Efficient Implementation of Complex Modulated Filter Banks Using Cosine and Sine Modulated Filter Banks

<p/> <p>The recently introduced exponentially modulated filter bank (EMFB) is a <inline-formula><graphic file="1687-6180-2006-058564-i1.gif"/></inline-formula>-channel uniform, orthogonal, critically sampled, and frequency-selective complex modulated filter bank that satisfies the perfect reconstruction (PR) property if the prototype filter of an <inline-formula><graphic file="1687-6180-2006-058564-i2.gif"/></inline-formula>-channel PR cosine modulated filter bank (CMFB) is used. The purpose of this paper is to present various implementation structures for the EMFBs in a unified framework. The key idea is to use cosine and sine modulated filter banks as building blocks and, therefore, polyphase, lattice, and extended lapped transform (ELT) type of implementation solutions are studied. The ELT-based EMFBs are observed to be very competitive with the existing modified discrete Fourier transform filter banks (MDFT-FBs) when comparing the number of multiplications/additions and the structural simplicity. In addition, EMFB provides an alternative channel stacking arrangement that could be more natural in certain subband processing applications and data transmission systems.</p

Implementation of linear-phase FIR nearly perfect reconstruction cosine-modulated filterbanks utilizing the coefficient symmetry

The analysis and synthesis parts of a cosine-modulated -channel filterbank (FB) contain two sections, a modulation block and a prototype filter implemented in a polyphase structure. Although, in many cases, a linear-phase prototype filter is used, the coefficient symmetry of this filter is not utilized when using the existing polyphase structure. In this paper, a method is proposed for implementing a linear-phase prototype filter building a nearly perfect reconstruction cosine-modulated FB in such a way that it enables one to partially utilize the coefficient symmetry, thereby reducing the number of required multiplications in the implementation. The proposed method can be applied for implementing FBs with an arbitrary filter order and number of channels. Moreover, it is shown that, in all cases under consideration, the cosine-modulation part of the FB can be implemented by using a fast discrete cosine transform. The efficiency of the proposed implementation is evaluated by means of examples.Published versio