Roundoff noise prediction in short-wordlength fixed-point digital filters
Andrew J. McWilliam, B.J. Stanier · IEE Journal on Electronic Circuits and Systems · 1978
Consideration is given to recursive fixed-point digital filters employing a signal wordlength in the range of 4 to 8 bits. Experimentally determined values of roundoff-noise variance are found to deviate markedly from those predicted in the normal manner. Such deviation is caused mainly by correlations between signal and error sequences. A method is proposed whereby improved predictions of noise variance may be obtained in the case of first order filters. Finally, it is demonstrated that, when the ‘coefficient slicing’ realisation is used to realise filters with sufficiently quantised coefficients, such filters yield both a very low level of roundoff noise, and also excellent agreement between the predictions of a simple model and measured noise levels