An efficient approach for designing FIR low-pass filter and its application

In this paper, an adjustable window function, based on combination of tangent hyperbolic function and a weighted cosine series, is proposed to design an FIR filter. The proposed window has only one adjustable parameter “r”. By varying this parameter, it is possible to change the spectral characteristics of the filter. The performance of the proposed window is compared with Gaussian and Kaiser windows. The proposed window has slightly larger main-lobe width compare to the commonly used Gaussian and Kaiser windows, while featuring 19.71 dB and 8.29 dB smaller ripple ratios respectively. Moreover the side-lobe roll-off ratio of the proposed window is almost 115.03 dB and 14.95 dB better than the Gaussian and Kaiser windows respectively. Simulation results show that the filter designed by the proposed window yields 34.39 dB smaller ripple ratio than Kaiser window. Further, the low-pass filter, designed by the proposed method results 7.3766 times and 3.65 times better side-lobe roll-off ratios than those of Gaussian and Kaiser windows respectively. This paper also highlights an application of the proposed method in the area of eliminating noise from corrupted Audio signal.