronic devices. The logic and feasibility of teaching the unified principles of nonlinear circuit analysis which are independent of the devices and their internal physical principles of operation, and which require no prerequisite other than elementary calculus, are illustrated with typical examples of various practical large signal electronic circuits actually taught in the course. The necessity to teach only a few fundamental unifying concepts and techniques, and the high motivational value of the proposed approach are shown to be the overriding factors which led-to-the success of this sophomore course at Purdue University.     

Calculation of mixing in nonlinear circuits

A novel scheme is described for calculating the harmonic response of a nonlinear circuit driven by two or more signals incommensurate in frequency. The method, which is a natural extension of the harmonic balance technique, is not limited by the degree of nonlinearity or signal strengths nor by their proximity in frequency.     

应用于DM648的FLASH自动加载实现方法

为实现DSP嵌入式系统的应用程序自动加载功能,提出了基于TI公司的TMS320DM648的NOR Flash自动加载实现方法.首先对启动过程进行了分析,给出了用户加载程序的编写方法.在此基础上,根据公共目标文件格式和应用镜像脚本两种文件格式的说明,设计出公共目标文件格式到应用镜像脚本转换程序,生成可用于FLASH烧写的文件.最后在TMS320DM648核心板上实现了在CCS环境下对Flash编程和程序自动加载,证明该方法有效可行.     

First-harmonic approximation in nonlinear filtered circuits

The criteria given by Loeb and by Belevitch for the stability of oscillations in nonlinear filtered circuits are compared. It is shown that for a single parallel RLC filter both criteria are equivalent, but that for more complicated filters the criterion of Loeb is only a necessary condition for stability.     

A numerical method for calculation of transients in electric circuits

 The present paper describes a numerical method for calculation of transients in electric circuits,using a step by step approach.For a small interval of time △t=const,for each branch j of circuit one calculates α_j=R_j+L_j/△t+△t/C_j,β_j=R_j+△t/C_j and θ=△t/C_j.After that,for each interval △t the current increments △i_(jk),the currents i_(jk)=i_(jk-1)+△i_(jk)and the capacitor\'s voltage u_(cjk)=u_(cjk-1)+Au_(cjk)are calculated. The values of △i_(jk)are the roots of a system of simultaneous linear equations.The results of numerical calculation of transients by the proposed method do not differ from those obtained by analytical ones.The proposed method can be applied to a large number of problems in electrical engineering.A similar approach can be used for the calculation of transients in non-linear electric circuits and in other engineering disciplines(mechanics,thermodynamics,hydraulics etc.).Several numerical examples show how the pro- posed method can be applied.     

A new macromodeling approach for nonlinear microwave circuits basedon recurrent neural networks

A new macromodeling approach is developed in which a recurrent neural network (RNN) is trained to learn the dynamic responses of nonlinear microwave circuits. Input and output waveforms of the original circuit are used as training data. A training algorithm based on backpropagation through time is developed. Once trained, the RNN macromodel provides fast prediction of the full analog behavior of the original circuit, which can be useful for high-level simulation and optimization. Three practical examples of macromodeling a power amplifier, mixer, and MOSFET are used to demonstrate the validity of the proposed macromodeling approach     

ANDREI-a minicomputer nonlinear analysis program for integrated circuits

A circuit analysis program, ANDREI, has been developed which can be run on a 32K 16-bit word minicomputer with a disk unit. A novel virtual storage scheme is used to save internal memory required by large arrays. The nonlinear DC and transient and small-signal AC analyses of circuits up to 150 nodes and 150 elements can be performed in the present version. Semiconductor device models for diodes, bipolar junction transistors, junction- and MOSFETs are built in. ANDREI runs presently on a 32K VARIAN 73 minicomputer.     

A subject-independent method for automatically grading electromyographic features during a fatiguing contraction

Many studies have attempted to monitor fatigue from electromyogram (EMG) signals. However, fatigue affects EMG in a subject-specific manner. We present here a subject-independent framework for monitoring the changes in EMG features that accompany muscle fatigue based on principal component analysis and factor analysis. The proposed framework is based on several time- and frequency-domain features, unlike most of the existing work, which is based on two to three features. Results show that latent factors obtained from factor analysis on these features provide a robust and unified framework. This framework learns a model from EMG signals of multiple subjects, that form a reference group, and monitors the changes in EMG features during a sustained submaximal contraction on a test subject on a scale from zero to one. The framework was tested on EMG signals collected from 12 muscles of eight healthy subjects. The distribution of factor scores of the test subject, when mapped onto the framework was similar for both the subject-specific and subject-independent cases.