Structure-variant transformation for reducing the roundoff noise in block parallel digital filters
Markus Gaida, M. Koeberle, Ernst H. Lueder · 2002
Linear matrix transformation is applied to flow graph matrices of block digital filters to improve roundoff noise behaviour and to enhance the dynamic range. This is done in two main steps: First a structure-variant transformation is performed, i.e. the topology of the filter is changed, so that the input nodes become pure branching nodes and the output nodes become pure adding nodes. Besides that, the scaling multipliers can be abolished through this step. In the second step a structure-invariant transformation is applied which does not change the topology any more but changes the multiplier values to perform a further noise reduction. As an example a second order block digital filter with two inputs and two outputs is used, for which the roundoff noise could be improved from about 39 dB to 21 dB. At the same time the dynamic range at the outputs was enhanced by about 18 dB.>