Design of FIR Hilbert Transformers Using a Combined Frequency Response Masking/Frequency Transformation Approach

A method to design low-complexity FIR Hilbert transformers with narrow transition bands and small ripples is presented in this paper. The proposal is based on a strategic combination of the Frequency-Response Masking (FRM) and Frequency Transformation (FT) techniques. The FT technique is employed to divide the overall filter in several identical simple subfilters, whereas the FRM technique is employed to design every subfilter reducing further the complexity of the overall filter. By applying simple rounding to the subfilter coefficients, the overall design achieves a very low number of multiplications per output sample. Design examples show that the proposed method has a lower computational complexity than other existing methods.