Comments on "The structure of the limit cycles in sigma delta modulation

In the above-titled paper by V. Friedman (see ibid., vol.36, p.972-9, Aug. 1988), noise spectra of single-loop sigma-delta modulators are calculated for DC inputs which are rational fractions of the quantizing steps. The commenter points out that, by using a simple combination of the previously published results, more explicit results are arrived at much more easily.<>