146 research outputs found
NASA Space Engineering Research Center for VLSI System Design
This annual report outlines the activities of the past year at the NASA SERC on VLSI Design. Highlights for this year include the following: a significant breakthrough was achieved in utilizing commercial IC foundries for producing flight electronics; the first two flight qualified chips were designed, fabricated, and tested and are now being delivered into NASA flight systems; and a new technology transfer mechanism has been established to transfer VLSI advances into NASA and commercial systems
Addressing Computational Complexity of High Speed Distributed Circuits Using Model Order Reduction
Advanced in the fabrication technology of integrated circuits (ICs) over the last couple of years has resulted in an unparalleled expansion of the functionality of microelectronic systems. Today’s ICs feature complex deep-submicron mixed-signal designs and have found numerous applications in industry due to their lower manufacturing costs and higher performance levels. The tendency towards smaller feature sizes and increasing clock rates is placing higher demands on signal integrity design by highlighting previously negligible interconnect effects such as distortion, reflection, ringing, delay, and crosstalk. These effects if not predicted in the early stages of the design cycle can severely degrade circuit performance and reliability.
The objective of this thesis is to develop new model order reduction (MOR) techniques to minimize the computational complexity of non-linear circuits and electronic systems that have delay elements. MOR techniques provide a mechanism to generate reduced order models from the detailed description of the original modified nodal analysis (MNA) formulation.
The following contributions are made in this thesis:
1. The first project presents a methodology for reduction of Partial Element Equivalent Circuit (PEEC) models. PEEC method is widely used in electromagnetic compatibility and signal integrity problems in both the time and frequency domains. The PEEC model with retardation has been applied to 3-D analysis but often result in large and dense matrices, which are computationally expensive to solve. In this thesis, a new moment matching technique based on Multi-order Arnoldi is described to model PEEC networks with retardation.
2. The second project deals with developing an efficient model order reduction algorithm for simulating large interconnect networks with nonlinear elements. The proposed methodology is based on a multidimensional subspace method and uses constraint equations to link the nonlinear elements and biasing sources to the reduced order model. This approach significantly improves the simulation time of distributed nonlinear systems, since additional ports are not required to link the nonlinear elements to the reduced order model, yielding appreciable savings in the size of the reduced order model and computational time.
3. A parameterized reduction technique for nonlinear systems is presented. The proposed method uses multidimensional subspace and variational analysis to capture the variances of design parameters and approximates the weakly nonlinear functions as a Taylor series. An SVD approach is presented to address the efficiency of reduced order model. The proposed methodology significantly improves the simulation time of weakly nonlinear systems since the size of the reduced system is smaller than the original system and a new reduced model is not required each time a design parameter is changed
Analysis and Life Cycle Assessment of Printed Antennas for Sustainable Wireless Systems
Siirretty Doriast
Sustainable international experience: A collaborative teaching project
Within engineering education, there is an increasing need for providing our students with international experiences. This is most often done by exchange studies abroad. However, a majority of the students on engineering programs do not engage in any international exchange. This paper presents insights from a collaborative cross-disciplinary international project to give students international experience without having to travel. From both a sustainability perspective and a situation where e.g. a global virus outbreak stop students from travelling, solutions that give engineering students experience of working in an international setting are becoming increasingly important. Initial challenges, for the teachers involved in the project, that were addressed before the project started, included the assessment of students, the use of online collaborative tools, assessment of students and the dependence between the two courses. The learnings from the first and second iteration of the collaborative project were mainly focused around transparency, introduction of students to each other, communication, real-time issues and deadlines. By gradually remove these peripheral challenges for the students, resulting in making the students focus on the actual challenges surrounding the actual collaborative project. Even though this project is ongoing, the initial results clearly show that by integrating courses between different countries and disciplines, it is possible to create an environment that strengthens the students’ ability in teamwork, communication and addresses the cultural and professional aspects of working as an engineer in an international context
Direct multidisplay for web document repositories
As the popularity of the Internet grows, the information on the Internet is increasing as well. Search engines are important tools to help people retrieve information of interest from the huge amount of documents. However, currently used search engines return long lists of URLS. Users have to click each URL to download the actual document and check its content and click the back button to access other URLs if the answer is not found in the current URL. This process is both labor intensive and time consuming. Multibrowser, a program that addresses this problem, is presented in this thesis. Multibrowser combines the advantages of multidisplay and direct display to present a more efficient user computer interface. First, the system downloads the actual documents according to the list of URLs returned by a standard search engine and saves the documents on the local disk. Second, the system converts the documents into n-gram vectors and clusters them into three groups according to the n-gram vectors. Then each document is assigned a color according to its position in relation to the cluster centroids. Also, each paragraph is linked with other paragraphs which have similar contents. Last, the documents are presented to the users using Multidisplay, where each document has a corresponding color bar. Users can look through the content of several documents at the same time and see the similarity among them by the colors bars; users can then retrieve the most similar paragraphs to a certain paragraph by clicking its find similar link. In addition, the investigation of hash tables for our text processing shows that the hash table size has to be chosen very carefully to avoid undesirably large collision probability. Some good values are suggested based on our experiments
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