共形相控阵天线方向图综合

交替投影法灵活性强,效率高,且其收敛也非常好,尤其是在大型阵列天线的方向图综合中。文中给出了改进的交替投影法的计算步骤,并将该方法成功地应用于旋转抛物面(GPOR)上的2个共形相控阵天线的方向图综合。研究表明,该方法对共形相控阵天线的方向图综合适用且高效。     

Error analysis of maximum likelihood estimates of physicalparameters from one or more dispersive waves

Measurement of physical parameters from one or more dispersive waves propagating in a band of frequencies across a linear array of receivers is considered. The waves propagate according to a known physical model having real-valued parameters and have spatially uncorrelated white Gaussian noise added to them. The objective of the measurement is to estimate a specified subset of the physical parameters, the remaining physical parameters are externally provided and have known error statistics. Existing maximum likelihood (ML) estimation and Cramer-Rao (CR) bounds theory describes the measurement under the assumption of correct values for the externally provided parameters. A review of this theory is presented for completeness. Then a bounding estimate on the total error on the estimated parameters is derived which takes into account both the CR bounds and errors in the externally provided parameters. Suggestions for the application of the theory to practical problems are provided. A criterion is derived for determining whether additional, unwanted (“nuisance”) parameters should be included in the estimate to improve the total error on the desired parameters     

Equivalent circuit parameters of resonant tunneling diodesextracted from self-consistent Wigner-Poisson simulation

The equivalent circuit parameters of resonant tunneling diodes (RTD) are extracted from numerical simulation results for RTDs. The RTD models used in this paper are double barrier structures. The influence of the resonant tunneling structure (RTS) parameters, such as the height of barriers, the width of the quantum well, the width of the spacers, and the width of the barriers, on the device parameters are systematically discussed. The effects of device temperature on device parameters are also discussed. Scattering between electrons and phonons greatly affects device parameters and thereby the function of the RTDs. Physical explanations about how the structure parameters and device temperature influence the device parameters are provided. Based on the analysis results, a general way to get an RTD oscillator with a higher maximum frequency is suggested     

Adaptive Fuzzy Control of Nonlinear in Parameters Uncertain Chaotic Systems Using Improved Speed Gradient Method

This paper presents an adaptive fuzzy controller for Nonlinear in Parameters (NLP) chaotic systems with parametric uncertainties. In the proposed controller, the unknown parameters are estimated by the novel Improved Speed Gradient (ISG) method, which is a modification of Speed Gradient (SG) algorithm. ISG employs the Lagrangian of two suitable objective functionals for on-line estimation of system parameters. The most significant advantage of ISG is that it is applicable to NLP systems and it results in a faster rate of convergence for the estimated parameters than the SG method. Estimated parameters are used to design the fuzzy controller and to calculate the Lyapunov exponents of the chaotic system adaptively. Furthermore, established on the well-known Takagi–Sugeno (T-S) fuzzy model, a LMI (Linear Matrix Inequality)-based fuzzy controller is designed and is tuned using estimated parameters and Lyapunov exponents. Throughout the controller design procedure, several important issues in fuzzy control theory including relaxed stability analysis, control input performance specifications, and optimality are taken into account. Combination of ISG parameter estimation method and T-S-based fuzzy controller yields an adaptive fuzzy controller capable to suppress uncertainties in parameters and initial states of NLP chaotic systems. Finally, simulation results are provided to show the effectiveness of the ISG and adaptive fuzzy controller on chaotic Lorenz system and Duffing oscillator.     

A practical approach to model long MIS interconnects in VLSI circuits

In this paper, a practical approach to model metal-insulator-semiconductor (MIS) interconnects is presented, with focus on the microstrip configuration. Starting from a one-dimensional (1-D) electromagnetic field analysis, we first extend the validity range of some closed-form expressions from 1-D to two-dimensional (2-D) and present an original RLCG-B model with five equivalent circuit parameters. These parameters, which depend on two effective widths of the physical metal strip, can be frequency dependent because of the skin effect and the dielectric losses. The original RLCG-B model is then modified and implemented with seven frequency-independent circuit parameters. These parameters are computed by analytical equations. Numerical simulations are used to validate the original and modified RLCG-B models. A formula to allow comparison of various interconnect models in the time domain is proposed. Comparisons based on this formula are presented for a single transmission line with source resistance, R/sub S/, and load capacitance, C/sub L/. Such comparisons are more meaningful in VLSI applications than comparisons of characteristics derived from swept-frequency per-unit-length parameters.     

EEG/MEC error bounds for a static dipole source with a realistichead model

We derive Cramer-Rao bounds (CRBs) on the errors of estimating the parameters (location and moment) of a static current dipole source using data from electro-encephalography (EEG), magneto-encephalography (MEG), or the combined EEG/MEG modality. We use a realistic head model based on knowledge of surfaces separating tissues of different conductivities obtained from magnetic resonance (MR) or computer tomography (CT) imaging systems. The electric potentials and magnetic field components at the respective sensors are functions of the source parameters through integral equations. These potentials and field are formulated for solving them by the boundary or the finite element method (BEM or FEM) with a weighted residuals technique. We present a unified framework for the measurements computed by these methods that enables the derivation of the bounds. The resulting bounds may be used, for instance, to choose the best configuration of the sensors for a given patient and region of expected source location. Numerical results are used to demonstrate an application for showing expected accuracies in estimating the source parameters as a function of its position in the brain, based on real EEG/MEG system and MR or CT images     

Literal solutions for time-domain crosstalk on losslesstransmission lines

The transmission line equations for a three-conductor lossless line in a homogeneous medium are solved in literal (symbolic) form in the time domain. The resulting formulas for the crosstalk voltages are exact and are given in terms of the line parameters and the termination impedances. These formulas demonstrate the effect of the various line parameters on the resulting crosstalk and show how to adjust the line parameters to achieve a desired time-domain crosstalk. In addition, other solution methods are discussed and used to verify the literal solution     

基于EM的主动段弹道导弹跟踪算法研究

为了提高未知弹道参数下主动段目标跟踪的精度,提出基于期望最大化（Expectation Maximization,EM）的联合优化算法框架.首先在E步基于平滑器得到状态和未知参数的后验估计,然后在M步计算初始状态的均值、协方差以及过程噪声协方差等未知统计量,最后推导出基于URTS（Unscented Rauch-Tung-Striebel）的EM算法,并给出未知统计量的最优解析解,避免了非凸优化难以求解的问题.仿真结果表明：在相同量级的计算量下,本文算法的状态估计精度优于迭代UKF（Unscented Kalman Filter）算法.     

Quality of service in telecommunications .II. Translation of QoSparameters into ATM performance parameters in B-ISDN

The main goal of this article is to present the translation of quality of service (QoS) parameters between layers. The QoS parameters in the ATM layer and AAL are defined. This translation concept came from the QoS framework in which the influence of the protocol stack on the QoS should be considered. As an example, we concentrate on the translation from the AAL to the ATM layer, as the AAL must be designed to be service-dependent and specific. Translation, both taking the transport protocol into account as well as between application and transport QoS, needs further study. However, our study shows that the QoS translation is a possible and good approach in end-to-end QoS guarantees in the broadband integrated services digital network (B-ISDN). As far as the end-to-end QoS guarantee issue is concerned, the transport QoS requirements are specified in terms of bounds on transport QoS parameters. The bounds on transport QoS parameters will be translated into the bounds on ATM layer QoS parameters. The ATM-layer QoS parameters resulting from the translation will be the performance requirements on a connection basis for the ATM network, but are basically the end-to-end parameters, including the network and the end systems. Therefore, the QoS translation finally results in the network performance parameters in the ATM network. We define QoS parameters in the AAL and ATM layer. Case studies in which the translation method is applied to a constant bit rate (CBR) video service and data service, respectively, are also presented     

Selection algorithm for parameters to characterize uterine EHG signals for the detection of preterm labor

This article proposes a selection method that can be applied to choose the best parameters to classify contractions in the uterine electrohysterography (EHG) signal for the detection of preterm labor. Several types of parameters have historically been extracted from the electrohysterogram. These can be divided into three classes: linear parameters, nonlinear parameters and parameters related to the electrohyterogram propagation. Frequency band enhancement EHG characterization has also been extensively studied. Our work is divided in two parts. The first part is to implement and compute all the parameters already extracted from the EHG that have been published in the literature. These parameters were computed both on the original EHG and on different frequency bands obtained using wavelet packet decomposition. In the second part, we will use a new parameters selection method to eliminate all parameters that are not efficient and pertinent for classification. Our results indicate a set of 13 linear parameters, 3 nonlinear parameters and 2 propagation parameters that are potentially most useful to discriminate between pregnancy and labor contractions, either on different frequency bands or directly on original EHG.     

System profiles in content-based image indexing and retrieval

In this paper, a novel study on system profiles and adaptation of parameters for end-users of content-based indexing and retrieval (CBIR) applications are presented. The main objective of the study is improving the overall CBIR application performance in different hardware platforms having different technical capabilities and conditions. We define CBIR system profiles in terms of hardware and system platform attributes and propose CBIR parameters for each profile. Hence, the study consists of two main parts: system profiling and adaptation of indexing and retrieval parameters for each profile. The proposed CBIR parameters are appropriate configurations for optimal CBIR use on every platform. The proposed parameters for each system profile are assessed over a large set of experiments. Experimental studies show that the proposed parameters for each system profile have satisfactory semantic retrieval performance, with reduced computational complexity and storage space requirement. 45 to 78% improvement is achieved in the computational complexity of the retrieval process depending on the profile.     

Polarization mode dispersion in spun fibers with different linearbirefringence and spinning parameters

This paper shows how the initial linear birefringence determines the necessary spinning parameters to produce spun fiber with optimum differential group delay (DGD) and polarization mode dispersion (PMD) properties. DGD measurements are reported on two pairs of fibers, each pair having been fabricated from a particular fiber preform. The fiber pairs each consist of a sample of spun and unspun fiber. These measurements are then compared with theoretical simulations for each fiber to determine the required range of spinning parameters for a given initial linear birefringence. These results should help in optimizing the spinning parameters for producing high-performance spun fibers     

降雨率的最坏月分区转换模式研究

利用我国56个气象台站降雨率的最坏月分布和年平均分布的转换关系，对转换模式参数进行了分析，得到我国降雨率的分区转换参数(南方区、北方区、戈壁区)，该分区模式与不同台站转换结果间有很好的一致性，可用于我国不同地区的降雨率最坏月转换。同时利用ITU—R提供的世界不同地区的参数及中国三地区的参数，得到了全球分区参数(热带亚热带和温带常湿区，与温带、极区和戈壁区)，全球分区模式适用于全球多数地区的最坏月转换。     

Performance Evaluation and ParameterOptimization of MC-CDMA

The performance of multicarrier systems depends on the propagation channel behavior. The latter is subject to time and/or frequency selectivity. The designer has to select properly the guard interval and the number of carriers for a given system bandwidth to combat the channel dispersiveness. In this paper, we investigate the sensitivity of downlink multicarrier code-division multiple-access (MC-CDMA) performance to these parameters in different environments. We derive closed-form expressions of the useful and the different interference powers after maximum ratio combining and despreading. The optimum parameters correspond to the minimum of the signal-to-noise-ratio degradation. It turns out that the derivations in the paper of Steendam and Moeneclaey ( IEEE Trans. Commun., 1999) that are restricted to the orthogonal frequency-division multiplexing (OFDM) system are a particular case of our results. Numerical evaluation of the analytical expressions reveals that the optimum parameters of the MC-CDMA and its corresponding OFDM system are similar and depend in the same way on the channel characteristics. We show in this paper that the load of the MC-CDMA system only has small influence on the optimization of the parameters. Therefore, from the point of view of parameter optimization, single-user transmission is sufficient to find the optimum parameters. Furthermore, as the optimum parameters mainly depend on the channel characteristics, similar conclusions can be drawn for the uplink transmission     

Low Cost Built-in Sensor Testing of Phase-Locked Loop Dynamic Parameters

Phase-locked loops (PLLs) serve as core building blocks for communication systems and are often used to synthesize IO clocks for data synchronization and frequency sources for RF conversion. Testing of PLL loop performance is consequently important for guaranteeing the reliability of the underlying communication systems. In this paper, a low cost testing method based on loop triggering and use of built-in analog sensors (small number of transistors) to accurately predict phase-locked loop dynamic parameters is proposed. The sensor responses show strong statistical correlation with the PLL parameters being tested. Accordingly, supervised learning is applied to predict the required PLL parameters from the observed sensor response after “training”. In order to verify analog sensor testing in PLL loop response evaluation, an off-the-shelf PLL and a PLL on printed circuit board (PCB) are tested using this method. The results are analyzed and shown with high correlation to loop parameters. Parameters including charge pump current, voltage-controlled oscillator (VCO) gain, bandwidth, phase margin, and locking time are predicted accurately to prove the viability of the proposed test method.     

Flexible Algorithms: Fragments from a Beginners' Course

This article presents an overview of a beginner's course on flexible algorithms. We briefly describe this notation's main features and present fragments from this course. The core algorithmic notation of flexible algorithms is based on functions with In parameters and Out parameters (but no In/Out parameters) and conditional statements. As in mathematics, variables and parameters receive a value only once. Blocks and loops (including nested forms) aren't part of the core language but are abbreviations for certain compound forms in the core language. Our notation has an iterative style and includes a once-only assignment statement. Because our notation can't update variables and parameters, it enables parallel execution     

Analysis of the 3-L DF-PPM inverter drive scheme

A novel modulation scheme for inverter drive systems based on the fundamental principle of position modulation (PPM) is proposed. It is called the three level double frequency PPM (3-L DF-PPM) scheme. Analytical expressions for its spectrum are given and its basic features are discussed. It is shown that the 3-L DF-PPM scheme combines a number of interesting properties that render it very suitable for variable frequency inverter drive applications. Its main advantages are: (a) The fundamental component is strong and easily controlled by two parameters, namely, the modulation index A and pulse width τ. lpar;b) The higher harmonics amplitude is suppressed with respect to the fundamental and depends on the particular choice of parameters A and τ as well, (c) The operation is uniform throughout the whole frequency range avoiding, therefore, any transitional stage such as that appearing in the sinusoidal PWM schemes, (d) The pulsating torques can be optimized by a proper choice of the parameters A and τ. The optimization is possible just because there are two parameters controlling the harmonics amplitude. This is characteristic of PPM schemes, (e) The time interval between successive choppings d the waveform is kept greater than a minimum time interval so that lock-out phenomena are avoided. (?) The digital or microprocessor realization of the scheme exhibits a number of advantages over the existing PWM techniques. Simulation results are given.     

Maximum likelihood and lower bounds in system identification withnon-Gaussian inputs

We consider the problem of estimating the parameters of an unknown discrete linear system driven by a sequence of independent identically distributed (i.i.d.) random variables whose probability density function (PDF) may be non-Gaussian. We assume a general system structure that may contain causal and noncausal poles and zeros. The parameters characterizing the input PDF may also be unknown. We derive an asymptotic expression for the Cramer-Rao lower bound, and show that it is the highest (worst) in the Gaussian case, indicating that the estimation accuracy can only be improved when the input PDF is non-Gaussian. It is further shown that the asymptotic error variance in estimating the system parameters is unaffected by lack of knowledge of the PDF parameters, and vice verse. Computationally efficient gradient-based algorithms for finding the maximum likelihood estimate of the unknown system and PDF parameters, which incorporate backward filtering for the identification of non-causal parameters, are presented. The dual problem of blind deconvolution/equalization is considered, and asymptotically attainable lower bounds on the equalization performance are derived. These bounds imply that it is preferable to work with compact equalizer structures characterized by a small number of parameters as the attainable performance depend only on the total number of equalizer parameters     

非均匀介质中的非对称耦合传输线一般情况下散射参数的推导

首次采用新的方法推导出非均匀介质巾非对称耦合传输线在一般情况下的散射参数解析表达式，给出了以正规模式参量描述的非均匀介质中非对称耦合传输线的散射参数表达式，形式简明，物理概念明晰，从理论上证明了所得散射参数的正确性，并结合所得S参数，给出了非均匀介质中非对称耦合传输线的等效网络。为非均匀介质中非对称耦合传输线在三维(多层)微波集成电路中的应用提供了有力的理论工具。     

How to model reliability-growth when times of design modificationsare known

Engineers often make changes during system development in order to correct design weaknesses. If done well this results in reliability growth as development continues. Since no reliability-growth model is adequate for all time (any growth model is valid only for some finite amount of time) it is prudent to use a different reliability model between each two design modifications. This paper assumes that the reliability growth model between each two design modifications is either a Poisson process or power-law process. Maximum likelihood estimates of the parameters are obtained for two cases: (1) no constraints on parameters; and (2) some constraints on parameters