Sharpening of comb filter by multiple use of the same filter

The paper presents an extension of the method proposed by A. Kwentus et al. (see IEEE Trans. Sig. Process., vol.45, no.2, p 457467, 1997) for sharpening comb filters. The method is based on the use of an amplitude change function (ACF) to decrease passband droop and increase alias rejection in the comb filter. Our proposal is to use a set of ACFs in order to obtain more flexibility in comb filter performance.