AbstractThe idea of discrete constrained notch filters is well known and widely described in the literature. Time‐invariant as well as time‐varying filters are considered. Because of the discrete nature of such filters, their application is limited to sampled signals, usually obtained as samples of low‐frequency signals. the aim of this paper is to give some ideas on how to synthesize a time‐varying analogue constrained notch filter which can be used directly for continuous