ALLPASS-BASED DUAL-NOTCH FILTER WITH CLOSELY SPACED NOTCH FREQUENCIES

Petar  Stančić; Goran Stančić; Ivana Đorđević; Stevica Cvetković

doi:10.20544/hisj.2026.595

Authors

Petar Stančić University of Niš, Faculty of Electronic Engineering - Niš, Serbia
Goran Stančić University of Niš, Faculty of Electronic Engineering - Niš, Serbia
Ivana Đorđević University of Niš, Faculty of Electronic Engineering - Niš, Serbia
Stevica Cvetković University of Niš, Faculty of Electronic Engineering - Niš, Serbia

DOI:

https://doi.org/10.20544/hisj.2026.595

Keywords:

Notch Filters, Parallel Connection, Approximately Linear Phase, All-Pass Filters, Equiripple Phase Error, Equiripple Magnitude Error

Abstract

In this paper, the method for designing a digital filter with two closely spaced notch frequencies is presented. The filter is implemented using two all-pass filters connected in parallel. To achieve an approximately linear phase, one of the all-pass filters is a pure delay. The proposed configuration, consisting of two IIR all-pass filters, can provide two notch frequencies and a flexible phase response. Unlike a filter of the same configuration with a piecewise-constant phase, where the filter order is 4 to realize two notch frequencies, the described approach for designing an approximately linear-phase filter allows increasing the filter order to reduce the approximation error.

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