Noise power estimation for poly-phase decimation filters: a frequency domain approach

This paper presents an algorithm used to calculate the total noise power for a specific decimation filter structure using a frequency domain approach. The assumed structure of the decimation filter is a cascade of double lowpass 2-path poly-phase blocks as presented by Kale, Morling and Krukowski (see IEE International Conference, ADDA ´94, Cambridge, 6-8 July, 1994). To establish the validity of the frequency domain approach the algorithm has been incorporated into a program which determines the internal data-path widths required for a given output precision. Verification of the algorithm is then possible by performing fixed-point time domain simulations using the data-path widths suggested and estimating the total output noise power, Results of the noise power estimation algorithm and data-path width determination algorithm for a 7 stage decimation filter are reported