Design of new FIR digital filters by using hybrid window functions

In this thesis study, new hybrid window functions are presented for the design of windowing method based design of FIR digital filters. These proposed new windows are obtained by combining the Cosh window having two-parameters with different windows having one-parameter in the literature. First of all, window spectral performance analysis of fixed and proposed windows are performed in terms of ten window spectral parameters. Then, analysis of the proposed windows in terms of the ripple ratio and mainobe width, which are the window spectral parameters related with filter design, are performed. The simulation results with a window length of N = 51 and fixed mainlobe width show that four Cosh based hybrid windows can present better ripple ratio than both Kaiser and Cosh windows. As for the simulation results with a window length of N = 51 and different mainlobe widths, it is shown that five hybrid windows can present better ripple ratio than Cosh window. Finlly, the performance of the proposed hybrid windows in the filter design is investigated comparatively. The simulation results performed for a filter length of N = 51 and different filter transition widths show that six hybrid windows can provide better filter characteristics than Cosh window. Moreover, for filter lengths of N = 51 and 101, the filters designed by the proposed windows are compared with the filters designed by two-parameter windows in literature in terms of the minimum stopband attenuation for fixed transition width. Results show that Cosh-Hamming and Cosh-Von Hann windows can provide better filters than other windows.