Reliability Study of Combinational Circuits

An exact, practical implementation of reliability calculation for combinational circuits can be based on a hierarchical decomposition of the circuit into manageable sub--units, and construction of exact summary tables for each sub--unit. For a simple example of voting logic, this exact reliability analysis reaffirms that the reliability of the individual voter inputs is as important as the voter reliability. 1 Introduction Reliability analysis of a circuit estimates the likelihood that a whole system operates correctly after a given period of time. An attractive technique of improving this reliability is through the use of hardware redundancy which ensures that correct outputs are produced even when some faults are present in the circuit structure. In these circumstances, redundancy masks faults so that many different fault combinations are not visible at the circuit's outputs. To obtain a precise estimate of the reliability of circuits, it is desirable to model circuits at the transi..

Fault Tolerant, Radiation Hard, High Performance Digital Signal Processor

An architecture has been developed for a high performance VLSI digital signal processor that is highly reliable, fault tolerant and radiation hard. The signal processor, part of a spacecraft receiver designed to support uplink radio science experiments at the outer planets, organizes the connections between redundant arithmetic resources, register files and memory through a shuffle exchange communication network. The configuration of the network and the state of the processor resources are all under microprogram control which both maps the resources according to algorithmic needs and reconfigures the processing should a failure occur. In addition, the microprogram is reloadable through the uplink to accommodate changes in the science objectives throughout the course of the mission. The processor will be implemented with silicon compiler tools and its design will be verified through silicon compilation simulation at all levels from the resources to full functionality. By blending reconf..

Whistler Observations on DEMETER Compared with Full Electromagnetic Wave Simulations Sferic Earth Ionosphere (~60 km – 80 km) 0 + Whistler Lightning

International audienceTerrestrial Very Low Frequency (VLF) electromagnetic radiation, which strongly impacts the Van Allen radiation belt electron dynamics, is injected across the ionosphere into the Earth's plasmasphere from two primary sources: man-made VLF transmitters and lightning discharges. Numerical models of trans-ionospheric propagation of such waves remain unvalidated, and early models may have overestimated the absorption, hindering a comprehensive understanding of the global impact of VLF waves in the loss of radiation belt electrons. In an attempt to remedy the problem of a lack of accurate trans-ionospheric propagation models, we have used a full electromagnetic wave method (FWM) numerical code to simulate the propagation of lightning-generated whistlers into the magnetosphere and compared the results with whistlers observed on the DEMETER satellite and paired with lightning stroke data from the National Lightning Detection Network (NLDN). We have identified over 20,000 whistlers occuring in 14 different passes of DEMETER over the central United States during the summer of 2009, and 14,000 of those occured within the 2000 km x 2000 km simulation grid we used. As shown in the attached figure, which shows a histogram of the ratio of the simulated whistler energy to the measured whistler energy for the 14,000 whistlers we compared, the simulation tends to slightly underestimate the total whistler energy injected by about 5 dB. However, the simulation underestimates the DEMETER measurements more as one gets further from the source lightning stroke, so since the signal to noise ratio of more distant whistlers will be smaller, possibly additive noise in the DEMETER measurements (which of course is not accounted for in the model) may explain some of the observed discrepancy