I. Introduction
With the advantages of digital signal processing (DSP) over an analog system [1], [2], digital filters have attracted increasing attention in recent years due to demands for improved performance in high-data-rate digital communication systems and in wideband image/video processing systems. Digital infinite-impulse-response (IIR) filters can often provide a much better performance and less computational cost than their equivalent finite-impulse-response (FIR) filters [3] and have become the target of growing interest [1], [2], [4]. However, because the error surface of IIR filters is usually nonlinear and multimodal, conventional gradient-based design methods may easily get stuck in the local minima of error surface [4], [5]. Therefore, some researchers have attempted to develop design methods based on modern heuristic optimization algorithms such as genetic algorithm (GA) [6]–[9], simulated annealing (SA) [10], tabu search (TS) [5], ant colony optimization (ACO) [1], immune algorithm (IA) [2], differential evolution (DE) [11], [12], and particle swarm optimization (PSO) [13], [14], etc.