Improvised method for analysis and synthesis of NUFB for Speech and ECG signal applications

This article presents a rapidly converging optimization technique using a single parameter for designing non-uniform cosine modulated filter banks (CMFB_S). The non-uniform cosine modulated filter banks are derived from closed-form uniform cosine modulated filter banks by merging the relevant bandpass filters based on given decimation factors. In this proposed method, the cut-off frequency of the prototype filter is varied through analytically calculated step size using control parameters so that the filter coefficients at quadrature frequency are approximately equal to 0.707 and the formulated objective function is satisfied with the prescribed tolerance. Simulation results demonstrate that the proposed algorithm achieves superior performance, with amplitude distortion levels significantly outperforming existing methods in the literature, reaching as low as 2.4483 × 10⁻⁴. For the prototype filter design, a constrained equiripple finite impulse response (FIR) digital filter is employed, with the roll-off factor and error ratio chosen based on a stopband attenuation, a passband attenuation and a filter order. The results highlight the proposed algorithm’s effectiveness for high-quality reconstruction of speech signals, particularly in speech coding and enhancement, as well as ECG signals. This makes the method highly versatile and suitable for various practical applications, including sub-band coding of real-time and near real-time signals.