Analog circuit optimization using adjoint network based sensitivity analysis

Performance optimization as per the desired specifications is a major requirement of analog and mixed signal circuit design process. Rapid scaling of the semiconductor technology demands efficient optimization techniques with minimal manual efforts. In this paper, a gradient based method for analog circuit optimization using adjoint network based sensitivity analysis is presented. The sensitivity of circuit response with respect to the different parameters is computed by using analog circuit and its adjoint transformation. The proposed method is applied to optimize performance of a two stage operational amplifier (OpAmp). Subsequently, the OpAmp circuit is simulated using Cadence Virtuoso for optimized parameters and the results are validated with post fabrication measurement results.     

A global optimization technique for statistical classifier design

A global optimization method is introduced that minimize the rate of misclassification. We first derive the theoretical basis for the method, on which we base the development of a novel design algorithm and demonstrate its effectiveness and superior performance in the design of practical classifiers for some of the most popular structures currently in use. The method, grounded in ideas from statistical physics and information theory, extends the deterministic annealing approach for optimization, both to incorporate structural constraints on data assignments to classes and to minimize the probability of error as the cost objective. During the design, data are assigned to classes in probability so as to minimize the expected classification error given a specified level of randomness, as measured by Shannon's entropy. The constrained optimization is equivalent to a free-energy minimization, motivating a deterministic annealing approach in which the entropy and expected misclassification cost are reduced with the temperature while enforcing the classifier's structure. In the limit, a hard classifier is obtained. This approach is applicable to a variety of classifier structures, including the widely used prototype-based, radial basis function, and multilayer perceptron classifiers. The method is compared with learning vector quantization, back propagation (BP), several radial basis function design techniques, as well as with paradigms for more directly optimizing all these structures to minimize probability of error. The annealing method achieves significant performance gains over other design methods on a number of benchmark examples from the literature, while often retaining design complexity comparable with or only moderately greater than that of strict descent methods. Substantial gains, both inside and outside the training set, are achieved for complicated examples involving high-dimensional data and large class overlap     

An adjoint variable method for sensitivity calculations of multiport devices

Recently, an adjoint variable method (AVM) for sensitivity calculations has been proposed for use with the method of moments solvers. In this paper, we extend this method to be suitable for application to multiport devices. The target objective function is usually represented in terms of the device's S-parameters. Our AVM obtains the sensitivities of the S-parameters with respect to all design variables using only one full simulation with additional overhead. This overhead is usually less than the computation time of a full simulation. An analytical expression for the adjoint excitation is derived, leading to stable sensitivities. The potential of the proposed technique is demonstrated by analyzing low-pass and bandpass filters. The results show very good agreement between the proposed AVM and the conventional finite-difference approach (FDA). Moreover, the AVM is always faster than the FDA. The speed-up factor increases as the size of the problem increases.     

Analog circuit design optimization through the particle swarm optimization technique

This paper details the Particle Swarm Optimization (PSO) technique for the optimal design of analog circuits. It is shown the practical suitability of PSO to solve both mono-objective and multiobjective discrete optimization problems. Two application examples are presented: maximizing the voltage gain of a low noise amplifier for the UMTS standard and computing the Pareto front of a bi-objective problem, maximizing the high current cut off frequency and minimizing the parasitic input resistance of a second generation current conveyor. The aptness of PSO to optimize difficult circuit problems, in terms of numbers of parameters and constraints, is shown.     

Second-derivative sensitivity using the concept of the adjoint network

Second-derivative sensitivities for linear time-invariant networks are derived by an extension of the method used by Director and Rohrer to calculate first-derivative sensitivities.     

Implementation of a decoupled optimization technique for design ofswitching regulators using genetic algorithms

This paper presents an implementation of a decoupled optimization technique for design of switching regulators using genetic algorithms (GAs). The optimization process entails the selection of component values in a switching regulator, in order to meet the static and dynamic requirements. Although the proposed method inherits characteristics of evolutionary computations that involve randomness, recombination, and survival of the fittest, it does not perform a whole-circuit optimization. Thus, intensive computations, that are usually found in stochastic optimization techniques can be avoided. Similar to many design approaches for power electronics circuits, a regulator is decoupled into two components, namely the power conversion stage (PCS) and the feedback network (FN). The PCS is optimized with the required static characteristics, whilst the FN is optimized with the required static and dynamic behaviors of the whole system. Systematic optimization procedures are described and the technique is illustrated with the design of a buck regulator with overcurrent protection. The predicted results are compared with the published results available in the literature and are verified with experimental measurements     

芯片设计中的功耗估计与优化技术

在芯片设计中,低功耗一直是一个重要的目标,受到封装、供电、散热的约束,并且最大功耗限制越来越严格。在本文中,首先讨论了芯片中的功耗来源。接着,阐述了在设计过程初期可以采用的几项可以降低功耗的技巧。本文提出的方法用于架构设计和前段设计的初期,如功耗估计、低功耗架构优化和时钟门控等。     

Systematic photonic crystal device design: global and local optimization and sensitivity analysis

We present a set of modeling, sensitivity analysis, and design optimization methods for photonic crystal structures based on Wannier basis field expansion and efficient matrix analysis techniques. We develop the sensitivity analysis technique to analyze both refractive index perturbations and dielectric boundary shift perturbations. Our modeling method is /spl sim/1000/spl times/ faster than finite-difference time-domain (FDTD) for searching through a large number of similar device designs. We show that our optimization techniques, relying on the efficiency of the modeling and sensitivity analysis methods, enable systematic global and local optimizations of integrated optical components. We show that our design method can be controlled to favor designs without high-energy build-ups, potentially making them more fabrication-error tolerant. We present design examples and verify our designs with FDTD calculations.     

Precision and sensitivity optimization for white-lightinterferometric fiber-optic sensors

A detailed analysis for accuracy and sensitivity of fiber-optic sensor based on white-light interferometric technique with wavelength scanning is presented. Analytical equations for optimal optical path difference were obtained, which allow to reach the minimum measurement uncertainty. The results of the analysis can be applied for optimization of any sensor based on low coherence spectrum domain technique, though our experimental validation of analysis has been carried out with the temperature sensor based on the Sagnac interferometer having a twisted high-birefringent fiber as a sensing element     

Neural space-mapping optimization for EM-based design

We propose, for the first time, neural space-mapping (NSM) optimization for electromagnetic based design. NSM optimization exploits our space-mapping (SM)-based neuromodeling techniques to efficiently approximate the mapping. A novel procedure that does not require troublesome parameter extraction to predict the next point is proposed. The initial mapping is established by performing upfront fine-model analyses at a reduced number of base points. Coarse-model sensitivities are exploited to select those base points. Huber optimization is used to train, without testing points, simple SM-based neuromodels at each NSM iteration. The technique is illustrated by a high-temperature superconducting quarter-wave parallel coupled-line microstrip filter and a bandstop microstrip filter with quarter-wave resonant open stubs     

A sensitivity optimization approach to design of a disturbanceobserver in digital motion control systems

This paper is concerned with a digital design methodology for the disturbance observer. The controller (disturbance observer) is designed such that the system sensitivity function is made to match a chosen target sensitivity function by numerical optimization. One advantage of the proposed design method is that the tradeoff between command following, disturbance suppression, and measurement noise rejection is made transparent in the process of the control system design. This allows the system designer to bypass the effort of obtaining a highly accurate system model. Another aim of this research, relative to previous works, is to study how the design specifications can be best structured in the digital filter (a main component of the disturbance observer) for easy implementation. The robust feedback controller, designed in the velocity loop, is used in conjunction with a feedback controller located in the position loop and a feedforward controller acting on the desired output to construct a control structure for high-speed/high-accuracy motion control. Simulation and experiments applied to a high-speed XY table designed for micro positioning demonstrate the effectiveness of the proposed controller     

EM based design of square-ring vialess bandpass filters

A simple technique for the design of new, vialess square-ring bandpass filters is presented. The proposed technique is based on the full-wave electromagnetic simulation of a single filter section with variable offset distance to realize a wide range of bandpass filters with flexible specifications at any given center frequency. The new, multilayered filter configurations are vialess in nature, taking advantage of the broadside coupling between different layers for simple fabrication. Two- and three-resonator Chebyshev bandpass filters with 20% and 10% bandwidth are designed at a center frequency of 2 GHz and the theoretical response is validated by measurement. Due to the EM based design approach, the proposed technique offers a high degree of accuracy. These new configurations are suitable for a variety of multilayered fabricational technologies.     

Robust power grid network design considering EM aging effects for multi-segment wires

This paper presents a number of power grid network design and optimization techniques that consider the electromigration (EM) effects for multi-segment interconnect wires. First, we consider a new EM immortality constraint due to EM void saturation volume for multi-segment interconnects. It helps reduce conservativeness in the EM-aware on-chip power grid design. Along with the EM nucleation phase immortality constraint, we show that both EM immortality constraints can be naturally integrated into the existing programming based power grid optimization framework. Second, to mitigate the overly conservativeness of the immortality constrained optimization methods, we further explore three strategies: we first size up failed wires to meet one of the immortality conditions subject to the design rules; second, we consider the EM-induced aging effects on power supply networks for a target lifetime, which allows some short-lived wires to fail and optimizes the remaining wires; third, we propose a large change sensitivity-based optimization scheme to perform localized fixing based on recently proposed coupled EM-IR drop analysis method. Numerical results on a number of IBM-format power grid networks demonstrate that the new method can reduce more power grid area compared to the existing EM immortality constrained optimizations. Moreover, the new method is able to optimize power grids with nucleated wires, which would not be possible with the existing methods. Results also show the sensitivity-based localized power girds fixing can fix EM-induced IR drop violations in a few minutes for synthesized power grid networks from ARM core designs.     

A high sensitivity measuring technique for capacitive sensortransducers

A measuring technique is proposed for a capacitive-type sensor that has been developed to measure the density of dielectric powder gaseous suspensions. The basic principle of the proposed technique is to measure the variations of sensor capacitance by measuring the phase shift between voltage and current in a series RLC circuit tuned to resonance. Experimental results obtained with the technique are presented     

A new optimization method for antenna design

The authors consider the class of conformal antennas consisting of bounded smooth closed curves in two dimensions and determine the surface field which maximizes power radiated in angular sector. The problem is cast as one of optimal control with the control set consisting of the surface current, constrained to have energy bounded by some constant, and the cost functional is taken to be the far field power radiated in an angular sector. A constructive algorithm is presented for approximating both the optimal value of the cost functional and the surface current which produce this optimal value. Bothte andtm polarizations are considered.     

Two-pole approximation for interconnect design and optimization

Firstly, an approach to find two approximate poles for capturing the system behaviour of interconnect network is presented. Secondly, two parameters, the damping ratio and natural undamped frequency, are expressed as functions of the two poles. These two parameters are used to define an objective function and constraints, which form a constrained multivariable nonlinear optimization problem. The optimization problem is solved using a gradient projection method. One major advantage of our approach is the ability to explicitly control the maximum overshoots at the observation points.     

RF-MEMS switch design optimization for long-term reliability

This contribution presents an optimization strategy for the mechanical and geometrical characteristics of clamped–clamped dielectric-less RF-MEMS switches in order to enhance their reliability performances both in terms of switch properties control and long-term actuation behavior. The modifications mainly affect the switch membrane, which is made more robust, and the stopping pillar dimensions, while the switch dimensions are practically unaffected. In the case of the proposed ohmic switch, also the mobile contact region was redesigned in order to increase the contact force. Experimental measurements have demonstrated that the optimized version of the capacitive switch investigated shows an improved resistance to high bias voltages (up to 90 V), while the optimized ohmic switch shows a lower, more stable and more reproducible contact resistance. Long-term actuation measurements are analyzed in detail, proposing a model to evaluate the switch lifetime, which was found of the order of few years in the more conservative estimate in the case of capacitive switches. The lifetime estimates are less precise in the case of ohmic switches, mainly because the contact instability sums up with the charging contribution. In spite of the improved switch general properties, lifetime is however not increased with optimization. The most likely explanation is that the optimization strategy was aimed at reducing charge injection and charge non-uniformity, but other effects can be important in lifetime determination.     

一种光环行器优化设计方法

针对光纤通信系统中最常用的晶体型三端口光环形器,详细论述了器件的工作原理,分析了现有方案中存在的光路不对称问题,提出了一种优化设计方法,通过引入位移型的Wollaston棱镜和改进型的位移晶体,设计出一种光路完全对称的器件结构,提高了光路调试和器件封装的效率.     

期待的是可执行性的标准

文章概要地说明，制定‘标准’应该具有先进性、科学性和可执行性，其核心是可执行性的问题。     

A new optimization technique for adaptive antenna arrays

An adaptive nulling algorithm for adjusting the array weights under the soft constraint of the weight norm being very much less than 1 or equal to 1, based on the measured correlations between the array and element outputs, is described. The algorithm can be regarded as an extension of the constrained least-mean-square algorithm. It is derived from the same concept of signal and noise subspaces defined in the multiple signal classification (MUSIC) algorithm. One of the unique features of the present algorithm is that the number of the iterations required to adapt the array weights to form nulls is exactly equal to the number of interferers