Publica
Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. Nonlinear function generation using oversampled SigmaDelta modulators
 IEEE Circuits and Systems Society: The 2000 IEEE International Symposium on Circuits and Systems, ISCAS 2000. Vol.1 : May 28  31, 2000, Geneva, Switzerland Piscataway, NJ, United States: IEEE, 2000 ISBN: 0780354826 pp.I611I614 
 International Symposium on Circuits and Systems (ISCAS) <33, 2000, Geneva> 

 English 
 Conference Paper 
 Fraunhofer IMS () 
Abstract
In this paper we present a technique for nonlinear function generation which uses a novel sparse lookup table approach. This novel approach can be derived from the simple lookup table concept and utilizes the interpolating properties of oversampled SigmaDelta modulators. We show that the approximation process with oversampled SigmaDelta modulators can be generally understood as a weighted sum of piecewisecontinuous polynomial Bsplines. The weights are digitally stored in a sparse lookup table memory which can be used for the nonlinear function mapping. The shape of the polynomial Bsplines depends on the order of the loopfilter which is used in the SigmaDelta modulator topology. Detailed investigations of approximation behaviour show that a spectrum of linear, square, and cubic piecewisecontinuous interpolation can be achieved if we use up to 3rd orderSigmaDelta modulators. With the increased order of modulator topology the approximation quality is also improved under the assumption that we use the same weight set for function mapping. The fact that polynomial Bsplines delivers only nonzero values within a limited range of input arguments makes this approximation method much less sensitive to local errors than classical approximation methods like Lagrange or Newton interpolation.