An Optimized Near Perfect Reconstruction Transmultiplexer

The design of an optimized near-perfect reconstruction (NPR) type trans-multiplexer has been proposed. Cosine modulation has been used to design the synthesis and analysis sections of the trans-multiplexer. The design of transmultiplexer was reduced to design of single low-pass prototype FIR filter which is designed using variable window function (Kaiser, Cosh and DolphChebyshev). An unconstrained, non-linear, iterative optimization technique Levenberg-Marquardt (LM) has been applied for optimization of filter coefficients such that the prototype filter have minimum value of error in its pass band, transition band and stop band. This results in minimum value of interference parameter like inter-channel interference (ICI) and inter-symbol interference (ISI) that occurs due to interference of filters in their stop-band and non-ideal nature of filters in their pass-band respectively. When compared to the optimized prototype filter designed without using any window function, the proposed method gives better performance in terms of reduction in errors in pass band, transition band and stop band and interference parameters (ICI and ISI) for same filter specification. KeywordsKaiser, Cosh, Dolph-Chebyshev window, Filterbanks, Cosine Modulation, ICI, ISI, LM Optimization.