Tricks for Cascading Running-Sum Filters With Their Variations for High-Performance Filtering [Tips & Tricks]

High-performance filtering (a flat passband, a sharp transition band, and a highly suppressed stopband) is always the ultimate goal of any digital signal processing (DSP) practitioner. However, high-performance filtering is traditionally the synonym of high implementation complexity. In this article, we propose an approach to reach high-performance filtering with lower implementation complexity. This approach designs a composite low-pass filter (LPF) by cascading a number of simple filters of diverse magnitude responses. In particular, this composite filter consists of prototype infinite impulse response (IIR) filters together with a mixture of shaping running-sum filters and their variations. These component shaping filters contain no multiplier at all. The numeric example shows that the filtering performance of our composite filter outperforms that of the conventional IIR filters (e.g., Chebyshev type 1 and elliptic filters) of higher complexity.