A digital filter structure with constant output roundoff noise level independent of filter bandwidth

It is shown that the roundoff noise level of an all-pass filter realized in normalized lattice structure is approximately equal to a constant value that depends only on the filter´s order for both fixed and floating point arithmetics. As a consequence, the parallel all-pass realization of a digital filter employing normalized lattice all-pass sections is shown to produce very low roundoff noise at the output which is practically independent of filter bandwidth. This result is valid for all classical types of filters, including low-pass, high-pass, and bandpass filters