Recursive Hartley filter-a new efficient digital-prefilter structure

Generation of various prefiltering characteristics from the recursive Hartley filter (RHF) is introduced. The RHF can be regarded as a new family of digital-prefilter structures and is the only prefilter proposed to have the ability to design the lowpass, bandpass and highpass digital filters simultaneously. These prefilters can be combined with appropriately designed equalisers based on equiripple methods, leading to efficient FIR digital-filter designs. In the bandpass design, the RHF is further modified to have a linear phase property and a more efficient hardware structure. The characteristics of the RHF and modified RHF are discussed in detail and those applied to the prefilter-equaliser approach are demonstrated in several design examples. Compared with the conventional equiripple design the proposed RHF and modified RHF can provide significant savings in the number of multipliers and adders at the expense of slightly larger filter length (delays)