Design of variable comb filter using FIR variable fractional delay element

In this paper, a new approach is proposed for the design of infinite-impulse-response (IIR) comb filter. The problem of the comb filter design is transformed into that of fractional delay filter design. Using the proposed method, the multiplier inside the proposed structure can be fixed regardless the value of fundamental frequency of harmonic interferences. This improvement makes the proposed structure be possible for the design of variable cases. To realize variable comb (VC) filter, the variable fractional-delay (VFD) filter is designed in weighted least-squares (WLS) sense first. Then, by embedding the designed VFD filter with a switch, the variable comb filter could be implemented in a proposed structure. Several experimental results and examples are presented to demonstrate the effectiveness of the proposed method.

► A new transfer function is introduced for the design of IIR fixed comb filter.
► Comb filter design can be transformed into the fractional delay filter design.
► VFD element is well designed in WLS approach to make the comb filter be variable.
► Unified structure is proposed to implement the variable comb filter.