Frequency-domain analysis of strongly nonlinear circuits using aconsistent large-signal model

This paper describes an analysis method that extends the applicability of the frequency-domain methods to strongly nonlinear circuits. Nonlinearities are described with Chebyshev expansions which are evaluated with a numerically stable three-term recurrence formula. The method is coupled with a novel, measurement-based consistent modeling approach which allows improved accuracy in describing the frequency-dependence of the measured small-signal parameters. The analysis method and the modeling approach are verified by comparing measurements and calculations on a MESFET mixer, driven with two and three tones     

智能温控头盔

随着关于摩托车一盔一戴政策的出台,每位驾驶员以及乘坐人员都必须穿戴头盔,而对于传统头盔来说内部温度会在短时间增高,使驾驶员在驾驶摩托车时会感到不适。而正因如此我们设计了一款能够自动调节的智能温控头盔,旨在解决驾驶员在驾驶途中头盔内部温度升高带来的不适感,其中利用了温度传感器以及单片机的技术,以此来实现头盔内部温度的转变,其中还添加了智能语音系统,方便驾驶途中接听电话,减少了驾驶员过去应接电话而带来的危险操作。     

Seat Belt Vibration as a Stimulating Device for Awakening Drivers

This paper presents a safety driving system that uses a seat belt vibration as a stimulating device for awakening drivers. The vibration stimulus was composed of pulsation tension, which was applied by the seat belt motor retractor. Magnitude, duration, and repetition rate of the additional tension were the major parameters that determined the awakening effect of the stimulus. We constructed a driving simulator, which was able to induce driver's drowsiness. In the experiments using the driving simulator, the driver's drowsiness was detected by changes in the driver's eye movements measured by electrooculography (EOG) and/or changes in facial expression of the driver monitored by the examiners through a video camera, subjective evaluation, and lane deviation. Exerting additional tension of 130 N for 3 cycles at duration and interval of 100 ms was the most effective pattern for awakening the driver without causing discomfort.     

Automatic detection of pathological voices using complexity measures, noise parameters, and mel-cepstral coefficients

This paper proposes a new approach to improve the amount of information extracted from the speech aiming to increase the accuracy of a system developed for the automatic detection of pathological voices. The paper addresses the discrimination capabilities of 11 features extracted using nonlinear analysis of time series. Two of these features are based on conventional nonlinear statistics (largest Lyapunov exponent and correlation dimension), two are based on recurrence and fractal-scaling analysis, and the remaining are based on different estimations of the entropy. Moreover, this paper uses a strategy based on combining classifiers for fusing the nonlinear analysis with the information provided by classic parameterization approaches found in the literature (noise parameters and mel-frequency cepstral coefficients). The classification was carried out in two steps using, first, a generative and, later, a discriminative approach. Combining both classifiers, the best accuracy obtained is 98.23% ± 0.001.     

MEMS微波功率传感器的悬臂梁弯曲模型研究北大核心

为了研究电容式MEMS微波功率传感器悬臂梁的非线性运动，建立了MEMS悬臂梁在空间域上的弯曲特性模型，综合考虑静电力、轴向应力以及残余应力对悬臂梁非线性运动的影响，求解得到动力学微分方程。在此基础上研究在不同杨氏模量、驱动电压和残余应力下悬臂梁的弯曲特性，解析得到对应的悬臂梁弯曲特性曲线与轴向应力曲线。使用有限元分析软件ANSYS对不同驱动电压下的悬臂梁下拉位移进行仿真，并对仿真结果与解析结果进行比较。结果表明，在驱动电压从10 V到20 V的变化过程中，仿真结果与模型解析结果具有一致的趋势，两者间的最大误差仅有8.81%。对电容式MEMS微波功率传感器的悬臂梁弯曲特性的研究具有一定的参考价值和指导意义。     

Output Power PDF of a Saturated Semiconductor Optical Amplifier: Second-Order Noise Contributions by Path Integral Method

We have developed a second-order small-signal model for describing the nonlinear redistribution of noise in a saturated semiconductor optical amplifier. In this paper, the details of the model are presented. A numerical example is used to compare the model to statistical simulations. We show that the proper inclusion of second-order noise terms is required for describing the change in the skewness (third-order moment) of the noise distributions. The calculated probability density functions are described far out in the tails and can hence describe signals with very low bit error rate (BER). The work is relevant for describing the noise distribution and BER in, for example, optical regeneration.     

一种新的大信号射频功率器件建模方法

对小信号网络分析而言,单一的S参数已足够描述器件的特性.但对大信号网络分析而言,则需要更多的数学工具来描述器件的特性.本文采用了一个新的适用于描述大信号非线性特性的描述函数——非线性散射函数.利用非线性散射函数可以完成对大信号射频功率器件的精确建模.     

变阻抗相对论返波管的研究

根据相对论返波管（RBWO）的非线性理论，数值模拟了耦合阻抗单步跃变型RBWO效率与束流参量、耦合阻抗跃变位置、高低耦合阻抗比值的依赖关系，结果表明器件最优化效率可达到50%，设计制造了一个X波段高功率耦合阻抗单步跃变型RBWO，运用全电磁粒子模拟程序仿真了器件中注波互作用过程，预见出器件功率、效率、频率等性能参量，在电子注电流、注加速电压、互作用区长度相同的实验条件下，测得变阻抗器件实验效率约为均匀阻抗型器件效率的2倍。     

变阻抗相对论返波管的研究

根据相对论返波管(RBWO)的非线性理论,数值模拟了耦合阻抗单步跃变型RBWO效率与束流参量、耦合阻抗跃变位置、高低耦合阻抗比值的依赖关系,结果表明器件最优化效率可达到50%.设计制造了一个X波段高功率耦合阻抗单步跃变型RBWO,运用全电磁粒子模拟程序仿真了器件中注波互作用过程,预见出器件功率、效率、频率等性能参量.在电子注电流、注加速电压、互作用区长度相同的实验条件下,测得变阻抗器件实验效率约为均匀阻抗型器件效率的2倍.     

Nonlinear antenna technology

Nonlinear antennas combine advances in nonlinear dynamics, active antenna design, and analog microelectronics to generate beam steering and beam forming across an array of nonlinear oscillators. Nonlinear antennas exploit two phenomena typically shunned in traditional designs: nonlinear unit cells and interelement coupling. The design stems from nonlinear coupled differential equation analysis that by virtue of the dynamic control is far less complex than the linear counterparts by eliminating the need for phase shifters and beam forming computers. These advantages arise from incorporating nonlinear dynamics rather than limiting the system to linear quasisteady state operation. A theoretical framework describing beam shaping and beam forming by exploiting the phase, amplitude, and coupling dynamics of nonlinear oscillator arrays is presented. Experimental demonstration of nonlinear beam steering is realized using analog microelectronics     

Modeling and Digital Control of a Phase-Controlled Series–Parallel Resonant Converter

A nonlinear model for a phase-controlled series-parallel resonant converter is developed using the extended describing function method and d-q decomposition. The model is linearized and reduced using the balanced model reduction technique. Based on the reduced model and taking into account the zero-order hold delay and the computation delay in the sampled-data system, a digital controller for the converter is designed. The controller is implemented with a digital signal processor (DSP). The closed-loop converter with the DSP controller is built and tested experimentally. Recorded transient waveforms show that the closed-loop converter is capable of not only responding to the reference input change as required by the design specifications, but also stabilizing the output effectively under disturbances from both the output and the input     

Nonlinear system analysis of renal autoregulation in normotensiveand hypertensive rats

The authors compared the dynamic characteristics in renal autoregulation of blood flow of normotensive Sprague-Dawley rats (SDR) and spontaneously hypertensive rats (SHR), using both linear and nonlinear systems analysis. Linear analysis yielded only limited information about the differences in dynamics between SDR and SHR. The predictive ability, as determined by normalized mean-square errors (NMSE), of a third-order Volterra model is better than for a linear model. This decrease in NMSE with a third-order model from that of a linear model is especially evident at frequencies below 0.2 Hz. Furthermore, NMSE are significantly higher in SHR than SDR, suggesting a more complex nonlinear system in SHR. The contribution of the third-order kernel in describing the dynamics of renal autoregulation in arterial blood pressure and blood flow was found to be important. Moreover, the authors have identified the presence of nonlinear interactions between the oscillatory components of the myogenic mechanism and tubuloglomerular feedback (TGF) at the level of whole kidney blood flow in SDR. An interaction between these two mechanisms had previously been revealed for SDR only at the single nephron level. However, nonlinear interactions between the myogenic and TGF mechanisms are not detected for SHR     

48级灰度线性声光调制驱动源研究

设计了一种衍射光强灰度值随数字调制电压成线性变化的48级灰度线性声光调制驱动源。该设计通过数字控制电路把0~5V (D.C.) 分为48档次的数字调制电压,进而对晶体振荡电路产生的高频载波信号进行幅度调制,使声光调制驱动源输出相应的射频驱动信号并驱动声光器件。通过声光调制实验得到对应的衍射光强灰度值并显示相应的灰度等级,针对声光器件固有的非线性特性,通过线性电压补偿技术得到补偿后的衍射光强灰度值与数字调制电压的线性相关系数为97.73%,比补偿前提高了7.06%。     

ECG on the road: robust and unobtrusive estimation of heart rate

Modern automobiles include an increasing number of assistance systems to increase the driver's safety. This feasibility study investigated unobtrusive capacitive ECG measurements in an automotive environment. Electrodes integrated into the driving seat allowed to measure a reliable ECG in 86% of the drivers; when only (light) cotton clothing was worn by the drivers, this value increased to 95%. Results show that an array of sensors is needed that can adapt to the different drivers and sitting positions. Measurements while driving show that traveling on the highway does not distort the signal any more than with the car engine turned OFF, whereas driving in city traffic results in a lowered detection rate due to the driver's heavier movements. To enable robust and reliable estimation of heart rate, an algorithm is presented (based on principal component analysis) to detect and discard time intervals with artifacts. This, then, allows a reliable estimation of heart rate of up to 61% in city traffic and up to 86% on the highway: as a percentage of the total driving period with at least four consecutive QRS complexes.     

AS级Internet拓扑层次性分析与建模

基于对AS(autonomous system)级拓扑实测数据的分析,提取出拓扑层次性相关的若干重要特征;给出层次划分的按据、优化参数以及新加入节点的连接细节和非线性择优概率;提出了一种基于核数划分的AS级互联网层次动态演化模型(IAT-HDEM).对模型进行了计算机建模和数值仿真评估,分析表明该模型能较好地模拟出真实...     

振荡器谐振回路的参数选择

针对振荡器谐振回路参数的选择较多地依赖于经验的问题,提出了从振荡器的等效电路出发,得到了描述振荡器的非线性微分方程,通过引入随机项来描述振荡器的内部电噪声,由此建立了用于分析振荡器行为的非线性随机微分方程。并针对遗传算法对振荡器谐振回路参数的优选结果,采用10MHz的Pierce晶体振荡器,得出了实证依据。当C1和C2比较接近时,Pierce振荡电路中的相位噪声可得到更好的抑止。     

Performance of Baseband Digital Data Transmission in Nonlinear Channels with Memory

This paper considers the performance of digital data transmission in nonlinear channels with memory. The analysis is based on the application of a particular form of Volterra series representation for the nonlinear system describing the transmission channel. First, expressions are derived for the output mean and power spectral density under certain conditions. Next, the paper presents a computationally convenient expression for the error rate involved in such transmission.     

On the Use of Describing Functions in the Study of Nonlinear Active Microwave Circuits

It is shown that a nonlinear microwave circuit can easily be represented by a feedback model. This formalistic identity with nonlinear control systems suggests that methods and results can be borrowed from nonlinear control theory. The describing function technique, a concept that has been developed to a high degree of sophistication in control theory, is applied to the problem of phase-locking of microwave oscillators. The use of describing functions in the study of nonlinear microwave circuits may give a simple conceptual understanding of locking phenomena, for example, and thereby reduce computational efforts.     

Simple analytical expression for the effect of initial interaction in Cerenkov second-harmonic generation

We analyze the nonlinear coupled-mode equations describing the Cerenkov second-harmonic generation in a nonlinear dielectric waveguide. An approximate analytic solution in a closed form is newly obtained for the pump depletion and nonlinear phase-shift of the fundamental field. Our solution, valid over the whole length, shows that the conversion efficiency is reduced by the feature of the initial process of the nonlinear interaction. It gives a simple expression for the efficiency with better accuracy for short device length. We have compared our solution with the previous analytic solutions derived by others. The validity of our solution is also checked by the nonlinear beam propagation method. Furthermore, the solution can be expressed in terms of a leaky mode phase-mismatch, and it shows explicitly that a resonant pump depletion and nonlinear phase-shift of the fundamental field occurs when the phase-matching to the lowest order leaky mode is accomplished. Extending our analysis method, we have also performed higher order numerical analysis for the nonlinear coupled-mode equations.