Worst-case Parameter Sets Research Articles

Integrity risk evaluation of impact of ionospheric anomalies on GAST D GBAS

This study develops a three-step Monte Carlo method to evaluate the worst possible integrity risk of ionospheric spatial gradients for GAST D GBAS. Impact simulation parameters are classified into two groups, “worst-case” and “average,” based on the underlying integrity requirements. Unlike “average” parameters, “worst-case” parameters are those for which a clear basis for averaging could not be established because the probabilistic distribution of these parameters cannot be developed with sufficient confidence due to the lack of observation data. In calculating integrity risk, these “worst-case” parameters use the worst-case value that maximizes the integrity risk. Each step of the randomized search narrows down the parameter ranges in sequence and identifies the two worst-case parameter sets (based on the largest position error and the largest missed-detection probability) for each worst-case region identified in the initial step. The resulting integrity risk values are well below 10^-9, showing that the GAST D SARPs integrity requirement is met.

Aeronautical channel modeling

A class of aeronautical wide-band channel models is proposed, featuring parking and taxi environments, takeoff and landing situations, and en-route scenarios for ground-air and air-air links. Typical and worst case parameter sets are suggested, based on published measurement results and empirical data. The models are suitable for channel emulators that can be easily implemented on digital computers or in hardware and thus are useful for the validation of digital aeronautical links. A time-domain and frequency-domain implementation of such a channel emulator are derived, and results for a typical multicarrier system are presented. It is shown that the scenarios have distinguishable performance results depending on the underlying maximum ranges and shapes of the Doppler and delay spectra and the presence of a line-of-sight path. Finally, the degrading effects of intersymbol interference and intersubcarrier interference on the multicarrier signal are explained.

Worst case tolerance analysis of linear analog circuits using sensitivity bands

The major difficulty of accurate worst case tolerance analysis is to identify the worst case parameter sets. Traditional vertex analysis presumes the monotonicity between circuit response and circuit parameters, and uses nominal sensitivity information to select the vertices of parameter space as the worst case parameter sets. However, under parameter variations, the sensitivity itself is uncertain within an interval range, furthermore, the worst case parameter sets may not be the vertices of parameter space. In this paper, the relationship among monotonicity, sensitivity, and worst case parameter sets is investigated in the context of parameter variations. An efficient yet accurate approach for linear circuit worst case tolerance analysis is proposed. The underlying idea is that if the circuit response is monotonic with respect to the changes in a specific circuit parameter over the parameter space, then the worst case parameter sets are located at the corners of that parameter. The monotonicity is identified by the sensitivity band computation, and is used to generate uncertainty-reduced simulation problems. Experimental results strongly meet the expectation for accuracy and efficiency.

Expression of worst case using multivariate analysis in MOSFET model parameters

Device and circuit performance such as drain current and delay time varies stochastically due to uncontrollable factors in the fabrication processes. In this paper, a new method that represents the variation of the performance as worst case parameters in a MOSFET model is proposed. The variation of the performance can be expressed as a linear combination of several process-related parameters of the MOSFET model. Because of this fact, the worst case of parameters which corresponds to the worst case of performance can be directly and uniformly determined. Therefore, the calculation time of worst case parameters can be reduced by this method. The worst case parameter sets calculated by this method enable designers to estimate circuit performance variations accurately and easily. The capability of this method is verified in the variation analysis of drain current.

PRACTICAL METHODS FOR WORST-CASE AND YIELD ANALYSIS OF ANALOG INTEGRATED CIRCUITS

Worst-case analysis is commonly used in integrated circuit design to verify a satisfactory circuit performance with regard to changes in the manufacturing conditions. However, worst-case analysis is often carried out using approximate worst-case parameter sets. This paper presents a new approach to the worst-case design of integrated circuits that takes account of fluctuations in the operating conditions. It provides exact and unique worst-case manufacturing conditions and worst-case operating conditions for given circuit specifications. These specifications may be either performance limits or minimum yield requirements. The method is illustrated with the parametric design of integrated CMOS bias stages.