Filter structures for decimation: a comparison

In this paper three different digital filter structures for decimation by a factor of 64 are compared. They are based on a commercially available decimator AD7722 by Analog Devices. The AD 7722 is a complete low power ΣΔ analog-to-digital converter with the application in digital audio processing. The applied filter is a two-stage decimator which decreases the sample rate by 32 and 2 respectively. This structure is then compared to a state-of-the-art approach of a FIR decimator with six stages, each of them performing decimation by a factor of 2, and to two different approaches to an almost linear phase IIR decimator based on an very efficient class of lattice wave digital filters with also six down-samplers. The advantages and disadvantages of the selected structures are described.