Hindawi Publishing Corporation Te Scientifc World Journal Volume 2013, Article ID 320489, 16 pages http://dx.doi.org/10.1155/2013/320489 Research Article Efficient and Accurate Optimal Linear Phase FIR Filter Design Using Opposition-Based Harmony Search Algorithm S. K. Saha, 1 R. Dutta, 2 R. Choudhury, 2 R. Kar, 1 D. Mandal, 1 and S. P. Ghoshal 3 1 Department of ECE, NIT Durgapur, Durgapur 713209, India 2 Department of ECE, BCET, Durgapur, India 3 Department of EE, NIT Durgapur, Durgapur 713209, India Correspondence should be addressed to D. Mandal; durbadal.bittu@gmail.com Received 11 March 2013; Accepted 29 April 2013 Academic Editors: C. Grimm and D. A. Zeze Copyright © 2013 S. K. Saha et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In this paper, opposition-based harmony search has been applied for the optimal design of linear phase FIR flters. RGA, PSO, and DE have also been adopted for the sake of comparison. Te original harmony search algorithm is chosen as the parent one, and opposition-based approach is applied. During the initialization, randomly generated population of solutions is chosen, opposite solutions are also considered, and the ftter one is selected as a priori guess. In harmony memory, each such solution passes through memory consideration rule, pitch adjustment rule, and then opposition-based reinitialization generation jumping, which gives the optimum result corresponding to the least error ftness in multidimensional search space of FIR flter design. Incorporation of diferent control parameters in the basic HS algorithm results in the balancing of exploration and exploitation of search space. Low pass, high pass, band pass, and band stop FIR flters are designed with the proposed OHS and other aforementioned algorithms individually for comparative optimization performance. A comparison of simulation results reveals the optimization efcacy of the OHS over the other optimization techniques for the solution of the multimodal, nondiferentiable, nonlinear, and constrained FIR flter design problems. 1. Introduction Digital flter is essentially a system or network that improves the quality of a signal and/or extracts information from signals or separates two or more signals which are previ- ously combined. Te linear time invariant (L TI) system and the flter are synonymous and are ofen used to perform spectral shaping or frequency selective fltering. Te nature of this fltering action is determined by the frequency response characteristics, which depend on the choice of system parameters, that is, the coefcients of the diference equations. Tus, by proper selection of the coefcients, one can design frequency selective flters that pass signals with frequency components in some bands while attenuate signals containing frequency components in other frequency bands [1, 2]. Tere are diferent techniques for the design of FIR flters, such as window method and frequency sampling method. All these methods are based on approximation to the frequency characteristics of ideal flters. Te design method is based on the requirements of ripples in the passband and the stopband, the stop band attenuation and the transition width. In the window method, ideal impulse response is multiplied with a window function. Tere are various kinds of window functions (Butterworth, Chebshev, Kaiser, etc.). Tese windows limit the infnite length impulse response of ideal flter into a fnite window to design an actual response [3–5]. But the major drawback of windowing methods is that it does not allow sufcient control of the frequency response in the various frequency bands and other flter parameters such as transition width, and it tends to process relatively long flter lengths. Te designer always has to compromise on one or other design specifcations [6]. Te conventional gradient-based optimization method [7] and other classical optimization algorithms [3, 4] are not sufcient to optimize multimodal and nonuniform objective functions of FIR flters, and the objective function cannot converge to the global minimum solution. So, evolutionary methods have been implemented in the design of optimal digital flters