Leszek J. Opalski

Design for nonsymmetrical statistical distributions

This paper presents a method for approximation of the constraint region and design centering for statistically distributed design parameters. Arbitrary uncorrelated probability density functions (p.d.f.s) are considered, including truncated ones. The approximation problem is formulated deterministically and solved by optimization. The constraint region is approximated by a family of second-order ellipsoidal type functions. Formulation of the approximation problem takes into account statistical distributions of parameters, to be used in subsequent design centering. A special metric replaces evaluation of a multidimensional (yield) integral over the constraint region by simple integrals over fixed intervals. An additional outcome of the approximation process is location of a nominal design that increases yield.

Design centering using an approximation to the constraint region

The paper discusses the applicability of the piecewise-ellipsoidal approximation (PEA) to the acceptability region for solution of various design problems. The PEA technique, originally developed and tested for linear discrete circuits described in the frequency domain, is briefly reviewed. It is shown that PEA is a generic mathematical method and its applicability is extended to linear and nonlinear systems (not necessary electrical) described in time or frequency domains. The architecture of a software implementing the technique is introduced and approximations to the acceptability regions for the given design specifications for integrated circuits (CMOS amplifier, clock driver) and multidomain systems (servomechanism) are constructed and their accuracy checked. Then, some standard optimal-design algorithms (i.e., worst case parametric yield maximization, yield versus cost optimization) are redesigned to exploit the PEA properties (e.g., local convexity/concavity) and make them more effective. The algorithms are confronted with design problems, and quality of the resulting designs is assessed.

Accuracy and Bandwidth Optimization of the Over-Determined Offset-Short Reflectometer Calibration

We present a new method for calculating line lengths of offset-short standards so as to provide a broadband and accurate one-port vector-network-analyzer (VNA) calibration. Our method is based on an approximate uncertainty analysis of corrected VNA measurements. We estimate the maximum value of the total variance (i.e., the trace of the covariance matrix) of errors in those measurements at a single frequency, and then quantify the quality of the offset-short calibration in a given frequency range with two metrics: the upper bound for the total variance and the lower calibration frequency. We then apply a global bi-objective optimization to these metrics in order to determine the optimal lengths. In order to verify our approach we first validate assumptions made in the approximate uncertainty analysis through a Monte Carlo simulation. We further perform an experiment in which we compare measurements of verification devices after calibrating the VNA with different offset-short sets designed with our method and with a set of reference airlines. Finally, we perform an uncertainty analysis for these measurements, which demonstrates the tradeoff between the offset-short calibration bandwidth and accuracy, and shows that our approach for selecting the offset-short line lengths provides the broadest bandwidth for a given calibration accuracy.

Application of the piecewise ellipsoidal approximation technique to design centering

A new worst case design algorithm for box-type tolerance region is presented. It employs specific properties of the piecewise ellipsoidal approximation of the acceptability region. The two-level optimizer uses a 2-phase feasible directions algorithm at the upper level and a combination of a projected gradient technique and a special purpose global optimization algorithm at the lower level. Optimization results on some standard problems illustrate concepts and efficiency.<<ETX>>

Variability-based global sensitivity analysis of circuit response

The research problem of interest to this paper is: how to determine efficiently and objectively the most and the least influential parameters of a multimodule electronic system - given the system model f and the module parameter variation ranges. The author investigates if existing generic global sensitivity methods are applicable for electronic circuit design, even if they were developed (and successfully applied) in quite distant engineering areas. A photodiode detector analog front-end system response time is used to reveal capability of the selected global sensitivity approaches under study.

An empirical study of transient responses of potentiometric ion sensors

The paper presents selected results of an empirical study of transient responses of ion-selective potentiometric sensor to two classes of stimulus. First, voltage time-domain response of ion-selective structures was observed to changes of ion concentrations in the sample, flow speed and electric load of the sensor. Presented results explain essential accuracy/precision limitations of ion concentration estimates that can be obtained in practical applications for clean water. Second, current time sensor response to small voltage stimulus was observed for different ionic content of the sample. A behavioral model was built, that can be used (along traditional steady-state model) for Data Fusion-based enhancement of multiple-sensor measurements.

Prototype of analog feedback communication system: First results of experimental study

The paper presents first results of an experimental study of narrow band optimal analog adaptive feedback communication system (AFCS) designed for analog signals transmission. The prototype system implemented optimal transmission — reception algorithm derived and studied in [1]-[4] and other authors works. The aim of the study was a comparison of theoretically expected performance of the system (limit accuracy, power and bandwidth efficiency of transmission) and performance provided by its hardware implementation.

A broadband test fixture for characterizing circuits mounted inside TO-8 package

We present a novel design of two-port test fixture for characterizing infrared (IR) detectors in TO-8 packages with a vector network analyzer (VNA). We characterize the system with a two-tier calibration technique. Ten unknown scattering parameters of our reciprocal fixture are calculated from the second-tier over-determined calibration performed using a special set of tiny short-open-load-thru calibration standards. These standards, built in house on the TO-8 header, were analyzed with an electromagnetic field simulating tool and their characteristics are utilized in the calibration. Having the fixture parameters, we de-embed characteristics of tested IR detectors. Experiments validate high consistency of the de-embedded characteristics for both the standards and test detectors measured up to 3 GHz. This new fixture and de-embedding technique can be easily adapted to characterize broadband circuits mounted in other types of TO packages.

Data processing for multi-sensor in-situ measurements: EU FP6 WARMER project perspective

The paper starts from a brief introduction to the EU FP6 WARMER (Water Risk Management in EuRope) project, but the main body is a presentation of current WARMER R&D in data processing for in-situ probes. The paper focuses on software development for local fusion of multi-sensor measurement data collected from WARMER-developed potentiometric sensors.

Electrical properties of potentiometric sensors -an empirical study

The paper sums up investigations of electrical properties of potentiometric sensors that are under development in the EU FP6 WARMER project. There are 2 main goals of the empirical study: to determine minimum input resistance/bias current of data acquisition board and to determine the quality of analytical signal in DC and transient responses of the potentiometric sensors.