Int. J. Signal and Imaging Systems Engineering, Vol. 9, No. 6, 2016 357 Copyright © 2016 Inderscience Enterprises Ltd. Passive congregation-based particle swarm optimisation for designing quadrature mirror filter bank Supriya Dhabal* Department of Electronics & Communication Engineering, Netaji Subhash Engineering College, Kolkata 700152, West Bengal, India Email: supriya_dhabal@yahoo.co.in *Corresponding author Palaniandavar Venkateswaran Department of Electronics & Tele-Communication Engineering, Jadavpur University, Kolkata 700032, West Bengal, India Email: pvwn@ieee.org Abstract: In this paper, we propose two different approaches based on Particle Swarm Optimisation (PSO) for the design of Near Perfect Reconstruction (NPR) Quadrature Mirror Filter (QMF) bank. The proposed method employs Constriction Factor-based PSO (CPSO) and PSO with Passive Congregation (PSOPC) approach for the design of prototype filter. Both the PSO methods are presented to optimise FIR filter coefficients that lead to NPR filter bank. Passband ripple, stopband energy, transition-band error and amplitude distortion of the overall bank are combined to obtain a closed form objective function. Two illustrative examples are given to demonstrate the feasibility of our proposed scheme and performances are compared with other existing methods. The experimental results show that PSOPC algorithm provides better performance parameters with great accuracy and convergence. Keywords: QMF; quadrature mirror filter; NPR; near perfect reconstruction; PSO; particle swarm optimisation; CPSO; PSOPC; PRE; peak reconstruction error. Reference to this paper should be made as follows: Dhabal, S. and Venkateswaran, P. (2016) ‘Passive congregation-based particle swarm optimisation for designing quadrature mirror filter bank’, Int. J. Signal and Imaging Systems Engineering, Vol. 9, No. 6, pp.357–368. Biographical notes: Supriya Dhabal received the BTech degree in Electronics and Communication Engineering from Kalyani Government Engineering College, Kolkata, West Bengal, India, in 2006, and ME degree in Electronics and Tele-Communication Engineering from Jadavpur University, Kolkata, West Bengal, India, in 2008. In 2008, he joined Tata Consultancy Services, Kolkata, as an Assistant System Engineer and in 2009, he joined Netaji Subhash Engineering College, Kolkata, as an Assistant Professor. His research interests include efficient design of digital filters and applications of digital filter in several fields of signal processing and communications. Palaniandavar Venkateswaran has been working as an Associate Professor in the Department of Electronics & Tele-Communication Engineering (ETCE), Jadavpur University (JU), Kolkata, India, since October 2001, he was promoted as a Professor in 2009. He has published over 70 papers in various national/international, journal/conference proceedings. His fields of interest are computer communication, microcomputer systems and digital signal processing. He is a senior member of IEEE (USA). 1 Introduction An essential system used in multi-rate signal processing is the Quadrature Mirror Filter (QMF) bank. Since it was introduced in 1977, the investigation on efficient design of QMF bank has become an important research area. A superior design of QMF bank can have significant effect on numerous applications such as sub-band coding, signal de- noising, image compression, and also in adaptive signal processing. For the first time, Esteban and Galand (1977) used QMF bank for speech signal processing to reduce aliasing distortion. In 1980, Johnston stated an objective